Metallogenic Processes:Evidencesfrom Zoning Patterns of Mineralization and alteration and fluid inclusion geochemistryin the Lehong Zn-Pb Deposit in Northeastern Yunnan, China

1 Introduction The large clusters of Zn-Pb deposits in northeastern Yunnan,located in the southwestern margin of the Yangtze Block,are an important part of the Sichuan-YunnanGuizhou Pb-Zn Poly-metallic Metallogenic Triangle

Trace Elements in Sphalerite from the Dadongla Zn-Pb Deposit, Western Hunan-Eastern Guizhou Zn-Pb Metallogenic Belt, South China

The western Hunan-eastern Guizhou Zn-Pb metallogenic belt is one of the important Zn-Pb mineralization regions in China.The Dadongla deposit,located in the northeast of Guizhou Province,is one of the typical Zn-Pb deposits in the region and has estimated resources more than 12 million metric tons(Mt)with an average grade of 4.11 wt%Zn+Pb.Its orebodies are hosted in the lower Cambrian Aoxi Formation dolomite,occurring as bedded,para-bedded in shape,and in conformity with the wall rock.The ore mineral assemblage is simple,dominated by sphalerite with minor pyrite and galena,and the gangue minerals are composed of dolomite,calcite with minor bitumen and barite.In view of the lack of geological and geochemical researches,the genesis of Zn-Pb ore is still unclear.Laser ablation-inductively coupled plasma mass spectrometry(LA-ICPMS)spot and mapping analyses were used to obtain sphalerite trace element chemistry in the Dadongla Zn-Pb deposit in Guizhou,China,aiming to constrain its ore genesis.The results show that sphalerite is characterized by the enrichment of Cd,Fe,Ge and Hg,corresponding with that of typical MVT deposits.Four zones were identified in the sphalerite crystal from Dadongla from the center to margin according to the color bands.in which the zone in the center,representing the early ore-stage sphalerite,is characterized by enrichment of Cd relatively,while the zone forming at late ore-stage is enriched in Ge and Hg relatively.The finding was controlled by differential leached metals content in ore-forming fluid from its source rock.Notably,critical element Ge trends to be enriched at the late ore-stage and follows a substitution of 2 Zn^2+(?)Ge^4++□(vacancy).Moreover,the calculated ore-forming temperature ranges from 79.9℃to 177.6℃by the empirical formula,which is similar to that of typical Mississippi Valley-type(MVT)deposits.Compared with the features of trace elements in sphalerite from different types of deposits,together with the geology,the Dadongla deposit belongs to an MVT Zn-Pb deposit.

Metallogenic Regularities and Deposit Type of Rich(Ge-Ag)-Zn-Pb Deposits in the Sichuan-Yunnan-Guizhou Triangle(SYGT)Area,China

1 Introduction The well-known1 Sichuan-Yunnan-Guizhou Triangle(SYGT)area of poly-metallic Zn-Pb deposits,southwest China is located at the south-western margin of the Yangtze Block in the transition area of the Tethys Belt and the Circum-Pacific Metallogenic Belt,and is composed of the Northeastern Yunnan。

Relationship Between Organic Matters and Zn-Pb Mineralization in the Giant Jinding Zn-Pb Deposit,SW China

The Jinding Zn-Pb deposit,Yunnan Province, southwestern China,represents the youngest,only continental sediment-hosted giant Zn-Pb deposit in the world.Various kinds of organic matters,such as the kerogen,light-and heavy-oil,hydrocarbon gas, bitumen of different occurrences and maturation,have been observed in recent underground and open pit mining.Oil-gas traces and oil-and methane-in-

Ore-controlling Regularitiesof Structureinthe Lehong Lead-zinc Deposit, Northeastern Yunnan

1 Introduction The Lehonglead-zincdeposit is a large-sized Pb-Zn depositnewly found in recent years in the Sichuan-Yunnan-Guizhou Lead-zinc Poly-metallic Mineralization Area,which occurrenceis

The mixing of multi-source fluids in the Wusihe Zn–Pb ore deposit in Sichuan Province, Southwestern China

The Sichuan-Yunnan-Guizhou(SYG)metallogenic province of southwest China is one of the most important Zn-Pb ore zones in China,with^200 Mt ZnPb ores at mean grades of 10 wt.%Zn and 5 wt.%Pb.The source and mechanism of the regional Zn-Pb mineralization remain controversial despite many investigations that have been conducted.The Wusihe Zn-Pb deposit is a representative large-scale Zn-Pb deposit in the northern SYG,which mainly occurs in the Dengying Formation and yields Zn-Pb resources of^3.7 Mt.In this paper,Zn and S isotopes,and Fe and Cd contents of sphalerite from the Wusihe deposit were investigated in an attempt to constrain the controls on Zn and S isotopic variations,the potential sources of ore-forming components,and the possible mineralization mechanisms.Both theδ66Zn andδ34S values in sphalerite from the Wusihe deposit increase systematically from the bottom to the top of the strata-bound orebodies.Such spatial evolution inδ66Zn andδ34S values of sphalerite can be attributed to isotopic Rayleigh fractionation during sphalerite precipitation with temperature variations.The strong correlations between the Zn-S isotopic compositions and Fe-Cd concentrations in sphalerite suggest that their variations were dominated by a similar mechanism.However,the Rayleigh fractionation mechanism cannot explain the spatial variations of Fe and Cd concentrations of sphalerite in this deposit.It is noted that the bottom and top sphalerites from the strata-bound orebodies document contrasting Zn and S isotopic compositions which correspond to the Zn and S isotopic characteristics of basement rocks and host rocks,respectively.Therefore,the mixing of two-source fluids with distinct Zn-S isotopic signatures was responsible for the spatial variations of Zn-S isotopic compositions of sphalerite from the Wusihe deposit.The fluids from basement rocks are characterized by relatively lighter Zn(~0.2‰)and S(~5‰)isotopic compositions while the fluids from host rocks are marked by relatively heavier Zn(~0.6‰)and S(~15‰)isotopic compositions.

Timing of the formation of the Baiyinnuo'er skarn Zn–Pb deposit,NE China:evidence from sulfide Rb–Sr dating

The Baiyinnuo’er deposit in northern China is located in the south section of the Great Xing’an Range,and it is the largest skarn Zn–Pb deposit in the region.Skarn and Zn–Pb orebodies mainly occur between the different units of the Permian Huanggangliang Formation,or within the contact zone between the intrusive rocks and the marble.Although Baiyinnuo’er has been well investigated previously,the timing of the Zn–Pb mineralization is still controversial,largely due to the lack of appropriate ore or alteration minerals that could be directly used for isotopic dating.In this study,we report the results of Rb–Sr isotopic analysis for sphalerite and pyrite samples from the Baiyinnuo’er orebodies,which yielded two isochron ages of 137.4±3.4 and 140.0±7.8 Ma,respectively,constraining the Zn–Pb mineralization time of the deposit as the Early Cretaceous.The data are also consistent with the age of the granitoids in the mining area,indicating a potential genetic relationship between the Early Cretaceous magmatism and mineralization.Many other intrusion-related hydrothermal deposits(including the two typical skarns,Huanggang and Haobugao)in the southern Great Xing’an Range also share similar mineralization ages(i.e.,140–130 Ma).Together,these data suggest an Early Cretaceous mineralization event in this region,and this largescale mineralization could be related to the regional tectonic regime transition from compression to extension as a result of the rollback of the subducted Paleo-Pacific plate.The initial87 Sr/86 Sr ratios of the sphalerite and pyrite samples are 0.70569 and 0.70616,respectively,implying that the ore-forming material could have a significant contribution from the mantle components.The current study shows that sulfide Rb–Sr dating could be used in deciphering the timing of skarn deposit formation.

滇东北乐红铅锌矿床构造成生发展及其控矿作用

乐红矿床是近些年来新发现的分布于川-滇-黔接壤区滇东北矿集区的大型铅锌矿床之一,矿体产出严格受构造控制。通过对矿区断裂、褶皱构造的系统解析,将断裂构造岩分为碎粒岩、碎斑岩、碎裂岩及构造角砾岩4类。通过不同方向断裂、褶皱构造筛分,反映矿区内存在4种构造组合,代表5期构造体系,分别对应于加里东期-前海西期、印支期-燕山早期、燕山中期、燕山晚期及喜马拉雅期。在此基础上,通过矿区褶皱和断裂控矿特征分析,认为NE向巧家-莲峰斜冲走滑断裂、乐马厂斜冲走滑断裂控制乐红矿区所在的巧家-金阳-永善构造带,NW向乐红断裂与成矿关系密切,是该矿床的导矿构造;乐红断裂和配套次级褶皱(包包上向斜和金家沟背斜)是矿床的配矿构造;构造活动引起的次级断裂破碎带、节理裂隙带及拖曳褶皱中层间断裂带是矿床的容矿构造。最终建立了乐红铅锌矿床构造控矿模式,为该矿床成因和找矿方向研究奠定了基础,也为黔西北矿集区铅锌找矿提供了重要启示。

滇东北乐红大型铅锌矿床流体包裹体地球化学

乐红铅锌矿床是扬子地块西南缘滇东北铅锌(银)多金属矿集区中的典型代表之一。通过对该矿床不同成矿阶段闪锌矿、石英、重晶石和方解石中流体包裹体岩相学、显微测温学和显微激光拉曼探针等测试,阐述了该矿床成矿流体性质和演化特征,并探讨了其成矿过程。研究发现,该矿床流体包裹体主要包括4类:Ⅰ类气相、Ⅱ类水溶液相(由Ⅱa型-富液相气液两相、Ⅱb型-富气相气液两相、Ⅱc型纯液相组成)、Ⅲ类含CO_2三相(V_(CO_2)+L_(CO)+L_(HO))及Ⅳ类含子矿物(L+V+S)包裹体。结果显示,重晶石阶段的均一温度为240.3~319.3℃,w(NaCl_(eq))为2.24~2%~1~20.73%,表现出中高温-中低盐度流体性质;白云石-黄铁矿-石英阶段具有中-高温(219.8~310.1℃),中盐度(w(NaCl_(eq))为7.02%~17.61%)特征;闪锌矿-方铅矿-黄铁矿阶段,包括S1闪锌矿具有中温(217.8~292.2℃)-中盐度(w(NaCl_(eq))为8.81%~16.71%)性质;S2闪锌矿具有中低温(180.2~241.3℃)-中盐度(w(NaCl_(eq))为7.73%~18.47%)性质;S3闪锌矿具有中低温(140.4~227.4℃)-中低等盐度(w(NaCl_(eq))为0.35%~19.21%)的流体性质,通过该阶段中含CO_2三相包裹体测试,估算成矿压力和成矿深度分别为45~74.9 MPa(平均58.2 MPa)、1.7~2.8 km。方解石阶段均一温度为165.3℃,中等盐度,w(NaCl_(eq))为11.28%,表现出低温-中等盐度的特征。不同成矿阶段的包裹体温度大致反映了该矿床成矿流体从早阶段至晚阶段,呈现中高温、中低盐度→中温、中等盐度→中低温、中低盐度的演化过程;早期高温-低盐度深部流体在热动力和构造应力驱动下大规模运移,受断裂构造影响发生减压沸腾作用,同时与大气降水发生混合,成矿流体物化性质陡变引起铅锌硫化物等的沉淀,并最终形成矿床。该研究为揭示矿床流体性质、演化及矿床成因提供了证据,深化了"构造-流体‘贯入’成矿"模型,亦对深化矿床成矿机制与指导找矿预测具有重要意义。

滇东北乐红铅锌矿床地质特征及找矿远景

乐红铅锌矿自20世纪50年代以来就有多家地勘单位先后进行过普查找矿,均以"层控"观点为指导没有进展而中途下马,90年代后期,云南第一地质大队以"构控"新思路开展新一轮找矿,获得突破性进展。在研究区域成矿地质背景、矿床地质特征及控矿地质因素的基础上,认为矿床为受断裂构造控制的热液充填交代型铅锌(银)矿床,并根据控矿断裂特征及成矿地质条件,指出乐红矿区及外围具有形成大型矿床的找矿远景,应该加强该区的地质找矿工作。

滇东北乐红—茂租地区铅锌银多金属矿“三位一体”成矿特征及模型

乐红—茂租地区是滇东北铅锌矿化集中区之一,其矿化普遍、构造特征明显,构造与成矿作用关系密切。典型矿床综合研究表明,该区铅锌矿床成矿地质体为断裂与碎裂白云岩组合,成矿结构面主要有岩性界面和构造成矿结构面,在此基础上建立该区地质成矿模型;并提出以东坪铅锌矿为中心,北西向找矿应注重震旦系灯影组白云岩与寒武系筇竹寺组粉砂质泥岩接触界面部位(茂租式);南东向找矿以产于震旦系灯影组白云岩中北西向断裂破碎带为重点区域(乐红式)。

滇东北乐红铅锌矿床铜矿物特征及地质意义

乐红铅锌矿矿床是川滇黔MVT型铅锌矿代表性铅锌矿床之一。近年来,矿床深部新发现了铜矿化体。本文通过镜下观察、扫描电镜和能谱分析。探讨铜矿与铅锌矿成因关系,以期揭示铜矿物质来源。证据表明,铜矿物与铅锌矿物具有明显的同期共生关系和相似的成矿物质来源,是同一成矿热液体系不同阶段演化的产物,对MVT型铅锌矿床铜矿物的研究具有参考意义。

滇东北乐红铅锌矿原生晕特征及深部找矿预测

鲁甸县乐红铅锌矿床位于滇东北矿集区,是新近发现的大型铅锌多金属沉积—热液改造型矿床。结合矿区地质背景、矿床成因、矿体特征及坑道岩石地球化学采样分析,系统详细地研究了乐红铅锌矿床深部的原生晕地球化学特征,结果表明:(1)矿体前缘元素和近矿元素为Ag、As、Sb、W、Hg、Zn、Mo,中程指示元素为Co、Ni,尾晕元素为Ba、Cu;(2)根据Grigorian原生晕分带原理,得出其轴向分带序列(由上至下各中段)为Ag-Zn-Mo-As-Hg-W-Co-Ni-Sb-Pb-Cu-Ba-Au-Sn,表明成矿过程存在多期矿化叠加;(3)采用多元统计的方法研究了各成矿元素及伴生元素的亲和性,并构建原生晕叠加模式、Ag/Cu、F1因子等深部找矿预测模型评价指标。综合原生晕各项特征,认为在1350中段以下应有隐伏矿体发育。此外,乐红矿床赋存状态为沿F2断裂近直立分布,垂向坑道岩石地球化学采样分析预测,深部具有成矿潜力,存在良好的找矿前景。

云南乐红铅锌矿床成矿时代与成矿物质来源:Rb-Sr和S同位素制约

川滇黔交界地区是我国重要的铅锌矿产地,云南省鲁甸县乐红铅锌矿床是区内近年来探获的又一大型MVT型铅锌矿床。本文通过乐红铅锌矿床闪锌矿Rb-Sr测年获得等时线年龄为200.9±8.3 Ma,显示成矿作用发生于印支晚期。闪锌矿初始锶同位素比值特征指示了成矿金属物质为壳源,主要来自于基底地层和沉积盖层。矿床金属硫化物硫同位素特征表明乐红铅锌矿床硫源为海水硫酸盐,还原硫可能是海水硫酸盐经过热化学还原作用(TSR)而来。结合矿床地质特征与区内铅锌矿成矿地质背景,认为乐红铅锌矿床可能是在印支晚期华南板块与印支板块拼合造山作用下,引起成矿流体运移,进而在容矿构造内沉淀成矿的结果。

滇东北乐红大型铅锌矿床稀土元素地球化学特征

乐红铅锌矿床位于扬子地块西南缘,是滇东北铅锌(银)多金属矿集区中的典型代表。通过不同中段典型矿化-蚀变样品中白云石、方解石、重晶石及闪锌矿稀土元素地球化学研究,探讨了该矿床的成矿流体来源。灰黑色白云岩、脉状-团块状白云石、斑团状-脉状重晶石、脉状方解石和各世代闪锌矿的∑REE均较低,均值分别为6.44×10-6、5.62×10-6、4.66×10-6和8.88×10-6,S1:1.12×10-6,S2:0.35×10-6,S3:2.75×10-6;δEu分别为0.72、0.80、68.27和0.65,S1:2.08,S2:3.78,S3:0.75;稀土配分模式为LREE富集-HREE亏损的右倾型。白云石、方解石和闪锌矿在REE配分模式、Eu和Ce异常及La/Ho-Y/Ho图解上的分布等均与未蚀变白云岩接近,表明成矿流体主要来源于碳酸盐地层中的循环水;而早阶段重晶石稀土元素特征差别明显,可能与早期深部流体有关。综合研究表明成矿流体具多源性,可能为源自于深部流体沿构造带运移至有利部位与碳酸盐岩地层中循环水发生混合。Eu、Ce异常特征表明,从成矿早阶段到成矿晚阶段,成矿过程经历了早期高温、氧化→成矿期中高温、弱还原→晚期中低温、还原的演化过程。