阿尔金断裂东段红柳峡火山岩及其周缘火山岩的岩石学、锆石成因岩相学及LA-ICP-MS U-Pb年代学对比研究显示,样品中存在两种锆石类型.一种为来自火山颈中心相样品的长柱状岩浆锆石,加权平均年龄为(109.0±1.6) Ma,属于早白垩世晚期,代表了红柳峡火山颈形成的年龄.另一种为来自火山颈周缘两个玄武岩样品的次圆或椭圆状继承锆石,且绝大部分具有核、幔结构,其U-Pb年龄分布在(138 ±2)～(2 376 ±74)Ma,展现了复杂的年龄峰值.这些继承锆石均为玄武岩浆上升过程中从下白垩统及更早地层捕获而来,它们的峰值年龄密切响应了阿尔金断裂早白垩世晚期及更早期复杂的多期岩浆及构造事件.部分年龄峰值与南阿尔金地体古生代花岗岩年龄的吻合显示阿尔金地体曾经与祁连陆块连接在一起.%This paper made a comprehensive study on the petrology,zircon morphology and LA-ICP-MS U-Pb geochronology of the Hongliuxia and its peripheral volcanic rocks in the eastern sector of the Altyn Tagh Fault.The results show that there are two types of zircons in the samples.One is a type of long-columnar magmatic zircons sampled from the volcanic neck,whose weighted average age is (109.0 ± 1.6) Ma (late Early Cretaceous),and it represents the formation age of Hongliuxia volcanic rocks.This age agrees well with previous results through different approaches.The other is a type of sub-rounded or oval inherited zircons sampled from the peripheral basalts,and most of them have the core mantle structure.The age distribution ranges from (138 ±2) to (2,376 ±74) Ma,which show the diverse age peaks.These inherited zircons are all captured from the Lower Cretaceous or/and earlier strata during the rising of basaltic magma.Their age peaks closely respond tothe complex multi-phase magma and tectonic events in the late Early Cretaceous or earlier time of the Altyn Tagh Fault.In addition,part of the age peaks coincident with the age of Paleozoic granite in the southern Altyn Tagh Terrane suggests that the Altyn Tagh Terrane was once connected to the Qilian Block.
展开▼
