德兴铜厂斑岩铜矿成矿流体演化特征

为探讨成矿流体的特征和演化过程,对德兴铜厂斑岩铜矿床不同蚀变—矿化带石英细脉中的流体包裹体进行详细的岩相学观察、显微测温、显微激光喇曼探针工作.结果显示,德兴铜厂斑岩铜矿主要有三类流体包裹体:富液相包裹体(Ⅰ型),富气相包裹体(Ⅱ型)、多相包裹体(Ⅲ型);成矿早期的Ⅰ型包裹体,主成矿期的Ⅱ型和Ⅲ型包裹体,以及成矿晚期的Ⅰ型包裹体的平均均—温度和平均盐度分别为:481℃,8.1％; 410℃,1.2％;389℃,56％和215℃,3.1％;主成矿期的Ⅱ型和Ⅲ型包裹体的平均均—温度相近,但盐度相差很大,指示了沸腾作用的发生;从早期到晚期,成矿流体呈现温度降低,挥发分逸出的趋势.     

江西德兴朱砂红斑岩铜矿流体包裹体特征及其成矿意义

朱砂红斑岩铜矿位于德兴斑岩铜矿矿集区的西北方向,紧邻铜厂铜矿.本文在前人有关德兴铜矿研究基础上,以铜矿流体包裹体为研究内容,通过野外详细的岩芯采样,室内石英斑晶、石英脉和方解石脉中包裹体测试及数据整理分析后初步发现:朱砂红斑岩铜矿流体包裹体大致可以分成五大类型(富液型包裹体、富气型包裹体、含CO2气液两相型包裹体、含子矿物多相型和固液两相型);相比铜厂整体成矿温度略低,盐度略高;由成矿流体压力47.27～184.47 MPa,推导出成矿深度达2～4 km,以及激光拉曼测试结果——流体中含有CO2、H2S和CH4等挥成份气体,它们可能与Au等元素的运移成矿有关.因此,从包裹体性质推测朱砂红铜矿不只是斑岩铜矿,可能是浅成热液斑岩型铜金矿床.此外,朱砂红矿区成矿流体来源至少有两种:高温岩浆流体和大气降水.伴随流体演化期次大致可以划分出3个成矿阶段:硅酸盐硫化物阶段、石英-硫化物阶段(即主成矿阶段,温度:200～340℃,盐度:2.0％～15％NaCl)、碳酸盐-硫酸盐硫化物阶段.同时,均一温度、盐度及压力等暗示在流体演化和成矿过程中岩浆流体发生过沸腾或不混溶作用.     

德兴铜厂斑岩型铜金矿床热液演化过程

德兴铜矿是中国东部大陆环境最具代表性的大型斑岩铜矿,由朱砂红、铜厂及富家坞三大矿床组成,其中的铜厂矿体以富金而别具特色.在前人研究基础上,本文通过系统的野外观测、详细的岩芯编录和全面的岩相学研究,厘定了铜厂矿床的脉体类型和形成顺序,系统地开展了各类脉体的流体包裹体研究,查明了成矿流体的演化过程,再塑了岩浆-热液矿化过程.初步识别出德兴矿床3组脉体类型,分别记录了三个不同阶段的蚀变-成矿过程:早期A脉分为4类,形成于成矿早期斑岩尚未固结时,伴有大规模的钾化和黑云母化甚至磁铁矿化;中期B脉可分为7类,形成于斑岩体固结后的大规模裂隙事件发育期,B脉石英呈梳状对称生长、黄铁矿以中心线生长;后期D脉共有3类,发育于成矿晚期,系雨水大量加入和硫化物大量淀积产物.观察发现,所有A、B及D脉沉淀过程中,均伴随大量的岩浆流体出溶、热液蚀变、流体挥发等热液活动、各脉均捕获了同体系内富含的热液流体.详细显微镜鉴定表明,各类脉体的脉石矿物石英内发育的大部分包裹体与世界典型斑岩铜矿床的矿化特征相似,从成矿早期A脉到成矿晚期D脉包裹体的类型发生如下变化:早期以LVH(含单子晶或多子晶包裹体发育,包裹体中还见有金属硫化物)+富气相包裹体为主→中期以含单子晶包裹体+富气相包裹体为主,以及含有少量富液相包裹体→成矿晚期,以富液相包裹体+少量富气相包裹体.包裹体显微测温结果总体上指示了温度、压力及热液成分在各类脉体的形成过程的变化规律,从早期到晚期温度和盐度逐渐降低,热液成矿作用明显经历三个阶段:早期岩浆未完全固结,温度达到800～600℃以上,压力较高(140～50MPa),发生强烈的钾硅酸盐化;中期,由于岩浆冷凝结晶,岩体顶部围岩裂隙发育,静岩压力向静水压力发生转换,温度下降到450～550℃,压力陡然从55～40MPa下降至20MPa(B脉);而D脉形成时,发生大规模绿泥石-水云母化,温度下降至350～375℃,压力完全降低至20MPa以下;最后,与成矿作用无关的热液活动了两次,峰值温度分别是320～300℃和180～200℃,形成了无矿碳酸盐脉、石英脉及黑云母. 在成矿过程中,成矿热液也从形成A/B脉时以岩浆热液为主,转变为形成D脉时以雨水、地下水为主.与世界典型斑岩型铜矿床相比,德兴斑岩铜矿床的蚀变-矿化系统基本一致,都由强硅酸盐蚀变带--青磐岩蚀变带--泥岩蚀变带等构成,在不同的蚀变阶段形成了具有特色的不规则形状A脉、脉石矿物梳状对称的B脉及粗颗粒大脉型D脉.德兴铜厂铜金矿各成矿阶段内主要成矿流体特征及其演化过程基本类似于世界典型斑岩矿床.但是,也存在不同之处,在铜厂铜金矿的A、B及D脉都发育了少量CO_2包裹体,表明德兴铜厂成矿过程中CO_2参与成矿作用,世界其它斑岩型矿床或没有报道发育 CO_2 包裹体(杨志明等,2008),或者仅在其中某个阶段发现了少量CO_2包裹体(Harris et al., 2004).CO_2包裹体参与成矿是否有特殊指示意义,须进一步的工作才能得出正确的结论.     

青海省兴海县赛什塘铜矿的斑岩型矿化特征及其找矿前景

青海省兴海县赛什塘铜矿床中局部具斑岩型矿化的特征,该矿区中酸性侵入岩发育并具明显的多期次和多类型.该类铜矿化发生于中-酸性岩浆侵入活动末期的闪长玢岩、花岗闪长斑岩、斜长花岗斑岩、石英斑岩、爆破角砾岩中,围岩蚀变强烈且具分带性.加强对蚀变闪长玢岩、花岗闪长斑岩、斜长花岗斑岩、石英斑岩、爆破角砾岩发育地段的找矿工作,有望实现本区找矿新突破.     

江西德兴地区主要矿床类型、成矿地质征及其因关系

江西德兴地区是中国重要的金属矿产资源聚集地,主要矿床有德兴斑岩铜矿(包括朱砂红、铜厂和富家坞)、金山金矿、银山Pb-Zn-Ag多金属矿和蛤蟆金矿等.这些矿床可以划分为与剪切带有关的金矿和与岩浆热液成矿作用有关的铜金钼铅锌银矿床(如德兴斑岩Cu-Mo-Au矿床和银山Pb-Zn-Ag-Cu-Au矿床).在控矿构造、成矿元素...     

Mineral Deposits Types, Mineralization Features and Genesis Relationship between Jinshan Gold Deposit and Dexing Porphyry Copper Deposit,Northeastern Jiangxi Province, South China

江西德兴地区是中国重要的金属矿产资源聚集地,主要矿床有德兴斑岩铜矿(包括朱砂红、铜厂和富家坞)、金山金矿、银山Pb-Zn-Ag多金属矿和蛤蟆金矿等.这些矿床可以划分为与剪切带有关的金矿和与岩浆热液成矿作用有关的铜金钼铅锌银矿床(如德兴斑岩Cu-Mo-Au矿床和银山Pb-Zn-Ag-Cu-Au矿床).在控矿构造、成矿元素组合、成矿流体来源、矿床地球化学等方面这两类矿床都有明显的差异;二者成矿年龄的差异显示它们是不同地质时期演化的结果.剪切带型金矿(如金山金矿)与斑岩铜矿(德兴铜矿)在成因上没有明显的直接关系,它们非单一同一岩浆系统的产物.     

Geology and Re-Os Geochronology of Mineralization of the Miduk Porphyry Copper Deposit, Iran

The Miduk porphyry copper deposit is located in Kerman province, 85 km northwest of the Sar Cheshmeh porphyry copper deposit, Iran. The deposit is hosted by Eocene volcanic rocks of andesitic–basaltic composition. The porphyry‐type mineralization is associated with two Miocene calc‐alkaline intrusive phases (P1 and P2, respectively). Five hypogene alteration zones are distinguished at the Miduk deposit, including magnetite‐rich potassic, potassic, potassic–phyllic, phyllic and propylitic. Mineralization occurs as stockwork, dissemination and nine generations (magnetite, quartz–magnetite, barren quartz, quartz‐magnetite‐chalcopyrite‐anhydrite, chalcopyrite–anhydrite, quartz‐chalcopyrite‐anhydrite‐pyrite, quartz‐molybdenite‐anhydrite ± chalcopyrite ± magnetite, pyrite, and quartz‐pyrite‐anhydrite ± sericite) of veinlets and veins. Early stages of mineralization consist of magnetite rich veins in the deepest part of the deposit and the main stage of mineralization contains chalcopyrite, magnetite and anhydrite in the potassic zone. The high intensity of mineralization is associated with P2 porphyry (Miduk porphyry). Based on petrography, mineralogy, alteration halos and geochemistry, the Miduk porphyry copper deposit is similar to those of continental arc setting porphyry copper deposits. The Re‐Os molybdenite dates provide the timing of sulfide mineralization at 12.23 ± 0.07 Ma, coincident with U/Pb zircon ages of the P2 porphyry. This evidence indicates a direct genetic relationship between the Miduk porphyry stock and molybdenite mineralization. The Re‐Os age of the Miduk deposit marks the main stage of magmatism and porphyry copper formation in the Central Iranian volcano‐plutonic belt.     

安徽铜陵桂花冲斑岩铜矿围岩蚀变与矿化作用

桂花冲铜矿为安徽铜陵地区新发现的斑岩型铜矿,斑岩体为准铝质高钾钙碱性的花岗闪长斑岩。围岩蚀变与矿化作用是斑岩型矿床成矿过程研究的一项重要内容,对蚀变带岩石开展元素地球化学成分的迁移研究,是分析热液交代蚀变过程的基础。桂花冲铜矿区内围岩蚀变作用比较强烈,蚀变类型主要有钾化、绢云母化、硅化、绿泥石化和碳酸盐化等。蚀变分带比较明显,由内向外依次为钾化带、绢英岩化带和青磐岩化带,矿体主要产于绢英岩化带内。矿化蚀变自早至晚划分为钾长石、石英-绢云母、石英多金属硫化物和碳酸盐4个阶段。蚀变带物质组分迁移结果表明,在蚀变过程中,岩石的主量元素除TiO₂、MnO、MgO外,其他元素迁移量发生了明显改变;微量元素除Sr和Cu外,迁移量变化较小,稀土元素在矿化强的部位亏损,在矿化弱的地带富集。岩体及蚀变带岩石稀土元素球粒陨石标准化配分模式一致,说明岩体与蚀变岩石经历了相同来源流体的交代蚀变,是岩浆流体连续作用的结果。     

德兴斑岩铜矿田两类伊利石的存在及其在蚀变分带中的意义

德兴斑岩铜矿田内存在两种成因类型的伊利石：一是特征的热液蚀变矿物,它是在热液流体 作用过程中斜长石、云母类矿物通过伊利石化过程形成的,其结晶度(IC)和膨胀层含量受携 带矿质的热液流体量控制;二是浅变质作用自身的产物,其结晶度远较小于前者,具2M1 多型,且不含膨胀层,是原始蒙皂石完全伊利石化形成的。作者发现,在斑岩体和接触带内 ,伊利石结晶度小的部位,蚀变程度强,矿化品位也高。     

德兴斑岩铜矿床研究新进展

江西德兴铜矿是中国东部最大的斑岩型铜矿床,前人对该矿床的成矿流体来源及演化方面的研究取得了较为一致的认识,但在含矿斑岩成因、成矿物质来源、成矿环境等其它方面还存在有较大的争论。最新研究成果表明,德兴铜矿的含矿斑岩形成于中侏罗世早期（1702～1710 Ma）古太平洋板块向欧亚大陆俯冲形成的大陆边缘环境下,由俯冲大洋板片（主要为上覆沉积物）部分熔融形成的具高Sr、Sr/Y 和La/Yb 比值特征的高钾钙—碱性熔体,在其上升过程中与岩石圈地幔相互作用所形成。超大型的Cu—Au 多金属成矿作用与岩浆侵入作用几乎同时发生,成矿物质主要由洋片（P MORB）中富含Fe3+ 的岩浆释放出的流体或熔体在上升途中与上覆岩石圈地幔相互作用后从岩石圈地幔中萃取出来。而在晚侏罗世中期（约1535 Ma）,区内转换为由俯冲大洋板片rollback 形成的弧后伸展环境,形成了壳—幔混源成因的闪长质侵入岩脉群,但没有显示出良好的矿化作用;到了早白垩世晚期（1009～1065 Ma）,德兴斑岩铜矿区内发生一次热液成因的Cu（—Au?）成矿作用事件,叠加于原先大规模的主成矿事件之上。     

新疆西天山达巴特斑岩铜钼矿床成矿流体演化

新疆达巴特铜钼矿床位于天山造山带的北缘,赛里木地块的中部,成矿与晚石炭世-早二叠世浅成侵入体有关。对该矿床详细的矿石组构、流体包裹体显微测温和激光拉曼光谱分析揭示,其流体成矿先后经历了辉钼矿-黄铜矿-石英脉(Ⅰ)、无矿石英脉(Ⅱ)、辉钼矿-石英脉(Ⅲ)和方解石-石英脉(Ⅳ)等4个阶段。从早到晚不同阶段,包裹体均一温度集中分布在336~414℃、276~393℃、221~396℃、192~287℃,盐度为(4.5~9.9)%Na Cleq、(1.6~8.4)%Na Cleq、(1.2~45.6)%Na Cleq、(1.6~7.5)%Na Cleq,密度为0.57~0.76 g/cm3、0.54~0.80 g/cm3、0.51~1.11 g/cm3、0.76~0.91 g/cm3,随成矿流体温度、盐度降低,密度渐升,还原性增强。Ⅰ、Ⅲ阶段都发育矿化,包裹体具有明显的沸腾特征,且气相成分中均发现CO2,表明Ⅰ和Ⅲ阶段的流体沸腾可能导致金属沉淀,且CO2对金属运移可能具有重要作用。压力估算得到达巴特矿床Ⅰ、Ⅱ、Ⅲ、Ⅳ阶段脉体的成矿深度分别为0.5~1.1 km、0.3~1.0 km、0.5~1.0km、0.4~1.0km。矿体矿石、围岩蚀变和流体包裹体具有斑岩型矿床的特点。结合前人资料,认为达巴特为一典型斑岩型矿床。     

Re-Os Geochronology of Molybdenite from Yuanzhuding Porphyry Cu-Mo Deposit in South China

The Yuanzhuding porphyry Cu-Mo deposit, discovered in 2008, is located within the southern segment of the Chenzhou-Huaiji fault belt, South China. The deposit is hosted within the Upper Cambrian neritic facies sandstone and shale formation that is the strata of the axis and wings of within the Yuanzhuding anticline. Both of the porphyry and exo-contact zone contain Cu-Mo mineralization. Economic orebodies occur mainly in the exo-contact zone around the porphyry. We dated 11 molybdenite samples obtained from two borehole cores of the deposit, using the Re-Os method. Analyses of eight molybdenite samples from borehole ZK12-112 yield a Re-Os isochron age of 157.3 ± 4.3 Ma (2σ), and analyses of 11 samples from boreholes ZK12-112 and ZK16-104 yield a Re-Os isochron age of 155.6 ± 3.4 Ma (2σ). These isochron ages are within the error of the Re-Os model ages, demonstrating that the age results are reliable and that the Yuanzhuding porphyry Cu-Mo deposit formed during the late Middle Jurassic. The formation age of the Yuanzhuding Cu-Mo deposit is similar to the age of intermediate-acid rocks and W-Sn polymetallic deposits along the Chenzhou-Huaiji fault belt. This concordance suggests the same geodynamic process to the igneous activity and related mineralization, raising the potentiality of the porphyry Cu-Mo mineralization in the belt.     

西藏多不杂斑岩铜金矿床地质与蚀变

[摘 要]西藏多不杂斑岩铜金矿是近年来新发现的一个矿床,位于班公湖-怒江成矿带西段。多不杂矿床内发育三期花岗闪长斑岩,侵入到侏罗系曲色组变砂岩中,北东向断层是多不杂矿床的主要控岩断层。多不杂矿床由内向外发育钾化、绢英岩化、青磐岩化,钾化主要发育于第一期花岗闪长斑岩出露区域,绢英岩化环绕钾化带发育,并叠加在钾化带之上,青磐岩化在矿床西侧的玄武安山岩和南侧的火山角砾岩中呈团块状发育。多不杂矿床的的铜矿化以黄铜矿矿化为主,金矿化与铜矿化密切共生。黄铜矿化主要发育于第一期花岗闪长斑岩及其与变砂岩接触带内,第一期花岗闪长斑岩为多不杂矿床的成矿斑岩。     

青海纳日贡玛斑岩铜钼矿床地球化学特征及成矿作用

纳日贡玛矿床是我国著名“三江”北段成矿区带中最典型的斑岩型Cu-Mo矿床。在总结矿床地质特征的基础上,通过系统总结该矿床的矿床地球化学及成矿作用相关资料,得出以下结论：①纳日贡玛矿床形成于喜马拉雅运动早期,纳日贡玛铜钼矿床成矿物质主要来自花岗斑岩体,成矿花岗斑岩源于下地壳;成矿流体为岩浆期后热液,矿床硫是由岩浆硫(为主)和成矿流体萃取围岩中的硫所组成的1种混合硫源。矿床的形成与青藏高原东缘区域构造和应力转换密切相关。②基于已有认识,建立了纳日贡玛铜钼矿床的成矿理想模式,认为矿体形成背景可能为逆冲挤压推覆条件下的局部拉张环境,拉张降压以及围岩的性质导致了该矿床富钼贫铜现况;矿床热液蚀变发育,绢云岩化与矿体较为密切,钾化带范围小,与成矿关系不大;纳日贡玛矿区剥蚀程度大,纳日贡玛矿床东南部剥蚀程度相对较小,在东南部外围找矿过程中,应该兼顾矽卡岩型矿体。     

Relationship Between Hydrothermal Alteration Index and Geological Attributes at Chuquicamata Cu–Mo Porphyry Deposit,Chile

The distribution of mineral zones, hydrothermal alteration assemblages and ore associations are important geological attributes of the Chuquicamata Porphyry Cu–Mo deposit. The development and morphology of these attributes were influenced by syn‐mineralization structures with later modification of post‐mineralization tectonism to yield the present day form. In this work we evaluate the elemental mass transfer index due to hydrothermalism by using Pearce Element Ratios, using a database of 1110 samples consisting of elemental concentrations by chemical analysis. We study the relationship of the aforementioned index with the geological attributes in the porphyry as well as evaluate the type of information that the index provides according to its distribution, magnitude and variability. The magnitudes of the alteration index are organized into deciles, each of which represents a source of information, or macrostate. Within these, the geological attribute, or microstate, has a probability to participate that depends on the possible categorization of a particular attributes. The amount of information or uncertainty that each geological attribute provides to each decile of the distribution of the alteration index is determined by measuring the value of entropy. The results indicate that this distribution is controlled by the geometric–kinematic properties of syn‐mineralization structures that generate the primary pattern related to potassic alteration that develops in the hanging wall of the East Shear Zone. Subsequently the shape of the potassic alteration is modified by the kinematic effect imposed by the Americana and Estanques Blancos faults, and this broadly defines the geometry of the Qz–Mo event and the shape of the phyllic alteration. In addition, the sinistral‐inverse shear of the West Fault Zone allows the construction of an enriched blanket and also generates the drag fold that is characteristically observed in the south wall of the mine. All of the above events combine to yield the final geometry of the geological attributes that controls the shape and magnitude of the alteration index in the porphyry. The magnitude of the alteration index is mainly driven by the potassic and phyllic alteration stages. Potassic alteration is dominant in the first four deciles, while phyllic alteration is dominant in the last six deciles. Supergene mineralization attributes contribute discreetly to the average magnitude of the alteration index for each decile. The distribution of the probability of participation of the geological attributes in the distribution of the alteration index suggests that in the potassic alteration, biotite and green‐gray sericite facies contribute to strengthen the index in an associated manner, while in the phyllic alteration, the Qz–Ser textural type is the most significant.     

Petrogenesis of Adakitic Porphyries in an Extensional Tectonic Setting, Dexing, South China: Implications for the Genesis of Porphyry Copper Mineralization

The Dexing adakitic porphyries (quartz diorite–granodioriteporphyries), associated with giant porphyry Cu deposits, arelocated in the interior of a continent (South China). They exhibitrelatively high MgO, Cr, Ni and Sr contents, high La/Yb andSr/Y ratios, but low Yb and Y contents, similar to adakitesproduced by slab melting associated with subduction. However,they are characterized by bulk Earth-like Nd–Sr isotopecompositions (_Nd(t) = –1·14 to +1·80 and(⁸⁷Sr/⁸⁶Sr)_i = 0·7044 – 0·7047), and highTh (12·6–27·2 ppm) contents and Th/Ce (0·19–0·94)ratios, which are different from those of Cenozoic slab-derivedadakites. Sensitive High-Resolution Ion Microprobe (SHRIMP)geochronology studies of zircons reveal that the Dexing adakiticporphyries have a crystallization age of 171 ± 3 Ma.This age is contemporaneous with Middle Jurassic extension withinthe Shi-Han rift zone, and within-plate magmatism elsewherein South China, indicating that the Dexing adakitic porphyrieswere probably formed in an extensional tectonic regime in theinterior of the continent rather than in an arc setting. Theirhigh Th contents and Th/Ce ratios, and Middle Jurassic age,argue against an origin from a Neoproterozoic (1000 Ma) stalledslab in the mantle. Taking into account available data for theregional metamorphic–magmatic rocks, and the present-daycrustal thickness (31 km) in the area, we suggest that the Dexingadakitic porphyries were most probably generated by partialmelting of delaminated lower crust, which was possibly triggeredby upwelling of the asthenospheric mantle due to the activityof the Shi-Hang rift zone. Moreover, the Dexing adakitic magmasmust have interacted with the surrounding mantle peridotiteduring their ascent, which elevated not only their MgO, Cr andNi contents, but also the oxygen fugacity (fO₂) of the mantle.The high fO₂ could have induced oxidation of metallic sulfidesin the mantle and mobilization of chalcophile elements, whichare required to produce associated Cu mineralization. Therefore,the Cu metallogenesis associated with the Dexing adakitic porphyriesis probably related to partial melting of delaminated lowercrust, similar to the metallogenesis accompanying slab melting. KEY WORDS: adakite; lower crust; delamination; porphyry copper deposit, South China     

基于红外光谱技术研究云南普朗斑岩铜矿的蚀变和矿化特征

近年来红外光谱技术作为一种绿色、快速、无损、精确探测矿物的技术手段而倍受关注,针对斑岩型矿床蚀变矿物高度叠加、蚀变分带界线不明显、细粒蚀变矿物多、黏土蚀变矿物多等特征,该技术在蚀变矿物识别和勘探信息解读等方面优势突出。本文应用红外光谱技术对云南普朗斑岩铜矿区钻孔ZK1801岩心进行矿物识别和蚀变分带划分的研究,识别出钾硅酸盐化带、绿帘石-绿泥石化带、绿泥石-伊利石化带、石英-伊利石化带和泥化带。研究表明:普朗铜矿整个钻孔的蚀变矿物主要有石英、钾长石、绢云母、绿泥石、绿帘石、高岭石、蒙脱石、伊利石等;根据矿化特征,发现铜矿体广泛赋存在钾硅酸盐化带和绿帘石-绿泥石化带中,与矿化关系密切的蚀变矿物"石英+钾长石+绢云母"和"绿帘石+绿泥石",可以作为普朗矿床勘查的标型蚀变矿物组合;研究区广泛发育的绢云母Al—OH波长随钻孔深度增加而逐渐从2210～2205nm减小到2202～2198nm, Al—OH波长2210～2205nm(长波绢云母)与矿化关系密切,可以作为普朗矿床勘查的指示信息。     

江西德兴斑岩铜钼矿床流体包裹体子矿物SEM-EDS 研究及其对成矿流体性质的制约

江西德兴斑岩铜钼矿床Q+Py±Cp±Cc脉、(黄铁)绢英岩和Q+Py+Mo±Cp脉中发育大量多相(透明、暗色子矿物)包裹体。本文以详细的显微观察和流体包裹体岩相学观察为基础,利用SEM-EDS(扫描电镜-X射线能谱仪)对多相包裹体内的子矿物进行了系统的鉴定。分析结果表明,Q+Py±Cp±Cc脉石英中发育的透明子矿物包括绢云母、石盐、水氯镁石、白云石、铁氯化物、磷灰石和含稀土元素磷酸盐;暗色子矿物包括赤铁矿、铁氧化物和黄铜矿。(黄铁)绢英岩石英和黄铁矿中透明子矿物包括石盐、(硬)石膏、绢云母、硫酸镁、菱镁矿、六水泻盐和(Fe、Cu、Mg)碳酸盐和硫酸盐,暗色子矿物包括磁铁矿、赤铁矿、金红石和黄铜矿;Q+Py+Mo±Cp脉石英包裹体中发育的子矿物相对较少,透明子矿物包括石盐、菱铁矿和钾长石;暗色矿物为赤铁矿。它们中发育种类繁多的子矿物,表明热液的化学成分非常复杂,多种盐类以及高氧化态子矿物出现指示流体具有高盐度-高氧化态的特征。此外,还鉴别出了黄铜矿、赤铁矿和磁铁矿等金属矿物,这表明热液含有丰富的成矿物质,这些成矿物质随物理化学条件的变化以黄铜矿等金属矿物从热液中沉淀下来,形成了矿床内的主要矿体。结合蚀变矿物组成观察,我们认为Q+Py±Cp±Cc脉、(黄铁)绢英岩和Q+Py+Mo±Cp脉中子矿物组成很可能不代表原始流体的化学成分,因为它们在很大程度上受到了热液蚀变作用的影响,围岩矿物由于水-岩反应被分解,同时释放出Na、Ca、Mg、Fe等元素进入热液,形成了上述种类多样的子矿物。通过流体包裹体岩相学观察发现,(黄铁)绢英岩和中Q+Py+Mo±Cp脉含石盐多相包裹体通常与富气包裹体或者CO₂包裹体紧密共生,这表明热液在被捕获前发生了相分离(或沸腾)作用,而这一过程必然会导致富液包裹体盐度的升高,因此不能排除这些高盐包裹体是由中低盐度流体发生相分离而形成的可能性。Q+Py±Cp±Cc脉中发育的稀土子矿物指示成脉流体具有高盐度-低pH-含CO₂的特征,而这类子矿物在(黄铁)绢英岩和Q+Py+Mo±Cp脉中不发育的原因可能是CO₂与液相发生了相分离作用。     

云南普朗斑岩铜矿蚀变带成矿流体特征及其成矿意义

云南普朗铜矿位于义敦—中甸岛弧带南缘,是近年来我国发现的一个大中型斑岩铜矿床。该矿床具有典型的斑岩铜矿蚀变分带,由中心向外依次为钾硅化带、绢英岩化带、青盘岩化带。对矿区不同蚀变带中的石英流体包裹体进行了岩相学观察、均一温度测量和激光拉曼探针成分分析。均一温度测量结果表明,从普朗斑岩铜矿床钾硅化带到绢英岩化带再到青盘岩化带,成矿流体的平均均一温度从274.4℃到236.4℃再到203.0℃,呈明显下降趋势,可能与天水参与成矿有关。同时,激光拉曼探针成分分析结果表明,普朗斑岩铜矿床矿化期间的成矿流体属于富硫富氯流体,这种温度较高且富硫富氯的成矿流体在钾硅化带和绢英岩化带发生矿化作用将导致成矿物质强烈富集成矿。     

Hydrothermal Alteration Related to Silver Mineralization at the Iwami Silver Deposit,Shimane Prefecture,Japan

The Iwami epithermal silver deposit consists of Ag-Cu veins in a dacitic intrusive body at the deep portion of the Eikyu area, and veinlets with disseminated Ag mineralization in dacitic tuff breccia at a shallow portion of the Fukuishi area. Hydrothermal alteration associated with the silver mineralization is characterized by intense potassium metasomatism with oxidizing conditions. An illite zone occurs around the pathways of uprising fluids in both the Eikyu and Fukuishi areas. It grades laterally into the illite/smectite zone, which is surrounded by a broad smectite zone. Because of boiling, abundant adularia associated with silver mineralization overlaps on the altered tuff breccia in the Fukuishi area. The alteration zoning suggests that the western Eikyu area and the eastern Fukuishi area belong to a single hydrothermal system. The data of fluid inclusion microthermometry indicate that the temperatures range 220–270°C, and salinities range 5–7 wt percent NaCl equivalent for the silver mineralization at the upper portion in the Eikyu area and the lower portion in the Fukuishi area. Radiometric ages for volcanic rocks in the area range from 2.19 to 1.64 Ma, and the dacitic intrusion formed at approximately 1.6 Ma. The silver-dominant mineralizing hydrothermal fluids system was active around 1.44 to 1.07 Ma, which formed the Eikyu Ag-Cu veins at depth, and the Fukuishi Ag ores at the shallower portion.