西天山达巴特斑岩型铜矿床流体地球化学特征和成矿作用

本文对西天山地区达巴特斑岩铜钼矿床矿石中石英的流体包裹体进行了均一法和冷冻法测温,对相应的石英单矿物进行了氢氧同位素测定,据此判断了成矿流体的来源和成矿物理化学条件。结果表明含铜钼矿石中的流体包裹体主要为气液两相包裹体和含子矿物三相包裹体,不同样品中同类包裹体具有基本一致的均一温度、子矿物溶化温度、冰点、盐度和密度值, 数据显示成矿流体均呈中温低盐度的特点。矿石氢氧同位素组成表明矿床的成矿流体属于岩浆水范畴,而且具有深部来源甚至幔源的可能性。根据矿体主要分布在火山机构南北两侧与地层的接触带及其内发育的断裂构造中这一空间关系,结合流体包裹体测温结果,推测尽管该矿床成矿流体具有深源特征,但成矿作用发生在中浅部环境,成矿与火山机构最晚期的花岗斑岩具有密切的成因关系。     

内蒙古呼盟地区甲乌拉银铅锌矿床流体包裹体与成矿的关系

通过对甲乌拉银铅锌矿床矿物中流体包裹体成分的含量、温度、压力测定,简述了包裹体特征与成矿的关系     

Caractérisation des paragenèses et des paléocirculations fluides dans l'indice d'or de Bleı̈da (Anti-Atlas,Maroc)Characterization of the paragenesis and the fluid palaeo-circulations in the gold showings of Bleida (Anti-Atlas,Morocco)

The gold showings at Bleida are hosted in Late Pan-African N50–80 °E quartz–hematite–chlorite 1 tension lenses that are related to the activity of major sinistral sub-east–west thrusts. Ores result from three superimposed stages of fluid migration. Gold occurs in microcracks offsetting the earlier minerals. Fluids evolved from COHN compositions with a saline component to boiling aqueous fluids. Pressure and temperature decreased from 50 MPa and 300 °C to less than 4 MPa and 150 °C. Thus, the gold showings at Bleida were formed in a typical geothermal (epithermal) setting, likely controlled by the Late Pan-African magmatism. To cite this article: A. Barakat et al., C. R. Geoscience 334 (2002) 35–41     

黑龙江乌拉嘎金矿的次火山岩浆-热液成矿:熔体-流体包裹体证据

黑龙江乌拉嘎金矿是我国陆相火山岩区的重要金矿之一。构造位置处于古亚洲构造域与滨太平洋构造域交接复合部位的东北缘,矿体主要分布于团结沟斜长花岗斑岩接触带部位的隐爆角砾岩带和黑龙江群变质岩的层间裂隙中。斜长花岗斑岩的石英斑晶中发育3类包裹体:熔体包裹体、原生的L-V包裹体(及少量的L-V-S包裹体)和次生的L-V包裹体。玻璃质熔体包裹体相当于酸性殘浆的成分(SiO2达69.5%～73.8%),其捕获温度大于800℃。石英斑晶中次生L-V包裹体均一温度集中在210～350℃、盐度5%～7%NaCleqv,代表了次火山岩浆热液的特征,与黄铁矿-早期白色玉髓状石英阶段中Q1的包裹体均一温度范围很接近,而盐度略高于白色玉髓状石英Q1的。乌拉嘎金矿的金成矿可划分3个成矿阶段,发育盐水溶液包裹体:(1)黄铁矿-早期白色玉髓状石英阶段,包裹体均一温度为154～355℃,集中在190～330℃,盐度为1.3%～8.2%NaCleqv,密度为0.53～0.88g/cm3。(2)烟灰色玉髓状石英-多金属硫化物阶段,石英中包裹体均一温度为159～196℃,集中在170～190℃,盐度为2.2%～3.2%NaCleqv,密度0.79～0.92g/cm3。(3)碳酸盐-石英阶段,方解石中包裹体均一温度集中在170～270℃;盐度0.5%～2.9%NaCleqv。成矿流体以中低温、低盐度、贫CO2的盐水体系为特征,与国内外陆相火山-次火山热液矿床十分相似。石英斑晶中熔体、流体包裹体及其共存反映了次火山岩浆活动晚期,由硅酸盐熔体通过不混溶产生含矿的盐水溶液的可能,说明了金成矿与斑岩的成因联系,乌拉嘎金矿应该属于陆相火山-次火山活动有关的中低温浅成热液金矿床。     

Mechanism of mineralization in the Changjiang uranium ore field,South China: Evidence from fluid inclusions,hydrothermal alteration,and H–O isotopes

The Changjiang uranium ore field, which contains >10,000 tonnes of recoverable U with a grade of 0.1–0.5%, is hosted by Triassic two-mica and Jurassic biotite granites, and is one of the most important uranium ore fields in South China. The minerals associated with alteration and mineralization can be divided into two stages, namely syn-ore and post-ore. The syn-ore minerals are primarily quartz, pitchblende, hematite, hydromica, chlorite, fluorite, and pyrite; the post-ore minerals include quartz, calcite, fluorite, pyrite, and hematite. The fluid inclusions of the early syn-ore stage characteristically contain O₂, and those of the late syn-ore and post-ore stage contain H₂ and CH₄. The fluid inclusions in quartz of the syn-ore stage include H₂O, H₂O–CO₂, and CO₂ types, and they occur in clusters or along trails. Homogenization temperatures (T_h) for the H₂O–CO₂ and two-phase H₂O inclusions range from 106 °C to >350 °C and cluster in two distinct groups for each type; salinities are lower than 10 wt% NaCl equiv. The ore-forming fluids underwent CO₂ effervescence or phase separation at ∼250 °C under a pressure of 1000–1100 bar. The U/Th values of the altered granites are lowest close to the ore, increase outwards, but subsequently decrease close to unaltered granites. From the unaltered granites to the ore, the lowest Fe₂O₃/FeO values become lower and the highest values higher. The REE patterns of the altered granites and the ores are similar to each other. The U contents of the ores show a positive correlation with total REE contents but a negative correlation with LREE/HREE ratios, indicating the pitchblende is REE-bearing and selectively HREE-rich. The δEu values of the ore show a positive correlation with U contents, indicating the early syn-ore fluids were oxidizing. The δCe values show a negative correlation, indicating the later mineralization environment became reducing. The water–rock interactions of the early syn-ore stage resulted in oxidization of altered granites and reduction of the ore-forming fluids, and it was this reduction that led to the uranium mineralization. During alteration in the early syn-ore stage, the oxidizing fluids leached uranium from granites close to faults, and Fe₂O₃/FeO ratios increased in the alteration zones. The late syn-ore and post-ore alteration decreased the Fe₂O₃/FeO ratios in the alteration zones. The δ¹⁸O_W–SMOW values of the ore-forming fluids range from −1.8‰ to 5.4‰, and the δD_W–SMOW values range from −104.4‰ to −51.6‰, suggesting meteoric water. The meteoric water underwent at least two stages of water–rock interaction: the first caused the fluids to become uranium-bearing, and the second stage, which was primarily associated with ore-bearing faults, led to uranium deposition as pitchblende, accompanied by CO₂ effervescence.     

河南省新县姚冲钼矿床流体包裹体研究

河南省新县姚冲钼矿床产于大别造山带,属于陆-陆碰撞体制的斑岩型矿床,其流体成矿过程可以分为早、中、晚三个阶段,分别以石英+钾长石±黄铁矿±磁铁矿、石英±钾长石+辉钼矿±其他硫化物和石英±碳酸盐±萤石组合为标志.热液石英和萤石中发育纯CO2包裹体(PC型)、CO2-H2O型包裹体(C型)、水溶液包裹体(W型)和含子晶多相包裹体(S型).早阶段石英中发育纯CO2包裹体、CO2-H2O型包裹体和含子晶多相包裹体,中阶段的石英则发育CO2-H2O型包裹体、水溶液包裹体和含子晶多相包裹体,在晚阶段的无矿石英脉中发育水溶液包裹体和少量的CO2-H2O型包裹体,石英-碳酸盐-(萤石)脉石英与萤石中只发育水溶液包裹体.早阶段流体包裹体的均一温度为277～ 380℃,集中于300～ 360℃,盐度变化于3.0％～10.3％ NaCleqv之间.中阶段包裹体均一温度介于185 ～ 351℃之间,集中在260～ 320℃,盐度介于2.4％ ～9.3％NaCleqv;晚阶段包裹体均一温度为139 ～245℃,盐度介于0.7％ ～6.3％ NaCleqv之间.中阶段多相包裹体中常见黄铜矿和其他透明子矿物,表明流体具有还原性、过饱和的特征,是矿石矿物沉淀的主要阶段.估算早、中阶段流体捕获压力分别集中于47 ～ 131MPa和26 ～118MPa,所对应的成矿深度分别约为4.7km和2.6～4.2km.上述流体包裹体的研究表明姚冲钼矿床的初始成矿流体具有高温、高盐度、富CO2的特征,同时预测了深部找矿潜能.     

孟加拉盆地东部褶皱带差异构造变形及成因

基于野外地质调查和地震资料分析,证实了孟加拉盆地东部褶皱带发育底部和中部两套滑脱层。底部滑脱层在整个褶皱带均发育,而中部滑脱层仅发育于北段—中段的陆上和陆架区,在中段的陆坡-洋盆区及南段则不发育。中部滑脱层的发育受古陆坡富泥沉积控制。北段—中段主要发育滑脱褶皱及被断层突破的滑脱褶皱,而南段主要发育泥底辟和泥火山构造。孟加拉盆地东部褶皱带滑脱层系及构造样式的差异变形特征主要受区域挤压作用、沉积作用以及地层流体超压等方面存在着差异的共同影响。     

共生黑钨矿与石英等多种矿物中流体包裹体的红外显微测温对比研究——以江西西华山石英脉钨矿床为例

西华山钨矿床是一个产于燕山期花岗岩中的大脉型钨矿床。已有百余年的开采史。但在矿床成矿条件和成矿流体性质等方面一直存在不同认识。作者利用红外显微镜及其它相关设备,对西华山矿床不同中段样品中的黑钨矿、锡石、绿柱石、黄铁矿、闪锌矿、石英和萤石中的流体包裹体进行了详细对比研究。结果显示,蚀变花岗岩中造岩石英只见次生气液包裹体,晶洞水晶中只有原生包裹体,而云英岩石英中原生、次生包裹体均较发育。黑钨矿中以原生气液包裹体为主,在早期结晶的黑钨矿中还有较多的硅酸盐熔融包裹体,而晶洞中的黑钨矿和水晶一样——只有原生气液包裹体。绿柱石中除了硅酸盐包裹体外,主要是气液包裹体(多为次生)。其它锡石、黄铁矿、闪锌矿和萤石等都只有气液包裹体(原生或次生)。研究结果表明,西华山钨矿床的初始成矿流体是一种岩浆——热液过渡性流体,尔后才演变成单一的热水溶液,在这一过程中黑钨矿、黄铁矿、闪锌矿、萤石和石英等矿物不断晶出。矿床总的成矿温度大致为700~200℃,压力约为160~200MPa。各种气液包裹体的盐度主要为5.0%~10%Na Cleqv。文中还对这些数据的地质意义以及对脉钨矿床流体包裹体研究和数据解释中的某些问题进行了较深入的讨论。     

金属矿床的成矿流体成分和流体包裹体

自然界中的成矿流体按其主要成分,可分为:(1)岩浆,即形成岩浆矿床的岩浆;(2)以H2O为主的流体(含Na Cl);(3)以CO2为主的流体。地壳中的流体类型很多,只有含一定金属元素含量的,并且达到一定浓度时才称为金属矿床的成矿流体。基于对矿床中流体包裹体和天然成矿流体中金属种类和含量的测定,这些金属矿床的成矿流体按金属元素含量可以分为五组,成矿流体可以来自岩浆、岩浆热液、大气降水、盆地卤水和变质流体等地质环境。     

安徽铜陵朝山金矿床流体包裹体研究

朝山金矿床是狮子山矿田内的热液交代型金矿床,在成因上与燕山期的白芒山辉石闪长岩有关.通过采集发育在不同深度下的含金黄铁矿-石英一方解石脉样品,进行流体包裹体岩相学观察和显微测温发现,石英和方解石中均捕获了富气相、富液相的两相水溶液包裹体和含子晶的三相水溶液包裹体,以上三种类型包裹体的均一温度统计峰值分别出现于315～335℃和255～275℃,盐度的统计峰值出现于17.50%～22.50%NaCl eq.和32.50%～37.50%NaCl eq.之间.激光拉曼探针分析表明,石英中流体包裹体的气相成分以水蒸汽为主,伴有少量CO2,可能含有CH4.流体的H、O同位素组成具确岩浆水特征.上述研究表明.朝山金矿成矿流体经历了相态变化,发生了不均匀捕获.受燕山期岩浆作用影响,狮子山矿田内的铜、金成矿在时空上具有一定联系,成矿流体运移的过程中,主要发生了相分离、气相液化和减压沸腾作用,可能是形威铜、金矿化分带的重要原因.