柴东欧南凹陷上石炭统克鲁克组构造背景、物质来源及沉积环境

柴达木盆地东部（简称柴东）欧南凹陷上石炭统克鲁克组获得油气发现，但该层段的构造背景、物质来源与沉积环境动态演化过程研究依然较薄弱。通过对欧南凹陷东北侧柏树沟露头上石炭统克鲁克组（C₂k）细粒沉积岩开展元素地球化学研究，结果表明，欧南凹陷在C₂k沉积期是阿尼玛卿洋壳向北俯冲控制的主动大陆边缘活动背景下弧后裂陷盆地的组成部分，南部的柴北缘加里东构造带向其提供酸性岩浆岩为主要母岩的陆源碎屑，北部的宗务隆海槽由于枕状玄武岩喷发和低温蚀变产生溶解硅，经海底洋流上升引发硅质浮游生物群落的繁盛而沉积生物硅。C₂k沉积期处于全球范围晚古生代冰期的第Ⅲ期事件，共识别出3期次间冰期（升温事件A、B和C）。古气候温度升高引发冰川型海侵，水体随之加深，缺氧程度增强，海水的回灌和升温蒸发作用使盐度升高而咸化；其中升温B期的温度升高强度和海平面上升幅度均强于升温A期和C期，对应于C₂k最大海泛面，古水体达到弱还原状态，宗务隆海槽方向以硅质生物为代表的海洋低等水生生物供给数量增多，其他时段主要受柴北缘构造带方向陆源有机质的影响。以上研究结果及认识为探索柴达木盆地石炭纪构造—沉积—古地理演化过程和有机质富集机制提供了依据。

The tectonic setting， material source and paleoenvironment of the Upper Carboniferous Keluke Formation in the Ounan Depression of the eastern Qaidam Basin： Evidence from element geochemistry of fine-grained sedimentary rocks

The research for tectonic setting， material source and paleoenvironment of Keluke Formation in the Lower Carboniferous remains weak， although hydrocarbons have been discovered in the formation of Ounan Depression， which is located in the east of northern Qaidam Basin. The study about element geochemistry of the C₂k fine-grained deposits from the Baishugou outcrop in the northeastern depression has been investigated； and the results indicate that the depression should be one part of the back-arc rifted basin， which developed in the tectonic setting of active continental margin while the Animachen ocean crust subducting northward during C₂k. Terrigenous detrital materials were provided into the depression from parent rocks of the North Qaidam Orogenic Belt in the south， which were dominated by acidic igneous rocks. The pillow basalt were erupted in the Zongwulong Rough to the north of the depression， which were easily eroded to the dissolved silica， carried by the upwelling into the depression and subsequently transformed to the biogenic silica by thriving siliceous plankton organisms. The C₂k stage was in the phase III of the late Paleozoic ice age and three interglacial warming events （periods A， B and C） have been identified， when the temperature increment causing the transgression for the glacial ablation， palaeobathymetric increasing， anoxic event and salinity growing for the seawater recharge and heating evaporation. The intensity of temperature rise and the extent of sea level rise in the warming period B were stronger than that in the periods A and C， when the sea level reached the maximum sea surface and depositional environment was weakly-reductive in the study area during C₂k. The C₂k paleoproductivity in the outcrop was composed of terrigenous plants and ocean aquatic organisms such as siliceous organism， respectively from the directions of North Qaidam Orogenic Belt and Zongwulong Rough， which are the typical mixed terrestrial and marine organic matters. The input intensity of ocean aquatic organic matters reached the maximum in the warming period B and it was primary influenced by the terrigenous organic matter in the other periods. This study has significance for comprehending the tectonic-sedimentary-palaeogeographic evolution process and mechanism of organic matter enrichment in the Carboniferous of the Qaidam Basin.