Alexander Vlahov

• Geological Institute, BAS

U-Pb detrital zircon geochronology provides middle Permian–earliest Triassic (272–246 Ma) maximum depositional ages for the Zelenigrad and Vranska Formations of the Belogradchik Unit. These ages match the depositional span (305–249 Ma) of the sedimentary successions in the St. Iliya Heights of the Sakar-Strandzha Zone, in addition to their structur...

Graphitization factors determine the structural state, carbon particle sizes, and industrial properties of graphite raw materials and control their use in different productions as well as the prices of graphite raw materials of different quality.

The contents of major and rare elements in 10 samples of altered (mainly zeolitized) pyroclastic rocks from the Eastern Rhodopes are investigated. The samples are selected to represent different secondary mineral associations specific to the area. The obtained results indicate that the diversity in secondary mineral associations has relatively litt...

Two X-ray diffraction methods were chosen to determine the degree of structural order (degree of graphitization) of natural carbonaceous matter. Factors influencing the graphitization processes during the progressive and regressive stages of metamorphism are examined. The correlation of the degrees of structural order of the carbonaceous material w...

Graphitization degrees and temperatures of the regional metamorphism in the Central and Eastern Rhododpes have been determined by the values of the structural parameter d002 (Å) of graphite in graphite-bear¬ing marbles and shists, from Vacha and Madan-Erma Reka areas (Madan lithotectonic unit), Ardino–Nedelino area (Startsevo lithotectonic unit), a...

The stereometric form factor and the sphericity coefficient of simple forms from the hexoctahedral crystallographic class are calculated. These characteristics determine the occurrence frequency of crystal habit types of minerals in this class.

A system for transformation, correlation, and unification of subordinations between d002 (Å) of semi-graphite and graphite, graphitization degrees and metamorphic temperature was created. The existing equations in the literature were analyzed and new equations, which determine correlation relationships between these parameters, were formulated. The...

The correlation dependence between selected X-ray structural parameters, the degree of graphitization of natural carbon substances and the temperature of the regional and contact metamorphism is examined in this paper. The results of various authors are integrated into one unified conversion system dataset. This allows the formulation of new equati...

Natural graphite is recognized as a critical raw material by the European Commission, because 95% of graphite, indispensable to the EU industry, is imported from China [246]. No industrially valuable graphite deposits have been discovered yet in Bulgaria. Graphite can provide information on the processes in metamorphic terrains (i.e. allows determi...

Graphite-bearing dolomite-calcite marbles from the Rhodopes (Byalata Skala quarry, Madan ore field, Ardino–Nedelino line and SW of Chernichevo village) were studied. The quantity of graphite in marbles varies from 0.01 to 1.67 wt.%, most often between 0.20– 0.60, and rarely up to 0.80 wt.%. The highest average graphite contents were established in...

1987) при прехода от дъл-бочинните зони към повърхността на Земята се извършва непрекъснато снижение на сумарната симетрия на минералното вещество, като кубични-те минерали намаляват за сметка на последовател-ното увеличение на ромбичните, моноклинните и триклинните. Urusov (2007) утвърждава, че средна-та симетрия на редките минерални видове е знач...

The number of the symmetry of each crystallographic class (NSCC) includes the sum of the orders of symmetry axes plus the number of symmetry planes plus one for a center of symmetry, if present. In 94.44% of cases, with increasing of NSCC values, the number of monoelement minerals crystallizing in the respective symmetry classes also increases. The...

In the vicinities of Madan, Ardino-Nedelino and Chernichevo the content of graphite (wt. %) is lowest in the white marbles (varying from 0.09 to 0.98, average 0.32%, median – 0.27), but increases in the gray-white (0.22 to 0.97, average – 0.47%) and highest in the gray marbles (0.15 to 1.61, average 0.73%, median – 0.58). With the decrease of calci...

GEOCHEMISTRY, MINERALOGY AND PETROLOGY • SOFIA ГЕОХИМИЯ, МИНЕРАЛОГИЯ И ПЕТРОЛОГИЯ • СОФИЯ 2006, 44, 41-55. Зависимост между някои рентгеноструктурни характери-стики, размерите на агрегатите и условията на образуване на графита в метаморфните скали от Родопите и Сакар Александър Влахов Alexander Vlahov. Relations between X-ray diffraction characteri...

Graphite-bearing dolomite-calcite marbles (with thickness of 120-140 m) have been found in the valley of river Vucha near the dam south of Krichim town (Трашлиев, 1989). According to Ivanov (Иванов, 1980, 1984) these rocks belong to the Posestrimo Formation but Kojouharov (Кожухаров, 1984) has defined them as part of the Vucha Formation. So far, th...