东天山寨北山铜矿区钠质火山岩年代学、地球化学特征及其成因  

Geochronology, geochemistry and genesis of Na-rich volcanic rocks of the Zhaibeishan copper deposit in Eastern Tianshan Mountains

作　　者：孙志远[1,2] 龙灵利[2] 王玉往[2] 罗照华[1] 赵路通[2,3] 解洪晶[2] SUN Zhiyuan;LONG Lingli;WANG Yuwang;LUO Zhaohua;ZHAO Lutong;XIE Hongjing(School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;Beijing Institute of Geology for Mineral Resources,Beijing 100012,China;;Faculty of Land Resources Engineering,Kunming University of Science and Technology,Kunming 650093,Yunnan,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]北京矿产地质研究院,北京100012 [3]昆明理工大学国土资源工程学院,昆明650093

出　　处：《中国地质》2018年第5期943-962,共20页Geology in China

基　　金：国家重点基础发展研究计划项目(2014CB440803);国家自然科学基金项目(41202046)联合资助

摘　　要：寨北山矿区海相火山岩为一套富钠的玄武安山玢岩、安山岩、英安岩、流纹岩组合,属于钙碱性系列岩石,具有低MgO(0.51%~5.93%,平均2.54%)、FeO(0.54%~6.39%,平均2.84%)和钛(TiO_2=0.09%~1.10%,平均0.58%),富铝(Al_2O_3=12.23%~17.75%,平均15.20%,A/CNK=0.79~1.42,平均1.11)以及富钠(Na_2O/K_2O平均为7.30)、富水的特征。火山岩中斜长石主要为钠长石,少量更长石。轻、重稀土分馏较明显((LREE/HREE)N=3.68~9.00),微量元素显示大离子亲石元素(如Th、U、Rb)、轻稀土的富集和高场强元素(如Nb、Ta、Ti、P)相对亏损的特征。获得矿区雅满苏组钠质玄武安山玢岩SHRIMP锆石U-Pb谐和年龄为(337.6±3.3) Ma,为早石炭世火山活动的产物。火山岩岩石学及地球化学特征表明研究区钠质火山岩可能形成于俯冲带近大陆方向的岛弧构造环境,是早石炭世洋壳俯冲熔融产生的岩浆在海底喷发过程中与海水相互反应后,经低变质相作用产生的。成矿元素在钠长石化过程中可能被淋滤出来进入含矿热液,后期在适当的温压等条件下沉淀形成本区的矿床。Marine Na-rich volcanic rocks of Yamansu Formation belong to calc-alkaline series and are dominated by basaltic andesitic porphyrite,andesite,dacite and rhyolite.These volcanic rocks are characterized by low MgO(0.51%-5.93%,averaging 2.54%),FeO(0.54%-6.39%,averaging 2.84%)and TiO2(0.09%-1.10%,averaging 0.58%)values,high Al2O3(12.23%-17.75%,averaging 15.2%;A/CNK=0.79-1.42,averaging 1.11),and Na2O(Na2O/K2O 7.30 on average).A majority of plagioclases in the Narich volcanic rocks consist of albite with less oligoclase.Chondrite-normalized REE patterns show the fractionation between LREE and HREE((LREE/HREE)N=3.68-9.00).The volcanic rocks are also rich in LILE(Th,U,Rb)and depleted in Nb,Ta,Sr,Ti,P.The SHRIMP zircon U-Pb dating yielded(337.6±3.3)Ma.Based on a comparative study of geochemical characteristics and inherited zircon age,the authors hold that Yamansu Na-rich volcanic rocks were formed in an island arc setting with continental basement and were the products of reaction between erupted magma and convective seawater during the subduction of oceanic plate in Early Carboniferous.

关 键 词：东天山 寨北山铜矿 雅满苏组 钠质火山岩 SHRIMP锆石U-PB年龄 

分 类 号：P597.3[天文地球—地球化学] P595[天文地球—地质学]