东昆仑东段清水泉辉长岩体LA-ICP-MS锆石U-Pb年龄、地球化学特征及其构造意义  

LA-ICP-MS zircon U-Pb dating and geochemical characteristics of gabbro in Qingshuiquan, east section of East Kunlun, and its tectonic significance

作　　者：桑继镇 裴先治[1,2] 李瑞保[1,2] 刘成军[1] 陈有炘[1] 李佐臣[1,2] 陈国超[1] 杨森[1] 王旭斌[1] 陈功[1] 邓文兵 

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]长安大学西部矿产资源与地质工程教育部重点实验室,陕西西安710054

出　　处：《地质通报》2016年第5期700-710,共11页Geological Bulletin of China

基　　金：国家自然科学基金项目(批准号:41472191;41502191;41172186);高等学校博士学科点专项科研基金项目(编号:20110205110004);中央高校基本科研业务费专项资金项目(编号:CHD2011TD020;2013G1271091;2013G1271092;310827161002;310827161006)

摘　　要：清水泉辉长岩体位于东昆仑中缝合带清水泉蛇绿岩北侧,主要岩性为角闪辉长岩。该岩体的LA-ICP-MS锆石U-Pb测年结果为452.1±5Ma,形成时代为晚奥陶世。辉长岩体样品SiO_2含量为43.89%~45.99%,Na_2O含量为1.30%~2.32%,K_2O含量为0.68%~1.39%,P_2O_5含量为0.26%~0.40%,TiO_2含量较低,为0.74%~0.95%,MgO含量为5.72%~6.54%,Mg~#值较低,为53~54。岩石地球化学特征显示,该岩体属于拉斑玄武岩系列,稀土元素表现出轻稀土元素富集、重稀土元素亏损的特点,微量元素以富集大离子亲石元素（Cs、Rb、Ba等,尤其以Ba的正异常最为突出）、亏损高场强元素（Nb、Ta、Ti、Zr、Hf）为特征。微量元素构造判别显示,其形成于活动陆缘岛弧构造环境。结合区域地质资料研究表明,清水泉辉长岩体可能形成于以清水泉蛇绿岩为代表的东昆仑中弧后有限洋盆向北俯冲的初始阶段。Located in central Eastern Kunlun suture zone on the northern side of Qingshuiquan ophiolite, the Qingshuiquan gabbro consists mainly of hornblende gabbros. The LA-ICP-MS zircon U-Pb age is 452.1±5Ma, suggesting the formation of gabbro in LateOrdovician. The gabbro samples have 43.89%~45.99% SiO_2, 1.30%~2.32% Na_2O, 0.68%~1.39% K_2O, and 5.72%~6.54% MgO,with low P_2O_5（0.26%~0.40%）, TiO_2（0.74%~0.95%） and Mg~#（53~54）. The geochemical characteristics indicate that the gabbro belongs to tholeiitic rocks; REE patterns show that the rocks are enriched in LREE and depleted in HREE; the trace elements are characterized by enrichment of LILE（Cs,Rb,Ba,especially positive anomaly of Ba） and obvious depletion of HFSE（Nb,Ta,Ti,Zr and Hf）. Tectonic discrimination diagrams indicate that the gabbro formed in an island arc setting of active continental margin. Combinedwith regional studies, the authors hold that Qingshuiquan gabbro rocks might have formed at the initial stage of the northward subduction of Central Eastern Kunlun back-arc limited ocean, represented by the Qingshuiquan ophiolite.

关 键 词：清水泉 辉长岩体 岛弧 LA-ICP-MS锆石U-PB测年 晚奥陶世 

分 类 号：P534.42[天文地球—古生物学与地层学] P597.3[天文地球—地质学]