新疆西准噶尔克拉玛依岩体中暗色岩墙的形成时代及地质意义--来自锆石LA-ICP-MS和角闪石Ar-Ar定年的证据  

Ages and geological significance of the dark dykes emplaced in the Karamay pluton and adjacent area,in western Junggar,Xinjiang,NW China:Evidence form LA-ICP-MS zircon chronology and Ar-Ar amphibole chronology

作　　者：冯乾文 李锦轶 刘建峰 宋彪[1,2] 王彦斌[1,2] 陈文 张彦 

机构地区：[1]巾闰地质科学院地质研究所,北京100037 [2]北京离子探针中心,北京100037

出　　处：《岩石学报》2012年第7期2158-2170,共13页Acta Petrologica Sinica

基　　金：国家973项目(2007CB411306、2001CB409810);国土资源大调查工作项目(1212010711817、1212010611806)联合资助

摘　　要：新疆西准噶尔克拉玛依岩体以及周围地层中存在着大量暗色闪长玢岩岩墙,是岩浆物质贯入3组走向不同的裂隙形成的。对其中一个闪长玢岩岩墙样品进行锆石LA-ICP-MS年代学测试,得到303.1±1.2Ma的锆石206Pb/238U加权平均年龄,对从该闪长玢岩中分离出的角闪石进行Ar-Ar年代学测试,得到312.1±2.8Ma的坪年龄(1120～1400℃)和313.6±6.9Ma的反等时线年龄。对该闪长玢岩岩墙附近的含角闪石黑云母二长花岗岩进行的锆石LA-ICP-MS年代学测试,获得其206Pb/238U加权平均年龄为319.0±1.0Ma。对侵入石炭纪地层的一个花岗斑岩岩脉样品进行锆石LA-ICP-MS年代学测试,得到了315.3±1.0Ma的206Pb/238U加权平均年龄。上述年代学测试结果表明克拉玛依市以西地区的暗色岩墙形成时代是石炭纪末期,不是前人所说的二叠纪。在这些岩墙形成之前,该区在石炭纪晚期还发育以克拉玛依岩体及附近酸性岩脉为代表的花岗质岩浆活动。上述围岩和岩墙的年代学资料揭示出该区闪长玢岩岩墙所占据的裂隙形成时代在315～303Ma之间,为新疆西准噶尔地区晚古生代地球动力学背景及岩浆活动的深入研究,提供了时间方面的约束。There are large number of dark diorite porphyrite dykes emplaced in the Karamay pluton and its adjacent area, western Junggar, Xinjiang, NW China. They are considered to be formed by magma filling into the existing fractures, which can be briefly classified into three groups with different strikes. The LA-ICP-MS U-Pb dating for zircons from a diorite porphyrite dyke sample yields ^206pb/^238U age of 303. 1 ± 1.2Ma. The Ar-Ar plateau age and inverse isochron diagram age of amphiboles from the same sample, are 312. 1±2. 8Ma（ 1120 - 1400℃ ）and 313.6 ±6. 9Ma respectively. The zircon ^206pb/^238U age of host rock is determined, by LA-ICP- MS zircon U-Pb dating, as 319. 0 ±1.0Ma, and zircon ^206pb/^238U age of a granite porphyry vein is 315.3 ± 1.0Ma. These chronology data show that the formation of the dykes in this area is not Permian, but Late Carboniferous, and that before filling of those dykes, the granitic magma intrusion occurred in western Junggar area, resulting in Karamay pluton and granite porphyry veins. The above dating data of the dykes and the host rock imply that the fractures, filled by the dykes, occurred from 315Ma to 303Ma. This study gives the new temporal constraint for further research in both Late Paleozoie geodynamical environment and magmatic intrusion of western Junggar, Xiniiang, NW China.

关 键 词：岩墙 锆石LA-ICP-MS年代学 角闪石Ar-Ar年代学 克拉玛依岩体 西准噶尔 

分 类 号：P588.13[天文地球—岩石学] P597.3[天文地球—地质学]