准噶尔盆地北缘石炭系烃源岩元素特征及其环境意义

Trace Element Characteristic and Environment Meaning of Hydrocarbon Source Rocks in the Northern Margin of Junggar Basin

沉积岩中微量元素蕴含丰富的古环境信息,包括古水体盐度、古生产力、氧化还原性等,通过微量元素特征可以有助于评价源岩生油气潜力。利用野外样品的微量元素数据开展了准噶尔盆地北缘石炭系烃源岩沉积环境分析,石炭系样品Mn元素富集反映了强烈的火山作用对水体的影响;B、Sr、Ba等反映水体咸度的元素显示水体为弱咸水-淡水,并计算了古水体盐度：0.32‰～7.46/3.17‰,说明水体环境开放,海水受淡水改造作用强烈;V、Ni、U、Mo等氧化还原敏感指标反映当时水体处于弱还原环境,通过生源Ba重建了石炭纪古生产力。早石炭世相对于晚石炭世水体更咸,还原程度更高,古生产力较高,具有形成较高丰度烃源岩的潜力。

Trace elements in sedimentary rocks are rich in palaeoenvironments informations such as paleosalinity,paleoproductivity and the extent of oxidation and reduction for water. The characteristics of trace elements contribute to evaluate the hydrocarbon potential of source rocks. The sedimentary environment of Carboniferous hydrocarbon source rocks in the northern margin of Junggar basin is carried out using the trace element data of the field sample. The enrichment of Mn element in the carbon system reflects the strong influence of the volcanic action on the water. B,Sr,Ba and other elements reflect the characteristics of water salinity showed low salinity water. Calculation of water salinity in Carboniferous is（ 0. 32 ～ 7. 46 /3. 17） ‰,The water environment is open,and the water is strongly influenced by fresh water. V,Ni,U,Mo and other redox sensitive indicators reflect the weak reducing fresh water lacustrine environments. The source Ba indicators show reconstruction of paleoproductivity in Carboniferous by Ba. Comparison of early and Late Carboniferous,the water is more salty and the reduction degree is higher,the paleoproductivity forces are higher in early carboniferous. As a result,the Early Carboniferous is potential to develop high abundance hydrocarbon source rocks in Northern Junggar.