中国地质2017，Vol.44Issue(3)：526-540,15.DOI:10.12029/gc20170310
东昆仑东段阿拉思木辉长岩锆石U-Pb年代学、地球化学特征及洋盆闭合时限界定
Zircon U-Pb geochronology, geochemistry of the Alasimu gabbro in eastern section of East Kunlun Mountains and the closing time of Paleo-ocean basin
摘要
Abstract
Late Paleozoic intermediate-acid granitoids are widely distributed in the East Section of East Kunlun, but the records of basic magmatism are very insufficient. Alasimu mafic rocks on the southern margin of the arc magmatic rock belt in northern East Kunlun Mountains was selected as the study objective so as to provide a new basis for the research on the Late Paleozoic magmatic evolution of the east section of East Kunlun Mountains. LA-ICP-MS zircon U-Pb analysis yielded the crystallization age of 241± 1Ma, suggesting that Alasimu Mafic rocks were formed in the Middle Triassic. All the rock samples are characterized by relatively low TiO2 (0.17%-0.37%, averagely 0.25%) and high Mg# (72.94%-77.32%, averagely 74.95%) and high Al2O3 (13.08%-23.20%, averagely 18.9%), enrichment of large ion lithophile elements (LILE:Sr, Rb, Ba), apparent depletion of high field strength elements (HFSE, Nb, Ta, Zr and Hf). MgO shows some correlation with Fe2O3T, TiO2, Ni and Co in the diagram of Harker, which reveals some degree of fractional crystallization of olivine and Ti-Fe oxide. Alasimu mafic rocks have similar chemical composition to island arc basalts, and they formed earlier than the collision and post-collision time of tectonic-magmatic activity. Combined with regional studies, the authors hold that Alasimu gabbro rocks ought to be the latest magmatism records in the East Kunlun region related to Middle Triassic Paleo Tethys oceanic crust subduction, which indicated that the tectonic transition from ocean subduction to collisional orogeny might have commenced in Middle Triassic.关键词
东昆仑造山带/辉长岩/岛弧/锆石U-Pb定年/中三叠世Key words
East Kunlun oroganic belt/gabbro/island arc/zircon U-Pb geochronology/Middle Triassic分类
天文与地球科学引用本文复制引用
张玉,彭思钟,裴先治,李瑞保,刘成军,陈有炘,李佐臣,王兴,胡晨光,颜全治..东昆仑东段阿拉思木辉长岩锆石U-Pb年代学、地球化学特征及洋盆闭合时限界定[J].中国地质,2017,44(3):526-540,15.基金项目
Supported by the National Science Foundation of China ( No. 41472191, 41502191, 41172186) （ No. 41472191, 41502191, 41172186）
the Special Fund for Basic Scientific Research of Central Colleges, Chang`an University (Nos. CHD2011TD020, 2013G1271091, 2013G1271092) （Nos. CHD2011TD020, 2013G1271091, 2013G1271092）
the Commonweal Geological Survey, the Aluminum Corporation of Chian and the Land-Resources Department of Qinghai Province (No. 200801).国家自然科学基金项目(41472191、41502191、41172186、310827161006)、中央高校基本科研业务费专项资金项目(CHD2011TD020、2013G1271091、2013G1271092)和青海省国土资源厅-中国铝业公司公益性区域地质矿产调查基金项目(中铝基金200801)联合资助. （No. 200801）
