VOLUME 32 (2-4)/December 2002 110th Anniversary of Acad. Prof. Strashimir Dimitrov; XVII Congress of the Carpathian-Balkan Geological Association

Strashimir Dimitrov was born on 10 August 1892 in the city of Sofia in a poor and large family – his father Dimitar Giorev Mechkarski and his mother – Susana Igova Kilimarska had 13 children. "The most important family traits of the Giorevs, parents and children, are natural intelligence, studiousness, persistent conscientious and beneficial diligence, good manner to neighbours, clients, fellow-citizens; sharp sense of duty and justice. These inherited and acquired virtues were the most specific features of Strashimir Dimitrov that built him up as a first class scientist and valorous citizen who was respected and loved by everybody." - writes Academician Prof. Ivan Kostov about the stock of Strashimir Dimitrov...

The structure and evolution of the pre-Alpine basement of Europe have been recently subject of active research. The results of this research clarified many of the features of the peri-Gondwanan elements in this basement. Several advantages characterize the pre-Early Palaeozoic basement in the considered here region compared to that of alpine Europe. Most of these advantages are related to the lesser degree of reworking of the analysed basement during the Variscan and Alpine tectogenesis.
   Both terranes treated are the basement of the Balkan terrane (Haydoutov, Yanev, 1997) and the eastern part of the Rhodope Massif.

The Precambrian ophiolites in the Rhodope Massif have been altered under different metamorphic conditions and as a result varied products were formed. Some of them show textures resembling to magmatic ones, and often were recognized by field investigations as basic magmatites. Here are presented three principal instances of pseudomagmatic texture appearance.

The Chelopech region is the host of Europe's largest gold deposit Chelopech, and is situated about 65 km east of Sofia at the foot of Stara Planina Mountain. It is whithin the northhermost part of the Panagyurishte ore district which includes many large porphyry-Cu and epithermal deposits. The Panagyurishte ore district belongs to central Srednogorie volcano-intrusive area, and is part of the Srednogorie Late Cretaceous island arc (Dabovski et al., 1991). The area is charcterized by the development of Late Cretaceous volcano-plutonic complexes consisting mainly of andesites, dacites, granodiorites, and quartz-monzodiorites grouped in 4 temporal stages accordin to Lilov and Chipchakova (1999): I^st, >91; II^nd, 91-88; III^rd, 88-86; IV^th, 67-65 Ma...

Catastrophic sediments are formed under the influence of sharp and short-term natural phenomena – earthquakes, tsunami, hurricanes, storms, submarine slumps, continuous torrential rains etc. They could be caused by different reasons (relief and land dynamics, shelf and continental slope, sharp climatic changes, impact and orbital influences etc.) which have outside (allocyclic) character in respect to the deposition. These deposits are named catastrophic because they are a result of the very short-term phenomena (Ager, 1974, 1993; Einsele, 1991; Seilacher, 1991). 
   The sediments discussed are genetically and dynamically determined and characterized in diverse Lower Cretaceous cross sections in Bulgaria. The basic types of catastrophic deposits in the Bulgarian Lower Cretaceous record are: debrites and diamictites with chaotic structure, very thick extensive debrites, as well as tempestites and beds with hummocky cross stratification (HCS). Specific event deposits are so called fluxoturbidites, whose origin is connected to the combination between turbiditic curents and significant submarine slumping. Generally these are thick-bedded deposits with slightly expressed graded stratification, often with chaotic structure and practically without any marks on the lower bed surface of the sand beds.
   The following types of catasttophic deposits were established in the Lower Cretaceous sections in the region of the Central and Eastern Balkan: 1) mass debris flow deposits - debrites and diamictites (or mixtites); 2) tempestites; 3) sediments with hummocky-cross-stratified bedding; 4) submarine slumps and slumping. Their formation is conditioned by the specificy of the palaeogeographic environment...

The events (physical, geochemical, biological – in the modern sense of the event stratigraphy) in the Maastrichtian and Danian in Bulgaria recently have been a subject of several publications. The main part of them is concentrated on the impact event at the Cretaceous/Tertiary (K/T) boundary and its consequences.
   After the discovery of the K/T boundary clay bed near Bjala (Stoykova, Ivanov, 1992), many authors had explored this locality and represented new data about the iridium anomaly in Bjala sections (Preisinger et aI., 1993a, b; Rogl et aI., 1996). Biological events and biostratigraphy across the K/T boundary in these sections are studied and discussed by Ivanov, Stoykova (1994), Stoykova, Ivanov (1995), Cтoйкoвa, Иванов (1996). The K/T boundary is located in the flysh section near Emona as well (Sinnyovsky, Stoykova, 1995). Later on, Синьовски (1999) reported an iridium anomaly at the K/T boundary in a clay bed, situated in-between shallow-water carbonate sediments in Mezdra region (NW Bulgaria).
   Many articles (or parts of articles) have been devoted to the problem of mass extinction and biological changes among the different fossil groups: calcareous nannoplankton – Preisinger et aI. (1993a, b) Ivanov, Stoykova (1994,1995), Ragl et aI.(1996), Cтoйкoвa, Иванов (1996);  planktonic foraminifera – Ragl et aI. (1996), Adatte ,et aI. (2002); benthic foraminifera – Вълчев (2001); macroinvertebrates – Ivanov Stoykova (1994), Stoykova, Ivanov (1995), Cтoйкoвa, Иванов (1996); Mileva-Ilieva (1998, 2000). There are two comprehensive studies on the K/T boundary in Bulgaria recently published – Стойкова и др. (2000), Adatte et aI. (2002). These papers summarize all data, that had been obtained from the different studies (stratigraphical, sedimentological, paleontological, mineralogical, geochemical, isotope), as well as newly acquired data andinterpretations.
   The value of other types of event-markers in the Maastrichtian – Danian interval is still poorly examined. Until now, Синьовски (1999) documented slumps, tephra-markers (beds containing volcanic ash) and biological events (colonization and immigration of fauna) in Maastrichtian-Danian of Mezdra region. Unfortunately
these event-markers are discerned in a restricted area and it's difficult to estimate their reliability for correlation.
   The first attempts for sequence stratigraphy subdivision of the Maastrichtian-Danian interval are made in the last few years. Синьовски (1999) divided two sequence units in this interval in Mezdra region. Вангелов (2000) separated two units in the Maastrichtian and one in the Maastrichtian-Danian in the East Balkan, Central Balkan-Fore Balkan and East Moesian Platform.
   The formulation of the present study is based of the choice of maximum informative for our purpose objects (sections). Therefore we discarded several well known to the geological community sections. We used only sections, which meet the following requirements: a) to have relatively continuous sedimentation across the  Maastrichtian-Danian, including the K/T border; b) to display different facial and bathymetrical zones in the basin. Three types of sections/environments can be distinguished: shallow-water, hemipelagic and deep-water.
The main goals of the study are: 1) to summarize all available data on the K/T boundary studies in Bulgaria, as well as to reveal some newly obtained data for correlation of the event-markers in the  Maastrichtian-Danian interval; 2) to produce a sequence stratigraphy subdivision and correlation of the third-order units in the interval.

Franz Toula (1890, 1892) expressed his opinion that the rocks in the vicinity of Varna and southernly of the town are similar to those from the Kerch Peninsula. Therefore all the rest investigators accepted these rocks as formed in the Euxinian basin during the Middle Miocene subage.
   The Middle Miocene Subseries in Northeastern Bulgaria is comparatively well studied. The Regional Stages according to the scheme of the Eastern Paratethys, and namely the Tarkhanian, Chokrakian, Karaganian, Konkian and Sarmatian (s.l.) Regional Stage are distinguished.
   In the last years extensive research has been done in a part of Northeastern Bulgaria (Fig. 1). The presence of some species in the gathered collection of molluscs, and some referred to in the publications, request a revision of the concepts concerning the presence and volume of some stages and substages as well as their correlation.

The Panagyurishte ore district in Bulgaria includes three significant porphyry copper (-gold) deposits (Medet, Elatsite and Assarel), and several small ones (Vlaikov Vruh, Tsar Asen, Petelovo and others). The porphyry copper deposits in the district were objects of intensive investigations during the last decades and numerous studies provide data about these hydrothermal systems and their mineral composition (Strashimirov et aI., 2000).
   The aim of the present paper is to summarize and determine correctly the hydrothermal alteration of the host rock according to the two most preferable genetic classifications: 1) the classification given by Meyer and Hemley (1967), which is used in the USA, Australia, Japan, New Zealand, UK, Spain, France, Italy, etc., and 2) the classification on a formation-facial basis given by Жариков, Омеляненко (1978), which is used in the East and Central European countries, Sweden, China, etc...

Klisoura occurence is located close to Klisoura Village, about 6 km west of the town of Bankya. Host rocks are Upper Cretaceous andesite pyroclastics, some andesite bodies and veins that form the core of Radui anticline – part of Viskyar-Vitosha synclinorium. The hydrothermallly altered rocks cover an area of about 2 km² and are exposed around the intersection center of several fault systems. Кунов et al. (2000) described the occurence as epithermal, of acid-sulfate type. 
   The main aim of the present study is to trace the behaviour of rare elements in the process of advanced argillic alteration that lead to the formation of secondary quartzites in the occurrence. The conclusion are based on the distribution of rare elements in different alteration types – from less to more intensively altered varieties. Here, the term "zone" is used as a synonim of "hydrothermally altered rock type" since the latter forms the zones of hydrothermal alterations.
   Samples from all alteration types were collected during the field studies. Materails from drillhole No3 (drilled in 1974) were also analyzed. The main components and 18 rare elements were analyzed by X-ray fluorescence and atomic absorption.

The presented note is reporting some midterm results of the NATO "Science for Peace" Program Project SiP 973739 "WATMETAPOL" gained by scientists from the Geological Institute, BAS - Sofia (in collaboration with BRGM, Orleans - France and the University of Antwerp - Belgium) and financed for a period of 3 years (2001-2004) (224 000 EUR).
   The main project goals are:
   • To establish the distribution, speciation and interactions of heavy metal pollutants and As in soil surface and groundwater in the Plovdiv-Asenovgrad region and the pollutants changes with time;
   •To develop a 3D GIS modeling of surface and groundwater pollution sensitivity and GIS based pollution-risk assessment tools and methods;
   • To develop a predictive coupled geochemical and transport computer model for studying the evolution of the pollution with the aim of limiting its harmful effects.
   The obtained results will be submitted to the end users: Ministry of Environment and Waters Government of Plovdiv Region, Ministry of Health, Ministry of Economy, Ministry of Agriculture and Forestry.

The anthropogenic factor is an equally important factor among the natural phenomena, changing the geological environment. It is displayed to a much higher extent than the natural processes in some sites as open-cast mines, quarries, aggregate quarries, tailing ponds, refuse dumps, landfills, etc. The natural environment is transformed within only a few years to such an outlook, which is impossible to acquire in the course of hundreds of years. A great part of the anthropogenic effects are analogous to the natural ones and have one and the same physical character. A corresponding technogenic analogue is correlated with each natural destructive geological process. However, the proceeding slow changes in nature in the course of hundreds and millions of years take place in a very short time – months and years, as a result of the anthropogenic impact. This impact is concentrated on relatively smaller areas compared to the general scale of the natural processes. The geological hazard in the case of technogenic processes ensues from the fast rates of their development and intensity in particular sites, when the geomorphological, hydrogeological and engineering geological conditions are drastically changed in a very short time. The so called anthropogenic relief is created, which changes radically the geological environment and redirects also the manifestation of the natural processes as the erosion, abrasion, suffusion, weathering, etc., creating at the same time new geostatic and geodynamic conditions by the changed loading in particular parts of the massif. The acting forces in the geological geological environment are redistributed and a new equilibrium is reached, when it is possible to activate processes as slow creep along the slopes with subsequent landslides. These are one of the most often displayed anthropogenic changes of the geological environment in the open-cast mine development. The stability of the newly formed slopes is always very important in the case of open-cast mine workings. Regardless of this fact, the preliminary calculations cannot always exclude landslide occurrence. There are many similar examples from the open-cast mines in "Maritsa-Iztok", "Medet", "Assarel", "Elatsite", "Pernik", "Kremikovtsi" and elsewhere.

The historical review of the seismic activity shows that strong earthquakes with destructive effects took place in the Sofia kettle. There are data for the display of sufficiently powerful seismic events in the Sofia zone that had been reflected in historical documents as early as in the XV century. Four strong earthquakes occurred in this region during the period from the beginning of the XIX century till now that caused significant damages, the most powerful one being in 1858 (intensity of IX degree according to the MSK-64 scale and magnitude of about 6.5-7.0).
   According to the seismic zoning of Bulgaria for a period longer than 1000 years and average engineering geological conditions, the kettle falls entirely within a region with expected intensity of IX degree according to the MSK-64 scale with a seismic coefficient K = 0.27 (Boncev et aI., 1982; Norms for ..., 1987).
   The engineering geological characteristics of the Sofia kettle are the basis for determining the influence of the soil conditions on the effects of the seismic activity. Complex geologicalgeophysical investigations were carried out in the Sofia kettle during the period 1967-1970 in connection with the seismic microzoning of the territory of the Sofia City and the Sofia basin. On the basis of the engineering geological studies and the micro-seismic investigations (Petkov, Christoskov, 1965; Demirev et aI., 1971; Petrov, Iliev, 1971), the first attempts for preliminary seismic micro-zoning of the Sofia City and its surroundings were made, which were applied in practice too. The coefficient of variation of the seismic intensity is calculated according to the formula of Medvedev, the parameters of the monzonites and syenites of the Vitosha pluton being considered as reference ones. The values of this coefficient reach up to 3, and for the most unfavorable ground conditions - even to 3.5.

The Palaeozoic flysch sediments from outcrops in the region of Cherna Gora (Kraishte area) are investigated by sedimentologists in scope of flysch rhythmics and presence of different lithological types (Yanev, 1985).
   Data about determined thickness and age of the lithostratigraphical units are analysed in the present study without commenting on the differences and analogies in sedimentological aspect that have served as argument in introducing three lithostratigraphical units, and namely, the Parchar, Tumba and Propalnitsa Formation.
   The thickness and the age data in the formal introduction of the Parchar, Tumba and Propalnitsa Formation are pointed by Yanev, Spassov (1985).
   Parchar Formation. The age of the Formation is determined on the base of conodonts as Late Givetian - Frasnian. The thickness is 640-770 m.
   Tumba Formation. The Famennian age of the Formation is not supported by palaeontological data. Its stratigraphical position between dated sediments of Parchar and Propalnitsa Formation is an argument to assign Tumba Formation to the Famennian stage. Taken dimension of the apparent thickness is 45-250 m.
   Propalnitsa Formation. The Formation according to determined macroflora is referred to the Late Famennian up to the Early Carboniferous for the uppermost parts of the Formation. The thickness is more than 540 m.

The sedimentary fill of Sofia Basin represents a large variety of sedimentary rocks grouped into four lithostratigraphic units – variegated terrigenous formation, Gniljane, Novi Iskar and Lozenec Formations (Kamenov, Kojumdgieva, 1983) that represent the distinct stages of the basin evolution - alluvial, marshy-lacustrine and lacustrine.
   The variegated terrigenous formation is presented by irregular alternation of clayshales, siltshales, sands and sandstones, varying in color. Gniljane Formation comprises conglomerates, sands and sandstones, siltstones and silty clayshales with lignite interbeds In the upper part (Balsha Member). Novi Iskar Formation comprises gray to gray-bluish clays, diatomaceous clays, silty clays and siltshales as well as varves, composed of alternation of carbonaceous and clayey siltshales. Lozenec Formation consists of irregular alternation of clays, siltshales, sands, and conglomerates with lignite interbeds (Novi Han Member) in the lowermost part of the formation and with micrite limestones (Bogiovci Member) in the upper part of the formation (Yaneva, 1998). The thickness of Neogene sediments in Sofia basin varies from 10 m in the borders up to 1400m in the central parts.

The Apuseni-Banat-Timok-Srednogorie (ABTS) Magmatic and Metallogenic Belt can be traced from the Apuseni Mountains in the north, through the western part of the South Carpathians (Banat) in Romania, the Timok region in East Serbia, the Srednogorie zone (Bulgaria) and continues in Turkey through the Black Sea.
   The basement belongs to the southern margin of the European continent. The ABTS Belt is unconformly superimposed on older structures, including the Early Cretaceous ones. Furthermore, it crosses the Vardar ophiolite suture in the Mures and Voevodina regions. These facts indicate a new stage in the alpine evolution which followed the subduction of the Vardar Ocean and subsequent collision. This new stage was characterized by an extensional geodynamic regime. The ABTS arcuate rift was formed as a result of postcollisional orogenic collapse.
   The Late Cretaceous magmatic activity with submarine volcanic rocks and comagmatic intrusions began during the Cenomanian and ended during the Maastrichtian. Volcanic and associated predominantly flysch-type sedimentary deposits form a 2-3 to 7-8 km thick pile. The magma generation in ABTS extensional belt was realized in different depth level, which determines differences of melt compositions. Rock association of calc-alkaline, tholeitic, subalkaline and alkaline series are established. The petrologic features of the alkaline and subalkaline rocks and several Sr isotope analyses show the mantle origin of the parent magma. The calc-alkaline magma was generated predominantly around the boundary between mantle and lower crust.
   Porphyry copper and copper massive sulphide deposits are the most important. Some of them have an economical content of gold and/or molybdenum. There are skarn and vein type copper deposits, too. Other important deposits are iron, tungsten-molybdenum and lead-zinc skarn deposits. Besides, small hydrothermal base metal-gold, barite, porphyry gold, silver and volcano-sedimentary iron-manganese deposits are known. The plutonic, subvolcano-plutonic, volcano-plutonic, volcano-subvolcanic and volcanic ore-bearing structures are distinguished. The geochemical associations show the predominance of mantle sources of the ore-forming fluids.

П. Попов, Т. Берза, А. Грубич, Д. Йоане. Позднемеловой магматический и металлогенический пояс Апуссены-Банат-Тимок-Средногорие (АБТС) в Карпато-Балканском орогене. Магматический и металлогенический пояс Апуссены-Банат-Тимок-Средногорие (АБТС) начинается с Апуссенских гор (с севера), проходит через западную часть Южных Карпат (Банат - в Румынии), через Тимокский район (в восточной Сербии) и далее, охватывая Средногорскую зону (Болгария), продолжается через Черное море на территории Турции.
   Его основание принадлежит к южной окраине Европейского континента. АБТС пояс наложен несогласно на более древние, вкл. раннемеловые  структуры. Более того - в районах Муреш и Воеводина он пересекает Вардарскую офиолитовую зону. Это показывает, что образование пояса связано с новым этапом альпийской эволюции, наступившим после субдукции Вардарского океана и последовавшей за ней коллизией. Этот новый этап протекал в условиях экстенсионного геодинамическото режима, а пояс оформлен в результате постколизионного обрушения орогенной постройки.
   Характерная для пояса позднемеловая магматическая активность с ее субаквальными вулканическими породами и комагматическими интрузиями началась в сеномане и закончилась в маастрихте. Вулканические породы и ассоциирующие с ними осадочные отложения преимущественно флишевого типа слагают разрезы мощностью в 2-3 до 7-8 km. Генерирование магмы в АБТС поясе осуществлялось на разных глубинах, что и определило различия в составе расплавов. Ассоциации пород принадлежат к известково-щелочной, толеитовой, субщелочной и щелочной сериям. Петрологические особенности щелочных и субщелочных пород и данные по Sr-изотопам указывают на мантийный генезис расплавов. Известково-щелочные магмы генерировались преимущественно в зоне между мантией и нижней корой.
   Самыми важными для пояса являются сульфидные медные оруденения (вкрапленные и массивные). Некоторые из них содержат промышленные количества золото и/или молибдена. Кроме того установлены медные месторождения скарнового и жильного типа. Важное значение имеют железные, оловяно-молибденовые и свинцово-цинковые скарновые месторождения. Кроме того в обхвате пояса размещены небольшие полиметаллические - золотые, баритовые, вкрапленные золотые и серебряные, а также вулканогенно-осадочные железо-марганцевые месторождения. Выявлены плутонические, субвулканические-плутонические, вулканические-плутонические и вулканические рудовмещающие структуры. Геохимические ассоциации указывают на преимущественно мантийные источники рудогенерирующих флюидов.

Results from X-ray diffraction analyses of Albian phosphorites from deposits Sanadinovo, Dekoy and Brushlen indicate presence mainly of fluorapatite and partly of chlorapatite and carbonate fluorapatite (francolite). The microprobe analyses of phosphate grains, coatings, cements, ammonite, wood, and shark tooth determined the following contents (in weight %): 26,65-41,02 P₂O₅ 45,19-57,17 CaO, 2,58-4,64 F, up to 0,80 CI, and silicate components from the admixtures in phosphate minerals. Fifteen crystallochemical formulae were calculated. They are characteristic with Ca_9.54-9.58[PO₄]_5.77-5.78FI_1.48-2.81 and Cl_0.06-0.30. Generally fluorapaiIte was determimid in 9 samples; and chlorine containing fluorapatite - in 6 samples.
   The exemplary crystallochemical formulae are:
   Ca_9.54[PO₄]_5.78F_2.75 - fluorapatite
   Ca_9.58[PO₄]_5.77F_1.94CI_0.30 - chlorine containing fluorapatite
   The presence of CO^3- and OH in the phosphate minerals was not substantiated by direct data. The studied phosphate minerals show high solubility in lemon acid (30-80%). This indicates defects in the crystal lattices caused by the presence of chlorine and most probably of carbonate group.

И. Начев. Фосфатные минералы альбских фосфоритов в Болгарии. Альбские фосфориты из месторождений Санадиново, Деков и Брышлян исследованы рентгено-структурным дифракционным методом. Установлено, что фосфориты сложены главным образом фторапатитом (франколитом). Под электронным микроскопом исследованы фосфатные зерна, внешние зоны зерен, образцы цимента, аммонит, обломок древесины и акулий зуб. Исследования показали, что фосфаты содержат (в весовых %): Р₂О – 26,65-41,02%; СаО – 45,19-57,17%; F – 2,58-4,64%; Cl – более 0,80%, а также – силикатны компонент, котороы смешан с фосфотными минералами. Вычислено 15 кристаллохимических формул.
   Для них характерны следующие соотношения:
   Са_9,54-9,58[PO₄]_5,77-5,78F_1,48-2,81 и Cl_0,06-0,30. Хлорапатит с представителной формулой Са_9,54[PO₄]_5,78F_2,75 установлен в 9 образцах, а хлор-содержащий фторапатит (представительная формула - Са_9,58[PO₄]_5,77F_1,94Cl_0,30) – в 6 образцах.
   Присуствие СО^3- и ОН в фосфатных минералах не доказано непосредственно. Фосфатные минералы слабо растворяются в 30-80% ли монной кислоте. Эта особенность связана с дефектами кристаллов в связи с присуствием хлора и по всей вероятности – карбонатной группы.