伊犁盆地中二叠统烃源岩有机质地球化学特征

目的 为探讨伊犁盆地中二叠统烃源岩沉积环境与地球化学特征的关系。方法 以地表剖面烃源岩的地球化学分析资料为主,结合部分井下样品分析数据,研究了泥岩的微量元素地球化学特征;利用不同岩类烃源岩有机碳含量及饱和烃气相色谱等特征,对烃源岩的沉积环境进行了研究。结果 伊犁盆地中二叠统烃源岩层系主要分布在塔姆齐萨依组,沉积水体的古盐度较高,为弱还原相-还原相沉积环境;半深湖-深湖相带沉积的还原程度强的黑灰色泥岩类烃源岩,大多有机质丰度高、类型好;河流一沼泽相带沉积的灰色-绿灰色泥岩类烃源岩有机质丰度较低、类型较差。结论 气候相对干燥、陆源碎屑物质补充不足或较长时间处于氧化程度较高的条件下沉积的碳酸盐岩类烃源岩,有机质丰度低、类型差;还原程度强、具一定深度水体的沉积相带是原始有机质沉积的良好场所,有机质能及时沉积、保存下来,且大多烃源岩有机质丰度高、类型好。

The relationship between the organic matters and source rocks geochemistry characteristics of Middle Permian series in Yili Basin

AimTo make sure that the Midlle Permian series source rocks are important, in which the sedimentary environments were the important factors for distribution of the organic metters in Yili Basin, Northwest China.The relationship between the environment and source rocks geochemistry characteristics are probed more impotantly.MethodsCombining the analysis of geochemical data about the source rocks on outcrop sections with bore specimen, the sedimentary environments about the source rocks are studied by abundance of the organic metters in the source rocks as well as saturated hydrocarbon chromatogram parameters.ResultsThe studies show that the Midlle Permian series source rocks are distributed mainly in Tamqisayi formations and the palaeosalinity was higher and the deposional environments were weak reducing to reducing. It is considered as that the zones deposited in half deep lake-deep lake where the organic matters could been buried and preserved contemporarily in strong reducing environment, there are more abundance and better types of organic metters in the source rocks such as black grey mudsource. The zones deposited in the river-delta there are less abundance and the worse types in the source rocks like green grey mudstone. ConclusionAmong the source rocks, there are least abundance and the worst types in the carbonate source rocks that deposited under the more oxide condition, in which terrienous clastic deposits were inadequate during longer time and the palaeclimate was drier relatively. The more reducing and favorable sedimentary zones are the better place,there are higher abundance of organic metters in the source rocks with strong reducing environment,where the organic matters can be buried and preserved contemporaryly, and the source rocks are generally high in organic content, or vice versa.