云南武定迤纳厂铁-铜-金-稀土矿床成矿物质来源——来自矿床地质与S、Pb、H、O同位素的制约

Sources of the ore-forming materials for the Yinachang Fe-Cu-Au-REE deposit,Wuding, Yunnan Province: Constraints from the ore geology and the S, Pb, H, O isotope geochemistry

武定迤纳厂铁铜金稀土矿位于我国云南省中部,扬子板块西缘,康滇地轴云南段。根据矿物组合、围岩蚀变和矿化特征等方面的差异,可将其蚀变矿物组合划分为铁稀土长石硅酸盐组合和铜金石英碳酸盐组合两类,前者发生在矿化中前期,后者发生于矿化后期。铁铜稀土长石硅酸盐组合又可划分为磁铁矿钠长石稀土组合和黄铜矿钾长石石榴子石黑云母组合。分别对黄铜矿钾长石石榴子石黑云母组合中的黄铜矿、萤石,铜金石英碳酸盐组合中的黄铜矿、萤石、石英、方解石开展了S、Pb、H、O同位素的示踪研究。两组黄铜矿的δ34SCDT(‰)值变化范围为-0.44‰^+4.07‰,集中于0值附近,说明其具有单一岩浆来源。后一组黄铜矿单矿物的δ34SCDT(‰)值稍高于前一组合。第一组黄铜矿的Pb同位素组成较为均一,206Pb/204Pb比值范围为37.684~51.112,207Pb/204Pb比值范围为16.939~17.875,208Pb/204Pb比值范围为40.116~41.984,表明其来源单一;而第二组黄铜矿的Pb同位素组成则相对分散且具线性趋势,206Pb/204Pb比值范围为19.523~356.740,207Pb/204Pb比值范围为15.853~41.182,208Pb/204Pb比值范围为39.411~42.010,表明其为混合来源。前一组合中的萤石单矿物δ18OV-SMOW值介于+9.30‰^+10.80‰之间,δDV-SMOW值介于-63.20‰^-80.20‰之间,表明其更具岩浆水性质;后一组合中的石英单矿物δ18OV-SMOW值介于+15.20‰^+18.10‰之间,δDV-SMOW值介于-47.70‰^-91.20‰之间;方解石单矿物δ18OV-SMOW值介于+17.00‰^+19.60‰之间,δDV-SMOW值介于-66.10‰^-98.20‰之间,表明其更具有变质水的特征。

The Yinachang Fe-Cu-Au-REE deposit is located in the middle of Yunnan Province along the southern part of Kangdian axis and at the southwest edge of the Yangtze block. According to differences in mineral association, ore structure, texture and wall rock alterations, two mineral assemblages can be recognized, i. e., Fe-CuREE-feldspar-silicate assemblage of pre-dominant mineralization stage and Cu-Au-quartz-carbonate assemblage of post-mineralization stage, and the Fe-REE-feldspar-silicate assemblage can be further divided into magnetitealbite-REE subassemblage and chalcopyrite-K feldspar-garnet-biotite subassemblage. S, Pb, H, O isotopic researches on chalcopyrite, fluorite, quartz and calcite of the chalcopyrite-K feldspar-garnet-biotite subassemblage and the Cu-Au-quartz-carbonate assemblage suggest that the metal and fluid sources of the chalcopyrite-K feldspar-garnet-biotite subassemblage were dominantly derived from magma, while the ore-forming materials of the Cu-Auquartz-carbonate assemblage had a complicated metal source, and its fluid was probably of metamorphic hydrothermal origin.