青藏高原祁漫塔格古生代以来主要岩浆活动及其意义

发布时间：2018-12-14 02:20

【摘要】：采用LA-ICP-MS方法对青藏高原祁漫塔格山西部枯草沟地区花岗岩和闪长岩进行锆石U-Pb测年,获得405.7±1.3Ma、420.8±1.6Ma、423.9±1.5Ma和421.0±1.7Ma四个年龄,属于晚志留世—早泥盆世。这些锆石具有高Th/U值,是典型的岩浆锆石,其结晶年龄代表岩石形成年龄。综合统计目前已有锆石U-Pb年龄数据表明,该地区主要存在2期岩浆活动:350~500Ma和200~350Ma,分别对应早古生代和晚古生代—早中生代。祁漫塔格早古生代岩浆活动年龄数量占统计的60%以上,为主要岩浆活动期,主要分布于祁漫塔格北部和西部。东昆仑晚古生代—早中生代的岩浆约占古生代以来岩浆总量的77%以上,为东昆仑主要岩浆活动期。祁漫塔格晚古生代—早中生代岩浆活动主要分布于其东南部,靠近东昆仑山,暗示其可能受东昆仑主要岩浆活动的影响。以上结果暗示,早古生代期间祁漫塔格洋的活动性强于东昆仑洋的活动性,祁漫塔格和东昆仑可能自晚古生代以来才逐步形成统一的造山带。
[Abstract]:Zircon U-Pb dating of granites and diorites in the Xiucaogou area, Shanxi Qimantag, Qinghai-Xizang Plateau was carried out by using LA-ICP-MS method. The ages of 405.7 卤1.3 Ma, 420.8 卤1.6 Ma, 423.9 卤1.5Ma and 421.0 卤1.7Ma were obtained. Belongs to the late Silurian-early Devonian. The zircon is a typical magmatic zircon with high Th/U value and its crystallization age represents the age of rock formation. The comprehensive statistics of zircon U-Pb dating show that there are two magmatic activities in this area: 350~500Ma and 2000.The magmatic activity corresponds to the early Paleozoic and the late Paleozoic to early Mesozoic, respectively. The age of early Paleozoic magmatic activity in Qimantage is more than 60% of the total, which is the main period of magmatic activity and mainly distributed in the north and west of Qimantage. The magma from late Paleozoic to early Mesozoic in East Kunlun is more than 77% of the total magma since Paleozoic, which is the main magmatic activity period in East Kunlun. The late Paleozoic to early Mesozoic magmatic activities in Qimantage are mainly distributed in the southeastern part of Qimantage, near the East Kunlun Mountains, suggesting that they may be affected by the main magmatic activities in East Kunlun. These results suggest that the activity of Qimantag Ocean was stronger than that of East Kunlun Ocean during the early Paleozoic, and Qimantage and East Kunlun probably formed a unified orogenic belt only gradually since the late Paleozoic.
【作者单位】：中国地质科学院地质研究所/国土资源部大陆动力学重点实验室;中国地质调查局大陆动力学研究中心;中国地质科学院地质力学研究所/中国地质科学院古地磁重点实验室;中国煤炭工业协会咨询中心;
【基金】：中国地质调查局项目(编号:DD20160022-02、12120115027001、12120114022901)
【分类号】：P534.4;P588.1

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