A Preliminary Study on Fluid Inclusions and Mineralization of Xitieshan Sedimentary-Exhalative (SEDEX) Lead-Zinc Deposit

The Xitieshan lead-zinc deposit is located at the northern margin of the Qaidam Basin, Qinghai Province, China, and had developed a complete marine sedimentary-exhalative system. Our preliminary study of ore-forming fluids shows that fluid inclusions in quartz from altered stockwork rocks that represent the pipe facies have a wide range of temperature and salinity. The intense fluid activities are characteristics of the pipe facies of the exhalative system. Fluid inclusions in carbonates near the unstratified ore bodies hosted in the thick-bedded marble which represents vent-proximal facies are large in size and have moderate to high temperatures. They represent unerupted sub-seafloor fluid activity. Fluids in altered stockwork rocks and carbonates have similar H20-NaCI-CO2 system, both belonging to the sedimentary-exhalative system. The fluids migrate from the pipe facies to the unstratified ore bodies. Boiling of the fluids causes the separation of CO2 vapor and liquid H2O. When the fluids migrate into the unconsolidated thick-bedded marble, the escape of CO2, decreasing temperature and pressure as well as some involvement of seawater into the fluids result in the unmixing of fluids with high and low salinity and deposition of ore-forming materials. The two unmixed fluids were trapped in unconsolidated carbonates and the ore-forming materials were deposited in the unconsolidated carbonates to form the sedimentary-exhalative type unstratified ore bodies. The oreforming temperature of unstratified ore bodies is up to high temperature indicating that there is a huge ore-forming potential in its deep.

Early Silurian Wuchuan–Sihui–Shaoguan exhalative sedimentary pyrite belt, South China: constraints from zircon dating for K-bentonite of the giant Dajiangping deposit

The Wuchuan-Sihui-Shaoguan(WSS)exhalative sedimentary pyrite belt in the southwestern part of the Qinzhou-Hangzhou(Qin-Hang)belt is the most important sulfur industry base in China.However,a wide range of metallogenetic ages spanning from Ediacaran to Devonian has been reported in the literature.This age range does not support the idea that the typical character of"coeval mineralization"in an exhalative sedimentary mineralization belt in China and worldwide.Therefore,the precise determination of mineralization ages of representative deposits is necessary to provide guides for exploration and metallogenetic models.The Dajiangping pyrite deposit is a typical example of this kind of deposits and is also the largest deposit with a proven reserve of 210 Mt.This deposit was thought to have formed in Ediacaran or Devonian.In this study,2-3 layers of 10-25 cm thick 2M1-type microcrystalline muscovite slate abruptly embedded in the No.Ⅳmassive orebody of the deposit has been identified to be low-grade metamorphic K-bentonite.A Concordia zircon LA-ICP-MS U-Pb age of 432.5±1.3 Ma(mean standard weighted deviation of concordance and equivalence=1.2;N=11)has been yielded for the low-grade metamorphic K-bentonite.This age is distinctly different from the Rb-Sr isochron age of630.1±7.3 Ma for siliceous rock at the top of the No.Ⅲbanded orebody and the Re-Os isochron age of 389±62 Ma for pyrites from a laminated orebody.Instead,it is close to the intercept age(429 Ma)of the youngest detrital zircons from sandstone interlayers of the No.Ⅲbanded orebody.The Concordia age is also coincident with those of the Late Caledonian(400-460 Ma)magmatism-metamorphism events which are widely distributed in Cathaysia Block.Particularly,it agrees well with that of the Early Silurian extensional volcanism(434-444 Ma)which have been revealed in the Dabaoshan,Siqian-Hekou,and Nanjing volcanic basins in northern Guangdong Province and southern Jiangxi Province.Hence,the dating result in this study confirms that the sedimentary time of the ore-host Daganshan Formation is Early Silurian,and implies that the mineralization age of the Dajiangping pyrite deposit should also be Early Silurian.In combination with the Early Silurian age of Shezui pyrite deposit and the Dabaoshan volcanic basin along the WSS pyrite belt,it could be inferred that the WSS pyrite belt provides a record of the northern expanding of Qinzhou-Fangcheng trough in Early Silurian and that the exhalative pyrite mineralization was triggered by the postcollisional extension of the margin of Cathaysia Block after the intracontinental collision between Cathaysia Block and Yangtze Block during Late Caledonian stage.

Sea-floor exhalative sedimentary and magmatic hydrothermal superimposition on the Bainiuchang polymetallic deposit in Yunnan Province: REE geochemical evidence

In order to study the characteristics of sea-floor exhalative sedimentary and magmatic hydrothermal superimposition on the Bainiuchang polymetallic deposit, the REE compositions of the granites, host-rocks and ores have been systematically analyzed by ICP-MS. As viewed from their REE compositions, the granites show obvious negative Eu anomalies and weak negative Ce anomalies. According to their REE characteristics, the host-rocks were derived partly from sea-floor exhalative sediments. In terms of their REE compositions, the ores can be divided into two groups: one group, of which the samples were collected from the Baiyang segment relatively far away from the Bozhushan granite batholith, possesses positive Eu anomalies or no Eu anomaly and negative Ce anomalies, indicating that ore-forming hydrothermal fluid was relatively reductive and its temperature was higher than 250 ℃. Furthermore, the coinstantaneous presence of positive Eu anomalies and negative Ce anomalies indicate that the convective mixing of a little amount of seawater with hydrothermal fluid had happened while ores were precipitated on ancient sea floor. The other group, of which the samples were mainly collected from the Chuanxindong and Duimenshan segments near the Bozhushan granite batholith, has similar chondrite-monalized REE distribution patterns to those of the magmatic rocks. But as a whole, the REE characteristics of both groups change gradually starting from the Bozhushan granite batholith. Based on the REE characteristics of the granites, host-rocks and ores, it is suggested that the ore-forming metals seem to have come from several different sources.

Genesis of the Zhaokalong Fe-Cu Polymetallic Deposit at Yushu, China: Evidence from Ore Geochemistry and Fluid Inclusions

The ore types of the Zhaokalong Fe-Cu deposit are divided into two categories： sulfide-type and oxide-type. The sulfide-type ore include siderite ore, galena-sphalerite ore and chalcopyrite ore, whereas the oxide-type ore include magnetite ore and hematite ore. The ore textures and structures indicate that the Zhaokalong deposit is of the sedimentary-exhalative mineralization type. Geochemical analyses show that the two ore types have a high As, Sb, Mn, Co and Ni content. The REE patterns reveal an enrichment of the LREE compared to the HREE. Isotopic analysis of siderite ore reveal that the j13CpDB ranges from -2.01 to 3.34 （%0） whereas the JISOsMow ranges from 6.96 to 18.95 （%0）. The fluid inclusion microthermometry results indicate that homogenization temperatures of fluid inclusions in quartz range from 131 to 181~C, with salinity values of 1.06 to 8.04 wt% NaCI eq. The mineralizing fluid therefore belongs to the low temperature - low salinity system, with a mineralizing solution of a CO2-Ca2＋（Na＋, K＋）-SO42- （F-, CI--H20 system. The geochemical results and fluid inclusion data provide additional evidence that the Zhaokalong deposit is a sedex-type deposit that experienced two stages of mineralization. The sulfide mineralization probably occurred first, during the sedimentary exhalative process, as exhibited by the abundance of marine materials associated with the sulfide ores, indicating a higher temperature and relatively deoxidized oceanic depositional environment. After the main exhalative stage, hydrothermal activity was superimposed to the sulfide mineralization. The later stage oxide mineralization occurred in a low temperature and relatively oxidized environment, in which magmatic fluid circulation was dominant.

U-Pb Geochronology and Geochemistry of Stratiform Garnet from the Aqishan Pb-Zn Deposit,Eastern Tianshan,Xinjiang,NW China:Constraints on Genesis of the Deposit

The Aqishan lead-zinc deposit,located in the Jueluotag metallogenic belt of eastern Tianshan,Xinjiang,Northwest China,has a stratiform occurrence in the marine volcanic tuff of the Yamansu Formation.The ore body has a typical double-layer structure,having a stratified,stratoid,lenticular upper part and a veined,stockwork-like lower part.The occurrence of the upper orebody is consistent with that of the volcanic tuff wall rock.The ore minerals are mainly chalcopyrite,pyrite,sphalerite,galena and magnetite,the altered minerals mainly being silicified,such as sericite,chlorite,epidote,garnet.The garnetized skarn,being stratiform and stratoid,is closely related to the upper part of the orebody.Geological observations show that the limestone in the ore-bearing Yamansu Formation is not marbleized and skarnized.Spatially,it is associated with the ferromanganese deposits in the marine volcanic rocks of the Yamansu Formation.These geological features reflect the likelihood that the Aqishan lead-zinc deposit is a hydrothermal exhalation sedimentary deposit.The results from the EPMA show that the garnet is mainly composed of grossular-andradite series,contents being in a range of 34.791-37.8%SiO_(2),32.493-34.274%CaO,8.454-27.275%FeO,0.012-15.293%Al_(2)O_(3),0.351-1.413%MnO,and lower values of 0.013-1.057%TiO_(2).The content of SiO_(2) vs.CaO and FeO vs.Al_(2)O_(3) has a significant positive correlation.The results of ICP-MS analysis for the garnet show that the REE pattern is oblique to right in general.The total amount of rare earth elements is relatively low,ΣREE=71.045-826.52 ppm,which is relatively enriched for LREE and depleted for HREE.LREE/HREE=8.66-4157.75,La_(N)/Yb_(N)=23.51-984.34,with obvious positive Eu and Ce anomalies(δEu=2.27-76.15,δCe=0.94-1.85).This result is similar to the REE characteristics of ore-bearing rhyolite volcanic rocks,showing that the garnet was formed in an oxidizing environment and affected by clear hydrothermal activity.The U-Pb isotopic dating of garnet by fs-LA-HR-ICP-MS gives an age of 316.3±4.4 Ma(MSWD=1.4),which is consistent with the formation time of the Yamansu Formation.According to the study of deposit characteristics and geochemical characteristics,this study concludes that the Aqishan lead-zinc deposit is a hydrothermal exhalation sedimentary deposit,the garnet being caused by hydrothermal exhalative sedimentation.

驼路沟喷气沉积型钴(金)矿床成矿地质背景及矿床成因的地球化学限制

驼路沟矿床是东昆仑南部造山带中新发现的钴（金）矿床,它的含矿岩系是一套浅变质的（绿片岩相）震旦-寒武纪火山-沉积岩系。火山岩是一套中-酸性凝灰岩及熔岩,其元素地球化学特征类似于活动大陆边缘或弧火山岩;沉积岩包括碎屑岩和黑色页岩,它们具有活动大陆边缘沉积岩的元素地球化学极性,部分沉积岩具有现代大陆弧地区沉积岩的元素地球化学特征。岩相学、矿物学及元素地球化学研究证明,作为主岩之一的石英钠长岩是典型的喷气沉积岩,而并非“脉岩”,它不但是钴（金）矿体的重要找矿标志,而且也是喷气沉积矿床的重要鉴别标志。钴（金）矿石组构及矿石矿物的世代显示其主要与海底喷气沉积成矿作用有关,在后期的碰撞造山过程中,受到了改造和活化。矿石和喷气沉积岩的痕量元素地球化学特征表明,它们同属喷气-成矿流体较远离喷气中心的海底沉积物。总之,岩（矿）相学及元素地球化学资料证明,驼路沟钴（金）矿床主要属喷气沉积矿床,形成于震旦-寒武纪东昆仑南缘的活动大陆边缘环境。

东昆仑祁漫塔格地区野马泉铁铜矿床地质特征及成因探讨

前人认为野马泉铁多金属矿属矽卡岩型,笔者首次在野马泉矿区发现在矿体的顶部有喷流岩——紫红色碧玉岩出现,证明在野马泉矿区曾发生过海底喷流成矿作用。通过分析对比,认为该区早期为喷流沉积成矿作用,晚期为矽卡岩成矿作用,也就是说野马泉铁铜矿床的成因应为喷流沉积+矽卡岩型。对于在该区找矿有重要的理论意义。

安徽铜陵冬瓜山铜(金)矿床成矿模式

长江中、下游断裂坳陷带是我国重要的铜、金、铁、硫成矿带,存在一系列块状硫化物矿床及与其伴生的矽卡岩型和斑岩型矿床。本文以铜陵矿集区冬瓜山铜、金矿床为例,探讨了这类矿床的成矿模式。冬瓜山矿床主要由层状硫化物矿体组成,伴有矽卡岩型和斑岩型矿体。层状硫化物矿体产于晚泥盆世砂岩和晚石炭世碳酸盐岩之间,具明显的层控特征,矿体下盘发育细脉—网脉状硫化物矿化以及硅化和绢云母化,矿体中伴有热水沉积岩,矿石具典型的沉积构造。燕山期岩浆热液对层状矿体进行了叠加和改造,改变了矿石的结构构造和矿石成分。黄铜矿交代黄铁矿变斑晶呈环斑结构或脉状交代结构,交代磁黄铁矿呈交代假象结构或交代残留结构。矽卡岩型矿体中黄铜矿的δ^(65)Cu 值为0.09‰～0.83‰,集中在0.23‰～0.83‰。层状矿体中黄铜矿的δ^(65)Cu 值为0.45‰～0.78‰,与矽卡岩矿体中黄铜矿的^(65)Cu 值大致相当,这说明两类矿体中的铜具有相同的来源。铜、氢和氧同位素研究表明,冬瓜山矿床铜来自岩浆岩,叠加的成矿流体主要为岩浆流体。提出了冬瓜山矿床属喷流沉积—岩浆热液叠生成因的成矿模式:在晚石炭世,海底喷流成矿作用形成了块状硫化物矿床,矿石成分以硫、铁为主;燕山期岩浆热液一方面对块状硫化物矿床进行改造,致使其富集铜等成矿物质,另一方面与围岩相互作用形成矽卡岩型和斑岩型矿体。

青海锡铁山铅锌矿的成因讨论

锡铁山铅锌矿是目前青海省最大的有色金属矿山,其属于以沉积岩为主要围岩的海底热水喷流沉积型矿床,大理岩和(碳质)片岩可作为一种找矿标志,但不能作为矿床类型划分依据。该区经历了多次喷发旋回,因此形成的铅锌矿也具有旋回层,应在今后的地质勘查找矿中特别注意,一个旋回层的结束就代表成矿作用的结束。从钻孔的资料和岩心看,该区至少有7次喷发旋回,也许更多,也就是说有多次成矿作用。找矿的类型为喷流沉积型铅锌矿床。

云南易门狮子山铜矿的地球化学

笔者近年承担了“罗次一元江元古宙海底喷流成矿”项目研究,应用了喷流成矿理论,将宏观矿床地质与微观地球化学相结合,对易门狮子山矿床进行了重点解剖。按矿床特征、成矿作用和地球化学,将矿床划分为三个成因类型,即喷流热水沉积-改造型铜矿、沉积-改造型砂岩铜矿和与细碧岩有关的含铜磁铁矿。第一类为矿区最主要铜矿类型,铜储量占矿区已探明储量的90％,是主要的找矿对象。该类型的主矿体深部和NW侧喷流岩发育,是最有利的找矿靶区。

西昆仑塔什库尔干铁矿带矿床类型、成因及成矿规律

在对西昆仑塔什库尔干地块地质演化、含矿岩系、锆石U-Pb同位素年代学和典型铁矿床进行研究的基础上,总结了区域含矿建造的特征、时代、矿床类型及成矿规律。结果表明：西昆仑塔什库尔干地块原＂布伦阔勒群＂实际上发育古元古代（2 100~2 500 Ma）、寒武纪早期（510~540 Ma）等两期沉积成矿事件,同时在中晚元古代（800~1 800 Ma）和海西期—印支期（200~410Ma）分别发生过强烈的变质和变形作用,局部富矿的形成可能与后期热液的叠加改造作用有关。区域铁矿可划分为两类：一为条带状铁建造遭受后期热液叠加改造的沉积变质型铁矿床,如赞坎、莫喀尔和吉尔铁克沟铁矿床,其形成环境为早元古代活动陆缘的弱氧化—还原的浅海相沉积环境,成矿物质来源于海底热液对基性火山岩的淋滤及少量陆源物质的风化;二为早寒武世海相火山-喷流沉积型铁矿床,如喀来子、老并和叶里克铁矿床,其形成条件为半深海—浅海相、弱氧化—半氧化的断陷盆地环境,成矿成岩物质主要来源于海底热水沉积及陆源物质。根据区域成矿规律,推测卡拉本—喀来子—莫拉赫一带是寻找早寒武世与海底喷流成矿系统有关的铁-多金属矿的有利地区,吉尔铁克沟—赞坎北地区、莫喀尔及其以南地区是赞坎铁矿带的北延和南延,是寻找古元古代沉积变质型铁矿的有利地区。

长江中下游成矿带铜多金属矿床中灰泥丘的发现及其意义——以武山和冬瓜山铜矿为例

通过对长江中下游成矿带中武山铜矿和冬瓜山铜矿层状硫化物矿体的详细研究,发现了大量具有层圈状构造、层纹状构造或不规则同心环状构造的矿石。在前人研究基础上,经光薄片鉴定、扫描电镜观察和碳氧同位素分析等,认为这类矿石在宏观构造上显示出类似于灰泥丘的孔洞系统,微观上又发现了细菌等微生物结构,判断其属于一种矿化的灰泥丘。资料显示,灰泥丘产出的环境为陆坡相,水深明显大于台地相,并且灰泥丘与热水喷流沉积成矿作用关系密切,在国内外许多热水喷流沉积成因矿床中均发现有灰泥丘。本文所研究的两个矿床中灰泥丘构造矿石保存状况略有不同,冬瓜山铜矿灰泥丘构造矿石保留了大量显示原生热水喷流沉积成因的组构、并发现细菌等微生物结构,碳-氧同位素组成也显示原始沉积特征;而武山铜矿灰泥丘构造矿石则显示出受热液改造的矿石组构和碳-氧同位素组成特征,暂未发现细菌等微生物结构。冬瓜山和武山铜矿灰泥丘构造矿石的发现,有力地佐证了长江中下游成矿带在海西期曾发生过热水喷流沉积成矿作用。

安徽铜陵冬瓜山矿床中磁黄铁矿矿石结构特征及其成因意义

安徽铜陵冬瓜山矿床是长江中下游地区具有代表性的大型层状硫化物矿床,磁黄铁矿为矿床中的主要硫化物矿物。该矿床主要由层状硫化物矿体组成,伴有矽卡岩型和斑岩型矿体。在层状矿体上部,磁黄铁矿主要为块状构造,而层状矿体下部,磁黄铁矿多为层纹状、条带状构造,具有显著的沉积结构构造特征。野外地质观察及室内矿相学研究表明,层状矿体中磁黄铁矿矿石遭受了强烈的变质作用及热液交代作用。进变质过程中形成的结构主要为胶黄铁矿转变为黄铁矿以及进一步变质转变为磁黄铁矿、磁铁矿时形成的交代残留结构。退变质过程则以磁黄铁矿的退火、黄铁矿变斑晶的生长和单纯六方磁黄铁矿的形成为特征。岩浆热液对单纯六方磁黄铁矿的交代作用形成了单斜和六方磁黄铁矿的交生结构。这些结构特征表明层状矿体中的磁黄铁矿并不是岩浆热液成因,而主要为石炭纪同生沉积胶黄铁矿、黄铁矿在燕山期岩浆侵入所引起的热变质作用下脱硫所形成,并在热变质作用之后又受到岩浆热液的叠加交代。磁黄铁矿的结构特征显示冬瓜山矿床的形成经历了同生沉积、热变质、热液交代等多个阶段,支持其为同生沉积-叠加改造型矿床。

喀喇昆仑火烧云超大型喷流-沉积成因碳酸盐型Pb-Zn矿的发现及区域成矿学意义

新疆和田火烧云Pb-Zn矿床是喀喇昆仑地区新发现的一个超大型碳酸盐型Pb-Zn矿床,产于中侏罗统龙山组灰岩中。矿体呈层状产出,与地层产状一致,主要由菱锌矿与白铅矿组成,矿石类型以纹层状、块状、角砾状及交代蚀变成因为主。矿体发育沉积超覆构造、韵律层理、粒序层理、鲕粒结构等典型的沉积结构与构造。矿石与围岩方解石的C,O同位素分析结果显示：菱锌矿与围岩方解石的C,O同位素组成相近（其δ13CPDB主要分布在0.78%~3.72‰,δ18OSMOW主要分布在21.71‰~24.87‰）,C,O来源主要为海水;白铅矿δ13CPDB=-7.28~1.19‰,δ18OSMOW=10.78‰~16.81‰,C,O来源为岩浆热液与海水混合流体。矿区菱锌矿与白铅矿的C,O同位素组成与表生氧化带中的碳酸盐型Pb-Zn矿不同。火烧云铅锌矿床闪锌矿Rb-Sr等时线年龄为（186±6）Ma,多宝山铅锌矿床的成矿年龄与火烧云一致。火烧云Pb-Zn矿床具原生层控特征,为喷流-沉积成因,是SEDEX型Pb-Zn矿床的新类型。火烧云碳酸岩型Pb-Zn矿的发现是Pb-Zn矿床成因研究的重要进展,表明喀喇昆仑乃至藏北地区相应构造层位具寻找同类型铅锌矿床潜力。

“镜铁山式”铁铜矿床地质特征及其成因探讨

探讨了镜铁山桦树沟矿区铁铜矿床成矿地质背景和成岩成矿的演化过程，阐述控制铁铜矿带在水平和垂向分带变化的地质特征。根据线性构造与火山喷发沉积关系，着重探讨“镜铁山式”铁铜矿床的成因机制，并运用δ３４Ｓ、δ１８Ｏ、δ１３Ｃ测试成果，确立含铁铜硅质岩建造，建立上铁下铜结构分带。认为该类型矿床是与海相火山作用有关的喷气沉积成因矿床，具有与块状硫化物矿床共生。

西藏当雄县拉屋铜铅锌多金属矿床喷流沉积成因

拉屋铜铅锌多金属矿床位于纳木错—嘉黎断裂带南侧的上石炭统—下二叠统来姑组中,矿体分布受日音拿背斜控制。矿区内矿化类型以层纹状、层状矿化为主,晚期有脉状矿化叠加。在矿床地质特征研究基础上,通过矿石和容矿围岩的稀土元素、稳定同位素地球化学特征分析,探讨了成矿物质来源及矿床成因。研究显示,矿床容矿围岩稀土元素具有弱Ce负异常(0.89～0.95)和Eu中等亏损(0.56～0.64)的特点。硫化物硫同位素δ34S值变化范围为-2.92‰～-0.42‰,平均值为-1.68‰,为深源硫来源。矿石中石英包裹体氢氧同位素组成显示,矿床成矿热液流体早期以深循环的海水与岩浆水的混合流体为主,中、晚期则有为长时间大气降水的参与,成矿流体来源以大气降水为主。综合研究表明:拉屋铜铅锌多金属矿床属于喷流沉积-叠加改造型矿床,具有喷流沉积型矿床的特征,燕山期则表现为岩浆热液活动叠加改造。

青海省锡铁山Sedex型铅锌矿床成矿流体来源及演化:流体包裹体及同位素地球化学证据

锡铁山铅锌矿床产于青海省柴达木盆地北缘早古生代裂陷的中基性火山-沉积岩系中,是我国规模最大的铅锌矿床之一。流体包裹体的温度、盐度、气液相成分测试以及同位素组地球化学研究证明锡铁山矿床形成于喷流沉积系统。管道相成矿流体以深源为主,深源流体的CO_2等气相组分溢出及深源流体与海水的混合作用导致了成矿物质沉淀,层状矿体中石英岩是管道相向SE方向位移、喷流的结果,锡铁山铅锌矿床是VMS型与Sedex型系统的复合或过度。

西秦岭造山带东段喷流沉积型铅锌矿床特征及其成矿模式——以徽县洛坝矿床为例

西秦岭造山带东段西成矿田内发育一系列泥盆纪的喷流沉积型（sEDEx）铅锌矿床，甘肃徽县洛坝铅锌矿床就是其中的代表型矿床之一。它产于中泥盆统安家岔组焦沟层上部，矿体分布受洛坝背斜和南、北两翼断裂控制，与地层产状基本一致，矿石主要为纹层状、层状、浸染状、块状构造。经过详细的显微构造和SEM扫描电镜分析，鉴定出与喷流沉积有关的通道构造、淬火构造等。矿床地球化学分析显示，该矿床赋矿围岩的Ba、As、Sb、B、Ag、Hg等喷流沉积指示元素值均较高，且两者均具有LREE相对富集、明显的Eu正异常和中等Ce正异常特征，对比表明，成矿流体中的REE主要继承赋矿围岩（硅质岩）。矿床包裹体及硫同位素分析表明：成矿温度为168～350℃，以中、高温为主；早期矿化硫化物的δ^34S值（平均9．8‰）明显大于晚期矿化硫化物的δ34S值（平均5．6‰），说明后期改造作用中有地层硫的参与。综合研究表明，该矿床为热水喷流沉积型铅锌矿床，后期又受到海西期一印支期的叠加改造，并确定该矿床为秦岭后造山期板内伸展热水喷流的产物，最后建立了洛坝铅锌矿床热水喷流沉积成矿模式。

云南澜沧老厂大型银多金属矿床黄铁矿稀土和微量元素地球化学

云南澜沧老厂银多金属矿床是"三江"成矿带南段著名的代表性矿床之一。本文系统研究了矿床中黄铁矿(石)的稀土和微量元素地球化学特征。结果表明:老厂矿床黄铁矿(石)稀土元素总量较低,黄铁矿石ΣREE平均为5.54×10-6,其单矿物ΣREE平均仅为0.25×10-6;各类样品稀土配分模式均为明显右倾的轻稀土富集模式,轻稀土分异较强、而重稀土元素分异较弱;黄铁矿石、矿物δEu正异常、δCe负异常和轻稀土富集的配分模式与现代海底热液稀土的十分相似,是成矿流体海底喷流沉积的体现,此外黄铁矿石、矿物还发育弱的δEu负异常,可能是后期岩浆成矿热液叠加改造的结果。矿床黄铁矿单矿物除相对富集少量高场强元素外,其它元素均有不同程度的亏损,其Hf/Sm、Th/La、Nb/La值普遍<1,表明矿床成矿流体可能是以富Cl的成矿热液为主;黄铁矿Co、Ni含量较低且变化较大,Co/Ni比值显示矿床经历了不同的成矿阶段,利用Y/Ho比值示踪成矿流体表明,黄铁矿Y/Ho比值与海水及海底热液基本一致,为矿床经历海底火山喷流沉积成矿作用提供了新的佐证。

云南白牛厂银多金属矿床成矿作用特征的稀土元素地球化学约束

为了研究白牛厂银多金属矿床成矿作用特征,对矿区岩浆岩、围岩和矿石的稀土元素进行了ICP-MS分析测试。花岗岩稀土元素组成表现了较强的Eu负异常和弱的Ce负异常。围岩稀土元素特征表现出一定程度的热水沉积成因。矿石的稀土元素组成大致可分为两组:一组矿石表现为Eu正异常或无异常和Ce负异常,反映喷流沉积稀土元素组成特征,主要是距离花岗岩体较远的白羊矿段,指示成矿热液为温度较高(>250℃)、相对还原的流体,另外,Eu正异常和Ce负异常同时出现,说明矿石沉淀时较高温度的流体与少量的海水发生了对流混合;另一组矿石表现出与岩浆岩一致的球粒陨石标准化稀土配分模式,显示岩浆热液叠加改造成因,主要是距离花岗岩体较近的穿心洞矿段和对门山矿段。两组矿石稀土元素组成特征总体来说随着花岗岩体距离的变化而变化。根据岩浆岩、围岩和矿石的稀土元素组成特征,白牛厂银多金属矿床由喷流沉积形成主矿体,燕山期花岗质岩浆活动对矿体部分叠加改造。