Sulphur Compound Distributions in the Upper Jurassic Source Rocks from the Dinarides

The distribution of elemental sulphur and sulphur bound in inorganic and organic compounds was investigated for three surface samples of the oil-source rock from the Upper Jurassic strata in the Dinarides. Concentrations of elemental sulphur are very low and the concentrations of sulphur bound in pyrite and sulphates are relatively low. On the other hand, organically-bound sulphur in both kerogens and bitumens is rather high, representing almost a tenth of the bitumens and the kerogens by weight. Among the organo-sulphur compounds in bitumens, analyzed by GC-MS, alkylthiophenes, alkylbithiophenes, alkylthiolanes, alkylbenzothiophenes and alkyldibenzothiophenes were identified. Among the pyrolysis products of kerogens alkylthiophenes, alkenylthiophenes and benzothiophenes were identified. Based on similar sulphur distribution and the same organo-sulphur compounds identified in the bitumens and kerogen pyrolysates, samples are thought to be geochemically related. The extremely high concentrations of organic matter and of organically-bound sulphur indicate that the depositional environment of the Upper Jurassic strata in the Dinarides was most probably anoxic and iron lean