柴北缘—南祁连地区构造热事件

对柴北缘路乐河剖面新生代沉积物和山前现代河沙中碎屑的锆石U-Pb同位素热年代学研究表明:研究区物源区发育～260、～450、500～600、800～900Ma 4个主要年龄峰值和～1.8、2.5～2.6Ga 2个较小的年龄峰值。结合研究区已有的同位素年龄数据提出:柴北缘—南祁连地区在二叠纪中—晚期遭受了一次较强烈的低温区域构造热事件的改造;柴北缘高压榴辉岩及其相关的地质体隆升到地表的时间晚于上新世;柴北缘—南祁连地区先后主要经历了800～900 Ma的Rodinia超大陆裂解事件,500～600 Ma的泛非区域变质事件和～450Ma的俯冲碰撞变质事件;柴北缘—南祁连地区的主要构造热事件发生在元古代,主要集中在500～600Ma和800～900Ma,表明柴北缘—南祁连地区的前寒武纪基底性质与扬子板块相似,与华北板块完全不同。

Tectono-Thermal Events of the Northern Qaidam Margin-Southern Qilian Area,Western China

U-Pb isotopic dating of the detrital zircons from both the Cenozoic sediments in Lulehe section and the modern river sands in northern Qaidam margin show four main peak ages of ~260,~450,500-600,800-900 Ma and two small peak ages of ~1.8 Ga and 2.5-2.6 Ga.Together with the previous reported isotopic dating data in the area,we concluded that the northern Qaidam margin-southern Qilian area had been suffered a relatively strong low temperature regional metamorphism during the Middle-Late Permian.The eclogite and its related rocks were uplifted and denudated to the earth surface after Pliocene.There occurred the Rodinia super continent breaking up in 800-900 Ma,fan-African regional metamorphism in 500-600 Ma and the ~450 Ma metamorphism related to the subduction and collision in the northern Qaidam margin-southern Qilian area.The major tectono-thermal events occurred in the Paleozoic in the area,mainly in the 500-600 Ma and 800-900 Ma.It is suggested that the Pre-Cambrian basement of the northern Qaidam margin-southern Qilian area is similar to that of Yangtze plate but different from that of North China plate.