新疆东天山土屋斑岩铜矿床地球化学、年代学、Lu-Hf同位素及其地质意义  

Geochemistry,geochronology,Hf isotope,and geological significance of the Tuwu porphyry copper deposit in eastern Tianshan,Xinjiang

作　　者：王银宏[1] 薛春纪[1] 刘家军[1] 王建平[1] 杨俊弢 张方方[1] 赵泽南 赵云江 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [2]新疆地质矿产开发局第一地质大队,昌吉831100

出　　处：《岩石学报》2014年第11期3383-3399,共17页Acta Petrologica Sinica

基　　金：中国地质调查局综合研究项目(1212011085471;1212011220923);高等学校博士学科点专项科研基金(20130022110001);高等学校学科创新引智计划(B07011);国家自然科学基金项目(40973035);中国地质大学(北京)基本科研业务费专项资金资助项目优秀导师基金联合资助

摘　　要：新疆东天山地区岩浆岩的岩石成因和地球动力学背景备受关注。本文获得的东天山土屋斑岩铜矿床SIMS锆石U-Pb定年、全岩元素地球化学和Lu-Hf同位素数据,以对这一问题进行约束。土屋斑岩铜矿床位于新疆东天山造山带晚古生代大南湖-头苏泉岛弧带中,赋矿地层为下石炭统企鹅山群,赋矿围岩主要为安山岩和闪长玢岩,含矿岩石主要为英云闪长岩。本文SIMS锆石U-Pb定年结果表明,土屋地区含矿岩体大约侵位于335Ma,土屋斑岩铜矿床成矿时代与成岩时代基本一致或稍晚。地球化学数据显示安山岩和闪长玢岩具有同源性及岛弧火山岩的特点,英云闪长岩具有埃达克质岩石的特征。土屋英云闪长岩具不均一的锆石εHf(t)正值(+6.3^+16.1),表明其可能来源于俯冲板片的部分熔融。土屋斑岩铜矿床含矿岩体很可能是在早石炭世北天山洋板块北向俯冲的地球动力学背景下,大洋板片发生部分熔融形成埃达克质岩浆,在熔融过程中同时析出金属,随埃达克质岩浆一起上升,并与地幔橄榄岩发生交代作用,在岩体顶部富集成矿。The petrogenesis and geodynamic setting of magmatic rocks in eastern Tianshan are attracting increasing attention. This study explores these issues by providing SIMS zircon U-Pb dating,whole-rock geochemical,and Lu-Hf isotope data of the Tuwu porphyry copper deposit of eastern Tianshan,Xinjiang. The Tuwu porphyry copper deposit is located in the middle of the Late Paleozoic Dananhu-Tousuquan arc belt in the eastern Tianshan tectonic belt. The Carboniferous Qieshan Group is the main ore-hosting stratum.The andesite and dioritic porphyrite are the ore-hosting rocks,while the tonalitic rocks are the ore-bearing rocks. SIMS zircon U-Pb dating data indicate that the ore-bearing rocks occurred around 335 Ma,and that mineralization of the Tuwu porphyry copper deposit occurred during the same period as that of the rock formation in the region or slightly later. The andesite and dioritic porphyrite are island arc volcanic rocks and formed by the same magmatism. However,the mineralized tonalitic rocks have adakitic characteristics. In situ Hf isotopic analyses of zircons yielded positive initial εHf（ t） values ranging from ＋ 6. 3 to ＋ 16. 1,indicating the ore-bearing rocks were most likely derived from partial melting of a subducted oceanic slab. Therefore,we suppose that the North Tianshan oceanic crust subducted northward beneath the Dananhu-Tousuquan arc belt during the Early Carboniferous,and the Tuwu adakitic magmas were derived from partial melting of the subducted oceanic slab,hybridized subsequently by peridotite in the mantle wedge. During the adakitic magmas ascent,large amounts of metallogenetic elements were released,and accumulated further on the top of the rock bodies.

关 键 词：土屋斑岩铜矿床 SIMS锆石U-Pb定年 地球化学 LU-HF同位素 东天山 

分 类 号：P597.3[天文地球—地球化学] P618.41[天文地球—地质学]