哈萨克斯坦麦卡因矿床火山岩地球化学、U-Pb年代学和Lu-Hf同位素及意义  

Geochemistry,U-Pb dating,Lu-Hf isotopic analysis and geological significance of volcanic rocks in Maikain deposit,Kazakhstan

作　　者：潘鸿迪[1] 申萍[2] 张林浩[3] SEITMURATOVA Eleonora JAKUPOVA Sholpan 

机构地区：[1]长安大学地球科学与资源学院,西安710052 [2]中国科学院地质与地球物理研究所、中国科学院矿产资源研究重点实验室,北京100029 [3]中国黄金集团资产管理有限公司,北京100011 [4]沙特巴耶夫地质研究所、地层实验室,阿拉木图050010

出　　处：《岩石学报》2015年第2期401-414,共14页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(U1303293;41390442;41272109);中国科学院重点部署项目(KJZD-EW-TZ-G07);国际科技交流与合作专项(2010DFB23390);国家“305”项目(2011BAB06B01)联合资助

摘　　要：麦卡因大型VMS型Au-Ag-Cu-Zn-Pb矿床位于中哈萨克斯坦西北部的Baidaulet-Akbastau地区。地质剖面测量和岩石薄片研究表明,麦卡因矿区发育中基性火山岩(玄武岩和安山岩)和次火山岩(辉绿-辉长岩和辉绿岩),矿化主要与安山岩有关。对矿区火山岩地球化学分析表明,矿区岩石分为两种类型:类型Ⅰ为拉斑-钙碱性系列中基性火山岩(玄武岩和安山岩)和次火山岩(辉绿-辉长岩和辉绿岩),岩石具平坦的稀土配分模式,亏损Nb和富集Th/Yb,显示俯冲特点;类型Ⅱ为钙碱性系列安山岩,具典型的右倾型稀土配分模式,亏损Nb和富集Th/Yb,指示其形成于岛弧环境。含矿岩石为类型Ⅱ安山岩。对类型Ⅱ安山岩进行了锆石Lu-Hf同位素和SIMS U-Pb年龄分析,结果表明,锆石εHf(t)为较高的正值(+4.28^+14.84),指示其是地幔物质部分熔融的产物,锆石SIMS U-Pb年龄为459.1±4.8Ma,指示其成岩年龄属于晚奥陶世。因此,哈萨克斯坦麦卡因大型VMS型矿床含矿火山岩为钙碱性系列安山岩,形成于晚奥陶世岛弧环境。对比研究认为,哈萨克斯坦早古生代波谢库尔-成吉思斑岩型-VMS型成矿带向东延伸到我国西准噶尔沙尔布提山,沙尔布提山具有形成VMS型矿床的岩浆条件和构造环境。The Maikain large-size VMS Au-Ag-Cu-Zn-Pb deposit is located in the Baidaulet-Akbastau area in Central Kazakhstan. On the basis of detailed field profiling and thin-section petrography, we identified the main rock types in the Maikain area which are basic-intermediate volcanic and subvolcanic rocks. The mineralization is associated with intermediate volcanic rock. Based on our new geochemistry, two types are recognized： （1） Type I is tholeiitic to calc-alkaline basalts, andesites and gabbro-diabase and diabase, with REE patterns that are fiat, and with a negative Nb -~nomaly and Th/Yb enrichment, indicating that they were generated above a subduction zone; （2） Type I1 is ealc-alkaline andesite, which is strongly enriched in LREE with a negative Nb anomaly and Th/Yb enrichment, suggesting generation in a normal island-are setting. Type I1 andesite is the host rock. The zircon Ln-I-lf isotopic composition show that the zircon 8H^（t） of Type II lava range from ＋4. 28 to ＋ 14. 84, suggesting that these melts were derived from mantle wedge above a subduction zone. The SIMS zircon U-Pb dating of Type I1 lava yields Late Ordovician age （459. 1 ＋4. 8Ma）. Therefore, the host rocks of the Maikain large-size VMS deposit are ealc-alkaline andesites which formed in a normal island-arc setting in Late Ordovician. We propose that the Sharburti Mountains are the eastern extension of the Boshchekul-Chingiz porphyry-VMS ore belt of Kazakhstan into China. The Sharburti Mountains in the northern West Junggar have the magma condition and tectonic setting for VMS deposit.

关 键 词：岩石地球化学 锆石U-PB年龄 锆石Lu-Hf同位素 VMS型矿床 麦卡因 哈萨克斯坦 

分 类 号：P588.13[天文地球—岩石学] P588.14[天文地球—地质学]