柴达木盆地北缘大煤沟剖面重矿物分析及其地质意义

The Heavy Mineral Analysis and its Geological Significance of Dameigou Section in Northern Caidam Basin

通过对柴达木盆地北缘大煤沟中生界地层标准剖面上重矿物的系统分析，初步查明了蚀源区母岩类型主要为中低级变质岩、沉积岩及中酸性岩浆岩和基性火山岩。提出了重矿物特征指数ＡＴｉ和ＧＺｉ的韵律性和相关性的存在，并依此把大煤沟剖面中生代地层划分为５个重矿物韵律层，分析了它们在揭示源区岩性变化及在地层划分与对比中的作用。最后探讨了ＺＴＲ指数变化与盆地构造演化的响应关系，根据ＺＴＲ指数规律性变化把中生代盆地划分为早侏罗世早期的初始断陷阶段、早侏罗世中期的主断陷阶段、早侏罗世晚期的断坳转换阶段。中侏罗世的坳陷阶段及晚侏罗世之后的反转萎缩阶段。

It has been found out that the mother rocks of erosion provenance are mainly mid-low - grade metamorphic rocks, sedimentary rocks, as well as acidic and basic rocks by the heavy mineral analysis of Dameigou section in northern Caidam basin. Then, put forward the exist of the rhythm and correlation of the heavy minerals by the rations of apatite / tourma-line (ATi) and garnet /zircon (GZi), and according to the rhythm, Dameigou section can be divided into five zones, which play important roles in revealing the change of the mother rocks and the division and correlation of different formations. At last, make an inquire into the rela-tionship between ZTR and the tectonic revolution of the basin. According to the regular changes of ZTR index ,the Mesozoic basin can be divided into five stages: first fault depression stage at J ,main fault depression stage at J ,fault- depression exchanged stage at J ,depres-sion stage at J and inversion stage after J.