Sulfur isotopic composition of the Tianqiao Pb-Zn ore deposit,Northwest Guizhou Province,China：Implications for the source of sulfur in the ore-forming fluids

The Tianqiao Pb-Zn ore deposit of Guizhou Province, China, is located in the mid-east of the Si-chuan-Yunnan-Guizhou Pb-Zn-Ag multi-metallic mineralization area, which is representative of the Pb-Zn ore de-posits in this area. It consists of three main orebodies, whose Pb+Zn reserves are more than 0.2 million ton. This paper analyzes the sulfur isotopic composition of these orebodies. The data show that the ore minerals (galena, sphalerite, pyrite) in these orebodies are enriched in heavy sulfur, with δ34SV-CDT values varying between 8.35‰ and 14.44‰, i.e. the δ34SV-CDT values of pyrite are between 12.81‰ and 14.44‰, the mean value is 13.40‰; the δ34SV-CDT values of sphalerite are range from 10.87‰ to 14.00‰, the mean value is 12.53‰; the δ34SV-CDT values of galena are range from 8.35‰ to 9.83‰, the mean value is 8.84‰, and they have the feature of δ34Spyrite>δ34Ssphalerite>δ34Sgalena, which indicates the sulfur isotope in ore-forming fluids has attained equilibrium. The δ34S V-CDT values of the deposit are close to those of sulfates from carbonate strata of different ages in the ore-field (15‰), which suggests that the sulfur in the ore-forming fluids should be derived from the thermo-chemical sulfate reduction of sulfates from the sedimentary strata.     

Isotope geochemistry of ore fluids for the Dongsheng sandstone-type uranium deposit, China

The Dongsheng sandstone-type uranium deposit is one of the large-sized sandstone-type uranium deposits discovered in the northern part of the Ordos Basin of China in recent years. Geochemical characteristics of the Dongsheng uranium deposit are significantly different from those of the typical interlayered oxidized sandstone-type uranium ore deposits in the region of Middle Asia. Fluid inclusion studies of the uranium deposit showed that the uranium ore-forming temperatures are within the range of 150–160℃. Their 3He/4He ratios are within the range of 0.02–1.00 R/Ra, about 5–40 times those of the crust. Their 40Ar/36Ar ratios vary from 584 to 1243, much higher than the values of atmospheric argon. The δ18OH2O and δD values of fluid inclusions from the uranium deposit are -3.0‰– -8.75‰ and -55.8‰– -71.3‰, respectively, reflecting the characteristics of mixed fluid of meteoric water and magmatic water. The δ18OH2O and δD values of kaolinite layer at the bottom of the uranium ore deposit are 6.1‰ and -77‰, respectively, showing the characteristics of magmatic water. The δ13CV-PDB and δ18OH2O values of calcite veins in uranium ores are -8.0‰ and 5.76‰, respectively, showing the characteristics of mantle source. Geochemical characteristics of fluid inclusions indicated that the ore-formation fluid for the Dongsheng uranium deposit was a mixed fluid of meteoric water and deep-source fluid from the crust. It was proposed that the Jurassic-Cretaceous U-rich metamorphic rocks and granites widespread in the northern uplift area of the Ordos Basin had been weathered and denudated and the ore-forming elements, mainly uranium, were transported by meteoric waters to the Dongsheng region, where uranium ores were formed. Tectonothermal events and magmatic activities in the Ordos Basin during the Mesozoic made fluids in the deep interior and oil/gas at shallow levels upwarp along the fault zone and activated fractures, filling into U-bearing clastic sandstones, thus providing necessary energy for the formation of uranium ores.     

Lead isotopic composition and lead source of the Tongchanghe basalt-type native copper-chalcocite deposit in Ninglang, western Yunnan, China

1 Introduction The native copper-chalcocite deposits associated with the Emeishan basalt have attracted great attention of many scientists engaged in ore deposits in recent years, but their focus is more put on the deposits hos- ted in the high-Ti basalt …     

Geochemical Characteristics of Volcanic Rocks of the Laochang Ag Polymetallic Deposit,Lancang,Yunnan Province,China

In terms of major element, trace element and REE geochemical characteristics ofvolcanic rocks in the area studied and by making use of the TiO2-K2O-P2O5,The-Hf-Ta and Zr-Nb-Y trianglar diagrams and the environmental discrimination diagrams of incompatible ele-ment distribution pattems,the authors have drawn some conclusions that are different from those by previous workers.It is concluded that volcanic rocks in the Laochang Ag polymetallic deposit at Lancang,Yunnan belong to continental within-plate alkali basalts, and that their geotectonic setting seems to be at the northeastern margin of East Gondwana Land.     

REE geochemistry of lamprophyres in Baimazhai nickel deposit, Yunnan Province, China： implication for the mantle source region

Lamprophyresarewidespreadinthe“Sanjiang”(tri river)alkali richintrusiverockbelt(Ailaoshan Jinshajiangalkali richintrusiverockbelt)insouth westernChinaandhaveaclosetemporalandspatialre lationwithAu,Cumineralization(HuYunzhonget al.,1995;HuangZhilongetal.,1999).Therefore,thereiscrucialsignificanceinsuchaspectsastectonic environment,mantlemetasomatism,crust mantlein teraction,magmaticevolutionandassociatedminerali zation.TheBaimazhainickeldepositislocatedinthe southernsegmentofthe“Sanjiang…     

Lead isotopic systematics for native copperchalcocite mineralization in basaltic lavas of the Emeishan large igneous province, SW China： Implications for the source of copper

The Emeishan continental flood basalt, which is widespread in Yunnan, Guizhou and Sichuan provinces of Southwest China, is the volcanic product of a Permian mantle plume, and native copper-chalcocite mineralization associated with the basalt is very common in the border area of Yunnan and Guizhou provinces. The mineralization occurred in the tuff intercalation and terrestrial sedimentary rock intercalation which were formed during the main period of basalt eruption. The orebodies are controlled by the stratigraphic position and faults. Metal ore minerals in the ores are mainly native copper, chalcocite and tenorite, with small amounts of chalcopyrite, bomite, pyrite and malachite, and sometimes with large amounts of bitumen, carbon and plant debris. Several decades of ore deposits are distributed in the neighboring areas of the two provinces, while most of them are small-scale deposits or only ore occurrences. By comparing the lead isotopic composition of the ores with that of the wall-rocks, cover and basement rocks of various periods, the source of copper in this type of ore deposits was studied in this paper. The results showed that: (1) The Pb isotopic composition of the ores from ten deposits is absolutely different from that of sili-ceous-argillaceus rocks of the Upper Permian Xuanwei Formation, limestones of the Lower Permian Series and Carboniferous, Cambrian sandstone-shale and recta-sedimentary rock and dolomite from the upper part of the Meso-Proterozoic Kunyang Group, This indicates that ore lead was derived neither from the cover rock nor from the basement rocks; (2) Although the Neo-Proterozoic Siman dolomite and silicalite, and dolomite in the lower part of the Kunyang Group are similar in Pb isotopic composition to the ores, lead and copper contents in these rocks are very low and they have not made great contributions to copper mineralization; (3) The ores have the same Pb iso-topic composition as the basalt, the latter being enriched in copper. These facts indicate that lead and copper were derived from the basalt. According to the regional geological data and the geological-geochemical characteristics of the ore deposits, it is suggested that ore-forming materials were leached out from the basalt. The thickness and buried depth of the basalt and regional tectonic dynamics can affect the formation of large-scale copper deposits. Therefore, exploration for this type of ore deposits should be conducted in the areas from western Yunnan to western Sichuan, where there are developed basalts of great thickness, with extensive tectonic movement and magmatic activity.     

Geochemistry of meta-volcanic rocks from the Longbohe Cu deposit, Yunnan Province, China： Implications for the genesis and tectonic setting

The Longbohe Cu deposit, which is located in the southern part of the Honghe ore-forming zone, Yunnan Province, China, belongs to a typical ore field where volcanic rocks are of wide distribution and are associated with Cu mineralization in time and space. The volcanic rocks in the ore field, which have experienced varying degree of alteration or regional metamorphism, can be divided into three types, i.e., meta-andesite, meta-subvolcanic rock and meta-basic volcanic rock in accordance with their mineral assemblages. These three types of volcanic rocks in the ore field are relatively rich in Na and the main samples plot in the area of alkali basalts in the geochemical classification diagram. With the exception of very few elements, these three types of volcanic rocks are similar in the content of trace elements. In comparison to the basalts of different tectonic settings, the meta-volcanic rocks in the ore field are rich in high field strength elements (HFSE) such as Th, Nb, etc. and depleted in large ion lithophile elements (LILE) such as Sr, Ba, etc. and their primary mantle-normalized trace element patterns show remarkable negative Th and Nb anomalies and negative Sr and Ba anomalies. These three types of volcanic rocks are similar in REE content range and chondrite-normalized REE patterns with the exception of Eu anomaly. Various lines of evidence show that these three types of volcanic rocks in the ore field have the same source but are the products of different stages of magmatic evolution, their original magma is a product of partial melting of the metasomatically enriched mantle in the tensional tectonic setting within the continent plate, and the crystallization differentiation plays an important role in the process of magmatic evolution.     

The metallogenic mechanism of the Dadengge gold polymetallic deposit in the Jiaodong Peninsula: Constraints from pyrite Rb-Sr dating,in situ S isotope and trace elementsSCIEI北大核心CSCD

大邓格金多金属矿床是胶东半岛唯一的一个金、银、铅、锌、铜共生的多金属矿床。与胶东金矿床主要分布于华北克拉通东南缘的胶北地体不同,大邓格矿床处于苏鲁-大别造山带最东端的威海超高压变质带。准确限定大邓格矿床的成矿年龄和成矿物质来源对深入理解胶东晚中生代成矿作用及构造背景具有重要意义。本文选取大邓格金多金属矿床主成矿阶段矿石中的黄铁矿开展Rb-Sr同位素定年和原位硫同位素及微量元素分析,以此限定成矿时限、成矿物质来源和成矿机制。结果显示黄铁矿Rb-Sr同位素等时线年龄为109.8±1.7Ma(MSWD=1.4),与该区域的钼、铜等有色金属矿床成矿时代一致,略晚于胶东大规模金矿爆发的时代(~120Ma)。主成矿阶段的硫同位素在-1.20‰~6.65‰之间,平均值为5.31‰。黄铁矿中富集Cu、Pb、Zn、Co、Ni等亲硫元素和铁族元素,Co/Ni比值介于0.03~1.36之间。大邓格金多金属矿床在空间上产于伟德山岩体的崮庄岩石单元外围,且成岩、成矿时代一致,表明二者具有密切的成因联系。综合分析认为,胶东早白垩世成矿作用受控于与古太平洋板块俯冲、华北克拉通破坏有关的热隆-伸展构造环境,俯冲板块向东后撤造成了西早东晚的区域成矿时间差异。     

Characteristics of fluid inclusions and metallogenic mechanism of the Longshang skarn type tin polymetallic deposit in eastern Hunan Province,ChinaSCIEI北大核心CSCD

矽卡岩型锡矿是全球重要的锡金属来源,但是锡石沉淀成矿机制仍存在较大的争议。垄上矽卡岩型锡矿床位于湘东锡田锡多金属矿田中部,是南岭钨锡成矿带内矽卡岩型锡矿的典型代表。本文在野外考察、矿石矿相学、流体包裹体岩相学研究的基础上,采用流体包裹体组合法对垄上矽卡岩矿床不同矿化阶段代表矿物中的流体包裹体进行了详细研究。结果显示,垄上矽卡岩型多金属矿床成矿阶段可划分为矽卡岩阶段、退化蚀变阶段、云英岩-氧化物阶段、石英硫化物阶段以及萤石碳酸盐化等5个阶段,其中,锡石主要形成于云英岩-氧化物阶段。与锡石密切共生的石英中发育流体包裹体类型主要为富液相、富气相两相水溶液包裹体,含液相CO_(2)三相水溶液包裹体和纯CO_(2)型包裹体。流体温度和盐度具有较大的变化范围(200-400℃和2%-9%NaCleqv),指示流体在降温过程中经历了显著的不混溶。与硫化物共生的石英中主要为富液相两相水溶液包裹体,温度和盐度主要集中在190-261℃和3%-7%NaCleqv,指示流体冷却过程同时经历了流体混合。本次研究提出锡田矽卡岩型矿床中流体不混溶是导致云英岩-氧化物阶段锡石沉淀成矿的主要机制,而流体冷却和混合是导致硫化物沉淀的主要原因。     

Ore-forming mechanism of Caledonian W-Sn deposit in the Nanling Range: A case study from the Luojiachong deposit,sourthwestern Hunan Province.SCIEI北大核心CSCD

近来南岭地区加里东期钨锡找矿勘查取得较大突破,但其成因机制研究仍相对缺乏。湘西南苗儿山岩体西北部的落家冲矿床是近年新发现的加里东期钨锡矿床,具有良好的钨锡多金属矿找矿前景,其成矿流体的特征和成矿机制有待查明。在详细的野外地质调查基础上,落家冲矿床的成矿过程可划分为四个阶段:蚀变花岗岩-白钨矿阶段(Ⅰ)、云英岩-白钨矿-锡石阶段(Ⅱ)、石英脉-白钨矿阶段(Ⅲ)和石英脉-硫化物阶段(Ⅳ)。本文选取第Ⅰ阶段的锆石和锡石开展了U-Pb定年和锆石Hf同位素分析,对四个成矿阶段的石英矿物进行了流体包裹体以及H-O同位素的研究。获得的锡石U-Pb反等时线年龄(433.0±11Ma)与蚀变花岗岩锆石U-Pb年龄(430.7±2.3Ma)在误差范围内一致,表明矿区的成岩成矿作用均发生于加里东晚期。流体包裹体研究显示第Ⅰ阶段到第Ⅳ阶段,均一温度分别集中在260-380℃、260-320℃、200-320℃和180-220℃之间,呈逐渐降低的趋势,盐度则表现为由第Ⅰ阶段到第Ⅱ阶段陡降,第Ⅱ阶段到第Ⅳ阶段总体变化不大的特点(平均值分别为16.9%、3.9%、4.8%和3.7%NaCleqv)。成岩成矿定年结果、各成矿阶段的成矿流体特征,结合锆石εHf(t)=-7.6--5.0、tDM2=1565-1711Ma,和石英矿物的δ18OH_(2)O值从第Ⅰ阶段(3.97‰-5.34‰)到第Ⅳ阶段(-4.99‰--5.10‰)逐渐降低的特点,以及区域岩体的地球化学特征,本文认为落家冲钨锡矿床是加里东期起源于元古宙地壳重熔的岩浆在经历了高分异演化作用后,流体的沸腾作用以及温度下降造成成矿流体中钨锡等矿质的沉淀所形成。     

滇东南白牛厂多金属矿床铅同位素组成及铅来源新认识

白牛厂矿床位于滇东南锡多金属成矿带中部,是一个Ag、Pb、Zn、Sn等共生的多金属矿床,但成因争议较大.前人引用早期矿床矿石矿物铅同位素数据得出矿石铅主要来源于基底岩石淋滤,矿床经历了热水沉积+岩浆热液叠加两个成矿阶段的结论.本文采用最新铅同位素数据系统研究了白牛厂矿床的铅同位素组成,其中,白牛厂矿床矿石矿物的铅同位素组成206Pb/204Pb、207Pb/204Pb和208Pb/204Pb分别为17.264～18.537、14.843～15.862和38.481～39.424;薄竹山花岗岩长石铅同位素组成206Pb/204Pb、207Pb/204Pb和208Pb/204Pb分别为18.301～18.387、15.611～15.670和38.677～38.904;薄竹山岩体接触带型矿床(点)矿石矿物铅同位素组成206Pb/204Pb、207Pb/204Pb和208Pb/204Pb分别为18.302～18.417、15.603～15.692和38.596～38.868;区域地层及矿区地层钻孔样品铅同位素组成206Pb/204Pb、207Pb/204Pb和208Pb/204Pb分别为18.307～19.206、15.622～15.809和38.436～39.932.对比四者铅同位素组成特征,白牛厂矿床矿石矿物、薄竹山花岗岩长石、薄竹山岩体接触带型矿床(点)矿石矿物具有一致的铅同位素组成,与地层铅同位素组成相差甚远,表明白牛厂矿床铅主要来自岩浆作用,在侵入的过程中可能受到了地层的轻度混染.矿床地质特征及近期地球化学和年代学研究成果表明,白牛厂矿床的形成主要受岩浆作用影响,沉积成矿作用在白牛厂矿床很可能是不存在的.     

Sulfur isotopic compositions of the Huize super-large Pb–Zn deposit, Yunnan Province, China: Implications for the source of sulfur in the ore-forming fluids

The Huize Pb–Zn deposit of Yunnan Province, China, is located in the center of the Sichuan–Yunnan–Guizhou Pb–Zn–Ag district. Four primary orebodies (orebody No. 1, No. 6, No. 8 and No. 10), with Pb + Zn reserves from 0.5 Mt to 1 Mt, have been found at depth in this deposit. This paper provides new data on the sulfur isotopic compositions of the four orebodies. The data show that the principal sulfide minerals (galena, sphalerite and pyrite) in the four orebodies are enriched in heavy sulfur, the δ³⁴S values between 10.9‰ and 17.7‰ and where δ³⁴S_pyrite > δ³⁴S_sphalerite > δ³⁴S_galena. The δ³⁴S values of sulfide are close to that of the sulfates from the carbonate strata within the region. The similarity in sulfur isotope composition between sulfides and sulfates indicates the sulfur in the ore-forming fluids was likely derived by thermochemical sulfate reduction of sulfates contained within carbonate units.     

Lead Isotopic Composition and Lead Source in the Bainiuchang Ag-polymetailic Deposit,Yunnan Province,China

The Bainiuchang deposit in Yunnan Province,China,is located geographically between the Gejiu ore field and the Dulong ore field.In addition to the>7000 t Ag reserves,the deposit also boasts of large-scale Pb,Zn and Sn reserves with a lot of dispersed elements(In,Cd,Ge,Ga,etc.).We have determined systematically the Pb isotope composition of the deposit.The Pb isotope ratios of the ores that are of sea-floor exhalative sedimentary origin in the northwest of the mining district,are ~(206)Pb/~(204)Pb=17.758-18.537,~(207)pb/~(204)pb=15.175-15.862 and ~(208)pb/~(204)pb=37.289-39.424,while those of ores that are of magmatic hydrothermal superimposition origin in the southeast of the mining district, are ~(206)Pb/~(204)Pb=17.264-18.359,~(207)Pb/~(204)Pb=14.843-15.683 and ~(208)Pb/~(204)Pb=36.481-38.838, respectively.In terms of the Pb isotope composition of feldspar in magmatic rocks or magmatic whole- rock samples from the mining district,we have determined the Pb isotope composition and acquired the Pb isotope ratios as:~(206)Pb/~(204)Pb=18.224-18.700,~(207)Tpb/~(204)Pb=15.595-15.797 and ~(208)Pb/~(204)Pb= 38.193-39.608.Then,in the light of the Pb isotope composition of metamorphic rock samples from the Proterozoic basement exposed in the Dulong ore field,we have determined the Pb isotope composition and obtained the isotope ratios as:~(206)Pb/~(204)Pb=18.434-19.119,~(207)Pb/~(204)Pb=15.644-15.693,and ~(208)Pb/~(204)Pb=38.514-38.832.And the Pb isotope ratios of Cambrian sedimentary rocks,which are exposed in the Bainiuchang mining district,are ~(206)Pb/~(204)Pb=18.307-19.206,~(207)Pb/~(204)Pb= 15.622-15.809,and ~(206)Pb/~(204)Pb=38.436-39.932.By comparing the two types of ores with respect to their Pb isotope compositions,it is indicated that lead in the Bainiuchang deposit was derived largely from the lower-crust granulite which is earlier than Neoproterozoic in age,but the Yanshanian magmatic hydrothermal fluids probably provided a part of ore-forming elements such as Sn for the ore blocks in the south of the mining district.     

云南澜沧老厂大型银多金属矿床碳、氧同位素组成及其意义

文章系统研究了老厂矿床的碳酸盐围岩和成矿方解石的碳、氧同位素组成.研究表明,相对于区域地层,矿区碳酸盐岩围岩普遍亏损18O;成矿方解石的碳氧同位素总体上具有明显的正相关性,这些特征表明成矿流体与围岩发生了大规模的水岩反应.文章初步建立了水岩反应的理想模式,根据该模式进一步将成矿方解石划分为矿体中心相和边缘相2组.水岩反应理论模拟表明:总体上成矿流体中的可溶性碳以H2CO3为主,中心相成矿流体的δ13C、δ18O值分别为-5.5‰和+4‰,具有典型深部岩浆流体的特征;边缘相成矿流体的δ13C、δ18O值分别为-1.5‰和+4‰,代表了深部岩浆流体与下渗天水共同交代碳酸盐岩围岩后的碳、氧同位素特征.     

云南白牛厂银多金属矿床喷流沉积成因证据:容矿岩石的地球化学约束

滇东南是否存在广泛的热水沉积活动已成为制约滇东南三大多金属矿床(个旧、都龙、白牛厂)成因研究的主要因素之一。系统研究了白牛厂银多金属矿床容矿岩石的地球化学特征,研究表明:矿床容矿岩石主量元素数据均投影于火山及海底热卤水成因区域内;稀土元素明显分为两组,稀土元素总量较高的样品可能与较多的正常沉积物的加入有关;稀土元素总量较低的样品具有与加拿大沙利文矿山的条带状富电气石热液沉积岩和加拿大Agnico-Eugle矿山的铁建造中的条带状燧石岩相似的稀土元素配分模式与标准化参数;同时,微量元素对的演化趋势与现代大洋热水沉积物相似,而且As、Sb和Ag含量与大厂和个旧热水沉积硅质岩相当。推测白牛厂银多金属矿床属热水沉积成矿,只是在距花岗岩体较近的部位遭受了部分叠加改造。     

兰坪白秧坪铜银多金属矿床成矿物质来源的铅和硫同位素示踪

白秧坪铜银多金属矿床主要产于白垩系下统景星组石英砂岩、粉砂岩中,矿石铅同位素组成特征与景星组砂岩的铅同位素组成比较接近,表明壳源物质参与了成矿作用。作ZartMan图解和Δγ-Δβ图解表明,矿石铅属于壳幔混合来源。矿石铅μ值介于9.43~9.65之间,Th/U比值介于3.72~3.87之间,表明矿石铅为壳幔混合铅。该矿床硫同位素组成表明,硫来源于深部地幔硫遭受地壳硫的混入。该矿床的成矿作用发生于开放体系之中,成矿物质来源为深部幔源物质混合了壳源物质。     

云南白牛厂银多金属矿床成因

对云南白牛厂超大型银多金属矿床的地质、地球化学特征及矿床形成的长期性及多阶段性的研究认为:白牛厂银多金属矿床是热水沉积—叠生成因矿床,早期呈现寒武纪的热水同生沉积成矿作用,晚期为燕山期花岗岩浆热液成矿作用。该矿床是热水沉积成矿作用与岩浆热液成矿作用叠加成矿的产物。     

云南富宁者桑金矿床硫铅同位素地球化学特征与成矿物质来源

者桑金矿床赋存于上二叠统吴家坪组沉积碎屑岩中,矿体受构造破碎带控制,呈似层状、透镜状产出,是滇东南金成矿带上一个典型的卡林型金矿床。硫铅同位素地球化学研究显示,沉积黄铁矿和热液硫化物(黄铁矿和毒砂)的δ34S值均为正值,变化范围较窄(8.4‰～11.3‰),与二叠纪沉积时期海水硫酸盐δ34S值一致,具有地层硫的特征。矿石中的硫主要通过地层中有机质与海水硫酸盐的热还原作用(TSR)提供。铅同位素组成中,206Pb/204Pb变化范围较宽,207Pb/204Pb和208 Pb/204 Pb较为稳定,计算获得的模式年龄变化范围大(-62～389Ma),甚至出现"负年龄",表明除正常铅外,还有较多的放射性成因铅的混入。铅主要来自于上地壳,有少量岩浆物质的混入。矿石与围岩的硫铅同位素具有一定的继承性,成矿物质主要来自地层。