ANALIZA GEOCHEMICZNA I KORELACJE GENETYCZNE BITUMINÓW I SKAŁ TYPU CZARNYCH ŁUPKÓW W JEDNOSTKACH TEKTONICZNYCH KARPAT ZEWNĘTRZNYCH W POŁUDNIOWO-WSCHODNIEJ POLSCE I NA OBSZARZE PRZYLEGŁYM

Abstract

GEOCHEMICAL ANALYSIS AND GENETIC CORRELATIONS FOR BITUMENS AND ROCKS OF THE BLACK SHALE TYPE IN THE OUTER CARPATHIANS TECTONIC UNITS IN SOUTHEASTERN POLAND AND THE ADJACENT TERRITORYAbstract. Studies were conducted in the Outer Carpathians in the area of the Western and Eastern Carpathians in the borderland of Poland, Slovakia and Ukraine. The character of anoxic facies in the Carpathians in the Polish and Slovak area within different tectonic units - from the Dukla unit through the Silesian, Boryslav-Pokuttia, Skole and the Węglówka units was analyzed. The analysis was based on geochemical parameters and indices from the following methods: Rock-Eval analysis, gas chromatography of n-alkanes and isoprenoids, isotopic determinations of carbon isotopes (in organic matter). Diversity of parameters has been stated. In case of bitumens, the TOC content changes within the interval from 0.62% to over 8.7wt %, while the highest values characterize the facies of the Skole unit. The potential maturity of the sediments is very high in the anoxic facies of the Silesian and Dukla units and in the Central Carpathian Depression (CDK). Residual petroleum potential (S2) of the dispersed organic matter varies from 0.26/1.20 mg HC/g rock in the Lower Cretaceous strata of the Bystre Slice to 16.50/36.59 mg HC/g rock in the Skole unit (Bandrów). It is moderate in the Polish and Slovak segments in the Dukla unit and slightly higher in the Magura and Boryslav-Pokuttia units. The aliphatic fraction dominates in all the studied rocks, while the aliphatic composition of bitumens is relatively homogeneous. The n-alkane distribution is variable in the rocks and solid bitumens. Three groups of bitumens may be distinguished with a variable domination of short-chain n-alkanes and/or long-chain n-alkanes. In general, pristane predominates over phytane, while the isoprenoids often show a lower content in comparison to the adjacent C17 and C18 n-alkanes. The pristine - phytane ratio oscillates from 18.01 (Central Carpathian Depression – CDK) through 13.36 (Węglówka unit) to 6.36 (Silesian unit), being close to one in other samples. Among the aromatic hydrocarbons, phenantrene predominates together with its methyl and di-metlyl derivatives. The δ13CPDB data for hydrocarbons show some variability for different fractions. For bitumens, they change from –24.9 to –28.9‰. Thermal maturity of kerogen (mixed type from II to III) varies from the immature phase (Skole and Boryslav-Pokuttia units) through mature in the Silesian and Dukla units up to the early gas phase in the tectonic mélange and its neighbourhood.