湘鄂西寒武系烃源岩地球化学特征与沉积环境分析

通过对湘鄂西从台地-斜坡-盆地3条典型寒武系剖面烃源岩微量元素及有机碳含量（TOC，%）的分析，V/(V+Ni)、U/Th、Ni/Co表明寒武系整体上由强还原环境-氧化环境演变，且斜坡带具多个较明显的氧化还原沉积旋回；烃源岩样品稀土元素经北美页岩标准化后δEu为正异常，δCe为负异常，异常程度指示从台地-斜坡-盆地水体加深，寒武系先快速海侵后整体海退。寒武系牛蹄塘组底部烃源岩发育于高生产力、强还原的海侵环境；其有机碳高度富集可能是震旦-寒武纪之交沿伸展断裂上涌的富营养元素的还原性热液以及阵发性上升流等多重因素共同作用的结果。

Analysis of Geochemical Feature and Sediment Environment for Hydrocarbon Source Rocks of Cambrian in West Hunan-Hubei Area

Based on the analysis of TOC, trace elements of 3 typical Cambrian stratigraphic sections from platform-slope-basin in west Hunan-Hubei area. V/(V+Ni), U/Th, Ni/Co indicated Cambrian sediment turn from strong reducing environment to oxidized environment, and with a few oxidation-deoxidation sediment periodicity in slope zone. After normalized by NASC, δEu with positive anomaly and δCe with negative anomaly, and the abnormal degree showed a deeper-water from platform-slope-basin, as a whole regression after transgression in Cambrian. The environment of source rock in the bottom of Niutitang Formation was productive, strong reducing, and transgressive; the high TOC shale probably has relationship with reductive, nutritive elements-rich hydrothermal  fluid  flow, which upwelled along deep fracture during the transition from Sinian to Cambrian, and also with episodicity upwelling.