Metal mobility during hydrothermal breakdown of Fe-Ti oxides: Insights from Sb-Au mineralizing event (Variscan Armorican Massif,France)

Hydrothermal alteration related to Sb-Au mineralization is widespread in the Variscan Armorican Massif, but mineral replacement reactions are not well characterized, in particular the hydrothermal breakdown of ilmenite-titanohematite. Based on petrography, electron probe micro-analyzer and laser ablation-inductively coupled plasma-mass spectrometer analyses, we document mineralogical change at rock- and mineral-scale and the redistribution of Sb and others trace elements during the recrystallization of ilmenite-titanohematite to hydrothermal rutile. Hydrothermal alteration is mainly potassic with associated carbonation. The replacement mechanism is interpreted to be an interface-coupled dissolution-reprecipitation process. Results show that Mn, Zn, Co, Ni, Sn, Mo and U are released during hydrothermal alteration, whereas Sb and W are incorporated in newly-formed hydrothermal rutile from the hydrothermal fluid. Furthermore, the concentration of Sb evolves through time suggesting a change in fluid composition likely related to an enrichment of fluid in Sb during rutile crystallization. Considering that Fe-Ti oxides breakdown during hydrothermal alteration is common within epithermal and mesothermal/orogenic Au-Sb mineralizing systems, results report in this study yield important constraints about metal mobility and exchanges in hydrothermal gold systems.     

胶东大柳行金矿田庵口金矿床成矿流体与成矿物质来源

庵口金矿床是位于大柳行金矿田东北部的石英脉型中型金矿床,矿体呈脉状产于郭家岭岩体内部的北东东向断裂带内。目前,对该矿床的研究相对较少,为探讨其成矿流体性质与成矿物质来源,文章通过井下观察、岩相学、流体包裹体测温、激光拉曼分析和同位素测试,将该矿床热液成矿期划分为黄铁矿石英阶段(Ⅰ)、石英黄铁矿阶段(Ⅱ)、多金属硫化物阶段(Ⅲ)和碳酸盐阶段(Ⅳ)。流体包裹体研究表明,成矿流体含富液相和富气相包裹体,包裹体气相成分以CO₂为主,少量N₂、CH₄,总体为中低温、低盐度CO₂-H₂O-NaCl体系,成矿早期(Ⅰ阶段)和主成矿期(Ⅱ、Ⅲ阶段)温度变化不大,盐度呈降低趋势,流体演化过程中发生了流体不混溶(沸腾)。H-O同位素测试表明,成矿流体可能主要来源于郭家岭岩体出溶的岩浆水;S、Sr-Nd-Pb同位素示踪显示,成矿物质可能主要来源于重熔活化的下地壳(前寒武纪变质基底),并在向上运移过程中混入了上地壳物质。     

黔西南架底金矿床流体包裹体研究

架底金矿是近年来在黔西南新发现的主要赋存于玄武岩中的大型微细粒浸染型金矿床。为查明其成矿流体特征,探讨流体成矿机制,针对矿床不同成矿阶段采取流体包裹体样品开展工作。根据野外观察和室内分析,架底金矿热液成矿期可分为3个阶段:黄铁矿阶段、烟灰色石英阶段和硫化物阶段,其中烟灰色石英阶段为主要成矿阶段。流体包裹体以NaCl-H₂O和CO₂-NaCl-H₂O型为主,黄铁矿阶段富CO₂包裹体,均一温度（T_h）为211~231℃,盐度（wt）为2.10~7.60（% NaCl equiv）;烟灰色石英阶段见大量NaCl-H₂O和CO₂-NaCl-H₂O型包裹体,均一温度（T_h）为182~218℃,盐度（wt）为1.40~5.90（% NaCl equiv）;硫化物阶段包裹体均一温度（T_h）普遍小于183℃,盐度（wt）为0.90~5.30（% NaCl equiv）。激光拉曼光谱分析显示包裹体中含CO₂、CH₄、N₂、SO₂等气相组分,随着成矿流体均一温度、盐度和密度的不断下降,包裹体中气相组分种类也趋于简单。通过计算成矿流体的ρ、P、pH、Eh和f_O2等物理化学参数,表明成矿环境具有中低温、低盐度、低密度、近中性、相对还原及低氧逸度的特征。流体包裹体组合变化表明成矿作用发生在流体CO₂含量不断降低的过程,主成矿阶段流体混合和区域伸展构造引起流体沸腾作用强烈,大量金属成分（黄铁矿、自然金等）快速沉淀形成金矿体。      

Carbon Enrichment in the Lithospheric Mantle: Evidence from the Melt Inclusions in Mantle Xenoliths from the Hainan Basalts

It is generally believed that the lithospheric mantle and the mantle transition zone are important carbon reservoirs. However, the location of carbon storage in Earth’s interior and the reasons for carbon enrichment remain unclear. In this study, we report CO₂-rich olivine-hosted melt inclusions in the mantle xenoliths of late Cenozoic basalts from the Penglai area, Hainan Province, which may shed some light on the carbon enrichment process in the lithospheric mantle. We also present ...     

Fluid Charging and Paleo-pressure Evolution in the Ledong Slope Zone of the Yinggehai Basin,South China Sea

Large numbers of gas reservoirs have been discovered in overpressure basins. Fluid charging has a close relationship with paleo-pressure evolution, affecting the migration of gas reservoirs. To study fluid charging and the related pressure system, we analyzed burial histories and fluid inclusion(PVTx) simulations and conducted basin modeling of the Ledong Slope Zone in the Yinggehai Basin as an example. On the basis of fluid-inclusion assemblages(FIAs), homogenization temperature(Th), final melt...     

四川雪宝顶钨锡铍矿床流体包裹体研究及其意义

四川雪宝顶钨锡铍矿床产于花岗岩体与三叠系地层大理岩的接触带,赋矿石英脉受大理岩中的劈理破碎带控制。绿柱石与白钨矿中的包裹体可分为熔融包裹体、流体熔融包裹体和流体包裹体3类。流体包裹体又可分为H2O包裹体、CO2包裹体和CO2-H2O包裹体,其中,绿柱石中以富含CO2-H2O包裹体为显著特征。加热时,富H2O相CO2-H2O包裹体完全均一至H2O相,富CO2相CO2-H2O包裹体完全均一至CO2相,而二者的完全均一温度和均一压力一致,表明它们是同期捕获的CO2-低盐水不混溶包裹体组合。与绿柱石相比,白钨矿中CO2-H2O包裹体数量明显减少,H2O包裹体数量增多,成矿压力与成矿温度均有所降低。含CO2流体在花岗岩体与大理岩接触带附近发生流体不混溶和相分离,CO2的出溶使成矿流体中pH值升高,f(O2)降低,导致钨的溶解度降低而沉淀,这是形成白钨矿的主要原因。     

新疆西准噶尔苏云河钼矿床成矿流体和成矿时代

苏云河钼矿位于新疆北部西准噶尔巴尔鲁克山西段,隶属于巴尔鲁克山成矿带,由3个花岗岩体组成,矿体主要位于与岩体接触的凝灰岩地层中。辉钼矿的Re-Os模式年龄为293.3±4.0Ma~296.8±4.3Ma,等时线年龄为294.4±1.7Ma,加权平均年龄为295.0±1.5Ma,表明矿化发生于早二叠世。苏云河钼矿床的石英脉中发育3种类型的包裹体:富液相包裹体、富气相包裹体和含子晶多相包裹体。研究表明,与3个岩体矿化有关的流体具有类似特征,均可以分为3个阶段。早阶段三种类型的包裹体均发育,均一温度491℃,盐度58.6%Na Cleqv,密度1.15g/cm3,具有高温、高盐度、高密度的特征,属Na Cl-CO2-H2O体系。中阶段发育富液相包裹体和富气相包裹体,均一温度为240~443℃,盐度为1.7%~21.0%Na Cleqv,密度为0.38~1.03g/cm3,为中高温、中低盐度、中低密度流体,属Na Cl-CO2-CH4-H2O体系。晚阶段仅发育富液相包裹体,均一温度为153~239℃,盐度为9.6%Na Cleqv,密度为0.81~0.94g/cm3,为中低温、低盐度、中低密度流体,属Na Cl-H2O体系。石英包裹体中水的氢氧同位素研究表明早阶段的成矿流体以岩浆水为主,中阶段和晚阶段为岩浆水和大气水的混合水,并且随着流体演化,大气水所占的比例逐渐升高。除此之外,综合流体包裹体和氢氧同位素地球化学特征表明流体沸腾作用和混合作用是引起苏云河钼矿床矿质沉淀的主要因素。     

矽卡岩岩浆对中国北方某些矽卡岩型矿床形成的制约——来自包裹体激光拉曼分析证据

本文将报道中国北方主要矽卡岩型矿床矿物熔融包裹体和流体-熔融包裹体的激光拉曼分析结果。研究目的是确认这些矿化矽卡岩矿物是否含熔融包裹体和流体-熔融包裹体,获取有关它们相态特征和相组成以及它们的分布状况(是局部的、偶然性的,还是广泛的)的信息。文章对邯邢铁矿、蒙库铁矿和杨家杖子钼矿等9个矿床12块标本中石榴石、辉石和方解石或白云石中23个包裹体进行了共聚焦激光拉曼光谱仪分析。拉曼分析结果表明,所研究的矽卡岩矿物均含熔融包裹体和/或流体-熔融包裹体,它们是岩浆矽卡岩的直接证据。结合本文激光拉曼分析结果、地质背景和其他地区岩浆矽卡岩矿物包裹体测温学研究,对所研究矽卡岩的形成机制和岩浆矽卡岩对中国北方某些矽卡岩型矿床的制约进行了讨论。认为含有熔融包裹体和/或流体-熔融包裹体的矿化矽卡岩系岩浆成因,其分布范围广泛,规模不小。中国北方某些矽卡岩型矿床的时空分布和规模受控于该地区分布的岩浆矽卡岩。希望本文有助于拓宽矽卡岩型矿床成矿规律研究和深部找矿勘探的思路。     

极富CO_2流体的造山型金矿:苏丹哈马迪金矿

哈马迪金矿位于苏丹东北部,矿床产于阿拉伯-努比亚地盾新元古界变质岩系中,属于受剪切带控制的造山型金矿床。金矿体赋存在角闪片岩内近南北向的片理化蚀变带中,围岩蚀变主要为黄铁绢英岩化,以及绿泥石化和碳酸盐化等。在含矿石英细脉中赋存有大量的极富CO2的碳质流体包裹体。这些包裹体几乎不含水,含有少量CH4(XCH4=0~0.10)。脉石英中碳质流体包裹体既有孤立或随机分布的原生包裹体,也有呈线性分布的次生包裹体,最晚期还有次生水溶液包裹体的分布。碳质流体包裹体的三相点(Tm,CO2)范围变化不大(-58.4~-57.0℃),但均一温度(Th,CO2)范围变化较大(-19℃~+29℃)。捕获的P-T条件可由LCO2包裹体的ρ值或Th,CO2值,以及与其伴生的CO2-H2O包裹体最终均一温度Th,TOT值,从有关相图中估算。早期碳质流体包裹体的捕获P-T条件范围为280~360℃、80~320MPa。金矿化发生在变质峰期之后的退变质作用晚期。广泛发育的热液蚀变说明碳质流体并非来自单一的流体源,寄主石英变形很弱也不能解释水从H2O-CO2-盐流体包裹体中优先淋失、残留大量的CO2±CH4包裹体。碳质流体包裹体可能的成因是:在金成矿的退变质时期,来自深部的H2O-CO2-盐流体,由于P-T下降而发生不混溶,H2O在热液蚀变中被大量消耗,而CO2则以碳质流体包裹体的形式被得捕获在脉石英中。