长江中下游成矿带龙角山矽卡岩钨矿床成矿作用过程——来自白钨矿和石榴子石主微量元素的证据  

Mineralization process in Longjiaoshan skarn tungsten deposit of Middle-Lower Yangtze River Metallogenic Belt: Constraints from in situ major and trace element analysis of garnet and scheelite

作　　者：聂利青 周涛发[2] 蔡国军 孙孝峰 宋玉龙 蔡毅 殷帅 王凤云 NIE LiQing;ZHOU TaoFa;CAI GuoJun;SUN XiaoFeng;SONG YuLong;CAI Yi;YIN Shuai;WANG FengYun(Key Laboratory of Intelligent Underground Detection Technology,School of Civil Engineering,Anhui Jianzhu University,Hefei 230601,Anhui,China;School of Resource and Environmental Engineering,Hefei University of Technology,Hefei 230009,Anhui,China;No.1 Geological Party of Hubei Geological Bureau,Daye 435000,Hubei,China)

机构地区：[1]安徽建筑大学土木工程学院智能地下探测技术重点试验室,安徽合肥230601 [2]合肥工业大学资源与环境工程学院,安徽合肥230009 [3]湖北省地质局第一地质大队,湖北大冶435000

出　　处：《矿床地质》2022年第1期69-90,共22页Mineral Deposits

基　　金：安徽省教育厅高校科学研究项目(编号:KJ2021ZD0069);国家自然科学基金项目(编号:91962218)联合资助。

摘　　要：白钨矿和石榴子石的原位微量元素特征能提供成矿流体的演化信息。长江中下游成矿带鄂东南矿集区龙角山矿床是近年发现的大型矽卡岩钨矿床,为区域找矿勘查和成科学研究提供了新的方向。龙角山矿床的流体演化和矿床成因亟待开展系统研究。文章在详细的野外工作和前人研究基础上,通过对矿床中矽卡岩阶段、退蚀变阶段和石英硫化物阶段的白钨矿和石榴子石进行原位主、微量分析,厘定了矿床成矿过程的环境和矿质沉淀机制。龙角山矿床矽卡岩阶段的红棕色石榴子石(Grt-1)矽卡岩、黄绿色石榴子石(Grt-2)-辉石矽卡岩和脉状石榴子石(Grt-3)-硅灰石矽卡岩中石榴子石成分分别为Adr_(30.6-84.1)Gro_(13.9-50.7)Pyr_(1.5-30.3)、Adr_(38.3-100)Gro_(0.0-39.4)Pyr_(0.0-22.4)和Adr_(75.3-100.0)Gro_(0.0-13.9)Pyr_(0.0-12.7),且富集大离子亲石元素,亏损高场强元素,具有富集轻稀土元素、亏损重稀土元素、铕正异常的特征。龙角山矿床矽卡岩阶段石榴子石U含量逐渐降低,且与钙铁榴石的成分变化吻合,表明在矽卡岩阶段成矿流体氧逸度逐渐升高;退蚀变阶段到石英-硫化物阶段白钨矿Mo元素含量先升高后降低,对应的氧逸度先增加后降低,显示了成矿过程复杂的脉冲式的氧逸度变化特征。龙角山矿床退蚀变阶段和石英-硫化物阶段的白钨矿显示铕负异常减弱、正异常增加的变化特征,表明成矿流体的p H值逐渐增加,而非在退蚀变阶段(主成矿阶段)达到峰值。因此,p H值不是影响白钨矿沉淀的主要因素。龙角山矿床矽卡岩阶段Grt-1稀土元素总量与Y存在正相关关系,Grt-2和Grt-3稀土元素总量与Y无正相关关系,且Grt-3富Fe元素,表明随着石榴子石的结晶由热液平衡状态向非平衡条件转变,水岩反应程度逐渐增加;退蚀变阶段(主成矿阶段)Sch-1的不规则生长环带比石英硫化物阶段Sch-2更发育,表明主成矿阶段水�In situ trace element characteristics of scheelite and garnet provide the evolution information of ore-forming fluids.The Longjiaoshan deposit is a large skarn tungsten deposit discovered in southeastern Edong orefield of the Middle-Lower Yangtze River Metallogenic Belt(MLYB).The fluid evolution history of the deposit has not been systematically studied,which restricts the prospecting work and theoretical research of the MLYB.Based on de‐tailed field work and previous studies,this study carried out in situ major and trace elements analyses of scheelite and garnet formed at different stages.The composition of red-brown garnet(Grt-1),yellow-green garnet(Grt-2)-pyroxene skarn and veined wollastonite-garnet(Grt-3)from the Longjiaoshan deposit is Adr_(30.6-84.1)Gro_(13.9-50.7)Pyr_(1.5-30.3)、Adr_(38.3-100)Gro_(0.0-39.4)Pyr_(0.0-22.4) and Adr_(75.3-100.0)Gro_(0.0-13.9)Pyr_(0.0-12.7),respectively.These three types of garnet are rich in LILEs and LREE,depleted in HFSEs and show positive Eu anomaly.The content of U element in garnet from the Longjiaoshan deposit gradually decreases,which is consistent with the composition change of andradite,indicating that the oxygen fugacity of ore-forming fluid gradually increases in the skarn stage.From retrograde to quartzsulfide stage the Mo content of scheelite increases and then decreases,as well as the oxygen fugacity increases and then decreases,indicating the complex pulse oxygen fugacity change characteristics in the mineralization process.The scheelite formed in the retrograde alteration stage and quartz sulfide stage shows decreasing in Eu negative anomaly but increasing in Eu positive anomaly,indicating that the p H value of ore-forming fluids gradually in‐creases.Therefore,p H value is not the main factor affecting scheelite precipitation.In the Skarn stage,there is a positive correlation between the total REE and Y of Grt-1,but there is no positive correlation between the total REE and Y of Grt-2 and Grt-3,and Grt-3 is rich in Fe,indicating that the degree of water-r

关 键 词：地质学 白钨矿 石榴子石 微量元素 成矿作用 龙角山矿床 

分 类 号：P618.67[天文地球—矿床学]