安徽宣城荞麦山矿床成矿岩体及其暗色包体成因与成矿意义:锆石U-Pb年代学、地球化学、Sr-Nd-Hf-O同位素制约  

Origin and metallogenic significance of the ore-forming intrusion and its mafic microgranular enclaves in the Qiaomaishan deposit,Xuancheng City,Anhui Province:Geochronology,geochemistry,Sr-Nd-Hf-O isotopic constraints

作　　者：李跃 袁峰[1,2] 邓宇峰 李晓晖[1,2] 刘光贤 李贺[1,2] 陆三明 周宇章[4] LI Yue;YUAN Feng;DENG YuFeng;LI XiaoHui;LIU GuangXian;LI He;LU SanMing;ZHOU YuZhang(School of Resources and Environmental Engineering,Ore Deposit and Exploration Centre(ODEC),Hefei University of Technology,Hefei 230009,China;Anhui Province Engineering Research Center for Mineral Resources and Mine Environments,Hefei 230009,China;School of Earth Sciences,East China University of Technology,Nanchang 330013,China;Public Geological Survey Management Center of Anhui Province,Hefei 230091,China)

机构地区：[1]合肥工业大学资源与环境工程学院,合肥工业大学矿床成因与勘查技术研究中心(ODEC),合肥230009 [2]安徽省矿产资源与矿山环境工程技术研究中心,合肥230009 [3]东华理工大学地球科学学院,南昌330013 [4]安徽省公益性地质调查管理中心,合肥230091

出　　处：《岩石学报》2019年第12期3838-3862,共25页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41820104007、41702353、41872247、41672069);国家重点研发计划项目(2016YFC0600209、2016YFC0600206);安徽省国土资源科技项目(2016-K-4);中央高校基本科研业务费专项资金(JZ2018HGTB0249)联合资助

摘　　要：宣城矿集区是长江中下游成矿带内新提出的矿集区,近年来取得了重大的找矿突破,尤其是大型斑岩型铜金矿的发现使宣城矿集区逐渐成为研究热点。宣城矿集区一系列的斑岩-矽卡岩矿床均与早白垩世侵入体密切相关。荞麦山铜钨矿床是区内典型的矽卡岩矿床,矿床形成与花岗闪长斑岩密切相关,且花岗闪长斑岩发育较多的暗色包体。确定暗色包体的成因有助于深入理解含矿岩体的岩浆演化过程及成矿意义。本次工作以荞麦山矿床花岗闪长斑岩和暗色包体作为研究对象进行U-Pb同位素年代学、岩石及矿物地球化学、全岩Sr-Nd、锆石Hf-O同位素地球化学分析,探讨暗色包体及成矿岩体的源区、岩浆演化过程及其对成矿的意义。暗色包体的形成时代为141Ma(MSWD=0.8),(87Sr/86Sr)i值为0.7059~0.7069,εNd(t)值为-6.0^-9.2,εHf(t)值为-12.7^-5.8,δ18O值为5.8‰~7.7‰;寄主岩石形成时代为140Ma(MSWD=0.3),(87Sr/86Sr)i值为0.7061~0.7064,εNd(t)值为-8.7^-7.7,εHf(t)值为-12.1^-8.1,δ18O值为5.6‰~7.4‰。此外,暗色包体与寄主岩石主要氧化物含量与SiO2含量呈线性负相关趋势、微量元素特征相似和寄主岩石斜长石斑晶的不平衡结构及捕掳晶的发现指示荞麦山暗色包体为岩浆混合成因,花岗闪长斑岩为起源于富集地幔的岩浆与壳源岩浆混合成的母岩浆侵位而来,同时幔源岩浆和壳源岩浆的混合也分别提供了成矿金属元素铜和钨,最终形成了铜钨共生的荞麦山矿床。The Xuancheng ore district is a new ore district in the Middle and Lower Yangtze River Metallogenic Belt. Its significant process has been made in prospecting exploration in recent years;especially the discovery of the Chating large porphyry Cu-Au deposit making the Xuancheng ore district gradually attracted the attentive. The Early Cretaceous intrusions have intimate relationship with these porphyry-skarn deposits in the Xuancheng ore district. The Qiaomaishan Cu-W deposit is a typical skarn deposit in the Xuancheng ore district and the ore-bearing granodiorite porphyry contains many mafic microgranular enclaves( MMEs). We did geochronology,geochemistry,whole rock Sr-Nd and zircon Hf-O isotopic composition studies for the granodiorite porphyry and MMEs to discuss the magma sources,magma processes and its significance of mineralization. The results of MMEs( the weighted 206Pb/238U age is 141 Ma( MSWD = 0. 8),the(87Sr/86Sr)i values are 0. 7059 ~ 0. 7069,the εNd( t) values are -9. 2 ^-6. 0,the εHf( t) values are -12. 7 ^-5. 8,the δ18O values are 5. 8‰ ~ 7. 7‰) and host rocks( the weighted 206Pb/238U age is 140 Ma( MWSD = 0. 3),the(87Sr/86Sr)i values are 0. 7061 ~ 0. 7064,the εNd( t) values are -8. 7 ^-7. 7,the εHf( t) values are -12. 1 ^-8. 1,the δ18O values are 5. 6‰ ~ 7. 4‰),the major oxides content have linear negative correlation with SiO2 content,trace elements have similar characteristics,the disequilibrium structure of plagioclases and the captured plagioclase from host rocks show that the MMEs are the result of magma mixing. The parental magma of granodiorite porphyry was mixed by the magma from enriched mantle and crust.Moreover,the mantle-derived magma provided the ore-forming material of copper while the crust-derived magma provided the tungsten which formed the Qiaomaishan Cu-W symbiotic deposit.

关 键 词：花岗闪长斑岩 暗色包体 岩浆混合作用 荞麦山矽卡岩铜钨矿床 

分 类 号：P588.13[天文地球—岩石学] P597.2[天文地球—地质学]