湘南黄沙坪铜锡多金属矿床与隐伏花岗斑岩有关的矿化-蚀变分带模式

The mineralization and alteration zoning model related to the concealed granite porphyry of the Huangshaping Cu-Sn polymetallic deposit,Southern Hunan Province

【研究目的】黄沙坪铜锡多金属矿床是湘南地区岩浆热液成矿系统的典型矿床之一。为了深化研究该矿床成岩成矿机制、高效指导深部找矿勘查,需要揭示与隐伏花岗斑岩有关的多金属矿化-蚀变分带规律,构建深部矿化-蚀变空间分带模式。【研究方法】应用热液矿床的大比例尺蚀变岩相定位找矿预测方法,开展矿区内-136 m、-176 m、-256 m中段典型穿脉剖面的矿化蚀变测量和矿物岩石地球化学研究,剖析了矿化-蚀变的强弱变化、矿物共生组合及其空间分带特征,探讨了成矿元素、元素组合及其元素比值变化规律。【研究结果】构建了矿化-蚀变空间分带模式:从花岗斑岩体(内带)→接触带→围岩(外带),依次为钨钼(黄铁)矿化-硅化-绢云母化花岗斑岩带(Ⅰ)→磁铁(钨锡)矿化石榴石矽卡岩带(Ⅱ-1)→钨钼-磁黄铁矿化石榴石矽卡岩带(Ⅱ-2)→铅锌矿化结晶灰岩带(Ⅲ)→强方解石化灰岩带(Ⅳ)的分带规律,各带对应的主要矿物组合为:石英+(黄铁矿+绢云母)→磁铁矿+透辉石+硅灰石+绿帘石+绿泥石+(白钨矿+锡石+黄铁矿+石榴石)→白钨矿+辉钼矿+磁黄铁矿+(锡石+黄铜矿+黄铁矿+闪锌矿+方铅矿)+石榴石+符山石+透辉石+角闪石+萤石+绿帘石+绿泥石+(石英+方解石)→方铅矿+闪锌矿+(黄铁矿)+方解石+石英→方解石+石英。进一步揭示了各蚀变带矿化元素分布规律:W、Mo→Fe、W、Sn(Bi、Mo)→W、Sn、Bi、Mo(Cu)→Pb、Zn(W、Sn、Cu)→Pb、Zn、Ag的水平分带规律。【结论】黄沙坪铜锡多金属矿床以岩体为中心至两侧围岩矿化-蚀变分带规律明显,各带内特征矿物组合和矿化指示元素的变化规律对矿体的赋存空间具有明显的指示作用。

This paper is the result of mineral exploration engineering.[Objective]The Huangshaping Cu-Sn polymetallic deposit is one of the typical representatives of the magmatic hydrothermal metallogenic system in southern Hunan,China.In order to deepen the diagenetic and metallogenic mechanism of the deposit and efficiently guide the exploration of deep prospecting,it is necessary to reveal the polymetallic mineralization-alteration zone rule related to the concealed granite porphyry,and construct the deep mineralization-alteration spatial zoning model.[Methods]Applying the large-scale altered lithofacies location prospecting and prediction method for hydrothermal deposits,and the geochemical analysis of rock and mineral for tunnel sections in the typical levels of-136 m,-176 m and-256 m,the intensity change of mineralization-alteration,mineral paragenetic association and its spatial zoning characteristics were analyzed,and the transformation rules of ore-forming elements,element associations and element ratios were discussed.[Results]The current study constructed mineralization-alteration zoning model:from porphyry(internal zone)to contact zone to surrounding rock(outer zone)with scheelite-molybdenite(pyrite)mineralized-silicified-sericitized granite porphyry zone(Ⅰ)→magnetization(scheelite-cassiterite)mineralized garnet skarn zone(Ⅱ-1)→scheelite-molybdenite-pyrrhotite mineralized garnet skarn zone(Ⅱ-2)→lead-zinc mineralized crystalline limestone zone(Ⅲ)→strong calcitization limestone zone(Ⅳ).The main mineral assemblages of in the corresponding zones are:Quartz+(Pyrite+Sericite)→Magnetite+Diopside+Wollastonite+Epidote+Chlorite+(Scheelite+Cassiterite+Pyrite+Garnet)→Scheelite+Molybdenite+Pyrrhotite+(Cassiterite+Chalcopyrite+Pyrite+Sphalerite+Galena)+Garnet+Vesuvianite+Diopside+Hornblende+Fluorite+Epidote+Chlorite+(Quartz+Calcite)→Galena+Sphalerite+(Pyrite)+Calcite+Quartz→Calcite+Quartz.The distribution rule of mineralized elements in each alteration zone was revealed:W,Mo→Fe,W,Sn(Bi,Mo)→W,Sn,Bi,Mo(Cu)→Pb,Zn(W,Sn,Cu)→Pb,Zn,Ag.[Conclusions]The mineralization-alteration zoning rule of the deposit was obvious from the rock mass as the center to the surrounding rock on both sides.The transformation rules of characteristic mineral assemblage and mineralization indicator elements in each zone have an obvious indication of the occurrence position of the ore body.