塔里木盆地西北缘玉尔吐斯组硅质岩成因及石油地质意义

塔里木盆地下寒武统玉尔吐斯组是一套岩性复杂的烃源岩，该组中出现了广泛分布的层状硅质岩。层状硅质岩的形成环境较为特殊，对层状硅质岩的成因研究有助于还原玉尔吐斯组沉积时期的沉积背景，从而预测优质烃源岩的分布。利用不同露头剖面的硅质岩样品，通过薄片鉴定、SEM观察、能谱探针、有机碳含量测定等无机-有机岩石学分析认为，玉尔吐斯组硅质岩形成于裂谷背景下的高盐度、碱性封闭水体中，沉积水体的水动力变化使硅质岩具有层状构造和碎屑结构。陆源碎屑、生物以及与裂谷作用同时发生的火山活动为水体提供了硅质来源，热液为封闭水体带来了营养物质，使藻类、小壳类生物在裂谷中生长繁盛；生物的生长富集和特殊水体的良好保存条件，使玉尔吐斯组发育了良好的烃源岩层。硅质岩的岩石学、地球化学特征显示，早寒武世拉张应力条件下的大规模裂谷作用，形成了大范围展布的台内裂陷，台内裂陷环境有利于优质烃源岩的发育，研究区早古生代-新元古代地层有良好的勘探潜力。

Siliceous Rock Origin and Significance in the Uyirtus Formation Northwestern Margin of Tarim Basin

The Lower Cambrian Uyirtus Formation is a set of complicated lithological source rocks, with widely distributed bedded siliceous rocks. Bedded siliceous rocks are always formed in special environment, thus, study of siliceous rocks will help to review ancient sedimentary environment of the time when Lower Cambrian Uyirtus Formation was depositing and predict the distribution of high quality source rocks. Through rock slice, SEM, probe detection combined with TOC analysis, noticing that the siliceous rocks formed in rift background which imply the enclosed high salinity alkaline water. The dynamic changes of the sedimentary water power made the silica rock have the layered structure and clastic structure. Terrigenous clastic, volcanic activity and organisms provide silicon for the water and hydrotherm suppling nutrient for the organisms that led to a flourishing development in algae and small shell species. The distribution of organisms controlled by the position of volcanic thermal water vent and the preservation condition in special water, so the Uyirtus Formation become good source rocks. The rifting is formed by the taphrogenesis within the platform that caused by tension stress in Early Cambrian period. This tectonic movement led to deposition of widely distributed source rocks, indicating that great exploration potential in Early Paleozoic-Neoproterozoic of Tarim basin.