A reconnaissance of Cu isotopic compositions of hydrothermal vein-type copper deposit Jinman,Yunnan, China

The Jinman deposit is a low-temperature hydrothermal vein-type copper deposit, which occurs along faults and fractures within Middle Jurassic sandstone and mudstone units of the Lanping-Simao Mesozoic-Cenozoic basin of Yunnan Province. In this note, we report for the first time the Cu isotopic compositions of Cu-sulfides from the Jinman deposit. The data show large variations and low δ⁶⁵Cu values of -3.70‰ to +0.30‰, which are in sharp contrast to the δ⁶⁵Cu values of high-temperature magmatic-hydrothermal copper deposits (-0.62‰ to +0.40‰) and the modern ocean-floor massive sulfide deposits (-0.48‰ to +1.15‰). It is suggested that the Cu isotope fractionation at Jinman is affected mainly by the following factors, i.e. a low temperature of ore formation (150—286℃); a sedimentary source for ore materials; various stages of ore deposition; and involvement of organic matter in the ore-forming processes.     

Helium isotope compositions of Machangqing copper deposit in western Yunnan, China

Helium isotopic composition of inclusion fluid in pyrites from Machangqing copper deposit, China, has been measured. The measurements, with³He/⁴He ratios ranging from 0.46–2.08 Ra, indicate that the helium in ore-forming fluid is a mixture of crust and mantle, and are consistent with the fact that the parental magma responsible for the formation of ore-forming fluid of the deposit is of crust-mantle provenance.     

滇西澜沧江断裂两侧成矿流体性质对比

处在印度-亚洲大陆主碰撞带南东侧的“三江”地区是世界上著名的成矿带之一,其中澜沧江断裂为一深切入地幔的超岩石圈断裂,不少学者认为其两侧为截然不同的地质单元,成矿地质背景不同,成矿流体性质亦有差别,具有不同的成矿模式。笔者着眼于滇西地区,以澜沧江断裂为界,其东西两侧各选取了位于兰坪盆地的白秧坪铜银多金属矿及保山地块的核桃坪铅锌矿等典型矿床,通过研究发现,两侧流体均为中低温（80～331℃）中等密度（0.48～1.11g/cm3）流体,其形成压力差别不大,成矿作用均发生在较浅成的环境。流体包裹体数据显示,两侧成矿流体主要由大气降水演化而来且均具有地幔流体混入的特点,性质上存在着极大的相似性,故认为两侧矿床是在印度-亚洲板块闭合之后才逐渐形成。     

西藏谢通门县雄村铜(金)矿矿石物质成分研究及其意义

西藏谢通门县雄村铜(金)矿是新发现的超大型细脉浸染型铜(金)矿.通过详细的岩石学、矿石学研究,表明矿石类型主要分为氧化矿石、次生硫化物矿石和细脉浸染状硫化物矿石三大类型.矿石主要为细脉浸染状.主要金属矿物为黄铜矿、黄铁矿、磁铁矿、磁黄铁矿,其次是辉铜矿等.主要非金属矿物为石英,约占矿物总量的60%～70%;其次是红柱石、钾长石、斜长石、黑云母、白云母、绢云母、绿帘石、石榴子石等.矿石主成矿元素以Cu为主,伴生有用组分为Au,Ag,Zn和Pb等.     

云南普朗超大型斑岩铜矿特征及成矿模型

普朗斑岩铜矿床位于义敦岛弧带南端,是中国目前可以确定的印支期斑岩铜矿床的典型代表.矿床产于由石英闪长玢岩、石英二长斑岩小岩株组成的复式岩体中,通过野外观察和典型地质体的辉钼矿Re-Os年龄、黑云母Ar/Ar年龄和K-Ar年龄测定,确定成矿年龄为(213±3.8)～(216.0±1) Ma,为晚三叠世诺利期,表明普朗斑岩铜矿床的成矿作用在印支期完成.含矿岩体蚀变分带明显,由中心向外发育强硅化带(局部)→钾长石、黑云母化带→石英、绢云母化带→青磐岩化带(局部发育伊利石-碳酸岩化带).工业矿体主要产于石英二长斑岩中的钾长石、黑云母化带和石英、绢云母化带.矿床具有斑岩铜矿中下部细粒状浸染、中上部细网脉状浸染和顶部围岩中产出大脉状矿体的"三层楼"模式.其斑岩体、元素组合及矿化特征与蒙古的欧玉·陶勒盖斑岩铜矿可以对比,资源潜力巨大.     

Strontium isotopic signature of hydrothermal sedimentation from Early Cambrian barite deposits in east Guizhou,China

The ore genesis model for barite deposits in east Guizhou Province has been in dispute and the major debate focuses on whether they are product of the submarine hydrothermal sedimentation. This note presents new strontium isotope data from 19 samples of Dahebian and Yuping barite deposits, and their ^87Sr/^86Sr ratios are significantly lower than that of the coeval seawater. The ^87Sr/^86Sr ratios of 17 samples out of 19 samples rang from 0.708310 to 0.708967, indicating that they might be related to the mantel admixture. Two isotopic ratios in this study are higher than those of coeval seawater (0.7090), collected from late-stage barite mineral vein of interpenetrative strata and a barite nodule bearing hypidiomorphic granular pyrite, which indicates that they might be related to the continental admixture. The study provides Sr isotopic evidence not only for the submarine hydrothermal exhalative genesis of Dahebian and Yuping barite deposits, but also for distinguishing the barite mineralization of late stage.     

Sm-Nd isotope dating of hydrothermal calcites from the Xikuangshan antimony deposit,Central Hunan

The research on Samarium-Neodymium isotope systematics of hydrothermal calcites from the Xikuangshan antimony deposit, Central Hunan, places precise timing constraints on the Sb mineralization in this area. It is revealed that the Xikuangshan deposit formed during the late Jurassic-early Cretaceous Period, the early- and latestage mineralization took place at (155.5± 1.1) Ma and (124.1±3.7) Ma, respectively. The accurate age determination of mineralization is very crucial for revealing the super-enrichment mechanism of the element Sb at the Xikuangshan mine, and lays some foundations for the further understandings of its ore genesis and mineralization mechanism.     

Molybdenum isotopic composition as a tracer for low-medium temperature hydrothermal ore-forming systems: A case study on the Dajiangping pyrite deposit,western Guangdong Province,China

Little is known about the range or controls on the molybdenum isotopic composition of low-medium temperature hydrothermal ore-forming systems. We present molybdenum isotope data from 12 hydrothermal syndepositional silicalite and carbonaceous slate samples from the Dajiangping pyrite deposit in western Guangdong Province, South China. The δ ^97/95 Mo values from Orebody III range from −0.02‰ to 0.29‰, with an average of 0.18‰. In contrast, the composition values from Orebody IV display a larger variation from −0.70‰ to 0.62‰. However, the five samples from the main ore bed all show strong negative values. This indicates that the significant variation in molybdenum isotopic composition supports different hydrothermal ore-forming metallogenesis and a metallogenic environment between the two orebodies. Orebody III is likely to have been deposited from submarine exhalative hydrothermal fluids under a relatively strong reducing environment and Orebody IV may have also been influenced by hydrothermal superimposition in a more oxidized disequilibrium condition. In addition, the δ ^97/95 Mo values of Orebody IV are clearly negative, together with the values increasing stratigraphically upward in the ore beds, suggesting that the metallogenic environment of Orebody IV is different from the open oceanic systems. There might be dynamic fractionation in this restricted environment. Therefore, the molybdenum isotope can be used as an effective tracer for the ore-forming fluid and metallogenic environment.     

云南大红山铁铜矿床隐爆角砾岩的岩石学特征

在云南大红山铁铜矿床,利用隐爆角砾岩探讨隐伏矿床的找矿标志。在外围的东么矿区,通过野外观测隐爆角砾岩的产状,利用宏观和微观的方法研究隐爆角砾岩的岩石学特征及与矿石的关系,将东么矿区隐爆角砾岩分为3类:复成分隐爆角砾岩、英安质隐爆角砾岩和隐爆角砾状矿石;矿化岩石多出现于强钠长石化的隐爆角砾岩附近。在大红山矿区,强钠长石化的隐爆角砾岩是寻找隐伏矿床的一个重要标志。     

滇东北麻栗坪铅锌矿床石英原位微量元素特征及其地质意义

麻栗坪大型铅锌矿床(～6.0 Mt@13.4%Pb+Zn)赋存于下寒武统梅树村组硅质白云岩中,是滇东北铅锌成矿带的代表性矿床之一.石英是麻栗坪矿床主要的脉石矿物,其形成贯穿整个成矿期.详细的矿物学研究表明,麻栗坪矿床发育3期石英.Ⅰ期石英呈细粒半自形,与细粒黄铁矿、闪锌矿共生,Ⅱ期石英呈中-粗粒半自形,与粗粒闪锌矿、方铅矿共生,Ⅲ期石英较纯.总体上,Ⅰ期至Ⅲ期石英的阴极发光(Cathodoluminescene,CL)强度先增大后减小,与Al、Ge、Li、Na、K含量呈协同变化趋势,暗示微量元素对CL强度的控制作用.元素含量相关性研究显示,微量元素主要以单原子替代(Ge⁴⁺→Si⁴⁺)和补偿替代(Al³⁺+Li⁺/Na⁺/K⁺→Si⁴⁺)方式进入石英晶格.麻栗坪矿床石英中Ti含量极低,而Al含量变化范围较大,与岩浆热液矿床显著不同,显示其具有低温热液矿床的特点.Ⅰ期至Ⅲ期石英中Al含量呈先升高后降低的总体趋势,反映Al溶解度先增大后减...     

东昆仑尕林格铁矿床成因年代学及Hf同位素制约

尕林格矿床发育大量与铁多金属成矿关系密切的花岗闪长岩、石英二长岩、石英二长闪长岩和石英闪长岩体.LA-ICP-MS锆石U-Pb年代学表明石英二长闪长岩的年龄为228.3土0.5 Ma,石英二长岩的年龄为234.4±0.6 Ma.地球化学特征也较为相似,SiO2质量分数中等(58.4％～64.3％),w(FeOT)/w(MgO)偏低(0.62～1.38),A/CNK值(0.52～0.86)＜1,轻稀土富集,轻重稀土分馏明显,中等—强烈的负Eu异常(δEu为0.33～0.82),富集Rb,Th等大离子亲石元素,明显亏损高场强元素(Sr,P,Nb,Ta,Ti等),w(Rb)/w(Sr)为0.12～0.39,具有壳幔混合Ⅰ型花岗岩的特征.锆石Hf同位素组成表明,石英二长闪长岩的εHf(t)为-4.15～3.44,T2DM为1042～1523 Ma;石英二长岩εHf(t)为-5.06～1.7,T2DM为1157～1587 Ma,二者具有相同的岩浆来源,可能为壳幔混合岩浆作用的结果.综合研究认为尕林格铁矿床中三叠世岩体为东昆仑218～242 Ma俯冲—碰撞转换阶段,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的产物,中高温岩浆流体与围岩发生水—岩反应是矽卡岩型矿体形成的主要因素.     

广东长坑金银矿床矿石类型及矿物组合

长坑金银矿床中金和银分别构成独立的金矿体和银矿体.矿床的主要矿石类型包括原生矿石和次生氧化矿石.氧化矿石的矿物种类简单,主要是石英,其次是粘土矿物,少量的针铁矿、臭葱石,微量的磁铁矿、锆石、黄铁矿和其他硫化物,偶见自然金.原生金矿石包括硅质金矿石、钙硅质金矿石、铝硅质金矿石三种类型,原生银矿石主要是硅质银矿石.原生金矿矿石矿物包括黄铁矿、雄黄、雌黄、重晶石、辉锑矿,其次是白铁矿和极少量毒砂和自然金,为一套浅成低温矿物组合.原生银矿矿石矿物是方铅矿、闪锌矿、银黝铜矿、深红银矿、硫锑铜银矿、硫锑铅银矿、辉锑银矿、辉银矿,次要矿物有黄铁矿、黝铜矿、黄铜矿、脆硫锑银矿、淡红银矿,是一套中深成中温的含银单硫化物和含银硫盐矿物组合.反映金、银矿床分属浅成低温和中深成中温热液交代成因的两次不同成矿作用的产物,金矿成矿在先,银矿成矿在后并叠加改造了金矿.     

Sm-Nd isotopic geochronology of the Yinachang Fe-Cu-REE deposit at Wuding, Yunnan Province and its genetic significance

Sm-Nd isotope systematics of ores and fluorites places precise time constraints on REE mineralization of the Yinachang Fe-Cu-REE deposit in Yunnan Province which occur in the Proterozoic Kunyan group. The ore-related fluorites contain high abundant REE, and show a strong enrichment of LREE and a positive Eu anomaly, which is in marked contrast to post-ore fluorites that are HREE enriched. The Sm-Nd isochron ages of the ores and fluorites are 1539±40 Ma and 1617±100 Ma, respectively, and calculated εNd（t） are -4.6 and -3.2. Accurate age determinations of the mineralization demonstrate that the REE mineralization took place during early Mesoproterozoic. Together with other geological evidence from the ore deposit, the primary REE-bearing ore-forming fluids are suggested to have been derived from the Enriched Mantle, and the Yinachang Fe-Cu-REE ore deposit is of volcanic exhalation- hydrothermal sedimentary origin. This study also imply that the sudden large-scale REE mineralization in the Mesoproterozoic epoch may have been induced by alkaline-rich anorogenic magmatism which occurred at marginal rifts of the continent in the Mesoproterozoic.