东天山黄山东和黄山西铜镍硫化物矿床含矿超镁铁岩的成岩‒成矿作用机制:来自斜长石成分的约束  

Petrogenesis and Metallogenesis Mechanism of the Ore⁃Bearing Ultramafic Rocks from the Huangshandong and Huangshanxi Ni⁃Cu Sulfide Deposits,Eastern Tianshan:Constraints from Plagioclase Compositions

作　　者：石煜 王玉往[2] 王京彬 周国超 王海 Shi Yu;Wang Yuwang;Wang Jingbin;Zhou Guochao;Wang Hai(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China;Beijing Institute of Geology for Mineral Resources Co.Ltd.,Beijing 100012,China;Sino-Zijin Resources Ltd.,Beijing 100012,China;College of Resources and Environmental Engineering,Guizhou University,Guiyang 550025,China)

机构地区：[1]东华理工大学核资源与环境国家重点实验室,江西南昌330013 [2]北京矿产地质研究院有限责任公司,北京100012 [3]中色紫金地质勘查(北京)有限责任公司,北京100012 [4]贵州大学资源与环境工程学院,贵州贵阳550025

出　　处：《地球科学》2022年第9期3244-3257,共14页Earth Science

基　　金：国家重点研发计划项目(No.2017YFC0601204).

摘　　要：东天山黄山东和黄山西镁铁‒超镁铁岩是区域早二叠世大规模幔源岩浆作用的产物,赋存有两个大型岩浆铜镍硫化物矿床.黄山东和黄山西矿床的主要矿体均赋存于超镁铁岩中,其含矿超镁铁岩的成因机制研究对揭示区域铜镍硫化物成矿作用机制具有重要意义.本文对黄山东和黄山西含矿超镁铁岩进行了详细的电子背散射图像研究,发现其斜长石斑晶存在显著的不平衡结构,并系统进行了电子探针成分剖面分析.结果显示斜长石具有剧烈变化的成分环带,其中黄山东超镁铁岩斜长石An值介于48.6~75.6,黄山西含矿超镁铁岩斜长石An值介于44.9~79.2,表明两个矿床含矿超镁铁岩的母岩浆在侵位过程中发生过显著的成分变化.结合黄山东和黄山西镁铁‒超镁铁杂岩体地质特征,本文认为高分异镁铁质岩浆的加入导致了低分异超镁铁质岩浆成分发生显著变化,致使岩浆硫化物熔离,以及黄山东和黄山西大型铜镍硫化物矿床的形成.The Huangshandong and Huangshanxi mafic-ultramafic intrusions in East Tianshan are products of regional large scale Early Permian mantle-derived magmatism,and host two large scale Ni-Cu sulfide deposits.Major ore reserves of the Huangshandong and Huangshanxi deposits are hosted in the ultramafic rocks.Therefore,petrogenesis of their ore-bearing ultramafic rocks plays key role in understanding the matallogenesis of the regional Ni-Cu sulfide deposits.This study uses back scattered electron(BSE)images to observe the ore-bearing ultramafic rocks from Huangshandong and Huangshanxi deposits,and find out that plagioclase phenocrysts show significant disequilibrium.EMPA was used to analyze the chemical compositions and chemical profiles of the plagioclase phenocrysts.The An value of plagioclase from Huangshandong and Huangshanxi ore-bearing ultramafic rocks varies from 48.6 to 75.6 and 44.9 to 79.2,respectively,suggesting that the parental magma of the ore-bearing ultramafic rocks had experienced significant composition change during emplacement.Combined with geology of these two deposits,it is proposed that addition of high differentiated mafic magma into low differentiated ultramafic magma significantly changed parental magma composition,leading to sulfide segregation and formation of the Huangshandong and Huangshanxi large scale Ni-Cu sulfide deposits.

关 键 词：斜长石 铜镍硫化物矿床 镁铁‒超镁铁岩 黄山东 黄山西 东天山 矿床学 

分 类 号：P612[天文地球—矿床学]