BULGARIAN ACADEMY OF SCIENCES

 

CENTRAL LABORATORY
OF MINERALOGY AND CRYSTALLOGRAPHY

ANNUAL REPORT
No 9/2003

 

Editor: Dr. Nikola Zidarov; E-mail: nzidarov@interbgc.com
© Central Laboratory of Mineralogy and Crystallography, 2004
ISSN 3033-2206

CONTENTS

Project No 21 is financially supported in part by the Bulgarian National Science Fund of the Ministry of Education and Science. Project No 13 is financially supported by NATO's Lincage Grant. 

INTRODUCTION

This annual report presents the activities of the Central Laboratory of Mineralogy and Crystallography during the 9th year of its existence. The topics developed were in accordance with the preliminary specified scientific and applied priorities. The most significant scientific results, part of which already published or reported at conferences can be grouped as follows: The most important achievements of practical character are: The most important results obtained in the framework of the international collaboration of CLMC are: During 2003 the activity in CLMC was concentrated in 8 projects financed by the budget of the Bulgarian Academy of Sciences, a project additionally financially supported by the National Council for Scientific Investigation, a project with NATO, four problems in the framework of the international collaboration, and 4 contracts with organizations in Bulgaria and abroad. The scientific results achieved by the stuff of CLMC in 2003 are reported in 75 publications in scientific journals and series, 48 of which in international and foreign journal and proceedings, and 27 in Bulgarian issues. The already published papers are 52 in number, whereas those in press 23. Our colleagues have given 31 reports in international and local conferences and symposiums. In March 2003 a scientific session "Scientific and applied achievements of CLMC-BAS' 2003" was carried out, in the course of which the activity in scientific projects worked out in the period 2000-2003 was resumed. The session was opened for all institutions in BAS and for Universities of similar topics, and 17 plenary and 23 poster reports were given, covering thematically 9 projects supported financially by the budget of BAS as well as NATO, National Council for Scientific Investigation, and other organizations in Bulgaria.

Nikola Zidarov 
Sofia, January, 2004

RESEARCH TOPICS:

I. MINERAL SYSTEMS AND ISOTOPE GEOCHEMISTRY

1. Mineral-petrological, geochemical and isotope studies of geological units in Serbo-Macedonian Massif, SW Bulgaria (N. Zidarov, I. Peytcheva, A. v. Quadt, V. Andreichev, L. Macheva, R. Titorenkova)

Two facial metagranitoid varieties are distinguished in the NE part of Serbo-Macedonian Massif (Ograzhden and Maleshevska mountains, SW Bulgaria): equigranular and porphyritic. They are deformed, metamorphosed (amphibolite facies overprinted at 650 °C and 7-8 kbar) and migmatized unevenly with augen, augen-layered or layered structures. Less deformed parts reveal magmatic peculiarities, such as micro-granular enclaves, zonally arranged plagioclase inclusions in potassium feldspar porphyroclasts and foliated aplitic and pegmatitic dykes. Our previous U-Pb zircon data (using ID-TIMS techniques) have defined an age of 459.9 ± 7.6 Ma (MSWD 1.17) for the equigranular metagranites and 451 +18/-9 Ma (MSWD 0.24) for the porphyritic one (Ann. Rep. 8/2002)

Fig. 1. Rb-Sr isotope diagram for equigranular and porphiritic metagranites of the Ograzhden and Maleshevska mountains
Fig. 2. Concordia diagram for zircons and sphene
of the leucosome sample A-4, Ograzhden mountain

Rb-Sr analyses of samples from both, equigranular and porphyritic varieties, yield an errorchrone, with a slope corresponding to 441 ± 170 Ma (Fig. 1). As the U-Pb zircon isotope system is much more reliable in metamorphic terrains, we interpret the scattering of the data points in Fig.1 as caused by high-grade metamorphism, although inhomogeneities of the granitic magma in Ordovician time can not be excluded [50].

New U-Pb isotope investigations were carried out on accessory minerals separated from plastically deformed aplitic and leucosome veins [101]. Unfortunately, none of the studied samples contains monazites, which are very indicative in high-grade overprinted terrains. The reason is that monazite (a light rare earth elements (REE) phosphate mineral with idealized formula CePO4) occurs commonly as an accessory phase in peraluminous melts (where Pb-isotope inheritance in zircon is substantial). On the other hand natural and experimental studies have demonstrated that monazite retains Pb up to relatively high temperatures of about 650–750 ºC. For Ograzhden leucocratic veins the lack of monazite could be explained by the presence of Ca-accessory minerals, where Ca can substitute for Ca in the structure of titanite, apatite, allanite, instead of forming an own mineral.

Needle-shaped pile violet-pinkish to colourless zircons in the small fraction (75-101 mm) of the leucosome sample (A-4) were used for U-Pb single grain analyses in order to avoid inherited cores. Some of the grains are additionally abraded to remove the outer parts, which are usually disturbed by the overprinted metamorphism. On the concordia diagram, the zircons define an upper intercept age of 461 ± 18 Ma (MSWD 0.79), which coincides, within the errors, with the crystallization age of the metagranites. The U-Pb isotope analysis of one sphene fraction gives evidence for Alpine metamorphic overprint, lying on the same discordia line being close to the lower intercept with the concordia (lower intercept "age" of 125 ± 66 Ma). The rutiles of the same sample, A-4, cannot be dated due to the low uranium and radiogenic lead contents.

Fig. 3 Distribution of trace elements in samples from Ograzhden and Maleshevska mountains normalized to such of the continental crust. Legend: filled symbols – porphyritic metagranites (mGr); empty symbols - equigranular mGr; gray symbols – leucosomes in the porphyritic mGr; asterix - aplitic vein in the equigranular mGr. Fig . 4. Chondrite normalized REE distribution in samples from Ograzhden and Maleshevska mountains. Symbols as in Fig. 3.

LA-ICP-MS chemical analyses of 7 whole rock (WR) samples, MC-ICPMS Hf-zircon isotope analyses of some dated zircons as well as WR Sr-isotope data are used to characterize the chemical composition of metagranites and veins in Ograzhden and Maleshevska mountains and to constrain their magma sources. Recently measured e-Hf (460 Ma) in zircons in leucosome A-4 varies between – 0.42 and – 0.53 and indicates a mixed crustal-mantle source of the melts. Zircons from the metagranites exhibit similar Hf-isotope characteristics. These data suggest island-arc or post-collisional geodynamic environment, as it was supposed based on some tectonic discrimination diagrams (for example Rb/Zr vs SiO2). Additional arguments for such a conclusion is provide by the Ta-Nb negative anomaly in the normalized distribution of the REE in the continental crust for all samples studied (Fig. 3). Chondrite-normalized REE distribution resembles closely that of typical island-arc calc-alkaline rocks with patterns enriched in LREE and depleted or flat in HREE (Fig. 4). It is worth to note that the lower contents of REE in the vein varieties M73 and A5 are accompanied with a lack of Eu-anomaly. These data can be interpreted as characteristic of not differentiated magma, without plagioclase fractionation.

Further information about the magma sources provides the initial strontium ratio, which when corrected for 460 Ma, changes in the range 0.7075-0.7099 in porphyritic samples and between 0.7080-0.7144 in the equigranular varieties with an average of 0.7109 ± 0.0062 (Fig. 1). These values hold for mixed, but crust dominated source of magma.

Obviously, the source characteristics of the metagranites in Ograzhden and Maleshevska mountains preserve some of the geochemical signatures of the older crust containing possibly both upper and lower crustal as well as mantle fragments inherited in the Ordovician magma.

2. Isotope-geochemical and geochronological investigation of magmatism and related ore formations in Srednogorie zone (I. Peytcheva, A. v. Quadt, B. Kamenov)

The potential usage of radiogenic isotopes in studying ore-forming processes has been recently studied by many authors. Two are the primary types of information available from these studies: age determination and isotopic source tracing. In the frame of the GEODE (Geodynamic and Ore Deposits Evolution) project of ESF (European Science Foundation) and in cooperation with many colleagues we applied a combination of radiogenic methods to studying economically important deposits of Cu (Au) in Central Srednogorie. Here we present isotope data on two pairs of deposits, the Elatsite Cu-porphyry and the Chelopech epithermal ones, cropping out in the northernmost part of Central Srednogorie, and the Vlaykov Vruh Cu-porphyry and Elshitsa epithermal deposits in the southernmost part of these zone. They provide a good opportunity for studying the genetic relationships between magmatism, alteration and ore formations.

The following combination of methods was used in this study: (1) precise single zircon U-Pb (TIMS) dating of magmatic events bracketing the ore-formation; (2) Rb-Sr, Sm-Nd whole rock and Lu-Hf zircon isotope geochemical analysis of source constraints. At Elatsite deposit the ore mineralization is confined by individually dated igneous events, indicating that the entire time span of the ore-forming magmatism and hydrothermal activity extend over a maximum duration of 1.1 Ma, but is probably much shorter (Ann. Rep. 8/2002).

The Chelopech volcanic complex, hosting one of the largest Au-Cu epithermal deposits in Europe, includes three phases: (I) dome-like bodies (andesites and latites to trachydacites), (II) lava to agglomerate flows (andesites, latites, dacites to trachydacites), and (III) lava breccia neck (andesites to shoshonites and latites). Based on the field position and relation to the sediments, alteration, and mineralization one can supposed that the first phase represents the pre-ore stage (as compared to the epithermal Au-Cu deposit), whereas the second one is the most important stage for the ore formation. The final third phase of the Chelopech volcano is barren.

According to new U-Pb zircon data, the magmatic activity had started at the northern border of the Chelopech region with the intrusion of the dome-like bodies at T=92.3 ± 0.5 Ma [35]. The products of the second and the third phases followed so close to one another that they are undistinguishable within the error limits: U/Pb analysis of zircon of representative samples yield an intrusion age of 91.3 ± 0.3 Ma (Fig. 1). For starting of the economically important ore-producing magmatism we prefer to use the mean value of age 206Pb/238U = 91.47 ± 0.15 Ma of zircons from hydrothermal brecciated, altered and mineralized andesite, sampled in the Chelopech mine. Thus, the ore-important magmatism had started some 91.6 Ma age or 91.62 Ma age and had finished at about 91.0 Ma age.

It was found that Sr and Nd isotopic compositions in Elatsite and Chelopech deposits are close to each other [105] that suggests a mixed mantle and crustal source of the Cenomanian-Turonian magma. The values of e-Hf (90) in the concordant zircons confirm this conclusion. In Chelopech the assimilation of upper crustal material was more pronounced in the volcanites of the second and third phases. Therefore, nor the isotope geochemical characteristics, neither the age determinations discards a model for a common magmatic chamber for both deposits.

Fig. 1. U-Pb concordia diagram for zircons of the andesitic lava breccia neck representing the III- rd phase in the Chelopech volcanic complex. Fig. 2. U-Pb concordia diagram for two rutiles from the Vlaykov Vruh porphyry copper deposit.

In Elshitsa and Vlaykov Vruh deposits we couldn't identify magmatic bodies (dykes), which crosscut the economically important ore mineralisation. Thus we had to change the approach, using direct dating of hydrothermal minerals - molybdenite (Re-Os isotope method) and rutile (U-Pb isotope method). In the region of both deposits the oldest volcanic rocks are the Amph-Px andesites. They are overlaid by dacitic lava flows and ash tuffs and are crosscutted by subvolcanic dacitic bodies and diorite porphyritic dykes. The porphyry copper deposit Vlaykov Vruh is hosted by subvolcanic granodiorites.

Zircons of the Elshitsa granite, representing the plutonic part of the magmatic system, reveal an intrusion age of 86.62 ± 0.02 Ma [36, 35]. An age of 86.11 ± 0.23 Ma was obtained for the Elshitsa subvolcanic dacites. The e-Hf (86) values of the concordant zircons range from +6.05 to +8.74 and give evidence for a mixed crustal-mantle origin of the ore-bearing magma. They are in agreement with the initial strontium characteristics, which change in all studied acid rocks in a narrow range between 0.70514 and 0.70583. Similar Sr and Hf-zircon isotope characteristics, additional to the close ages, argue for a common magma chamber of all acid rock varieties in the Elshitsa and Vlaykov Vruh deposits.

The mean 206Pb/238U-ratio of high-temperature hydrothermal rutiles from Vlaykov Vruh define an age of 85.65 ± 0.15 Ma (Fig. 2). This age indicate probably the onset of the hydrothermal mineralisation. The Re-Os isotope dating of a molybdenite from the same stage of mineralisation in Vlaykov Vruh reveals an age of 85.2 ± 0.5 Ma. Low-temperature anatases from epithermal ore bodies in Elshitsa were not suitable for U-Pb analyses, because of the low uranium and radiogenic lead content. For dating the epithermal mineralisation we need to apply additional 40Ar-39Ar measurements of potassium-containing minerals, which are common in the alteration zones of hydrothermal deposits.

As shown above, the combination of isotope-geochronological and isotope–geochemical investigation, is a powerful tool to establish the age relationships between hydrothermal systems and associated lithologies, or the history of the systems themselves, and to delineate the sources of certain components within the system in terms of likely reservoirs.

3. Isotope geochemistry and timing of fluorite deposits in Bulgaria (B. Zidarova, I. Peytcheva, N. Zidarov)

The Bulgarian industrial fluorite deposits (Chiprovtsi-East, Slavyanka, and Mikhalkovo) have been well studied concerning their chemical and mineral composition, texture, and the processes of mineral formation. The results are used for developing local (Ann. Rep. 1/1995; 6/2000) and common [75] geogenetic models.

For timing of these deposits we used up to now the relations between fluorite bodies and geological units of well-constrained age. The formation of Mikhalkovo deposit is connected with the Upper Oligocene rhyolite volcanic activity of Bratsigovo-Dospat massif (about 31 Ma, K/Ar data, Pecskay, Harkovska-private communication). Our geological investigations give also evidence that there is a genetical relationship of Slavyanka deposit with the post-volcanic hydrothermal activity of the dacitic volcanites in Ograzhden Mountain (30-32 Ma, K/Ar data – Ann. Rep. 7/2000). For "Chiprovtsi-East" fluorite deposit, like the others deposits in the Chiprovtsi fault zone, published works assume a mineral formation related with the Sveti Nikolski granite pluton, the age of which has been determined recently as Carboniferous by the U-Pb zircon method (313.8 ±3.5 Ma). Based on our field observations, we presumed a younger (Alpine age) for this fluorite mineralisation.

Our preliminary isotopic data are as follow:

For Slavyanka deposit:Ten samples of hydrothermally altered rocks from Vodena Skala mine, leveled at 40, 80 and 385 m, were investigated using the K/Ar method (V. Andrejchev, Komi, Ural branch of RAS). Three samples of sericitized gneisses were aged of 29±1 Ma. This age is about 2 Ma smaller than that of the acid effusives in the region. The calculated ages based on 7 muscovite samples separates from the altered gneisses vary from 209 to 166 Ma. They could not be related to real geological processes and result probably from radiogenic loss of Ar without any isotope homogenization in the isotope system.

For samples from Chiprovtsi-East deposit, Lukina Padina mine (earlier distinguished as four genetical type, Ann. Rep. 2/1996) we applied the Sm/Nd and Rb/Sr isotope approaches (A. von Quadt, I. Peycheva, ETH-Zuerich). The data confirm our idea for an Alpine age of the fluorite formation (164±27 Ma - Sm/Nd method).

The 87Sr/86Sr and 143Nd/144Nd isotope ratios of the same samples give evidence for a crustal dominated source of the hydrothermal solutions (Fig. 1). The values are not very radiogenic, which is explained with the mantle-crustal origin of the hosting rocks (diabases and marbles). Further Sm/Nd and Rb/Sr investigation of the latter would help to estimate their effect on the hydrotherms from which the fluorite had been crystallized.

The distribution of REE in the fluorites of the studied deposits is considered as indicators for formation of minerals under specific P-T conditions [51].

Fig. 1. 87Sr/86Sr vs. 143Nd/144Nd diagram for fluotite
samples of Chiprovtsi East deposit. EM1 - enriched
mantle 1 field of Hart and Zindler, 1989.


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

The Pb isotope composition of galenas from various types of primary ores (siderite, barite, polymetallic) from the Kremikovtsi deposit is studied. The obtained data are analogues to the known so far single analyses of samples from this deposit. The analysis of the results and their comparison with those for other deposits in the region and all over the world makes it possible the following main conclusions to be made:

5. Isomorphic substitutions and petrogenic significance of allanite-(Ce) from Skrut's porphyric granitoids (Belassitza Mt., Serbo-Macedonian Massif) (E. Tarassova, M. Tarassov)

Allanite-(Ce) is a typical accessory mineral in Skrut's granitoids formed on the earliest stages of the magmatic crystallization and it is the major repository for REE, U, Th, and Y in these rocks (up to 25 wt.%). Two types of allanite were recognized by us using petrography, crystal chemistry, and microstructure criteria, namely: allanite (I) is the early variety presented by euhedral crystals with comparatively low content of Th (ThO2 0.8-1.8 wt.%) and allanite (II) - later variety of the mineral characterized by randomly shaped crystals, containing a much higher content of Th (ThO2 2.1-3.9 wt.%).

Figure 1 shows chondrite-normalized REE patterns of the allanite studied, which indicates that the later allanite (II) had been crystallized in media with much lower concentrations of heavy REE than the characteristic one for allanite I. This trend of behavior of REE in the melt during the crystallization of both types of allanite could be related to the fractional crystallization of zircon, which decreases the content of heavy REE in the melt. Another reason for this phenomenon can be searched in the principle chemical difference between the melt producing allanite I and allanite II. Indeed, the diagram proposed by Broska et al., the sum (REE+Y+Th+U) vs. the total Al in apfu, differentiates well the two types of allanite: the points corresponding to allanite I fall in-between the regions typical of A- and I-type granitoids, whereas those of allanite II lie in the intermediate region between I- and S-type granitoids. All these findings indicate that the chemical composition of allanite I and II fluctuates due to the varying composition of the parent magma (caused by the differing participations and heterogeneities of different protholite components) and due to fractional crystallization [39].

Critical survey of the allanite compositions, obtained by us, as well as those taken from the literature, shows that the classical scheme for the pair isomorphic substitution,

Fig. 1. Chondrite-normalized REE patterns of allanites from Skrut granitoids.


(1)

is not sufficient to explain the composition variations in the mineral. It is shown that several additional schemes of isomorphic incorporation of REE should also be taken into consideration, namely:

(2)

(3)

The validity of the heterovalent isomorphism ascribing the insertion of Th and U in the structure of allanite,

(4)

is critically discussed and some reservations are proposed. Although, the presented scheme (4) seems to be an appropriate model for the distribution of Ca, Th(U), and REE in the allanite crystals, reported in the literature (a simultaneous increase in the content of Ca and Th(U) and a decrease of that of REE in the rims of crystals), some discrepancies exist concerning this scheme and the total correlations between Ca, Th(U) and REE. The first one is that the variations in the content of Ca and REE are well correlated with the isomorphic schemes (1-3), all atomic quantities and charges of the components being well balanced. The second one is related to the experimentally proved fact that a negative correlation exists between Ca and Th(U) contents, rather than that between REE and Th(U). Based on these considerations, the following possible schemes for the isomorphic incorporation of Th and U are proposed:

(5)

(6)

Schemes 2 and 5 emphasize the specific implication of the hydrogen fugacity f(H2) in magmas during the allanite crystallization, a problem recently discussed in literature.


6. A new deposit of celestine in the Low Cretaceous sediments near Krousheto village, Gorna Oryahovitza district, Bulgaria (I. Donchev, N. Lihareva, Y. Tzvetanova)

This deposit of celestine is localized in the Baremian-Aptian sediments of Gorna Oryahovitza formation along the right bank of Yantra river near to it confluence Rositsa river (Fig. 1).

Fig. 1. Geological map of the region of the celestine deposit scaled M 1:100 000 (sheet Veliko Tarnovo) and the points of sampling (1-5); rmK1a–ab – Roman formation; gK1h–a – Gorna Oryahovitza formation

Fig. 2. Parallel-fibrous (a) and veinlets with crystalline celestine in aleurolites (b).

The cross-section is in the upper part of the formation (gK1h–a) and is represented by alternating marls with fine-layered aleurolites covered with sandstones of the Roman formation (rmK1a–ab). Intersecting and layered lens-like veins with thickness up to 15-20 cm are formed among marls. Celestine is most frequently of a parallel fibrous habit and fills veinlets of thickness 4-5 cm (Fig. 2a). Aleurolites are thin-layered and on places are intersected with fine (up to 5 mm) veinlets with crystalline celestine (Fig. 2b). Corals almost totally fully pseudomorphosed by celestine are also observed.

The crystal chemical formula of celestine, Sr0.84Ba0.16SO4, indicates a high content of Ba (8.45 mass %) as evidenced by microprobe analysis. This is markedly seen in the XRD pattern of celestine, namely the d-spacings in Fig. 3 have higher values and are close to those of baritocelestine (PDF #39-1467), for which the composition is Sr0.75Ba0.25SO4.

Fig. 3. Powder X-ray diffraction pattern of celestine (Dron 3M with CoKa radiation); Cel – celestine; Cc – calcite; K – kaolinite

Fig. 4. Powder XRD of thenardite for a crystallized material from dissolved salts (Dron 3M with CoKa radiation)

The marls in the section are strongly salted and the water extract taken from a surface sample gives the following ion contents (in mg/l): K+- 11.6, Na+ - 356.0, SO42– - 826.1, Cl– - 35.8, Ca2+ - 39.1, Mg2+ - 28.0, Sr2+ - 2.46. As seen, highest is the content of Na+ and SO42–. By evaporation and crystallization, a light-yellow fine-crystalline material was obtained from this solution, with a XRD pattern (Fig.4) indicating the presence of diffraction maximums of thenardite Na2SO4.

The genesis of celestine is related to evaporite sedimentation and a subsequent diagenetic-catagenetic segregation of SrSO4 in layered and intersecting veins of crystalline or parallel-fibred celestine.

The marls in the Gorna Oryahovitza formation are of proved practical potential for building ceramics. The mineralization of celestine and salts in the deposit near Krousheto village, found by us, is an indication that they should be considered as a perspective complex mineral raw material.


7. Mineralogy of noble metals in alluvial sediments (Z. Tsintsov)

New alluvial occurrences (Qaternary and Priabonian) of platinum group minerals (PGM) are found in the regions of Dobromirtsi ultrabasic massif (Eastern Rhodopes) and Straldja graben (Eastern Sredogorie near 25-30 km S-SE from Sliven town). The MPG from Eastern Rhodopian sediments are presented by Os-Ir-Ru alloys and sperrylite, whereas those from the Eastern Srednogorie include Pt-Fe alloys only. The extremely fine grains (sized below 63 mm) and their low concentration in the sediments (less than 1mg/m3) are general characteristics of these minerals in both occurrences.

The Pt-Fe alloys are presented by nearly isometric kidney-like or drop-like grains. They have well-smoothened edges and a very high degree of mechanical processing. Their surfaces are clean, white, smooth and with a metal luster. Sometimes small caverns are observed, elliptically shaped or with partially preserved crystal faces. The PGE alloys include grains of irregular and crystalline form. Their surfaces are clean and coarse, whereas the edges are strongly smoothed in the placer. The crystals are a combination of hexagonal prism, hexagonal bi-pyramid and basic pinacoid, indicating a hexagonal symmetry. The hexagonal prism and the basic pinacoid are preserved, whereas the hexagonal bi-pyramid is very strongly mechanically processed, only separate part of it being preserved. Sperrylite is elongated and of a very high degree of mechanical processing. Its surfaces are dense, defect-free, white to dark-green, with a strong metal luster. In some parts relicts of particularly preserved crystalline faces are observed, but the strong mechanical processing does not allow their indexing.

The contents and the character of distribution of placer gold are studied in sediments known as ancient gold mining centers in southwestern Bulgaria [53]. The data show that in this region cropped out are: a) Quaternary weakly sorted, alluvial depositions along the river valleys (of the type "Uineshtitsa river") with placer gold from 15 to 420 mg m3; b) coarse, unsorted, weakly binded conglomerates (Neogene, Paleogene), a great part of which being processed in the past for gold extraction, with plenty of remainders of mining works and piles of boulders (type "Kretsul") with placer gold from 0.30 to 1.85 g/m3; and c) anthropogenic sand deposition resulting from the waste heaps from the gold processing in ancient times (type "Suho pole") with placer gold from 20 to 65 mg/m3. Nowadays, higher contents than the afore mentioned are established in the bottom of the Paleogene conglomerates (type "Kretsul"), where nuggets with weight up to 15 g can be found. It is found that about 43 % of gold grains are concentrated in the fractions below 200 mm. The thickness of sediments is different – from several tenths cm to several meters, ceaching in some parts up to above 20 m (type "Suho pole").


8. Characteristics of sulfide mineralization in serpentinized ultrabasites croped out in the region of Zhivkovo village, Central Srednogorie (Z. Tsintsov)

The sulfide mineralization represented by mono-sulfide solid solutions (MSS), pentlandite and pyrit, found in an ultrabasite body croped out at about 3 km SW of Zhivkovo village, Ihtiman district, is studied [40, 102]. The ultrabasites are irregularly serpentinized. The inner parts of the body are relatively fresher, with preserved relics from the primary rock. In its peryphery talc-chlorite, talc-tremolite-chlorite, and talc rocks are developed. The sulfide mineralization is included in the serpentinized matrix of the rock, the most widespread minerals, determining the type of the ore mineralization, being MSS and pentlandite, which in most cases are intimately crossed in complex aggregates building veinlets and irregularly shaped individual grains sized up to 0.6 x 1.5 cm. The veinlets are broad up to about 0.8 – 1.0 cm and long up to 5-6 cm. In this association MSS are dominant. Pyrite is most rarely presented and is in the form of individual grains, either irregularly shaped or with crystal form and rarely associates with Fe-oxides (hydroxides). MSS are presented by troilite and pyrrhotite (monoclinic and hexagonal), demonstrating the exsolution platy structure. The troilite studied is the first finding in host rocks in Bulgaria. Other ore minerals are observed sporadically, being represented mainly by spinelides (magnetite and chromite).

The recent data allowed us to think that only MSS and pentlandite are paragenetically related, whereas pyrite is formed under other conditions. The sporadic presence of sulfides and magnetite in the investigated body indicates locally varying conditions of f(S2) and f(O2) in the process of crystallization. The association MSS – pentlandite has probably originated under conditions of a initial hydrothermal alteration of ultrabasites. The formed exsolution structures of the two minerals show that the processes had probably started at a temperature above 300 oC. The temperature change had lead to structural modifications in the hexagonal pyrrhotite resulting in substructures of monoclinic pyrrhotite at 142 oC, when dissolution of troilite from the hexagonal pyrrhotite had occured. Simultaneously with these processes inversion in the conditions had also taken place, causing the formation of spinelides. The later stages of their sulfide transformations had led to destruction of a part of these minerals and to a further increase in f(S2) in some regions,caused the pyrite formation. The iron, necessary for forming the sulfide mineralization, had been released from the host ultrabasites. Probable sources of Ni could be the earliest formed pentlandite and Ni-containing minerals.

9. Late Alpine gold mineralizations in Eastern Rhodopes, SE Bulgaria (I. Marinova, A. Tzvetkov, O. Malinov, I. Kalinova)

Lensko and Bely Dol gold occurrences are located in the East Rhodopes between Krumovgrad and Ivailovgrad towns. This region is built up of high metamorphic rocks and Paleogene sediments, intruded by Oligocene volcanics of andesite and rhyolite composition. The Byala reka Dome, the Pelevun Thrust (taken up by S. Sarov as Late Alpine detachment fault) and the Byala reka Depression have been considered as main tectonic structures of the region discussed. The Byala reka Dome of N-S elongation is built up of high metamorphic rocks. The Pelevun Allochthone is composed of marbles, intercalated by dark-grey graphitic, dirty marbles to calc-schists and has been accepted till now as pre-Paleogene. The Byala reka Depression of E-W direction is filled in with sediments of large age range (Maastrichtian – Middle Eocene).

Three types of gold mineralization were observed in this area. The oldest one is mainly located among graphitic marbles. It consists of layers of metasomatic jasperoid and dispersed microcrystalline pyrite. Gold is established in channel samples. Ore-conducting structures are synthetic faults of the detachment fault, marked by mylonites to which the silicificated and pyritaceous rocks are attached. Clasts of this type mineralization were observed among breccias and breccia-conglomerates of the Krumovgrad group.

The second type of gold mineralization, which is of economic interest, is stockwork. The stockwork body is of NE elongation and crops out in the central part of Lensko occurrence (Fig. 1). This type of mineralization consists of quartz, adularia, carbonate, pyrite, arsenopyrite, galena, chalcopyrite, gold, and gypsum. These minerals fill microfissures, which clearly crosscut the jasperoid as well as the millimetre sized cavities among the jasperoid and the host rocks. The quartz is of several generations. The gold is present as cube-octahedral crystals sized up to 12 mm in arsenopyrite or as irregular aggregates up to 70 mm in quartz. The channel sampling revealed the presence of Au, Ag, Pb, Zn, Cu, Co, Ni, Cd, Bi, As, Sb and sporadic Mo. The mineral association and spectrum of chemical elements give us arguments to consider this mineralization as an epithermal one.

Fig. 1. Geological section across the central
part of Lensko occurence: 1 – white marbles,
2 – seams of grey, dirty, graphitic marbles,
3 – layered jasperoid, 4 – stockwork
mineralization, 5 – fault.

The electrical prospecting showed that the stockwork type of mineralization occupies knots of intersection of N-NE, NE, SE and N-S faults and fracture zones. The width of the fracture zones is in the range from 50 to 100 m. They are marked by pronounced local minima of the electrical resistance. The majority of them are probably related with the movement of Pelevun Allochthone in NE to N direction.

The third type of gold mineralization (low graded) forms thin quartz veins in post Priabonian E-NE steep normal faults in Lensko occurrence and in E-SE faults in Bely Dol occurrence southwards. Everywhere in the area these faults are vertical to south vergent and bundle-formed.

The diverse types of gold mineralization indicate that the ore-forming process in the considered area had have accompanied the Late Alpine extension of that part of Eastern Rhodopes [24 ].


10. Mineralogical map of the heavy mineral concentrates in Bulgaria scaled 1:25000 (O. Vitov)

Data on heavy mineral concentrates (HMC) samplings and investigations in Bulgaria are summarized [47]. Presented are: the map of the knowledge on HMC; a table with data for the used information from the National Geological Fund; a table of the established 92 minerals and mineral varieties as well as their statistical characteristics, on the basis of which an isonatic map is prepared for the distribution of the mineral variety on the territory of Bulgaria; a statistical analysis and a model of variation of the informational importance of the samples as function of the number of the established minerals, in which it is shown that each new mineral triples the informational significance of the samples.

Individual maps represent relationships in the distribution and HMC prognoses for survey of gold, polymetal, tungsten-molybdenum, mercury, silver, bismuth, tin, tantalum-niobium, titanium, barite, and other ore formations. Every prognosis includes a map of the material, a statistical analysis of the data, an iso-frequency prognosis for survey of deposits. For the distribution of gold, a Fourier model of distribution is prepared aiming at prospecting of gold in the stripe Vidin-Vratsa-Panagyurishte-Krumovgrad.

The necessity of HMC additional and re-sampling in the country is grounded as a whole in order to prospect in details ore deposits and to collect material for detailed mineralogical studies.

A modification of the program "REGION" is performed with the possibility to carry out large scaled Fourier analysis. The possibilities of the new model and the existing database are checked for large-scale works (M 1:200 000 and M 1:50 000). A particular metallogenic problem is solved, namely the relationship of the Paleogene magmatism and volcanic activity in Eastern Rhododpes with the formation of polymetalic and gold mineralization in the region [7, 8].

Fig. 1. Placer aureoles (grey areas) of gold within the Late Alpine Momchilgrad depression (bold contour) and its metamorphic frame. Base metal and gold mineralizations (circles), and volcanic edifice are indicated.

Fig. 2. Placer aureoles (grey areas) of barite within the Late Alpine Momchilgrad depression (bold contour) and its metamorphic frame. Base metal and gold mineralizations (circles), and volcanic edifice are indicated.

Unknown up to now facts were established on the enrichment in gold of SE metamorphic frame of the Momchilgrad depression (Fig. 1); an abundance of barite in the depression (Fig. 2) and an abundance of sheelite in the frame of the depression. In addition, chromite dispersion halo is present near to known ultrabasic bodies and in the east frame of the Momchilgrad depression. A prognosis is made for the presence of blind ore bodies bellow the barite dispersion halo in the north eastern part of the Zvezdel-Pcheloyad ore field, the presence of a paleo-placer in Djebel sandstones as well as perspectives for prospecting of sheelite ore formations in the metamorphic frame of the Momchilgrad depression. These results point at a total re-evaluation of the role of the Paleogene magmatism and volcanism in Eastern Rhodopes.The performed HMC studies indicate that in the depressions in Eastern Rhodopes of an expressed volcanic activity during the Paleogen barite and galena with small dispersion halos of gold are well-manifested. Their frames are saturated with gold, sheelite, and with sporadic occurrences of galena dispersion halos. This contrast sketch suggests also metallogenic conclusions, namely: a) perspectives for prospecting of base metal ore formations below the barite dispersion halos; b) expectation for old sheelite ore formations in the metamorphic frames of the depressions; c) the dispersion halos of gold are placed in the relatively cool frames of the volcanogenic depressions, out of the area of distribution of the base metal ore formation in Eastern Rhodopes.

A reference book "Mineralogical map of the heavy mineral concentrates in Bulgaria" is in preparation in order to summarize the newly obtained data and maps for their use for metallogenic prognoses, evaluation of the pollution with toxic and radioactive minerals and for the prospecting of mineral raw materials. 44 reference pages are sketched for minerals of the following elements: As (1); Sb (1); Ba (1); Bi (3); W (2); F (1); Cr (1); Hg (1); Sn (1); Al2O3 (2); Mn (1); Mo (1); Ag (1); Zn (1); Au (1); C (3); Cu (7); Pb (10); Ta-Nb (2) [the brackets indicate the number of minerals]. A number of 111 geomorphological maps, scaled M 1:25 000, are prepared for water sheds/ water stocks in order to assure detailed prognosis for projecting HMC maping scaled M 1: 25 000.


11. National mineralogical database: projecting and realization (N. Zidarov)

Recently, in Bulgaria there is collected an enormous massif of mineralogical information on about 760 mineral species and 400 mineral varieties. This information is collected in various sources, namely publications, reports, stock materials, etc. The last published survey "Minerals in Bulgaria" (1964) includes 350 minerals and varieties. The effective usage of this information is strongly hampered. Independently of sporadic trials by various institutions, in Bulgaria there is no yet a scientifically based systematization of the extremely diverse mineralogical data, as is the case in many other countries. This problem is of a great scientific interest and has a definite practical direction aiming at the development of estimations and strategies for developing the mineral raw basis of our country, for solving ecological problems and for integration with the existing world systems of mineralogical information.

The aim of the project is creation of a National mineralogical database (NMD) in order to collect, estimate, process, and supply already existing or new information for the Bulgarian minerals and the built by them mineral bodies. We intend this program to serve the research activity, the environmental protection and recycling, the prospecting, prognosticating and developing of the raw material resources of the country, the technological processing of mineral ores, the teaching process in high schools, mineralogical museums in the country, the Bulgarian and international mineralogical communities.

A problem of NMD is to structure the connections between its separate modules aiming at its main functions, namely registration of the old and new data for Bulgarian minerals, including its standardization and formalization, work in a reference regime, estimation of the existing information according to definite criteria, creation of new information at a higher level.

NMD will be constructed by several individual modules containing the specific information on minerals, namely: A. Bibliographic database; B. General information; C. Chemical composition; D. Morphology; E. Crystal structure; F. Properties; J. Physical-Chemical parameters of formation; H. Quantitative data for mineral raw materials; I. Technogenic mineral phases.

Basic principals in developing NMD are: smartness, compatibility, accessibility, certainty of information, hardware and system software independence, low cost of exploitation and upgrade, effectiveness with respect to information input, renewal and usage.

Stages in constructing NMD are: collection of primary information on hard copies according definite criteria and sources; development of a bibliographic database in an interactive regime on computers; building of factual database (during the first three years – a representative excerpt) including totally standardized and formalized information in separate modules.

The realization of this project in CLMC, BAS, started in 2003 by developing the bibliographic database, in which about 3500 bibliographic units were introduced. We expect the main part of this work to be finished in 2004 and the results loaded for Internet access.


12. Assessment of grid-based sampling frameworks for soil geochemical surveys (O. Vitov, I. Marinova)

The large-scale geochemical surveys are usually employed for prognoses and prospecting of ore-knots, ore-fields, and large mineral deposits. Sampling of elluvial-delluvial sediments at appropriate density and scheme is carried out, chosen depending on the shape and size of the expected geochemical anomalies. The probability for hitting irregularly shaped anomalies using given number of grid-points at a definite size of the anomalies and of the cell grid can be estimated approximately by the formulae of Shurygin:

where P(i) is the probability to hit the anomaly and i is the number of the grid-points, S is the area of anomaly and DS is the area of cell grid.

The "Monte-Carlo" approach could be applied to determining the probability P(i), which is by no means an easy task and requires the development of a method for solving the problem. This method should allow an optimal choice of the grid-based framework to be made when geochemical anomalies of definite shape and size concerned [48]. Using that method the tested frameworks are compared with four quantitative characteristics: sensitivity, selectivity, representation (i.e. statistic significance), and economic feasibility [49], the first three accounting for the probability to both hit and omit geochemical anomalies of specified parameters using different number of grid-points, while the fourth is related to the grid density.

The following orthogonal sampling frameworks were used: 500x100 m, 500x50 m, 250x250 m, 250x200 m and 250x100 m. The geochemical anomalies were selected according to their shape and size as circular (sized 600 m, 1300 m and 2600 m in diameter) and ellipsoidal (with axes ratio A/B=4 and sized 1200x300 m, 2600x650 m, 5200x1300 m), both randomly distributed as determined by a generator of random numbers. The size of the anomalies follows the Krassnikov's decimal classification and corresponds to large, middle, and small gold deposits. The direction of the long axis of the ellipsoid anomalies has been varried from 0º to 355º with increment of 5º; 100 anomalies have been simulated for each direction [48].

The method was tested for West Balkan, NW Bulgaria, on the example of Govejda gold field. These gold deposits are of vein type and the quartz-gold veins are oriented in several directions: 10-30º, 50-70º, 90-130º, 160-180º. Our results evidence that in the case the ore bodies and their hypergene anomalies are of variable direction the optimum grid is 250x250 m (16 samples/km2). The latter is the cheapest possible one, hits all circular and ellipsoidal geochemical anomalies with sufficient number of grid-points, and provides almost equal probabilities in all directions (Fig. 1, 2).

The grid 500x100 m (20 samples/km2) used now for sampling within the West Balkan at 1:50 000 scale, is more expensive than the previous one, misses anomalies parallel to the lines, and has an uneven probability distribution for hitting differently oriented anomalies (Fig. 2).

Fig.1. Histogram s of probability to hit anomalies with different number of grid-points: a, b - circular anomalies sized 600 m in diameter; c, d - ellipsoidal anomalies sized 1200x300 m in axes; a, c - at 500x100 m grid; b, d - at 250x250 m grid. Cumulative probability to hit the anomalies following Shurygin's formulae - continuous line; following “Monte-Carlo” method - dash line. The number of simulated anomalies is 7200.

Fig.2. Circular diagrams of the probability (P) to hit ellipsoidal anomalies depend ing on their direction and on the chosen grid derived from “Monte-Carlo” method. The diagram's radius is proportional to P. Grey - f ields of probable misses of anomalies; broken lines - changing of P to hit anomalies of variable direction with different number of grid-points. The number of simulated anomalies is 7200.


II. ENVIROMENTAL MINERALOGY


13. Mineralogy and geochemistry of coals and their combustion and pyrolysis products (S. Vassilev, Ch. Vassileva)

The present state of the methods commonly used for inorganic and mineral matter characterization in coal are described and summarized [43], where various separation procedures, macroscopic observations, reflected and transmitted optical microscopy, scanning and transmission electron microscopy, X-ray diffraction, differential thermal and thermogravimetric analyses, Mössbauer spectroscopy, infrared spectroscopy, and chemical analyses are briefly discussed.

The phase-mineral and chemical composition of 6 coal types and 5 fly ash types, derived from coal burning at 4 Spanish thermo-electric power stations, are characterized [42]. A scheme of conventional separation procedures (flotation, leaching, vaporization, crystallization, and magnetic separation) was applied to recover sequentially 6 initial potentially useful and/or hazardous products from these fly ashes, namely: (1) ceramic cenospheres; (2) water-soluble salts; (3) magnetic concentrates; (4) char fractions; (5) heavy concentrates; and finally (6) improved fly ash residues [42]. The phase and chemical composition and properties of ceramic microspheres and water-soluble salts [73] as well as of magnetic and char concentrates [74] were also characterized for a multicomponent, wasteless and environmentally friendly utilization of such fly ashes.

Coal, char and activated char from Spain doped with model V components (V2O5 and NH4VO3) and petroleum coke ash (enriched in V, Fe, and Ni) were prepared and characterized as potential catalytic sorbents for NO reduction. The prepared sorbents were tested for reduction of gaseous NO without [21] or with reducing agents [59]. The sorbents tested without reducing agent are active for NO reduction at temperatures above 350 °C and the most efficient sorbents were those obtained from inactivated chars doped with model V compounds or petroleum coke ash [21]. The sorbents tested with reducing agent (ammonia) are active for NO reduction at a lower temperature of 150 °C and the most efficient sorbents were those obtained from activated chars doped with model V compounds or with petroleum coke ash [59]. Despite the slightly higher NO conversions for the samples loaded with pure V components than those impregnated with petroleum coke ash, the latter catalyst is perspective for producing low-cost and effective catalyst doped activated carbons [21,59].

The general phase-mineral transformations and chemical interactions of inorganic matter during combustion of lignites (Maritza East, Marirza West, Sofia) [44] and subbituminous (Pernik, Bobov Dol) [45] and bituminous (Balkan) [45] coals from Bulgaria heated in air from 100 to 1600 °C (with the step of 100 °C) were characterized. The original minerals in coal as well as in the newly formed inorganic phases in the oxidized products and combustion residues (ashes and slags) were identified and the behaviour of minerals and phases during heating were described. Complex physicochemical transformations and reactions of various minerals and phases occur during the heating of coals. However, minerals such as pyrite, marcasite, calcite, gypsum, anhydrite, lime, hematite, and Ca silicates for lignites and quartz-cristobalite-tridymite, clay minerals, mullite, anhydrite, hematite-magnetite, and glass for higher-rank coals, play a major role for the behaviour of inorganic matter.

14. Study of partitioning of metals in ash samples using a sequential extraction procedure (N. Lihareva)

This sequential extraction procedure BCR, proposed in 1993 by the European Community's Bureau, was used to study the partitioning of Cu, Zn, Pb, Cd, Ni, and Cr in coal ashes collected from a power plant [60]. The original BCR extraction scheme was modified by adding stages of leaching with distilled water and analysing the remained solid residue after the extraction in order to calculate the mass balance. The finely accepted procedure makes it possible to study the partitioning of elements into five fractions, as follows: a) a water soluble (extraction with distilled water); b) a bound to carbonate one (extraction with 0.11 mol/L acetic acid); c) a fraction bound to Fe/Mn oxides (extraction with 0.1 mol/L NH2OH.HCl and adjusted with HNO3 to pH=2); d) a fraction bound to sulfide compounds and organic materials (extraction with 8.8 mol/L H2O2 and acidified to pH 2); e) a residual one (digestion of the solid residue with HNO3, HF and HClO4). The concentration of metals in the leaching solutions was determined by atomic absorption spectrometry and ICP-AES.

For all studied metals the level of extraction with distilled water is generally low. The main amount of total extracted Ni, Zn, Cd, Pb passes into the solution during the weak acid attack stage. The percentage of elements in the residual fraction is considerable for all trace metals and, especially for Cr and Ni. They are strongly bound to minerals and resistant components. The high proportion of metals in the residual fraction and the observed low levels of extractable metals in the reducible and oxidizable fractions indicate their low potential mobility in the environment.

The sequential extraction procedure was found to be both repeatable and reproducible. The values of the relative standard deviations (RSD), which characterize the precision, were in general below 25%. The accuracy estimated by comparing the total metal concentrations obtained after decomposition with HF and HClO4 with the sums of the five extraction steps plus the concentrations in the remaining solid residue is satisfactory. Using the methods of ICP-AES and AAS in both flame and ETAAS modes allows determining the low and high concentrations of elements in extracts.


III. MODELING AND MODIFICATION OF MINERAL SYSTEMS


15. Geometrization of the language of mineralogy: Logical analysis and mathematical formalization of the structural paradigms used in mineralogy (V. Penev, N. Zidarov, B. Zidarova)

The general (cognitive) structural paradigm is explicitly formulated and the related triad of mutually determining cognitive categories structure, composition, and construction is analyzed. Through concretizing and specifying the definitions of these categories the classical structural paradigm, which is in the basis of several natural sciences, is explicitly formulated and logically analyzed. The logical relationships between these particular forms of the classical structural paradigm are analyzed, which are in the fundamentals of chemistry, crystal chemistry and crystallography, and, consequently in the fundamentals of mineralogy. It is shown that: a) from the classical structural paradigm through adding the relatively weak requirement "the composition to be chemical" one obtains the chemical structural paradigm; b) from the chemical structural paradigm through adding the much stronger requirement for a partial or total periodicity of the construction in the ordinary physical space VE(3) one obtains the crystal chemical structural paradigm; c) if in the crystal chemical structural paradigm we reject the requirement "the composition to be chemical" and accept that the role of the composition in the considered structure is simply played by mathematical point in VE(3) one obtains the crystallographic structural paradigm.

Using the proposed original method for developing entirely mathematical and unique representations of arbitrary chemical (incl. mineral) structures (see the official site of the scientific project "Geometrization of the language of chemistry" – Main URL http://www.clmc.bas.bg/staff/V_Penev/gcl/) we were able to overcome the still existing bifurcation in the language of structural crystallography (and consequently in the language of descriptive mineralogy) between the languages of chemistry and mathematics. As an example illustrating the way of using this method the structure of rutile is represented entirely mathematically.

Table 1. Entirely mathematical and uniquie coordinate
representation of the structure of Rutile (TiO2).

In this table the following abbreviations and symbols are used: SCO – Simple Chemical Object; SSCO – Species of Simple Chemical Objects;  stands for the mathematical image with respect to KM(3) in Mendeleev's space VM(3) of the corresponding SSCO, obtained using the second generalized mathematical model (see http://www.clmc.bas.bg/staff/V_Penev/gcl/); in the symbol  – Nn stands for the number of neutrons, where Np – for the number of protons (i.e. the sequential number in the Periodic system) in the nuclei of the considered SSCO, h stands for the oxidation state of the SSCO, and k (k=1,...,32) is the number of this column in the corresponding initial form T2 of the Periodic system to which the electro-neutral atoms of the considered SSCO belong.

The Cartesian coordinates (u, v, w) with respect to KE(3) in the ordinary physical space VE(3) of the simple chemical objects building the elementary cell of rutile are as those in http://cst-www.nrl.navy.mil\lattice\struk.xmol\c4.pos. On its turn, the coordinates (z, r, j) of the corresponding SSCO with respect to KM(3) in Mendeleev's space VM(3) are obtained using the following rules: z = Nn; r = Np and j = (k - h)(2p/32), where h is the oxidation state of the considered SSCO, while k (k=1,...,32) is the number of this column in the corresponding initial table form T2 of the Periodic system to which the electro-neutral atoms of the considered SSCO belong.


16. Investigating the system Na2O - TiO2 - SiO2 - H2O (S. Ferdov, C. Lengauer, O. Petrov, V. Kostov-Kytin, Yu. Kalvachev)

Extending our previous investigations directed to optimization and control of the synthesis of microporous titanosilicates we developed a new rapid method for low-temperature synthesis of a Na analogue of microporous titanosilicate GTS-1 [54], the so-called Grace titanium silicate. Here we report a new approach for synthesising microporous titanosilicates. The synthesis of nanosized GTS-1 was performed for the first time from a sodium gel at 90 °C for 18 h without using any organic reactants (Fig 1).

By the deposition-precipitation method for loading of gold on titanosilicates ETS-4 and ETS-10 we prepared catalysts, in which gold particles are homogeneously dispersed on the surface of the supports and are with an average diameter from 2 to 4 nm. With gold deposited as fine nanosized particles over a suitable support we found that gold exhibits exceptionally high catalytic activity for many reactions. Adsorption of nitrogen oxide onto the so-synthesized nanosized gold catalysts was investigated by in-situ FTIR spectroscopy. Various mononitrosyls and dinitrosyls adsorbed species as well as nitro- and nitro-nitrito complexes were observed. The dependence of the stability of these species on time and on temperature is studied [56].

Fig. 1 Powder XRD pattern of the as- synthesized GTS-1


17. Thermal and calorimetric study of hydrotalcite phases and their transformations (N. Petrova)

The continuous interest during last few years, concerning the thermal decomposition of hydrotalcite and similar compounds, has its origin in the wide applicability of the resulting decomposition products as catalysts, ion-exchangers and sorbents. The low-temperature decomposition products are also suitable for heat-adsorbents, as shown by measuring calorimetrically the heats of sorption of water vapours [34, 94]. The heats of hydration of samples with a high content of Mg, activated at a temperature as low as 70 oC, are much higher than that of zeolites used in heat-pump systems.

The behaviour of the release of water and CO2 in natural and synthetic hydrotalcites (Mg/Al between 2:1 and 3.7:1), heated to 800 oC, was investigated by differential thermal analysis (DTA), thermogravimetry (TG) and evolved gas analysis (EGA) [69, 98]. At least six endothermic and two exothermic effects were established by computer curve resolving (Fig.1).

Fig.1. TG, DEGA curves and decomposed DTA- and DTG-curve of HT
sample with Mg/Al = 2:1 (I-IV- composed peaks; 1-8- resolved peaks)

The formation of each HT metaphase (HT-D-dehydrated HT, HT-B-partially dehydroxylated HT and MO mixed oxides with periclase-like structure) is related to the release of a discrete amount of water molecules, depending on the content of Al in the samples, and to appearing of corresponding endothermic peaks in the DTA curves. The exothermic processes, associated with the crystallization of HT-B and MO metaphases, were specified by decomposition of DTA-curves. The release of CO2 during the process of thermal decomposition of the carbonate groups is found to be different for the samples studied. The preservation of CO3, even at high temperatures, was established for synthetic samples with a high content of Al. The release of volatile H2O and CO2 (which is about 40 % of the sample mass) provokes fine cracking both along and across the layers (seen in SEM images), thus explaining of these species the substantial increase in the mixed oxide free-surface area as compared with that of the initial sample.


18. Sol-Gel preparation, modification and characterization of amorphous and crystalline WO3.xFe2O3.nH 2O phases (M. Tarassov, E. Tarassova, L. Konstantinov)

A quasi-equilibrium phase diagram for the system WO3-H2O, which specifies pH-temperature fields for the following phases WO3.2H2O, WO3.H2O, h-WO3.1/3H2O, rh-WO3.1/3H2O, WO3, and amorphous WO3.nH2O, is constructed using sol-gel experiments in the temperature range 25-160 oC, pH form 0.3 to 4.0, and total concentration of tungsten 1 mol/(H2O kg). It is shown that upon doping with ferric iron crystalline phases are WO3.H2O and h-WO3.1/3H2O with Fe/W<0.1, formed at pH<1.0 and temperatures above 50 oC, while the other WO3.xFe2O3.nH 2O products are amorphous being either of metatungstate-like (at t<50 oC) or of WO3.1/3H2O-like (at t>50 oC) type gels, independently of pH and for Fe/W>0.1. All the synthesized WO3.xFe2O3.nH 2O materials were modified through heating and simultaneous treatment by various solutions. It is found that when the solutions are tungsten-free the same phases as those in the direct sol-gel process are formed, whereas if the solutions contain tungsten, a pyrochlore-type (W,Fe)(O,OH)3 is formed [38, 70, 99].


19. Mechanochemical activation of pyrite concentrate (D. Kunev, D. Paneva, V. Petkova, E. Manova, I. Mitov, I. Dombalov)

The products of mechanochemical treatment of pyrite concentrate are studied using Mössbauer, X-ray spectroscopy, and thermal analysis. The results obtained are ecologically important and provide information on the conditions and methods of processing of metallurgical waste concentrates [20].

As a result of this study it was found that:

Fig.1 Mössbauer spectra of non-activated and activated samples

Fig. 2 DDA, TG and DTG curves of samples activated for 36 min

20. Mass-transport phenomena in silicate melts under external fields (N. Zidarov, J. Mouchovski, M. Tarassov)

In investigating electrochemically induced mass-transport in anhydrous basaltic melts (Ann. Reports N 5/1999, 6/2000, 7/2001, 8/2002), a new series of experiments were performed to clarify the polarization effects and the reduction kinetics on the mass-transport in the melts under a constant external electric field.

Using a specially designed apparatus, a high-temperature voltage-measurement was carried out, combined with a fast cooling of the melt to produce a "freezing" profile. The starting material (preliminary baked and grounded basalt from Bukovo deposit, Bulgaria, with a content of SiO2 of about 44 wt.%) was loaded in uniform rectangular electrochemical cells of corundum (the cell constant being 0.0127 cm–1) and equipped with two-plate Pt electrodes providing a homogeneous electric field. The following parameters were varied: temperature from 1100 to 1430 ºC; external potential from 0 to 5 V, and duration from 0 to 25 h. The electric current was measured by a period from 0.33 to 600 s. When the cells were drown out of the hot zone the cooling rate reduces only by 0.3 K/s (from 2.5 to 2.2 K/s) during the first 70 s till reaching the glassy state at 1170 ºC.

In processing the experimental data we took into account that the constant external voltage is distributed between the voltage on the resistance of the used highly sensitive ammeter (11.3 W) and that on the cell, which is a sum of the ohmic drop on the melt in the cell and the cell polarization, Dz, which at given temperature depends on the current density, i.e. on the amplied external voltage. It is determined by a sharp switching on and off of the external voltage, while the opposite (negative) current through the cell in the initial moment (Iin) and after the standard potentials on the electrodes (Istat) have been reached, the difference, Iin - Istat, multiplied by the melt resistance at a given temperature, T, results in the total electrochemical cell polarization Dz at the given voltage Ucel. It is seen from the dependence of the total polarization vs. voltage, Dz = f(Ucell), that at Ucell = 1V Dz = -90.4 mV, i.e. the ohmic drop on the melt in the cell is 91% the applied voltage. A higher cell polarization is determined from the Volt-Amper characteristics at T=1617 K, namely Dz= -146 mV (at a scanning rate of 355 mV/s) and Dz= -151 mV (at 513 mV/s). Both, these differences and shape of the curves obtained show the importance of the kinetic stage of the reduction on the cathode. Accounting for the polarization effect in the cell we found the temperature dependencies of the specific conductivity s and of the viscosity h (Fig. 1) of the basaltic melt upon an external field of intensity E=1.88 V/cm. The temperature varies between 1570 and 1623 K at an approximately constant rate of heating (9.2–9.6 K/min), where a quasi-stationary state of mass-transport process is supposed. From the obtained straight lines the values of s and h at 1603 K (s=1.12.10–4 W·cm–1 and h=1188.5 Poase, at 0.1 MPa) were specified. Further, from the slope of these straight lines we calculated the activation energy of the two processes DEs=47.17 Kcal/mol and DEh=48.2 Kcal/mol, while the intercepts define constants representing values at infinite temperature (lgso=2.477 and lgho=-3.499). The so found constants are very close to those quated in the literature for basaltic melts of a similar composition and confirm the Frenkel theoretical dependence: hsn = const or lgh= lgho + n·(lgso - lgs). Here, n= (DEh/DEs) = 1.02, i.e. the activation energy of the viscous flow is a bit higher than that of the electrical conductivity.

Fig.1. Viscosity – temperature dependence for basaltic melt imposed under external electric field with E=1.88 V/cm and temperature ramp 9.8 – 9.3 K/min Fig.2. Partial current density – time dependence for Fe cations in basaltic melt at 1604 K imposed under external electric field with E=1.65 V/cm

Upon electrolysis of the basalt melts studied the mass transport becomes stationary after about 80 s. Before this time the temporal dependence of the partial current density obeys the theoretical expression obtained as a solution of the differential equations describing the non-stationary mass transport in fluid systems under the action of gradients in concentration and in the applied external electric field in the approximation of the effective binary diffusion coefficients. Using this theoretical expression to fit the experimental points for iron ions with three parameters (Fig. 2) one obtains: zFe = 2.872, CFes = 7.38 wt.% and DFe = 7.41·10–8 cm2/s. The number of exchange electrons zFe is less than 3 as a small part of the iron ions are bivalent. The concentration gradient, CFeo - CFes, is only 0.24 wt. %, which indicates the existence of diffusion restrictions for the mass-transport of iron ions far from the limiting boundary diffusion current. The value of the effective diffusion coefficient of the DFe3+ is close to that found from the fit of the experimental points to the distribution of iron in the near cathode region (9.1·10 –8 cm2/s). Both values are lower by about 50% of those equated in the literature. This can be explained by the relatively low value used by us for the Fe-ions transfer number (tFe=0.057) calculated using the Richter's model, since some authors consider that the transfer numbers for cations in silicate melts should be significantly higher.

When analyzing the results obtained in fitting the temporal dependence of the partial current density to the concentration distribution near to the cathode one should accounted for that the migration/diffusion ratio is proportional to zi/T. Thus, the melt viscosity increases drastically when the temperature approaches that of the glassy state and one should expected a significant increase in the relative effect of migration as compared to the multi-component diffusion. This should be kept in mind when modeling the mass-transport in magmatic melts upon electric potentials, which can explain the distribution of the melt compounds.

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


21. Local structure and phonon anomalies in inhomogeneous oxide materials. Lead-based relaxor ferroelectrics. (B. Mihailova, L. Konstantinov)

Due to their extraordinary dielectric properties relaxor ferroelectrics have a wide application in various devices and are of great technological interest to be used for high-speed storage and processing of information. The unique macroproperties of relaxors are related with the complexity of their nano-scale structure. The nanometer structural peculiarities in relaxors of the type PbSc0.5B"0.5O 3 (B"=Nb,Ta) were studied using polarised Raman spectroscopy [10, 25]. The temperature evolution of the phonon anomalies was investigated on the basis of calculated modes of representative structural units. It is shown that on a nanometer scale – doubling of the perovskite structure always exists and it is related to ordering in the O-sublattice rather than to B-site ordering. The electron lone pairs of the Pb2+ cations promote electron-phonon coupling, thus leading to off-centred structural fluctuations. When the temperature decreases different structural changes are preferential depending on the type of B"-cations. Hence, different mechanisms of formation of the ferroic state are realized: for B"=Nb uncorrelated distortions of Pb-BO3 species result in isotropic polar clusters; for B"=Ta the correlation in the out-of-plane shifts of Pb atoms gives rise to highly anisotropic incipient domains. The type of preferred structural transformation should depend somehow on the affinity of B'/B" cations to form a solid solution or to order in a periodic network. In PbSc0.5Ta0.5O3 a rhombohedral-to-monoclinic phase transition, accompanied by unit cell doubling, occurs near 180 K. In PbSc0.5Nb0.5O3 lowering of the translation symmetry occurs near the Curie point and additional unit cell multiplication is realized. The comparison between the temperature dependence of the inelastic light scattering in stoichiometric and Nb-doped PbSc0.5Ta0.5O3 shows that the presence of Nb even in small concentrations affects the Pb-O sublattice and changes the direction of the local structural transformations, i.e. the dominant type and the size of ferroic nano-metric domains may be governed via suitable doping of the crystallographic B-position.


22. Hydrothrmal synthesis of microporous phases in the system Na2O - Ba2O - ZrO2 - SiO2 - H2O (V. Kostov-Kytin, S. Ferdov, U. Kolitsch, O. Petrov, C. Lengauer, E. Tillmanns)

Low temperature hydrothermal synthesis in the system Na2O - Ba2O - ZrO2 - SiO2 - H2O was carried out without organic additives to the synthesis mixtures. The crystallization fields of the following known and new phases were outlined in the Zr-containing system without Ba sources: zircon ZrSiO4; gaidonnayite Na2ZrSi3O9.2H 2O; a synthetic phase, Na2ZrSi3O9.H2 O; kenyaite NaSi11O20.5(OH)4.3H 2O; a zirconosilicate phase with the empirical formula Na2.8Zr6.5Si2O 17.8, without solved crystal structure; and two new zirconosilicate phases without known structural analogues, characterized only by powder X-ray diffraction and by thermogravimetric and differential thermal analyses (TG-DTA). With BaCl2 used as a reagent in the Zr-system we obtained single crystals (Fig 1.) of a new microporous zirconosilicate, Ba2Na(Na0.5,(H2O) 0.5)2Zr2Si6O 19·3H2O, named MCV-2 (Mineralogy and Crystallography Vienna).

Fig. 2. Crystal structure of MCV-2


Fig.1. SEM image of MCV-2

This phase is the first example of a Ba-Na-zirconosilicate and has a crystal structure, which is unique among the mixed octahedral - tetrahedral framework types. The crystal structure of as-synthesized phase is solved in the orthorombic space group Cmca (no. 64), with a = 16.258(3), b = 20.806(4), c = 12.339(2) Å, V = 4173.8(13) Å3, Z=8. The complex structure consists of isolated ZrO6 octahedra sharing all their corners with trisilicate groups and six-membered rings of SiO4 tetrahedra to form channel systems oriented approximately parallel to [100] and [110]. The channels are filled with one non-equivalent (ten-coordinated Ba2+ ion), two Na+ ions (eight- and four coordinated) and two water molecules (Fig. 2) [78].


23. Application of Raman spectroscopy in structural characterization of opals (A. Ilieva, B. Mihailova, O. Petrov)

The structural state of microcrystalline varieties of hydrous SiO2 is complex and has not yet been entirely resolved. Hydrous SiO2 phases are widely spread in the volcano-sedimentary rocks and are closely related to the diagenetic alteration and the processes of devitrification. Thus, it is very important to characterise precisely the structural state of these phases. The present study is an attempt to resolve the structure of opaline silica from various levels of the Palaeogene volcano-sedimentary complex of East Rhodopes. Several samples from opal siliceous rocks and bentonite clays have been analysed by powder X-ray diffraction (XRD), scanning and transmission electron microscopy, differential thermal analysis, and Raman spectroscopy. The results show that the opals from the pure opal siliceous rocks are in fact tridymitic. Their XRD patterns are of the opal-CT type, but the Raman spectra obtained from the same samples reveal the predominance of tridymitic domains. Using a micro-Raman spectroscopy analysis it is proved that the structure of the so-called lepispheres, typical of most opaline silica, is related to monoclinic-tridymite (Figs.1, 2). Our data show that opal in the opaline samples studied can be considered as of the opal-T type [80].

Fig.1. SEM micrograph of lepisheres. Fig.2. Raman spectrum of lepispheres (upper plot) compared to the spectrum of monoclinic tridymite
(lower plot).

24. TEM study of structural transformations in potassium feldspars from Biala reka metagranitoids, East Rhodopes, Bulgaria (D. Nihtianova, L. Macheva, U. Kolb)

Potassium feldspars from heterogeneously deformed metagranitoids (the region of Biala reka, East Rhodopes) are studied by TEM (bright field electron micrographs and selected area electron diffraction - SAED). According to powder X-ray diffraction data the studied potassium feldspar samples are represented mainly by their monoclinic modification - orthoclase with a low degree of triclinity (Dz in the range 0.48-0.71). Twenty two crystallographic sections, including the main three, [001], [010] and [100], were registered in TEM for both orthoclase and microcline. The TEM experimental data are in a good agreement with the theoretically simulated electronograms. Three types of diffraction patterns were established, such of: 1) orthoclase; 2) "tweed" orthoclase and 3) ordered microcline. Predominant is the so-called "tweed" orthoclase, its diffraction pattern revealing diffuse streaks parallel to both a* and b* axes in a*b*- plane (from barely visible to well developed, Fig. 1).

Fig.1. “Tweed” orthoclase diffractions with a) diffusion streaks along b* and b) diffusion streaks along a* and b*

a b

This "tweed" orthoclase is built of triclinic microcline domains, preserving as a whole its monoclinic symmetry and is characterized by the presence of diffuse streaks of individual diffraction spots crossing the reflexes either in one or two mutually perpendicular directions. Simultaneously, domains of microcline are observed in one and the same morphological unit. In the triclinic modification of K-feldspar the twinning elements (010) and [010] are deviated by 3.5o from the orthogonal case and their bright field images are characterized by a fine scaled cross-hatched microtexture (Fig. 2).


Fig.2. Bright field image of fine scale “tweed” orthoclase

Electron diffraction data show that the structural transition "tweed" orthoclase – ordered microcline is met only in some crystallographic directions, most probably related to regional tectonic strain directions.

The theoretically generated electron diffractions of orthoclase and microcline (in a reduced cell) show their coincidence in the following crystallographic directions:

A possible way for interpretation of these results is the topotaxic growth of the "tweed" orthoclase onto the primary magmatic orthoclase, which, in its turn, is transformed into triclinic microcline domains being energetically most advantageous. In more deformed specimens this structural transition is more frequently observed. The phase transition orthoclase – "tweed" orthoclase may be related to the cooling history of granitoid body immediately after their intrusion. Regardless of the relatively high-temperature intense syn-metamorphic deformation under low-temperature amphibolite facies conditions (T=500-550 oC), the "tweed" domain microtexture of orthoclase may serve as a barrier for their further ordering, independently of the intense Al, Si diffusion. The limited topotaxial growth of microcline onto orthoclase in some crystallographic directions becomes possible just upon the conditions of brittle deformations in the low temperature greenshist facies. This process is realized during the final exhumation stage of the rocks in the presence of active fluid phase circulation and increase in the defectiveness of the potassium feldspar structure.

25. Structure and valent states of Fe in nanometer sized iron oxides (V. Ganev, M. Tarassov, L. Konstantinov, O. Petrov)

Iron oxides and oxyhydroxides formed under exogenous conditions and in laboratory synthesis experiments occur usually as nanometer-sized materials, containing the two principle valence states of iron, Fe2+ and Fe3+. The free Fe3+ ion is with five-fold energy degenerate 3d atom valence orbitals. Under the ligand field effect the 3d-orbital degeneracy is partially removed and the orbitals split into three equivalent t2g and two e2g orbitals. Resulting from the electron transitions between these orbitals, specific peaks appear in the optical absorption spectrum of the ligand complex. According to Jahn –Teller's theory, the non-linear molecules with degenerate valence orbitals are energy unstable and, as a result, their symmetry should spontaneously be violated so that a secondary removal of the degeneracy arises.

This study aims at investigation of the effect of size and morphology in some nano-sized iron oxides and oxihydroxides on their 3d-valence orbital energies on the basis of powder XRD patterns and optical absorption spectra in the UV-VIS-NIR region [55, 79]. For this purpose we investigated Fe3+ complex ions with 3d5 electron configuration in Fe2O3 (hematite) and FeOOH (goethite) in octahedral oxygen ligand field.

Natural and sol-gel synthesized a-Fe2O3 (hematite) and two types of a-FeOOH (ochre and glassy goethite) are investigated. Size and morphology effects on the optical absorption spectra are studied. It is shown that these effects lead to the appearance of less resolved and shaped spectra when the particle size decreases, which is related to an increase in the dispersion of the FeO6 octahedra distortion. The DFT calculations show that the absorption peak at 1.38 eV, typical for goethite in the NIR region, can be attributed to the d-d type electron transition between t1u and t2g beta orbitals. The latter result is well confirmed by the theoretical value of the transition energy equal to 1.4 eV.


26. Crystal structure of 2-guanidinium-1-aminocarboxylate monohydrate (Tz. Kolev, R. Petrova)

In synthesizing some new phases of guanidinum, we used as reagents the commercial product aminoguanidinium hydrogen carbonate (AGHC) of Fluka, EGA Chemie, Aldrich, and squaric acid (Huels-Marl, Germany). The vibrational spectrum of AGHC differs substantially from the expected one, although this compound contains the aminoguanidinium ion, as confirmed unambiguously from the synthesized product, aminoguanidinium squarate. In the infrared (IR) spectrum of AGHC the characteristic bands of hydrogen carbonate are missed, while there are two very strong bands at 1688 and 1634 cm–1. Comparing this spectrum with that of aminoguanidinium chloride we found out that in its IR spectrum there are seven n(N-H) bands instead of five in that of AGHC. This difference motivated us to calculate theoretically the spectrum of aminoguanidinium cation and comparing it with the experimentally measured one. We concluded that the commercial product AGHC is not in fact aminoguanidinium hydrogen carbonate. Later, after several recrystallization stages we were able to obtain transparent crystals suitable for single crystal X-ray diffraction analysis and to solve the crystal structure of this commercial compound. After each recrystallization we compared the IR-spectra of the starting and newly synthesized material, thus assuring that there is no any change in the molecular and crystalline structures. After solving the crystal structure it was found that the product sold as AGHC is in fact zwitterionic 2-guanidinium-1-aminocarboxylate monohydrate [16].

This compound can be considered as a derivative of aminoguanidinium, in which the positive charge is delocalized around the guanidinium residue, where as the negative one around the NHCO2 group (Fig. 1). This fact is also confirmed by the IR spectrum. Both guanidinium and NHCO2 groups are planar and nearly perpendicular to each other, with a dihedral angle of 83.26(5)o. The molecules are bonded through hydrogen bonds and form layers parallel to the crystallographic plane bc. These layers alternate along a-direction with layers formed by water molecules and bonded again by hydrogen bonds.

Fig.1. Chemical scheme of the molecule


27. Thermo-tribochemistry of (NH4)2SO4 (V. Petkova, K Tonsuadu, I. Dombalov, Y. Pelovski, L. Petrov)

Experimental results are presented on the thermal and thermal-tribochemical behavior of ammonium sulphate specimens of various origins obtained through purification of contaminated technological gases or in the process of caprolactam, methylmethacrylate or coke production. TG-DTA and X-ray analysis are used for studying the solid phase products as well as the mechanochemical activation of decomposition. Based on the obtained results a fundamental pattern of ammonium sulphate decomposition process is proposed, the intermediate products and stages of the process are proved, and a comparative analysis of the thermal behaviour of both activated and non-activated specimens is performed. The influence of the specimen preliminary treatment and the possibility for a partial decomposition of ammonium sulphate structure and for influencing on its thermal decomposition are proved [32].


28. DTA and XRD studies of non-conventionally synthesized Zn2SnO4 (I. Stambolova, A. Toneva, V. Blaskov, D. Radev, Y. Tzvetanova, P. Peshev)

Zinc stanate (Zn2SnO4) is prepared by non-conventional (low-temperature) synthesis using co-precipitation and additional mechanochemical or hydrothermal treatment of the sediment. The resulting product is studied by DTA and XRD. It is found that the three methods allow synthesis of Zn2SnO4 at relatively low temperatures. The method of preparation affects the structure of the intermediate compounds. The co-precipitation leads to the formation of an amorphous phase that transforms into ZnO and SnO2. A further rise in the temperature leads to the formation of Zn2SnO4 at 700 oC. By mechanochemical modification one can form ZnSn(OH)6, which at 650 oC transforms into zinc stanate. The hydrothermal modification results in synthesis of Zn2SnO3 while 650 oC is the temperature for preparing Zn2SnO4. The obtained zinc stanate crystallites are sized about 20 nm. The smallest in size crystallites are in the sample prepared by the mechanochemical co-precipitation method [71].

It is shown that, as compared to the conventional methods for preparing Zn2SnO4, in our synthesis the temperature is reduced by about 600 oC. The final product of this synthesis is important for environmental preservation for usage as a sensor for NO.


29. Growing mixed fluoride crystals CaxMe1-xF2 (Me=Ba, Sr) of optical grade: the role of atmosphere in the reactor (J. Mouchovski)

The Bridgman-Stockbarger method is appropriated for growing crystals of ternary compounds of the type CaxMe1-xF2 (Me = Ba, Sr; 0<x<1), which are prospective for the 193 and 157 nm semiconductor chips technology. One of the main factors in growing crystals of appropriate optical properties (birefringence below 1 nm/cm, high transmittance, index homogeneity, radiation hardness, minimal fluorescence) is the atmosphere in the reactor of growth. It has to satisfy two major requirements: a) to be of a sufficiently high pressure in order to prevent any undersirable evaporation and decomposition of the molten starting reagents and b) the contents of water vapors and oxygen to be extremely low so to avoid the melt contamination throughout its surface. Another source of contamination are the starting reagents since they consist, of particles containing absorbed molecules of water vapors and oxygen. To compensate their ineffective desorption, a metal scavenger (most often PbF2) has usually been added to the starting materials aiming at involvement of the gaseous contaminants in chemical reactions leading to an easy removal of volatile metal oxides and gasses such as HF and CO2. Due to its significantly lower volatility and higher capacity ZnF2 is expected to be more effective scavenger.

The aim of this work is: a) to study the effectiveness of PbF2 and ZnF2 as scavengers, either alone or in combination and to find the optimum contents for growing mixed fluoride crystals with optical grade; b) to analyze the crystal-chemical reactions involving oxygen-containing impurities when growing single CaF2 crystals; c) to determine a suitable range of pressures on the outlet of the growing chamber and to ensure such a constant flow of argon through it so that to suppress any decomposition and segregation effects and to minimize the contamination through the melt surface; and d) to assess the effectiveness of the preliminary high-temperature purification applied to all starting reagents for removal of the majority of oxygen-containing impurities.

Fig. 1. Changes in the extinction coefficient averaged
for different wavelengths from the transmittance curves of CaF2
optical windows, prepared from crystal ingots grown by adding
different amount of PbF2 as scavenger.

The analysis of experimental results shows that:

The Bridgman-Stockbarger method can be used for in-group-growth of ternary crystal compounds of the type CaxBa1-xF2 and CaxSr1-xF2 (0<x<1) in flowing argon, purified to below 1 ppm level of contaminant and under a constant pressure of about 1 Pa on the outlet in the case of a crucible loaded with deeply purified precursors prepared using the starting reagents via technological scheme effective for removing oxygen containing contaminants, the main of which are water vapors. Our preliminary data indicates that the optimal concentration of PbF2 to prepare such precursors should be between 1.5 and 2 wt.%.

30. Polyetheresters obtained from poly(H-phosphonate)s (K. Kossev, N. Koseva, K. Troev)

The biological importance and the practical significance of phosphate esters, containing P-H bonds (a feature emphasized in their names), have been a subject of numerous investigations due to their unique nature.

Here we report another aspect of the application of H-phosphonate chemistry combined with polymer chemistry, namely the preparation of biologically tolerant polyetherphosphoesters. The aim was tosynthese biocompatible and degradable polymers applicable as drug carriers, excipients, or components in implantable compositions. To design and synthesise diverse structures for degradable polyethers by incorporating phosphonate ester group and modify the P-center occupancy was our goal as well as to report new results. In the framework of this study and exploring the reactivity of the P-H bonds in poly(oxyalkylene)s with phosphonate or phosphate ester moieties in the structure and different side-chains bearing reactive groups (chloromethyl, oxiranyl), hydrophylic (PEG-residues), hydrophobic (PPG, phenylethyl residues), iongenic (tertiary amines). An application of polyoxyethylene phosphate to immobilize a chemical radio- protector is also presented. The reported results demonstrate the feasibility of the approach in terms of efficiency, mildness, and versatility of the synthetic procedures used [17].


31. Molecular dynamics of v–B2O3 (E. Kashchieva, B. Shivachev, Y. Dimitriev)

In this work the differences in the model density characteristics of v-B2O3 obtained by Molecular Dynamics (MD) are studied as functions of the cooling rates used to generate glass structures. The initial volume of the model cell and the number of atoms utilized for the dynamics correspond to the experimental density of B2O3 (1.84 g/cm3). We have employed a modified four-body potential, similar to that proposed by Cormack. For the parameterization of the employed potentials, Density Functional Theory (DFT) calculations were carried out for BO3, B2O5, BO3H3, B3O6, B3O6H3, B4O8 and B4O8H4 aggregates in order to reproduce the structure factors and the frequencies of localized vibrations making use of a large basis set 6-31G** and including polarization effects and the B3-LYP exchange-correlation functional. We have set two different cooling cycles. Cycle I corresponds to the high temperature structure of vitreous B2O3, while cycle II give us a relatively slower cooled structure (Table 1) [58, 97].

Results fof this MD simulation do not reproduce exactly the experimentally observed density of v-B2O3. The density for the cycle I structural models is far from the experiment. The computed density for MD models, containing less than 400 atoms obtained in cooling cycle II, is very close to the experimental density (Fig. 1). The fraction of boroxol rings as a function of the number of atoms for both cycles is presented in Fig. 2. These results present the influence of the cooling cycle on the final structure, namely, there are more boroxol rings in the slow-cooled structure. However, the fraction of B atoms in boroxol rings is lower than that reported by others. In fact, there are no variations in the fraction of B3O6 rings as a function of the number of atoms in cycle I. In cycle II the fraction of B3O6 progressively decreases. As the trends in Figures 1 and 2 are similar one can associate the variations in the density with such in the fraction of boroxol rings in the structure.

Table 1. Scheme for the cooling MD algorithms.

CYCLE I
(fast cooling)

CYCLE II
(slow cooling)

20 ps NVT 6000 K

20 ps NVT 4000 K

20 ps NVT 2000 K

800 ps NVT 1300K

30 ps NVT per 100 degree from 1300 up to 300 K (a total time of 300 ps)

30 ps NVT per degree from 1300 up to 300 K (a total time of 30000 ps)

30 ps NPT 300K


 

Fig. 1. Model density [g/cm3] for MD generated structures of B3O6 (according to Table 1)   Fig. 2. Fraction of boron atoms in boroxol rings for MD generated structures of B3O6 vs. the number of atoms in the unit cell (according to Table 1 ).

The obtained results show that there exist density variations associated with the difference in applied cooling algorithms. The results indicate that there exists density variations associated with the difference in the applied cooling algorithms. The model density decreases with increasing the number of atoms in the unit cell, especially in cycle II. The calculated densities are influenced by the change in the ratio of the structural units, BO3 and B3O6, in the models. According to these results the cooling scheme used to simulate the structure of v-B3O3 should be taken into account.

32. A method for determining structural parameters by TEM (V. Dimov, N. Khaltakova)

Micrometer-sized individual representatives of minimal concentration are met in polymineral samples or in the case of crystallization of new products. In many cases the study of their crystal structure can be performed only using transmission electron microscopy (TEM). There are methodological limitations in determining the structural parameters on the basis of single crystal electron diffraction patterns. There are symmetry constrains for reflexes of the type (hkl) for body- or face- centered unit cells. This fact determines the presence in electron diffraction patterns of forbidden reflexes of zero intensity and does allow the determination of the primitive unit cell. The strong (dynamical) interaction of electrons with matter modulates the intensity of diffracted rays selectively. The determination of these part of intensity, which depends on the structure factor is obscured and, in many cases, impossible. Under specific conditions, periodic changes in the single crystal electron diffraction patterns of the intensity of the diffraction spots, which are symmetric with respect to the central spot, can be attributed to the structural factor and to be used for solving structures.

An original method is presented for determining of the unit cell parameters and of possible group of symmetry of non-centrosymmetric structures by use of indexing a series of electron diffraction pattern obtained in rotating single crystals around a crystallographic axis. We studied an unknown synthetic phase of potassium-titanium zeolite-like silicate and an orthorhombic unit cell with parameters a = 1.31(54) nm, b = 1.02(02) nm, c = 0.73(40) nm, a = 90o, b = 90o, g = 90o is determined as well as the following possible space groups P222, Pmm2, Pmmm and P2121 21 are specified.

INTERINSTITUTE PROGRAMS:


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PUBLICATIONS AND REPORTS AT CONFERENCES AND LOCAL MEETINGS


PUBLISHED ARTICLES AND REPORTS:

1. Atanassova-Vladimirova, S., B. Mavrudchiev, A. von Quadt, I. Peytcheva, K. Kouzmanov. 2003. New data of the petrology and geochemistry of Vitosha pluton. - Proc. of annual sci. conf. of BGD "Geology 2003", Sofia, December 11-12, 7-9.

2. Baicheva, O., D. Salkova, A. Damianova, I. Sivriev, N. Lihareva. 2003. Mineral composition of tomato plants invaded by nemathodes Meloidogyne arenaria and treated with NH4VO3. - Journal of Balkan Ecology, 6, 2, 157 - 160.

3. Chakalov, K., T. Popova, K. Mitov, E. Filcheva, O. Petrov. 2003. Influence of natural and modified zeolites on the mobility of some heavy metals in soils and model experiments. - Proc. of X Balkan congress "Mineral Processing in the 21th century", Varna, Bulgaria, June 15-20, 780-786.

4. Damianova, A., O. Baicheva, D. Salkova, I. Sivriev, N. Lihareva. 2003. Evaluation of changes in the element content and biomass of invaded with Meloidogyne arenaria tiny tim tomato plants under NH4VO3 treatment. - Acta Biolagica Hungarica, 54, 3-4, 373-384.

5. Damianova, A., O. Baicheva, D. Salkova, N. Lihareva. 2003. Influence of NH4VO3 on the chemical composition of tiny tim tomato plants invaded with Meloidogyne arenaria. -In: Proceeding book of 40th International symposium on trace elements in human:New perspectives, Athene, Greece, 1072- 1078.

6. Filcheva, E., K. Chakalov, T. Popova, K. Mitov, O. Petrov. 2003. A new method for preparation of humic containing materials for their use in ecology. - Proc. of X Balkan congress "Mineral Proceessing in the 21th century", Varna, Bulgaria, June 15-20, 757-762.

7. Georgiev, V., O. Vitov. 2003. Heavy minerals concentrates features of Momchilgrad depression and its frame (East Rhodopes). – In: Proceeding of IV National symposium "Metallogeny of Bulgaria", May 7-9, Sofia, 73-77. (in Bulgarian)

8. Georgiev, V., O. Vitov. 2003. Heavy minerals concentrates – mineralogical zonation and prognosis in prospecting for mineral deposits in the Eastern Rhodopes. - Proc. of annual sci. conf. of BGD "Geology 2003", Sofia, December 11-12, 40-42.

9. Georgieva, B., I. Podolesheva, D. Nihtianova, I. Konstantinov. 2003. Nanosized tin-oxide layers – new method of preparation and humidity sensing properties. - Nanoscience&Nanotechnology, 3, Heron Press, Sofia, 133-135.

10. Güttler, B., B. Mihailova, R. Stosch, U. Bismayer, M. Gospodinov. 2003. Local phenomena in relaxor-ferroelectric PbSc0.5B"0.5 O3 (B"= Nb, Ta) studied by Raman spectroscopy. - Journal of Molecular Structure, 661-662 C, 469-479.

11. Hristov, V., I. Kairakov, I. Donchev, Z. Damyanov. 2003. Innovation of the technology and scheme of benefication of Kremikovtsi ore for improving the production of barite and iron concentrates. – Proc. of X Balkan congress "Mineral Processing in the 21th century", Varna, Bulgaria, June 15-20, 646-651.

12. Ivanova, V., V. Petkova, Y. Pelovski. 2003. Thermal analysis and solid electrolyte system study of FeSO4.H2O – BaO2 mixtures. - Journal of Thermal analysis and Calorimetry, 74, 387-394.

13. Kalvachev, Yu. 2003. Oxydation of hydrocarbons over nanosized gold catalysts. - Nanoscience&Nanotechnology, 3, Heron Press, Sofia, 45-47.

14. Kamenov, B., A. von Quadt, I. Peytcheva. 2003. New insight into petrology, geochemistry and dating of the Vejen pluton, Bulgaria. – Geochem., miner. and petrol., 39, 3-25.

15. Kamenov, B., A. von Quadt, I. Peytcheva. 2003. Petrological, geochemical and isotopic constraints for magma origin and evolution of the Capitan-Dimitrievo pluton, Central Srednogorie, Bulgaria. - Geochem. Miner. Petrol. 40,

16. Kolev, T., R. Petrova. 2003. Zwitterionic 2-guanidinium-1-aminocarboxilate monohydrate. - Acta crystallographica E 5, 447-449.

17. Kossev, K., A. Vassilev, Y. Popova, I. Ivanov, K. Troev. 2003. Funktionalization of poly(oxyethylene phosphonate) under phase-transfer catalyst conditions. - Polymer, 44, 1987-1993.

18. Kossev, K., N. Koseva, K. Troev. 2003. Calcium chloride as co-catalyst of onium halides in the cycloaddition of carbon dioxide to oxiranes, - Journal of Molecular Catalysis A: Chemical 194, 29-37.

19. Kostov, V., V. Gergelchev. 2003. Mineralogical and metallogenic characterization of the Spahievo ore-magmatic claster in the East Rhodopes. - In: Proceeding of IV National symposium "Metallogeny of Bulgaria", May 7-9, Sofia, 111-115. (in Bulgarian)

20. Kunev, B., D. Paneva, V. Petkova, I. Mitov, I. Dombalov. 2003. Mechanochemical treatment of ðyrite concentrate. – In: CONTACT 2003, 43-48.

21. Lazaro, M. J., I. Suelves, R. Moliner, S. Vassilev, C. Braekman-Danheux. 2003. Low cost catalytic sorbents for NOx reduction. 2. Tests with no reduction reactives. – Fuel, 82, 7, 771-782.

22. Lihareva, N. 2003.Comparison between fractionation of ash metals using a sequential extraction procedure and single extraction. – Bulg. Chem. Comm., 35, 1, 59-64.

23. Marinova, I. 2003. Notes on the data reliability in sampling and assay for gold in the prospecting. – In: Proceeding of IV National symposium "Metallogeny of Bulgaria", May 7-9, Sofia, 116-121. (in Bulgarian)

24. Marinova, I., A. Tzvetkov, O. Malinov, I. Kalinova. 2003. Geology and gold mineralizations of Lensko and Bely dol occurrences, Eastern Rhodopes, SE Bulgaria. – Proc. book "UNIVERSITARIA ROPET 2003", October 16-18, Petrosani, Romania, 33-38.

25. Mihailova, B., U. Bismayer, B. Güttler, L. Tosheva, J. Sterte. 2003. Raman scattering in locally inhomogeneous crystals.- Phase transitions, 76, 17-32.

26. Mincov, I., V. Ganev, T. Troev, B. Shivachev. 2003. Temperature dependence study of crystallization in Fe78Si9B13 and Co75Si15B10 amorphous alloys using positron lifetime spectroscopy and x-ray diffraction. – Meeting in Physics at University of Sofia, 4, ed. A. Proykova, Heron Press, Sofia, 133-138.

27. Neubauer, F., C. A. Heinrich and the GEODE ABCD Working group including I. Peytcheva et al. 2003. Late Cretaceous to Tertiary geodynamics and ore deposit evolution of the Alpine-Balkan-Carpathian-Dinaride orogen. – In: Eliopoulos et al (eds.), Mineral Exploration and sustainable Development. Millpress, Rotterdam, 1133-1136.

28. Nihtianova, D., V. Ganev, N. Khaltakova, M. Gospodinov. 2003. Crystal structure identification of Bi2(MoO4)3 single crystals. - Compt.rend.Acad.bulg.Sci., 56, 7, 53-58.

29. Ovtcharova, M., A. von Quadt, C. A. Heinrich, M. Frank, M. Kaiser-Rohrmeier, I. Peytcheva, Z. Cherneva. 2003. Triggering of hydrothermal ore mineralization in the Central Rhodopean Core Complex (Bulgaria) – Insight from isotope and geochronological studies of tertiary magmatism and mineralization. – In: Eliopoulos et al. (eds), Mineral exploration and sustainable development, Millpress, Rotterdam, 367-370.

30. Pelovski, Y., V. Petkova, I. Dombalov. 2003. Thermal analysis of mechanoactivated mixtures of Tunisia phosphorite and ammonium sulphate. – Journal of Thermal Analysis and Calorimetry, 72, 967-980.

31. Petkova, V., K. Tonsuadu, I. Dombalov, Y. Pelovski, L. Petrov. 2003. Tribochemistry of the ammonium sulphate. - In: Contact 2003, 117-122. (in Bulgarian)

32. Petkova, V., R. Kuusik, K. Tonsuadu, Y. Pelovski, I. Dombalov, L. Petrov. 2003. Investigation of thermal decomposition of mechano-activated mixstures of Estonian phosphorite and ammonium sulphate. – In: Contact 2003, 111-116. (in Bulgarian)

33. Petkova, V., Y. Pelovski. 2003. Thermal analysis and solid electrolyte system study of FeSO4.H2O – BaO2 mixtures. - Journal of Thermal Analysis and Calorimetry, 72, 981-989.

34. Petrova, N., T. Mizota, Ts. Stanimirova, G. Kirov. 2003. Sorption of water vapor on a low temperature hydrotalcite metaphase: calorimetric study. - Microporous and Mesoporous Materials, 63, 139-145.

35. Peytcheva, I., A. von Quadt and GEODE team. 2003. The power of radiogenic isotope methods in resolving geochronological and source problems at ore deposits: examples from Central Srednogorie, Bulgaria. - Proc. of annual scientific conf. of BGD "Geology 2003", December 11-12, Sofia, 61-64.

36. Peytcheva, I., A. von Quadt, K. Kouzmanov, K. Bogdanov. 2003. Elshitsa and Vlaykov Vruh epithermal and porphyry Cu-(Au) deposits of Central Srednogorie, Bulgaria: source and timing of magmatism and mineralisation. – In: Eliopoulos et al. (eds), Mineral Exploration and sustainable Development., Millpress, Rotterdam, 371-373.

37. Popova, T., O. Petrov, K. Chakalov, K. Mitov, E. Filcheva. 2003. Modified zeolites – properties and application in ecology. - Proc. of X Balkan congress "Mineral Processing in the 21th century", June 15-20, Varna, Bulgaria, 757-762.

38. Tarassov, M., B. Mihailova, E. Tarassova, L. Konstantinov. 2003. Fe2O3.nH2O-nanophases formed in tungsten-polyanion-assisted sol-gel process. – Nanoscience&Nanotechnology, 3, Heron Press, Sofia, 64-66.

39. Tarassova, E., M. Tarassov. 2003. Occurrence, chemical composition and petrogenetic significance of allanite in granitoids from Belassitza mountain, Serbo-Macedonian Massif. - Proc. of annual scientific conf. of BGD "Geology 2003", December 11-12, Sofia, 71-73.

40. Tsintsov, Z., B. Banushev, M. Sivilov. 2003. Characterization of the sulfide mineralization in metamorphosed serpentinites near Zhivkovo village, Central Sredna Gora, Bulgaria. – Annual of the University of Mining and Geology "St. Iv. Rilski", 46, 1, 177-182.

41. Tzvetanova, Y. 2003. Lead phosphate minerals from Brussevtzi deposit (Eastern Rhodopes, Bulgaria) – SEM, IR and DTA study. - Compt.rend.Acad.bulg.Sci., 56, 5, 55-58.

42. Vassilev, S., R. Menendez, D. Alvarez, M. Diaz-Somoano, M. R. Martinez-Tarazona. 2003. Phase-mineral and chemical composition of coal fly ashes as a basis for their multicomponent utilization. 1. Characterization of feed coals and fly ashes. - Fuel, 82, 14, 1793-1811.

43. Vassilev, S., J. Tascon. 2003. Methods for characterization of inorganic and mineral matter in coal: a critical overview. - Energy and Fuels, 17, 2, 271-281.

44. Vassileva, C. 2003. Phase-mineral transformations in inorganic matter of Bulgarian lignites during heating. – Compt.rend.Acad.bulg.Sci., 56, 6, 41-48.

45. Vassileva, C. 2003. Phase-mineral transformations in inorganic matter of Bulgarian subbituminous and bituminous coals during heating. – Comp.rend. Acad.bulg.Sci., 56, 9, 19-26.

46. Vassileva, M., S. Dobrev, Z. Damyanov. 2003. Comparative characteristics of endogenic kutnahorite from Ribnitsa deposit and exogenic kutnahorite from Kremikovtsi deposit. – Annual of the University of Mining and Geology "St. Iv. Rilski", 46, part I - geology and geophysics, 195-200.

47. Vitov, O. 2003. Summary of the results of heavy mineral samples and investigations in Bulgaria. – In: Proceeding of IV National symposium "Metallogeny of Bulgaria", May 7-9, Sofia, 38-42. (in Bulgarian)

48. Vitov, O., I. Marinova. 2003. Choice of grid-based sampling framework for prospecting of small gold deposits in the West Balkan. – Mining and geology, 10, 35-40. (in Bulgarian with English abstract)

49. Vitov, O., I. Marinova. 2003. On the characteristics of grid-based sampling frameworks for soil geochemical surveys. - Proc. of annual scientific conf. of BGD "Geology 2003", December 11-12, Sofia, 83-86.

50. Zidarov, N., I. Peytcheva, A. von Quadt, V. Andreichev, L. Macheva, R. Titorenkova. 2003.Timing and magma sources of metagranites from the Serbo-Macedonian Massif (Ograzhden and Maleshevska mountains, SW Bulgaria): constraints from U-Pb and Hf-zircon and Sr whole rock isotope studies. – Proc. of annual scientific conf. of BGD "Geology 2003", December 11-12, Sofia, 89-91.

51. Zidarova, B. 2003. Rare earth elements in natural fluorite as indicators of the mineral-forming environment. – Compt.rend.Acad.bulg.Sci., 56, 11, 19-26.

52. Zimmerman, A., H. Stein, R. Markey, L. Fanger, C. Heinrich, A. von Quadt, I. Peytcheva. 2003. Re-Os ages for the Elatsite Cu-Au deposit, Srednogorie zone, Bulgaria. – In: Eliopoulos et al (eds.), Mineral Exploration and sustainable Development, Millpress, Rotterdam, 1253-1256.

PUBLICATIONS IN PRESS:

53. Bachmann, H-G, Z. Tsintsov. Placer gold in SW-Bulgaria: past and present. – Gold Bulletin,

54. Ferdov, S., C. Lengauer, O. Petrov, V. Kostov-Kytin. A rapid method for low-temperature synthesis of the Na-analogue of the microporous titanosilicate GTS-1. - Journal of Materials Science Letters,

55. Ganev, V., M. Tarassov, L. Konstantinov, O. Petrov. Structure and valent states of iron in some crystalline and amorphous iron oxides:UV-VIS spectroscopy and DFT calculations data. - Nanoscience &Nanotechnology, 4, Heron Press, Sofia,

56. Kalvachev, Yu., V. Kostov-Kytin, H. Papp. IR investigation of NO adsorption over nanosized gold deposited on titanosilicates ETS-4 and ETS-10. - Nanoscience &Nanotechnology, 4, Heron Press, Sofia,

57. Kashchieva, E., B. Shivatchev. Tem study of nanoclusters in oxide glasses. - Nanoscience &Nanotechnology, 4, Heron Press, Sofia,

58. Kashchieva, E., B. Shivatchev, Y. Dimitriev. 2003. Molecular dynamics studies of vitreous boron oxide. – Journal of Non-crystalline Solids,

59. Lazaro, M. J., M. Galvez, I. Suelves, R. Moliner, S. Vassilev, C. Braekman-Danheux. Low cost catalytic sorbents for NOx reduction. 3. NO reduction tests using NH3 as reducing agent. - Fuel, 83,

60. Lihareva, N. Study of metals fractionation in ash samples using a sequential extraction procedure. - Bulg.Chem. Comm., 35,

61. Mihailova, B., M. Wagner, S. Mintova, T. Bein. Colloidal molecular sieves: model system for kinetic study of crystal grouth process. - Studies in Surface Science and Catalysis,

62. Mincov, I., B. Shivachev, T. Troev, V. Ganev, A. Liolios, Sp. Dedousis, M Chardalas. Temperature dependence study of crystallization of Fe78Si9B13 amorphous alloy by positron lifetime method and DTA. - Second Balkan Conf. on Glass Science and Technology, Varna, Bulgaria,

63. Penev, V., L. Konstantinov. Geometrization of the language of chemistry: Mathematical representation of the complex chemical objects – Academic Open Internet Journal,

64. Penev, V., L. Konstantinov. Mathematical representations of chemical processes: Part I. Conceptual schemes for representing changes; space and coordinate system; method – Academic Open Internet Journal,

65. Penev, V., L. Konstantinov. Mathematical representation of chemical processes: Part II. Representation of the free physical particles and of the laws for preservation of electric charge and preservation of mass in chemical reactions – Academic Open Internet Journal,

66. Penev, V., L. Konstantinov. Geometric images of simple and complex chemical objects in the space of chemical structures VM(3). Studying the relationship between the languages of chemistry and geometry. - Academic Open Internet Journal,

67. Peytcheva, I., A. v. Quadt, M. Ovtcharova, R. Handler, F. Heubauer, E. Salnikova, Yu. Kostitsyn, S. Sarov, K. Kolcheva. Metgranitoids from the eastern parts of the Central Rhodopean Dome (Bulgaria): U-Pb, Rb-Sr and 40Ar/39Ar timing of emplacement and exhumation and isotope-geochemical features. – Mineralogy and Petrology,

68. Shivatchev, B., I. P. Mincov, E. P. Kashchieva, Y. B. Dimitriev, R. Smith, T. Troev. Position lifetime spectroscopy of vitreous B2O3. – Journal of Non-crystalline Solids,

69. Stanimirova, Ts., N. Piperov, N. Petrova, G. Kirov. Thermal evolution of Mg-Al-CO3 hydrotalcites. - Clay Minerals,

70. Tarassov, M., E. Tarassova, L. Konstantinov. Sol-gel preparation and characterization of amorphous and crystalline WO3.xFe2O3.nH2O phases. - Nanoscience &Nanotechnology, 4. Heron Press, Sofia,

71. Toneva, A. Application of DTA and X-ray diffraction for investigation of nonconventional synthesis of Zn2SnO4. – Journal of Thermal Analysis and Calorimetry,

72. Troev, T., B. Shivachev, T. Yoshiie. Positron lifetime calculations of defects in nickel containing hydrogen at various temperatures. – Materials Science Forum,

73. Vassilev, S., R. Menendez, M. Diaz-Somoano, M. R. Martinez-Tarazona. Phase-mineral and chemical composition of coal fly ashes as a basis for their multicomponent utilization. 2. Characterization of ceramic cenosphere and water-soluble salt concentrates. - Fuel, 83,

74. Vassilev, S., R. Menendez, A. Borrego M. Diaz-Somoano, M. R. Martinez-Tarazona. Phase-mineral and chemical composition of coal fly ashes as a basis for their multicomponent fly ash utilization. 3. Characterization of magnetic and char concentrates. - Fuel,

75. Zidarova, B., N. Zidarov. Main elements of the common geogenetic model for deposits of the Fluorite Ore Formation in Bulgaria. – Rev. Bulg. Geol. Soc., (in Bulgarian with English abstract)

ABSTRACTS AND POSTERS AT SCIENTIFIC EVENTS:

76. Atanassova-Vladimirova, S., A. von Quadt, I. Peytcheva, B. Mavrudchiev. 2003. The Vitosha pluton as part of the Apuseni-Banta-Timok-Srednogorie zone: new insight from petrology and isotope geochronology. – Final GEODE-ABCD workshop, March 22-24, Seggauberg, Austria, Abstract volume, 16-17.

77. Cherneva, Z., M. Ovtcharova, S. Arkadaksky, A. von Quadt, I.Peytcheva.2003. Accessory minerals behavior during Eocene melting of Hercynian granitoids in the Central Rhodopian Dome, Bulgaria. - Final GEODE-ABCD workshop, March 22-24, Seggauberg, Austria, Abstract volume, 25-26.

78. Ferdov, S., U. Kolitsch, O. Petrov, V. Kostov-Kytin, C. Lengauer, E. Tillmanns. 2003. Synthesis and crystal structures of two new, microporous materials, MCV-1 and MCV-2. - "Rohstoffe im Dienste der Gesellschaft", International symposium of the Austrian Academy of Sciences (Kommission fur Grundlagen der Mineralrohstoffforschung), November 7, Vienna, Austria.

79. Ganev, V., M. Tarassov, L. Konstantinov, O. Petrov. 2003. Structure and valent states of iron in some crystalline and amorphous iron oxides:UV-VIS spectroscopy and DFT calculations data. . – 5th Annual national workshop, NANO'2003, November 17-18, Sofia, Bulgaria.

80. Ilieva, A., B. Mihailova, O. Petrov, 2003. Structural state of opals from East Rhodopes, Bulgaria. - 10th Conference of the European Clay Groups Association, Euroclay 2003, June 22-26, Modena, Italy.

81. Kalvachev, Yu., V. Kostov-Kytin, H. Papp. 2003. IR investigation of NO adsorption over nanosized gold deposited on titanosilicates ETS-4 and ETS-10. – 5th Annual national workshop, NANO'2003, November 17-18, Sofia, Bulgaria.

82. Kamenov, B., A. von Quadt, I. Peytcheva. 2003. New petrological, geochemical and isotopic data on the genesis of Capitan-Dimitrievo pluton, Central Srednogorie, Bulgaria. - Final GEODE-ABCD workshop, March 22-24, Seggauberg, Austria, Abstract volume, p. 31.

83. Kamenov, B., R. Moritz, R. Nedialkov, I. Peytcheva, S. Stoykov, Y. Yanev, A. von Quadt. 2003. Petrology of the Late Cretaceous ore-magmatic centers from the Central Srednogorie, Bulgaria: Magma evolution and sources. - Final GEODE-ABCD workshop, March 22-24, Seggauberg, Austria, Abstract volume, p. 30.

84. Kolb, U., D. Nihtianova, I. Nikolov, V. Nikolov, D. Kovacheva. 2003. Crystal structure analysis of NaAl(WO4)2 single crystals. – 21st European Crystallographic Meeting, August 24-29, Durban, South Africa, f2.m2.p2.

85. Koseva, N., K. Kossev, K. Troev. 2003. Polyetheresters via Exploring Phosphorus Chemistry. - Learning from nature how to design new implantable biomaterials, Avor, October 13-24, Algavre, Portugal, p. 62.

86. Koseva, N., K. Kossev, R. T. Georgieva, R. P. Kusheva, P. S. Denkova, K. D. Troev. 2003. Poly(Alkylene Hydrogen Phosphonates) – Feasible Precursor Polymers for Conjugation of Bioactve Molecules. - Macromolecular approaches to advanced biomaterials engineering systems, November 8-11, Sofia, Bulgaria.

87. Kossev, K. N. Koseva, K. Troev. 2003. Cyclic Carbonate Functionalizad Polymers for Immobilization of Enzymes and Cells. - Learning from nature how to design new implantable biomaterials, Avor, October 13-24, Algavre, Portugal, p.72

88. Kashchieva, E., B. Shivatchev. 2003. Tem study of nanoclusters in oxide glasses. – 5th Annual national workshop, NANO'2003, November 17-18, Sofia, Bulgaria.

89. Mihailova, B., A. Boris, C. Bernhard, M. Gospodinov, U. Bismayer. 2003. Far infrared ellipsometry of Pb-based relaxor ferroelectric single crystals. - ANKA Annual Report ISS Institute for synchrotron radiation, Forschungzentrum Karlsruhe GmbH., 133-134.

90. Ovtcharova, M., A. von Quadt, I. Peytcheva, F. Neubauer, C. A.Heinrich, M. Kaiser. 2003. Time and duration of metamorphism and exhumation of the Central Rhodopean Core Complex, Bulgaria. - EGS-AGU-EUG Joint Assembly, Nice, Geophysical Research Abstracts, Vol. 5, 10121.

91. Ovtcharova, M., A. von Quadt, Z. Cherneva, I. Peytcheva, C. A. Heinrich, M. Kaiser-Rohrmeier, F. Neubauer, M. Frank. 2003. Isotope and geochronologycal study on magmatism and migmatisation in the Central Rhodopean Core Complex, Bulgaria. - Final GEODE-ABCD workshop, March 22-24, Seggauberg, Austria, Abstract volume, p. 42.

92. Petkova, V., K. Tonsuadu, I. Dombalov, Y. Pelovski, L. Petrov. 003. Tribochemistry of the ammonium sulphate. – XII Jubilee science-technical session CONTACT 2003, October 30-31, Sofia, Bulgaria. (in Bulgarian)

93. Petkova, V., R. Kuusik, K. Tonsuadu, Y. Pelovski, I. Dombalov, L. Petrov. 2003. Investigation of thermal decomposition of mechano-activated mixstures of Estonian phosphorite and ammonium sulphate. - XII Jubilee science-technical session CONTACT 2003, October 30-31, Sofia, Bulgaria. (in Bulgarian)

94. Petrova, N., T. Mizota, Ts. Stanimirova, G. Kirov. 2003. Sorption of water vapor on low temperature hydrotalcite metaphases. - 10th Conference of the European Clay Groups Association, Euroclay 2003, Modena, Italy, June 22-26, 223-224.

95. Peytcheva, I., A. von Quadt. 2003. U-Pb zircon isotope system in mingled and mixed magmas: an example from Central Srednogorie, Bulgaria. – EGS-AGU-EUG Joint Assembly, Nice, Geophysical Research Abstracts, v. 5, 09177.

96. Peytcheva, I., A. von Quadt, K. Kouzmanov, K. Bogdanov. 2003. Timing of magmatism and mineralization in Elshitsa and Vlaykov Vruh Cu-(Au) deposits of Central Srednogorie, Bulgaria: constraints from U-Pb zircon and rutile geochronology and Hf-zircon and Sr-whole-rock tracing. - Final GEODE-ABCD workshop, Seggauberg, Austria, March 22-24, Abstract volume, p. 46.

97. Shivachev, B., E. Kashchieva, Y. Dimitriev. 2003. Computer simulation of the structure of vitreous boron oxide. – IInd Balkan conference on glass and ceramics, September 24-28, Varna, Bulgaria.

98. Stanimirova, Ts., N. Piperov, N. Petrova, G. Kirov. 2003. Thermal evolution of Mg-Al-CO3 hydrotalcites. – 10th Conference of the European Clay Groups Association, Euroclay 2003, Modena, Italy, June 22-26, 262-263.

99. Tarassov, M., E. Tarassova, L. Konstantinov. 2003. Sol-gel preparation and characterization of amorphous and crystalline WO3.xFe2O3.nH 2O phases. – 5th Annual national workshop, NANO'2003, November 17-18, Sofia, Bulgaria.

100. Titorenkova, R. 2003. Heterogeneity of zircon from high-grade metamorphic rocks, Ograzhden Mountain, Serbo-Macedonian Massif. - Proc. ann. sci. conf. BGD "Geology 2003", Sofia, December 11-12, p. 74.

101. Titorenkova, R., L. Macheva, N. Zidarov, A. von Quadt, I. Petcheva. 2003. Metagranites from SW Bulgaria as a part of the Neoproterozoic to Early Paleozoic system in Europe: new insight from zircon typology, U-Pb isotope data and Hf-tracing. – EGS-AGU-EUG Joint Assembly, Nice, Geophysical Research Abstracts, vol. 5, 08963.

102. Tsintsov, Z., B. Banushev, M. Sivilov. 2003. Characterization of the sulfide mineralization in metamorphosed serpentinites near Zhivkovo village, Central Sredna Gora, Bulgaria. – International scientific conference "50 year University of Mining and Geology" " St.. Iv. Rilski", May 14-16, Sofia

103. Von Quadt, A., I. Peytcheva. 2003. Dating of ore forming processes in copper-porphyry deposits: Is U-Pb zircon the only suitable method. – Suppl. Geochemica and Cosmochemica Acta, Abstracts 13th Ann. Goldschmidt Conference, Kurashiki, Japan, A515.

104. Von Quadt, A., I. Peytcheva, C. A. Heinrich, M. Frank, V. Cvetkovic, M. Banjesevic. 2003. Evolution of the Cretaceous magmatism in the Apuseni-Timok-Srednogorie metallogenic belt and implications for the geodynamic reconstructions: new insight from geochronology, geochemistry and isotope studies. - Final GEODE-ABCD workshop, March 22-24, Seggauberg, Austria, Abstract volume, p. 60.

105. Von Quadt, A., I. Peytcheva, V. Cvetkovic. 2003. Geohronology, geochemistry and isotope tracing of the Cretaceous magmatism of Eastern Serbia and Panagyurishte district (Bulgaria) as part of the Apuseni-Timok-Srednogorie metallogenic belt in Eastern Europe. – In: Eliopoulos et al. (eds.), Mineral Exploration and sustainable Development, Millpress, Rotterdam, 407-410.

106. Von Quadt, A., I. Peytcheva, V. Cvetkovic, M. Banjesevic, D. Kozelj. 2003. Geochronology, geochemistry and isotope tracing of the Cretaceous magmatism of Timok Magmatic Complex and Ridanj-Krepoljin Zone East Serbia. - Abstracts of the workshop on the Cretaceous and tertiary Geodinamics of the ABCD region, January 10-11, Strazburg, p. 19.

REPORTS AND POSTERS ON THE SESSION
"SCIENTIFIC AND APPLIED ACHIEVEMENT OF CLMC-BAS"
19-20 March 2003

107. Damyanov, Z. Genetic significance of the phillosilicate mineralization in SEDEX-type ore deposits (on the example of Kremikovtsi deposit).

108. Damyanov, Z. Genetic peculiarity of the barite mineralization in the Kremikovtsi deposit.

109. Dimov, V., P. Vitanov. Investigation of the structure of porous silicon obtained by electrochemical etching.

110. Donchev, I. Synthesis of artificial rocks (Synroc).

111. Donchev, I., A. Lenchev. Posibilities for utilization of fly-ashes from TEPS as an addition into clinker for the production of Portland cement.

112. Ganev, V. Positron spectroscopy and x-ray diffraction investigation on Fe78Si9B13 metal glasses.

113. Kalvachev, Yu. Gold based ca talysts for environmental important reactions.

114. Kalvachev, Yu. Oxidation of aliphatic hydrocarbons on gold nanosized catalysts.

115. Kossev, K. Synthesis of phytopharmaceutical preparations, carriers and polimer medicine forms.

116. Kostov-Kytin, V., S. Ferdov, O. Petrov. Synthesis and crystallochemical peculiarities of titanosilicate phases.

117. Lihareva, N. Application of sequential extraction procedure and ICP-AES method for studyng the metal partitioning in ashes.

118. Mihailova, B., L. Konstantinov. Local structure and dynamics in complex oxide materials.

119. Mihailova, B., L. Konstantinov. Local structure and dynamics in relaxor-ferroelectric PbSc0. 5B"0.5O"3 (B"=Nb, Ta) single crystals.

120. Nihtianova, D. Tilt series method in TEM for investigation of aerinite and double tungstates.

121. Penev, V., L. Konstantinov, M. Marinov. Main results on the project "Geometrization of the foundations of chemistry".

122. Petkova, V., A. Toneva. Thermal analysis of mechanically activated mixtures of Tunisian phosphorite and ammonium sulfate.

123. Petrov, O. Modeling and modification on mineral systems.

124. Petrova, R. Thiourea complexes of (CdNO3)2

125. Petrova N., Ts. Stanimirova, T. Mizota. Evaluation of low-temperature hydrotalcite metaphases as heat exchangers.

126. Tarassov, M., B. Mihailova, E. Tarassova, L. Konstantinov. Phase-formation in the system WO3-Fe2O3-H2 O of low-temperature conditions.

127. Tarassova, E. Accessory minerals – indicators for magmatic processes for example of Fe-Ti-Mn oxides and allanites.

128. Titorenkova, R. Inner structure and chemical composition of zircon inmetagranites from Serbo-Macedonian Massif (SW Bulgaria).

129. Toneva, A., V. Petkova. Thermal investigations of the solid state synthesis of the shpinel-like Zn2SnO4 and BaFe2O4.

130. Tsintsov, Z. Whitemetal mineralization in ultrabasites and listwenites from the Rhodopes.

131. Tzvetanova, Y. Crystal chemical peculiarities of minerals from metasomatic zones and oxidatio zone of Brussevtzi deposit.

132. Vassilev, S., C. Vassileva. Mineralogy and geochemistry of coals and coal products.

133. Vassileva, B., O. Petrov. Investigation and comparative characteristic of minerals as filter systems.

134. Vitov, O. Shlihovo-mineralogical map of Bulgaria.

135. Vitov, O. Termotransfusion of gold in the rocks.

136. Zidarov, N. Mineral systems– composition, conditions and processes of appear, transform and interaction.

137. Zidarov, N., L. Macheva, I. Peycheva, R. Titorenkova. Metagranitoids from the Serbo-Macedonian Massif (SW Bulgaria).

138. Zidarov, N., J. Muhovski, M. Tarassov. Electrochemically induced transport processes in basaltic melts.

139. Zidarov, N., V. Penev, B. Zidarova. Geometrization of the language of mineralogy.

140. Zidarova, B., N. Zidarov. Main elements of the common geogenetic model for deposits of the Fluorite Ore Formation.