BULGARIAN ACADEMY OF SCIENCES

 

CENTRAL LABORATORY
OF MINERALOGY AND CRYSTALLOGRAPHY

ANNUAL REPORT
No 12/2006

 

Editor: Dr. Nikola Zidarov; E-mail: nzidarov@interbgc.com
© Central Laboratory of Mineralogy and Crystallography, 2007
ISSN 3033-2206

CONTENTS

 

Projects NoNo 4, 24, 29, 30, 31 and 34 are financially supported in part by the Bulgarian National Council for Scientific Investigation of the Ministry of Education and Science. Project No 22 is financially supported in part by EAESME of the Ministry of Economy and Energy. Project No 5 is financially supported in part by the Swiss National Science Foundation.

INTRODUCTION

This annual report presents the activities of the Central Laboratory of Mineralogy and Crystallography during the twelfth year of its existence.

The topics developed were in accordance with the politics and programs for realization of the strategy, aims, and priorities of BAS in the period up to 2007.

The most important scientific achievements, a part of which has been published or reported at scientific events, can be grouped as follows:

The most important scientific and practical achievements are:

The most important results obtained in the framework of the international collaboration of CLMC are:

Scientific activity

During the year the activity was concentrated on 10 projects financed by the budget of the Bulgarian Academy of Sciences, 3 projects additionally financially supported by the National Council for Scientific Investigation, 4 projects in the framework of the international collaboration, and 1 contract with organization in Bulgaria. The scientific results achieved by the staff of CLMC in 2006 were reported in 82 publications in scientific journals and series, 38 of which in international and foreign journals and proceedings, and 44 in Bulgarian issues. The already published papers are 64 in number, whereas those in press are 18. Our colleagues have given 63 reports in international and local conferences and symposiums, with 36 of them being presented on international scientific events or such with an international participation.

Of a national character is the fulfillment of the program "Design and structural analysis of nano-sized regions in functional materials" in the framework of the national program "Nano-technologies and nano-materials". Since the end of 2005, CLMC is taking part, together with Asarel-Medet JSCo and NIPRORUDA JSCo, in the scientific project "Development of technology for combined extraction of gold from copper ore", which is partially financed by the National Agency for Encouraging Small and Medium Enterprises of the Ministry of Economy and Energy.

Users of our scientific products are a number of leading industrial companies like Kaolin JSCo, Sofarma JSCo, Biovet JSCo, Tehcem JSCo, Chelopech mining JSCo, Zlatna Panega Cement JSCo, Geology and Geophysics JSCo, TEPs "Maritsa-East 3" as well as scientific institutes of the Bulgarian Academy of Sciences, Sofia University "St. Kl. Ohridski", etc.

Nikola Zidarov
January, 2007

RESEARCH TOPICS:

I. MINERAL SYSTEMS AND ISOTOPE GEOCHEMISTRY

1. Common regularities during origination, alteration, and interactions of the mineral systems (N. Zidarov)

In geology and mineralogy and in science in general it is already basically accepted that the organization of the system of the natural objects is of fundamental significance. This provokes an understandable willingness to discover the systematic nature and relations during the formation of various geological bodies [63].

In respect to the hierarchical levels of organization of the mineral matter in nature there exist two linear ascending rows, each of them representing an independent system:

Mineral individual mineral aggregate mineral (geologic) body;

Mineral species mineral paragenesis mineral formation (association of mineral parageneses).

The first row corresponds to the term mineral system and includes objects that represent real physical bodies. They are systematic objects because each of them represents a separate relatively independent structural unit (sub-system) with definite composition, inner structure and outer morphology being bounded from the surrounding space with an interrupted closed surface, thus, forming a unit. In this system could be included also the mineral forming media, which bind the processis that lead to the formation of each element in the system (in case when information is available).

The second row corresponds to the term mineralogical system and includes categories of logical notions, which correspond to derivatives from these of first row, i.e. represents a conceptional terminological system, which includes deductive terms and synthesized information obtained by use of analyses like correlation, formational, paragenetic, etc.

These two ascending rows are open upwards and in respect to geological objects various authors specify different subsystems.

Each mineral system, in the sense already postulated above, subjects to the most common regularities of its origination and to the subsequent processes of alteration up to full disintegration of its separate members or their entire destruction.

The processes of interaction of the different genetic types of mineral systems (magmatic, metamorphic, hydrothermal, hydrothermal sedimentary, sedimentary, and hypergenic) through the mineral formation media or during solid state reactions lead to new system relations, respectively to origination of new systems or subsystems.

The application of systematic approach during investigation of varying in genesis and rank model objects [64], correlated with data of other researchers revealed the possibility to mark the following regularities in the origination, transformation, and interactions of the mineral systems:

1. Each geological system (mineral system, respectively), independently of the hierarchical subordination of its elements, is characterized by self organization of its inner state, which tends to reach energetic equilibrium at definite physical-chemical conditions.

2. The change in the outer conditions leads to changes in the system that includes realization of work connected with gain or loss of energy resulting in origination of new system relations between the composing members.

3. The geological systems, spatially closely situated, interact on each level of their organization. This is expressed in gradual transition between them up to fixation of relatively constant alterations, which lead to new status of the system.

4. The speed of the geological processes depends on the rank of the system higher being the rank (i.e. more energy consuming) lower is the speed.

5. The activity of the live systems (including human) in each natural medium is directed against equilibrium up to the moment of its destruction. The subsequent epigenetic processes are directed towards creation of new stable equilibrium under definite physical-chemical conditions.

6. Characteristic feature of each geological system is the presence of heterogeneities at any hierarchical level caused by irregular distributions of the initial inner energy and the different speed of transformations of its elements up to creation of new equilibrium conditions.

7. The conditions determining the initial state of the system are:

8. One condition, determining the energetic state of the system during its transformation is the presence of phase boundaries between the mineral individuals (in the subsystem mineral aggregate). The interaction of the mineral individuals (related to presence or absence of "agent-moderator") realizes either in fluid medium, needed for conduction of the chemical reactions, or via solid-state reaction.

9. The defects in the crystal structures of the mineral individuals are peculiar "locks", along which the energy (and the substance) circulates during their transformation. The packing defects in the mineral individuals, which build the mineral aggregates, at this level determine the speed of the transformations.

10. All system-forming processes proceed in gradient fields, which determine their directions (vector directed) in space and time depending on their potential.

2. Nanosized phenomena in minerals a review of the studies in CLMC (B. Zidarova)

Since the end of 20-th century nanomineralogy started an active development in many countries. A specially organized commission by UN has added such type of studies to the most perspective scientific problems and technologies of 21-st century. The objects of this scientific branch are looked upon as pre-mineral forms of organization and its main purpose is investigation on micro- and ultra-micro levels. Due to their actively developed surface the nano-individuals significantly differ from the macro- and micro-individuals in form and physical-chemical properties (mainly melting temperature, reactivity, electrical conductivity, magnetic properties, strength). Namely, on a nano-level a new type of structure-morphologically ordered objects, play a constructive role in the mineral world. The structure, composition and properties of the nano-individuals are still insufficiently studied. Specific objects can be subdivided on a nano-level, which combine the properties either of mineral or molecule (molecule-crystal, nano-protocrystal). The structural and morphological features of the nano-individuals are as follows: spheroid, fibroid, capsule, and thin layer. The nano-structures consist of phase-specified nano-individuals and are structural elements of the micro-individuals in minerals and biological organisms, which determine many of their useful properties.

Various physical and chemical processes are responsible for structuring, condensation or dispersing of the mineral matter to nano-particles. The genesis and nature of the nano-individuals are pre-determined by several types of mineral-forming processes, namely: physical ultra-dispersion (in the zones of physical and chemical weathering); chemical ultra-dispersion during surface and volume processes; condensation of atoms, molecules, and other crystal forming particles (a result of reactions in water solutions, flux, gasses, etc.); biogenesis (minerals, formed in live organisms or with their participation); technogenesis (connected with emissions of solid and mineral particles in the atmosphere and hydrosphere during different industrial productions). The encountered processes lead to formation of mineral individuals in nature and are background for preparation of nano-particles in laboratory and industrial conditions.

In the Central Laboratory of Mineralogy and Crystallography objects of study are nano-sized minerals and possibilities for their utilization, namely:

The studies on nano-level reveal new perspectives for discovering of the mechanism of origin and growth of crystals.

Problems and ways in developing of nano-mineralogy are:

Nano-mineralogy has possibilities for technological achievements in the industry and in particular: the raw material branch (for utilization of natural nano-sized stuff); agriculture (for soil meliorants); creation of new high-technological nano-materials (catalysts, heat-exchangers, sorbents, etc.);

CLMC has qualified specialists in this field and the background for education of young scientists. However, new laboratory equipment is needed in order to ensure functional scientific and technological nano-mineralogical sector [118].

3. Lozen metagranite, Belassitsa Mountain evidence for widespread distribution of Ordovician metagranitoids in the Serbo-Macedonian Massif, SW Bulgaria (L. Macheva, I. Peytcheva, A. v. Quadt, N. Zidarov, E. Tarassova)

The Lozen metagranite is exposed as a ~6 km2 NW-SE elongated body in the northern slopes of Belassitsa Mountain (the most south-western part of Bulgaria). It forms about 350 m thick sheet, underlain by strongly mylonitized plagioclase-bearing kyanite-garnet schists and tectonically overlain by amphibolites.

Lozen metagranites are medium- to coarse-grained, equigranular to porphyritic, with alkali-feldspar porphyroclasts up to 5 cm in size. Elongated melanocratic enclaves and biotite-rich schlieren, foliated parallel to the rock fabric, are abundant in an unevenly deformed metagranites. Relic magmatic texture is preserved only in porphyroclastic metagranites. They are characterized by large K-feldspar megacrysts within a more ductile fine- to medium-grained matrix of quartz, muscovite, biotite, plagioclase and K-feldspar. In weakly deformed parts not only K-feldspar, but also biotite and plagioclase are preserved as magmatic relics, mainly poikilitic included in K-feldspar porphyroclasts. Feldspars, which behave in both plastic and brittle fashion, show size reduction through fracturing, grain boundary migration and/or subgrain rotation. In strongly deformed rocks feldspar augens recrystallized to coarse polygonal aggregates, which points to a high temperature deformation. Idiomorphic relic plagioclase crystals with corroded edges are often included in K-feldspar augens. New plagioclase is formed at the expense of magmatic crystals and is observed as recrystallized small polygonal grains. In strongly deformed parts of the rock, aggregates are interconnected defining its foliation. Relic biotite porphyroclasts in the rock matrix are also frequent. White mica is rare and formed at the expence mainly of magmatic biotite. Magmatic quartz is entirely recrystallized in coarse-grained lenses, which in mylonitic augen gneisses commonly formed "core-and mantle" structure and "type-4" quartz ribbons (after Boullier and Bouchez, 1978). The serrated edges of the large grains, the presence of subgrains and of deformation lamellaes, point to the high temperature recrystallization mechanisms of the mineral via subgrain rotation and grain boundary migration. Accessory phases are apatite, zircon, opaque, garnet, ilmenite.

The mineralogy of quartz-feldspar rocks is not suitable for geothermobarometric studies. Therefore, estimations of PT conditions of metamorphism are indirect, based on mineral recrystallization textures. The temperature of metamorphism is relatively high (>500-550°C), but traces of migmatization are not observed.

The major element analyzes of whole rock samples from Lozen metagranites point to their corundum-normative, peraluminous character (ASI 1,08-1,49). Chondrite-normalized REE patterns show small variations, and resemble those of Ograzhden metagranites with УREE 130-234, LaN/YbN 5-13 and Eu/Eu* 0.44-0.80. Accepting the validity of Harris et al. (1993) modeling on the basis of the Rb/Sr ratio it would appear that Lozen metagranites (Rb/Sr 0.21-1.40) were formed by vapour-present melting. The distribution of trace elements concentrations, normalized to the upper crust show good resemblance on the Speider diagrams, which suggests derivation by crustal melting.

Precise single grain U-Pb ID-TIMS and in situ LA-ICP-MS methods are used for dating of zircons from the Lozen metagranites (sample A-31). They are combined with Hf-isotope studies of the dated grains to unravel the magma sources. Three out of four long prismatic zircons are concordant and define a Concordia age 451.9±1.3 Ma (Fig.1), whereas one grain is slightly discordant and shows negligible lead loss (generally at Variscan time).

Fig. 1. Concordia diagram for zircons of Lozen metagranite
(sample A-31).

Fig. 2. CL images of zircons from sample A-31 (Lozen metagranite).
The circles show the location of the LA-spots with the corresponding 238U/206Pb age.

In situ LA-ICP-MS analyses are in agreement with the conventional data. Zones with magmatic oscillatory zoning (Fig. 2) define a mean 238U/206U age 462±17 Ma (2у errors), and inherited cores in two zircons are 550-580 Ma old (Fig. 2b). The magmatic age of the Lozen metagranite coincides within the error limits with the age of the Ograzhden metagranites, dated at 459.9±7.6 Ma (equigranular variety) and 451+18/-9 Ma (porphyritic variety) (Ann. Report CLMC, 7/2003). The same is observed in the е-Hf characteristics of the studied zircons: they range between -1.4 and -3.1 in the Lozen metagranites and between -2.6 and -4.4 in the Ograzhden metagranites. The identical age, zircon peculiarities and е-Hf source characteristics argue for a common origin of the rocks and for wide distribution of Ordovician metagranites in Belassitsa and Ograzhden Mountains [22].

4. Isotope geochemistry, geochronology and magmatic evolution of Petrochan, Klissura und Lutskan plutons in Western Bulgaria (I. Peytcheva, E. Tacheva, A. v. Quadt, R. Nedialkov, M. Dyulgerov, O. Malinov)

The Petrochan and Klissura plutons are exposed in the core of Berkovitsa anticline, SE-NE of Berkovitsa town in the Western Balkan. Usually, they are considered as part of the Variscan "Stara Planina Calc-Alkaline Formation", but some authors describe the Klissura pluton as diatectites of the Burzya migmatitic complex with a probable Cambrian age (Carrigan et al., 2003). We obtained new field, petrological, geochemical and isotope-geochronological data for both plutons with the aim to understand their geotectonic position, generation and relationships.

Klissura and Petrochan plutons have Ca-alkaline affinity and reveal equigranular and porphyritic textures. Klissura pluton is built up only by acid rocks granites and granodiorites. The combination of conventional ID-TIMS and LA-ICP-MS zircon/monazite studies define an age of 332±7 Ma (Fig. 1). Zircon e-Hf values are mainly negative and define crustal dominated magma source [35].

Fig. 1. U-Pb concordia diagram for zircons of samples
AvQ135-C1 and AvQ-136, Klissura granite.

The Petrochan pluton is an I-type intrusive with calc-alkaline affinity. It is built up by gabbroic to granitic rocks with a prevailing distribution of the acid and intermediate varieties [35, 41]. The pluton is metaluminous in composition with an increased Na/K ratio. Mafic magmatic enclaves (MME) are a characteristic feature of the Petrochan pluton in the outcrops south of Spantchevtsi village. The MME reveal transitional compositions between gabbroic and granitoid magma and range mainly from diorites to gabbrodiorites. They have similar mineral composition to the granitoids of the Petrochan pluton, but with a different proportion of the main rock-forming minerals. Needle apatite, elongated hornblende crystals and plagioclase enclaves with a high anortite component in the accessory sphen result obviously from the fast cooling of the primary hot gabbroic magma. MME field relationships of the basic and acid varieties and characteristic petrographic and geochemical features give evidence for processes of magma mingling and mixing, additional to the normal AFC processes [41], whereas the basaltic magma intruded in not fully solidified granitoid mush in a middle/upper crust magma chamber. U-Pb dating of the Petrochan pluton follows the idea of Haydoutov et al. (1992) for prolonged magma replenishment. Granodiorites are dated at 307 ± 1 Ma, and the hybrid gabbro of the Spantchevtsi quarry at 302.7 ± 3.3 Ma. In the same range is the age 304 ± 4 Ma, calculated by in situ SIMS dating of Carrigan et al. (2005). The positive (age corrected) e-Hf of dated zircons (mainly between +2 and +5) gives evidence for mixed crustal-mantle origin of the magma and confirms the idea for the post-collisional tectonic setting of their generation [35].

The Lutskan magmatic complex belongs to the Kraishte tectonic zone in Bulgaria. It crops out south from the town of Trun between the villages Ezdimirtsi, Velinovo, Erul and Milkiovtsi (Lutskan pluton), in a small body northern of Trun and in Rui Mountain (Rui pluton). The rocks of the complex intrude rocks metamorphosed in amphibolite facies with presumed Precambrian age (Zagorchev et al., 1995). Part of the country rocks belong to the diabase-phyllitoid complex. The intrusive rocks of Lutskan complex are covered by Permian sediments. Traditionally, the Lutskan pluton is regarded as a complex magmatic body, built up by several phases, with clear successive relations between them. The first intrusive phase is represented by melanocratic gabbro-diorite varieties, followed up by granites and leucocratic aplitic granites. Transitional-alkaline, alkaline syenite- and granite porphyries are described as a last magmatic phase. The distinction between the magmatic phases follows a logic and standard succession in the evolution of magmatism from more basic to acid varieties. Our field observations showed that the relations between the magmatic phases are more complicated and ambiguous [8] and that the intrusive rocks cropping out north of Trun, near Erma River are gabbros and diorites in composition (not granitoids as shown on the geological map of Bulgaria, 1:100 000).

Petrologic, isotope geochemical and geochronological studies reveal different ages and distinct geochemical features for the diorites and granitoides of Lutskan pluton. The diorites (sample Tr18) are Cambrian in age (537 ± 1.7 Ma, TIMS data and consistent in situ LA-ICP-MS, Fig. 2) and can be correlated with the rocks of Struma Diorite Formation/Struma Unit, which are exposed wider south of the Trun region. The diorites show eHf-zircon values between +8.9 and +12.4 [12]. They have flat HREE distribution, Nb-Ta and Ti negative anomalies, calc-alkaline affinity and slight enrichment in LILE and LREE. These features are consistent with a subduction-related geodynamic setting. Isotope and geochemical signature suggest generation of the magma in a subcontinental mantle lithosphere, which was mildly enriched in LILE as a result of subduction related slab dehydratation.

Fig. 2. CL images of zircons from sample Tr18 and Tr11a (Lutskan pluton).
The circles show the location of the LA-spots with the corresponding 238U/206Pb age.

The granitoids (sample Tr11a) from the other side are Variscan in age (334.1 ± 1.2 Ma titanite conventional dating and corresponding in situ LA-ICP-MS zircon data, Fig. 2) and collision- or postcollision related. They present elevated LILE/HFSE ratios, fractionated trend of REE, important contents of Th, U, K, and isotropic fabrics. The e-Hf-zircon isotope signature of granitoides indicates the important role of crustal material in the magma generation [8]. Geochemical characteristics of the granitoids imply melting of crustal materials with mixed crustal-mantle origin. Subordinate input of mantle components could explain the presence of MME, the chemical heterogeneity of the rocks and the similarity in the distribution of some trace elements with that in the diorites.

5. Isotope-geochemistry and geochronology of magmatism and related Cu-Au ore formation in Western Srednogorie, Eastern Serbia and Banat, Romania (I. Peytcheva, A. v. Quadt, D. Dimov, K. Naydenov, D. Stoyanov)

The Apuseni-Banat-Timok-Srednogorie (ABTS) belt is Europe's most extensive belt of calc-alkaline magmatism and Cu-Au mineralization. The Medet copper deposit - Bulgaria's first known porphyry type deposit is situated in the central part of the Srednogorie zone and related to this belt. The main magmatic activity is around 90 Ma, but isotopic data seems controversial, as white mica (sericite) reveals 40Ar-39Ar plateau ages of 79.0±0.8 Ma to 79.5±0.7 Ma (Lips et al., 2004; Handler et al., 2004). We sampled therefore the so called "late spessartite" dyke in the open pit, which cross-cut all previous porphyry rock varieties. It is high-K granodioritic in composition and not lamprophyric, as feldspar builds up part of the porphyries. Four zircons (two abraded and two not abraded) yield a concordia age of 89.26±0.32 Ma (Fig. 1). The data give evidence for a short life-span of the magmatism in the Medet deposit less than 1 Ma (from 90.4 to 89.3). Therefore, the K-Ar and Ar-Ar younger aging of sericite has to be related to low-temperature fluids heated by late deep magma chambers in the Central Srednogorie. The e-Hf zircon values (corrected for 90 Ma) of the Cretaceous shallow intrusion range from +1.4 to -0.9 and are close to zircons with lead inheritance (from +2.9 to -2.3). These data define the lower and middle crust as a source material, which was mixed with an enriched mantle magma prior to crystallization of zircons[109, 112].

Fig. 1. Concordia diagram for zircons
from sample AvQ-210. 		Fig. 2. Concordia diagram for zircons from sample AvQ-122, Chuchuliga granite. The e-Hf values (corrected for 69 Ma) are written to the corresponding zircon grains.

Some magmatic rocks in the Rhodopes Mountain reveal isotope-geochemical characteristics, which are similar to the Srednogorie-type magmatism. This is recently suggested for the granitoids of the first unit of Rila-West Rhodopes batholith (Belmeken and Gruntcharitsa bodies), which were dated between 66.5 and 69.5 Ma (the error uncertainties included). Similar ages yield the Chuchuliga and Rosino granites in Eastern Rhodopes [23]. Conventional ID-TIMS single zircon U-Pb analyses of zircons from the Chuchuliga granite (sample AvQ-122, Fig. 2) define a concordia age of 68.94 ± 0.40 Ma. The zircons of Rosino granites show a more complex composition. All five analyzed grains reveal inheritance and define a discordia line with a lower intercept age 68 ± 15 Ma (one grain is almost concordant at ~70 Ma) and an upper intercept age of 482 ± 27 Ma. The majority of the zircons are closer to the lower intercept, which obviously is informative for the crystallization time of the granites. Within error uncertainties it coincides with the age of Chuchuliga granites. The upper intercept of the discordia gives evidence for assimilation of the Early Paleozoic materials. One apatite sample from the Chuchuliga granite has been analyzed for Sr isotopes and revealed a comparatively low 87Sr/86Sr isotope ratio (0.70616). It is in agreement with the mixed crustal-mantle composition of the magmatic zircons in both granites, as they reveal slightly positive e-Hf (corrected for 69 Ma) values from +0.5 to +2.7. It must be noted that in zircons with lead inheritance (containing older cores) the e-Hf becomes respectively crustal dominated with negative values between -5 to -7. The isotope data are consistent with the generation of granites from a mantle derived magma, which was contaminated with a crustal material and evolved trough assimilation-fractional crystallization processes.

Additional proofs for Srednogorie-type materials in the frame of Rhodopes Mountain are found in the northern parts of Central Rhodopes between the villages Brestovitsa, Parvenets and Assenovgrad [61]. They are built up by variegated lithologies and characterized by complicated tectonic relationships resulting from the prolonged activity of the Maritsa fault zone. Low metamorphic rocks prevail in the succession of the described area. Together with the two mica gneisses with boudines of amphibolites, which were overtrusted (?) from NW, they are considered as a part of the Thracian unit (Sarov et al., 2006). We sampled the gneisses in an outcrop west of Parvenets (5672a) and studied them in cooperation with "Geology and Geophysics" JSCo. Conventional U-Pb-zircon method and ID-TIMS (Isotope Dilution Thermal Ionisation Mass Spectrometry) techniques are combined with in-situ LA-ICP-MS analyses of zircons to unravel their magmatic to metamorphic history. In Parvenets gneisses (5672a) we distinguish 2 main types of zircons: (i) beige-brownish, transparent to semi transparent, and (ii) almost colorless, transparent. Prismatic grains prevail, whereas in the small size fractions they are mostly long prismatic. In the bigger fractions the content of the shorter crystals increases. All zircons are slightly rounded. Conventional U-Pb analyses show lead inheritance, as well as lead loss in the measured grains. They define discordias, which in both cases cross the Concordia at ~330-340 Ma. Lead loss is observed mainly in the brownish zircons and is obviously related to the Alpine overprint. CL and BSE images of zircons show inherited cores with Lower Paleozoic and older ages, and outer parts with oscillatory magmatic zonation. These peculiarities are interpreted as formation of crustal peraluminous synmetamorphic (?) granites in the Carboniferous, which were metamorphically overprinted in Late Alpine time. All e-Hf values at 330 Ma define a crustal source lying between -4.3 and -6.7 in some older parts of zircons decreasing to -8.9. The data are consistent with the age of the migmatic veins in Central Srednogorie, determined at 336.5 ± 5.4 by Carrigan et al. (2006). This fact allows a correlation with the basement of the Srednogorie zone and suggests a synmetamorphic generation of these granitic melts. After the accretion to the Rhodopes the metagranites together with the cross-cutting gabbroic bodies (amphibolites of sample 5672) suffered the Late Alpine metamorphic overprint.

ID-TIMS dating and LA-ICP-MS analyses of zircons from fertile and not fertile magmatic rocks in Apuseni Mountains, Romania [20], showed that porphyry ore-formation at Valea Morii deposit occurred between 11.41 ± 0.03 Ma and 11.30 ± 0.05 Ma, about 1 Ma after the main volcanic activity. At that time the magma chamber reached oxidized conditions, favourable for release of ore-forming magmatic hydrothermal fluids.

In Zidarovo ore field (Eastern Srednogorie), despite some variations in the REE distribution Ruskov et al. [36] and Georgiev et al. [86] suggest high-K calc-alkaline affinity and island-arc characteristics of all Upper Cretaceous volcanic, dyke and intrusive rocks. The magmatism is mantle dominated. Compared with the isotope characteristics of contemporary rocks in Central Srednogorie it was less crustal influenced (e-Nd from +2.1 to +3.0 and initial strontium ratios of 0.704-0.705).

6. Comparative characteristics of carbonate-hosted sedimentary exhalative polymetallic deposits (Z. Damyanov)

Analysis of the basic characteristics of recent and ancient (fossilized) Fe-Mn ore mineralizations was made within the framework of the performed comparative characterization of carbonate-hosted sedimentary exhalative polymetallic deposits. As a rule, these mineralizations are genetically and spatially related to polymetallic (Pb-Zn-Cu-Ba-Ag-Hg) ones in depth, thus being distal (upper, outer) elements of complex ore deposits with a complicated geological and ore structure. They were formed in seafloor depressions in an environment of arid climate, very low terrigenous input, weak transportation ability and passive tectonic regime (zones of incipient rifting or along deep-seated faults in passive continental margins). The sources of ore matter are hydrothermal solutions venting onto the seafloor, cooling and mixing with the seawater in different proportions. The ore formation is intimately dependent on the running in the basin chemical to weak biochemical processes of marine carbonate lithogenesis and because of that the ore occurrences have all typical characteristics of the carbonate sedimentary formations. The local changes in the facial setting during precipitation define their mineralogical type dominant Fe(+Mn)-carbonate or more rare Fe-oxide (under oxic conditions onto the depression slopes). The available geochemical diagnostic diagrams for the recent metalliferous Fe-Mn sediments from the rift zones of the World Ocean and some marginal seas were analyzed and adapted to the fossilized sedimentary exhalative Fe-Mn deposits. Genetically most informative of them are the following triangle diagnostic diagrams: Fe-Mn-Al, Fe-Mn-Si, (Fe+Mn)-Ba-Si, and Fe-Mn-(Pb+Cu+Zn). One of the most important criteria to distinguish the carbonate-hosted sedimentary exhalative Fe-Mn deposits from all other types of Fe-Mn mineralizations is the presence of specific (by morphology, structure, composition and mineral variety) authigenic Fe-Al phyllosilicate mineral assemblage.

7. Late Alpine epithermal gold mineralizations in the Kesebir Gneiss Dome, East Rhodope Mt (I. Marinova)

Studies on the electrum mineralization from the Stenata outcrop, Khan Krum gold deposit, were further continued in 2006 [24, 25, 26, 27]. Textures from the layer-like pervasive silicification in the Stenata outcrop were investigated and three genetic groups of textures were recognized: 1) replacement, 2) open-space fillings, and 3) brecciated.

Massive, grid-work, platy bladed and lattice bladed replacement textures were established [25]. The massive texture is the major one in the pervasive silicification and together with the grid-work texture indicate that the layer-like pervasive silicification was deposited by highly supersaturated hydrothermal solutions in respect to quartz. The platy bladed and the lattice bladed textures are a result of replacement of platy calcite by microcrystalline quartz and are indicative of fluid boiling. The scarce distribution of the later textures in the layer-like pervasive silicification marks low extent of fluid boiling during its formation.

The open-space filling textures in the layer-like pervasive silicification from the Stenata outcrop are represented by banded, colloform banded, crustiform and comb ones [26]. They were observed in joints, which cross-cut the layer-like pervasive silicification. The first two textures are represented by a rhythmic alternation of bands composed of microcrystalline quartz, quartz + adularia, adularia and partially crystallized opal, and often of banded electrum. These two textures are indicative of intensive boiling of the hydrothermal solutions (presence of adularia) or of mixing with ground waters and high supersaturation in respect to the opaline silica. The adularia-containing colloform banded texture can serve as a textural indicator for high-grade electrum.

The following brecciation textures from the layer-like pervasive silicification in the Stenata outcrop were recognized: stockwork, breccious, veinlet and jigsaw-fit puzzle ones [27]. The most widespread fractures in the layer-like pervasive silicification are the joints. The diversity in their morphology and size shows different intensity of brittle deformation and the cross-cutting relationships multiple episodes of jointing and brecciation, infilling the open space with electrum-bearing fluids and postmineral jointing without hydrothermal infilling. Due to multiple episodes of jointing and brecciation, one could propose a multiple deposition of electrum, which favoured the high gold grade of Khan Krum deposit. The sealing and healing of joints by quartz, adularia and partially crystallized opal suggest formation of the brecciation textures in a fluidized medium, i.e. by fluidofracturing being probably a result of multiple overpressure of the hydrothermal fluids in depth.

Preliminary data on the morphology of electrum from the layer-like pervasive silicification were also obtained [24]. It was established that the electrum is micron-sized and forms: 1) dispersed grains in the massive, microcrystalline quartz, 2) grains in interstices of the massive, microcrystalline quartz, 3) filamentary crystals in voids, 4) clots of irregular grains in colloform banded textures, and 5) dendrites in colloform banded textures. It is supposed that the dispersed electrum grains were deposited simultaneously with the massive, microcrystalline quartz. It can be concluded that the combination of filamentary and dendritic electrum with adularia- and opal-containing colloform banded textures is an indicator of highly nonequilibrium conditions of deposition (intensive boiling and high supersaturation of the hydrothermal solutions) after the formation of layer-like pervasive silicification in the Stenata outcrop.

8. Rare Bi and Ni minerals from the Martinovo iron skarn deposit, Northwestern Bulgaria (D. Dimitrova, E. Tarassova, M. Tarassov)

Rare Bi and Ni minerals found in the Martinovo iron skarn deposit (Perchinki and Mali Dol mine sections), Northwestern Bulgaria, were studied by optical microscopy and electron probe microanalysis [7]. The mineralizations are related to the postmagmatic activity of the Sveti Nikola granite pluton of Paleozoic age intruded into the low-grade metamorphic rocks of the Diabase Phyllitoid Complex. The established Bi and Ni minerals are spatially associated with pyrrhotite ores as well as with zones of wallrock (skarns, marble, schists) alteration. The following minerals are identified: bismuth minerals - native bismuth, bismuthinite, tellurian bismuthinite (?), joseite-B; Pb-Bi sulphosalts - cosalite and lillianite; and nickel minerals cobaltian gersdorffite and antimonian gersdorffite. Accompanying subordinate ore minerals are chalcopyrite, galena, sphalerite, native gold and electrum. Native gold associated with native bismuth is observed in pyrrhotite aggregates. Electrum with sphalerite occurs as veinlets within pyrite aggregates from silicificated schists.

Both, Bi and Ni, mineralizations are not observed in any direct relationships with each other. Therefore, conclusions on their origin and relations are drawn using textural and chemical criteria as well as the known tendencies in the geochemical evolution of the hydrothermal mineral-forming processes in the deposit. The principle mineral-forming trend in the deposit is the regular gradual evolution and alternation of iron minerals: hematite - magnetite - pyrrhotite (pyrite) - arsenopyrite - (loellingite). In this respect, one can suggest that the two described gersdorffite varieties crystallize under conditions of increased activity (fugacity) of sulphur and arsenic (comparable with that necessary for formation of arsenopyrite). At the same time, the close association of gersdorffite with chalcopyrite indicates the important role of copper in the hydrothermal solutions. The third notable aspect concerning the Ni mineralization is its spatial localization in the hydrothermally altered schists (primarily metamorphosed diabase tuffs) at the upper levels of the ore bodies. The latter fact most probably is an evidence for influence of the chemical composition of the primary host rock (possible source of nickel) onto the type and composition of the ore minerals formed. The presence of two closely associated varieties of gersdorffite enriched in Co and Sb, respectively, is the other noteworthy feature of the Ni mineralization. The antimonian gersdorffite seems to be a later variety of this mineral marking an essential increase in the activity of antimony species in the hydrothermal solution. However, the presence of antimony in the studied Ni minerals seems to have a local significance not influencing the other polymetallic mineralizations, as those of bismuth. For example, we have established only the Bi sulphosalts being without any indications for Sb presence - either as minor element in the Bi minerals or as own sulphosalt phase.

The diversity of Bi minerals (native Bi, bismuthinite, joseite-B, cosalite, lillianite) and their textural relationships well correspond to the empirically established tendencies in the formation of Bi minerals in postmagmatic hydrothermal environments related to granite intrusions: native Bi + Bi sulphide + Bi sulphotelluride ® Pb-Bi sulphosalts. In our case, bismuthinite occurs always in close association (aggregates) with native Bi and joseite-B. It is noteworthy that native Bi is encountered also as individual grains, even in samples containing gersdorffite. This is the only case, when we found Ni and Bi minerals in one and the same sample.

An additional common feature of the two mineralizations is their close association with chalcopyrite. The textural relationships between the Bi minerals do not show any distinct indications for hypogene chemical alteration (replacement) of the primary Bi minerals. At the same time, the established native Bi bismuthinite intergrowths could be explained as a result of decomposition of a preceding mineral phase, stable at higher temperature (i.e. Bi4S3 analogous of ikunolite). The formation of Ag-containing Pb-Bi sulphosalts (cosalite, lillianite) is an indication of the further evolution of the hydrothermal mineral-forming processes transition to Pb-Ag mineralizations which are widespread southeast of the Martinovo deposit.

9. Mineral composition and comparative characteristics of Bulgarian Oligocene phosphorites (V. Stoilov, I. Donchev, O. Petrov, V. Petkova, Y. Kalvachev, N. Lihareva)

Two poor in phosphates Oligocene phosphorite deposits of volcanogenic-sedimentary origin have been investigated, namely Gorna Glogovitsa and Dalbok Izvor ones. The samples were taken from different points of old exploration places. The mineral, crystal chemical and structural features of the samples have been studied by powder X-ray diffraction (XRD) analysis, differential thermal gravimetric analysis (DTA/TG), scanning electron microscopy (SEM) and infrared (IR) spectroscopy [75].

Two poor in phosphates Oligocene phosphorite deposits of volcanogenic-sedimentary origin have been investigated, namely Gorna Glogovitsa and Dalbok Izvor ones. The samples were taken from different points of old exploration places. The mineral, crystal chemical and structural features of the samples have been studied by powder X-ray diffraction (XRD) analysis, differential thermal gravimetric analysis (DTA/TG), scanning electron microscopy (SEM) and infrared (IR) spectroscopy [75].

Gorna Glogovitsa deposit. The mineral composition in the samples from the deposit, proved by XRD, is mainly of quartz, calcite and apatite (Fig. 1). After preliminary calcite dissolving the presence of plagioclase (with prevailing anorthite component) was also established. The apatite mineral cannot be determined exactly because of its fine crystalline state resulting in very broad diffraction peaks.

Fig. 1. Powder XRD patterns of phosphorite samples
from Gorna Glogovitsa deposit initial, after heating at 1100°C and after calcite dissolving (ammonium citrate, pH=6 and pH=7.1) and subsequent heating at 1100°C

Fig. 2. Infrared spectra of phosphorite sample from
Gorna Glogovitsa deposit after preliminary ammonium
citrate dissolving pH=6 (a) and of its variety
after heating to 1100°C (b)

The average size of the apatite microcrystallites (defined by profile analysis of its powder diffraction peaks) are in the range between 60 and 150 Е in directions normal to the crystallographic planes (211), (112) and (300), and about 260 Е in direction [001]. After heating to 1100°C apparent apatite recrystallization is established, which results in sharpening of the characteristic diffraction lines with d-spacings of 2.79, 2.77, 2.70 and 2.62 (Е) (Fig.1), giving increase in sizes of crystallites to 350-550 Е.

The IR spectrum of the sample from Gorna Glogovitsa deposit after treatment with ammonium citrate solution and that after heating the latter to 1100°C (Fig. 2) do not display the characteristic bands of calcite. However, the low intensive bands at 873 and 1426 cm-1 are characteristic for the CO32- group, which is by no doubt incorporated in the apatite structure. The broad band between 3660 and 3150 cm-1 belongs to stretching mode of OH- groups, connected with F or another OH- group by means of hydrogen bonds. After heating of the sample this band becomes narrower and a new band appears at 3538 cm-1, which is characteristic of OH-F bond thus showing presence of high fluorine content.

The DTA/TG analysis of the initial sample shows weight losses of 23.8 wt.% in the temperature interval 660-780°C, and the respective endothermal effect at about 762°C is due to possible decarbonatization of calcite. The sample purified from calcite displays important thermal effects in the temperature interval 600-840°C. These endoeffects are related with 0.84 wt.% weight loss at 659°C and 1.07 wt.% weight loss at 759°C, due to separation of constitutional water and decarbonatization, respectively. As the sample does not contain calcite, this endoeffect can be due to CO32-groups, incorporated as additional anions in the apatite structure.

The obtained DTA/TG results correlate with the data from XRD analysis and IR spectroscopy in respect to the presence of structurally incorporated CO32- groups in the studied apatite, which confirms the presumption for partial substitution of PO43- by CO32- groups. Therefore, the apatite in the samples from Gorna Glogovitsa deposit can be defined as carbonate-fluorapatite.

Dalbok Izvor deposit. The proved minerals in this deposit are fluorapatite, quartz, plagioclase, montmorillonite, sanidine and insignificant amounts of amphibole and mica (muscovite?). The powder XRD pattern (Fig. 3) shows that the phosphate mineral is well-crystallized fluorapatite. Its basal peaks are quite intensive, which is a result of predominant texturing of the crystals in direction [001] due to their platy habit. This is well proved with SEM analysis showing hexagonal platy fluorapatite crystals (Fig. 3).

The profile analysis of the peaks in the powder XRD pattern of a sample from this deposit gave average size of the apatite microcrystallites as follows: in direction [001] (diffraction line 002) they are 1000-1100 Е and are nearly twice bigger than the sizes in directions normal to (211), (112) and (300) 550-600 Е. These results show significant difference in the size of the apatite microcrystallites from both deposits.

The IR spectroscopic analysis of a sample from Dalbok Izvor deposit reveals the characteristic bands of apatite. Bands typical for calcite are not observed but at 841 and 1458 cm-1 there are low intensive bands characteristic for CO32- groups incorporated in the apatite structure.

Fig. 3. Powder XRD pattern of a representative
phosphorite sample from Dalbok Izvor deposit

DTA\TG analysis shows mass losses in the interval 220-650°C. They are probably due to multi-stage separation of structurally bound water molecules and OH- groups from smectite and mica. On the DTA curve there is registered a weakly pronounced endothermal effect in the interval 800-930°C, accompanied by insignificant mass loss (0.43 wt.%). This endoeffect is probably due to a low portion of CO32- groups in the fluorapatite structure. In conformation to this the bands at 841 and 1458 cm-1 in the IR-spectrum of the heated sample are already not present.

The comparison of the XRD powder patterns of a sample from this deposit (Fig. 4), heated to different temperatures shows thermal instability of fluorapatite at values significantly lower than Tmlt. At 950°C the sample has almost lost its smectite and mica components. When heated at 1100°C the apatite in the sample transforms to б-Ca3(PO4)2 , the plagioclase is nearly unchanged, while quartz is fully preserved.

As a result of this study, new data are obtained for the mineral composition, crystallinity and structural specificity of the phosphate matter in the samples from Gorna Glogovitsa and Dalbok Izvor deposits. It is shown that after appropriate chemical treatment with ammonium citrate solution (pH=6) it is possible to dissolve calcite and enrich the sample in phosphate matter, which allows exact characteristics of apatite.

Fig. 4. Powder XRD patterns of a representative
phosphorite sample from Dalbok Izvor deposit and
after heating at 950 and 1100°C, recorded
at room temperature

The mineral composition of the phosphorites from both deposits differs in Gorna Glogovitsa deposit predominates the sedimentary-diagenetic component (calcite), while in Dalbok Izvor deposit predominating are the minerals of volcanogenic-hydrothermal origin.

The apatite mineral in Gorna Glogovitsa deposit is determined as carbonate fluorapatite (the so-called "francolite type"), while in Dalbok Izvor deposit it is typical fluorapatite. The latter when heated undergoes structural changes, probably because of critical loss of structurally incorporated CO32- groups, which leads to the formation of б-Ca3(PO4)2. The clarification of this effect requires additional investigations.

The investigation of the features of phosphate matter in volcanogenic sediments shows that micrograined phosphorites differ in degree of crystallinity of apatite. The carbonate fluorapatite from Gorna Glogovitsa is with markedly small crystallite size (up to 260 Е) and the fluorapatite from Dalbok Izvor is characterized by an ordered structure and bigger crystallites (up to 1100 Е).

The presence of additional anionic groups in the structure of fluorapatite is a good precondition for subsequent application of the mechano-chemical and thermo-chemical activation methods, with the goal to obtain suitable products for soil amendment and fertilizing.

10. Crystal chemical and structural peculiarities of staurolite from rocks undergone different metamorphic evolution: FTIR spectroscopy study (V. Ganev, L. Macheva)

The local structural peculiarities of staurolites were investigated by unpolarized FTIR absorption spectroscopy [10]. Samples from 3 regions differing in their metamorphic evolution were selected metapelites from the region of Biala reka (East Rhodopes), (L-series), orthoschists from the region of Ograzhden Mountain (M-series) as well one sample from the metapelites of the Ustrem formation in Sakar Mountain (C-series).

For the first region the metamorphic history has been well established with clockwise P-T-t path - an early HP/LT episode (Pmin = 13 kbar and T » 450°C), related to rapid crustal thickening followed by isothermal decompression (MT/MP - P 9-3 kbar and T » 550°C) and a final cooling episode of LT/LP type (P 3-2 kbar and T » 400°C). Staurolite was formed during the entire MT/MP episode.

The samples from Ograzhden Mountain were selected from orthoschists, in which relic kyanite and garnet are preserved. The calculated metamorphic conditions for this metamorphic episode are T ~ 670°C and pmin = 7 kbar. Staurolite and chloritoid are formed at Tmax ~ 550°C after almost entirely sericitized kyanite porphyroblasts.

The metamorphic conditions for the staurolite-bearing rocks of the Ustrem formation in Sakar Mountain, as estimated by Chatalov, Grozdanov (1978), are T~450-600°C and P=1.8-6 kbar.

EMPA data on staurolites from L- and M-series do not show any remarkable differences in their chemistry. The generalized formula of the studied staurolites can be written as Fe1.27-1.73Al8.63-8.95Si 3.77-3.94O23(OH) and Fe1.49-1.69Al8.63-8.88Si 3.78-3.92O23(OH) for L- and M-series, respectively. They are unzoned, Fe-rich, with a Fetot/(Fetot+Mg) ratio of 0.72-0.85 and 0.77-0.82, respectively, Ti-poor (0.2-0.10 p.f.e.) and with ZnO content in the range 0-1.59 and 0-0.75 for L- and M-series, respectively. EMPA analyses of staurolite from the C-series were not done. The similarity in the chemical composition of the staurolite samples from the three regions does not allow making any inferences about the metamorphic conditions, regardless the differences in the pertographical observations. Because of that, we have undertaken an IR study of the mineral.

Unpolarized FTIR absorption spectroscopy was applied for investigation of local structural peculiarities of staurolite. The measurements were performed on Bruker TENSOR-37 FTIR spectrometer in the range 4000400cm-1.

Fig. 1. O-H region of the staurolite
IR spectra of samples from: C (Sakar),
L (East Rhodopes) and M (Ograzhden).


Fig. 2. SiO4 region of the staurolite
IR spectra of samples from: C (Sakar),
L (East Rhodopes) and M (Ograzhden).

The IR spectra in the range 3800-3200 cm-1 of the studied staurolites are shown on Fig. 1, where the (O-H, H2O) stretching region of mid-IR spectrum is presented. Three different bands marked A, B and C are distinguished: (i) broad and relatively strong A-band in the range 3500-3300 cm-1 with maximum close to 3400 cm-1; (ii) weak B-band at about 3650 cm-1; and (iii) weak C-band centered around 3750 cm-1. All tree bands could be assigned to asymmetric stretching modes of O-H groups in different structural positions. Pronounced A-band broadening and intensity decreasing in the spectra from M-series are observed in comparison with the L-series. The A-band has composite structure, which could be deconvoluted by use of single Gaussian functions. The B and C bands could not be unambiguously presented in that way, due to the registered low S/N ratio.

The staurolite IR spectra measurements in the range 1500850 cm-1, assigned to n3as vibration mode of the SiO4 tetrahedral group, are shown on Fig. 2.

A band broadening and band intensity decreasing in the spectra of the M-series in comparison with the L-series are distinguished.

The presented FTIR spectra of staurolites from the three studied regions show some similarities, but differences in their thin band structures are also observed. Pronounced decreasing in the intensity of the A-band in the OH-region of the spectrum for Ograzhden staurolite samples in comparison with those from East Rhodopes is established (Fig. 1). This effect could be attributed to differences in the P-T conditions of the metamorphism. The significant variations in the IR spectra of staurolites from the Biala Reka region (East Rhodopes) in the range 3800-3200 cm-1 could be related to the formation of the mineral during the entire process of isothermal decompression (P = 9-4 kbar and T = ~550°C) as is ascertained by the petrological investigations. The intensities of the band in this spectral region are characterized by a great variation as well as in their broadening probably because of the large variations in the fluid supply during the rock exhumation. Based on petrological considerations and peculiarities observed on the IR spectra in the OH range, an assumption could be made that the staurolites from Ograzhden Mountain formed at higher temperature, but in a more limited time interval. The OH A-band in the spectrum obtained from the Sakar Mountain staurolite sample is close to those from Biala Reka.

The fine structure of the staurolite vibration spectra in the asymmetric stretching vibration n3as region presented on Fig. 2 could be assigned to the heterovalent Al®Si isomorphism in T1 structural positions. Because of the bigger Al ionic radius with the increase of pressure a decrease of the Al®Si substitution is to be expected. This process is reflected in shifting of the ~1020 cm-1 main peak position to higher frequencies. The total increase of band intensity in the spectra from Biala Reka-series is also to be expected. Due to the formation at higher-pressure conditions this effect could be partially reduced with increasing the deformation of SiO4 tetrahedra.

Based on the investigations by unpolarized FTIR absorption spectroscopy of staurolites undergone different metamorphic evolution, a clear dependence between their fine structure and P-T conditions of the metamorphism is established.

11. Amphiboles from Vitosha pluton - indicators for the magmatic evolution (S. Atanasova-Vladimirova, I. Piroeva, K. Kouzmanov, B. Mavrudchiev)

Objects of the present study are amphiboles from different phases of Vitosha pluton. These minerals are the most widespread mafic minerals in this geologic body and supply data for the evolution of the pluton. The association of femic minerals in the Vitosha plutonic rocks is characteristic for calc-alkaline granitoids of geochemcal I-type (amphibole, biotite, titanite, magnetite, and ilmenite) [1].

Vitosha pluton is located in the western part of the Srednogorie tectonic zone. The rocks of the pluton have been studied in detail by S. Dimitrov (1942) who determined four intrusive phases: I - gabbroic rocks (gabbro, anorthosite), II - monzonites, III leucosyenites, and IV - granosyenites. Pegmatitic dykes cut each of the intrusive phases. Amphibole is one of the main rock-forming mineral in the pluton and often occurs as secondary mineral in aplites and pegmatites. In the gabbro differentiates its modal content reaches 20-22%, in anorthosites - about 6.3%, in monzonites and syenites - about 4%.

The chemical composition of the amphibole samples is calculated on the basis of 60 microprobe analysis. According to the classification scheme of Leake et al. (1997), the studied amphiboles are calcian ones with (Na+K)A < 0.50. In the calssification diagram the amphiboles from the gabbro, anorthosite, monzogabbro, and monzonite rocks fall into the group of magnesian hornblends and in the syenitic rocks the figurative points are in the area of magnesian and ferroan amphiboles.

The estimated temperatures of crystallization of gabbro (based on the geothermometer of Blundy and Holland, 1997) are between 769834°C, for the core and 759-796°C, for the rims of the plagioclase crystals. Normal and reverse temperature zoning is registered in the investigated plagioclase-amphibole couple. The reverse zoning is characteristic for the gabbro rocks. The parameter Mg# of plagioclase is with values between 70-48, for the core, and 73-53, for the rim (Fig. 1).

The monzogabbro is characterized by normal temperature zoning - 719°C, for the core, and 679°C, for the rim. For the monzonite rocks the estimated temperatures are between 598-721°C, for the plagioclase core, and 579-687°C, for the rim. The syenite rock is characterized by normal temperature zoning - 647-756°C, for the core, and 490-722°C, for the rim.

The calculations of the pressures of formation were performed by the geobarometer of Schmidt (1992). The estimated pressures for gabbro are between 3.5 and 2.6 kbar, which correspond to a depth of 710 km, and for monzogabbro, monzonite, and syenite - 3.12.0 kbar, which correspond to a depth of 9-6 km.

Fig. 1. Amphibole from the pluton in the classification
diagrams of Leake at al. (1997)

As a rule, the tetrahedral aluminium (IVAl) in amphibole decreases with the progress in the magma differentiation. The average IVAl content in amphiboles from gabbro is 0.89, in the cores, and 0.85, in the rims, for monzonite these values are respectively 0.94 and 0.48, and for syenite - 0.97 and 0.18. In the amphibole grains the IVAl content decreases from the core to the rim.

The VIAl contents in the amphiboles generally decrease with the progress of magma differentiation and reflect the Si activity and the degree of polymerization of the magma (Kamenov, 2004). The average VIAl content in amphiboles from gabbro is 0.24, in the cores, and 0.098, in the rims, from monzonite - 0.14 and 0.04, and from syenite - 0.12 and 0.09.

Fig. 2. Diagram IV Al vs. Mg/(Mg+Fe),
ratio ¦O2 plot of Anderson and Smidt (1995)

The average (Na+K)A values in the studied amphiboles are indicators for the alkalinity of the magma. The calculated average value for the amphibole cores in the gabbro is 0.13 and 0.11, for the rims. In the monzogabbro, monzonite and syenite the average (Na+K)A values are lower in the cores, i.e. they are indicative for the higher alkalinity in the later stages of crystallization.

Zoning in the amphiboles is also observed following the abundances of Si (a.p.f.u.). The average Si content in the amphibole cores from the gabbro is 7.11, from the monzonite - 7.23, and from the syenite - 7.82.

The studied amphiboles from Vitosha pluton fall into the field of plutons with high ¦O2 on the IVAl vs. Mg/(Mg + Fe) ratio diagram of Anderson and Smidt (1995) (Fig. 2).

Based on our studies on amphiboles from Vitosha pluton it was found that:

12. Mineralogical mapping and prognoses for mineral resources in the Pernik administrative district based on stream-sediment pan-concentrated sampling (O. Vitov)

The degree of covering of Pernik administrative district by stream-sediment pan-concentrated sampling was studied using the archival data of the National Geofund [57]. Because of gaps in the sampling grid a new sampling by use of additional 3000 stream-sediment samples is recommended (Fig. 1a). Using the available data a mineralogical dividing was made, which revealed a regular spatial arrangement of the complex heavy-mineral anomalies (Fig. 1b). The mineral diversity of the stream-sediment samples, expressed by the informational significance of the mineral composition, showed a linear heavy-mineral anomaly (Fig. 1c). These regularities were compared with the geological structure in the Pernik district (Fig. 1d) and interpreted as a new Trun-Radomir-Dren metallogenic stripe named "Radomir metallogenic zone", which is enriched in complex anomalies of gold, galena, cinnabar, scheelite and barite. Most deposits, occurrences and indications of gold and base metals as well as mercury occurrences fall within its boundaries. It is NW-SE-striked (135°) and marks the boundary between the Srednogorie, on one hand, and the Rila-Rhodopes area and the Kraishte, on the other.

Fig. 1. Stream-sediment sampling along the rivers and streams, and ore resources of Pernik district (a); stream-sediment anomalies of HgS, PbS and CaWO4 in Pernik district (b); Trun-Radomir-Dren stripe of highest mineral diversity (c); geological scheme of Pernik district (d).

13. Mineralogical mapping and prognosis for garnet deposits in Sakar Mt, SE Bulgaria (O. Vitov, N. Tsankova)

In connection with a prospecting for garnet deposits for abrasives, a mineralogical dividing of Sakar Mt was made and a prognosis for garnet deposits was compiled based on stream-sediment pan-concentrated archieve data [49]. The stream-sediment samples showed a strong correlation between the garnet, gold and galena.

The following rocks were sampled and a heavy-mineral concentrate was obtained from each of them: two-mica and muscovite schists near Orlov dol; magnetite- and garnet-containing schists near Hlyabovo village; garnet-staurolite two-mica schists near Oreshnik village; amphibolites near Planinovo village; a two-mica schists near Dervishka mogila village.

The mineral composition of the rock samples and the chemical composition of the collected garnets were examined. The garnets from monomineral fractions were studied by a goniometer and morphometrically (measurement of a, b, c axes).

Estimation of morphometric coefficients, statistical data processing and classification of garnet crystal forms were performed after Zingg by use of the GARNET program written for this study.

It is established that the studied garnets are of almandine type. The morphometric data show a relationship between the regional synmetamorphic deformation and the garnet crystal habit. The ductile deformed garnets (b2=ac) lay on the main diagonal on the Zingg diagram (Fig. 1), the tabular garnets - along the b/c=1 axis, and the elongated crystals - along the c/a=1 axis. The figurative points on the diagram within the field between both axes belong to deformed and elongated garnets. The relict garnet crystals fall in point a=b=c.

In conclusion, the detailed mineralogical examinations of garnets from Sakar Mt and the ascertained spatial regularities point to presence of economic almandine deposits, complex gold-almandine placers and metamorphic base-metal mineralizations.

Fig. 1. The studied garnets on the Zingg diagram.

14. The archaeomineralogy in Bulgaria conception and new evidence (Z. Tsintsov)

The last few archaeological seasons in our country showed increasing necessity of archaeometric data for archaeological interpretations of the metal raw materials extracted in ancient times on the Bulgarian territory. At this stage the Bulgarian mineralogical science has limited potential in that aspect and cannot answer adequately to these needs. The extension of the archaeometric database requires the organization of a certain mineralogical basis on which these studies to be developed and this is possible only with the methods of archaeomineralogy. The present work resumes the experience and the views of the author regarding the place and the role of the mineralogical studies for the needs of archaeology in our country. One objective of this work is to provoke discussions among the geological society in Bulgaria on the problems related to this type of studies and the necessity of separating them from the archaeometallurgical investigations and also their specifications as own scientific direction in archaeometry and in the Bulgarian science [46].

In 2005 a joint program between CLMC-BAS and AIM-BAS started, which includes investigation of the traces of ancient ore processing and metallurgy in the region of Gorata ridge in Eastern Rhodopes. Major problems to be clarified in a longer time period are: i) chronology of the ore mining and metallurgy in the region (main periods and their specificity); ii) types of metallurgy (ferrous and/or non-ferrous); iii) the raw materials used for this aim and the deposits; iv) features of the technological processes, which can be registered for the different periods. During interdisciplinary preliminary archaeomineralogical studies in the region of Vulche pole village, Haskovo district, it has been established that during the Iron epoch (X-I century B.C.) in these places ancient miners had mined iron ore and performed metallurgical processing on the same places. An indicator for that is the great amount of slag, found very close to a metallurgical furnace as well as in the placers in the region. For this purpose there were used placer iron-bearing pieces present in great quantity in the alluvial sediments of the region. The ore mineralization in them is mainly represented by Fe oxides/hydroxides including magnetite, hematite, maghemite, goethite and small amounts of sulfides (Fig. 1 a, b). The first two minerals display reversed dominating quantitative relations and determine the outlook and the features of the separate samples. The ancient iron mine is disposed in the region of the places Gaidata and Kutela (Fig. 1 c) [48].

Fig. 1. Morphological features of placer magnetite (a) and magnetite-hematite (b) pieces;
traces (refuses) from ancient placer iron-mining in the borders of ancient mine (c). Scale bar a-c 4 cm.

Preliminary archaeomineralogical studies on the sediments in the region of Gorno Uino village (Kyustendil district) and the preserved remnants found in them coming from ancient mining and processing of gold showed that the ancient galleries in the region of hamlets Kretsul and Zdravkova had been cut almost horizontally at the low part of the Paleogene conglomerates and followed the richest in gold parts. Their cross-sections have the form of semicircle and length of up to 10-12 m, height of about 1.50-1.60 m and width at the bottom of around 2.40 m. Their walls, although wavy, are dense and smooth. It seems that these works had most probably been used for prospecting purposes in order to appropriately direct the surface mining.

The position of the ancient gold mine is marked by huge piles of sorted boulders, which crop out to the north of Kretsul hamlet. The scale of the mining works had probably exceeded 10 millions m3 of earth mass. The ore dressing refuses from the processing equipments of the ancient miners had been deposited in the place Suho pole as an anthropogenic mass with a total volume of 8 millions m3. The content and the peculiarities of the native gold in these depositions show that the ancient miners conducted selective mining. The gold artifacts in the alluvial sediments of the region point out that a gold processing center had been operating close to the mine.

All these data explicitly indicate that in ancient times the region of GornoUino village had been inhabited by people, permanently engaged with mining and processing of gold. Traces of such activity are found elsewhere, which speak about one very big and well-organized mining-metallurgical complex. This huge and impressing, even in our days, heritage has preserved much information, which must be subjected to carefull reading and correct discussion [76].

15. Gold and civilization in Kjustendil district, Western Bulgaria (O. Vitov)

A comparison is performed between the spatial distribution of gold-containing stream-sediment pan-concentrated samples, known gold deposits, occurrences and indications, and historical monuments from ancient times up to now in the Kjustendil administrative district [80]. The historical data were taken from written sources, maps and investigations. After the comparison of all available data nine periods of arising, bloom and decline of gold mining and their representatives were defined: I Pre-Thracian period (Gurbino gold-mercury occurrence); II Thracian period (holes for gold in the flooding terrace in the vicinity of Treklyano village); III Thraco-Roman period (open and underground gold mines in the terraces of Struma and Dragovishtica rivers between Perivol and Shishkovci villages); IV The Middle ages period (gold mines in the Tertiary conglomerates in the vicinity of Uino village); V Ottomanian period (boulder heaps along the rivers drawn on the Russian topographic maps like Koprivska river in Vlahina planina Mt near Sreburnovci hamlet); VI Prospector period (concessions of Maksimov from Kjustendil town); VII - German period (open pit for optical calcite in Dvorishte village; graphite mine near Treklyano village and prospecting gallery for gold, copper and base metals in the vicinity of Boboshevo village); VIII Socialist period (gold deposits, occurrences and indications on the Ore map at 1:100 000 scale); IX Post-socialist period till now (private concessions for gold along Struma river at Konyavo, Kopilovci and Shishkovci villages).

A high degree of spatial coincidence between the areas of gold-containing stream-sediment pan-concentrated samples (Fig. 1a) and the places of historical monuments (funeral mounds, settlements, strongholds (Fig. 1b), churches, etc.) allows us to propose that the gold mining in the Kjustendil district has been a major factor for the development of civilization there: the periods of intensive gold mining coincide with the periods of bloom of the material culture in the Kjustendil district. The Thraco-Roman period left most significant traces of gold mining.

Fig. 1. Localization of the golden deposits, occurrences and indications in Kjustendil district (after Мазников, 1997) and frequences of the gold-containing stream-sediment pan-concentrated samples (Витов, 2005) (a); antique and post-antique strongholds and contemporary settlements (after Слокоска и др., 1972) (b).


II. ENVIROMENTAL MINERALOGY

16. Mineralogy, geochemistry and environmentally safety application of solid fuels and their combustion and pyrolysis products (S. Vassilev, Ch. Vassileva)

Bulgarian subbituminous (Pernik, Bobov Dol) and bituminous (Balkan) coals were gradually heated under air from 100°C to their fluid ash-fusion temperatures (1400-1600°C) via 100°C intervals and the behaviour of their inorganic matter (IM) was studied. The original minerals and newly formed inorganic phases in the oxidation and combustion products (OCPs) of these coals were identified and the behaviour of 33 minerals and phases was described. The coals studied reveal high detrital abundance and low authigenic mineralization with sulphide-sulphate, carbonate or mixed sulphide-sulphate and carbonate tendencies. The IM of coals is composed mainly of quartz, kaolinite, illite+muscovite, feldspars, pyrite, and calcite, while the other minerals identified have subordinate occurrence. The IM of OCPs includes various pre-existing minerals and newly formed phases. The latter phases are glass, quartz-cristobalite-tridymite, mullite, amorphous clay material, hematite-magnetite, anhydrite, and others originating from the heating of these coals or during storage of their OCPs. The physico-chemical processes and temperatures that result in the formation of new phases in OCPs are described. The relationships between the ash-fusion behaviour and chemical and mineral composition of the coals are also discussed. A systematization of the physico-chemical transformations and some comparative characterizations, as well as prediction of certain technological and environmental problems related to the behaviour of IM during heating of Bulgarian lignites (Maritza East, Maritza West, Sofia), subbituminous and bituminous coals are also described and summarized [55].

The mass balance of 57 major, minor and trace elements in two group boilers, namely Units B1-4 and Units B5-6, at the Soma thermo-electric power station (TPS) was calculated by two methods. It was found that S, Ta, Hg, Se, Zn, Na, and Ca in Units B1-4, and Hg, S, Ta, Se, P in Units B5-6, have volatile behaviour during coal combustion in this TPS. It was also identified that Sb and Tb in Units B1-4 and Sb in the Units B5-6 have relatively high retention effects in the combustion residues from the Soma TPS [17].

The extractable contents of Ca, Cr, Cu, Fe, Mg, Mn, Ni, Pb, and Zn were determined using a six-stage sequential leaching procedure and different solvents to isolate: (1) water-soluble; (2) slightly changed organic matter; (3) carbonate; (4) Fe-Mn oxides; (5) glass and silicates; and (6) char fractions of Bobov Dol fly ash (FA) and ceramic cenospheres (CCs) recovered from this FA. The leaching behaviour and modes of occurrence of the above-listed elements in FA and CCs are discussed. The preliminary results show that this improved sequential leaching procedure applied on well chemically and mineralogically characterized products is promising and could be successfully used [53, 54].

A summary on the mineralogy and geochemistry of various coals worldwide is reported and both basic and applied aspects are recognized [52]. The fundamental aspects include: (1) mineralogical and geochemical characterization; (2) determination of contents, migration, enrichment/depletion trends, and distribution and modes of occurrence of elements, minerals, and phases; (3) elucidation of genetic features of minerals and inorganic phases; and (4) characterization of economically valuable and/or environmentally hazardous components in the coals studied. The applied aspects include determination, prediction, and reduction of some technological and environmental problems related to coal utilization.

A new approach for the classification system of coal FAs based on their origin, phase-mineral and chemical composition, properties, and behaviour is introduced and evaluated [78]. Detailed data for 41 FAs produced from various feed coals at 37 coal-fired TPSs in Spain, Bulgaria, The Netherlands, Italy, Turkey, and Greece were used for that purpose. The chemical FA classification system was organized according to the contents, common geochemical associations, and significant positive or negative correlations of ash-forming elements in FAs using three end members, namely: (1) sum of Si, Al, K, Ti and P oxides; (2) sum of Ca, Mg, S, Na and Mn oxides; and (3) Fe oxide. This approach specified 4 chemical FA types (Sialic, Calsialic, Ferrisialic, and Ferricalsialic) with three dominant tendencies - high acid, medium acid, and low acid. The most important phase-mineral FA classification system was organized according to the contents, associations, correlations, properties, and behaviour of species in FAs using also three end members, namely: (1) glass; (2) quartz+mullite; and (3) other minerals. This approach specified 4 phase-mineral FA types (Pozzolanic, Inert, Active, and Mixed) with three dominant tendencies - high pozzolanic, medium pozzolanic, and low pozzolanic. The divided chemical and phase-mineral FA types and subtypes were characterized and the relationships and distinctions between them were also described. It was found that characteristics such as: (1) feed coal and combustion technology used in TPS; (2) water-soluble, magnetic and heavy fractions, pH, fluid ash-fusion temperature, detrital/authigenic index, and BET specific surface area of FAs; and especially (3) content, modes of occurrence, and distribution of glass, quartz, mullite, lime-portlandite, periclase-brucite, Ca sulphates, Ca and Ca-Mg silicates, magnetite-hematite, and char types in FAs, give the most valuable information for the determination of potential utilization directions and environmental concerns of FAs.


17. Project: Mercury pollutions and mercury mineralizations in Bulgaria (O. Vitov, I. Marinova, I. Dimitrov)

Mercury is a highly toxic element and according to the published data its content in the Earth's atmosphere is 30% more than the normal values. Numerous projects of the United Nations, European Community, and USA monitor the mercury emissions in the atmosphere and prepare requirements for their diminishing. The work performed on these projects clarified the modes of occurrences of mercury in the atmosphere, the major industrial productionspolluters and the quantity of mercury emitted from different countries. These investigations revealed also high variations of the mercury content in the atmosphere for periods of 24 hours, one hour, and a minute as well as the considerable mercury variations in the atmosphere in height and along profiles on the Earth's surface.

Bulgaria belongs to the Mediterranean global mercury belt and its lithosphere is enriched in Hg. As a consequence, a lot of stream-sediment samples taken from alluvial sediments in the country contain cinnabar (HgS) (Ann. Rep. No 11/2005). Additionally, there are published data that show the presence of Hg in the Bulgarian ferrous and non-ferrous metal ores and in the emissions coming from coal and petroleum combustion, as well as from the cement, pigment and iron, caustic soda and chlorine productions, and roasting of non-ferrous ores and also from domestic wastes.

Till now in Bulgaria there are no systematic ecological investigations on the mercury spread in the environment and, thus, the realization of a scientific project "Mercury pollutions and mercury mineralizations in Bulgaria" is of significant importance.

A first step in this direction is the proper choice of the objects of study, to outline the mercury pollutions, and to compile respective models of mercury migration in the environment. These objects should be well studied in geological aspect. Kjustendil district (Western Bulgaria) is one possibility for realization of such studies as this is a region where cinnabar displays high concentrations in stream-sediment samples and numerous cinnabar mineralizations are found (Ann. Rep. No 11/2005). Two natural and two anthropogenic sources of mercury emissions are planned to be investigated, respectively: the cinnabar occurrence in Ushi Mt, near Treklyano village, and the mercury-gold occurrence at Gurbino village as well as the dung-hill of Kjustendil town and the brick-producing plant in the village of Dragovishtitsa.

The model objects shall be studied by geological, litho-chemical and hydrochemical surveys and a possibility for remote determination of mercury contents in the air will be looked for. The results of these explorations will help in preparing a model for the mercury spread in the air above the surface. This model will be a background for further monitoring of the mercury emissions and control of the risk for mercury pollutions [58].


18. Ecological and economic aspects of the barrages and barrage systems in Bulgaria (O. Vitov, V. Nikolov)

Study of the processes of formation of stream sediments and their transport in an alluvial medium showed that these processes stopped after the building of dams across the rivers and of barrages and barrage systems across their streams [60].

Recognizing the significance of barrages as facilities that prevent soil from erosion and protect against floodings (Fig. 1), it is established that barrages influence the development of the relief as they create new local erosion systems, cause salting of soil, and change the microclimate by rising the temperature of the ambient air. The barrages also stop the natural transport of forest soil toward the plains and as a result the plain soil looses its fertility.

Fig. 1. Erosion of soil (a) and a standard barrage across Palakaria river near Yarlovo village (b).
Water flowing out of the barrage in summer is mineralized. The barrage constantly drains the soil and,
thus, dries the river valley.

The formation of local erosion bases after filling up the barrages creates a new erosion cycle in their drainage system with a consequent activation of gullies and landslides.

For overcoming the negative effects of barrages a periodic disloading of the accumulated sediments from the barrages is proposed. The gained soil, inert materials and heavy minerals like gold, zircon, monazite, magnetite, etc. are valuable resources and should be controlled by the state institutions. As a summary it may be stated that new geological, ecological and economic studies of the barrages and barrage systems in Bulgaria have to be curried out.


19. Tuzlites a new type of coast protection facility (O. Vitov, V. Nikolov)

Study on the processes leading to formation of sand at the Black Sea shore (the zone of bench) showed a specific natural underwater relief grooves parallel to the coast, which are filled with spherical stone pieces [59]. These stone spheres named "tuzlites" after the place of their first finding ("Tuzlata" is a place near Balchik town) are a result of mechanism of transformation of the wave energy into energy of rotation of stones up to their gradual wearing and formation of sand. During this process the coast is protected until the stones spheres do not fully wear out (Fig. 1, 2).

Fig. 1. Mechanism of coast protection using tuzlites that fill grooves of soft rock parallel to the coast line and situated in grooves formed from rock plates pulled down from the sea-shore: a) lifting of tuzlites when a wave moves toward the coast; b) revolving of tuzlites when a wave moves toward the sea. At this mechanism a drop of water level is created due to the delay induced by the curtain of revolving tuzlites and as a result the next waves destroy themselves far away from the coast and, thus, protecting it.

Fig. 2. Perfectly rounded tuzlites from natural grooves (left) and a scheme of their formation (right).

A new type of coast protection is proposed on the basis of the mechanism of formation of tuzlites. It includes making of grooves of partly overlapping concrete panels on the sea bottom and periodic filling of the grooves with stone pieces.


III. MODELING AND MODIFICATION OF MINERAL SYSTEMS

20. Geometrization of the language of mineralogy (V. Penev, N. Zidarov, B. Zidarova)

In preceding Annual reports (see Ann. Rep. NoNo 3/1997; 5/1999; 7/2001) a conceptual scheme was proposed for constructing of entirely mathematical spatial representations of arbitrary chemical (incl. mineral) structures [73]. According to this scheme, the mathematical representation of each chemical or mineralogical structure is being constructed through defining the corresponding particular distribution (with respect to a previously chosen coordinate system KE(3) in the physical space VE(3)) of the chemical charges forming this structure. On the other hand, the notion chemical charge is introduced into the space of chemical structures VS(6) (see Ann. rep. 3/1997) through specifying a strictly defined noninvertible image of the physical space VE(3) onto Mendeleev's space VM(3). This image is being constructed using the following two rules (see http://www.acadjournal.com/2004/v11/part2/p3/):

1. To each point in VE(3), in which some simple chemical object exists, one juxtaposes the mathematical image of this species of simple chemical objects in VM(3) obtained via either of the two generalized spatial mathematical models or   (see http://www.acadjournal.com/2000/v2/part2/p3/).

2. To each point in VE(3), in which there is no simple chemical object, one juxtaposes the natural zero point of VM(3).

These two rules have a simple qualitative meaning, namely they provide the unique procedure for assigning an exactly specified chemical charge to each point of VE(3). By the notion chemical charge we mean the species of the corresponding simple chemical object occupying this point at a given moment.

On the other hand, by specifying the distribution of a given kind of charges in a space, one in fact defines in this space a field of an exactly specified kind.

It becomes clear from the aforesaid that with constructing an entirely mathematical representation of chemical and mineralogical objects one defines in fact of the specific configuration (distribution) of the field of chemical charge in the corresponding volume of VE(3). In other words, by introducing the notion of chemical charge and by formulating the rules for specifying this type of a charge in VE(3), one has introduced in the language of mineralogy both the fundamental idea for a field, and a number of related basic formal-science notions.

It is clear from the aforesaid that the descriptive mineralogy investigates, describes and classifies the diverse possible configuration of the chemical field.

As an example for an entirely mathematical representation of a given mineral structure through defining the corresponding configuration (distribution) of the field of chemical charge, Table 1 presents the distribution of this field in the volume of a unit cell for the mineral cuprite.


21. Thermotribochemical treatment of low-grade natural phosphates (Y. Pelovski, V. Petkova, I. Dombalov)

This study concerns results on the stability of mixed mineral fertilizers processed by effective mixing and compaction, using extrusion technology [105]. Being new products, it is necessary for these fertilizers to study the possible changes in the phase ratios and caking processes during long term storage. Seven samples with different nutrient components ratios are investigated after a year staying in a storage facility without conditioning. Thermal effects and weight losses, type of crystal structures and phase content in the samples were studied by TG-DTA (results shown in Fig. 1), scanning electron microscopy and X-Ray diffraction methods. Based on the results obtained, the relationships are discussed and conclusions made about the possibility to safety storage and application of the new products as fertilizers in the agriculture for nutrition of different plants. It is confirmed that the investigated samples, produced on the basis of low-grade phosphates are stable during long term storage and they could be successfully recommended for a. practical use in agriculture, using traditional or individual methods of fertilization.

Fig.1. TG-DTG-DTA curves of the samples studied


22. Design of technology for extraction of gold from copper ores (I. Donchev, E Tarassova, O. Petrov, Y. Tzvetanova, V. Stoilov)

The project for realization of this task was worked out in collaboration with "Asarel-Medet" JSCo and "Niproruda" JSCo. This project was partly financially supported by the Executive Agency for Encouragement of Small and Medium Enterprises (EAESME) and aims at obtaining of additional production at "Asarel-Medet" JSCo evaluated at about USD 5 000 000. Two of the five planned 6-month stages were fulfilled up to the end of 2006. As a partner, the Central Laboratory of Mineralogy and Crystallography performs mineralogical-technological investigations of the ore materials and the products of their dressing.

The first stage included sampling of Asarel mine according to the requirements specified in the project and the rules for topomineralogical mapping. The samples are representative for the respective blocks and horizons of the mine and meet the requirements of the project for Au contents, mineralogical composition and ore structures and textures. During the period of technological investigations in Ore Dressing Plant (ODP) "Asarel" preliminary studies were performed on the sand from the gravitational concentrate coming from the hydro-cyclones and the throats of the mills. The intergrowth mechanisms of the copper minerals with pyrite and rock-forming minerals were studied in more than 300 microscopic preparations and under the microscope several gold grains sized about 30-40 mm were observed. Electron microprobe analysis on these grains proved the presence of silver in the range 8 to 12 wt.%.

Fig. 1. Size distribution of gold
in the gravitational concentrate

During the second stage the activity was concentrated on detailed mineralogical studies of gold in the heavy fractions of the sands coming from hydro-cyclones during processing of intermediate products of ODP "Asarel". It was found that the gold grains are characterized by diverse morphology and size in the range from 60 to 80 mm (Fig. 1). Prevailing are gold grains with admixtures (Ag, Cu, and Fe) not exceeding 8-10 wt.% and presence of electrum was not registered in a series of more than 30 gold wafers. More than 120 gold particles were observed in the heavy fractions obtained on a concentration table and for the majority of them microphotographs were prepared. The final product of these studies is the report "Atlas of gold in the heavy fractions of intermediate products ODP-Asarel".


23. Experimental investigation and mathematical modelling of non-stationary mass-transport in basaltic melts subjected to external electric field (J. Mouchovski, M. Tarassov, N. Zidarov, Tz. Sapundjiev)

The multi-component character of magmas determines the complexity of ionic motion during gradual cooling that affects their differentiation and mineral crystallization. In preceding reports (Annual Rep. NoNo 6/2000-11/2005), hypotheses for an ion-migration induced by thermo-electromotive force and acting together with chemical and thermal diffusion within the boundary layers of magmatic melts, was checked up by performing a series of laboratory experiments to investigate the transition from a non-stationary to stationary ionic motion in basaltic melts in a constant dc electric field. The experiments were carried out at ambient pressure using mainly a rectangular parallelepiped electrochemical cell.

The present report concerns only experiments carried out in air at a pressure of 1 bar and using an electrochemical cell with axial symmetry of the electrical field between two platinum electrodes, whose configuration (thin wire as cathode, and crucible wall as anode) assured a cathode-type cell polarization. Controlled are: the melt temperature Tmelt, the applied external voltage, the total current through the cell, and the degree of cell polarization. The model of one-dimensional mass-transport in cylindrical coordinates is used for describing an isothermal ionic motion involving two new terms in the differential equation. In this way, one accounts for the simultaneous action of the chemical diffusion, ion-migration, the electro-reduction driven Stefan's flow, rate-determining the reactions limitations, and the stationary part of the current. The partial differential equation is used for solving the inversed problem, namely the iterative determination of optimal values of the adjusted, non-fixed parameters such as the mole fraction and the number of exchange electrons on the cathode surface, and the effective diffusion coefficient for a given ionic species.

To solve this problem we used a system of ordinary differential equations by a powerful software simulator (20-STM 3.4 Controllab Products B.V. Enshete, The Netherland).

The model of ionic transport was applied within a relatively wide range of Tmelt (13691614 K), as the numbers of data points for the total current vs. time dependence are sufficiently large to attain a quasi-equilibrium state.

The starting current (at t = 0) rises monotonically up by more than an order of magnitude for the explored temperature range (Fig. 1), a fact correlating with the increase of the ion-mobility, and in accordance with Nernst-Einstein's equation. After a very fast current decrease during the first 200 s, the steepness of the curves sharply reduces, thus indicating a rapid diminishing of the ratio between the non-stationary and stationary current throughout the cell. Hence, the curves section after t » 200 s is supposed to be controlled basically by the stationary part of the current. At the same time, the curves reveal a series of local maximums and minimums that can be explained by variations in the cell polarization due to the different rate of proceeding electrochemical and chemical reactions. The curves corresponding to the three lowest temperatures (within 1369 and 1430 K) occur in Fig. 1 in an inversed order and without any extremes at t>200 s. These temperatures belong either to a glass transition for the studied basalts (1230-1420 K) or lie slightly above this range. These phenomena could be explained by the existence of two different competitive mass-transport mechanisms acting within and near to the glass transition.

Fig. 1. Non-stationary current through basaltic melt in electrochemical cell with an axial symmetry of the electrical field at constant temperature, varied from 1369 to 1614 K, and at constant external voltage: (1010 ± 7) mV. B 1369 K, D 1397 K, F 1430 K, H 1460 K, J 1498 K, L 1528 K, N 1557 K, P 1585 K, R 1614 K. The legend shows the initial and the average (in brackets) values for the current in miliampers at different temperatures. Fig. 2. Simulation curve for experimental total current vs. time dependence at 1456+2 K and under external voltage of 1012±8 mV. Fixed parameters: melt temperature, Fe-mole fraction in melt bulk (XFeo = 0,091), and Fe-transferring number (tFe = 0.94). Fitting parameters: Fe-mole fraction XFecath = 0.0899 and number of exchange Fe-electrons ZFe =2.944 on the cathode surface, and Fe-effective diffusion coefficient DFe = 5.22x10-9 cm2/s.

The model is verified for the motion of Fe since its ions exist in two and three valence states in the magmas and may act as network-formers and network modifiers. Besides, the ratio between the two Fe-states defines the degree of melt polymerization, which, in its turns, determines the melt properties such as viscosity, specific electrical conductivity, density, and expansivity. The application of the simulator for a chosen temperature (Fig. 2) gives a fitted curve with a very high correlation coefficient and low statistical error. Besides, the values of the fitting parameters (XFecath, ZFe, and DFe) appear to be physically reliable, being close to those found by us for electrolysis in electrochemical cells with a rectangular cross section. At this case, the used simulator proves to be a powerful tool for further investigation of the ionic motion in any alumosilicate liquids by using appropriate models.


IV. SYNTHESIS, COMPOSITION, STRUCTURE, AND PROPERTIES OF MINERALS AND NEW MATERIALS

24. Hydrothermal synthesis of microporous titanosilicates (V. Kostov-Kytin, S. Ferdov, B. Mihailova, Yu. Kalvachev, O. Petrov)

Microporous titanosilicates are closely related to natural and synthetic zeolites and draw lately interest to various applications. Natural occurrences are mostly localized to the postmagmatic derivatives of peralkaline rocks and more than 100 of these mineral species have already been reported. These are zeolite-like compounds whose frameworks are built of tetrahedral (Si) fragments and transition elements (mainly Ti, but also Nb and Zr) with 6-fold and, rarely, with 5-fold coordination. Microporous titanosilicates often occur together in a large family of heterophyllosilicate minerals that contain the same set of major cations. Materials of these types are promising as ion exchangers, sorbents, catalysts or catalyst carriers. In recent years, suchlike phases, both with and without mineral analogues, have been prepared using various synthesis techniques, yet, their number is still smaller than that provided by Nature.

Aiming at further optimization of the synthesis conditions for preparation of titanosilicates with desired pore systems and functionality, we have explored the system Na2O-K2O-TiO2-SiO 2-H2O. Here, we present results concerning the role of certain physicochemical parameters on the crystal type, size, morphology, and orientation of the run-products [91].

Detailed synthesis studies were carried out in the system aNa2O-bK2O-cTiO2-10SiO 2-675H2O, where 0ЈaЈ9, 0ЈbЈ9, a+b=9, 0.3ЈcЈ3.3 at temperature of 200°C, crystallization time 24 h and autogenous pressure. The reactants used were: SiO2 (Merck), TiCl4 (Fluka), NaOH (Merck), KOH (Merck), and distilled water, without using organics as templates. The precursor gels were prepared by mixing the silicate alkaline aqueous solution with hydrolyzed TiCl4 and transferred then into 10 ml Teflon-lined autoclaves. In addition, kinetic investigations were carried out in the system aNa2O-bTiO2-10SiO2 -675H2O, with 3ЈaЈ40, 1ЈbЈ6 and synthesis duration varied between 16 and 240 h.

The phase identification and characterization were performed by powder X-ray diffraction analysis. SEM was used to examine the morphology, size and orientation of the run-products. Infrared, Raman and 29Si MAS NMR spectroscopic methods were applied to analyze the relationship between the chemical compositions of the initial synthesis gels and the favored crystalline titanosilicate phases formed upon hydrothermal treatment.

Nine pure crystalline titanosilicate phases were synthesized under the above-described conditions, namely microporous ETS-10, ETS-4 (zorite), STS (Ti analogue of the mineral umbite), GTS-1 and synthetic sitinacite, layered AM-1 and AM-2 (Rocha and Anderson, 2000), and two dense titanosilicates, analogous to the minerals natisite and paranatisite.

The role of the exchangeable cations as structure-directing agents is evidenced through the formation of AM-1 instead of ETS-10 and of ETS-4 instead of STS when K is replaced by Na in the potassium-free system.

The crystal size and morphology of the run-products within the crystallization field of STS are strongly influenced by the TiO2 content in the initial gel as illustrated on Fig. 1. Increasing its value promotes transition from formation of large single crystals through intergrowths with a decreasing size and degree of orientation of the building crystallites to spherical aggregates composed of microcrystallites.

Fig. 1. Micrographs of STS crystals and aggregates synthesized hydrothermally for 24 h
in the system 2Na2O-7K2O-xTiO2-10SiO 2-675H2O, where: a) x=0.3, bar length 10 mm;
b) x=0.6, bar length 100 mm; c) x=0.9, bar length 10 mm; d) x=1.2, bar length 10 mm;
e) x=1.5, bar length 10 mm; f) x=1.8, bar length 10 mm.

In the potassium free system, the initial Na2O/TiO2 ratio specifies the pH of the reaction medium in the range 12-13. It is found that lower Na2O/TiO2 values favor the formation of layered and microporous materials, whereas at higher values titanosilicates with dense structures crystallize, preferentially. The kinetic investigations well confirmed the validity of Ostwald's rule of successive phase transformations leading to the appearance of more thermodynamically stable products in the following sequence: AM-1 - ETS-4 - GTS-1 - AM-4 - sitinacite - paranatisite - natisite, i.e., from microporous and layered titanosilicates with a low Ti content up to dense and with high Ti content phases. The fact that the framework-topology type and phase morphology are quite sensitive to the reaction medium variations allows precise tuning in the preparation of titanosilicates with tailored pore systems and functionality.

It is concluded that to increase the structural diversity of synthetic heterosilicates with useful properties it is necessary to vary the composition of framework and extraframework cations as well as to work in somewhat milder conditions concerning the pH and the temperature of the reaction medium.


25. Synthesis of nanosized TiO2 particles on activated carbon (L. Ljutzkanov, I. Stambolova, V. Blaskov, S.Vassilev, V. Petkova, D. Mehandjiev)

Nanosized TiO2 particles loaded on activated carbon were successfully obtained by an original method of pyrolysis in a stream of exhaust gas and water vapor at two different temperatures [92].

XRD analysis indicates that the powders obtained at a temperature of 680oC consist of three phases: anatase, Ti2O3 and Ti4O7, while the calcination at 830oC leads to a change in the phase composition - rutile, anatase and Ti2O3.The size of the crystallites was evaluated by the Scherrer formula and was found in the range 10-40 nm.

The samples were characterized by XRD and DTA/TGA and the obtained data are shown in Fig 1. In addition, adsorption-desorption isotherms and specific surface area and pore size distribution were measured. It was found that TiO2 on the activated carbon composites prepared at 680oC has possess a relatively high specific surface area of 480 m2/g and a total pore volume of 0,4 cm3/g. Both samples contain micropores and mesopores.

Fig. 1. DTA and TG of TiO2 /AC


26. Photoactive optically transparent titania nanoparticles incorporated in thin layers (V. Stengl, S. Bakardjieva, V. Kostov-Kytin, Y. Kalvachev)

Nanosized particles of titanium dioxide exhibiting a quantum size effect are investigated [110], their physico-chemical properties being depended on the particle dimensions. Compared to macroscopic TiO2 powder materials for these particles a blue shift in the absorption spectra is observed due to broadening of the bandgap. Their aqueous dispersion does not practically scatter light. The synthesis of transparent colloidal solutions of extremely small titanium dioxide particles in water or ethanol by hydrolysis of TiCl4 or of nanometer sized Q-TiO2 particles, prepared by a sol-gel method, is presented. Detailed kinetic study of the photocatalytic degradation of diuron in aqueous colloidal solutions of Q-TiO2 particles, prepared by hydrolysis of TiCl4, is reported. The optically transparent nanoparticles of titanium dioxide have been prepared by hydrolysis of titanium (III) chloride in the presence of polyethylene glycol. Anatase or brookite nanoparticles are formed depending on to the molecular mass of polyethylene glycol. The transparent nanoparticles of rutile modification were prepared by hydrolysis of aqueous solution of titanium (III) chloride in the presence of hydroxyethyl methacrylate. Optically transparent titania nanoparticles doped with nanoparticles of Pd and Ag were prepared and deposited as thin layers on a quartz tube to be used as a photocatalyst for the mineralization of organic pollutants. The measurement of the photocatalytic activity of thin layers of poly-hydroxyethyl metacrylate, determined by degradation of Orange II dye under UV radiation, demonstrated excelent photocatalytic properties of these materials.

Fig. 1. HRTEM micrograph, SAED pattern and photocatalytic activity of optically transparent titania

27. Crystal structure and crystal habit types of nanostructured TiO2 thin films a TEM investigation (V. Dimov, B. Kostova,I. Piroeva)

Two samples of 40 nm thick TiO2 films, subjected to a temperature treatment (350oC for 60 min) followed by two types of temperature annealing - 600oC for 60 min in O2 (lower temperature annealing) and 850oC for 15 min in O2 (higher temperature annealing), were investigated by transmission electron microscope (TEM) [79].

The lower temperature annealing sample is composed of nanocrystallites with maximum dimensions of 40 nm, as well as smaller grains (approximately up to 20 nm). The higher temperature annealing sample shows an uneven morphological structure. The films are composed of nanocrystallites, and the crystals size increases with the annealing temperature.

The selected area electron-diffraction polycrystal images with well-defined diffraction rings maxima identified both TiO2 thin films as anatase with a high degree of polycrystallinity.

A convergent beam electron diffraction imaging along the direction [331] of anatase from the 60 nm crystals was obtained. The [331] direction is almost perpendicular to the crystal face (112), corresponding to the {hhl} (Fig. 1). The 4060 nm individual anatase crystals from the two samples, most of them with a hexagonal shape, show different habits of the observed face (112).

Fig. 1. Anatase habit

Fig. 2 presents the three hexagonal habit types of {112} observed in the lower temperature annealed film: that of equally grown face's edges, typical of the regular surfaces {100} and {hhl} (Fig. 2a); that of a missing edge of (112) face due to either (100) or {hhl} faces being undeveloped (Fig. 2b); that of the differently sized face edges, formed due to diverse velocity of growth along (100) and {hhl} as well as to the irregular shape of the edges, because of simultaneous crystal growth (Fig. 2c).

Fig. 2. Single anatase crystals from the lower temperature annealing thin film.

The same peculiarities were observed for the sample annealed at the higher temperature and, in addition, another anatase habit type was found. Fig. 3a shows an unusually shaped anatase crystal with rhombohedral habit. Actually, we observed two instead of one face of {hhl}, which is the only face developed for this crystal.

Fig. 3. Single anatase crystals from the higher temperature annealing thin film.

According to the diverse diffraction contrast of the bright-field image, the coarse anatase crystals are thicker and their Moire sets, shown in Fig. 3b and 3c, indicate overlaying of two differently orientated equivalent structures. Consequently, the single crystals, exhibiting a higher diffraction contrast, were grown onto the thin polycrystalline film.

We have proved the existence of a polycrystalline anatase structure in both thin TiO2 films. The face morphology of anatase crystals as well as their size for the two samples studied is different due to the various annealing temperatures.

The lower temperature and the longer duration of crystallization determine the availability of anatase forms with faces of approximately equal growth rates. Therefore, the {112} from the lower-temperature thin film are of an almost hexagonal form. The {112} from the higher-temperature thin film exhibit two different habits representing two stages of the anatase crystallization. The dipyramidal crystal habit defines the first stage, ending earlier. The irregular hexagonal {112}-face habit determines the end of TiO2 crystallization.


28. Transformation of brookite-type TiO2 nanocrystals to rutile: correlation between microstructure and photoactivity (S. Bakardjieva, N. Petrova)

Investigations on the transformation of brookite-type nanocrystals to rutile, reported in Ann. Rep. No 11/2005, were summarized [2]. Nanometric particles of pure brookite TiO2 were synthesized by modified thermolysis of reactant solutions containing titania powder, HCl and urea. Unique flower-like brookite agglomerates with an average diameter of 400450 nm composed of single brookite nanocrystals of 45 nm were obtained at 105oC. The brookite-rutile transformation has been studied and TiO2 mixtures with variable amount of anatase, brookite and rutile polymorphs at different temperatures (from 200 to 800oC) were obtained. High resolution transmission electron microscopy (HRTEM), electron diffraction and BET/BJH analyses were used to characterize the phase assemblages, crystallite size and pore volume of the brookite and TiO2 mixtures. In order to understand the metastablestable TiO2 phase transformation, X-ray powder diffraction (XRD) was performed. The photoactivity of the brookite and TiO2 powders with different compositions of the brookiteanataserutile and anataserutile polymorphs obtained during the transitions was examined by photocatalyzed degradation of 4-chlorphenols in aqueous solution. The titania sample with the highest catalytic activity was obtained at 500oC. It contains 3.2% brookite, 42.9% anatase and 53.9% rutile and is referred to be TiO[B]/500 (Fig. 1).

Fig. 1. High resolution transmission electron micrographs of sample TiO[B]/500 obtained at 500oC:
a) and b) are at low magnification; c) and d) are at high magnification


29. Local structure of relaxor-ferroelectric Pb0.78Ba0.22Sc0.5Ta 0.5O3 (B. Mihailova, L. Konstantinov, O. Petrov, M. Tarassov)

The structure of the newly-synthesized relaxor ferroelectric with chemical formula Pb0.78Ba0.22Sc0.5Ta 0.5O3 (PBST) was studied by X-ray diffraction and Raman spectroscopy [28]. The structure of this compound is of double-perovskite type with a face-centred cubic symmetry at room temperature. The frequency dependence of the dielectric constant of PBST shows a strong dielectric dispersion in a wide temperature range and a dielectric-constant maximum near 200 K at 10 kHz. The analysis of polarized Raman spectra shows that the incorporation of Ba deforms the BO6 octahedra adjoining the BaO12-polyhedra along the [111] direction and shortens the Pb-O bond lengths next to the BaO12-polyhedra within the 111 planes. The random substitution of Ba for Pb leads to a wider distribution in the size and shape of the ferroic species in PBST as compared to stoichiometric PbSc0.5Ta0.5O3. The addition of Ba shifts the optical absorption edge to lower energies and gives rise to extra absorption peaks at 460 nm and 730 nm. The latter peak is related to polar atomic rearrangement in the vicinity of the Ba ions embedded into the PbSc0.5Ta0.5O3 matrix.


30. Organic crystals with potential optical activity (R. Petrova, B. Shivachev)

The present investigation aimes at the synthesis and the structural modeling of new organic materials with nonlinear optical (NLO) properties. The noncentrosymmetrical arrangement of the atoms in the stucture is one of the required peculiarities. Compounds containing squarate (Sq) and L-tartrate fragments crystallize noncentrosymmetrically and are suitable for NLO applications, especially for second harmonic generation. The interaction and the subsequent noncentrosymmetrical crystallization of these compounds with different "guest" molecules is a new trend in the molecular engineering of new materials with bulk NLO properties. Attempts to co-crystallize guanidines- with both squarate- and tartrate-derivatives resulted in the formation of new crystal phases. Crystals suitable for X-ray diffraction were obtained for two of these phases namely 4-phenylpyridinium hydrogentartarate dihydrate (C11H10N, C4H5O6, 2(H2O)) (Fig. 1) and aminoguanidinium hydrogentartarate monohydrate (C4H5O6, CH7N4, H2O) (Fig. 2). The crystal structure determination showed that both compounds crystallize noncentrosymmetrically, and that cations and anions take part in the formation of extensive hydrogen bonding.

Fig. 1. 4-phenylpyridinium hydrogentartarate dihydrate Fig. 2. Aminoguanidinium hydrogentartarate monohydrate


31. Crystal structures of spirohydantoin derivatives and biologically active compounds (R. Petrova, B. Shivachev)

Continuing our preceding structural studies on cycloalkanespirohydantoin, б-aminophosphonic acids and codeine derivatives, the crystal structures of several new compounds were determined.

Cycloalkanespirohydantoins are a subject of extensive investigations due to their biological properties, especially those acting on suppressing central nervous system tremors, б-aminophosphonic acids possess herbicidal, anticancer, antibacterial and antiviral activities, while the transformation of morphine derivatives into different metabolites is a matter of practical interest for detecting opiates in blood or urine.

In the course of our work we determined the crystal structure of the following compounds: 3'-aminocyclohexanespiro-5'-hydantoin-phenylboronic acid (1/1) [38] (Fig. 1), Codeinone 4,5б-epoxy-3-methoxy-17-methyl-morphin-7-en-6-one [18] (Fig. 2), and [(4,4-Dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]phosphonic acid [45] (Fig. 3).

Fig. 1.

 Fig. 2.
Fig. 3.


32. Conformation and structure of 4-substituted 3-furyl-2-phenethyl-tetrahydroisoquinolinon (K. Kossev)

One has continued proceeding studies on the conformational and structural peculiarities of 3-furyl-2-phenyl isoquinolinons. The effect of conformation on their 1H and 13C NMR spectra has been discussed. The structure of 3-(2-Furyl)-2-phenethyl-4-(pyrrolidin-1-ylcarbonyl)-3,4-dihydroisoquinolin-1(2 H)-one has been determined. The dependence of the conformational berriers on the isomers structure and their spectral characteristics has been simulated. The effect of weak and non-valence interactions on the population of the conformational isomer levels in solution and in solid state has been also discussed [40].


33. Thermal and structural investigation of hydrotalcite phases and their transformation (N. Petrova, R. Petrova, B. Shivachev, D. Kostadinova, Ts. Stanimirova)

Layered double hydroxides (LDHs) of hydrotalcite-like structure have potential applications as anion exchangers, catalysts or catalyst supporters and recently, as drug reservoirs in medicine.

In order to obtain biologically active materials we concentrated ourselves on squaric acid, H2C4O4 (H2Sq) derivatives, as guest anions in the LDH structure. The hydrogensquarate, HC4O4 (HSq), and squarate, C4O42 (Sq) anions are able simultaneously to be donors and acceptors of hydrogen bonds and thus form bonds with various biologically active organic molecules. MgO, гAl2O3 , NaHC4O4H2O and Na2C4O43H2 O were used as initial reagents to obtain Mg-Al-HSqLDH and Mg-Al-SqLDH by a hydrothermal method. An initial study of the structural, crystal-chemical and thermal peculiarities of LDHs intercalated with Sq- and HSq-anions were performed using XRD, IR-spectroscopy, and DTA-TG methods. The XRD patterns of both samples are typical of the LDH structure as the reflections can be indexed in terms of a hexagonal lattice with R3m rhombohedral symmetry. The influence of the two geometrically similar differently charged Sq ions onto the LDH structure was clarified: a perpendicular intercalation for HSq (d003 of 10.5Е), and a horizontal one - for Sq2 (d003 of 7.6Е). The presence of both squarate anions into the LDH structure was confirmed during the thermal decomposition in air atmosphere one observes an effect of combustion of the organic component on the DTA curves at about 450oC. The observed three bands in the IR spectra at 1614 cm1, 1516 cm1 and 1365 cm1 are assigned to the vibration of Sq anions.

In this study we determined the structure of NaHC4O4H2O using a single-crystal diffractometer [34] the Na atom is coordinated by six oxygen atoms, four from hydrogensqurate anions and two from water molecules. The three-dimensional packing is stabilized by a system of hydrogen bonds (Fig. 1). The presence of one water molecule and its strong bonding in the structure is demonstrated by DTA-TG.

Another direction of investigation was to synthesize and to characterize LDH-nanocomposite materials. Deposition-precipitation of metal nanoparticles (Sn/Cu and Ni) was performed by borohydride reduction on a LDH support. A preservation of the layer structure with a greatly decreased degree of crystallinity was observed by XRD and DTA-TG. A polydisperse distribution of the metal particles was observed by TEM, their size varying between 4 and 20 nm for Sn/Cu and between 3-30 nm for Ni [19].

Fig. 1. The packing in NaHC4O4H2O, with hydrogen bonds represented
by dotted lines. [Symmetry codes: (i) 1 + x, 1 y, 1/2 + z; (ii) 1 + x, y, z;
(iii) 1 + x, 1 + y, z]

The calcination of hydrotalcite up to temperatures 350-800oC leads to the formation of periclase-like Mg-Al oxide capable to recover the layer structure upon treating with water or water solutions even at room temperature. This is an important method for obtaining various inorganic or organic forms as well as pillared structures. The mechanism of hydrotalcite regeneration was studied calorimetrically for the first time [108]. This study shows that the regeneration of mixed oxides takes place through crystallization from solution. All processes observed on the calorimetric curves (hydration and dissolution of Mg-Al oxides and crystallization of hydrotalcite) are exothermic. The amount of the evolved heat decreases with increasing the content of Mg in the initial sample.


34. Particle size and support effects on the complete benzene oxidation by Co and Co-Pt catalysts using silica and kenyaite as supports (Yu. Kalvachev, V. Kostov-Kytin, S. Todorova, K. Tenchev, G. Kadinov)

In a preceding work, synthetic kenyaite (layered silicate) was used as a support in catalysts for hydrocarbon combustion (Ann. Rep. No 11/2005). Using this kenyaite and silica, monometallic cobalt and bimetallic Co-Pt samples of various particle sizes were prepared [15, 77]. They are characterized by elemental analysis, XRD, TPR, and XPS. Cobalt is introduced by two methods classical impregnation and ammonia method. The ammonia method of preparation leads to the formation of finely dispersed Co3O4 on both supports. Besides, hardly reducible cobalt silicate phases appear predominantly on the SiO2 support. The Co3O4 particle size varies between 10 and 20 nm, depending on the support. The monometallic Co samples prepared by ammonia method on both supports are more active in benzene combustion than the impregnated ones due to the finer dispersion of the easily reducible Co3O4. It is well known that the transient metal oxides operate in complete hydrocarbon oxidation by redox-type mechanism, according to which the oxide species oxidize the hydrocarbon and are regenerated by the oxygen-containing gaseous phase. In this way the catalytic behaviour can be correlated with the oxide reducibility. The ammonia method of cobalt deposition leads to the formation of finely dispersed cobalt oxide, which is reduced at a lower temperature. The cobalt loading by impregnation leads to the formation of large Co3O4 crystallites, which are reduced at higher temperature. The higher activity at T95 for the Co/SiO2-I (723 K, 95%) in comparison with the activity of Co/Ken-I (723K, 76%) can be related to the smaller particle size of Co3O4 in the former sample (13 nm) and thus to an easy reduction of the cobalt oxide.

The addition of Pt improves the activity and the promoting effect becomes more pronounced for the impregnated sample. This result can be explained by a synergy effect of cobalt oxide species and Pt. In general, the activity of the bimetallic supported samples was found to be lower than that of Pt/SiO2. A possible explanation is that the Pt particles in the bimetallic samples are decorated by (or interact strongly with) cobalt during the pre-treatment. At low concentrations, Pt interacts strongly with the support surface or with the cobalt phase and, as a consequence, its reduction has been impeded. Reduced concentration of Pt on the support was observed upon simultaneous deposition of Pt and Co, with the explanation that cobalt species cover partially that of platinum.


35. Optimizing conditions of growth of mixed Ca1-xSrxF2 crystals and investigation of their optical transmission (J. Mouchovski, L. Dimitrov, B. Kostova, L. Konstantinov)

The oxygen-containing impurities, embedded into the fluorite lattice during the growth of the single or mixed fluoride crystals, deteriorate seriously the optical properties of single or mixed fluoride crystals produced in the CLMC by a version of Bridgman-Stockbarger's technique. That requires further optimization of this method aiming at: (i) minimization of the oxygen and water vapor inside the growing chamber, and (ii) conditions ensuring a slightly convex crystallization front (CF) during the process. Because of that we replaced the low-pressure dynamic argon atmosphere with the high vacuum environment over residual pressure less than 10-3 N/m2 and implemented an in-group growing of mixed Ca1-xSrxF2 crystals (0.383ЈxЈ0.675) in an appropriate temperature regime in order to retain CF-position in the upper half of the adiabatic gradient zone, appearing under conditions for a normal growth of slightly convex CF-shape. The starting sintered/polycrystallized precursors were prepared from grained fluorspar (99.6% purity) and powdered SrF2 (Merck, suprapur) using 1.1 wt.% PbF2 and 0.55 wt.% ZnF2. The final product was in the form of cylindrical bulls with a conical bottom part, sized 1012 mm in length and 1.1252" in diameter. They are transparent, colorless, without any bulk macro- or micro-impurities or defects in the overall volume. The measured stress-induced birefringence of the bulls was less than 5 nm/cm for all the peripheral bulls and being slightly higher only within small sections into the central bull.

Fig. 1. Optical transmission spectra of Ca1-xSrxF2
windows prepared from cylindrical crystals
(1"1.125" in diameter) grown by BS-technique
modified in CLMC.

The optical transmission of well-polished plane-parallel windows with thickness of 6.00±0.15 mm was studied in the spectral range 200-400 nm. It was found that the transmission of light increases with increasing the concentration of strontium x for wavelength above 220 nm (Fig. 1).

The presence of REE impurities forms optical-active centers and generates several specific bands of light absorption in that spectral range, the positions and intensity of which (measured as the area below the peaks) were inspected as functions of x in order to find a possible relationship. The observed 8 picks in the spectra can be assigned to Yb2+ (two peaks), Ce3+, Sm2+, Sm3+ (two peaks), and Eu2+. The spectral behavior of these peaks, concerning both the shifting in the position and the change in the intensity, can serve to draw conclusions on the effect of Sr concentration on the optical properties of such mixed materials [71, 72].


36. Incorporation of mixed valence vanadium in the microporous titanosilicate AM-2 (S. Ferdov, Z. Lin, R. A. Sб Ferreira)

Experiments conducted in the system Na2O K2O TiO2 V2O5 SiO2 H2O have resulted in the successful incorporation of mixed valence vanadium in the framework of microporous titanosilicate AM-2 (K2TiSi3.O9.H 2O, also known as STS, a structural analogue of umbite). The performed powder XRD analysis indicated a single phase that showed extended unit cell dimension due to the isomorphous substitution of silicon by vanadium in tetrahedral coordination. DR UV-Vis spectra displayed the presence of both octahedral V4+ and V5+and tetrahedral V5+, which is an example for direct synthesis of mixed valence vanadium containing microporous titanosilicate. The framework distortion after V incorporation and the presence of paramagnetic V4+ ions broadened the 29Si MAS NMR spectrum of the V-AM-2 sample and resulted in the fail of detecting 51V MAS NMR signals.

Furthermore, for the first time REE silicates with apatite-type structure were prepared under mild hydrothermal conditions. The synthesized Eu8.18Na1.08(SiO4) 6 (OH)1.62-2yOy and Eu3.96Gd3.96Na1.2(SiO 4)6(OH)1.86-2yOy were structurally and optically characterized [9].


V. PhD THESESES

37. Crystal chemical and structural characteristics of natural and modified montmorillonites from Bulgarian deposits of bentonite clays (A. Ilieva)

A detailed study is performed on the crystal chemical and structural features of montmorillonite in bentonite clays from the Oligocene volcanogenic-sedimentary complex, East Rhodopean-Upper Tracian Paleogene Depression. For this purpose, a complex of modern physical and chemical methods as well as specific methodology for analysis of smectites were applied [14]. For the first time the method of n-alkyl ammonium exchange is used for characterization of the mean values and distribution of the layer charge of montmorillonites from Bulgarian bentonites. According to the chemical composition the studied montmorillonites can be specified in two groups:

• more siliceous, with higher contents of Mg and Fe, and Na-Ca interlayer cations montmorillonite from bentonites of Kardjali deposit;

• with higher Al contents, almost not containing Fe; and with predominantly Ca interlayer cations montmorillonite from white bentonites (deposits near Enchets, Dimitrovgrad and Zlatna livada).

Based on the calculated crystal-chemical formulae, octahedral cationic occupancy, distribution and localization of the layer charges, the montmorillonite varieties are grouped in two crystal-chemical types according to the classification of dioctahedral smectites, namely:

• type "Wyoming" montmorillonite from bentonites of Kardjali deposit (with lower mean values of the layer charge, more homogeneously distributed);

• type "Tatatila" montmorillonite from the white bentonite clays (relatively higher charged and with higher degree of charge heterogeneity).

The main minerals accompanying montmorillonite in the clay fractions (cristobalite, calcite, X-ray amorphous Fe-oxides-hydroxides) and their quantitative relations were established. The chemical analyses were recalculated in order to obtain accurate crystal-chemical formulae of montmorillonite. The structural state of the free SiO2 (earlier described as low-temperature cristobalite) was determined as opal-C, grown epitactically on the surface of the montmorillonite particles along the following orientations of the two structures: (112)crist//(001)montm.

So called "pillared" clays (PILC) are prepared by intercalation of polymer Al-oxy-hydroxy cations (Al13 - type „Keggin"). Thermally stable modification was obtained only for the montmorillonite from the white bentonite (with low Fe content and higher crystallinity).


38. Mineralogical features of zircon from Paleozoic metagranites from Ograzhden Mountain, Serbo-Macedonian massif, SW Bulgaria (R. Titorenkova)

The thesis aims at presenting a systematic investigation of numerous representative zircon crystals from amphibolite facies metamorphic rocks (metagranites) and at performing the relationships existing between their morphological characteristics, the inhomogeneities in their internal textures, the chemical composition and structure, the age of crystallization, the degree of structural disorder due to accumulated radiation defects, and the simultaneous recovery of the structure due to thermal annealing.

It is shown that the increase in the degree of migmatization of the embedding rocks affects substantially the morphology, chemical composition, internal textures, isotopic ratios and the degree and type of structural disorder of zircon crystals [43].

Based on the studied crystal features one can separate zircon according to the source of crystallization and to the secondary alteration of the protholitic crystals.

The degree of zircon metamictization was studied as a function of the accumulated radiation dose as determined via the measured concentration of uranium and thorium for an age of crystallization (460 Ma) and using existing theoretical models for describing the processes of metamictization and thermal recovery of the structure.


39. Structural models of vitreous B2O3 (B. Shivachev)

The thesis is aiming at investigation of the structural evolution in vitreous boron oxide (v-B2O3) network associated with the appearance of micro-heterogeneities [37]. TEM analysis showed that in the structure of quenched v-B2O3 heterogeneities were not formed, whereas in the slowly cooled v-B2O3 cluster formation occurred. Positron lifetime spectroscopy was employed for the first time to clarify v-B2O3 structural discrepancies. Three lifetimes were mesearued: the shortest one (0.224 ns) is associated with annihilation of e+ in I-B2O3 crystal mono-vacancies; the middle (0.350 ns) with annihilation around oxygen sites for both I-B2O3 and v-B2O3, and the longuest lifetime (1.45 ns) related to the presence of B3O6 units in v-B2O3.

Molecular Dynamics simulations, employing an optimized potential for B2O3, were carried out. Two different cooling cycles were used, showing that structural differences occur in the final models. It was found that the ratio of B atoms contained in B3O6 units varies between 9 and 30% depending on the cooling rate.

The network formation of v-B2O3 was simulated by Molecular mechanics and it was shown that combination between clusters with different ratio of the structural units BO3 vs. B3O6 can reproduce the calculated experimental density and the radial distribution function.

INTERINSTITUTE PROJECTS

· "Synthesis and crystallochemical study of new porous materials - potential catalysts and sorbents", Joint research project between CLMC-BAS and the Institute of Inorganic Chemistry - Chezh Academy of Science;

· "Thermal and mechanochemical investigations in synthesis of environmentally balanced mineral fertilizers", Joint research project between CLMC-BAS and Tallinn Technical University and Estonian Academy of Sciences;

· "Origin and distribution of Europe's most important copper and gold deposits in Bulgaria, Romania and Serbia-Montenegro", Joint research project sponsored by Swiss National Fund for Scientific Researches.


POSTDOCTORAL FELLOWS AND VISITING SCIENTISTS

Dr. Stanislav Ferdov - University of Aveiro, Department of Chemistry, Portugal.

Dr. Rossitza Petrova - Yamagouchi University, Department of Advanced Material Science and Engineering, Tokiwadai, Ube, Japan.

Dr. Boriana Mihailova - visitor-professor on "Spectroscopy of minerals" and "Crystal Physics" at the Faculty of Earth Sciences, University of Hamburg, Germany.


RESEARCH TOPICS, ANNOUNCED FOR INTERNATIONAL PARTNERSHIP COLLABORATION


PUBLICATIONS AND REPORTS AT CONFERENCES AND LOCAL MEETINGS


PUBLISHED ARTICLES AND REPORTS

1. Atanassova-Vladimirova, S., I. Piroeva, K. Kuzmanov, B. Mavroudchiev. 2006. Amphiboles of Vitosha pluton indicators of magmatic evolution. In: Proc. of the Nat. confer. with inter. participation "GEOSCIENCES 2006", Sofia, 193-197.

2. Bakardjieva, S., V. Stengl, L. Szatmary, J. Lukac, N. Murafa, D. Nizmansky, K. Cizek, J. Jirkovsky, N. Petrova. 2006. Transformation of brookite-type TiO2 nanocrystals to rutile: correlation between microstructure and photoactivity. J. of Mater. Chem., v. 16, 1709-1716.

3. Banushev, B., Z. Tsintsov. 2006. New occurrence of "Shumen" type agates in NE Bulgaria. Compt. rend. Acad. bulg. Sci., 15, 12, 1259-1264.

4. Campos, A. A., L. Dimitrov, C. R. da Silva, M. Wallau, E. A. Urquieta-Gonzalez. 2006. Recrystallisation of mesoporous SBA-15 into microporous ZSM-5. Microporous and mesoporous materials, v. 95, 1-3, 93-104.

5. Campos, A. A., C. R. Silva, L. D. Dimitrov, M. Wallau, E. A. Urquieta-Gonzalez. 2006. Secondary crystallizaton of SBA-15 in the presence of TPAOH and aqueous glycerol influence of the water content. 9th Inter. Symp. "Scientific Bases for the Preparation of Heterogeneous Catalysts", E.M. Gaigneaux et al. (Eds.), September 10-14, Louvain-la-Neuve (Belgium), Elsevier, 347-354.

6. Dimitrov, L. D., M. Wallau, E. A. Urquieta-Gonzбlez. 2006. Mordenite seeding gels mesostructured by the non-ionic surfactant Pluronic P123. 9th Inter. Symp. "Scientific Bases for the Preparation of Heterogeneous Catalysts", E.M. Gaigneaux et al. (Eds.), September 10-14, Louvain-la-Neuve (Belgium), Elsevier, 433-440.

7. Dimitrova, D., E. Tarassova, M. Tarassov. 2006. Rare Bi and Ni minerals from Martinovo iron skarn deposit, North-western Bulgaria. In: Proc. of field workshop "Au-Ag-Te-Se deposits", Cook, N. J., I. Ozgenc, T. Oyman (Eds.), Izmir, Turkey, September 24-29, 42-49.

8. Dyulgerov, M., I. Peytcheva, A. v. Quadt, R. Nedialkov. 2006. Source and age heterogeneities between the rocks of Lutzkan pluton. In: Proc. of the Nat. confer. with inter. participation "GEOSCIENCES 2006", Sofia, 177-180.

9. Ferdov, S., Z. Lina, R. A. Sб Ferreira. 2006. Incorporation of mixed valence vanadium in the microporous titanosilicate AM-2. Microporous and mesoporous materials, v. 96, 363-368.

10. Ganev, V., L. Macheva. 2006. Crystal chemical and structural peculiarities of staurolite from rocks undergone different metamorphic evolution: FTIR spectroscopy study. In: Proc. of the Nat. confer. with inter. participation "GEOSCIENCES 2006", Sofia, 120-123.

11. Georgiev, S., A. von Quadt, I. Peytcheva, P. Marchev, C. A. Heinrich. 2006. Eastern Srednogorie zone new geochemical data for lateral zonation of magmatism. In: Proc. of the Nat. confer. with inter. participation "GEOSCIENCES 2006", Sofia, 197-200.

12. Gonзalves, M. L., L. D. Dimitrov, M. Wallau, E. A. Urquieta-Gonzбlez. 2006. Mesoporous ZSM-5 synthesized by simultaneous mesostructuring and crystallization of ZSM-5 nuclei. 9th Inter. Symp. "Scientific Bases for the Preparation of Heterogeneous Catalysts", E.M. Gaigneaux et al. (Eds.), September 10-14, Louvain-la-Neuve (Belgium), Elsevier, 323-330.

13. Iliev, M., I. Donchev. 2006. A method for estimation and analysis of performance indices for concentration circuits. In: Proc. of XXIII Inter. Mineral Proc. Congress, Istanbul, Turkey, September 3-8, v. 3, 1972-19-76.

14. Ilieva, A. 2006. Crystal chemical and structural characteristics of natural and modified montmorillonites from Bulgarian deposits of bentonite clay. (PhD Thesis), pp. 36.

15. Kalvachev, Y., V. Kostov-Kitin, S. Todorova, K. Tenchev, G. Kadinov. 2006. Synthetic kenyaite as catalyst support for hydrocarbon combustion. Applied catalysis B: Environmental, 66, 192-197.

16. Kamenov, B., R. Nedyalkov, M. Popov, E. Tarassova, B. Mavroudchiev. 2006. The Malko Turnovo pluton in Southeastern Bulgaria: I. New data on its petrographical composition and rock-forming minerals. Geochem., miner. and petrol., 44, 103-130 (in Bulgarian with English abstract).

17. Karayigit, A., Y. Bulut, G. Karayigit, X. Querol, A. Alastuey, S. Vassilev, C. Vassileva. 2006. Mass balance of major and trace elements in a coal-fired power plant. Energy Sources, 28, 1311-1320.

18. Kolev, T., R. Bakalska, B. Shivachev, R. Petrova, 2006. Codeinone. Acta Cryst., Section E: Structure Reports Online, 62, 1, o255-o257.

19. Kostadinova, D., N. Petrova, I. Dragieva, C. Gerardin, D. Tichit. 2006. Deposition-precipitation by borohydride reduction of metal nanoparticles on layer double hydroxide support. Nanoscience & Nanotechnology, 6, 175-178.

20. Kouzmanov, K., A. von Quadt, I. Peytcheva, C. A. Heinrich, T. Pettke, E. Rosu. 2006. Geochemical and time constraints on porphyry ore formation in the Barza magmatic complex, Apuseni Mountains, Romania. In: Proc.of field workshop "Au-Ag-Te-Se deposits", Cook, N. J., I. Ozgenc, T. Oyman (Eds.), Izmir, Turkey, September 24-29, 96-102.

21. Lihareva, N., O. Petrov, Y. Tzvetanova. 2006. Application of the BCR sequential extraction procedure to studying the partitioning of metals in sewage sludge and sediments. Bulg. Chem. Comm., v. 38, No 2, 131-139.

22. Macheva, L., I. Peytcheva, A. v. Quadt, N. Zidarov, E. Tarassova. 2006. Petrological, geochemical and isotope features of Lozen metagranite, Belasitza Mountain evidence for widespread distribution of Ordovician metagranitoids in the Serbo-Macedonian Massif, SW Bulgaria. In: Proc. of the Nat. confer. with inter. participation "GEOSCIENCES 2006", Sofia, 209-212.

23. Marchev, P., A. von Quadt, I. Peytcheva, M. Ovtcharova. 2006. The age and origin of the Chuchuliga and Rosino granites, Eastern Rhodopes. - In: Proc. of the Nat. confer. with inter. participation "GEOSCIENCES 2006", Sofia, 213-216.

24. Marinova, I. 2006. Preliminary data on the morphology of electrum from the layer-like pervasive silicification in Stenata outcrop, Khan Krum gold deposit, SE Bulgaria. In: Proc. of the Nat. confer. with inter. participation "GEOSCIENCES 2006", Sofia, 113-116.

25. Marinova, I. 2006. Replacement textures from the electrum-bearing, layer-like pervasive silicification in the low sulfidation Khan Krum gold deposit, SE Bulgaria. Compt. rend. Acad. bulg. Sci., 59, 9, 945-948.

26. Marinova, I. 2006. Open-space filling textures from the electrum-bearing, layer-like pervasive silification in the low sulfidation Khan Krum gold deposit, SE Bulgaria. Compt. rend. Acad. bulg. Sci., 59, 10, 1027-1030.

27. Marinova, I. 2006. Brecciation textures from the electrumbearing, layer-like pervasive silification in the low sulfidation Khan Krum gold deposit, SE Bulgaria. Compt. rend. Acad. bulg. Sci., 59, 11, 1163-1166.

28. Marinova, V., B. Mihailova, T. Malcherek, C. Paulmann, K. Lengyel, L. Kovacs, M. Veleva, M. Gospodinov, B. Gьttler, R. Stosch, U. Bismayer. 2006. Structural, optical and dielectric properties of relaxor-ferroelectric Pb0.78Ba0.22Sc0.5Ta 0.5O3. J. Phys.: Cond. Matter., 18, L385-L393.

29. Mikhailova, V., I. Mincov, T. Troev, V. Ganev, K. Berovsky. 2006. Investigation of Co78Si15B10 metallic glass by positron lifetime measurements and X-ray analysis. Comp. rend. Acad. bulg. Sci., v. 59, 11, 1131-1136.

30. Mihaylov, M., E. Ivanova, F. Thibault-Starzyk, M. Daturi, L. Dimitrov, K. Hadjiivanov. 2006. New types of nonclassical iridium carbonyls formed in Ir-ZSM-5: A fourier transform infrared spectroscopy investigation. J. Phys. Chem. B, 110, 10383-10389.

31. Nedialkov, R., A. Zartova, R. Moritz, F. Bussey, A. von Quadt, I. Peytcheva, D. Fortignie. 2006. Magmatic petrology and exsolution of ore-bearing fluid in the magmatic center Assarel, Central Srednogorie, Bulgaria. In: Proc. XVIII Congress CBGA, September 3-6, Belgrade, Serbia, 411-414.

32. Nihtianova, D., J. Li, U. Kolb. 2006. Electron crystallography in mineralogy and materials research. In: Electron Crystallography, Novel Approaches for Structure Determination of Nanosized Materials, Th. E. Weirich, J. L. Labar and X. Zou (Eds.), Springer, 421-433.

33. Penev, V., L. Konstantinov, M. Marinov. Geometrization of the language of chemistry: Approximate spatial mathematical model of different species of atoms and Mendeleev's Periodic Law Academic Open Internet Journal, v. 17, 4/24/2006, http://www.acadjournal.com/2006/V17/part2/p2/Geometrization.pdf

34. Petrova, N., B. Shivachev, T. Kolev, R. Petrova. 2006. Sodium hydrogensquarate monohydrate. Acta Cryst., Section E: Structure Reports Online, 62, 6, m1359-m1361.

35. Peytcheva, I., A. v. Quadt, O. Malinov, E. Tacheva, R. Nedialkov. 2006. Petrochan and Klissura plutons in Western Balkan: relationships, in situ and single grain U-Pb zircon/monazite dating and isotope tracing. In: Proc. of the Nat. confer. with inter. participation "GEOSCIENCES 2006", Sofia, 221-224.

36. Ruskov, K., A. von Quadt, I. Peytcheva, S. Georgiev, S. Strashimirov, S. Stoykov. 2006. Geochemical and Sr-Nd isotope constraints on the Late Cretaceous magmatism in the area of the Zidarovo ore field. Ann. of the Univ. of mining and geology "St. I. Rilski", 49, 1, Geology and Geophysics, 131-136.

37. Shivachev, B. 2006. Structural models of vitreous B2O3. (PhD Thesis), pp. 31.

38. Shivachev, B., R. Petrova, E. Naydenova. 2006. 3prime;-aminocyclohexanespiro-52-hydantoin-phenylboronic acid (1/1). Acta Cryst., Section E: Structure Reports Online, 62, 9, o3887-o3889.

39. Shivachev, B., R. Petrova, P. Marinova, N. Stoyanov, A. Ahmedova, M. Mitewa. 2006. Four cycloalkanespiro-42 -imidazolidine-22,52 -dithiones. Acta Cryst., Section C: Crystal Structure Communications, 62,4, o211-o215.

40. Stoyanova, M., S. Angelova, K. Kosev, P. Dencova, V. Enchev, M. Palamareva. 2006. Synthesis of trans/cis 4-substituted, 3-Furyl-2-phenethyl-tetrahydroisoquinolin-1-one; cinformation of the trans-4-(pyrrolidinylcarbonyl) derivative. Tetrahedron Letters, 47, 13, 2119-2123.

41. Tacheva, E., R. Nedialkov, I. Peytcheva. 2006. Magma mingling and mixing in Petrochan pluton (Western Balkan): preliminary field, petrological and geochemical evidence. In: Proc. of the Nat. confer. with inter. participation "GEOSCIENCES 2006", Sofia, 161-164.

42. Tarassov, M., E. Tarassova. 2006. Processes of replacement and in-situ Th-U-Pb electron microprobe dating of monazite and xenotime from Igralishte granite pluton (Southwestern Bulgaria). In: The theory, history, philosophy and practice of mineralogy (Proc. of IV Inter. mineralogical seminar, Syktyvkar, Komi Republic, May 17-20), 290-291 (in Russian).

43. Titorenkova, R. 2006. Mineralogical features of zircon from Paleozoic metagranites from Ograzhden Mountain, Serbo-Macedonian massif, SW Bulgaria. (PhD Thesis), pp. 30.

44. Titorenkova, R., B. Michailova, L. Konstantinov. 2006. Raman spectroscopic study of variably recrystallized metamict zircon from amphibolite-facies metagranites, SMM, Bulgaria. Canadian Mineralogist, 44, 1481-1490.

45. Todorov, P., E. Naydenova, R. Petrova, B. Shivachev, K. Troev. 2006. [(4,4-dimethyl-2-oxo-1,3-oxazolidin-3-yl)methyl]phosphonic acid. Acta Cryst., Section C: Crystal Structure Communications, 62, 11, o661-o662.

46. Tsintsov, Z. 2006. The archaeomineralogy independent interdisciplinary direction in the archaeometry and the Bulgarian science. In: Proc. of the Nat. confer. with inter. participation "GEOSCIENCES 2006", Sofia, 151-154.

47. Tsintsov, Z., B. Banushev, E. Vulev. 2006. Sagenitic agates from the Eastern Rhodopes. Mining and geology, 10, 36-40 (in Bulgarian with Russian and English abstracts).

48. Tsintsov, Z., Z. Popov, B. Banushev. 2006. Archaeometallurgical investigation in the region of Vulche pole village, Haskovo district Ann. of the Univ. of mining and geology "St. Iv. Rilski", v. 49, p. I, Geology and geophysics, 79-84 (in Bulgarian with English abstract).

49. Tzankova, N., O. Vitov. 2006. Mineralogical peculiarities and distribution of garnet mineralizations in Sacar Mountain, SE Bulgaria. Ann. of the Univ. of mining and geology "St. Iv. Rilski", v. 49, p. I, Geology and geophysics, 69-78 (in Bulgarian with English abstract).

50. Tzankova, N., O. Petrov. 2006. ICP AES, microprobe, and X-ray powder diffraction data for garnets from metamorphic rocks in the Sakar region, SE Bulgaria. Geochem., miner. and petrol., v. 44, 73-89.

51. Tzankova, N., O. Petrov, M. Kadiyski. 2006. Crystal chemical features of garnets from metamorphic rocks of Zhalti chal and Ustrem formations from the frame of Sakar Pluton, SE Bulgaria. Compt. rend. Acad. bulg. Sci., 59, 5, 531-538.

52. Vassilev, S. 2006. Basic and applied aspects of mineralogy and geochemistry of coals. Mining and Geology, 7, 31-37 (in Bulgarian with Russian and English abstracts).

53. Vassilev, S., N. Lihareva, C. Vassileva. 2006. Sequential leaching behaviour of some elements during chemical treatment of Bobov Dol coal fly ash. Compt. rend. Acad. bulg. Sci., 59, 6, 645-650.

54. Vassilev, S., N. Lihareva, C. Vassileva. 2006. Sequential leaching behaviour of some elements during chemical treatment of ceramic cenospheres from coal fly ash. Compt. rend. Acad. bulg. Sci., 59, 7, 753-758.

55. Vassileva, C., S. Vassilev. 2006. Behaviour of inorganic matter during heating of Bulgarian coals. 2. Subbituminous and bituminous coals. Fuel Processing Technology, 87, 1095-1116.

56. Videva, V., T. Tosheva, A. Chauvin, S. Shenkov, R. Petrova, R. Scopelliti et al. 2006. Phosphoamide modified p-tert-butyl calix[4]arene and its sodium complexes: synthesis, coordination ability and structure. Polyhedron, 25, 11, 2261-2268.

57. Vitov, O. 2006. Mineralogical study and dividing of Pernik administrative district, Western Bulgaria, based on stream-sediment surveys. In: Proc. of the Nat. confer. with inter. participation "GEOSCIENCES 2006", Sofia, 243-246 (in Bulgarian with English abstract).

58. Vitov, O., I. Marinova, I. Dimitrov. 2006. Project "Mercury pollutions and mercury mineralizations in Bulgaria. In: Proc. of the Nat. confer. with inter. participation "GEOSCIENCES 2006", Sofia, 247-250 (in Bulgarian with English abstract).

59. Vitov, O., V. Nikolov. 2006. Tuzlites a new type of coast protection equipment. In: Proc. of National-pract. confer. "State and control of the slides and erosive processes in Bulgaria", NTU, Sofia, November 31 December 1, 94-103 (in Bulgarian with English abstract).

60. Vitov, O., V. Nikolov. 2006. Ecological and economical aspects of barrages and barrage systems in Bulgaria. In: Proc. of National-pract. Conf. "State and control of the slides and erosive processes in Bulgaria", NTU, Sofia, November 31 December 1, 283-287 (in Bulgarian with English abstract).

61. Von Quadt, A., S. Sarov, I. Peytcheva, E. Voynova, N. Petrov, K. Nedkova, K. Naydenov. 2006. Metamorphic rocks from northern parts of Central Rhodopes conventional and in situ U-Pb zircon dating, isotope tracing and correlations. In: Proc. of the Nat. confer. with inter. participation "GEOSCIENCES 2006", Sofia, 225-228.

62. Wallau, M., L. D. Dimitrov, C. R. Silva, E. A.Urquieta-Gonzalez. 2006. Mesoporous ZSM-5 prepared by sequential nanocasting of MCM-41 nanospheres. 9th Intern. Symp. "Scientific Bases for the Preparation of Heterogeneous Catalysts", E.M. Gaigneaux et al. (Eds.), September 10-14, Louvain-la-Neuve (Belgium), Elsevier, 409-416.

63. Zidarov, N. 2006. Common regularities during origination, alteration and interactions of the mineral systems. In: The theory, history, philosophy and practice of mineralogy (Proc. of IV Inter. mineralogical seminar, Syktyvkar, Komi Republic, May 17-20), 37-38 (in Russian).

64. Zidarova, B., N. Zidarov. 2006. Application of topographic mineralogy in the creation of geological-genetic models for the Fluorite mineral formation in Bulgaria. In: The theory, history, philosophy and practice of mineralogy (Proc. of IV Inter. mineralogical seminar, Syktyvkar, Komi Republic, May 17-20), 114-116.


PUBLICATIONS IN PRESS

65. Kamenov, B., Y. Yanev, R. Nedialkov, R. Moritz, I. Peytcheva, A. von Quadt, S. Stoykov, A. Zartova. Petrology of Late-Cretaceous island-arc ore-magmatic centers from Central Srednogorie, Bulgaria: magma evolution and paths. Geochem., mineral. and petrol.,

66. Klocke, A., B. Mihailova, S. Zhang, B. Gasharova, R. Stosch, B. Gьttler, B. Kahl-Nieke, P. Henriot, B. Ritschel, U. Bismayer. CO2 laser-induced zonation in dental enamel: a Raman and IR micro-spectroscopic study. J. of Biomedical Materials research B,

67. Kossev, K., T. Tsanov. Application of modified poly (ethylene oxide) networks in phase-transfer catalysis. Polymer,

68. Kostova, B. Optical spectroscopy in the UV-SIS-NIR range as a means for studying minerals. Rev. Bulg. Geol. Soc., (in Bulgarian)

69. Mihailova, B., M. Bastjan, B. Schulz, M. Rьbhausen, M. Gospodinov, T. Malcherek, R. Stosch, B. Gьttler, U. Bismayer. Resonance Raman scattering of relaxor-ferroelectric PbSc0.5Ta0.5O3 and PbSc0.5Nb0.5O3. Applied Physics Letters,

70. Milenov, T. I., V. I. Dimov, M. M. Gospodinov. TEM observation of two-dimensional defects in CdTe crystals. J. of Optoelectronics and Advanced Materials,

71. Mouchovski, J. Control of oxygen contamination during growing of optical calcium fluoride and strontium fluoride crystals. Progress in crystal growth and characterization of materials,

72. Mouchovski, J. Growing of mixed crystal compounds based on calcium and strontium fluorides. Bulg. Chem. Comm., March,

73. Penev, V., N. Zidarov, B. Zidarova. Geometrization of the language of mineralogy. Review of the basic results. Academic Open Internet Journal,

74. Peytcheva, I., A. v. Quadt, N. Georgiev, Zh. Ivanov, C. A. Heinrich, M. Frank. Combining trace-element compositions, U-Pb geochronology and Hf isotopes in zircons to unravel complex calcalkaline magma chambers as inferred by mixed gabbros and granodiorites in the Upper Cretaceous Srednogorie zone (Bulgaria). Lithos,

75. Stoilov, V., I. Donchev, O. Petrov, V. Petkova, Y. Kalvachev, N. Lihareva. Mineral composition and comparative characteristics of Bulgarian Oligocene phosphorites. Rev. Bulg. Geol. Soc., (in Bulgarian with English abstract).

76. Tsintsov, Z., K. Radoikov. Traces of ancient processing of placer gold in the region of Gorno Uino village. In: Pautalia-Velbugde-Kyustendil and adjacent territories, Vth Inter. Sym., October 5-7, Regional Historical Museum, Kyustendil, (in Bulgarian).

77. Todorova, S., G. Kadinov, K. Tenchev, Yu. Kalvachev, V. Kostov-Kytin. Particle size and support effects on the complete benzene oxidation by Co and Co-Pt catalysts. J. of Materials Science,

78. Vassilev, S., C. Vassileva. A new approach for the classification of coal fly ashes based on their origin, composition, properties, and behaviour. Fuel,

79. Vitanov, P., V. Dimov, A. Harizanova, B. Kostova, I. Piroeva. Structure analysis of nanostructured TiO2 thin films using transmission electron microscopy. J. of Optoelectronics and Advanced Materials,

80. Vitov, O. Geological and historical information for gold mining in Kyustendil district. In: Pautalia-Velbugde-Kyustendil and adjacent territories, Vth Inter. Sym., October 5-7, Regional Historical Museum, Kyustendil, (in Bulgarian)

81. Wang, X., A. Klocke, B. Mihailova, R. Stosch, B. Gьttler, U. Bismayer. Effect of bleaching on dental hard tissues: a Raman and IR spectroscopic study. Key Engineering Materials,

82. Zidarov, N., E. Tarassova, I. Peytcheva, A. v. Quadt, V. Andreichev, R. Titorenkova. Petrology, geochemistry and age dating of Skrut granitoids new evidence for Lower Triassic magmatism in Belassitsa Mountains (SW Bulgaria). Geologica Balcanica,


REPORTS ON SCIENTIFIC EVENTS:

83. Bismayer, U., B. Mihailova, S. Zhang, A. Klocke, B. Gasharova. 2006. Transition of laser-treated dental enamel. 23rd European Crystallographic Meeting ECM23, Leuven, Belgium, August 6-11, poster.

84. Bismayer, U., B. Mihailova, S. Zhang, A. Klocke, B. Gasharova. 2006. CO2 laser-irradiated dental enamel: A spectroscopic study. 84th annual meeting of German Mineralogical Society (DMG), September 25-27, Hannover, Germany, poster.

85. Chakalov, K., T. Popova, K. Mitov, O. Petrov, E. Filcheva. 2006. A model for the impact of ferritized clinoptilolite on flooded soil. 7th Inter. Confer. on the Occurrence, Properties, and Utilization of Natural Zeolites, July 1621, Socorro, New Mexico, USA, Extended Abstracts, 78-79, poster.

86. Georgiev, S., A. v. Quadt, I. Peytcheva, P. Marchev, C. A. Heinrich. 2006. Sources and magma evolution of Eastern Srednogorie, SE Europe: conventional and in situ isotope data. Abstract 16 V. M. Goldschmidt Confer., August 27 September 1, Melbourne, Australia, CD version.

87. Georgieva, G., R. Petrova, B. Shivachev, I. Kuleff, G. Gencheva. 2006. Synthesis, solution chemistry and structural characterization of ruthenium complexes with 3-amino-2-chloropyridine. crystal structure of bis(2-chloropyridin-3-ylamino) ruthenium(IV)-tetrachloride. Inter. Symp. on Organic Chemistry, December 9-12, Sofia, Bulgaria.

88. Goev, G., V. Masheva, L. Ilkov, D. Nihtianova, M. Mikhov. 2006. Magnetic properties of Ni Cu Zn ferrites with Co substitution. 6th Inter. Confer. of the Balkan Physical Union, August 22-26, Istanbul, Turkey, 6 P 063, poster.

89. Gonçalves, M. L., L. D. Dimitrov, M. Wallau, E. A. Urquieta-González. 2006. Synthesis of mesoporous zeolite ZSM-5. 9th Nat. Catalysis Confer., Bulg. Catalysis Club, November 15, Sofia, Inst. of Catalysis-BAS, p. 20.

90. Damianova, A., I. Sivriev, N. Lichareva. 2006. Changes in chemical content of water plants (F.antipyretica) due to the variation of Cu concentration in the local environment. Workshop on Biological Activity of Metals and Metal Components, November 2-3, Sofia, Book of Abstracts, 24-25.

91. Kostov-Kytin, V., S. Ferdov, B. Mihailova, O. Petrov. 2006. Hydrothermal synthesis of microporous titanosilicates. 7th Inter. Confer. on the Occurrence, Properties, and Utilization of Natural Zeolites, July 1621, Socorro, New Mexico, USA, Extended Abstracts, 148-149, poster.

92. Ljutzkanov, L., I. Stambolova,V. Blaskov, S. Vassilev, V. Petkova, D. Mehandjiev. 2006. Synthesis of nanosized TiO2 particles on activated carbon. 8th Workshop Nanoscience & Nanotechnology, November 20-22, Sofia, poster.

93. Marinova, V., B. Mihailova, D. Petrova, T. Malcherek, U. Bismayer. 2006. Growth, structural, electrical and optical properties of complex perovskite-type Pb0.78Ba0.22Sc0.5Ta 0.5O3 crystals. DPG AKG-Frühjarstagung, 21st General Confer. of the EPS Condensed Matter Division, Dresden, March 26-31, poster.

94. Marinova, V., S. H. Lin, K. Y. Hsu, B. Mihailova, U. Bismayer. 2006. Electrical, photoelectrical and optical properties of Ru-doped Bi12M(Si,Ti)O20 crystals. DPG AKG-Frühjarstagung, 21st General Confer. of the EPS Condensed Matter Division, Dresden, March 26-31, poster.

95. Mihailova, B. 2006. Nanoscale domains and structural transformations in relaxor ferroelectrics. Invited talk at the colloquium of the Institute of Solid State Physics, Bulgarian Academy of Sciences, Sofia, March.

96. Mihailova, B. 2006. Laser treatment of dental materials. Invited talk at the summer seminar of the Graduiertenkolleg 611 "Design and characterisation of functional materials", Universität Hamburg, Germany, May.

97. Mihailova, B. 2006. Local structure and phonon anomalies in relaxor-ferroelectric lead scandium niobates and tantalates. Invited talk at the summer colloquium of the Institute of Applied Physics, Tübingen, Germany, June.

98. Mihailova, B. 2006.Local structural phenomena in relaxor-ferroelectric lead scandium niobates and tantalates: a Raman spectroscopic study. Alexander von Humboldt Kolleg "Ferroics", October 26-28, Clare Hall Cambridge, UK, invited talk.

99. Mihailova, B. 2006. High-pressure-induced renormalization phenomena in lead scandium niobates and tantalates with relaxor behaviour. 1st Workshop of SPP 1236, October 10 November 01, Hünfeld, Germany, talk.

100. Mihailova, B., A. Ilieva, Z. Tsintsov, O. Petrov. 2006. A Raman spectroscopic study of microcrystalline opals. 84th annual meeting of German Mineralogical Society (DMG), September 25-27, Hannover, Germany, poster.

101. Mihailova, B., B. Güttler, T. Malcherek, C. Paulmann, R. Stosch, M. Gospodinov, U. Bismayer. 2006. Effect of B"-site cation on the local structure of perovskite-type relaxor ferroelectrics. 14. Jahrestagung der DGK 2006, Freiburg, April 3-6, poster.

102. Mihailova, B., B. Güttler, M. Gospodinov, U. Bismayer. 2006 Chemically-induced renormalization phenomena in relaxor-ferroelectric PbSc0.5Ta0.5O3. 23rd European Crystallographic Meeting ECM23, Leuven, Belgium, August 6-11, poster.

103. Mihailova, B., V. Marinova, T. Malcherek, C. Paulmann, M. Gospodinov, B. Güttler, U. Bismayer. 2006. Local structure and optical properties of relaxor-ferroelectric Pb0.78Ba0.22Sc0.5Ta 0.5O3 single crystals. 84th annual meeting of German Mineralogical Society (DMG), September 25-27, Hannover, Gernamy, talk.

104. Mihailova, B., U. Bismayer, B. Güttler, R. Stosch, M. Gospodinov. 2006. Temperature evolution of the phonon anomalies in relaxor ferroelectic PbSc0.5(Nb,Ta)0.5O3 , DPG AKG-Frühjarstagung, 21st General Confer. of the EPS Condensed Matter Division, Dresden, March 26-31, poster.

105. Pelovski, Y., V. Petkova, I. Dombalov. 2006. Thermotribochemical treatment of low grade natural phosphates. 9th European Symposium on Thermal Analysis and Calorimerty, August 27-31, Krakow, Poland.

106. Penev, V. Geometrization of the foundations of the chemistry: Part I. Formulation of the problem and geometrization of the statics of simple chemical objects. Report to seminar "Geometry and symmetry in physics" to Institute of Biophysics-BAS.

107. Penev, V. Geometrization of the foundations of the chemistry: Part II. Geometrization of the dynamics of simple chemical objects and the statics and dynamics of complex chemical objects. Report to seminar "Geometry and symmetry in physics" to Institute of Biophysics-BAS.

108. Petrova, N., Ts. Stanimirova, G. Kirov. 2006. Hydrotalcite regeneration: a calorimetric study. Fourth Mediterranean Clay meeting, September, 5-10, Ancara, Turkey.

109. Peytcheva, I., A. v. Quadt, R. Nedialkov, C. A. Heinrich, M. Frank. 2006. Timing and magma evolution in Medet Cu-porphyry deposit, SE Europe: controversial or coinciding isotope data? Abstract 16 V. M. Goldschmidt Conference, August 27 September 1, Melbourne, Australia, CD version.

110. Stengl, V., S. Bakardjieva, V. Kostov-Kytin, Yu. Kalvachev. 2006. Photoactive optically transparent titania nanoparticles incorporated in thin layers. 8th National Workshop Nanoscience & Nanotechnology, Sofia, Bulgaria, November 2022, poster.

111. Varblianska, K., S. Tseneva, Ph. Comninou, D. Nihtianova. 2006. Tailoring of the metal n/p type GaSb interface properties for device production. 6th Inter. Confer. of the Balkan Physical Union, August 22_26, Istanbul, Turkey, 6 O 050, oral presentation.

112. Von Quadt, A., I. Peytcheva, C. A. Heinrich. 2006. In-situ measurements (U-Pb, Lu-Hf, trase elements) in zircons to unravel the record of magmatic evolution within a Cretaceous ABTS belt. Abstract 16 V. M. Goldschmidt Conference, August 27 September 1, Melbourne, Australia, CD version.

113. Wang, X. J., A. Klocke, B. Mihailova, R. Stosch, B. Güttler, U. Bismayer. 2006. Effect of bleaching on structure of enamel. 14. Jahrestagung der DGK, Freiburg, April 3-6, poster.

114. Wang, X., A. Klocke, B. Mihailova, R. Stosch, B. Güttler, U. Bismayer. 2006. Effect of bleaching on dental hard tissues, BIOCERAMICS 19. 19th Inter. Symp. on Ceramics in Medicine, The Annual Meeting of the International Society for Ceramics in Medicine (ISCM), Chengdu, China, October 10-13, poster.

115. Wallau, M., L. D. Dimitrov, C. R. da Silva, E. A. Urquieta-Gonzalez. 2006. Sequential nano-casting of MCM-41 micro-spheres for mesoporous ZSM-5 preparation. 9th Nat. Catalysis confer., Bulg. Catalysis Club, November 15, Sofia, Inst. of Catalysis-BAS, p. 41.

116. Yoleva, A., O. Petrov, S. Djambazov, O. Malinov, D. Stoycheva 2006. Clinoptilolite in volcanic neck structure near Kralevo deposit, Haskovo region (Bulgaria) 7th Inter. Confer. on the Occurrence, Properties, and Utilization of Natural Zeolites, July 1621, Socorro, New Mexico, USA, Extended Abstracts, 256-257, poster.

117. Zhang, S., A. Klocke, B. Mihailova, B. Gasharova, B. Güttler, R. Stosch, U. Bismayer. 2006. Laser-Induced Structural Changes in Dental Enamel. 14. Jahrestagung der DGK, Freiburg, April 3-6, oral presentation.

118. Zidarova, B. 2006. Nanosized fenomena in minerals. Personal report at the Open Joint Meeting of the National Coordination Council on Innovation and National Coordination Council on Nanotechnology, June 30, BAS.