中文摘要：

为探讨四川盆地志留系页岩氧化还原条件和古沉积环境,并给页岩气下步勘探和有利区优选提供参考,选取W201和Z106两口龙马溪组页岩取心井,进行了主微量元素和有机地球化学分析。结果表明,W201井富有机质页岩Th/U、V/Cr和Ni/Co值分别为0.3~2.3,1.49~4.27和2.51~6.7,Z106井分别为0.45~2.15,1.34~5.61和3.64~11.96,稀土元素（δCe和δEu）与微量元素一致,结合黄铁矿和笔石富集程度,指示川南上奥陶统观音桥段沉积于氧化环境,龙马溪组底部富有机质页岩沉积于滞留缺氧的还原环境。早志留世的缺氧环境与全球海平面快速上升一致,对川南龙马溪组黑色页岩的形成具有明显控制作用,形成一套稳定发育的厚度为30~40m的黑色页岩,TOC含量为1.96%~4.28%,是目前页岩气勘探开发主力层段。

英文摘要：

In order to discuss paleo redox conditions and deposition environment of the shale in the Silurian Longmaxi Formation in the Sichuan Basin,and to provide new selective targets for future exploration of shale gas in the region,a study on elemental and organic geochemistry of shales of the Longmaxi Formation from cores of the W201 and Z106 wells has been undertaken in this paper. Results show that Th / U,V / Cr,and Ni / Co ratios of the organic-enriched shale core from the W201 well are 0. 3-2. 3,1. 49- 4. 27,and 2. 51- 6. 7,respectively,whereas those of the shale core from the Z106 well are 0. 45- 2. 15,1. 34- 5. 61,3. 64- 11. 96,respectively. Characteristic of rare earth elements（ δCe and δEu） and trace elements and the enrichment of pyrite and praptolite indicate that Upper Ordovician Guanyinqiao Formation were deposited in oxic environment,while the organic-rich shale of the bottom part of the Longmaxi Formation was deposited in anoxic environment. The formation of black organic-rich shale of the Longmaxi Formation,with thickness of 30 ~ 40 m and total organic carbon content of 1. 96%-4. 28%,is obviously controlled by the anoxic environment in Early Silurian which is coincided with a rapid rise of the global sea-level. Therefore,the black shale of the lower part of the Longmaxi Formation is the main targets for exploring and developing shale gas.