Geochemistry of the Jurassic Source Rocks in the South Qiangtang Basin,Tibet

According to the surface samples and test data,the authors use analytic methods of Rock-Eval,microscopic observation,vitrinite reflectance,biomarkers comparatively and carbon isotope compositions of individual n-alkanes to analyse the organic geochemical characters of the Jurassic source rocks in South Qiangtang basin.The result reveals that the organic matter abundance of source rocks is lower in Jurassic,the type of organic matter is mainly Ⅱ1,and the overall high degree of thermal evolution to achieve high mature stage.The organic source material is mainly low-grade hydrobios,the hydrocarbon source rocks form in a certain strong salinity reduction environment.Alkane isotope analysis show that it may be quite different in the parent material for the Jurassic source rocks in each formation.Dolomite oil seepage has a strong affinity with the mudstone source rocks of Xiali Formation in the study area.