柴北缘牦牛山组火山岩锆石U-Pb年龄及其地质意义  

Zircon U-Pb Ages and Geological Significance of Volcanic Rocks from Maoniushan Formation in the Northern Margin of Qaidam Basin

作　　者：张耀玲[1,2] 倪晋宇 沈燕绪 王超群[2] 高万里[2] 胡道功[2] ZHANG Yaoling;NI Jinyu;SHEN Yanxu;WANG Chaoqun;GAO Wanli;HU Daogong(School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;Institute of Geomechanics , Chinese Academy of Geoscience , Beijing 100081, China;Minmetals Exploration and Development Co. Ltd., China Minmetals Corporation, Beijing 100010, China;Cores and Samples Center of Land ＆ Resources, Langfang, Hebei 065201, China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]中国地质科学院地质力学研究所,北京100081 [3]中国五矿集团公司五矿勘查开发有限公司,北京100010 [4]国土资源实物地质资料中心,河北廊坊065201

出　　处：《现代地质》2018年第2期329-334,共6页Geoscience

基　　金：中国地质调查局柴达木盆地及周缘油气基础地质调查子项目(121201104000150007)

摘　　要：柴北缘牦牛山组磨拉石建造不整合覆盖在前泥盆系之上,记录了该地区早古生代洋盆关闭的时间。对柴北缘牦牛山一带牦牛山组上部火山岩段两个流纹质熔结凝灰岩样品进行锆石U-Pb同位素测定,两个样品的岩浆锆石206Pb/238U年龄加权平均值分别为(396.5±2.4)Ma(n=17,MSWD=3.3)和(395.8±1.2)Ma(n=20,MSWD=1.1),均被解释为火山岩喷发年龄。结合东昆仑造山带牦牛山组测年结果,认为柴达木盆地周缘牦牛山组火山岩形成时代为晚志留世—晚泥盆世,且东昆仑与柴北缘加里东造山作用结束的时间均为早泥盆世之前,而非传统认为的晚泥盆世。The molasses of Maoniushan Formation rest unconformably on pre-Devonian strata and record the closure time of the Early Paleozoic ocean in the northern margin of Qaidam Basin. This research determinates zircon U-Pb isotopes from two rhyolite-tuff samples of volcanic rock member of upper Maomiushan Formation of Maoniushan mountain,northern margin of Qaidam Basin. The weighted mean206 Pb/238 U ages of magmatic zircons from two samples are（ 396. 5 ± 2. 4） Ma（ n = 17,MSWD = 3. 3） and（ 395. 8 ± 1. 2） Ma（ n = 20,MSWD= 1. 1）,interpreted as the formation time of the volcanic rocks. Combining past dating results about Maoniushan Formation of East Kunlun orogenic belt,we concluded that the formation time of the Maoniushan Formation around Qaidam Basin should be Late Silurian to Late Devonian,and the Caledonian movement of East Kunlun and northern margin of Qaidam Basin ended before Early Devonian instead of Late Devonian,as traditional thought.

关 键 词：牦牛山组 火山岩 锆石U-PB年龄 泥盆纪 柴北缘 

分 类 号：P588.14[天文地球—岩石学] P597[天文地球—地质学]