【摘要】 羌塘盆地经受了青藏高原隆升事件等强烈的构造作用,盆地是否具有刚性结晶基底,对于油气的保存至关重要。长期以来对于该盆地是否具有前古生代的结晶基底,分歧较大。笔者新近在羌塘盆地中央隆起带北缘俄久卖发现的含夕线石和蓝晶石的片麻岩以及其附近发现的极浅变质的奥陶系地层,证实羌塘盆地具有变质结晶基底。本文进一步开展了片麻岩中锆石的SHRIMP年龄分析,获得了7组锆石年龄:2498～2374Ma、1780～1666Ma、645～522Ma、465～420Ma、402～369Ma、270～233Ma和223～198Ma。通过CL图象对各组年龄锆石进行成因分析,并结合区域地质特征,认为1780～1666Ma为该片麻岩的主期变质年龄,羌塘盆地具有前寒武纪结晶基底,并对其余年龄组反映的构造热事件及其地质意义进行了讨论。更多还原

【Abstract】 Whether exist crystalline basement or not? This is crucial to the petroleum preservation in the Qiangtang basin,where had undergone intense tectonism due to the Qinghai-Xizang plateau uplift.There has been much debate,for a long time,concerning the existence of pre-paleozoic crystalline basement.Recently,the authors found gneiss rocks containing sillimanite and kyanite in Ejiumai to the north of the central uplift belt in the Qiangtang basin.Combined with very low metamorphic Ordovician strata being found in this area,we conclude that there exist metamorphic crystalline basement in the Qiangtang basin.The zircon grains from the gneiss rocks yield a wide range of ages,and fall into seven groups:2498～2374Ma,1780～1666Ma,645～522Ma,465～420Ma, 402～369Ma,270～233Ma and 223～198Ma.Zircon cathodoluminescence(CL) image analyses,in conjunction with regional geological characteristics,show that the main metamorphism of the gneiss rocks occurred from 1780Ma to 1666Ma,supporting the existence of Precambrian crystalline basement in the Qiangtang basin.This paper also discusses the other age groups and their geological implications.更多还原