新疆北部中二叠统烃源岩地球化学特征与沉积环境

The Relationship between the Geochemical Characteristics and Sedimentary Environments of the Middle Permian Hydrocarbon Source Rocks in Northern Xinjiang, China

首次对新疆北部准噶尔、吐哈及伊犁盆地中二叠统碳酸盐岩类、泥岩类烃源岩的微量元素、稀土元素和有机地球化学丰度进行了系统分析 ,其主要特征是微量元素含量与同类岩石的克拉克值相比 ,有的较高 ,有的偏低 ;轻稀土富集程度较高 ,重稀土相对较低 ,Ce/ Ce*具有较明显的正异常 ,反映出烃源岩沉积环境总体为还原环境。有机地球化学分析证实 ,烃源岩中微量元素含量对沉积水体中生物的分布有一定的影响 ,部分微量元素丰度与有机质含量呈明显的正相关关系。还原程度强的沉积相带是原始有机质沉积的良好场所 ,沉积有机质能及时沉积、保存 ,烃源岩大多有机质丰度高 ;反之 。

The trace elements and rare earth elements and the organic geochemical abundance of the Middle Permian carbonate and mudstone source rocks are analyzed systematically for the first time in the northern Xinjiang region, including the Junggar basin, the Turpan-Hami basin and the Ili basin. The results show that compared with the clarke of similar rocks, the contents of trace elements are either higher or lower. The light rare earth elements are relatively enriched and the content of heavy rare earth elements is relatively low. Besides, the Ce/Ce* ratio shows an obviously positive anomaly. They reflect that the sedimentary environments of the source rocks are mainly reducing environments. The geochemical analysis confirms that the content of trace elements has some effects on the distribution of the organisms in sedimentary water bodies. The abundance of some trace elements shows an obviously positive correlation with the content of organic matter. The study demonstrates that the sedimentary face zones of strongly reducing environmenst are batter sites for the deposition of primary organic matter, where the organic matter can be buried and preserved contemporaly, so that the source rocks are generally high in organic content, and vice versa.