皖南地区晚二叠世—早三叠世页岩沉积环境及物源指示意义

晚二叠世—早三叠世地球经历了重大的气候环境—生物种类更替，该时期皖南地区发育了一套黑色页岩，不仅可以作为非常规油气资源的储层，而且为该时期气候环境演变研究提供了良好的载体。针对该套黑色页岩古环境演变及物源，前人采用多种手段和方法开展了研究，但仍存在不同的观点。因此，基于宏观—微观岩石学特征，结合地球化学数据，对皖南地区下二叠统大隆组—上三叠统殷坑组页岩古气候和物源输入及其有机质富集控制因素进行分析，开展页岩古环境演变及物源研究。结果表明：微量元素及草莓状黄铁矿（<6μm）指示页岩形成于温暖潮湿且波动频繁的缺氧—硫化环境，由大隆组至殷坑组，缺氧条件和古生产力整体呈逐渐降低趋势；w(Th)/w(Sc)—w(Zr)/w(Sc)、w(La)/w(Sc)—w(Co)/w(Th)和w(Hf)—w(La)/w(Th)图解以及稀土元素配分模式表明页岩物源主要来自后太古代上地壳花岗岩，w(La)—w(Th)—w(Sc)、w(Th)—w(Co)—w(Zr/10)和w(Th)—w(Sc)—w(Zr/10)判别图显示页岩物源的构造背景为大陆岛弧，兼具活动大陆边缘，推断其主要来自“江南造山带”；氧化还原条...

Depositional environment and provenance of Late Permian-Early Triassic shale in the Wannan area

From the Late Permian to the Early Triassic, the earth experienced significant climatic and biological changes. A set of black shale successions had developed in southern Anhui during this period that is not only served as a reservoir of unconventional oil and gas resources, but also completely records the evolution of climate and environment of this period. For this set of black shale paleoenvironmental evolution and provenance, predecessors have used a variety of means and methods to carry out research, but there are still different views. Therefore, based on macro-micro petrology and geochemical data, the paleoclimate and provenance input of the Lower Permian Dalong Formation-Upper Triassic Yinkeng Formation shale in southern Anhui, as well as the controlling factors of organic matter enrichment, were analyzed, and the evolution of shale paleoenvironment and provenance were studied. The result implies that trace elements and framboidal pyrites (<6 μm) indicate that shale was formed in a warm, humid and frequently fluctuating anoxic-sulfidic environment. The anoxic conditions and primary productivities of shale show an overall downward trend from the Dalong Formation to the Yinkeng Formation. The discriminant diagram of w（Th）/w（Sc）-w（Zr）/w（Sc），w（La）/w（Sc）-w（Co）/w（Th） and w（Hf）-w（La）/w（Th） and the REE partition model indicate that the shale source is mainly from the post-Archean upper crust granite. The discriminant maps of w（La）-w（Th）-w（Sc），w（Th）-w（Co）-w（Zr/10） and w（Th）-w（Sc）-w（Zr/10） show that the tectonic background of the shale is continental island arc with active continental margin, it is considered that the provenance may come from the southern “Jiangnan orogenic belt”. Redox conditions and primary productivity played important roles in organic matter accumulation.