摘要： 富有机质泥页岩中往往蕴含着丰富的油气资源,而其沉积环境与发育机制是评价预测有利勘探目标的重要基础。通过露头描述、薄片观察、地化分析等手段,对塔里木盆地东北缘(塔东北)兴地断裂以北地区下寒武统泥页岩的岩石类型、沉积环境和发育机制开展研究。在西山布拉克组(SQ1)和西大山组(SQ2)2个三级层序中,确定了10类岩石: 黄褐色钙质粉砂岩、灰黑色硅质页岩、棕褐色磷质页岩、灰黑色硅质粉砂岩、灰黑色钙质粉砂岩、黑色硅质—泥质页岩、灰色泥质灰岩、灰黑色泥质—钙质页岩、灰色泥质—钙质粉砂岩、灰黑色钙质页岩。西山布拉克组沉积时期(SQ1)水体为强—中等封闭,在厌氧—无氧的环境下主要发育灰黑色硅质页岩、黑色硅质—泥质页岩和棕褐色磷质页岩等盆地相沉积。西大山组沉积时期(SQ2)水体为中等—弱封闭,贫氧—厌氧环境,主要沉积深水陆棚相。还原条件是塔东北下寒武统有机质富集的主控因素,沉积速率是控制有机质富集的次要因素,而古生产力与有机质富集无必然联系。盆内拉张构造背景下的热液事件对有机质兼具控富和降解的作用。SQ1高位体系域时期有机质富集和保存条件最佳。

关键词: 富有机质泥页岩, 发育机制, 塔里木盆地东北缘, 寒武系, 西山布拉克组, 西大山组

Abstract: Organic-rich mud shales are often rich in hydrocarbon resources,and their depositional environments and formational mechanisms are important bases for evaluating and predicting favorable exploration target. In this paper,the petrographic types,depositional environments,and developmental patterns of the Lower Cambrian shales to the north of the Xingdi Fault in northeastern Tarim Basin were investigated by means of outcrop description,thin section observation,and geochemical analysis. There are 10 types of lithofacies developed in the target strata in the study area: yellow-brown calcareous siltstone,gray-black siliceous shale,brown phosphatic shale,gray-black siliceous siltstone,gray-black calcareous siltstone,black siliceous shale,gray mud chert,gray argillaceous calcareous shale,gray argillaceous calcareous siltstone,and gray-black calcareous shale. The target interval can be divided into two third-order sequences(SQ1 and SQ2). The seawater was strongly to -moderately confined during the deposition period of the Xishanbulak Formation(SQ1),and basin-facies deposits of gray-black siliceous siltstone,gray-black siliceous shale,and brown phosphatic shale were mainly developed in an anaerobic-anoxic environment. The Xidashan Formation depositional period(SQ2) was characterized by moderately to -weakly confined water, depleted-anaerobic environment,and deep-water shelf dominant facies. Reduction condition is the main controlling factor of organic matter enrichment in the Lower Cambrian of northeastern Tarim Basin,while sedimentation rate is a secondary control of organic matter enrichment,and the palaeo-productivity is not necessarily related to organic matter enrichment. Hydrothermal events in the context of intrabasin tensional tectonics both control the enrichment and degradation of organic matter. The conditions for organic matter enrichment and preservation were optimal during the SQ1 period.

Key words: organic-rich mud shales, formational mechanisms, northeastern margin of Tarim Basin, Cambrian, Xishanbulak Formation, Xidashan Formation

中图分类号: 

• P521