Geochemical and Sedimentation History of Neogene Lacustrine Sediments from the Valjevo-Mionica Basin (Serbia)

Abstract

Valjevo-Mionica Basin is one of the numerous lacustrine Neogene basins in Serbia. AfterAleksinac Basin, according to the quality and amount of oil shale, it is one of the maindeposits of this raw material in Serbia. The most important oil shale deposits in Valjevo-Mionica Basin are located in the central part of the basin (Bela stena series, Sušeočka andRadobićka Bela Stena). The kerogen content in oil shales ranged from 8 - 16 %. The averageoil yield of 6.3 % is of economical value.Total of 62 samples of Neogene lacustrine sedimentary rocks to the depth of 400 m wereinvestigated in this study. The first objective of the study was to reconstruct geologicalhistory (evolution) of the sediments i.e. to determine the palaeoconditions in depositionalenvironment during its formation. For this purpose numerous geochemical methods andapproaches were used. The second objective of the study was to determine the origin, type,maturity and liquid hydrocarbon potential of organic matter (OM). Aimed at detailedestimation of the oil shale OM potential, and prediction of the conditions necessary tobecome active oil generating source rock, pyrolytic experiments were performed on thebitumen-free sample. Bearing in mind that some metal ions (e.g. Al(III)-ion in clay minerals)(Jovančićević et al., 1993; Peters et al., 2005) have catalytic influence on most of thematuration processes, and that Pt(IV)- and Ru(III)- ions are often components of catalysts inmany laboratory investigations and industrial procedures (Hu et al., 1994; Kawaguchi et al.,2005), the pyrolytic experiments of bitumen-free rock were performed also in the presence ofsimple inorganic compounds, H2[PtCl6] and RuCl3, to investigate if their presence changesthe yield and hydrocarbon composition of liquid pyrolysates.