BULGARIAN ACADEMY OF SCIENCES

 

CENTRAL LABORATORY
OF MINERALOGY AND CRYSTALLOGRAPHY

ANNUAL REPORT
No 10/2004

 

Editor: Dr. Nikola Zidarov; E-mail: nzidarov@interbgc.com
© Central Laboratory of Mineralogy and Crystallography, 2005

CONTENTS

Projects NoNo 5, 24 are financially supported in part by the Bulgarian National Science Fund of the Ministry of Education and Science. Project Ή 14 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 anniversary 10th year of its existence.The topics developed were in accordance with the preliminary specified scientific and applied priorities. The most important scientific results, a part of which were published or reported on scientific events, may be grouped as follows:

The most important achievements of practical importance are:

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

During 2004 the activity in CLMC was concentrated in 8 projects financed by the budget of the Bulgarian Academy of Sciences, 3 projects additionally financially supported by the National Council for Scientific Investigation, 1 project with NATO, 4 projects in the framework of the international collaboration, and 2 contracts with organizations in Bulgaria and abroad. The scientific results achieved by the stuff of CLMC in 2004 were reported in 79 publications in scientific journals and series, 41 of which in international and foreign journals and proceedings, and 30 in Bulgarian issues. The already published papers are 48 in number, whereas those in press are 31. Our colleagues have represented 43 reports in international and local conferences and symposiums, with 32 of them being presented on international and national conferences with foreign participation. Scientists from CLMC have presented 3 invited reports abroad.During the year, R. Petrova and S. Ferdov were graduated with a PhD degree, and a course in „Applied mineralogy" for M.Sc. degree was carried out for the purposes of the University of Mining and Geology „St. I. Rilski", Sofia.
 

Nikola Zidarov
Sofia, January, 2005

RESEARCH TOPICS:

I. MINERAL SYSTEMS AND ISOTOPE GEOCHEMISTRY

1. Mineral-petrologycal, geochemical and isotope studies of geological units in Serbo-Macedonian Massif, SW Bulgaria (N. Zidarov, I. Peytcheva, A. v. Quadt,
E. Tarassova, V. Andreichev)

New isotope data for the Igralishte and Yavornitsa granitoids from the most SE part of the Serbo-Macedonian Massif are obtained [48]. The Igralishte granite pluton is crops out over a territory of 32 km2 in the Ograzden Mountain. The prevailing part of the pluton is built up by porphyritic after plagioclase middle- to coarse-grained, two-mica to biotite granite. In the outer northern, eastern and western parts of the body a narrow band of leucocratic muscovite-bearing granite occurs. The transition between the two granite varieties is gradual, whereas the muscovite content increases gradually with the biotite decrease. In the periphery zones of the pluton resorbed amphibolite xenoliths are observed. Pegmatite, aplite and quartz veins cross cut the granite, as well as the host metamorphites. The main rock-forming minerals are plagioclase, K-feldspar, quartz, biotite and muscovite. The accessories are represented by sphene, ilmenite, magnetite, monazite, xenotime, zircon and garnet. Secondary products of the plagioclases and micas are the sericite, chlorite, epidote-group minerals. According to the TAS-classification the rocks of the Igralishte pluton belong to the subalkaline granites and the normal to subalkaline leucogranites, whereas the SiO2 content changes in the range 71.80 to 74.31% and the (Na2O+K2O) one – in the range 7.49-8.48%. According to the K2O content of 3.25-4.48% the granites belong to the high-K calc-alkaline magmatic series. The average ASI coefficient of 1.05 determines the rocks as low peraluminous S-type granites.

The timing of the Igralishte granite was especially important, as it is not metamorphosed and is weakly deformed, hence postdates the high-grade metamorphism in Ograzhden Mountain. We used U-Pb analyses on single zircons and monazites and ID-TIMS techniques for this purpose. Long prismatic beige zircon grains of sample A7 (two mica granite) were separated to avoid inherited cores, which are common in peraluminous granitic rocks. Some of the grains are additionally abraded to remove the outer parts, as they are usually enriched in uranium, the structure in these parts could be damaged by the radioactive decay of U and loose easier their daughter products – the radiogenic lead. Six zircons yield a discordia line (Fig. 1) with an upper intercept age of 240 +13/-9 Ma (MSWD 0.36), interpreted to reflect the time of the granite intrusion. The three abraded grains are almost concordant, one of them – concordant at 244 Ma. The non abraded zircons show lead loss, which we interpret as due from one hand to the active Alpine tectonic and the possible higher thermal gradient related to the Late Alpine volcanites in the region, and on the other hand provoked by the high U-concentration of zircons (1200-1500 ppm). The analyzed monazites are discordant also and the grade of discordance may be related to the high Th and U concentrations as well. The obtained electron microprobe dating of monazites from the same samples (see Tarassov et al. in this Ann. Report) give evidence for an almost mutual crystallization with zircons.

Cathode luminescent (CL, zircons) and BSE images (zircon and monazite) of both accessory minerals reveal a magmatic oscillatory zoning. The REE patterns of zircons (LA-ICP-MS measurements) are typical of magmatic rocks, but without or with a weak positive Ce-anomaly and with a weak Eu-negative anomaly. The latter is most probably due to the chemical peculiarities of the magma (fractionation of plagioclase), then to its oxidation characteristics.

Recrystallized areas of the zircon grains loose the light and middle REE or all REE – the concentration decreased one or two orders within these parts. One possible explanation is leaching by hydrothermal solutions as low-temperature diffusion is not enough to explain the considerable drop of the trace element concentration in these zircon parts.

Fig. 1. U-Pb Concordia diagram for zircons of the Igralishte pluton, sample A7.

Fig. 2. 87Rb/86Sr vs. 87Sr/86Sr diagram for biotite (Bi)
and whole rock (WR) fractions, sample A7,
Igralishte pluton.

Preliminary Rb-Sr data give evidence for Late Alpine overprint of the Igralishte granite: the slope of the two-point reference line WR-biotite corresponds to an age of 36.36 ± 0.56 Ma (Fig. 2). As the closure temperature of the Rb-Sr biotite isotope system is ³300°C, we need additional data for this thermal overprint; it is necessary to analyze other rock-forming minerals (Ms, Pl), which are more resistant to thermal overprint.

The calculated initial strontium ratio 87Sr/86Sri (T 240) of the whole-rock sample A7 of 0.70804 argues for a crustal dominated source of the granite magma of the Igralishte pluton.The presented new isotope data about the Igralishte pluton give evidence for Pre-Alpine intrusion of the Igralishte granite about 245 Ma ago with Late Alpine overprint, probably related to the Alpine tectonic and hydrothermal activity in the region.

Fig. 3. 87Rb/86Sr vs. 87Sr/86Sr diagram for biotites, plagioclase,
K-feldspar+plagioclase fractions, Yavornitsa granitoid.

 Yavornitsa granitoids (named by us), presented by several small igneous bodies of non-deformed fine-grained granitoids of a similar chemical composition and structure, crop out near the Yavornitsa village in Belassitsa Mountains. The main rock-forming minerals in granitoids are plagioclase of andesine-labradorite composition (An58-44 in cores and An50-40 in rims) (40%), amphiboles (magnesiohornblende and actinolite) and biotite (of magnesian type with Fe/(Fe+Mg) between 0.44-0.48) (totally femic minerals 20-25%), potassium feldspar (20%) and quartz (15%). The chemical compositions and mineral assemblages of the studied rocks correspond to the high-potassium calc-alkaline quartzmonzodiorite and quartzdiorite belonging to the magnetite series of the I-type. The igneous rocks have crystallized at pressures 3.1-4.5 kbar and temperatures 710-750oC (see Ann. Rep. 6/2000).

Rb-Sr analyses of separated biotites, plagioclase, K-feldspar+ plagioclase yield an isochrone with slope corresponding to 40.4±0.8 Ma (MSWD 0.22) (Fig. 3), which we interpret to reflect the time of intrusion of Yavornitsa granitoid bodies. The initial strontium ratio of 0.71068 argues for a crustal source of the magma. Obtained new isotope date give evidence for Late-Alpine magmatic manifestations in the region, which is in accordance with the previous presumption of its Paleogene age.

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

The potential use of radiogenic isotopes in the study of ore-forming processes was recognized by many geologists in the last years. There are two primary types of information available from these studies: age determination and isotopic source tracing. Studying the link magmatism-mineralisation and in cooperation with colleagues from ETH-Zurich and Sofia University we applied a combination of radiogenic methods to study the Cretaceous magmatic rocks in the region of Medet deposit – the first known Bulgarian porphyry copper type deposit. It is situated in the central part of the Srednogorie zone. Special attention was devoted to the basement rocks – metamorphites and Variscan igneous rocks with the aim to elucidate the role of both the crustal protoliths and the subcontinental mantle lithosphere as sources of the fertile magma. The region of Medet deposit is built up of high-grade metamorphic rocks (gneisses and rarely amphibolites), intruded by Variscan granodiorites and granites as well as by gabbro south of Medet deposit related by some authors to the Carboniferous magmatic complex; their opinion was later supported by K/Ar amphibole and biotite age of 255 and 256 Ma. The basement is also intruded by the rocks of Medet pluton – a small stock-like body (~3 km2), which is believed to represent the apical parts of a larger and deeper intrusive body (as the magnetic anomalies suggest). The pluton is emplaced at the intersection of the NNW-oriented Panagyurishte deep-seated fault zone with faults developed along the contact between the Paleozoic granitoids and the metamorphic basement rocks.

The evolution of the Cretaceous magmatism starts with the intrusion of gabbrodiorites to diorites 90.4 ± 0.5 Ma ago (U-Pb zircon data); closely after followed by the ore-bearing Q-monzodiorites and the amphibole and plagioclase granodiorite porphyries. The latter are cross-cut by aplitic veins with an age of 90.12 ±0.36 Ma (Fig. 1). Therefore, the magmatism in the deposit finished not later than 89.7 Ma ago (within the error uncertainties). An age of ~90 Ma is assumed for the Cu-porphyry deposit too, as the magmatic origin of the hydrothermal solutions is proofed by many authors.

Our preliminary U-Pb zircon analyses give evidence for an Early Palaeozoic age of the gneiss protoliths near Koprivshtitsa [sample AvQ010, 29].

For the Variscan basement very close ages reveal zircons of the Medet gabbro (AvQ014) - 305.55 ± 0.50 Ma (Fig. 2) and the Smilovene granite (AvQ109, 305.3 ± 1.3 Ma), as well as the monazites of the Koprivshtitsa granite (AvQ110, 304.8 ± 0.8 Ma). Furthermore the gabbro shows mixed crust-mantle characteristics, according to the eHf (300) zircon value of +0.14 and whole-rock initial strontium ratio of 0.7043. These data fit with the I-type affinity of the Smilovene and Koprivshtitsa granites and argue for a postcollisional formation of the studied Variscan igneous rocks.

Published data about the major and trace element geochemistry argue for island-arc character of the Upper Cretaceous magmatites in the region of Medet. Our new data are in agreement with them: the REE patterns of the newly sampled Cretaceous rocks are characterized by enrichment in LREE and flat or slightly depleted HREE. The Eu-anomaly is week or absent. The multi-element patterns are characterized by depletion in Ta-Nb, enrichment in LILE and by low values of HFSE, which is typical of subduction-related magmatic sequences. These data are compared with the geochemical characteristics of the host rocks in order to estimate the influence of the latter as a possible source for the Upper Cretaceous magma. Noteworthy is the similarity of the trace and rear-earth element distribution in the Variscan and Cretaceous magmatic rocks; in the basement rocks trace and rear-earth elements differ in patterns and content and give evidence for a different origin (crustal, mixed and mantle) of protoliths. Based on Sr-Nd-whole rock and Hf-zircon isotope data at least two magma sources should be constrained for the Cretaceous rocks in the Medet deposit: the subcontinental enriched mantle and the pre-Variscan basement, the latter revealing mantle as well as crustal characteristics. The Sr isotope characteristics change in a narrow interval around 0.70554, and e90 (Hf) values of the concordant zircons vary in the range from +2.9 to –0.2. The results of this investigations are published [13, 15, 16, 30, 54, 68, 70] and reported on conferences [101, 111, 112].

Fig. 1. Concordia diagram for zircons from aplitic
vein (AvQ-040), crosscutting the granodiorites
in Medet deposit.

Fig. 2. Concordia diagram for zircons of the gabbro
near Medet (AvQ-014).

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

Till now, the formation of the Chiprovtsi fluorite deposit is connected with the granites of the Variscan "Stara Planina calc-alkaline formation" (St. Nicola pluton), but a possible link to the Alpine thrusting and faulting comes recently into account. We applied a combination of isotope methods – Rb-Sr and Sm-Nd in order to date the deposit and to trace the source of the hydrothermal fluids.

Timing of fluorite deposits is always a tough problem. The reason is that it does not contain radiogenic elements in the amount, which is required to have enough radiogenic daughter elements and hence to obtain a reliable age determination. Published successful datings of fluorite deposits are based on examples, where fluorites contain higher amounts of radiogenic elements (Sm-Nd dating of Illinois-Kentucky fluorspar district, USA), or inclusions of other minerals (U-Th/Pb method on fluorites with inclusions of U-bearing minerals from La Azul fluorite deposit, Mexico). We used 8 fluorite samples representing different generation types. They are purple, green and grey colored, or colorless, milky. Two additional samples of the hosting marbles and diabases were also studied as possible sources of Nd and Sr for fluorites. On the 147Sm/144Nd vs. 143Nd/144Nd diagram (Fig. 1) the 8 measured samples do not determine an isochrone. The corresponding points lie mainly in the range 0.51235-0.51245 (eNd from -3.4 to -5.3) and argue for a crustal or a mixed (mantle-crust, but crustal dominated) source. The content of Sm in all measured samples is low (less than 3.5 ppm), hence the Sm147/ Nd144 ratio varies in a narrow range from 0.14 to 0.22. This fact makes it impossible to use the data for geochronological purposes, although the preliminary analyses of the first four samples (with highest Sm content) determined an errorchrone, whose slope corresponds to an age of 164 ± 27 Ma (see Ann. Rep. 9/2003).

The studied fluorite samples are extremely Rb-poor (Rb<2 ppm), respectively the 87Rb/86Sr ratios are lower than 0.12. Therefore, we can not use them for aging. There are two exceptions, which are related to possible overprinting processes. The two fluorite samples from level 495 determine a two-point reference line with an age of ~290 Ma; if we look at the Nd system characteristics of the same points, we see that they overlap with each other. Therefore, we excluded the use of Sr data for timing, too.

Fig. 2 shows the position of the studied samples on 87Sr/86Sr vs. 43Nd/144Nd diagram. The corresponding points lie in the field of the rocks, between enriched mantle fields EM1 and EM2. They suggest a source with mixed, but crustal dominated origin for the fluorites of the Chiprovtsi deposit.

Fig. 1. 147Sm/144Nd vs. 143Nd/144Nd diagram for fluorite samples
from Chiprovtsi deposit.

Fig. 2. Position of the fluorite samples from Chiprovtsi deposit
on the 87Sr/86Sr vs. 143Nd/144Nd diagram. DMM-depleted
mantle magma, HIMU – field of the mantle magma with
high m (206Pb/204Pb ratio), BSE – bulk silicate earth,
EM – enriched mantle. Fields of DMM, HIMU, BSE,
EM1 and EM2 after Faure, 2003)

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

A review of a large number of publications (over a hundred) on the carbonate-hosted sedimentary exhalative polymetallic deposits from Bulgaria and the world (Eastern Alps, Ireland, Canada, USA, Australia, Kazakhstan) has been undertaken as a first step of creating a detailed database of their characteristics for the aims of the planned comparative study. The database includes a wide range of various descriptive characteristics (quantitative and qualitative) of this type of ore deposits, arranged in several main groups: (1) geological – tectonic setting, host rock lithology, paleogeographic setting, shape and size of ore bodies, ore zoning, whole-rock alteration, etc.; (2) mineralogical – mineral composition, characteristics of ore and associated minerals, ore textures and structures, etc.; (3) geochemical – chemical composition of ore bodies (major, minor and trace elements), spatial distribution of elements and geochemical zoning, isotope data, etc.; (4) economic – reserves, resources, cut-off grade, production, prices, costs. Besides, objects of evaluation and classifying are also interpretative characteristics for the deposits including elements of their presumable genesis (sources of ore matter and ore solution, conditions and mechanisms of formation and alteration, ages and time-spatial relationships, stages of ore formation and alteration) and metallogeny (ore-controlling factors, criteria for prospecting and exploration). A detailed comparative characterization of this industrially important class of ore deposits is foreseen to be carried out on the basis of the summary data and models of their origin, formation and alteration as well as optimal parameters for evaluation and criteria for effective prospecting and exploration to be worked out.

5. Th-U-Pb electron microprobe age dating of monazite from Igralishte and Klissura granites: preliminary data (M. Tarassov, E. Tarassova, I. Peytcheva,
A. v. Quadt)

Preliminary data concerning the adaptation of the electron-microscopic technique available in the Central Laboratory of Mineralogy and Crystallography, Bulgarian Academy of Sciences (CLMC-BAS), to the purpose of electron microprobe dating, as well as the first results of electron microprobe dating of monazite from Igralishte (Ograzhden Block, Serbo-Macedonian Massif) and Klissura (Western Stara Planina) granites are reported in the present communication [35]. The control and assessment of the accuracy of electron microprobe dating were performed through comparing the obtained data with those of isotopic study (ID-TIMS) carried out in the Institute of Isotopic Geology and Mineral Resources (ETH-Zurich, Switzerland). The CLMC-BAS is in possession of a scanning electron microscope Philips 515 SEM, equipped with WDX-2A wave-dispersive spectrometer. The principle feature of the wave-dispersive system is that it permits the measurement of only one X-ray emission line during one and the same time. With regards to this, two analytical protocols were considered and applied in this work. The first one ("complete analysis") presents a conventional approach of electron probe analysis requiring the measurement of all elements whose content exceeds a definite detection limit of the method. In the studied monazites these elements were P, Si, Ca, Y, Th, U, Pb, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Yb. The second protocol ("partial analysis") involves measuring only of Th, U and Pb. The matrix corrections in the latter protocol are introduced using the data for the "average composition of monazite". The following X-ray lines, free of interference, were chosen: P Ka, SiKa, CaKa, Y La1, ThMa, U Mb, PbMa, LaLa1, CeLa1, PrLb1, NdLb1, SmLb1, GdLb1, TbLa1, DyLa1, HoLb1, ErLb1, and YbLa1. The most critical point of the considered methodology was the stability of the PET analyzing crystal employed for measuring ThMa, U Mb, and PbMa. To overcome the "crystal drift" we used the procedure including consecutive measurement of a reference sample, unknown sample and a standard, the reference sample and standard being of one and the same material. Age dating of monazite from Igralishte pluton. The ID-TIMS investigation shows that the monazites under study are discordant with apparent Pb/U ages varying between 170 and 223 Ma. The highest monazite age (223 Ma) is close to the zircon age (@ 240 Ma) as presented in Zidarov et al. (2004) and proposed to be the time of the granite intrusion. The electron microprobe dating performed by us shows a smaller age variation 210-247 Ma (average value being 224+13) and a better correspondence to the zircon age. Age dating of monazite from Klissura pluton. The ID-TIMS data give evidence for lead loss in the monazites which together with the studied zircons define a discordia line with an upper intercept age of 329±8 Ma (assigned as the age of magmatic crystallization), while the lower intercept with the concordia marks an Alpine event (62±17 Ma). The data of electron microprobe dating show the two groups of ages as well, being 290-317 Ma and 63-101 Ma, which is in a good agreement with the isotopic data. It should be noted that the increased contents of Th (up to ~14 wt.%) and U (up to ~ 1 wt.%) in the studied monazites allowed us to do the electron microprobe dating of comparatively "young" monazites (below 100 Ma) without any particular efforts and approaches. The present study shows good perspectives for the employment and development of electron microprobe dating in Bulgaria. Some of the results obtained need further detailed investigation and comparison with conventional isotopic methods.

6. Nanoscale structure and degree of defectness of natural zircons – a Raman microspectroscopic study (R. Titorenkova, B. Mihailova)

Zircon (ZrSiO4 – I41/amd, Z = 4) belongs to the group of metamict minerals, which are characterized with a high degree of structural disorder and coexistence of defect-rich crystalline and amorphous nanodomains, due to the radioactive decay of structurally incorporated U and Th. Radiation effects in zircon structure have important implication as alternative of borosilicates for actinide waste form and also in geochronology. Using Raman micro-spectroscopy (1.5 mm) different internal spatial areas as revealed by cathodoluminescence and back-scattered electron microscopy have been analyzed. The phonon modes of crystalline zircon are well studied. The increasing amount of radiation damages leads to a decrease in intensity, broadening and a shift to the low wavenumbers of the Raman-active modes of zircon. The position and the width of the peak near 1008 cm–1, generated by the n3(SiO4), are most sensitive to point defects and distribution in the Si-O bond lengths. The relative intensity of this peak indicates disruption of the translation symmetry in the zircon lattice. Extra peaks between 150 and 650 cm–1 indicate zircon structure decomposition and formation of ZrO2 phases on nanometric scale in heavily damaged samples. Additional well-pronounced peaks in the range 1100-1250 cm–1 that do not depend on the excitation light wavelength, are related to the amount of ZrO2 and could be due to the occurrence of chain-like clusters of linked SiO4 tetrahedra. The spectroscopic data show that the width of the peaks at 357 and 439 cm–1, originating from SiO4 rotation and bending mode, respectively, can be used for estimating the degree of nanoscale structural disorder of zircon (Fig.1).




Fig.1. Peak width versus peak position of the Raman signals near 1008 (a), 439 (b) and 357 cm-1 (c). The spectral parameters were determined by fitting the spectrum profile with Lorentz functions (Origin 6.1) and the measured FWHM were subsequently corrected for the apparatus slit according to Irmer (1985); the lines represent the linear fits of the experimental data.

According to the spectrum profile, zircon spatial regions are characterized with: (i) a low degree of structural damage consisting mainly in point defects; (ii) a medium degree of structural damage consisting in faults in the periodicity and formation of chain-like SiO4 species; (iii) a high degree of structural damage, consisting in changes in the mutual orientation between cation-oxygen polyhedra and chemical phase separation; and (iv) a structural state of initial recrystalization characterized with the existence of zircon nuclei [71, 117, 118, 119, 120].

7. Characterization of the ore mineralization in serpentinized ultrabasites near Tserovo village, Central Sredna Gora (Z. Tsintsov)

Serpentinites and the related ore mineralization (magnetite, chromite and sulphide) from Tserovo village, Pazardzhik district (Central Sredna Gora) are studied. Reaction products with varied mineral associations – talc, chlorite, tremolite anthophyllite, and vermiculite, are developed in the serpentinite body (outside parts) and along tectonically dislocated zones, which are favorable for infiltration of hydrothermal solutions. Sulphide mineralization in a quantitatively decreasing order is presented by monosulfide solid solutions (mss), pentlandite and pyrite. It is observed in the light-yellow, hydrothermally altered ultrabasites and is mainly presented by complex intergrown aggregates of mss and pentlandite and single xenomorphic grains of pyrite. The aggregates of the system mss-pentlandite have irregular or oval shape and are sized from 5-6 to 20-30 μm. The composition of mss includes (wt %) Fe from 59.98 to 61.06 and S – from 38.17 to 39.73. The data shows variation in the crystal chemical formulae and the presence of monoclinic and hexagonal pyrrhotite. The composition of pentlandite includes (wt %) Fe (30.95 to 31.95), Ni (32.78 to 33.75), Co (0.44 to 0.78), and S (34.04 to 34.31). The Ni/Fe atomic ratio varies in a relatively narrow range – from 0.98 to 1.03. The formed structures in the described system (mss-pentlandite) are flame-like and lamella-like types. Pyrite is very rarely observed. Its composition is very pure with a stoichiometry close to the theoretical one of the mineral. The ultrabasites from the region near Tserovo village are intensively altered. The low-temperature hydrothermal metamorphism had influenced greatly the formation of the prevailing part (excluding chromite and part of magnetite, which are of primary magmatic origin) of the investigated ore mineralization. The irregular distribution of magnetite and the sulphide minerals in the different parts of the body indicates for a local variable conditions for f(S2) and f(O2) in the process of crystallisation. In this case f(O2) was dominating. Short in continuation and limited in space was the increased f(S2), which had caused a weak and locally distributed sulphide mineralization. The system mss-pentlandite is a result of dissociation of solid solutions formed below 150°C. Probably, it had emerged in the last stage of postmagmatic changes of the ultrabasites. Pyrite formed in different strongly limited in space conditions. The sulphide crystallisation had caused a quick depletion of S, change of the physico-chemical conditions, and abundant formation of magnetite. The needed iron for the formation of the hydrothermal ore mineralization had been released from the primary rock-forming minerals of the ultrabasites, where it is presented mainly in a divalent form. The earlier formed pentlandite and Ni-containing minerals could be considered as probable sources of Ni [4, 80].

8. Heavy minerals concentrates map of Bulgaria at 1:25 0000 scale (O. Vitov)

A dividing of Momchilgrad Depression (Eastern Rhodopes) based on heavy minerals concentrates data was made and target prospects for mineral deposits were outlined [11, 12]. It was established an unknown till now spatial regularity of striped pattern of gold from heavy minerals concentrates samples taken in Eastern Rhodopes (Fig. 1) [75, 121].

Fig. 1. Striped pattern of gold distribution from heavy minerals concentrates samples taken in Bulgaria (I); in Eastern Rhodopes (II) and in Momchilgrad Depression (III). A – on heavy minerals concentrates data and with geological background; B – full Furier-model.

IA

IB

 

IIA

 

IIB

 

IIIA

 

IIIB

The geological blocks detached on tectonic data were characterized by their heavy minerals composition and their features were specified as follows. The Central Rhodopian Dome is characterized with monazite and galena; the Kesebir Dome – with scheelite, kyanite, gold and monazite; the Biala Reka Dome – with scheelite, gold and chromite; the Sakar Block – with rutile, ilmenite and scheelite and the Eastern Phodopian depressions – with barite, chromite and monazite [47, 122].

Table 1. Comparison between Eastern Rhodopes blocks by mineral composition
of the heavy mineral concentrates samples (Kolmogorov-Smirnov, a<1%, Cheeney, 1986).

*sup – superior difference; Ksm – critical difference;
K=sup/Ksm; N1, N2 – number of samples in both distributions.

The comparison made between the blocks (Table 1) shows significant diversions in the composition of heavy minerals concentrates samples, which points to a possible accretion model of the Eastern Rhodopes building. The dividing of the total area in basic areas of 4 km2 each, and their further comparison by mineral composition at a different critical range allowed us to divide a lot of areas, homogeneous in heavy minerals aspect (Table 2).

Table 2. Dividing of Eastern Rhodopes in mineralogically homogeneous areas (N)
by heavy minerals concentrates samples at different critical range a.

9. Sperrylite from alluvial sediments of Vurbitsa river in the region Dobromirtsi village – Momchilgrad town (Kurjali district), SE Rhodopes (Z. Tsintsov)

Studies on the mineral composition of the heavy mineral concentrates from placers associating with closely situated ultrabasic bodies in SE Rhodopes proved the presence of PGM in them also. The alluvial sediments of Vurbitsa river in the region Dobromirtsi village – Momchilgrad town (SE Rhodopes) are elsewhere "infected" with sperrylite, accompanied by single finds of alloys of the platinum-group elements (PGE) (iridium and ruthenium) only in the alluvial depositions disposed near the ultrabasites of the Dobromirtsi massif. The heavy mineral concentrates taken from the studied region consist mainly of magnetite, chromite, ilmenite, rutile, almandine, zircon, native gold, rarely of monazite, native silver, Au-Ag amalgama, uraninite, cinnabar, very rarely PGM, etc. The grains of sperrylite are concentrated in fractions <63 mm. Their form is isometric or elongated and they are tin-white to dark-gray colored and with apparent metal luster. Sperrylite grains are subdivided in two types in respect to the degree of mechanical processing during the exogenic transport: very strongly or relatively weakly processed. The two types are regularly represented in the various parts of the studied sediments. The natural surface of the grains from the first type is dense and smooth – very well polished during their mechanical transportation in the placer. The samples from the second type are represented chiefly by relatively well preserved combinational crystals or crystal parts composed of forms with indices a {100}, o {111}, rarely d {110}, etc. The polished surfaces of the grains from both types are disturbed by plenty of caverns with irregular form and sized up to 5-6 mm. The composition of the studied sperrylite includes only the constitutionally regulated elements of the mineral (according to data of microprobe analyses). The Pt content is in the range (wt. %) from 55.26 to 59.06, while that of As – from 41.42 to 43.22. Indications for presence of Ni were noticed in several samples but its content remained steadily under the detection limits of the analysis. Some of the grains have stoichiometry corresponding to the theoretically calculated one for this mineral – PtAs2. The rest samples display some metal excess not correlated with their morphology. Inclusions of other phases in the studied grains were not observed [41]. The hydrothermal solutions that took part in the metamorphic alterations of the ultrabasites in SE Rhodopes probably were the reason for Pt immobilization from earlier formed minerals. At the same time the, solutions carried As needed for the formation of sperrylite. The later exogenic processes caused its disintegration from ultrabasites and deposition in the alluvial sediments of Vurbitsa River.

10. National Mineralogical Database – level of realization (N. Zidarov,
V. Stoilov, I. Marinova)

The building of a National Mineralogical Database (NMDB) started in 2003, following the accepted modular structure and stages (Ann. Rep. 9/2003) [125]. During the last year one completed the first stage of the project – creation of a Bibliographic Database (module A). It is an electronic catalogue of the published papers on Bulgarian minerals. The realization is as a table in Microsoft Access media, which allows sorting and searching to be made using assigned criterion like author, year of publishing, period of time, title, mineral name, and mineral locality. The major sources of mineralogical information in Bulgaria have been considered. The total number of the titles covered for the period from 1844 to 2003 is 3200. The layout of the Bibliographic Database is shown in Fig. 1.

The Bibliographic Database is accessible on the web-site through the Central Laboratory of Mineralogy and Crystallography. Forthcoming is the realization of the second module: Factual Database. Its preparation has started with collecting about 1800 bibliographic units on a paper bearer, each included under an unique number in the Bibliographic Database in a column, named "Separates".

11. Oligocene reef limestones from Momchilgrad depression, East Rhodopes
(E. Tarassova, M. Tarassov, Ek. Dimitrova)

New data on organogenic limestones with scarce pyrite mineralization from the Metlichki reef located to the east of Plovka village are presented. The main mineral composing the limestones is calcite displaying crystals with variable dimensions which most probably indicates the initial heterogeneous texture of the sedimentary rock. In small amounts also presented are quartz (3-10 %), potassic feldspar (1-3 %), magnesian calcite (<1%), plagioclase, sericite, pyrite, marcasite, illite, goethite, and kaolinite. Magnesian calcite is identified in the powder diffraction patterns of the rocks by its characteristic reflections in the range 0.301-0.295 nm. Pyrite is a diagenetic mineral that forms idiomorphic crystals distributed jointly with the organogenic remains. Marcasite is encountered as overgrowths or intergrowths with the pyrite crystals. The relationships between the iron sulphides indicate unstable regimes of pH and Eh in the surrounding medium during consolidation and recrystallization of the sediments. The studied limestones contain (in wt. %) CaO 40.95-50.96, SiO2 4.02-16.94, Al2O3 1.86-5.13, FeO 0.41-1.96, K2O 0.3-1.0, MgO 0.76-1.18. Minor elements are presented by Pb, Zn, Cu, As (with contents up to 100 ppm), Ni, Co (up to 50 ppm), Ag (up to 3 ppm), and Au (0.1–0.17 ppm). The elements Ca and Mg are related to the organogenic carbonate relics, while Al, Si, Ti, Fe and the rare ore elements originate from terrigenous material in the limestone. Organogenic detritus in the limestones sized in the range 0.3-2.4 mm, comprises 20-60 % of the rock volume and is cemented by microgranular calcite (< 200 ΅m). In the limestones sampled near to Plovka village for the first time is established Nummolites vascus Joli et Leim that is indicative for the Oligocene age. With considerable participation in the limestones are the microfossils of the families Lagenidae, Miliolidae (Triloculina sp., Spiroloculina sp. and Pyrgo sp), Crinoidae (Fig. 1).

Fig. 1. Micrographs of Nummulites vascus Joly et Leim and Crinoidae from reef limestone near Plovka village, obtained in transmitted light: (a) image in parallel nicols, (b) image in crossed nicols – symmetrically-sectorial structure of the calcite aggregate inherited from the Nummulites skeleton is clearly observed.

The association includes also the specimens of Lenticulina sp., Bolivina sp., Anomalina sp., Dorothia crassa (Cushman) and other Textulariidae. Rarely are encountered the sections of Planorbulina cretae (Marsson) and Sphaerogipsina cf globuls (Reuss). The obtained new data on the Metlichki reef limestones – their mineral composition and the identified organogenic detritus, provide a possibility for lithological correlations with organogenic limestones from other regions of Bulgaria [37].

12. Sensitivity assessment of different grids for soil geochemical surveys using "Monte-Carlo" simulations (O. Vitov, I. Marinova)

Traditionally, the geochemical surveys are used to direct the prospecting for large deposits, which could be found out by applying standard rectangular grids, which have been approved by the long-term experience. However, the running out of the major large deposits, outcropping on the surface, shifted the attention to prospecting for smaller deposits, too. And this is a world tendency. The efficient soil geochemical surveying for smaller deposits requires a careful choice of sampling framework, which accounts for the shape, size and direction of expected geochemical anomalies considering the geological setting. In order to choice an optimal grid-based sampling framework for certain geological setting it is proposed a comparison between appropriate grids, based on the "sensitivity" parameter, to be made [46]:

where Pa is the probability a given grid to hit geochemical anomalies with one grid-point at least, and Po is the probability this grid to miss them. The sensitivity T ranges from -₯ to 1. For low sensitivities (negative values) the misses are more than the hits; at T=0 the probabilities for hitting and for missing the anomalies are equal (i.e. 50/50). At T=1 we are sure that there is no misses.

Table 1. Probability of a 500x100 m grid to hit ellipsoidal geochemical anomalies
sized 1200x300 m at a change of their direction by a step of 5o in the range 0o-175o

Here, various grids are tested for certain region by "Monte-Carlo" method, including the shape and size of expected geochemical anomalies at a random choice of anomalies' place and direction. The outcomes are given in a table, shown on histogram and circular diagram with a view towards comparison of the grid variants based on their "sensitivity". To illustrate the described procedure we analyzed the case of a virtual soil geochemical survey extended within a 50x50 km2 area, including both 7200 circular and ellipsoidal anomalies, sized so as to correspond to small gold deposits (1 t gold resources). The centre of each anomaly was determined by a standard generator of random numbers. The anomaly's direction was changed from 0o to 355o with a step of 5o, 100 anomalies were simulated for each step. The 500x100 m and 250x250 m grids were plotted in the virtual square.

The computer simulation shows that the outcomes of both grids are similar for circular anomalies. For ellipsoidal anomalies, the anomalies' direction influences the outcomes.

Table 2. Probability of a 250x250 m grid to hit ellipsoidal geochemical
anomalies sized 1200x300 m at a change of their direction by a step
of 5o in the range 0o-175o

The rectangular grid discovers ellipsoidal anomalies usually with 5 and 6 points, but there are misses of such anomalies, when they are parallel to the grid-lines (Table 1). That effects over the sensitivity of the 500x100 m grid – it is 0.947. The square grid discovers ellipsoidal anomalies usually with 4 and 5 points and there is no misses (Table 2). Because of finding out every simulated anomaly, the square grid shows maximum sensitivity of 1.00. The "Monte-Carlo" simulations show that at an unclear and/or variable direction of geochemical anomalies the square grid is more sensitive (more effective respectively). This finding supposes to make a revision of all soil sampling surveys for gold carried out in Bulgaria so far and a reassessment of the potential of missed gold anomalies.

13. Determination of the provenance of newly discovered archaeological monument (L. Macheva)

A stone slab bearing an inscription "Samuil – tsar and samodrzhets vsem blgarom" (Fig. 1) was found on 25 March 2004 in the vicinities of the village Samuilovo. At present it is kept at the Historical Museum in Blagoevgrad. On request of the latter, a detailed petrological and mineralogical investigation was carried out at CLMC-BAS to determine its provenance. Minor piece of the slab is sampled and studied using polarizing petrographic microscope, scanning electron microscope and X-ray powder diffractometer.

The petrological examination reveals that the rock is a serpentinized peridotite, composed mainly of coarse relics of olivine and tremolitic amphibole in a fine-grained chlorite-serpentine matrix. Talc and magnetite (up to 1%) are also present as minor constituents. The texture of the rock is pseudorelictic to relict-granular after olivine and amphibole, mesh texture in relation with the net-vine-like pattern of the serpentine minerals cutting off the olivine aggregates, nematoblastic after amphibole and heterogranular after serpentine and chlorite minerals.

Fig. 1. Stone slab bearing an inscription “Samuil – tsar and samodrzhets vsem blgarom”

On the basis of mineral relationships and mineral chemistry a conclusion can be drawn about the geological evolution the rock has undergone. We consider that the rock had been metamorphosed under amphibolite facies conditions at elevated temperatures and medium pressure, during which olivine (under Tmin~400 0C) and tremolitic amphibole (under Tmin~500-550 0C) were consistently formed. On the peridotites already metamorphosed in amphibolite facies a low temperature greenschist metamorphism is imposed, with which a repeated episode of partial serpentinization is associated. During this retrograde metamorphic stage the crack-filled replacement of olivine and tremolite by chrysotile is realized as well as the appearance of the isotropic platy serpentine (lizardite). Chlorite and talc were also formed. It is well documented that metamorphosed ultrabasic rocks, identical with the studied specimen from the stone slab in question, build up lenticular and lense-like bodies on the northern slope of the Belassitsa mountain (to the south of the village of Samuilovo, between Kliuch and Yavornitsa villages, as well as southerly to the village Kolarovo). On the account of this parallelism and of our investigations we conclude that the inscribed stone slab which, according to the archeologists, served as a border stone of the mediaeval kingdom of tsar Samuil, is most likely to originate from the metamorphosed ultrabasic bodies in the immediate vicinity.


II. ENVIROMENTAL MINERALOGY

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

The phase-mineral and chemical composition of ceramic cenosphere and water-soluble salt concentrates [43], magnetic and char fractions [42], as well as of heavy concentrates and improved fly ash residues [74], recovered from five fly ashes (FAs) produced in four large Spanish thermo-electric power stations (TPSs) was characterized for a multicomponent, wasteless and environmentally safety utilization of such FAs. Low-cost catalytic sorbents for NOx reduction, based on chars and activated chars obtained from a low-rank Spanish coal and doped with vanadium compounds and petroleum coke ash, were tested with the addition of ammonia as reducing agent. The sorbents have shown to be active for NOx reduction at low-temperature (150 °C) and the most efficient sorbents are those prepared from activated chars [21]. Some environmental aspects related to water-soluble fractions leached from Bulgarian coals and FAs [44], as well as to sulphur emissions during combustion of Bulgarian coals [45], were studied. It was found that some mobile trace elements from coals (Cl, Cu, Mn, Pb, Zn) and fly ashes (Cl, Cu, Pb, Zn), as well as some acid coal solutions (Maritza East, Pernik, Bobov Dol) may contaminate the surface and subsoil waters, soils, and plants in the areas surrounding the coalmines, fuel depositories at preparation plants and TPSs, and FA disposal sites [44]. The mechanism of S emissions and their capture during combustion of some Bulgarian coals (Maritza East, Maritza West, Sofia, Pernik, Bobov Dol, and Balkan) were studied. The data indicate that the traditional pulverized combustion (1200-1600°C) of the high-sulphur Bulgarian coals in TPSs is inadequate from an environmental point of view and other alternatives should be applied [45]. The phase-mineral and chemical composition of feed coals and their bottom ashes and FAs produced in the Soma TPS (Turkey) was characterized. Some genetic features, properties, possible environmental concerns, and potential utilization directions related to these fuels and their solid combustion products were described [72]. Six fractions were recovered from FAs produced in the Soma power station and their phase-mineral and chemical composition was characterized. The following fractions were isolated: (1) char concentrates (CCs); (2) light fractions (<1 g cm-3) (LFs); (3) water-soluble residues (WRs); (4) magnetic fractions (MFs); (5) nonmagnetic coarse-grained fractions (>63 ΅m) (NCFs); and (6) nonmagnetic fine-grained fractions (<63 ΅m) (NFFs). It was found that possible environmental concerns are related mainly to the trace element mobility in WRs, LFs, and CCs, while the potential utilization directions are connected mostly with the composition of MFs, WRs, CCs, LFls, and NFFs [73]. Additionally, the variations in FA composition [55] and mass balance of major and trace elements [56] in the Soma TPS were also characterized.


15. Chemical Durability Testing of the Synroc-like crystal matrix (I. Donchev, B. Zidarova, N. Lihareva, N. Zidarov)

During synthesis of Synroc type crystal assemblies using XRD and SEM analysis we proved the formation of phases analogues of zirconolite, a hollandite like phase, perovskite, and non reacted badeleite and rutile.

Crystal-chemical calculations for the perovskite structure show that it is very similar in its structure-chemical parameters to uhligite – (Ca2.14, Sr0.57, Sm0.33, Nd0.44)3.44 [Ti3.86Al0.28]4.14 O12. Perovskites with incorporated in its lattice radionuclides are with Pnma symmetry and the reduction of the symmetry from cubic to orthorombic is explained with Sr presence in octahedral sites, substituting a part of calcium. The symmetry of zirconolite formed in the Synroc-like material does not differ from the phases with incorporated Nd, Sm and Sr. For hollandite rutile and badeleite there is no available microprobe data (Table 1).

Table 1.

The experiments on testing of the chemical durability of the crystal lattice of zirconolite and perovskite from the Synroc-like testing bodies with incorporated Sr, Sm and Nd are carried out in two ways:

The experiments of the first type were carried out at room temperature (22°C) and five solutions with acidic and alkaline composition (H2SO4, NaCl, CaCO3, CaCO3 + NaOH) are used, as well as of water extracted solution from marls of Lower Cretaceous age from Gorna Oryahovitza Formation (Table 2).

Table 2.

* - not analysed ; + - semiquantitative estimation ** Analyser - prof. R. Djingova, Sofia Univ. Chem.faculty, Dep.of Radiochemistry

The high temperature leaching is performed in steel autoclaves with embedded Teflon vessels of 25 ml volume for isolation (according to the rules for hydrothermal synthesis). The autoclaves are heated in electric furnace at 180° ± 2 °C for 72 hours. The solutions obtained after high temperature leaching are analyzed by ICP-AES for quantitative determination of the content of Sm and Nd and for qualitative determination of Ti, Zr, Sr and Ba. The error of the analysis is below 2%*. Usually, Synroc matrices are investigated for degree of chemical durability with deionisated or distilled water at 90 °C – the so called MCC (Materials Characterization Center) tests. The accent of our work is on the concentration of REE in the solutions with different values of pH after the leaching, without registration of the mass loses from the crystal matrix. The preliminary results demonstrate (table 2) that in acidic medium at elevated T and P greater quantity of Nd (3 to 5 times) and Sm (2 to 8 times) passes in the solutions compared to the case at ambient temperature and pressure. In alkaline medium – Sm is 15 times more and Nd up to 2 times more. It should be noted that Nd in sample 2 in both treatments shows anomalous values, which are probably due to the higher solubility of the Synroc-like material in hydrochloric acidic medium. The analysis of the data from leaching in water extract from marls shows that Nd is with higher concentration compared to that in CaCO3 solution (pH = 7.20). This elevated solubility also might be due to salinity of the water extracted leachate, whose alkalinity is due to the high content of Na salts (carbonates, sulphates) and of NaCl. The leaching degree of Ti in the same sample is many times higher compared to the other samples, while Zr leaches intensively in the medium with NaOH. The Ti content solved in these alkaline conditions possibly comes from rutile, which is present in the Synroc-like matrix and is unsustainable in a medium of alkaline carbonates. On the basis of the obtained preliminary results the following conclusions may be drown:


16. Application of the BCR extraction procedure for study of metal distributions in waste water slurries and sediments (N. Lihareva)

In this work the BCR extraction procedure was applied to sewage sludge samples and sediments, collected from selected sites before and after the effluent of urban waste waters in a river and wastewater treatment plant. In the first step the water soluble fraction was investigated. The next step yield information on metal fractions associated with: 1) carbonates; 2) easily and moderately reducible iron and manganese compounds; 3) organic matter and sulphidic phases; and 4) residual silicate fraction. The total concentrations of macroelements (Mg, Ca, K, Na and Al) and trace elements in the samples, the obtained extracts and the remaining solid residues on different steps were measured by FAAS. Matrix interferences were investigated by use of a standard addition method, applied to extracts with different extractants and digests. No significant interference was found in the determination of the elements (i.e. the recovery of added standards was 100±10%). However, signal increasing of about 20% occurred in 1 mol. L-1 of ammonium acetate solution. The distribution patterns of the major and trace elements were created. It was found that the distribution patterns of elements in sewage sludges differ considerably from those in sediments. Cu and Pb behave similarly and are found mainly in the organic and in the residual silicate phases. Significantly great proportions of the content of Cd and Zn were found in reducible and carbonate fractions. Small amounts of these elements were found in the remaining solid residue. Mn and especially Fe are retained in the residual silicate phase. In the extractable part the greatest portion of Mn was found in the carbonate phase. In contrast, in the not contaminated sediment the heavy metals were evenly distributed among all fractions with a significantly low proportion in the organic and sulphidic fractions. The accuracy estimated by comparing the total metal concentration with the sum of extracted amounts and solid residue was satisfactory for this analysis (recovery 86% - 111% for the major and 76% - 139% for the trace elements). The precision expressed as RSD values varied over a wide range and depends on the element concentration and the extraction step. It is worse for elements of low contents and in the fractions where the extracted amounts of elements were near or below the detection limit. The results of this work are presented on the 5th National conference of chemistry [96].


III. MODELING AND MODIFICATION OF MINERAL SYSTEMS

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

In earlier publications and annual reports we defined the geometric images of chemical and mineralogical objects and clarified some basic aspects of the relation between mineralogy and geometry [25, 26, 64, 104]. This allows us to make another important step toward the real geometrization of the language of mineralogy introducing the notions equivalency and similarity of geometric figures, which play a basic role in geometry. Therefore using the worked mathematical apparatus and the introduced fundamental notions chemical point, chemical graph, mineral graph and elementary mineral graph (i.e. elementary cell) (see Ann. Rep. 7/2001) we formulated in a general form one entirely geometrical criterion for equivalency in VS(6) of elementary cells of mineral objects (individuals respectively theirs aggregates). Criterion for equivalency: The elementary cells of two mineral objects A and B (i.e. the elementary mineral graphs  and  of two mineral objects) are equivalent then and only then when there exists such a combination  of translations and rotations in the ordinary physical space VE(3) that transforms the geometrical image  in VS(6) of the elementary cell of one mineral object into the geometrical image  in VS(6) of elementary cell of other mineral object. This entirely geometric criterion for equivalency can be expressed mathematically in the following way:

such that 

where:  is the operator of translation at a distance a along the u-dimension of VE(3);  is the operator of translation at a distance b along the v-dimension of VE(3);  is the operator of translation at a distance c along the w-dimension of VE(3); , ,  are operators of rotation by angles a, b and g in VE(3). From the formulated criterion for equivalency it becomes clear that the elementary cells of the equal mineral graphs differ from one another only in their first triad of coordinates defining the position in VE(3) of elementary cells of the corresponding mineral objects, represented geometrically by the respective mineral graphs. The question for defining the basic geometrical notion similarity for mineral objects is much more complex and is narrowly connected with the question for investigation of this transformations in the spaces of chemical structures Vs(6) which are possible from the chemical point of view. However, we should explicitly note that before formulating mathematically any criterion for similarity of chemical and mineralogical objects, one must firstly clarify logically correctly in chemistry and mineralogy the question "when two objects can be considered similar?" Only then, one may think about formulating a mathematical (and in particular geometrical) criterion for similarity of chemical and mineralogical objects. According to us, as a direct point for a future clarification of this question one can accept the following hypothesis:

HYPOTHESIS: Two mineral objects are assumed as similar, if:


18. Synthesis and characterization of microporous titanosilicates
(S. Ferdov, V. Kostov-Kytin, O. Petrov)

At constant time (24 h), temperature (200 °C) and using one and the same chemical reagents, only by varying the chemical composition of the initial gel we were able to synthesize ten titanosilicate phases - six microporous [ETS-4, ETS-10, STS (AM-2), titanosilicate analogue of the mineral sitinakite, titanosilicate analogue of the mineral pharmacosiderite (GTS-1) and rombohedral titanosilicate analogue of the mineral pharmacosiderite], two layered [JDF-L1 (AM-1), AM-4] containing water molecules and two dense titanosilicate (natisite, paranatisite) [87]. The synthesis of the layered titanosilicate AM-4 was the only one that required time for crystallization over 24 h. For most of the phases are determined crystallization fields by varying the quantities of Na2O, Na2O/K2O, K2O and TiO2.

Figures 1-3 show the crystallization fields of ETS-4, GTS-1, STS (AM-2), ETS-10, titanosilicate analogue of the mineral sitinakite, JDF-L1 (AM-1), AM-4 and the dense titanosilicate natisite. Except AM-4 all phases are synthesized for 24 h. It can be seen (Fig. 1) that in the field of crystallization of AM-4 after synthesis for 24 h the run product is presented by a mixture of AM-4 and GTS-1, which after the 96th hour is completely transformed into flake-shaped particles of AM-4 (Fig 4, a). In each crystallization field variations in the morphology were observed depending on the initial quantities of Na2O, K2O, Na2O/K2O and TiO2. The main morphological difference between the synthesized phases is in their presence as polycrystalline particles or single crystals. In the synthesis of ETS-10 and JDF-L1 the variations in the initial batch composition has no significant effect on the morphology and these two phases appear only as single crystals or their aggregates (Fig. 4 b, c).

ETS-4 was observed mainly as polycrystalline particles (Fig. 4 d) and for GTS-1 and the rhombohedrally distorted titanosilicate analogue of the mineral pharmacosiderite it was not possible to observe any crystals. In the case of STS (AM-2), enhancement in the initial amount of KOH leads to a change from polycrystalline particles to pseudohexagonal single crystals (Fig. 3 and 4 e, f).

Fig. 4. SEM images of microporous titanosilicates showing the main morphological differences between the phases obtained from gels with composition corresponding to their crystallization fields.

Using the rapid method for low-temperature synthesis the microporous titanosilicate Na-GTS-1 was hydrothermally synthesized in the system Na2O-TiO2-SiO2-H 2O [7]. The as-synthesized nanocrystalline material (<10 nm), was characterized by XRD, SEM, TG-DTA, as well as by IR and Raman spectroscopy. It is shown that on heating Na-GTS-1 undergoes a gradual decrease of the degree of crystallinity accompanied by a process of amorphization (up to 600 °C) followed by transformation into a mixture of Na2TiSi2O7 and unknown phase/s [88].


19. Characterization of novel synthetic zirconosilicates (V. Kostov-Kytin,
Yu. Kalvachev, S. Ferdov, U. Kolitsch, O. Petrov, C. Lengauer, E. Tillmanns)

Hydrothermal syntheses held in the system Na2O – ZrO2 – SiO2 – H2O at 200ΊC and without using organic additives in the reaction mixture led to the preparation of seven phases with or without natural analogues: the layered NaSi11O20.5(OH)4.3H 2O and the zirconium-rich Na2Zr7Si2.5O20 .3H2O; the microporous Na2ZrSi3O9.2H 2O, Na2ZrSi3O9.H2 O, Na4Zr2Si5O16 .2H2O; and the dense ZrSiO4 (zircon) and Na8Zr3Si6O22 . Pure crystalline samples of the novel Na2Zr7Si2.5O20 .3.5H2O, Na4Zr2Si5O16 .H2O and Na8Zr3Si6O22 have been characterized by microprobe analysis, powder X-ray diffraction, scanning electron microscopy, thermogravimetric-differential thermal analysis, infrared and Raman spectroscopy [92, 86]. Taking into account the spectroscopic investigations (Fig. 1, Fig. 2) it is thought that Na2Zr7Si2.5O20 .3H2O is a phase with layered structure, Na4Zr2Si5O16 .2H2O is a microporous phase and Na8Zr3Si6O22 is a phase with dense structure. In the course of optimizing the reaction conditions it has been found that sodium zirconosilicates of promising properties can be prepared in alkaline medium by finely tuning the molar ratios of the initial gel. Syntheses held in reaction medium of high acidity or high basicity result in the formation of phases with dense structures.

Fig. 1. A - infrared absorption spectrum of Na2Zr7Si2.5O203H2O. B - infrared spectrum of Na4Zr2Si5O162H2O heated at 100 °C for 1 hour and subsequently cooled to room temperature does not give any evidences for changes in the water state. Such behavior suggests rehydration properties of this material. C - infrared spectrum of Na8Zr3Si6O22 heated at 100 °C for 1 hour and subsequently cooled to room temperature does not give any evidence for structurally bound water.

Fig. 2. A - Raman spectrum of Na2Zr7Si2.5O203H2O. The peak near 935 cm-1 originating from the Si-O bond stretching is of relatively low intensity because of the high Zr/Si ratio. B - Raman spectrum of Na4Zr2Si5O162H2O. C - Raman spectrum of Na8Zr3Si6O22. The peaks related to the stretching modes of SiO4 tetrahedra are positioned at lower wavenumbers as compared to Na2Zr7Si2.5O203H2O and Na4Zr2Si5O162H2O, which indicates more swelled SiO4 groups.

When using BaCl2 as reagent in the Zr-system we were able to obtain single crystals of a new microporous zirconosilicate, which was named MCV-2 (Mineralogy and Crystallography Vienna). MCV-2 - Ba2Na(Na0.5,(H2O) 0.5)2Zr2Si6O 19·3H2O represents the first example of a Ba-Na-zirconosilicate and possesses a crystal structure which is unique among the mixed octahedral and 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) Ε, V = 4173.8(13) Ε3, 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 [51].


20. Investigation of the thermal stability of the layered titanosilicate -JDF-L1 (V. Kostov-Kytin, B. Mihailova, S. Ferdov, O. Petrov)

Layered titanosilicate JDF-L1 is synthesized in the Na2O-TiO2-SiO2-H 2O system applying a rapid procedure and without using organic additives in the synthesis mixture. The thermal evolution of the JDF-L1 structure is studied by thermogravimetric-differential thermal analysis, powder X-ray diffraction and Raman spectroscopy (Fig. 1, Fig. 2). Upon thermal treatment JDF-L1 undergoes reconstructive phase transitions involving order-disorder-order processes and resulting in formation of narsarsukite, Na4Ti2Si8O22, as a final dominant phase [20, 91]. The thermal evolution of JDF-L1 consists of three main stages:

Fig. 1. Powder XRD patterns of as-synthesized JDF-L1 and JDF-L1 heated in ambient atmosphere at different temperatures. The samples were heated at each temperature for 2 hours, except at 550 and 580 °C where the duration of thermal treatment was 1 h. For clarity the patterns of samples heated at 580, 600 and 700 °C are multiplied by factor of 3. The asterisks mark the positions of opal reflections.
Fig. 2. Raman spectra of as-synthesized JDF-L1 and JDF-L1 heated in ambient atmosphere at different temperatures. The samples were heated at each temperature for 2 hours, except at 550 and 580 °C where the duration of thermal treatment was 1 h. The arrows mark the main Raman signals for samples heated at 580 ?C. The spectrum of the sample heated at 700 °C is the same as the spectrum of narsarsukite. The insert presents the two types of SiO4-rings characteristic for JDF-L1 and narsarsukite, respectively.

1. A low-temperature range that is characterized with a gradual decrease in the interlayer spacing caused by the two-stage removal of H2O molecules and accompanied by topological changes in the Si-O entities and layer undulation. 2. An intermediate, narrow-temperature range of critical phenomena, namely: a collapse of the JDF-L1 framework and a subsequent formation of X-ray amorphous Ti-rich phase/s, partially disordered microcrystalline silica, and nucleation of narsarsukite; 3. A high-temperature range characterised with atomic rearrangements in the matrix of non-crystalline alkali titanate-titanosilicate spatial regions and silica microcrystallites resulting in enhanced crystallization of narsarsukite.


21. Synthesis of kenyaite in Zr-containing reaction medium (V. Kostov-Kytin, Yu. Kalvachev)

Synthetic kenyaite is prepared in the system Na2O–ZrO2–SiO2–H 2O, without using organic reactants [57]. It is characterized by powder X-ray diffraction (Fig. 1), scanning electron microscopy (Fig. 2), microprobe analysis, and Fourier transformed infrared spectroscopy.

Fig. 1. X-ray diffraction pattern of kenyaite synthesized for 96 h.
Fig. 2. SEM micrograph of kenyaite synthesized for 96 h presenting a rosette-like aggregate over an amorphous substrate. x2200; bar length – 10 im.

The appearance of kenyaite among the run products obtained in this system has been somehow unexpected but can be explained with the high Si/Zr ratio in the initial gel. However, the field of crystallization of this compound is quite narrow: 0.3-1.5 Na2O – 0-0.3 ZrO2 – 10-15 SiO2 – 150-300 H2O, and the phase stability is sensitive to the reaction conditions as indicated by the presence of concomitant amorphous products and/or silica. Within its crystallization field but without using ZrCl4, kenyaite of low crystallinity forms for less than 24 h, then rapidly transforms into quartz, the latter being the only phase detected by X-ray diffraction after 48 h. Following the described in [57] procedure best quality samples of kenyaite have been prepared in the presence of ZrCl4 between 72 h and 96 h, after which a slow transformation into quartz comes. Traces of kenyaite have been observed even after 168 h of synthesis duration. A possible explanation for the increased lifetime of kenyaite in the crystallization sequence of our system is the presence of zirconium. Further investigations are needed to elucidate the effect of Zr in the synthesis of this phase and its structural position since this can be essential for promoting of new properties for this material promising for its application in fields like cation exchanging, adsorption and oxidation catalysis.


22. Thermal and calorimetric investigation of hydrotalcite phases and their transformations (N. Petrova)

The behavior of the evolution of water and CO2 in natural and synthetic hydrotalcites (HT) (a ratio Mg/Al between 2:1 and 3.7:1), heated to 850 oC, was investigated by DTA-TG, EGA (evolved gas analysis) IR, XRPD and SEM [32]. The thermal decomposition of hydrotalcite leads to the formation of a series of metaphases: dehydrated HT-D; partially dehydroxylated HT-B and mixed oxides (MO) [115]. Two (Mg, Al) oxides exist in the temperature range 350- 850 oC: periclase-like (MO-P) and spinel-like (MO-S) mixed oxides [109]. The grain sizes of 3-8 nm for MO-P and of about or less than 1nm for MO-S are estimated from the full width at half maximum (FWHM) of diffraction lines using Sherer's equation. The measured average grain sizes correspond to a surface area of about 200 m2g-1 for the heated samples, a value, which is 10 times higher than that for the initial synthetic samples. The transformation of HT-B into MO is accompanied by releasing H2O and CO2 (almost a half of the initial weight). The MO volume is about 33% that of the initial sample. Taking into consideration that the crystal size preserves (a pseudomorphous replacement), the remaining 67% of the MO volume are pores. The high porosity of MO is demonstrated by small-angle scattering at 2oΘ of XRPD patterns. The relationship between both MO phases as a "decoration" of MO-P by MO-S determines the stability of sintering of this material, namely the latter phase covers the surface of the former, thus detaining the sintering of periclase-like nanoparticles. The high surface area, porosity and stability of sintering of mixed oxides explain their potential as alkaline catalysts.

Hydrotalcite materials are also interesting as ion-exchangers. Although their ion-exchange properties have been widely studied, thermodynamic data based on direct calorimetric measurements are sporadic. A Kalve-type differential calorimeter was used to determine the total heats of anion exchange on a benzoate-intercalated Mg-Al sample (Mg/Al ratio = 3:1 and d003= 16.3 Ε) in solutions of 1.0M KF, KCl, KI, KNO3, Na2SO4 and Na2CO3 [110]. The dependence of the total heats of anion exchange, Q, Jg-1 vs. the basal spacing, Ε of the exchanged forms are given in Fig.1.

The Q values are rather small all they being exothermic and increasing with increasing the basal spacing. The factors determining the heat effect of anion exchange are rather complicated: except energy bonding between layers and interlayer in the structure it is important to consider the hydration heats of anion in the solution.

Fig.1. Plots of heat of anion exchange, Q vs. basal spacing
of exchanged samples.


23. Mass-transport processes in silicate melts under external fields: model investigation of basaltic melts subjected to constant electric potential
(N. Zidarov, I. Mouchovski, M. Tarassov)

In investigating electrochemically induced mass-transport in anhydrous basaltic melts (Ann. Reports 5/1999, 6/2000, 7/2001, 8/2002, and 9/2003) model experiments were accomplished at variable values of the melt temperature and the intensity E of the imposed electrical field to assess the contribution of the possible mass-transport mechanisms included – concentration diffusion, migration, viscous flow, and Stephan flow. One-dimensional model supposing a quasi-equilibrium in the melt was derived in the form of the first Fick's low: Ji = (C.Dieff/δ).Fitr, where Ji is a partial flux of ith melt constituent, Fitr is the so called "transport factor", Dieff is the effective binary diffusion coefficient of ith component, C is the mean total concentration of the melt, and δ is the width of the near-cathodic region wherein the ionic transport is under diffusion control. Fitr essentially replaces the difference in weight fractions (Xio–Xis) in the classic Fick's law. It was shown that the ratio Fitr/(Xio–Xis) determines the overall contribution of migration, viscous flow, and Stefan flow juxtaposed to concentration diffusion. This means that by eliminating consecutively the parameters related to the different mass-transport processes in Fitr, one may model the relevant partial fluxes Ji and may establish the contribution of different transport mechanisms at given experimental conditions. We checked the model by using the data for dependence (time) – (total current density) and analyzing the Fe distribution in the frozen profile in the sample, whose melt was being subjected to electrical field with a "high" E-value of 1.8 V/cm. The results are shown in Tabl. 1.

Table 1. Relative mass-transport contribution in the Fe-ions drive in basaltic melt, subjected to constant DC electric field with “high” intensity at temperature of 1604 K.

Analyzing the data for Fitr/(XFeo–XFes)-values one can see: i) the migration contribution surpasses significantly that of the other mass-transport mechanisms; ii) the viscous flow is a bit over 20% of diffusion contribution, being, at the same time, negligible as compared to migration; iii) Stefan flow arising at electrochemical Fe3+-reduction accelerates the migration approximately by 8%.

Table 2. Parametric model data, mean velocity and traversed distance of Fe and
Mg-ions in anhydrous basaltic melts subjected to constant external electric field.

According to the model it was found (Tabl. 2) that the mean ionic velocity, ui, defined by the ratio of relevant partial molar flux to mean molar concentration, varies for Fe-constituent from 0.92.10–3 to 4.54.10–3 cm/s at E varying from 0.41 to 1.84 V/cm. At a short range was estimated ui for Mg-constituent (2.24.10–3 cm/s at 0.41 V/cm). Because of the significantly faster migration motion for Fe- and Mg-ions compared to their diffusion motion in the studied basaltic melts (subjected to DC electrical field with E ranging from 0.4 to 2 V/cm), these two cations acting as network modifiers enrich the cathodic surrounding. The calculation shows that at such conditions their driving front passes a distance of 1 m for 24-h, thus creating a pronounced heterogeneity in chemical composition of the basaltic melt during the stage of homogeneous differentiation in the "cathodic space" of the margins of any magmatic chamber. This outcome suggests that the ionic migration forced by electrical potential gradients within the margins of the magmatic chambers may play a significant role in geological processes.


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

24. Nanoscale phase transformations in relaxor-ferroelectric lead scandium tantalate and lead scandium niobate (B. Mihailova, L. Konstantinov)

Structural transformations that take place on cooling down in Pb-based relaxor ferroelectrics are investigated on the basis of polarized Raman spectroscopy and far infrared ellipsometry applied on single-crystal samples of PbSc0.5Ta0.5O3 (PST) and PbSc0.5Nb0.5O3 (PSN). The temperature evolution of phonon anomalies reveals different preferred ferroic species in PST and PSN. Near the dielectric constant maximum cooperative shifts of Pb atoms in respect to the oxygen sheets perpendicular to the cubic body diagonal occur in larger spatial regions for PST than for PSN. On cooling down this structural modification becomes preferential for PST, thus giving rise to highly anisotropic ferroelectric domains. In PSN the temperature decrease favours B-cation deviations from the BO6-octahedral centers, which leads to formation of small-sized polar clusters distributed in the isotropic matrix. Near 180 K PST undergoes an additional phase transition that involves reduction of the rotation symmetry. The nanoscale phase transformations in PST are affected by the presence of point defects rather than by the degree of long-range B-site ordering. The spectroscopic data give some evidence that in PSN additional multiplication of the unit cell takes place, besides the common perovskite-structure doubling  [62, 99].


25. Crystal structure of 2-[(2-ethoxy-3,4-dioxocyclobut-1-en-1-yl)amino]
(Ts. Kolev, R. Petrova, M. Spiteller)

The investigation of (L)-2-[(2-ethoxy-3,4-dioxocyclobut-1-en-1-yl) amino] -3-phenylpropaneamide semi-hydrate (I) is part of a project dealing with nonlinear optical, electro-optical and photorefractive materials [19]. Several optically active salts of squaric acid have been synthesized and their crystal structure has been reported: (R)-(-)-1-phenylglycinium hydrogensquarate monohydrate, L-argininium hydrogensquarate, L-serinium hydrogensquarate, L-asparaginium hydrogensquarate. The study was continued with syntheses of squaric acid covalent derivatives. The first reported structure of squaric acid ester-amide is 4-[(4-N, N-diemethylaminophenylene) amino] -3-ethoxy-3-cyclobutene-1,2-dione. It has been synthesized according to the general procedure described by Tietze. We tried to apply this approach to free amino acids. The procedure did not result in desired products due to zwitterionic nature of amino acid.

Fig. 1. Molecular scheme.

The titled compound was synthesized via condensation of L-phenilalaninamide and diethylsquarate in ethanol at room temperature upon continuous stirring.

The organic molecule in (I) is optically active and possesses considerable conformational flexibility (Fig. 1). This is probably the reason that there are two conformationally nonequivalent organic molecules in the unite cell, which differ in their twisting and mutual position of the phenyl and squarate moieties. The torsion angles describing the conformation of molecule (I) are: C5-C6-C7-C8 is 88.4(5)o; C6-C7-C8-N2 is 64.6(5)o and C7-C8-N2-C10 is 105.0(4)o. The values of the corresponding angles in molecule II are 70.0(5)o, 54.1(5)o and 117.8(4)o respectively. The dihedral angle between phenyl and squarate moieties is 42.0(1)o in first (I) and 62.3(2)o in the second (II) molecule. The amide groups form diverse hydrogen bonds. The two types of organic molecules and a water molecule are linked along the a-axis by hydrogen bonds of the type N1-H1B...O9-HW2...O6-C-C-O7...H1A-N1 thus building polymeric zigzag chains. The chains are connected along the c-axis by hydrogen bonds, forming complex rings of the type N3-H3B...O3-C-C-O2...H3A-N3. The shortest hydrogen bond is between HW2 water atom and the amide oxygen from molecule I. The presence of three groups of differing in length hydrogen bonds is well shown by the IR spectrum measured on a KBr pellet. The spectral band at 3184 cm–1 was assigned to the shortest O9-HW1...O1 bond. The broad band between 3340 and 3370 cm–1 can be attributed to the bonds in which the donor-acceptor distance varies in the range of 2.82 - 2.89 A. There is a shoulder at about 3470 cm–1 that corresponds to the longest hydrogen bonds N3-H3A...O2 and N1-H1A...O7. For the first time the transparent crystal described could be a representative of a new series of prospective crystalline materials suitable for second order nonlinear optical applications in conventional diode lasers. In contrast to the known ionic noncentrosymmetric materials this crystal has the technical advantage in its water insolubility, high melting point and high degree of crystallinity.


26. Crystal structure of a-Ethyl-a-N-(hydroxyethylamino)-methylphosphoninic acid (B. Shivachev, R. Petrova, K. Kosev, K. Troev)

Structural characteristics of a-aminophosphonic acids are interesting due to their potential biological activity. Recently we started an investigation of new phosphomycin analogs and their biological activities. One of them is a-Ethyl-a-N-(hydroxyethylamino)-methylphosphoninic acid [69]. The synthesis of the titled compound and its disodium salt has been previously reported.

In the crystal structure of the titled compound the molecule exists as a zwitterion with the amino group being protonated and the phosphonic acid group being ionized (Fig.1). The P-O2 and P-O3 bond distances show similar values, 1.501(2) A and 1.505(2) A, indicating that the negative charge is nearly equally distributed between both of the oxygen atoms. The molecule has an extended structure as seen from torsion angles of the backbone, P-C1-N-C4-C5.

Fig. 1.

The a-ethyl and hydroxy groups emerge from the same side of the backbone. The molecules are facing each other with fragments having an opposite charge and are linked via N-H...O and O-H...O hydrogen bonds to form ribbons running along the b axis. Each two phosphonic groups from neighboring chains are linked via O1-H1...O3 hydrogen bonds to form layers parallel to (100). Thus eight-membered rings of the type, P-O1-H1D...O3'-P'-O1'-H1D'...O3 occur in the layers. Similar rings are formed between phosphonate groups in other aminophosphonic acids.


27. Growth of ternary fluoride compounds Ca1-xMexF2 (Me = Ba; Sr) of optical grade: effect of PbF2 and ZnF2 additives on optical properties (J. Mouchovski)

The ternary crystal compounds CaxMe1-xF2 (Me = Ba; Sr, where 0<x<1) have been recognized as highly potential crystalline materials for manufacturing stepper lenses to produce smaller and faster new-generation integral circuits. These mixed crystals may satisfy the challenging requirements of the contemporary semiconductor industry for optical materials with extremely low birefringence in vacuum ultraviolet (VUV). In this spectral region the starting components, CaF2 and MeF2, show such intrinsic birefringence versus wavelength dependences which allow entirely eliminating the negative effect of intrinsic birefringence. Supposing the optical properties of single and mixed fluoride crystals as depended similarly on the purity of growth atmosphere regarding oxygen contaminants, the key goal of the research is to explore the major source of such contamination in case of CaF2 crystal growth and to find an efficient method to minimize it thus avoiding a deterioration of crystal optical properties. According to our previous investigation (Ann. Rep. 9/2003), the high optical quality of CaF2, grown by Bridgman-Stockbarger method, is determined rather by efficiency of removing the moisture adsorbed deeply in the starting material, than by the apparatus capability to maintain high purity atmosphere in the reactor chamber. It has been proved a good efficiency of the developed method of Preliminary High Temperature - High Vacuum Purification (PHT-HVP), whose usage converts any starting fluorides into high-density precursors with extremely low level of adsorbed oxygen-containing ions (OH– and O2–). The next step is distinguishing precisely the effects of PbF2 and ZnF2 additives, whose reactions with traces of oxygen contaminants inside a multi-crucible, loaded by CaF2 precursors and different amounts of additives, give highly volatile products easily removable under outward partial pressure and total pressure gradients. The run is carried out in argon flow, a gaseous media, suggested to ensure minimal segregation and decomposition of the melt.

The grown crystal ingots appear visibly transparent and colorless that indicates insignificant content of light-scattering centers and a very low abundance of optical-active centers of light-absorption in visible (VIS) spectrum region. The external transmittance of optical windows prepared from the grown ingots is measured at different wavelengths l and the corresponding values for the coefficient of extinction E are calculated. From E - l curves, obtained at different amounts of PbF2 and ZnF2, the individual optimum for both additives is localized. Their efficiency regarding the relevant grades of optical CaF2 is studied by following the wavelength dependence of extinction ratio θ that corresponds to the optimal amounts of used scavengers. This dependence is essentially linear up to 610 nm, the middle VIS (Fig. 1), with a correlation coefficient of 0.98.

Fig. 1. Extinction ratio of optimal ZnF2 scavenger (0.375 wt.%)
to optimal PbF2 scavenger (0.95 wt.%) as a function of wavelength.

Approximating the line in the far UV (λ £ 190 nm), one can find θ value of 0.846 at 157 nm, which is, nowadays, the shortest wavelength for stepper lenses systems. Such steepness of the line indicates that ZnF2 is, likely, better as scavenger than PbF2 at λ < 300 nm, that is, in VUV and shorter UV. At λ>300 nm the value of θ becomes above 1, which means PbF2 to be more efficient scavenger, keeping this effect to middle VIS (610 nm). The comparative analysis of scavenger efficiency for growing different grades optical CaF2 allow us to suggest ZnF2 additive below 1 wt. % as appropriate for growing UV grade mixed fluoride crystals Ca1-xMexF2 (Me = Ba, Sr; 0<x<1). For the ternary compound Ca1-xBaxF2 we do not obtain solid solutions when the growth is performed in static argon media at pressure exceeded the atmospheric surroundings and extremely high purity of entering gas. Instead crystals, we obtain eutectics of the starting single fluorides representing non-transparent ingots with milk-white to gray-opaque color. Nevertheless, a slight partial solubility appears at the lowest x. In the case of the ternary compounds Ca1-xSrxF2 solid solutions are sintered in high vacuum for the first time in Bulgaria. The run conditions ensure a single crystal structure in the upper half part of the grown ingots, which are colorless, visibly transparent, and shaped convex in the top. A break in normal growth (volumetric crystallization) is observed along the finally crystallized part of the ingots, as its contribution to the overall process decreases with increasing CaF2 content in the compound due to lowering the melting point for the relevant x. The outcome of this research is in our ability to grow high-quality mixed fluoride crystals appropriate for usage in 193 nm and, 157 nm versions of UV lithography.

28. Positron lifetime spectroscopy of vitreous diboron trioxide (B. Shivachev,
I. Mincov, E. Kashchieva, Y. Dimitriev, R. Smith, T. Troev)

A comparison is made of the structural data obtained by Positron Lifetime Spectroscopy (PLS) for vitreous B2O3 (v- B2O3) and crystalline B2O3 (c- B2O3). PLS is based on the fact that the lifetime of a positron in its bound form, positronium (Ps), is sensitive to structural inhomogeneities. It is energetically favorable for Ps to locate in regions of low electron density, such as holes, vacancies, and cavities. Existing models describe the relation between the o-Ps lifetime and the size of the free volume by assuming different shapes of the Ps trapping void. Samples of v-B2O3 were dried by holding the melt at 1350 K to reduce the presence residual OH groups [31]. Fast quenching and slow cooling were used to obtain glasses having different fictive structures. According to the literature, B3O6 rings are thought to be formed during slow cooling of v-B2O3. The c-B2O3 modification, was prepared by US Borax Inc. according to the classical scheme. Three lifetimes, t1, t2, and t3, with respective intensities I1, I2, I3, were measured in both vitreous and crystalline samples. According to assumed model the different lifetimes must be associated with different electronic densities e.g. different structures. The observed value of 0.224 ns (t1) in c-B2O3 is probably from positron annihilation in monovacancies. For v-B2O3 samples, the measured value of t1 (0.127-0.162 ns) is the sum of two lifetime components: the p-Ps component (0.124 ns) and a component for positron annihilation in the glass matrix. These "two" components couldn't be separated analytically as the lifetime difference is very small. The lifetime t2 (0.380 – 0.406 ns) is due to annihilation around oxygen, ions and is practically the same in the glassy and crystalline samples. This lifetime component has similar values to the ones reported in several other glasses. From the value of the long lifetime component, t3 (1.53 ns), attributed to the positronium atom, the average size of the cavity radius was estimated to be 2.5 Ε consistent with the dimension of a boroxol ring inner "circle". The significant difference in I3 component observed in v-B2O3 (24 to 31%) and c-B2O3 (4%) is related to the absence of boroxol rings in the structure of c-B2O3. For c-B2O3 t3 should be explained by the presence of either narrow pores or a small amount of amorphous B2O3 phase. PLS results confirm the presence of different structural motifs in c-B2O3 and v-B2O3 modifications. The long lifetime component, t3, is attributed to positron annihilation in cavities with a radius of 2.5 Ε e.g. in boroxol rings.


29. TEM investigation of dense Na8Zr3Si6O22 (U. Kolb, D. Nihtianova,
V. Kostov-Kytin, Yu. Kalvachev)

Na8Zr3Si6O 22 was obtained under static hydrothermal conditions. This new chemical compound is potentially valuable in catalyst systems. The sample was investigated by TEM (EM 420 Philips, Tecnai 12) and powder X-ray diffraction (DRON 3M). The unit cell parameters were determined by a series of tilts in SAED mode and powder X-ray diffraction. The tilt was started from the initial zone [101] showing the b – parameter of 9.26 Ε and a (101) interplaner distance of 5.02 Ε. The tilt around b* indicates a series of crystallographic directions: [101],[102],[001],[10-2],[10-1],[20-1],[30-1],[40-1]. Electron diffraction data from tilt series show unambiguously that the c - parameter is doubled in comparison with the powder data and the possible space groups being Cmc21 and Cmm2. From the tilt about b* only the zone [102] and [10-2] would exhibit a difference. Unfortunately, these zones were too weak to consider the right space group. The c - glide plane and 21 screw axes would be only distinguishable via the tilts about other axes. Both space groups Cmc21 and Cmm2 explain powder diffraction data in the same way. After the refinement of the unit cell parameters with respect to powder data, the cell parameters are: a = 5.539 Ε, b = 8.981 Ε, c = 13.867 Ε, a=b=g=90. Due to the rules of both space groups the chemical formula Na8Zr4Si8O28 turns to be more probable. Using the cell parameters refined from ED data with respect to powder data (Cmc21: a = 5.55 Ε, b = 8.99 Ε, c=13.88 Ε, a=b=g=90), and the determined composition of 8 Na, 4 Zr, 8 Si and 28 O, a reasonable density of 2.93 g/cm3 was derived. Attempts to pack the atoms into a cell with space group symmetry Cmm2 does not lead to any reasonable arrangement. We assume 4Zr as occupying a special position a (0,y,z). To join all oxygens two Si atoms have to be positioned on the mirror plane (= 8 Si) as well. Na atoms are placed on common position (= 8 Na), with three oxygens on the mirror plane (= 12 O) and four oxygens on common positions (= 16 O).


30. Catalytic properties of Au/ETS-4 and Au/ETS-10 (Yu. Kalvachev,
V. Kostov-Kytin, H. Papp)

By using the deposition-precipitation method for loading of gold on titanosilicates ETS-4 and ETS-10 catalysts can be obtained, in which gold particles are homogeneously dispersed on the surface of the supports and are with average diameter of 2 to 4 nm. When gold is deposited as fine nanosized particles over suitable support it has been found that gold exhibits exceptionally high catalytic activity for many reactions. Adsorption of nitrogen oxide over the so synthesized nanosized gold catalysts is investigated by in situ FTIR spectroscopy. Different mononitrosyls and dinitrosyls adsorbed species as well as nitro- and nitro-nitrito complexes are observed. The influence of time and temperature on the stability of these species is studied [14].


31. Structure study of porous silicon by atomic structure modeling and computer simulated HR TEM images (V. Dimov, P. Vitanov)

Porous silicon structure was investigated by Transmission Electron Microscope (TEM) imaging phase and diffraction contrast. Different structure types in the dissolution zones are found: crystalline structure of primary silicon; changed crystalline structure in the intermediate dissolution zone as a result of a partial dissolution process; amorphous structure in the porous zone. A hypothesis about the type of the changed structure in the intermediate dissolution zone is put forward and an atomic model of this structure is presented. The model of the changed silicon structure was checked by studying experimental High Resolution Transmission Electron Microscopy Images (HRTEMI). HRTEM images analysis is complicated and not always unambiguous. A correct interpretation is possible only when the experimental images are compared with those theoretically calculated on the basis of the atomic models proposed [82].

Images of phase and diffraction contrast have been simulated on the basis of models accounting for structure changes. Fig.1 shows simulated and experimental HRTEM images. Three dissolution zones are observed similar to those in the experimental HRTEMI. Changes in the phase and diffraction contrast when passing from one zone to another are seen. The effect arises from thickness or structure changes. A new structure polygon that appears in the boundary zone evidences for structure changes or for electrons interaction with more than one type of crystalline structure (superstructure effect). The structure, diffraction and phase contrast changes correspond to the changes in the experimental HRTEMI. A good agreement between experimental and simulated images is observed.

Fig.1. Simulated and experimental HRTEM images. A good agreement between experimental and simulated images is observed. a –The simulated image is calculated on the basis of a two-layered super cell. Diffraction and phase contrast changes are the same as those of experimental images. b - Suitable magnification experimental HRTEMI containing a super-cell.

A theory of the mechanism of the dissolution process, based on structural peculiarities, observed in the images, was formulated. The dissolution occurs mainly in the most favourable atomic planes (101) and (111). The process proceeds simultaneously on the whole etching surface with relatively equal velocity along [010] direction. As a result, a zigzag dissolution front is formed, parallel to the etching surface, which divides the porous and the unchanged zones and comprises regions of primary and partially dissolved silicon.


V. Ph.D. THESESES

32. Structural characteristic of compounds in the system M2+(ReO4)2LH2 O, M= Ca, Sr, Ba, Pb, Cd; L = CO(NH2)2, CS(NH2)2 (R. Petrova)

The present investigation aims at modeling the structures of compounds in the system M2+(ReO4)2–H2 O (M=Ca, Cd, Sr, Ba, Pb) through adding small organic molecules with analogous donor-acceptor centers differing in their molecular geometry and manner of package [28]. Two different molecules with well studied crystal and chemical properties and relatively high dipole moment, urea and thiourea are used. All starting compounds are well solvable in water, due to which the synthesis is performed following the standard procedure, namely mixing water solutions of inorganic and organic compounds in different molar ratios and evaporating at different temperatures. The investigations of the dry substances are performed using powder and single crystal diffraction methods. The DRON – 3M and DRON - UM1 powder diffractometer and CAD4 single crystal diffractometer are used. The main achievements of the dissertation are: 1. The crystal structures of the following compounds are determined and analyzed: Cd(ReO4)2.2Urea, Cd(ReO4)2.4Urea, Cd(ReO4)2.6Urea, Pb(ReO4)2.3Urea, Cd(ReO4)2.2Thiourea(I), Cd(ReO4)2.4Thiourea, Cd(ReO4)2.2Thiourea(II), Ca(ReO4)2.Urea.H2O, Ca(ReO4)2.5Urea, Pb(ReO4)2.Urea.H2O, Sr(ReO4)2.Urea.H2O, Ba(ReO4)2.3Urea, Sr(ReO4)2.3Urea, Pb(ReO4)2.6Thiourea.H2 O and Cd(ReO4)2.6Thiorea. On the bases of date obtained detailed diffraction patterns for the first six ones are prepared and included in the Powder Diffraction File (PDF). 2. It is found that the crystal structures of Sr(ReO4)2.Urea.H2O and Pb(ReO4)2.Urea.H2O, Ba(ReO4)2.3Urea, Sr(ReO4)2.3Urea and Pb(ReO4)2.3Urea are iso-structural.

Fig. 1. Schematic presentation of the studied compounds.

3. The general relationships for building the crystal structures of adducts know so far and newly synthesized were discussed and a general method for presenting the studied compounds is proposed (Fig.1).

4. The role of hydrogen bonds in 3D arrangement of the structural units is determined and it is found that these bonds contribute to the structure stabilization.


33. Synthesis and crystallochemical characterization of microporous titanosilicates (S. Ferdov)

The aims of the doctoral thesis are to modulate the conditions of hydrothermal synthesis of microporous titanosilicates in the systems Na2O – TiO2 – SiO2 – H2O, K2O – TiO2 – SiO2 – H2O, and Na2O - K2O - TiO2 - SiO2 - H2O; to investigate the physicochemical conditions affecting the process of crystallization; study the thermal behaviour of the microporous titanosilicates [8]. A complex of analytical methods and procedures was used: optical microscopy, SEM, powder X-ray diffraction, thermal treatment. At times between 24 and 96 h, temperature 200 °C and using one and the same chemical reagents, varying the chemical composition of the initial gel one may synthesize ten titanosilicate phases - six microporous [ETS-4, ETS-10, STS (AM-2), titanosilicate analogue of the mineral sitinakite, a cubic titanosilicate analogue of the mineral pharmacosiderite (GTS-1) and a rombohedral titanosilicate analogue of the mineral pharmacosiderite], two layered phases [JDF-L1 (AM-1) and AM-4], containing water molecules and two dense titanosilicates (natisite and paranatisite). For the majority of these phases the crystallization fields are determined by varying the quantities of Na2O, Na2O/K2O, K2O and TiO2. The main morphological difference between the synthesized phases is in their existing as polycrystalline particles or single crystals. In synthesizing ETS-10 and JDF-L1 the variations in the initial batch composition do not affect significantly the morphology and these two phases appear only as single crystals or their aggregates. In the crystallization field of STS the increase of the initial content of alkalis results in the formation of pseudohexagonal single crystals not observed for the other phases. The thermal behaviour of as-synthesized titanosilicates shows that upon heating the microporous phases undergo a gradual decrease in crystallinity accompanied by amorphization and followed by transformation into a dense titanosilicate or into unknown phase/s (Fig. 1).

Fig. 1. Powder XRD patterns showing an example
of the thermal stability of ETS-4 during heating
up to 800oC

The most important results of this work could be brought out as follow: 1) It is shown that the synthesis of microporous titanosilicates can be performed rapidly, without using any organic compounds. 2) The phases with the highest contents of silicon in their structures (ETS-10 and JDF-L1) appear mainly as single crystals. 3) The ratio TiO2/Na2O and/or K2O in the initial gel can be used for controlling phase structure and morphology. 4) The observed phase transformations from one to another phase demonstrated for the first time Ostwald's rule for titanosilicate phases. 5) By refinement of the unit cell parameters, precise Powder Diffraction Files for JDF-L1, Na-GTS-1, natisite and paranatisite were prepared. 6) A new method for rapid and relatively low-temperature preparation of Na-GTS-1 is performed. 7) A new rapid method for synthesis of JDF-L1 is described. 8) For the first time a rombohedrally distorted titanosilicate analogue of mineral pharmacosiderite is synthesized from an initial sodium-potassium batch (molar composition 5Na2O – 3.7K2O – 0.76TiO2 – 4.3SiO2 – 714H2O) at 200 °C for 24 h.

INTERINSTITUTE PROGRAMS


POSTDOCTORAL FELLOWS AND VISITING SCIENTISTS


LECTURING ON INTERNATIONAL EVENTS

Dr. B. Mihailova:

Dr D. Nihtianova:


RESEARCH TOPICS, ANNOUNCED FOR INTERNATIONAL PARTNERSHIP COLLABORATION


PUBLICATIONS AND REPORTS AT CONFERENCES AND LOCAL MEETINGS


PUBLISHED ARTICLES AND REPORTS

1. Atanasova-Vladimirova, S., B. Mavrudchiev, A. v. Quadt, I. Peytcheva, S.Georgiev. 2004. Petrology and geochemistry of lamprophyric dykes in the Vitosha pluton. - In: Proc. Conf., BGD,"Geology 2004", December 16-17, Sofia, 100-102.

2. Atanassova, R., T. Kerestedjian, I. Donchev. 2004. Mineralogy and Remobilization Processes in the Weltz-clinker Dump Site, Plovdiv Region, Bulgaria. - In: Proc. of the 8th International Congress on Applied Mineralogy (ICAM), Aguas de Lindoia, Brasil, September 19-22, Eds Pecchio et al. ISBN 85-98656-01-1, 387-389.

3. Banjesevic, M., V. Cvetkovic, A. v. Quadt, I. Peytcheva. 2004. Late Cretaceous evolution of the Timok Magmatic Complex (TMC) inferred from new data on age and geochemistry of volcanic rocks. - In: Proc. 5th Intern. Symp. on Eastern Mediterranean Geol., v. 3, April 14-20, Thessaloniki, Greece, 1080-1083.

4. Banushev, B., Z. Tsintsov, M. Sivilov. 2004. Serpentinised ultrabasites near Tserovo village, Pazardzhik district and related ore mineralization. - Annual of the MGU "St. I. Rilski", 47, 1, 21-26. (in Bulgarian with English abstract)

5. Damianova, A., O. Baicheva, I. Sivriev, D. Salkova, N. Lihareva. 2004. Influence of vanadium input on the chemical content of T.Tim plants. - Mat. 22 Workshop 2004 "Macro- and Trace elements", Jena, Germany, 1164-1171.

6. Dimov, V. 2004. Non-conventional diagnodtics of microcrystalline mineral phdses by TEM. - In: Proc. Conf., BGD,"Geology 2004", December 16-17, Sofia, 12-14.

7. Ferdov, S., C. Lengauer, V. Kostov-Kytin, O. Petrov.2004. A rapid method for low-temperature synthesis of the Na analogue of the microporous titanosilicate GTS-1. - Journal of Materials Science, 39, 4343-4344.

8. Ferdov, S. 2004. Synthesis and crystallochemical characterization of microporous titanosilicates. - (PhD thesis) (in Bulgarian).

9. Ganev, V., M. Tarassov, L. Konstantinov, O. Petrov. 2004. 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, 21-23.

10. Geisler, T., A. M. Sedoux-Guillaume, M. Wiedenbeck, R. Wirth, J. Berndt, M. Zhang, B. Mihailova, E.K.H. Salje, A. Putnis, J. Schlόter. 2004. Periodic precipitation pattern formation in hydrothermally treated, metamict zircon. - American Mineralogist, 89, 1341-1347.

11. Georgiev, V., O. Vitov. 2004. Momchilgrad Depression (dividing on heavy minerals concentrates data). - Mining and geology, 5, 37-42. (in Bulgarian with English abstract)

12. Georgiev, V., O. Vitov. 2004. Momchilgrad Depression (prospect for mineral deposits based on heavy minerals concentrates data). - Mining and geology, 9, 35-38. (in Bulgarian with English abstract)

13. Georgieva, S., R. Petrunov, R. Moritz, S. Stoykov, I. Peytcheva, A. v. Quadt. 2004. Temporal relationship betweenvolcanism and the hydrothermal system in the region of Chelopech high-sulphidation Cu-Au deposit: constraints from geochronological and mineralogical data. - In: Proc. Conf., BGD,"Geology 2004", December 16-17, Sofia, 21-23.

14. Kalvachev, Y., V. Kostov-Kytin, H. Papp. 2004. IR investigation of NO adsorption over nanosized gold deposited on titanosilicates ETS-4 and ETS-10. - Nanoscience & Nanotechnology, Heron Press, Sofia, 4, 168-171.

15. Kamenov, B., A. v. Quadt, I. Peytcheva. 2004. Petrological, geochemical and isotopic constraints for magma origin and evolution of the Capitan-Dimitrievo pluton, Central Srednogorie, Bulgaria. - Geochem, mineral., petrol., 41, 21-53.

16. Kamenov, B., Y. Yanev, R. Nedialkov, R. Moritz, I. Peytcheva, A. v. Quadt, S. Stoykov, A. Zartova. 2004. An across-arc petrological transect through the Central Srednogorie Late-Cretaceous magmatic centers in Bulgaria. - In: Proc. Conf., BGD,"Geology 2004", December 16-17, Sofia, 35-37.

17. Karashanova, D., D. Nihtianova, K. Starbova, N. Starbov. 2004. Crystalline structure and phase composition of epitaxially grown Ag2S thin films. - Solid State Ionics, 171, 269-275.

18. Kecht, J., B. Mihailova, K. Karaghiosoff, S. Mintova, T. Bein. 2004. Nanosized gismondine grown in colloidal precursor solutions. – Langmuir, 20, 5271-5276.

19. Kolev, T., R. Petrova, M. Spiteller. 2004. (R)-2-[(2-Ethoxy-3,4-dioxocyclobut-1-en-1-yl)-amino]-3-phenylpropanamide hemihydrate. - Acta Crystallographica, E60, 634-636.

20. Kostov-Kytin, V., B. Mihailova, S. Ferdov, O. Petrov. 2004. Temperature-induced phase transformations of layered titanosilicate JDF-L1. - Solid State Sciences, 6, 967-972.

21. Lazaro M. J., M. Galvez, I. Suelves, R. Moliner, S. Vassilev, C. Braekman-Danheux. 2004. Low cost catalytic sorbents for NOx reduction. 3. NOx reduction tests using NH3 as reducing agent. - Fuel, 83 (7-8): 875-884.

22. Lihareva, N. 2003. Study of metals fractionation in ash samples using a sequential extraction procedure. - Bulg. Chem. Comm., vol. 35, No 2, 110-114.

23. Mintova, S. M. Hφlzl, V. Valtchev, B. Mihailova, Y. Bouizi, T. Bein. 2004. Closely Packed Zeolite Nanocrystals Obtained via Transformation of Porous Amorphous Silica. - Materials Chemistry, 16, 5452-5459.

24. Mintova, S., V. De Waele, M. Hφlzl, B. Mihailova, U. Schmidhammer, E. Riedle, T. Bein, 2004. Encapsulation of 2-(2'hydroxyphenyl)benzothiazole in Nanosized Zeolites: Intrazeolite Femtochemistry. - Journal of Physical Chemistry, A, 108, 10640-10648.

25. Penev V., N. Zidarov, B. Zidarova. 2004. Geometrization of the Language of Mineralogy: II. Formulation and Logical Analysis of the Structural Paradigms that Underlie the Language Mineralogy. – Compt. rend. Acad. bulg. Sci., 57, 7, 59-64.

26. Penev V., N. Zidarov, B. Zidarova. 2004. Geometrization of the Language of Mineralogy: III. Entirely Mathematical Coordinate Representation of Mineral Structures. - Compt. rend. Acad. bulg. Sci., 57, 7, 65-70.

Penev, V., L. Konstantinov. 2004. Geometrization of the language of chemistry: Mathematical representation of the complex chemical objects . – Academic Open Internet Journal, vol. 11 (2004), Part 2: Chemistry – http://www.acadjournal.com/2004/v11/part2/p3/

Penev, V., L. Konstantinov. 2004. Mathematical representations of chemical processes: Part I. Conceptual schemes for representing changes; space and coordinate system; method. – Academic Open Internet Journal, vol. 11 (2004), Part 2: Chemistry – http://www.acadjournal.com/2004/v11/part2/p4/

Penev, V., L. Konstantinov. 2004. Mathematical representation of chemical processes: Part II. Representation of the free physical particles and of the laws for preservation of the electric charge and the mass in chemical reactions. – Academic Open Internet Journal, vol. 11 (2004), Part 2: Chemistry – http://www.acadjournal.com/2004/v11/part2/p5/

Penev, V., L. Konstantinov. 2004. Geometrical images of the simple and complex chemical objects in the space of chemical structures V M (3). Investigation of the connections between the languages of chemistry and geometry. – Academic Open Internet Journal, vol. 11 (2004), Part 2: Chemistry – http://www.acadjournal.com/2004/v11/part2/p6/

27. Petkova, V., 2004. Investigation of the thermal decomposition of triboactivated samples of ammonium sulphate. - International Journal of the Balkan Tribological Association, v. 10, No 3, 344-353.

28. Petrova, R. 2004. Structural characteristic of compounds in the system M(ReO4)2-L-H2O, M=Ca,Sr,Ba,Pb,Cd; L=CO(NH2)2, CS(NH2)2. - (PhD thesis) (in Bulgarian)

29. Peytcheva, I, A. v. Quadt. 2004. The Palaeozoic protoliths of Central Srednogorie, Bulgaria: records in zircons from basement rocks and Cretaceous magmatites. - In: Proc.5th Intern. Symp. on Eastern Mediterranean Geol., v.3, April 14-20, Thessaloniki, Greece, 392-395.

30. Peytcheva, I, A. v. Quadt, M. Frank, R.Nedialkov, B. Kamenov, C.Heinrich. 2004. Timing and magma evolution of upper cretaceous rocks in Medet Cu-porphyry deposit: isotopegeochronological and geochemical constraints. - In: Proc. Conf., BGD,"Geology 2004", December 16-17, Sofia, 57-59.

31. Shivachev, B. L., I. P. Mincov, E.P. Kashchieva, Y.B. Dimitriev, R. Smith, T. Troev. 2004. Positron lifetime spectroscopy of vitreous B2O3. - J. of Non-Crystalline Solids, v. 345-346, 108-111.

32. Stanimirova, Ts., N. Piperov, N. Petrova, G. Kirov. 2004. Thermal Evolution of Mg-Al-CO3 hydrotalcites. - Clay Minerals, 39, 177-191.

33. Stavrakeva, D., I. Donchev. 2004. Applied mineralogy in Bulgaria. State and perspectives. - Mining and geology, 4, 41 - 45. (in Bulgarian).

34. Stoykov, S., I. Peytcheva, A. v. Quadt, R. Moritz, M. Frank, D. Fontignie. 2004. Isotope constraints on the age and magma evolution of Chelopech volcanic complex (Bulgaria). - In: Proc. Conf., BGD,"Geology 2004", December 16-17, Sofia, 80-82.

35. Tarassov, M., E Tarassova. 2004. Th-U-Pb electron microprobe age dating of monazite from Igralishte and Klissura granites; preliminary data. - In: Proc. Conf., BGD,"Geology 2004", December 16-17, Sofia, 86-88.

36. Tarassov, M., E Tarassova, L. Konstantinov. 2004. Sol-gel preparation, modification and characterization of amorphous and crystalline WO3.xFe2O.nH2O phases. - Nanoscience &Nanotechnology, Heron Press, Sofia, 4, 92-94.

37. Tarassova E., M. Tarassov, Ek. Dimitrova. 2004. Reef limestones from East Rhodope. - Mining and geology, 10, 40-43. (in Bulgarian with English abstract)

38. Tarassova E., M. Tarassov. 2004. Acessory allanite-(Ce) from the Skrut porphyritic granitoids, Serbo-Macedonian massif. - Geology and mineral resources, 3, 14-16. (in Bulgarian with English abstract)

39. Tarassova, E., M. Tarassov. 2004. Accessory allanite and its petrogenetic signoficance for granotoids from Belassitsa Mauntain, Serbo-Macedinuan Massif. - In: Proc.5th Intern. Symp. on Eastern Mediterranean Geol., v.3, April 14-20, Thessaloniki, Greece, 1248-1251.

40. Troev, T., B. Shivachev, T. Yoshiie, 2004, Positron lifetime calculations of defects in nickel containing hydrogen at various temperatures. - Materials Science Forum, V 445/446) 198-200.

41. Tsintsov, Z. 2004. Sperrylite from Vurbitsa River alluvial placers, SE Rhodopes. - In: Proc. Conf., BGD, "Geology 2004", December 16-17, Sofia, In: Conf., BGD, "Geology 2004", December 16-17, Sofia, 92-94.

42. Vassilev, S., R. Menendez, A. Borrego M. Diaz-Somoano, M. R. Martinez-Tarazona. 2004. 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, 83 (11-12): 1563-1583.

43. Vassilev, S., R. Menendez, M. Diaz-Somoano, M. R. Martinez-Tarazona. 2004. 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 (4-5): 585-603.

44. Vassileva, C. 2004. Some environmental aspects related to water-soluble fractions in Bulgarian coals and fly ashes. - Compt. rend. Acad. bulg. Sci., 57, 7, 71-76.

45. Vassileva, C., S. Vassilev. 2004. Some environmental aspects related to sulphur emissions during combustion of Bulgarian coals. - Compt. rend. Acad. bulg. Sci., 57, 9, 29-32.

46. Vitov. O., I. Marinova. 2004. Sensitivity assessment of different grids for soil geochemical surveys using Monte-Carlo simulations. - Compt. rend. Acad. bulg. Sci., 57, 6, 89-94.

47. Vitov, O., V. Georgiev. 2004. Comparison between the Eastern Rhodopes blocks by heavy minerals concentrates data. - In: Proc. Conf., BGD,"Geology 2004", December 16-17, Sofia, 97-99.

48. Zidarov, N., I. Peytcheva, A. v. Quadt, E. Tarassova, V. Andreichev. 2004. Timing and magma sources of Igralishte pluton (SW Bulgaria): Preliminary isotope-geochronological and geochemical data. – In: Proc. Conf., BGD, "Geology 2004", December 16-17, Sofia, 116-117.


PUBLICATIONS IN PRESS

49. Dimov V., N. Khaltakova. Determination of structural parameters of minerals and synthetic phases in tem using saed images obtained from rotation of single crystals around a crystallographic axis. - Ann. of the Sofia Univ. "St. Kl. Ohridski", Department Geology and Geography, book 1 – geology, 97

50. Donchev, I., N. Lihareva, Y. Tzvetanova. A new deposit of celestine in the Lower Cretaceous sediments near Krousheto village, Gorna Oryahovitza municipality. - Ann. of the Sofia Univ. "St. Kl. Ohridski", Department Geology and Geography, book 1 – geology, 97.

51. Doshkova, D., D. Kaisheva, B. Mihailova, M. Gospodinov. Crystal growth, structure and dielectrical properties of ferroelectric mixed Pb2ScTaxNb1-xO 6 single crystals. - Journal of Optoelectronics and Advanced Materials.

52. Ferdov, S., U. Kolitsch, O. Petrov, V. Kostov-Kytin, C. Lengauer, E. Tillmans. Synthesis and crystal structure of a new microporous zirconosilicate, MCV-2. - Microporous Mesoporous Materials.

53. Kaisheva, D., D. Doshkova, B. Mihailova, M. Gospodinov. Dielectric behavior of Sn doped and annealed ferroelectric lead scandium tantalate single crystals. - Journal of Optoelectronics and Advanced Materials.

54. Kamenov, B., Y. Yanev, R. Nedialkov, R. Moritz, I. Peytcheva, A. v. Quadt, S. Stoykov, A. Zartova. Petrology of Late-Cretaceous island-arc ore-magmatic centers from Central Srednogorie, Bulgaria: magma evolution and paths. - Int. Earth Sci.

55. Karayigit, A., Y. Bulut, X. Querol, A. Alastuey, S. Vassilev. Variations in fly ash compositions from the Soma power plant, Turkey. – Energy Sources.

56. Karayigit, A. I., G. Karayigit, Y. Bulut, A. Alastuey, X. Querol, S. Vassilev, C. Vassileva. Mass balance of major and trace elements in coal-fired Soma power plant, Turkey. - Energy Sources.

57. Kavrakova, I., P. S. Denkova, R. Petrova. Stereoselective Lewis Acid Promoted Kharasch-Type Additions of 3-Bromoacetyl-2-oxazolidinones to Norbornadien. Tetrahedron:Asymmetry.

58. Kostov-Kytin, V., Yu. Kalvachev. Synthesis of kenyaite in Zr-containing reaction medium. - Compt. rend. Acad. bulg. Sci.,

59. Majano, G., S. Mintova, O. Ovsitser, B. Mihailova, T. Bein. Zeolite Beta nanosized assembles. - Micropor. Mesopor. Mater.

60. Mihailova, B., M. Gospodinov, B. Gόttler, F. Yen, A.P. Litvinchuk, M. N. Iliev. Temperature-dependent polarized Raman spectra of HoMn2O5. - Phys.Rev.B.,

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

62. Mihailova, B., U. Bismayer, B. Gόttler, M. Gospodinov, A. Boris, C. Bernhard, M. Aroyo. Nanoscale phase transformations in relaxor-ferroelectric lead scandium tantalite and lead scandium niobate. - Zeitschrift fόr Kristallographie,

63. Nihtianova, D., J. Li, U. Kolb. Electron crystallography in mineralogy and materials science, Electron Crystallography, Novel Approaches for Structure Determination of Nanosized Materials. - The 36th Crystallographic Course at the Ettore Majorana Centre, June 9 – 20, Erice, Sicily.

64. Penev, V., N. Zidarov, B. Zidarova. Logical analysis and mathematical formalization of the foundations of the language of mineralogy – a premise for its geometrization. - Ann. of the Sofia Univ. "St. Kl. Ohridski", Department Geology and Geography, book 1 – geology, 97 (in Bulgarian with English abstract)

65. Petkova, V., B. Kunev, D. Paneva, I. Mitov. Application of tribochemistry in utilisation of pyrite concentrates. - Chemistry for sustainable development,

66. Petkova, V., V. Yaneva, I. Dombalov. Structural transformations of Syrian phosphorite under mechanochemical activation. - Chemistry for sustainable development,

67. Petkova, V., Y. Pelovski, V., Hristova. Thermal analysis for identification of E-beam nanosized ammonium sulfate. - Journal of Thermal Analysis and Calorimetry,

68. Quadt, A. v., R. Moritz, I. Peytcheva, C. A. Heinrich. Geochronology and geodynamics of calc-alkaline magmatism and Cu-Au mineralization: the Panagyurishte region of the Apuseni-Banat-Timok-Srednogorie belt (Bulgaria). – Ore Geology Review, spec. edition.

69. Shivachev, B., R. Petrova, K. Kossev, K. Troev. [1-(Hydroxyethylammonio) propyl]phosphonate. - Acta Cryst., E61, 134–136.

70. Stoykov, S., I. Peytcheva, A. v. Quadt, R. Moritz, M. Frank, D. Fontignie. Timing and magma evolution of the Chelopech volcanic complex (Bulgaria). - SMPM (GEODE ABCD ISSUE).

71. Titorenkova, R. Heterogeneity of zircon from high-grade metamorphic rocks, Ograzhden and Maleshevska Mountains, Serbo-Macedonian massif. - Ann. of the Sofia Univ. "St. Kl. Ohridski", Department Geology and Geography, book 1 – geology, 97

72. Vassilev, S., C. Vassileva, A. Karayigit, Y. Bulut, A. Alastuey, X. Querol. Phase-mineral and chemical composition of composite samples from feed coals, bottom ashes and fly ashes at the Soma power station, Turkey. - International Journal of Coal Geology.

73. Vassilev, S., C. Vassileva, A. Karayigit, Y. Bulut, A. Alastuey, X. Querol. Phase-mineral and chemical composition of fractions separated from composite fly ashes at the Soma power station, Turkey. - International Journal of Coal Geology.

74. Vassilev, S., R. Menendez. Phase-mineral and chemical composition of coal fly ashes as a basis for their multicomponent utilization. 4. Characterization of heavy concentrates and improved fly ash residues. - Fuel.

75. Vitov, O., V. Georgiev. Characteristics of the gold distribution in stream sediment pan concentrated surveys from Eastern Rhodopes, SE Bulgaria. – Ann. of the Sofia Univ. "St. Kl. Ohridski", Department Geology and Geography, book 1 – geology, 97 (in Bulgarian with English abstract)

76. Yaneva, V., V. Petkova, I. Dombalov. Effect of tribochemical activation on solid state synthesis in the system Syrian phosphorite – ammonium sulphate. - Soil science,

77. Yaneva, V., V. Petkova, I. Dombalov. Structural modifications and phase transitions under tribochemical activation of Syrian phosphorite. - Soil science,

78. Zidarov, N., V. Andreichev, E. Tarassova, R. Titorenkova. Skrut granodiorite-manifestation of Jurassic magmatisme in Belassiza Mt, SW Bulgaria. – Geologica Balcanica,

79. Zidarova, B., N. Zidarov. Main elements of the common geogenetic model for deposits of the fluorite ore formation in Bulgaria. - Rev. Bulg. Geol. Soc., 65, 1-3, (in Bulgarian with English abstract)


ABSTRACTS AND POSTERS AT SCIENTIFIC EVENTS:

80. Banushev, B., Z. Tsintsov, M. Sivilov. 2004. Serpentinised ultrabasites near Tserovo village, Pazardzhik district and related ore mineralization. - International Scientific Conference of the MGU "St. I. Rilski", October 19-21, Sofia.

81. Cherkezova-Zheleva, Z., M. Shopska, G.Gouliev, I. Donchev, G. Kadinov, I. Mitov, L. Petrov. 2004. Study of the surface of titania-supported nanosized Fe and FeMe (Me=Pd, Pt) systems. - 6th Annual National Workshop "NANO 2004", November 24-25, Sofia, Bulgaria, p. 99.

82. Dimov V., P. Vitanov, Structure study of porous silicon by atomic structure modeling and computer simulated HR TEM images. - 6th Annual National Workshop "NANO 2004", November 24-25, Sofia, Bulgaria, p. 57.

83. Dimova, M., V. Dekov, G. Molin, C. Griggio, I. Rajta, I. Uzonyi. 2004. Cosmic spherules from the metalliferous sediments of two spreading centers:EPR and MAR. - 32th IGC, August 20-28, Florence, Italy.

84. Donchev, I., N. Lihareva, Y. Tzvetanova. 2004. Once more about celestine in sediments from Northern Bulgaria – a new deposit of celestine. - In: Proc. Ann. Sci. "Minerogenesis 2004", BMG, January 22-23, 31.

85. Doshkova, D., D. Kaisheva, B. Mihailova, M. Gospodinov. 2004. Crystal growth, structure and dielectrical properties of ferroelectric mixed Pb2ScTaxNb1-xO 6 single crystals. - 13th International School of Condensed Matter Physic, Advances in the Physics and Technology of Solids and Soft Condensed Matter, Varna, Bulgaria, August 30 - September 3.

86. Ferdov, S., B. Mihailova, V. Kostov-Kytin, Yu. Kalvachev, O. Petrov. 2004. Hydrothermal synthesis and characterization of a novel zirconosilicate. - 22nd European Crystallographic Meeting, August 26-31, Budapest, Hungary.

87. Ferdov, S., V. Kostov-Kytin, O. Petrov. 2004. Microporous titanosilicates – Synthesis and crystallization fields. - Meeting "Micro- and Mesoporous Mineral Phases", December 6–7 Rome, Italy.

88. Ferdov, S., V. Kostov-Kytin, O. Petrov. 2004. Synthesis and characterization of nanosized Na-GTS-1. - 6th Annual National Workshop "NANO 2004", November 24-25, Sofia, Bulgaria, p. 105.

89. Kaisheva, D., D. Doshkova, B. Mihailova, M. Gospodinov. 2004.Dielectric behavior of Sn doped and annealed ferroelectric lead scandium tantalate single crystals. - 13th International School of Condensed Matter Physic, Advances in the Physics and Technology of Solids and Soft Condensed Matter, August 30 - September 3, Varna, Bulgaria.

90. Kashchieva, E. P., Y. B. Dimitriev, B. L. Shivachev. 2004. Middle range order in vitreous boron oxide. - Advances in the Physics and Technology of Solids and Soft Condensed Matter, August 30 - September 3, Varna, Bulgaria.

91. Kostov-Kytin, V., B. Mihailova, S. Ferdov, O. Petrov. 2004. Temperature-induced phase transformations of layered titanosilicate - JDF-L1. - 5th European Conference on Mineralogy and Spectroscopy (ECMS), September 4-8. Vienna, Austria.

92. Kostov-Kytin, V., Yu. Kalvachev. 2004. Hydrothermal Synthesis and Characterization of Novel Sodium Zirconosilicates. - Meeting "Micro- and mesoporous mineral phases", December 6-7, Rome, Italy.

93. Kunev, B., D. Paneva, D. Mitova, V. Petkova, E. Manova, I. Mitov. 2004. Tribochemical and thermotribochemical treatment of pyrite concentrates. – Anniversary National conference with foreign participation BULTRIB'04 „30 years tribology in Bulgaria", October 28-29, Sofia.

94. Kunev, B., V. Petkova, D. Paneva, D. Mitova, E. Manova, I. Mitov. 2004. Mechanochemical and thermomechanochemical treatment of pyrite concentrates – particle size effects. – 6th Annual National Workshop "NANO 2004", November 24-25, Sofia, Bulgaria, p. 104.

95. Kunev, B., V. Petkova, D. Paneva, E. Manova, I. Mitov. 2004. Tribochemical and thermo-tribochemical treatment of pyrite concentrates - 5th National chemical conference - 29 September – 1 October, Sofia.

96. Lihareva, N., O. Petrov, Y. Tzvetanova. 2004. Application of the BCR extraction procedure for study of metal distributions in waste water slurries and sediments. - In: Proc. 5th National conference of chemistry, September 29 – October 01, Sofia.

97. Mihailova, B. 2004. Stacking disorder in zeolite Beta family, Workshop of CNRS-DFG bilateral program. – June 31 –July 02, Munich, Germany.

98. Mihailova, B. Raman spectroscopy as a method for structural analysis on nanometric scale. - Department of Physical Chemistry, Ludwig-Maximillian University of Munich, Germany, July 21.

99. Mihailova, B., M. Gospodinov, B. Guettler, U. Bismayer, L. Konstantinov. 2004. Nanoscale phase transformations in relaxor-ferroelectric lead scandium tantalate and lead scandium niobate. - 6th Annual National Workshop "NANO 2004", November 24-25, Sofia, Bulgaria, p. 24.

100. Mihailova, B., M. Wagner, S. Mintova, T. Bein. 2004. Colloidal molecular sieves: model system for kinetic study of crystal growth process. - 14th International Zeolite Conference, April 25-30, Cape Town, South Africa,

101. Moritz, R., K. Kouzmanov, I. Chambefort, A. v. Quadt, R. Petrunov, I. Peytcheva. 2004. Epitermal Cu-Au deposits of the Late Cretaceous Panagyurishte ore district, Srednogorie zone, Bulgaria: similarities and variations in ore characteristics. – In: Proc. Japan-Swiss Seminar "Spatial and temporal relationships between deep magmatic, porphyry and epithermal environments and significance for ore formation processes", March 4-14, Tsukuba and Kagoshima, Japan.

102. Nihtianova, D., L. Macheva, U. Kolb. 2004. TEM study of structural transformations in potassium feldspars from Biala reka metagranitoids, Eastern Rhodopes, Bulgaria. - In: Proc. Ann. Sci. "Minerogenesis 2004", BMG, January 22-23, 48-49.

103. Nihtianova, D., U. Kolb, Jixue Li, I. Queralt. 2004. "TEM Investigation of Aerinite, Compared with Synchrotron and X-ray Powder Diffraction Data", s4.m14.04. - 22nd European Crystallographic Meeting, August 26 – 31, Budapest, Hungary.

104. Penev, V., N. Zidarov, B. Zidarova. 2004. Geometrization of the language of mineralogy – upcoming new stage in its evolution - In: Proc. Ann. Sci. "Minerogenesis 2004", BMG, January 22-23, 50-51.

105. Petkova, V., B. Kunev, D. Paneva, I. Mitov. 2004. Application of tribochemistry in utilising pyrite concentrates. - VIII International Conference on Sintering and II International Conference on Fundamental Bases of Mechanochemical Technologies "Mechanochemical Synthesis and Sintering", June 14 - 18, Novosibirsk, Russia.

106. Petkova, V., V. Yaneva, I. Dombalov. 2004. Structural transformations of Syrian phosphorite under mechanochemical activation. - VIII International Conference on Sintering and II International Conference on Fundamental Bases of Mechanochemical Technologies "Mechanochemical Synthesis and Sintering", June 14 - 18, Novosibirsk, Russia.

107. Petkova, V., Y. Pelovski, I. Dombalov, K. Tonsuaadu. 2004. Thermochemical investigations of natural phosphate with ammonium sulphate additive. – 13th ICTAC Congress, September 12-19, Chia Laguna, Sardinia, Italy.

108. Petkova, V., Y. Pelovski, P. Kostadinova, I. Dombalov. 2004. Influence of triboactivation conditions on the synthesis in the system natural phosphate - ammonium sulphate . – 13th ICTAC Congress, September 12-19, Chia Laguna, Sardinia, Italy.

109. Petrova, N., P. Tzvetkov, Ts. Stanimirova, G. Kirov. 2004. Nano-sized mixed (Mg-Al) oxide products of the hydrotalcite decomposition. - 6th Annual National Workshop "NANO 2004", November 24-25, Sofia, Bulgaria, p. 108.

110. Petrova, N., Ts. Stanimirova. 2004. Anion exchange of a benzoate-intercalated layered double hydroxide: a calorimetric study, The 13th International Congress on Thermal Analysis and Calorimetry, September 12-19, Chia Laguna, Sardinia, Italy, Abstracts, p. 337.

111. Peytcheva, I, A. v. Quadt, M. Frank, B. Kamenov, C.Heinrich. 2004. The subcontinental lithosphere beneath Central Srednogorie (Bulgaria): U-Pb and Hf-zircon, Nd and Sr whole rock constraints. - In: Abstr. Goldschmidt conf., June 5-11, Copenhagen, Denmark, 5.3.P22.

112. Quadt, A. v., I. Peytcheva, C. A. Heinrich, M. Frank, B. Kamenov. 2004. Subduction related rocks in Medet Cu-porphyry deposit: sources and magma evolution. - In: Abstr. Goldschmidt conf., June 5-11, Copenhagen, Denmark, 5.5.P22.

113. Shivachev, B. L., E. P. Kashchieva, Y. B. Dimitriev. 2004. DFT calculations of cluster formation in vitreous B2O3. - 7th ESG Conference on Glass Science and Technology, April 25-28, Athens, Greece.

114. Shivachev, B., V. Ganev. 2004. DFT calculations Hydrogen Physisorption on Boron Oxide. - 6th Annual National Workshop "NANO 2004", November 24-25, Sofia, Bulgaria, p. 54.

115. Stanimirova, Ts., N. Petrova, T. Mizota, G. Kirov. 2004. Thermal behaviour of MgAlCO3 Layered double hydroxides: Formation and rehydration of metaphases. - International Tokyo Conference on Nano-structured Materials Based on Layered Inorganics, February 27-28; Tokyo, Japan

116. Tarassova, E., M. Tarassov. 2004. Chemical composition and isomorphic substitutions in allanite – (Ce) from Skrut granitoids (Belassitsa Mountain). – In: Poc. Ann. Sci. "Minerogenesis 2004", BMG, January 22-23, 56-57.

117. Titorenkova, R., B. Michailova. 2004. A local structural state of zircon from metagranites – a Raman spectroscopic study. – 6th EMU School "Spectroscopic Methods in Mineralogy" August 30 – September 8, 5th European Conf. on Mineralogy and Spectroscopy, September 4-8, Vienna, Austria, p.96.

118. Titorenkova, R., B. Michailova. 2004. A Raman microprobe study of zircon from metagranites, Ograzhdenian Mountain, Serbo-Macedonian massif. - In: Proc. Ann. Sci. "Minerogenesis 2004", BMG, January 22-23, 83-84.

119. Titorenkova, R., B. Michailova. 2004. Nanoscale structure and degree of defects of natural zircon. - 6th Annual National Workshop "NANO 2004", November 24-25, Sofia, Bulgaria, p. 109.

120. Titorenkova, R., B. Mihailova. 2004. Local structure of natural inhomogeneous zircon from metagranites. A micro-raman spectroscopic study. - 32th IGS, Florence, August 20-28., Workshop, p. 1536.

121. Vitov, O., V. Georgiev. 2004. Characteristics of the gold distribution in stream sediment pan concentrated surveys from Eastern Rhodopes, SE Bulgaria. - In: Proc. Ann. Sci. "Minerogenesis 2004", BMG, January 22-23, 26-27.

122. Vitov, O., V. Georgiev. 2004. Comparison between the Eastern Rhodopes blocks by heavy minerals concentrates data. - In: Proc. Conf., BGD,"Geology 2004", December 16-17, Sofia.

123. Yaneva. V., V. Petkova, I. Dombalov. 2004. Effect of tribochemical activation on solid state synthesis in the system Syrian phosphorite – ammonium sulphate. - National conference with foreign participation "Production and utilisatin of P-containing fertilizers and balansed fertilizing for stable agriculture", October 28, Sofia.

124. Yaneva. V., V. Petkova, I. Dombalov. 2004. Structural modifications and phase transitions under tribochemical activation of Syrian phosphorite. – National conference with foreign participation "Production and utilisation of P-containing fertilizers and balansed fertilizing for stable agriculture", October 28, Sofia.

125. Zidarov, N. 2004. National Mineralogical Database – project and realization. - In: Proc. Ann. Sci. "Minerogenesis 2004", BMG, January 22-23, 38-39.