湘西-黔东地区碳酸盐岩容矿铅锌矿床成矿模式

湘西-黔东地区位于扬子陆块东南缘,在该地区碳酸盐岩地层中,目前已发现大、中、小型铅锌矿床及矿点200余处.为了解湘西-黔东地区铅锌矿床成矿作用过程,系统总结了区内主要铅锌矿床地质与地球化学特征,并对成矿机制进行探讨,建立成矿模式.区内铅锌矿床主要赋存于下寒武统碳酸盐岩中,分布明显受断裂及褶皱构造控制,矿体主要为层状、似层状或透镜状,矿物组成主要为闪锌矿、方铅矿、黄铁矿、方解石及少量萤石、重晶石和沥青,并伴随着广泛的以方解石化为主的热液蚀变.闪锌矿与方解石中的流体包裹体均一温度集中在120~200℃之间,盐度集中在8%~20%(NaCl_eqv)之间;成矿期方解石的δ13C_PDB值范围为-4.89‰~1.50‰,δ18O_SMOW值范围为13.37‰~25.09‰,略低于碳酸盐围岩;矿石硫化物δ34S值变化范围为22.3‰~36.1‰,以富含重硫为主;矿石硫化物铅同位素组成较为均一,变化范围较小,206Pb/204Pb在17.952~18.678之间,207Pb/204Pb在15.635~15.832之间,208Pb/204Pb在38.015~39.255之间.对地质和地球化学资料的综合分析表明,湘西-黔东地区铅锌矿床成矿流体为低温、中高盐度热卤水,主要来源于建造水和大气降水,成矿流体中的碳主要来源于碳酸盐围岩的溶解作用,硫来源于碳酸盐岩地层中硫酸盐热化学还原作用(TSR),铅锌主要来源于下伏地层,成矿时代为晚志留世-早泥盆世,属于比较典型的密西西比河谷型(MVT)铅锌矿床.综合以上分析建立了该地区铅锌矿床有机质参与下的多源流体混合成矿模式.      

Strontium isotopic geochemistry of Tianqiao Pb-Zn deposit,Southwest China

Tianqiao carbonate-hosted Pb-Zn deposit, controlled by NW-trending F37 thrust fault and NW-trending Tianqiao anticline, is located in the eastern part of Sichuan-Yunnan-Guizhou （SYG） Pb-Zn metallogenic province, southwestern Yangtze Block, southwest China. Ore bodies in this deposit are hosted in the Devonian-Carboniferous carbonate rocks, and ore minerals include sphalerite, galena and pyrite, while the gangue minerals are dominated by calcite and dolomite. Using high-precision solid thermal ionization mass spectrometry （TIMS）, this paper reports the strontium isotopic compositions （0.7119 to 0.7167） of sulfide samples from the Tianqiao deposit in order to trace the origin of hydrothermal fluids. Compared with the country rocks, the calculated 87Sr/86Sr200 Ma values of sulfide range from 0.7118 to 0.7130, higher than those of the age-corrected Devonian to Permian sedimentary rocks （0.7073 to 0.7101） and the Middle Permian Emeishan flood basalts （0.7078 to 0.7039）, but lower than those of the age-corrected Proterozoic basement rocks （such as the Kunyang and Huili Groups, 87Sr/86Sr200 Ma=0.7243 to 0.7288）. This implies a mixed strontium source between the older basement rocks and the younger cover sequences. Together with geologic and previous isotopic evidences, we considered that the fluids＇ mixing is a possible mechanism for sulfide precipitation in the Tianqiao deposit.     

湘西北花垣矿集区铅锌矿床成矿流体来源及矿床成因

湘西北花垣矿集区位于扬子地台东南缘,是湘西-鄂西成矿带上最典型的超大型铅锌矿床所在地.通过对花垣矿集区典型铅锌矿床流体包裹体显微测温、成分分析及C、H、O同位素研究,结果表明,该区铅锌矿床闪锌矿与方解石中流体包裹体的均一温度范围集中在120~200℃,盐度范围集中在8%~20% NaCl_eqv.流体中液相离子成分主要为Ca2+、Na+、Mg2+、SO₄2-、Cl-,气相成分主要为H₂O、N₂和CO₂及少量的CO、CH₄和H₂.流体的δD_SMOW值范围为-60.4‰~-33.0‰,δ18O_流体值范围为3.8‰~9.2‰.以上流体包裹体和稳定同位素分析结果表明,花垣矿集区铅锌矿床的成矿流体具有热卤水的性质,主要来源于建造水和大气降水.成矿期方解石的δ13C_PDB值范围为-4.89‰~0.57‰,δ18O_SMOW值范围为13.37‰~21.73‰,略低于碳酸盐围岩,说明成矿流体中的碳主要来源于碳酸盐围岩的溶解作用.矿石沉淀机制可能为两种流体的混合,即来自深部的富含金属物质的热卤水与富含有机质和硫酸盐的建造水及下渗大气降水的混合导致了铅锌矿石的沉淀.对地质和地球化学资料的综合结果表明,花垣矿集区铅锌矿床属于密西西比河谷型（MVT）铅锌矿床.      

滇中荒田铅锌矿床Rb-Sr同位素年代学与C-O-S-Pb同位素地球化学特征

滇中荒田铅锌矿床赋存于下二叠统碳酸盐岩与上二叠统峨眉山玄武岩接触界面上,矿体主要呈似层状、透镜状产出。矿石矿物组合以闪锌矿、方铅矿为主,脉石矿物以石英、方解石、白云石为主。热液方解石C、O同位素组成表明荒田铅锌矿床成矿流体中CO_2的碳具有多元性,主要来源于幔源与海相碳酸盐岩的混合碳;硫化物硫同位素组成表明荒田铅锌矿床硫以岩浆硫为主,可能混有其他硫源(可能包括地层硫酸盐),铅同位素表明赋矿围岩、玄武岩和燕山期花岗岩均有可能为成矿提供了成矿物质,是多源混合后的产物;闪锌矿Rb-Sr同位素等时线年龄为(83.2±3.4)Ma,指示荒田铅锌矿床形成于晚燕山期,荒田铅锌矿床成矿动力学背景可能与右江褶皱带在中生代末期发生了大规模的岩石圈伸展有关。而晚二叠世海相喷发火山岩对矿区铅锌矿床的形成起了重要的盖层、赋矿层及矿化作用。综上,荒田铅锌矿床成矿流体中的不同组分来源不同,矿床类型为沉积-改造型矿床。     

滇东铅锌多金属矿成矿过程探讨

位于扬子陆块南部被动边缘褶-冲带的滇东铅锌多金属成矿区是我国重要的铅锌多金属矿产地之一。区内矿床赋矿围岩为震旦系-二叠系碳酸盐岩,以构造控矿为主;成矿过程漫长,成矿元素来自上下不同层位的地层中,成矿流体具多源特征。本次研究收集了前人关于滇东地区铅锌多金属矿勘查和研究成果,并利用作者在滇东地区长期从事矿产勘查所获得的资料...     

Ore genesis of the Tianbaoshan carbonate-hosted Pb–Zn deposit,Southwest China: geologic and isotopic (C–H–O–S–Pb) evidence

The Tianbaoshan Pb–Zn deposit, part of the Sichuan–Yunnan–Guizhou (SYG) Pb–Zn metallogenic province, is located in the western Yangtze Block and contains 2.6 million tonnes of 10–15 wt.% Pb + Zn metals. Ore bodies occur as vein or tubular types and are hosted in Sinian (late Proterozoic) carbonate rocks and are structurally controlled by the SN-trending Anninghe tectonic belt and NW-trending concealed fractures. The deposits are simple in mineralogy, with sphalerite, galena, pyrite, chalcopyrite, arsenopyrite, freibergite, and pyrargyrite as ore minerals and dolomite, calcite, and quartz as gangue minerals. These phases occur as massive, brecciated, veinlet, and dissemination in dolostone of the upper Sinian Dengying Formation. Hydrogen and oxygen isotope compositions of hydrothermal fluids range from –47.6 to –51.2‰ and –1.7 to +3.7‰, respectively. These data suggest that H₂O in hydrothermal fluids had a mixed origin of metamorphic and meteoric waters. Carbon and oxygen isotope compositions range from –6.5 to –4.9‰ and +19.3 to +20.2‰, respectively. These compositions plot in the field between mantle and marine carbonate rocks with a negative correlation, suggesting that CO₂ in the ore-forming fluids had multiple sources, including the Permian Emeishan flood basalts, Sinian-to-Permian marine carbonate rocks, and organic matters in Cambrian-to-Permian sedimentary rocks. Sulphur isotope compositions range from –0.4 to +9.6‰, significantly lower than Cambrian-to-Permian seawater sulphate (+15 to +35‰) and sulphate (+15 to +28‰) from evaporates in Cambrian-to-Permian strata, implicating that the S was derived from host-strata evaporates by thermal–chemical sulphate reduction. ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb ratios range from 18.110 to 18.596, 15.514 to 15.878, and 38.032 to 39.221, respectively, which plot in field of the upper crust Pb evolution curve, unlike those of Proterozoic basement rocks, Sinian dolostone, Devonian-to-Permian carbonate rocks, and the Permian Emeishan flood basalts, implying complex derivation of Pb metal in the ore-forming fluids. Geological and isotopic studies of the Tianbaoshan Pb–Zn deposit reveal that constituents in the hydrothermal fluids were derived from multiple sources and that fluid mixing was a possible metallogenic mechanism. The studied deposit is not distal magmatic–hydrothermal, sedimentary exhalative (SEDEX), or Mississippi Valley (MVT) types, rather, it represents a unique ore deposit type, named in this article the SYG type.     

青海玉树东莫扎抓铅锌矿床地质特征及碳氢氧同位素地球化学研究

东莫扎抓铅锌矿床位于青藏高原羌塘地体东北缘,是"三江"北段铅锌铜银多金属成矿带中的典型代表,对该矿床地质特征和成因类型的研究有助于理解区域铅锌铜银多金属成矿规律,对区域找矿具有重要意义.笔者通过详细的矿区地质考察、系统的矿石光薄片显微镜下鉴定和矿石中方解石的碳、氢、氧同位素分析测试,概述了东莫扎抓铅锌矿床的地质特征和成矿流体的碳、氢、氧同位素组成特征.东莫扎抓铅锌矿床矿体呈似层状展布,产状严格受到矿区逆冲断层的控制,赋矿围岩为上三叠统结扎群波里拉组灰岩和下一中二叠统开心岭群尕迪考组灰岩,发育强白云石化和弱硅化,矿物组合简单,主要为闪锌矿+方铅矿+黄铁矿+白云石+方解石+重晶石,矿石结构以皮壳状、草莓状等胶状结构和他形粒状结构为主,矿石构造为浸染状、角砾状、团块状和脉状.矿石中方解石的δ~(13)C_(V-PDB)值、δ~(18)O_(V-SMOW)值分别为δD_(V-SMOW)值分别为-1.8‰～+3.3‰、+6.1‰～+24.6‰和-137‰～-53‰,计算得到成矿流体的δ~(18)O_(流体)值为-0.5‰～+13.8‰.研究结果表明,东莫扎抓铅锌矿床的成矿流体主要来自盆地封存热卤水和大气降水,金属物质可能由区域流体在长距离迁移过程中通过与碳酸盐岩地层相互作用,以及淋滤含矿地层底部的火山岩而得来,成矿过程中伴随着碳酸盐岩的溶解作用,可能存在有机质的参与.据此,笔者将东莫扎抓矿床归为发育在碰撞造山带中受逆冲推覆断裂构造控制的类MVT铅锌矿床,并初步建立了东莫扎抓铅锌矿床的构造控矿模型.     

Geological and C–O–S–Pb–Sr isotopic constraints on the origin of the Qingshan carbonate-hosted Pb–Zn deposit,Southwest China

Located in the western Yangtze Block, the Qingshan Pb–Zn deposit, part of the Sichuan–Yunnan–Guizhou Pb–Zn metallogenic province, contains 0.3 million tonnes of 9.86 wt.% Pb and 22.27 wt.% Zn. Ore bodies are hosted in Carboniferous and Permian carbonate rocks, structurally controlled by the Weining–Shuicheng anticline and its intraformational faults. Ores composed of sphalerite, galena, pyrite, dolomite, and calcite occur as massive, brecciated, veinlets, and disseminations in dolomitic limestones.

The C–O isotope compositions of hydrothermal calcite and S–Pb–Sr isotope compositions of Qingshan sulphide minerals were analysed in order to trace the sources of reduced sulphur and metals for the Pb–Zn deposit. δ¹³C_PDB and δ¹⁸O_SMOW values of calcite range from –5.0‰ to –3.4‰ and +18.9‰ to +19.6‰, respectively, and fall in the field between mantle and marine carbonate rocks. They display a negative correlation, suggesting that CO₂ in the hydrothermal fluid had a mixed origin of mantle, marine carbonate rocks, and sedimentary organic matter. δ³⁴S values of sulphide minerals range from +10.7‰ to +19.6‰, similar to Devonian-to-Permian seawater sulphate (+20‰ to +35‰) and evaporite rocks (+23‰ to +28‰) in Carboniferous-to-Permian strata, suggesting that the reduced sulphur in hydrothermal fluids was derived from host-strata evaporites. Ores and sulphide minerals have homogeneous and low radiogenic Pb isotope compositions (²⁰⁶Pb/²⁰⁴Pb = 18.561 to 18.768, ²⁰⁷Pb/²⁰⁴Pb = 15.701 to 15.920, and ²⁰⁸Pb/²⁰⁴Pb = 38.831 to 39.641) that plot in the upper crust Pb evolution curve, and are similar to those of Devonian-to-Permian carbonate rocks. Pb isotope compositions suggest derivation of Pb metal from the host rocks. ⁸⁷Sr/⁸⁶Sr ratios of sphalerite range from 0.7107 to 0.7136 and (⁸⁷Sr/⁸⁶Sr)_200Ma ratios range from 0.7099 to 0.7126, higher than Sinian-to-Permian sedimentary rocks and Permian Emeishan flood basalts, but lower than Proterozoic basement rocks. This indicates that the ore strontium has a mixture source of the older basement rocks and the younger cover sequence. C–O–S–Pb–Sr isotope compositions of the Qingshan Pb–Zn deposit indicate a mixed origin of the ore-forming fluids and metals.     

New insights into the origin of early Cambrian carbonate-hosted Pb-Zn deposits in South China: A case study of the Maliping Pb-Zn deposit

The western margin of the Yangtze Block hosts the giant Upper Yangtze Pb-Zn metallogenic province, with the occurrence of >400 carbonate-hosted Pb-Zn deposits. More than 50% of these deposits are hosted in carbonate rocks of late Ediacaran to early Cambrian age. Although they have attracted great attention over the past two decades, it is still unclear why such carbonate sequences host so many Pb-Zn deposits and the role that the country rocks played during mineralization. The newly-discovered Maliping Pb-Zn deposit (~6 Mt @ 4.18 wt% Pb and 9.18 wt% Zn) is hosted in early Cambrian strata composed of carbonate and phosphate rocks, black shales, as well as evaporite sulfates, of which the carbonate rocks are the direct ore-hosting rocks. Evidence from mineralogy and the concentrations of ore-forming metals indicate that the phosphate rocks played an important role in providing geochemical barriers during Pb-Zn ore formation. Homogenization temperatures of the primary fluid inclusions in sphalerite and quartz range from 185 to 282 °C, and their salinities vary from 3.39 to 17.17 wt% NaCl equiv. The REE and C-O isotopes imply that the hydrothermal carbonates were formed under relatively oxidizing conditions and that the wall rocks were involved in the Pb-Zn mineralization through dissolution. Sulfur isotopic compositions (δ³⁴S = +7.60–+31.79‰) of sulfides reveal that S²⁻ originated from evaporite sulfates within the ore-hosting strata, and that the black shales acted as an important reducing agent during thermo-chemical reduction (TSR). Pb isotopic ratios of galena (²⁰⁶Pb/²⁰⁴Pb = 17.856–17.973, ²⁰⁷Pb/²⁰⁴Pb = 15.668–15.689 and ²⁰⁸Pb/²⁰⁴Pb = 37.953–38.101) are similar to those of Proterozoic basement rocks in the region. This implies that the basement could be the key source of mineralizing metals. Hence, we propose that: (i) The favorable lithological combination of early Cambrian phosphate rocks, black shales, carbonates and evaporites, as well as Proterozoic basement in the area, were responsible for controlling the majority of Pb-Zn deposits in the late Ediacaran-early Cambrian carbonate sequences in the western Yangtze Block; and (ii) the Maliping Pb-Zn deposit resulted from a combination of mineralized fluids, various trap structures and favorable lithologies, of which the fluids were epigenetic with low to moderate temperatures and salinities.     

四川天宝山矿床闪锌矿Rb-Sr年代学、稳定同位素及地质意义

四川天宝山铅锌矿床是赋存于震旦系灯影组白云岩中的大型铅锌矿床,一直以来缺乏精确的成矿年龄数据,致使其成矿构造环境存在争议.获取了闪锌矿Rb-Sr年龄,联合H-O、C-O同位素数据,以确定其成矿年代、成矿物质来源及成矿构造环境.闪锌矿Rb-Sr年龄为348.5±7.2 Ma(MSWD=1.10),表明矿床形成于早石炭世.热液矿物δD_H2O、δ18O值分别为-19.3‰~-58.1‰、-1.4‰~0.6‰,沿海水与地层有机质反应线分布,并有向雨水线漂移的趋势,说明成矿流体中水是海水与地层有机质反应并加入雨水的混合体.热液方解石δ13C、δ18O值明显分为两群,分别为-1.7‰~-1.6‰、12.9‰~15.2‰和-6.5‰~-4.9‰、19.3‰~20.2‰,暗示成矿流体中C、O可能来源于赋矿围岩溶解作用和有机质脱羧基作用.闪锌矿(87Sr/86Sr)_i值为0.710 42 ±0.000 13,高于赋矿围岩Sr同位素值而明显低于基底Sr同位素值,指示成矿物质主要来源于赋矿围岩与基底.结果表明川滇黔地区存在两期铅锌成矿作用,分别形成于晚泥盆世-早石炭世与古特提斯洋张开有关的伸展构造环境和晚三叠世-早侏罗世与古特提斯洋闭合有关的收缩构造环境.      

MVT矿床中与成矿有关热液方解石的地球化学判据——以青海多才玛超大型铅锌矿床为例

碳酸盐矿物是MVT型铅锌矿床最为常见的热液蚀变矿物,记录了成矿流体特征,其元素或同位素组成对示踪和定位矿体具有一定的指示意义,但由于该类矿床中碳酸盐矿物成因多样,单一的岩相学观察往往难以准确识别与成矿有关和无关的方解石,需要辅以地球化学手段来确定方解石成因。本文利用钻孔编录、岩相学观察、C-O-Sr同位素和原位微量与稀土元素组成分析等手段,探讨了青海多才玛超大型MVT铅锌矿床中与成矿有关和无关两期方解石的矿物化学特征。结果表明,多才玛矿床成矿前方解石(Cal1)空间上与矿体无相关关系,遍布于中二叠统九十道班组灰岩内,阴极发光呈暗棕色至棕黄色,无明显生长环带;成矿期方解石(Cal2)主要产于铅锌矿体内及其上盘围岩中,多呈砂糖粒状-皮壳状充填于围岩裂隙和溶孔内,阴极发光呈暗黄色至亮橙色,常发育生长环带。相对于Cal2, Cal1与围岩的C-O-Sr同位素组成更为接近,这表明水岩反应期间,Cal1组成受围岩影响更大,Cal2组成受影响更小;相比于Cal1,Cal2具有较高的Mn、Fe、Zn、Pb含量和U/Th、V/Cr值以及较低的LREE/HREE值、Mg、Sr含量和弱的Ce负异常,指示成矿...     

Isotopic Geochemistry of Chinese Fluorite Deposits

China is one of the richest countries in the world in terms of fluorite resources. On the basis of host rocks and mineralization patterns, the fluorite deposits in China have been classified into three types: (1) those occurring in Mesozoic volcanic regions, mainly consisting of veinfilling deposits of the quartz-fluorite association (Type I); (2) those occurring in granite areas, chiefly belonging to veinfilling deposits of the quartz-fluorite association or veinfilling or altered-rock deposits associated with Pb, Zn, W, Sn, etc. (Type II); and (3) those occurring in carbonate rocks as bedded deposits of quartz-fluorite, sulfide-fluorite, and quartz-barite-calcite-fluorite assemblages (Type III).

This paper summarizes the characteristics of fluorite deposits in China on the basis of strontium-, hydrogen-, and oxygen-isotopic and geochronological data, as well as geological investigations of deposits from 22 mining districts. δ¹⁸O and δD values of ore-forming fluids are ?10.2 to +3.7‰ and ?77.9 to 41.0‰, respectively, for Type-I deposits, ?13.1 to ?4.9‰ and ?65.5 to ?41.7‰ for Type-II deposits, and -5.6 to +4.3‰ and ?80 to ?29‰ for Type-Ill deposits. Study of the isotopic water-rock exchange indicates that the mineralizing fluids for these types of deposits have been derived mostly from circulating geothermal water that originated from Mesozoic meteoric water. The differences in the isotopic characteristics of hydrothermal systems for various types of deposits depend mainly on isotopic exchange between water and rocks, the water/rock values being 0.05 to 2.0 for Type-I deposits, generally more than 2.0 for Type-II deposits, and 0.5 to 3.0 for Type-Ill deposits.

The ore-forming ages for Type-I and Type-II deposits are roughly separated into three groups—230 to 180 Ma, 120 Ma, and 90 to 60 Ma. These ages successively decrease from northwestern China to southeastern coastal areas.

⁸⁷Sr/⁸⁶Sr values of 0.7306 to 0.7710 (mean 0.7513) from fluorite in the early stage (main mineralization) for Type-I deposits are higher than those from host rocks (0.7081 to 0.7260) during the mineralizing event, and mostly fall in the range of ⁸⁷Sr/⁸⁶Sr values from basement metamorphic rocks (from 0.7455 to 0.9094) during the epoch of mineralization. But the ⁸⁷Sr/⁸⁶Sr values of 0.7102 to 0.7137 (mean 0.7122) for late-stage fluorite and calcite are similar to those of surrounding host rocks. This indicates that the mineralizing materials of early stages in the formation of deposits (Type-I) originated mostly from Precambrian basement metamorphic rocks; those of later stages (Type II) were derived chiefly from host rocks. Type-II and Type-Ill deposits from different mining areas exhibit great variations in ⁸⁷Sr/⁸⁶Sr values, but are quite similar to their host rocks, indicating that the mineralizing materials in Type-II and Type-Ill deposits were derived chiefly from their host rocks.     

滇东北矿集区茂租铅锌矿床地球化学特征

茂租铅锌矿床位于扬子地台西南缘,是滇东北矿集区内的一个大型矿床,矿体主要呈似层状产于震旦系灯影组白云岩中;矿石矿物以闪锌矿为主,次为方铅矿;脉石矿物主要为白云石、方解石和萤石。本文对该矿床中与铅锌矿密切共生的团块状白云石、方解石和萤石以及围岩灯影组白云岩的REE地球化学特征和C、O、Sr同位素进行了对比研究。结果表明:团块状白云石和方解石的稀土配分模式、C同位素和Sr同位素比值与围岩灯影组白云岩比较接近,表明形成团块状白云石和方解石的成矿流体主要来源于围岩灯影组白云岩的溶解;但这两种矿物的稀土总量ΣREE高于灯影组白云岩,说明成矿流体除了主要由围岩提供REE外,还有部分其他富含REE流体的加入。萤石则具有LREE亏损和分配曲线相对平缓的稀土配分模式特征,表明萤石形成于成矿的晚阶段,有更多的外部流体的加入。团块状白云石、方解石和萤石表现出明显的Eu正异常,且团块状白云石和方解石的O同位素低于灯影组白云岩,反映了存在较高温度的流体活动,这3种脉石矿物是由高温热液流体形成的。灯影组白云岩和3种脉石矿物都具有明显的Ce负异常,说明成矿流体可能主要来源于地层循环水,继承了围岩的Ce负异常特征。方解石和萤石的Sr同位素比值高于围岩震旦系灯影组白云岩和峨眉山玄武岩,但小于基底岩石昆阳群和会理群,说明成矿流体主要由赋矿围岩等沉积地层中的循环流体与流经了基底岩石的深部流体混合形成。     

贵州普定五指山地区铅锌矿床成矿模式

黔西北五指山铅锌矿集区是川滇黔接壤铅锌成矿域的重要组成部分之一,近年已探明多个大中型铅锌矿床,提交铅锌金属资源储量超250万t,实现了地质找矿的重大突破。文章对区内典型矿床的地质、地球化学等资料进行综合分析,并与邻区及MVT矿床进行比较。研究结果显示,本区矿体主要赋存于上震旦统灯影组和下寒武统清虚洞组白云岩中,呈层状、似层状和陡倾斜脉状产出,断控和层控特征明显。矿石自然类型为原生硫化矿型,主要金属矿物由闪锌矿和方铅矿组成。矿床形成受构造、层位及岩性、沉积岩相等因素的约束,构造是必要条件和主要控矿因素,灯影组和清虚洞组鲕状白云岩是有利赋矿层位和容矿岩性,局限-半局限的台地-泻湖相沉积为有利沉积岩相条件。成矿物质具有混合特征,其中成矿金属Pb、Zn等主要来源于基底岩石,而矿化剂C和S则分别来自赋矿海相碳酸盐岩及其内的蒸发膏岩。成矿流体属于与右江盆地演化有关的低温中低盐度盆地卤水,矿体是富金属流体在早燕山期区域挤压向伸展转换的动力学背景下卸载,与富硫流体混合的产物,成矿过程与MVT矿床相似。五指山地区铅锌矿床成矿模式的建立,有望推动区内找矿新突破,并为邻区铅锌成矿预测提供理论指导。     

四川东北寨微细浸染型金矿床的同位素组成特征及其成因意义

东北寨金矿床是我国迄今为止发现的规模最大的浅成热液形成的微细浸染型金矿床。对矿床的同位素组成的研究表明,成矿溶液主要来自大气降水,矿化和蚀变作用是在水/岩比值较低的体系中进行的;硫来自围岩中的还原硫;碳酸盐岩地层是提供金属组分的主源层。地下热液在环流过程中,从围岩中萃取金属矿质,并迁移到黑色岩系地层的破碎带中成矿。     

川滇黔地区MVT铅锌矿床分布、特征及成因

位于扬子地台西南缘的川滇黔铅锌多金属成矿区是中国重要的铅、锌、银、锗生产基地,目前在该成矿区已经发现大、中、小型铅锌矿床和矿点400多处。经过对比研究,这些矿床的赋矿围岩为震旦系一二叠系碳酸盐岩,矿体明显受控于断裂构造,并伴随有强烈的白云岩化和方解石化,以低温、低盐度为特征,成矿时代可能为中生代,成矿物质主要来自地层本身。它们为受热对流循环流体经过成矿物质萃取、搬运和卸载而成矿,是大陆边缘造山带东侧伸展带中的产物,属于比较典型的密西西比河谷型铅锌矿床。     

REE and C-O Isotopic Geochemistry of Calcites from the World-class Huize Pb-Zn Deposits, Yunnan, China: Implications for the Ore Genesis

<正>The world-class Huize Pb-Zn deposits of Yunnan province,in southwestern China,located in the center of the Sichuan-Yunnan-Guizhou Pb-Zn polymetallic metallogenic province,has Pb+Zn reserves of more than 5 million tons at Pb+Zn grade of higher than 25%and contains abundant associated metals,such as Ag,Ge,Cd,and Ga.The deposits are hosted in the Lower Carboniferous carbonate strata and the Permian Emeishan basalts which distributed in the northern and southwestern parts of the orefield.Calcite is the only gangue mineral in the primary ores of the deposits and can be classified into three types,namely lumpy,patch and vein calcites in accordance with their occurrence.There is not intercalated contact between calcite and ore minerals and among the three types of calcite,indicating that they are the same ore-forming age with different stages and its forming sequence is from lumpy to patch to vein calcites. This paper presents the rare earth element(REE) and C-O isotopic compositions of calcites in the Huize Pb-Zn deposits.From lumpy to patch to vein calcites,REE contents decrease as LREE/ HREE ratios increase.The chondrite-normalized REE patterns of the three types of calcites are characterized by LREE-rich shaped,in which the lumpy calcite shows(La)_N(Ce)_N(Pr)_N≈(Nd)_N with Eu/Eu~*1,the patch calcite has(La)_N(Ce)_N(Pr)_N≈(Nd)_N with Eu/Eu~*1,and the vein calcite displays(La)_N(Ce)_N(Pr)_N(Nd)_N with Eu/Eu~*1.The REE geochemistry of the three types of calcite is different from those of the strata of various age and Permian Emeishan basalt exposed in the orefield.Theδ~(13) C_(PDb) andδ~(18)O_(Smow) values of the three types of calcites vary from-3.5‰to-2.1‰and 16.7‰to 18.6‰,respectively,falling within a small field between primary mantle and marine carbonate in theδ~(13)C_(PDb) vsδ~(18)O_(Smow) diagram. Various lines of evidence demonstrate that the three types of calcites in the deposits are produced from the same source with different stages.The ore-forming fluids of the deposits resulted from crustal -mantle mixing processes,in which the mantle-derived fluid components might be formed from degassing of mantle or/and magmatism of the Permian Emeishan basalts,and the crustal fluid was mainly provided by carbonate strata in the orefield.The ore-forming fluids in the deposits were homogenized before mineralization,and the ore-forming environment varied from relatively reducing to oxidizing.     

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.     

Geology and Isotope Geochemistry of the Yinchanggou-Qiluogou Pb-Zn Deposit, Sichuan Province, Southwest China

The Yinchanggou-Qiluogou Pb-Zn deposit,located in the western Yangtze Block,southwest China,is hosted by the Upper Sinian Dengying Formation dolostone.Ore bodies occur in the Qiluogou anticline and the NS-and NNW-trending faults.Sulfide ores mainly consist of sphalerite,pyrite,galena and calcite,with subordinate dolomite and quartz.Seventeen ore bodies have been discovered to date and they have a combined 1.0 million tons of sulfide ores with average grades of 2.27wt%Zn and 6.89wt%Pb.The δD_(H2O-SMOW) and δ~(18)O_(H2O-SMOW) values of fluid inclusions in quartz and calcite samples range from-68.9‰ to-48.7‰ and 7.3‰ to 15.9‰,respectively,suggesting that H_2O in the hydrothermal fluids sourced from metamorphic water.Calcite samples have δ~(13)C_(PDB) values ranging from-6.2‰ to-4.1‰ and δ~(18)O_(SMOW) values ranging from 15.1‰ to 17.4‰,indicating C and O in the hydrothermal fluids likely derived from a mixed source of metamorphic fluids and the host carbonates.The δ~(34)S_(CDT) values of sulfide minerals range from 5.5‰ to 20.3‰,suggesting that thermal chemical reduction of sulfate minerals in evaporates were the most probable source of S in the hydrothermal fluids.The ~(206)Pb/~(204)Pb,~(207)Pb/~(204)Pb and ~(208)Pb/~(204)Pb ratios of sulfide minerals fall in the range of 18.11 to 18.40,15.66 to 15.76 and 38.25 to 38.88,respectively.The Pb isotopic data of the studied deposit plot near the upper crust Pb evolution curve and overlap with the age-corrected Proterozoic basement rocks and the Upper Sinian Dengying Formation hosting dolostone.This indicates that the Pb originated from a mixed source of the basement metamorphic rocks and the ore-hosting carbonate rocks.The ore geology and C-H-O-S-Pb isotopic data suggest that the YinchanggouQiluogou deposit is an unusual carbonate-hosted,strata-bound and epigenetic deposit that derived ore-forming materials from a mixed source of the underlying Porterozoic basements and the Sinian hosting carbonates.     

东昆仑祁漫塔格早中生代大陆地壳增生过程中的岩浆活动与成矿作用

东昆仑祁漫塔格地区位于青藏高原北缘,为典型的大陆边缘增生造山带,经历了漫长的古生代—早中生代增生造山过程,其中以早中生代岩浆活动与成矿作用最为发育。文章系统总结了区内早中生代侵入岩分布及成因,对与其相关矿床地质、成矿流体特征及成矿物质来源进行分析,进一步探讨了祁漫塔格地区早中生代大陆地壳增生过程中的壳幔混合岩浆活动与成矿作用的关联。研究结果认为,中二叠世—早三叠世以俯冲阶段的侧向增生为主,中-晚三叠世以碰撞-后碰撞阶段的垂向增生为主,与成矿有关的岩浆岩主要为中-晚三叠世石英闪长岩、花岗闪长岩、二长花岗岩、正长花岗岩、花岗斑岩等,以I型、A型花岗岩为主,且多见暗色包体,Sr-Nd-Hf同位素组成表明其源于古陆壳物质的重熔,有地幔物质的参与,由地幔底侵古老陆壳,幔源基性岩浆与壳源花岗质岩浆发生不同程度混合作用而形成。与该时期岩浆活动关系密切的主要为斑岩型铜钼矿床、矽卡岩型铁多金属矿床、层控矽卡岩型铅锌矿床、与碱性花岗岩有关稀有金属矿化等。成矿时代集中于248~210 Ma,成矿流体主要来源于岩浆热液,成矿物质具有壳幔混合来源,区内中-晚三叠世大陆垂向增生过程中的壳-幔岩浆混合作用为区域大规模金属成矿提供大量热能、成矿流体及成矿物质。