江南造山带东段地区三堡铅锌矿床花岗闪长斑岩的形成年代、地球化学特征及成矿指示  

Geochronology,Geochemical Characteristics,and Mineralization Significance of the Granodiorite Porphyry in the Sanbao Lead-zinc Deposit,Eastern Jiangnan Orogenic

作　　者：侯舒雅 张达玉[1] 张飞 雷行行 胡梦祥 翁望飞[2] Noel C White HOU Shuya;ZHANG Dayu;ZHANG Fei;LEI Hanghang;HU Mengxiang;WENG Wangfei;Noel C White(School of Resources and Environmental Engineering,Hefei University of Technology,Hefei 230009,Anhui,China;332 Geological Team,Anhui Bureau of Geology and Mineral Exploration,Huangshan 245000,Anhui,China)

机构地区：[1]合肥工业大学资源与环境工程学院,安徽合肥230009 [2]安徽省地质矿产勘查局332地质队,安徽黄山245000

出　　处：《大地构造与成矿学》2024年第4期879-898,共20页Geotectonica et Metallogenia

基　　金：安徽省公益性地质工作项目(2021-g-2-11);安徽省自然资源厅科技项目(2023-K-17、2021-K-9);国家自然科学基金项目(4192076)联合资助。

摘　　要：三堡铅锌矿床位于江南古陆北部,其成矿作用与花岗闪长斑岩密切相关。本文在地质特征和岩相学认识基础上,对与三堡铅锌矿床相关的花岗闪长斑岩开展了锆石LA-ICP-MS U-Pb同位素年代学、全岩地球化学和Sr-Nd同位素分析。结果显示,三堡花岗闪长斑岩锆石U-Pb年龄为154.8±1.8 Ma,为晚侏罗世。三堡花岗闪长斑岩SiO_(2)含量为63.75%~67.47%,Na_(2)O+K_(2)O为3.92%~7.34%,为高钾钙碱性、准铝质‒弱过铝质的I型花岗岩;且样品富集轻稀土元素(LREE/HREE=10.50~11.29)、显示弱负Eu异常(δEu=0.68~0.77),富集Rb、Th、U、K等大离子亲石元素,亏损P、Ti、Yb等高场强元素。花岗闪长斑岩(^(87)Sr/^(86)Sr)i值为0.71028~0.71320,ε_(Nd)(t)值在-6.57~-5.55之间。岩石地球化学特征显示,三堡花岗闪长斑岩熔体来自壳幔混合源区,上升过程中经历了显著的结晶分异作用。结合区域资料对比显示,三堡铅锌矿床为江南造山带东段地区燕山期早阶段(177~153 Ma)铜铅锌成矿作用的重要组成部分,该花岗闪长斑岩所呈现的中低结晶温度、较低分异程度、较高氧逸度与水含量是该区中酸性岩浆岩的成矿专属性指标。The Sanbao lead-zinc deposit is located in the northern part of the Eastern Jiangnan Orogenic Belt(EJOB)and is genetically related to a granodiorite porphyry.Based on detailed geological and petrologic observations,this paper presents zircon LA-ICP-MS U-Pb isotope chronology,whole-rock geochemistry,and Sr-Nd isotopes of the granodiorite porphyry in the Sanbao lead-zinc deposit.Zircon U-Pb dating yielded an age of 154.8±1.8 Ma for the granodiorite porphyry,corresponding to the Late Jurassic.The Sanbao granodiorite porphyry has SiO_(2) contents ranging from 63.75% to 67.47% and Na_(2)O+K_(2)O contents ranging from 3.92% to 7.34%.It is characterized by metaluminous to weak peraluminous and high K calc-alkaline I-type granite.The granodiorite porphyry is characterized by enriched LREEs(LREE/HREE=10.50-11.29)with weak negative Eu anomalies(δEu=0.68-0.77),high large ionic lithophile element contents(LILEs,e.g.,in Rb,Th,U and K),and depleted high field strength elements(HFSEs,e.g.,P,Ti and Yb),with(^(87)Sr/^(86)Sr)i and ε_(Nd)(t)values in the ranges of 0.71028-0.71320 and-6.57 to-5.55,respectively.These geochemical characteristics indicate that the Sanbao granodiorite porphyry was derived from crust-mantle mixing source,and underwent significant fractional crystallization.The Sanbao lead-zinc deposit is an important part of early-stage Yanshannian Cu-Pb-Zn(177-153 Ma)magmatism and mineralization.Compared with the regional Yanshanian ore-forming intrusions in the EJOB,we propose that the lower magmatic temperature and differentiation index(DI)and higher oxygen fugacity(f_(O_(2)))and water content of the granodiorite porphyry are beneficial indicators for copper-lead-zinc mineralization in the EJOB.

关 键 词：花岗闪长斑岩 成岩年代 岩石成因 成矿专属性 江南造山带东段地区 

分 类 号：P595[天文地球—地球化学] P597[天文地球—地质学]