吐哈盆地台北凹陷侏罗系煤系源岩地球化学分类及意义

Geochemical Classification and Significance of Jurassic Coal-Bearing Source Rocks in Taibei Depression,Turpan-Hami Basin

烃源岩的沉积环境、母源输入与有机质性质有着密切联系,吐哈盆地台北凹陷不同层系、不同地区侏罗系煤系烃源岩由于其沉积环境、母源输入的不同,导致其地球化学指标差异;通过对源岩地球化学指标相关性分析表明,姥植比(Pr/Ph)是反映源岩沉积氧化还原环境和水体盐度的重要指标;C29ααα20R在C27～C29规则甾烷ααα20R中的相对含量也是反映沉积水体盐度的重要指标。同时发现源岩类型划分的主控指标是族组成中芳烃、沥青质组分含量及饱芳比、非沥比等四项指标,姥植比、伽马蜡烷指数为源岩类型划分的次控指标,据此将台北凹陷侏罗系煤系烃源岩划分为三类。

The sedimentary environments and the original inputs of source rocks close related with the nature of the organic matter,in different layers and different regions of Taibei Depression,Turpan-Hami Basin,due to the differences of the depositional environments and the original inputs of Jurassic coal-bearing source rocks,result in differences of the geochemical index.The analysis of geochemical indicators of source rocks showing that Pr/Ph and C29ααα20R relative content are important indicators of redox environment and the salinity of water.At the same time,we found that the main indicators of the type of source rocks are aromatic hydrocarbon and asphaltene contents in the group composition of soluble organic matter,the ratio of saturated hydrocarbon and aromatic hydrocarbon,also the ratio of nonhydrocarbon and asphaltene.Pr/Ph,gammacerane index are secondary indicators of classification of source rocks.The Jurassic coal-bearing source rocks can be classfied into three categories by the above index in Taibei Depression.