中国华南渝东北城口地区下寒武统烃源岩发育环境与形成机制

上扬子地台北缘发育下寒武统黑色页岩，沉积厚度大、有机碳含量高，是一套重要的烃源岩，具有重要的勘探价值。恢复其发育环境和碎屑物源，对烃源岩分布预测具有重要意义。通过对华南渝东北城口地区野外露头系统取样并开展地球化学测试，研究了黑色页岩的形成环境与物源供应，探讨气候变化与陆源输入对黑色页岩形成的控制作用，重建优质烃源岩的形成过程。分析结果表明，黑色页岩具有高的Al₂O₃含量（7.38%~13.90%）、K₂O含量（1.01%~2.93%）、Na₂O含量（1.98%~2.88%）和总Fe₂O₃含量（2.35%~5.36%），富集V（平均值为242 μg/g）、Cr（平均值为83 μg/g）、Ni（平均值为58 μg/g）等微量元素。CIA、K/Al和Rb/Al指示黑色页岩沉积期气候为温暖湿润，V/Cr、U/Th、Ce/Ce*、Mo_EF?U_EF指沉积水体经历缺氧→次氧化→缺氧→次氧化四个阶段，正Eu/Eu*异常指示早期存在海底热水活动，Th/Sc?Zr/Sc图表明黑色页岩沉积组分未经历再循环过程，可以有效判别源区；Co/Th?La/Sc图和La/Th?Hf图确定黑色页岩存在长英质和铁镁质两种源岩类型，并且汉南古陆是有效物源区。

Development Environment and Formation Mechanism of Lower Cambrian Source Rocks in the Chengkou Area,Northeast Chongqing,South China

The Lower Cambrian black shale at the northern margin of the Upper Yangtze Platform is an important source rock with large sedimentary thickness and high organic carbon content， which gives it important oil and gas exploration value. Restoring its developmental environment and clastic provenance is of great significance for the prediction of hydrocarbon source rock distribution. By systematic field outcrop sampling in the Chengkou area， South China， and geochemical testing， this study investigated the formation environment and source supply of the black shale and discusses the effect of climate change and terrigenous input on the formation of the black shale. It also reconstructs the process by which these excellent?quality hydrocarbon source rocks were formed. The results showed that the black shale has high Al₂O₃ content （7.38?13.90%）， K₂O content （1.01?2.93%）， Na₂O content （1.98?2.88%） and total Fe₂O₃ content （2.35?5.36%）， and is enriched by trace elements such as V （average 242 μg/g）， Cr （average 83 μg/g） and Ni （average 58 μg/g）. CIA， K/Al and Rb/Al ratios indicate that the climate was warm and humid during the period of black shale deposition. V/Cr， U/Th， Ce/Ce* and MoEF?UEF indicate that the sedimentary waterbody underwent an anoxic → suboxic → anoxic → suboxic cycle. A positive Eu/Eu* anomaly also suggests the occurrence of early submarine hydrothermal activity. The Th/Sc ? Zr/Sc chart indicates that the sedimentary components of the black shale did not undergo a recycling process， and it is therefore possible to effectively identify the location of the source. The Co/Th?La/Sc and La/Th?Hf diagrams confirm the presence of both felsic and mafic source rocks in the black shale. The Hannan paleo?uplift may have been an effective source area.