东昆仑夏日哈木闪长玢岩成因及动力学背景:年代学、地球化学及Hf同位素约束  

STUDY OF GENESIS AND GEODYNAMIC SETTING OF DIORITE- PORPHYRITE IN XIARIHAMU AREA:CONSTRAINTS FROM GEOCHRONOLOGY,GEOCHEMISTRY AND HF ISOTOPIC DATA

作　　者：鲁海峰 陈静 余福承[3] 徐贝贝[3] 焦和 Lu Haifeng;Chen Jing;Yu Fucheng;Xu Beibei;Jiao He(The Qaidam Comprehensive Ggeology and Mineral Resources Exploration Institute of Qinghai Province,Key Laboratory of Salt Lake Resources Exploration and Research,Qaidam basin,Qinghai province,Xining,Qinghai 816099,China;Qinghai Normal University,School of Geographic Sciences,Xining,Qinghai 810000,China;Qinghai Geological Survey Institue,The northern Qinghai-Tibet Plateau Geological Processes and Mineral Resources Laboratory,Xining,Qinghai 810012,China)

机构地区：[1]青海省柴达木综合地质矿产勘查院,青海省柴达木盆地盐湖资源勘探研究重点实验室,青海西宁816099 [2]青海师范大学地理科学学院,青海西宁810000 [3]青海省地质调查院,青藏高原北部地质过程与矿产资源重点实验室,青海西宁810012

出　　处：《矿物岩石》2019年第4期61-68,共8页Mineralogy and Petrology

基　　金：国家自然科学基金(41862011;41762006);中国科学院“西部之光”人才培养引进计划的成果

摘　　要：夏日哈木矿区I号含矿杂岩体出露有多条中基性岩脉,对其中的含矿闪长玢岩脉进行了锆石LA-ICP-MS定年,结果表明岩脉的侵位时间为441.1±2.5 Ma。岩石地球化学分析表明该闪长玢岩具有富钠(K2O/Na2O=0.49~0.60)、准铝质(A/CNK=0.87~0.95,平均0.913)、LILE富集、HFSE相对亏损以及Nb,Ta和Ti负异常的特征。176 Hf/177 Hf为0.282360~0.282709,εHf(t)为-4.49~6.97,多集中在0~4之间,揭示其具有幔源组份的特征,一阶段Hf模式年龄变化于781~1234 Ma之间,平均0.98 Ga,表明源区物质可能经历过Grenville期构造-岩浆事件。岩石地球化学和同位素特征表明该闪长玢岩岩浆源区为俯冲洋壳环境形成的壳-幔混合岩浆,地壳物质可能参与了部分熔融。地球动力学背景分析结合区域近同期构造岩浆事件表明,晚奥陶世至早志留世早期东昆仑中西段仍在发生洋壳俯冲作用,东昆仑地区俯冲结束、碰撞造山开始的时限为早志留世到中志留世。Zircon LA-ICP-MS dating for the No.I ore-bearing diorite porphyrite veins in the Xiarihamu mining area yields an emplacement age of 441.1± 2.5 Ma.Geochemical analysis showed that the diorite was rich in sodium(K2O/Na2O=0.49 to 0.60),quasi-aluminum(A/CNK=0.87 to 0.95,average 0.913).LILE is enriched,with relative loss of HFSE and negative anomalies of Nb,Ta and Ti.The 176Hf/177 Hf is in the range of 0.282 360 to 0.282 709.Geochemical and isotopic characteristics of the rock indicated that the magma source of the diorite porphyrite was crust-mantle mixed,formed in oceanic crust subduction environment,and crustal materials may participate in partial melting.Comprehensive analysis of geodynamic background and contemporaneous regional tectonic and magmatic events showed that oceanic crust subduction still taken place in the late Ordovician to early Silurian in the western part of east Kunlun,and the time limit from subduction to collision orogenesis in East Kunlun is early to middle Silurian.

关 键 词：闪长玢岩 年代学 地球化学 锆石HF同位素 夏日哈木 东昆仑 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]