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1.
The Dahutang tungsten polymetallic ore field is located north of the Nanling W-Sn polymetallic metallogenic belt and south of the Middle—Lower Yangtze River Valley Cu-Mo-Au-Fe porphyry-skarn belt.It is a newly discovered ore field,and probably represents the largest tungsten mineralization district in the world.The Shimensi deposit is one of the mineral deposits in the Dahutang ore field,and is associated with Yanshanian granites intruding into a Neoproterozoic granodiorite batholith.On the basis of geologic studies,this paper presents new petrographic,microthermometric,laser Raman spectroscopic and hydrogen and oxygen isotopic studies of fluid inclusions from the Shimensi deposit.The results show that there are three types of fluid inclusions in quartz from various mineralization stages:liquid-rich two-phase fluid inclusions,vapor-rich two-phase fluid inclusions,and three-phase fluid inclusions containing a solid crystal,with the vast majority being liquid-rich two-phase fluid inclusions.In addition,melt and melt-fluid inclusions were also found in quartz from pegmatoid bodies in the margin of the Yanshanian intrusion.The homogenization temperatures of liquid-rich two-phase fluid inclusions in quartz range from 162 to 363℃ and salinities are 0.5wt%-9.5wt%NaCI equivalent.From the early to late mineralization stages,with the decreasing of the homogenization temperature,the salinity also shows a decreasing trend.The ore-forming fluids can be approximated by a NaCl-H_2O fluid system,with small amounts of volatile components including CO_2,CH_4 and N_2,as suggested by Laser Raman spectroscopic analyses.The hydrogen and oxygen isotope data show that δ5D_(V-smow) values of bulk fluid inclusions in quartz from various mineralization stages vary from-63.8‰ to-108.4‰,and the δ~(18)O_(H2O) values calculated from the δ~(18)O_(V-)smow values of quartz vary from-2.28‰ to 7.21‰.These H-O isotopic data are interpreted to indicate that the ore-forming fluids are mainly composed of magmatic water in the early stage,and meteoric water was added and participated in mineralization in the late stage.Integrating the geological characteristics and analytical data,we propose that the ore-forming fluids of the Shimensi deposit were mainly derived from Yanshanian granitic magma,the evolution of which resulted in highly differentiated melt,as recorded by melt and melt-fluid inclusions in pegmatoid quartz,and high concentrations of metals in the fluids.Cooling of the ore-forming fluids and mixing with meteoric water may be the key factors that led to mineralization in the Dahutang tungsten polymetallic ore field.  相似文献   

2.
The Chehugou Mo–Cu deposit, located 56 km west of Chifeng, NE China, is hosted by Triassic granite porphyry. Molybdenite–chalcopyrite mineralization of the deposit mainly occurs as veinlets in stockwork ore and dissemination in breccia ore, and two ore‐bearing quartz veins crop out to the south of the granite porphyry stock. Based on crosscutting relationships and mineral paragenesis, three hydrothermal stages are identified: (i) quartz–pyrite–molybdenite ± chalcopyrite stage; (ii) pyrite–quartz ± sphalerite stage; and (iii) quartz–calcite ± pyrite ± fluorite stage. Three types of fluid inclusions in the stockwork and breccia ore are recognized: LV, two‐phase aqueous inclusions (liquid‐rich); LVS, three‐phase liquid, vapor, and salt daughter crystal inclusions; and VL, two‐phase aqueous inclusions (gas‐rich). LV and LVS fluid inclusions are recognized in vein ore. Microthermometric investigation of the three types of fluid inclusions in hydrothermal quartz from the stockwork, breccia, and vein ores shows salinities from 1.57 to 66.75 wt% NaCl equivalents, with homogenization temperatures varying from 114°C to 550°C. The temperature changed from 282–550°C, 220–318°C to 114–243°C from the first stage to the third stage. The homogenization temperatures and salinity of the LV, LVS and VL inclusions are 114–442°C and 1.57–14.25 wt% NaCl equivalent, 301–550°C and 31.01–66.75 wt% NaCl equivalent, 286–420°C and 4.65–11.1 wt% NaCl equivalent, respectively. The VL inclusions coexist with the LV and LVS, which homogenize at the similar temperature. The above evidence shows that fluid‐boiling occurred in the ore‐forming stage. δ34S values of sulfide from three type ores change from ?0.61‰ to 0.86‰. These δ34S values of sulfide are similar to δ34S values of typical magmatic sulfide sulfur (c. 0‰), suggesting that ore‐forming materials are magmatic in origin.  相似文献   

3.
Native bismuth in the form of metallic melt has been considered instrumental to the formation of some metallic ore deposits via a mechanism dubbed the “Liquid Bismuth Collector Model.” Here, we provide petrographical documentation of trail‐forming, μm‐sized blebs of native bismuth in cassiterite–quartz veins from the Santa Bárbara greisen Sn deposit in the Rondônia tin province of northern Brazil. These inclusions suggest the trapping of a Bi melt that took place during vein formation, in a mechanism similar to the entrapment of fluid inclusions.  相似文献   

4.
The recently discovered Xiaobeigou fluorite deposit is situated in the southern part of the Southern Great Xing'an Range metallogenic belt. Fluorite‐bearing veins are rather common over the whole area. So far, 11 mineralized veins have been delineated at the Xiaobeigou deposit. Orebodies of the deposit are mainly hosted in Permian and Jurassic volcano‐sedimentary rocks. The orebodies in this mining district exhibit a well‐developed vertical zonation: from top to bottom, the orebodies can be divided into upper, central, and lower zones. The central zone is the most important part for mining operations, and it shows lateral zonation of fluorite mineralization. Rare earth element (REE) contents of the investigated samples are relatively low (less than 30.2 ppm). Furthermore, the REE contents of the fluorite grains from early to late ore stages exhibit a decreasing trend. All the fluorite samples show no or slightly positive Eu anomalies. Three types of fluid inclusions (FIs) are distinguished in the quartz and fluorite samples, including pure‐liquid single‐phase (PL‐type), liquid‐rich two‐phase (L‐Type), and vapor‐rich two‐phase (V‐type) FIs. The FIs hosted in early‐stage quartz were homogenized at 159.5–260.7°C (mainly 160–240°C); their salinities range from 0.18 to 1.22 wt.% NaCl eqv. The FIs hosted in early‐stage fluorite yield slightly lower homogenization temperatures of 144.4–266.8°C (peaking at 140–220°C), which correspond to salinities of 0.18–0.88 wt.% NaCl eqv. Homogenization temperatures and salinities for the late stage are 132.5–245.8°C (mainly 160–180°C) and 0.18–1.40 wt.% NaCl eqv., respectively. Laser Raman spectroscopy of FIs shows that both the vapor and liquid compositions of the inclusions are dominated by H2O. The H–O isotopic compositions at Xiaobeigou suggest that the ore‐forming fluids are predominantly of meteoric water origin. The Xiaobeigou deposit can be classified as a typical low‐temperature hydrothermal vein‐type fluorite deposit. Combined with regional data, we infer that the fluorite mineralization occurred during the Late Mesozoic in an extensional setting.  相似文献   

5.
大兴安岭锡矿带是中国北方唯一成型的锡多金属成矿带。新近发现的内蒙古维拉斯托锡多金属矿床位于大兴安岭南段,隶属中亚造山带东段的兴蒙造山带。该矿床为一典型的大型斑岩型热液脉型锡多金属矿床,矿区内锡矿化主要赋存于石英斑岩体顶部及其上部的石英脉中。矿床成矿阶段包括石英斑岩体内的滴状锡锌矿化阶段、石英斑岩体上部石英脉中的辉钼矿矿化阶段、石英锡石黑钨矿阶段和石英多金属硫化物阶段。流体包裹体研究结果显示：流体包裹体类型主要为气液两相包裹体,尤其是富液相包裹体,其次为含子矿物的三相包裹体。斑岩体内矿化阶段流体包裹体均一温度为324~333 ℃,盐度为6.5%~7.5% NaCleqv,密度为0.73~0.74 g/cm3;石英脉型矿化阶段包裹体均一温度为201~324 ℃,盐度为3.4%~9.9% NaCleqv,密度为0.73~0.92 g/cm3。包裹体显微测温分析结果显示该矿区成矿流体具有中高温、低盐度、中密度的特征。激光拉曼光谱分析表明,气液两相包裹体液相成分主要为H2O,气相成分主要有H2O、CO2和CH4。氢氧同位素研究结果表明该矿床石英斑岩体上部石英脉矿化阶段的成矿流体为岩浆水和大气降水混合来源,以岩浆水为主。岩浆流体与大气降水的混合以及流体演化中的降温过程是该矿床矿石沉淀的主要机制。  相似文献   

6.
《Resource Geology》2018,68(1):83-92
Cu–Mo mineralization occurs in southern part of the Chatree Au–Ag deposit, central Thailand. Quartz veins of Cu–Mo mineralization are divided into five types: Types A, B, C, D and E. Quartz veins of Types A, B and C are hosted in altered granodiorite porphyry, and quartz veins of Types D and E occur in altered andesite lava. Mineral assemblages of Types A, B and C quartz veins are composed of qz–chl–ilt–mol–py–ccp, qz–chl–ilt–ccp–py and qz–chl–ilt–ccp–py–sp–po, respectively. Types D and E quartz veins consist of qz–chl–py–ccp–sp–po and qz–ep, respectively. Fluid inclusions of quartz veins are divided into liquid‐rich two‐phases fluid inclusion, vapor‐rich two‐phases fluid inclusion and multiphase solid‐bearing fluid inclusion. Coexistence of a halite‐bearing fluid inclusion having salinity of 37 equiv. wt.% NaCl and a vapor‐rich two‐phases fluid inclusion having salinity of 1 equiv. wt.% NaCl suggests that the Cu–Mo‐bearing quartz veins were formed at temperature of 450°C and pressure of 250 bars (depth of approximately 1.5 km from the paleosurface). Based on the formation temperature of 450°C of quartz veins and the δ18O values of quartz of the quartz veins, the δ18O value of fluid responsible for the Cu–Mo‐bearing quartz vein is estimated to be +9.9‰. The origin of fluid forming the Cu–Mo‐bearing quartz veins in the N prospect of the Chatree mining area would be magmatic water. Based on the characteristics of geology, age, mineral assemblage and the formation environment, Cu–Mo mineralization would be different from the epithermal Au–Ag mineralization of the Chatree mining area.  相似文献   

7.
The late Triassic Baolun gold deposit hosted by Silurian phyllites is a large‐scale high‐grade gold deposit in Hainan Island, South China. The ores can be classified into quartz‐vein dominated type and less altered rock type. Three mineralization stages were recognized by mineral assemblages. The early stage, as the most important mineralization stage, is characterized by a quartz–native gold assemblage. The muscovite?quartz?pyrite?native gold assemblage is related to the intermedium mineralization stage. In late mineralization stage, native gold and Bi‐bearing minerals are paragenetic minerals. Microthermometry analyses show that the early mineralization stage is characterized by two types of fluid inclusions, including CO2‐rich inclusions (C‐type) and aqueous inclusions (W‐type). C‐type inclusions homogenize at 276–335°C with an averaged value of 306°C and have salinities of 1.0–10.0 wt% NaCl equivalent (mean value of 4.9 wt% NaCl equivalent). W‐type inclusions homogenize at 252–301°C (mean value of 278°C) with salinity of 4.0–9.7 wt% NaCl equivalent (mean value of 7.4 wt% NaCl equivalent). In intermedium mineralization stage, C‐type and W‐type inclusions homogenize at 228–320°C (mean value of 283°C) and 178–296°C (mean value of 241°C), with salinities of 2.4–9.9 wt% NaCl equivalent (mean value of 6.5 wt% NaCl equivalent) and 3.7–11.7 wt% NaCl equivalent (mean value of 7.7 wt% NaCl equivalent), respectively. No suitable mineral, such as quartz or calcite, was found for fluid inclusion study from late mineralization stage. In contrast, only aqueous inclusions were found from post‐ore barren veins, which yielded lower homogenization temperatures ranging from 168–241°C (mean value of 195°C) and similar salinities (2.6–12.6 wt% NaCl equivalent with averaged value of 7.2 wt% NaCl equivalent). The different homogenization temperatures and similar salinities of C‐type and W‐type from each mineralization stage indicate that fluid immiscibility and boiling occurred. The Baolun gold deposit was precipitated from a CO2‐bearing mesothermal fluid, and formed at a syn‐collision environment following the closure of the Paleo‐Tethys.  相似文献   

8.
Abstract: The North granitic body of the Miyako pluton is located in the Northern Kitakami belt, Northeast Japan. The formation of the scheelite–chalcopyrite–magnetite–bearing aplitic veins and scheelite–chalcopyrite–magnetite–bearing Yamaguchi skarn deposit was closely associated with the formation of the Miyako plutons. Petrographic facies of the North granitic body vary from quartz diorite in marginal zone (zone A), to tonalite and granodiorite (zone B), and to granite (zone C) in the central. The large numbers of aplitic veins distributed around the Yamaguchi mining area are divided into two groups: barren and scheelite–mag–netite–chalcopyrite–bearing aplitic veins. The latter cut massive clinopyroxene skarns of the Yamaguchi deposit, and are composed of plagioclase, K‐feldspar and titanite. Some plagioclase crystals have dusty cores with irregularly shaped K‐feldspar flakes, and clear rims of albite. Textures of plagioclase in the mineralized aplitic veins are different from the idiomorphic textures with sharp plagioclase crystal boundaries that occur in the North granitic body and barren aplitic veins. These textural data suggest that the mineralized aplitic veins were formed from hydrothermal fluid. Changes in the contents of major and minor (Rb, Sr, Sc, Co, Th, U) elements in the North Miyako granitic body are similar to those of zoned plutons formed by typical magmatic differentiation processes. On the other hand, concentrations of REE, especially middle to heavy REE, of granitic rocks in zone C and barren aplitic veins are significantly lower than those of granitic rocks in zones A and B. The hypothetical chondrite‐normalized REE patterns, calculated assuming fractional crystallization from zone B granitic melt, suggest that REE concentrations of the residual melt increased with the degree of fractional crystallization, and changed into a pattern with enriched LREE and strongly negative Eu anomaly. However, the REE patterns of granitic rocks in zone C are different from the hypothetical patterns. Moreover, the REE patterns of magnetite–scheelite–chalcopyrite aplitic veins are quite different from those of granitic rocks. The Cu contents of granitic rocks in the North Miyako body increase from zone A (5–26 ppm) to zone B (10–26 ppm), and then clearly decrease to zone C (5–7 ppm) and drastically increase to the barren aplitic veins (39–235 ppm). Concentrations of Cu in the mineralized aplitic veins are also higher than those of the granitic rocks in zone C. The decrease in REE and Cu contents of granitic rocks from zone B to zone C is not a result of simple magmatic fractional differentiation. Fluid inclusions in quartz from mineralized aplitic veins contain 3.3 wt% NaCl equivalent and 5.8 wt% CO2. It was also demonstrated experimentally that the removal of MREE and HREE by fluid from melt enabled the formation of complexes of REE and ligands of OH‐ and CO32‐. Based on the possibility that the melt of the granitic rocks of zone C and the mineralized aplitic veins coexisted with CO2‐bearing fluid, it is thought that REE were extracted from the melt to the CO2‐bearing fluid, and that the REE in the mineralized aplitic veins were transported by the CO2‐bearing fluid. It is likely that the low HREE and Cu contents of the granitic rocks in zone C could have been caused by the removal of those elements from the granitic melt by the fluid coexisting with the melt. The expelled materials could have been the sources of scheelite–magnetite–chalcopyrite–bearing aplitic veins and copper mineralization of the Yamaguchi Cu‐W skarn deposit.  相似文献   

9.
The Xinlu Sn‐polymetallic ore field is located in the western Nanling Polymetallic Belt in northeastern Guangxi, South China, where a number of typical skarn‐, hydrothermal vein‐type tin deposits have developed. There are two types of Sn deposits: skarn‐type and sulfide‐quartz vein‐type. The tin mineralizations mainly occur on the south side of the Guposhan granitic complex pluton and within its outer contact zone. To constrain the Sn mineralization age and further understand its genetic links to the Guposhan granitic complex, a series of geochronological works has been conducted at the Liuheao deposit of the ore field using high‐precision zircon SHRIMP U‐Pb, molybdenite Re‐Os, and muscovite Ar‐Ar dating methods. The results show that the biotite‐monzogranite, which is part of the Xinlu intrusive unit of the Guposhan complex pluton, has a SHRIMP U‐Pb zircon age of 161.0 ± 1.5 Ma. The skarn‐type ore has a 40Ar‐39Ar muscovite plateau age of 160 ± 2 Ma (same as its isochron age), and the sulfide‐quartz vein‐type ore yields an Re‐Os molybdenite isochron age of 154.4 ± 3.5 Ma. The magmatic‐hydrothermal geochronological sequence demonstrated that the hydrothermal mineralization took place immediately following the emplacement of the monzogranite, with the skarn metasomatic mineralization stage predating the sulfide mineralization stage. Geochronologically, we have compared this ore field with 26 typical Sn deposits distributed along the Nanling Polymetallic Belt, leading to the suggestion of the magmatic‐metallogenic processes in the Xinlu ore field (ca. 161–154 Ma) as a component of the Early Yanshanian large‐scale Sn‐polymetallic mineralization event (peaked at 160–150 Ma) in the Nanling Range of South China. Petrogenesis of Sn‐producing granite and Sn‐polymetallic mineralization were probably caused by crust–mantle interaction as a result of significant lithospheric extension and thinning in South China in the Late Jurassic.  相似文献   

10.
All the indium-rich deposits with indium contents in ores more than 100×10- 6 seems to be of cassiterite-sulfide deposits or Sn-bearing Pb-Zn deposits, e.g., in the Dachang Sn deposit in Guangxi, the Dulong Sn-Zn deposit in Yunnan, and the Meng'entaolegai Ag-Pb-Zn deposit in Inner Mongolia, the indium contents in ores range from 98×10-6 to 236×10-6 and show a good positive correlation with contents of zinc and tin, and their correlation coefficients are 0.8781 and 0.7430, respectively. The indium contents from such Sn-poor deposits as the Fozichong Pb-Zn deposit in Guangxi and the Huanren Pb-Zn deposit in Liaoning are generally lower than 10×10-6, i.e., whether tin is present or not in a deposit implies the enrichment extent of indium in ores. Whether the In enrichment itself in the ore -forming fluids or the ore-forming conditions has actually caused the enrichment/depletion of indium in the deposits? After studying the fluid inclusions in quartz crystallized at the main stage of mineralization of several In-rich and In-poor deposits in China, this paper analyzed the contents and studied the variation trend of In, Sn, Pb and Zn in the ore-forming fluids. The results show that the contents of lead and zinc in the ore-forming fluids of In-rich and -poor deposits are at the same level, and the lead contents range from 22×10-6 to 81×10-6 and zinc from 164×10-6 to 309×10-6, while the contents of indium and tin in the ore-forming fluids of In-rich deposits are far higher than those of In-poor deposits, with a difference of 1-2 orders of magnitude. Indium and tin contents in ore-forming fluid of In-rich deposits are 1.9×10-6-4.1×10-6 and 7×100-6-55×10-6, and there is a very good positive correlation between the two elements, with a correlation coefficient of 0.9552. Indium and tin contents in ore-forming fluid of In-poor deposits are 0.03×10-6-0.09×10-6 and 0.4×10-6--2.0×10-6, respectively, and there is no apparent correlation between them. This indicates, on one hand, that In-rich ore-forming fluids are the material basis for the formation of In-rich deposits, and, on the other hand, tin probably played a very important role in the transport and enrichment of indium.  相似文献   

11.
The Yaoling tungsten deposit is a typical wolframite quartz vein‐type tungsten deposit in the South China metallogenic province. The wolframite‐bearing quartz veins mainly occur in Cambrian to Ordovician host rocks or in Mesozoic granitic rocks and are controlled by the west‐north‐west trending extensional faults. The ore mineralization mainly comprises wolframite and variable amounts of molybdenite, chalcopyrite, pyrite, fluorite, and tourmaline. Hydrothermal alteration is well developed at the Yaoling tungsten deposit, including greisenization, silicification, fluoritization, and tourmalinization. Three types of primary/pseudosecondary fluid inclusions have been identified in vein quartz, which is intimately intergrown with wolframite. These include two‐phase liquid‐rich aqueous inclusions (type I), two‐ or three‐phase CO2‐rich inclusions (type II), and type III daughter mineral‐bearing multiphase high‐salinity aqueous inclusions. Microthermometric measurements reveal consistent moderate homogenization temperatures (peak values from 200 to 280°C), and low to high salinities (1.3–39 wt % NaCl equiv.) for the type I, type II, and type III inclusions, where the CO2‐rich type II inclusions display trace amounts of CH4 and N2. The ore‐forming fluids are far more saline than those of other tungsten deposits reported in South China. The estimated maximum trapping pressure of the ore‐forming fluids is about 1230–1760 bar, corresponding to a lithostatic depth of 4.0–5.8 km. The δDH2O isotopic compositions of the inclusion fluid ranges from ?66.7 to ?47.8‰, with δ18OH2O values between 1.63 and 4.17‰, δ13C values of ?6.5–0.8‰, and δ34S values between ?1.98 and 1.92‰, with an average of ?0.07‰. The stable isotope data imply that the ore‐forming fluids of the Yaoling tungsten deposit were mainly derived from crustal magmatic fluids with some involvement of meteoric water. Fluid immiscibility and fluid–rock interaction are thought to have been the main mechanisms for tungsten precipitation at Yaoling.  相似文献   

12.
The Xiaojiashan tungsten deposit is located about 200 km northwest of Hami City, the Eastern Tianshan orogenic belt, Xinjiang, northwestern China, and is a quartz vein‐type tungsten deposit. Combined fluid inclusion microthermometry, host rock geochemistry, and H–O isotopic compositions are used to constrain the ore genesis and tectonic setting of the Xiaojiashan tungsten deposit. The orebodies occur in granite intrusions adjacent to the metamorphic crystal tuff, which consists of the second lithological section of the first Sub‐Formation of the Dananhu Formation (D2d 12). Biotite granite is the most widely distributed intrusive bodies in the Xiaojiashan tungsten deposit. Altered diorite and metamorphic crystal tuff are the main surrounding rocks. The granite belongs to peraluminous A‐type granite with high potassic calc‐alkaline series, and all rocks show light Rare Earth Element (REE)‐enriched patterns. The trace element characters suggest that crystallization differentiation might even occur in the diagenetic process. The granite belongs to postcollisional extension granite, and the rocks formed in an extensional tectonic environment, which might result from magma activity in such an extensional tectonic environment. Tungsten‐bearing quartz veins are divided into gray quartz vein and white quartz veins. Based on petrography observation, fluid inclusions in both kinds of vein quartz are mainly aqueous inclusions. Microthermometry shows that gray quartz veins have 143–354°C of Th, and white quartz veins have 154–312°C of Th. The laser‐Raman test shows that CO2 is found in fluid inclusions of the tungsten‐bearing quartz veins. Quadrupole mass spectrometry reveals that fluid inclusions contain major vapor‐phase contents of CO2, H2O. Meanwhile, fluid inclusions contain major liquid‐phase contents of Cl?, Na+. It can be speculated that the ore‐forming fluid of the Xiaojiashan tungsten deposit is characterized by an H2O–CO2, low salinity, and H2O–CO2–NaCl system. The range of hydrogen and oxygen isotope compositions indicated that the ore‐forming fluids of the tungsten deposit were mainly magmatic water. The ore‐forming age of the Xiaojiashan deposit should to be ~227 Ma. During the ore‐forming process, the magmatic water had separated from magmatic intrusions, and the ore‐bearing complex was taken to a portion where tungsten‐bearing ores could be mineralized. The magmatic fluid was mixed by meteoric water in the late stage.  相似文献   

13.
矽卡岩型锡矿是全球重要的锡金属来源,但是锡石沉淀成矿机制仍存在较大的争议。垄上矽卡岩型锡矿床位于湘东锡田锡多金属矿田中部,是南岭钨锡成矿带内矽卡岩型锡矿的典型代表。本文在野外考察、矿石矿相学、流体包裹体岩相学研究的基础上,采用流体包裹体组合法对垄上矽卡岩矿床不同矿化阶段代表矿物中的流体包裹体进行了详细研究。结果显示,垄上矽卡岩型多金属矿床成矿阶段可划分为矽卡岩阶段、退化蚀变阶段、云英岩-氧化物阶段、石英硫化物阶段以及萤石碳酸盐化等5个阶段,其中,锡石主要形成于云英岩-氧化物阶段。与锡石密切共生的石英中发育流体包裹体类型主要为富液相、富气相两相水溶液包裹体,含液相CO_(2)三相水溶液包裹体和纯CO_(2)型包裹体。流体温度和盐度具有较大的变化范围(200-400℃和2%-9%NaCleqv),指示流体在降温过程中经历了显著的不混溶。与硫化物共生的石英中主要为富液相两相水溶液包裹体,温度和盐度主要集中在190-261℃和3%-7%NaCleqv,指示流体冷却过程同时经历了流体混合。本次研究提出锡田矽卡岩型矿床中流体不混溶是导致云英岩-氧化物阶段锡石沉淀成矿的主要机制,而流体冷却和混合是导致硫化物沉淀的主要原因。  相似文献   

14.
Mineralogic studies of major ore minerals and fluid inclusion analysis in gangue quartz were carried out for the for the two largest veins, the Aginskoe and Surprise, in the Late Miocene Aginskoe Au–Ag–Te deposit in central Kamchatka, Russia. The veins consist of quartz–adularia–calcite gangue, which are hosted by Late Miocene andesitic and basaltic rocks of the Alnei Formation. The major ore minerals in these veins are native gold, altaite, petzite, hessite, calaverite, sphalerite, and chalcopyrite. Minor and trace minerals are pyrite, galena, and acanthine. Primary gold occurs as free grains, inclusions in sulfides, and constituent in tellurides. Secondary gold is present in form of native mustard gold that usually occur in Fe‐hydroxides and accumulates on the decomposed primary Au‐bearing tellurides such as calaverite, krennerite, and sylvanite. K–Ar dating on vein adularia yielded age of mineralization 7.1–6.9 Ma. Mineralization of the deposit is divided into barren massive quartz (stage I), Au–Ag–Te mineralization occurring in quartz‐adularia‐clays banded ore (Stage II), intensive brecciation (Stage III), post‐ore coarse amethyst (Stage IV), carbonate (Stage V), and supergene stages (Stage VI). In the supergene stage various secondary minerals, including rare bilibinskite, bogdanovite, bessmertnovite metallic alloys, secondary gold, and various oxides, formed under intensely oxidized conditions. Despite heavy oxidation of the ores in the deposit, Te and S fugacities are estimated as Stage II tellurides precipitated at the log f Te2 values ?9 and at log fS2 ?13 based on the chemical compositions of hypogene tellurides and sphalerite. Homogenization temperature of fluid inclusions in quartz broadly ranges from 200 to 300°C. Ore texture, fluid inclusions, gangue, and vein mineral assemblages indicate that the Aginskoe deposit is a low‐sulfidation (quartz–adularia–sericite) vein system.  相似文献   

15.
The Jinman Cu polymetallic deposit is located within Middle Jurassic sandstone and slate units in the Lanping Basin of southwestern China. The Cu mineralization occurs mainly as sulfide‐bearing quartz–carbonate veins in faults and fractures, controlled by a Cenozoic thrust–nappe system. A detailed study of fluid inclusions from the Jinman deposit distinguishes three types of fluid inclusions in syn‐ore quartz and post‐ore calcite: aqueous water (type A), CO2–H2O (type B), and CO2‐dominated (type C) fluid inclusions. The homogenization temperatures of CO2–H2O inclusions vary from 208°C to 329°C, with corresponding salinities from 0.6 to 4.6 wt.% NaCl equivalent. The homogenization temperatures of the aqueous fluid inclusions mainly range from 164°C to 249°C, with salinities from 7.2 to 20.2 wt.% NaCl equivalent. These characteristics of fluid inclusions are significantly different from those of basinal mineralization systems, but similar to those of orogenic or magmatic mineralization systems. The H and O isotope compositions suggest that the ore‐forming fluid is predominantly derived from magmatic water, with the participation of basinal brine. The δ34S values are widely variable between ?9.7 ‰ and 9.7 ‰, with a mode distribution around zero, which may be interpreted by the variation in physico‐chemical conditions or by compositional variation of the sources. The mixing of a deeply sourced CO2‐rich fluid with basinal brine was the key mechanism responsible for the mineralization of the Jinman deposit.  相似文献   

16.
Abstract: The southern segment of the Da Hinggan Mountains is a well‐known tin–polymetallic metallogenic belt of North China with Jurassic‐Cretaceous volcanic–plutonic rocks widespread. Principally because of this, most of the deposits are regarded as epigenetic hydrothermal deposits in genetic connection with the Mesozoic magmatism. But nearly 90 % of the deposits occur in Permian strata, and show concordant stratiform mineralization with a spatial distribution constrained by sedimentary facies of the Permian strata. A close association between mineralization and Permian strata is recognizable. The Huanggang Fe‐Sn deposit was regarded as a standard skarn‐type deposit formed by magmatic hydrothermal solutions in connection with Mesozoic granites. But there are abundant fabrics indicating submarine hydrothermal exhalation both in magnetite ores and in skarns, including bedding/lamination, soft–deformation, synsedimentary brecciation, and collo‐form fabrics. The magnetite orebodies and skarn‐bodies are predominantly concordant stratiform, and extend nearly 20 km along certain stratigraphic horizon, that is, the upper section of the Lower‐Permian submarine volcanic rocks. The Mesozoic granitic rocks crosscut the magnetite and skarn zone. Instead of skarnization, they show strong greisenization associated with cassiterite‐quartz veins, distinct from the magnetite skarn‐ore with disseminated tin in the Permian rocks. The Dajing Sn‐polymetallic deposit is generally regarded as subvolcanic‐hydrothermal origin, principally because of the close spatial association between ores and some of the Mesozoic subvolcanic dikes (called rhyolitic porphyry). Detailed geological, fabric, petrographical and mineralogical study demonstrates that this very kind of subvolcanic rocks is actually a new type of exhalites (called ‘siderite‐sericite chert’ according to its mineral assemblage), formed by hydrothermal sedimentation during the evolution of the Later‐Permian lacustrine basin. There are, however, indeed some rhyolitic porphyry dikes that crosscut orebod–ies. The orebodies and their associated exhalite predate, and thus have no genetic relation, to the Mesozoic magmatic process. We thus conclude that subaqueous exhalative mineralization did occur during the basin evolution at the Permian time in the southern segment of the Da Hinggan Mountains, which is ignored and poorly understood, but might be as important as the hydrothermal mineralization connected with the Mesozoic magmatism.  相似文献   

17.
Sn–W deposit of the Mueilha mine is one of many other Sn–W deposits in the Eastern desert of Egypt that associated with albite granite. Two forms of Sn–W mineralizations are known at the Mueilha Sn-mine area, namely fissure filling quartz veins and greisen. Cassiterite and/or wolframite, sheelite, and beryl are the main ore minerals in the greisen and quartz veins. Subordinate chalcopyrite and supergene malachite and limonite are also observed in the mineralized veins. To constrain the P–T conditions of the Sn–W mineralizations, fluid inclusions trapped in quartz and cassiterite, have been investigated. The following primary fluid inclusion types are observed: CO2-rich, two-phase (L?+?V) aqueous, and immiscible three-phase (H2O–CO2) inclusions. Low temperature and low salinity secondary inclusions were also detected in the studied samples. Microthermometric results revealed that Sn–W deposition seem to have taken place due to immiscibility at temperature between 260°C and 340°C, and estimated pressure between 1.2 to 2.2 kb. Microthermometric results of fluid inclusions in fluorite from fluorite veins illustrated that fluorite seems to be deposited due to mixing of two fluids at minimum temperature 140°C and 180°C, and estimated minimum pressure at 800 bars.  相似文献   

18.
芙蓉矿田白腊水锡矿矿化特征及找矿意义   总被引：7，自引：1，他引：6  
白腊水锡矿床是在新一轮地质大调查中发现,并进行了初步评价的大型矿床.该区断裂构造发育,构造线以NNE-NE向为主,并控制着锡矿带的分布.通过该矿床矿化特征的研究认为:①白腊水矿区到处发育的石英脉可能是锡矿化作用的同期产物;②矿脉内的锡矿化可能极不均匀,高品位的地段一般在构造破碎强烈地方;③该区不同岩体的成矿元素含量明显高于地壳花岗岩类岩石的平均值,有些高出数十倍,具良好的含矿性;④该地区的岩浆岩的稀土元素组成特征极为相似,岩(矿)石稀土元素球粒陨石标准化曲线具有相同的变化特点,显示出岩(矿)石可能为同一岩浆房演化的产物;同时反映出矿化可能与细粒花岗岩关系更密切.  相似文献   

19.
The Chitudian Zn‐Pb ore deposit, Luanchuan, Henan province, was recently discovered in the southern margin of the North China Craton. The Zn‐Pb orebodies are hosted in the Proterozoic Guandaokou and Luanchuan Groups, occurring as veins in interbedding fracture zones mainly in a WNW‐ and partially in a NS‐direction. The Zn‐Pb ores are characterized by banded, massive, and breccia structures, coarse crystal grains, and a simple mineral composition mainly of galena, sphalerite, pyrite, quartz, dolomite, and calcite. In addition to the vein type orebodies, there are Mo‐ and Zn‐bearing skarn orebodies in the northwest of the Chitudian ore field. Four types of primary fluid inclusions in quartz and calcite were recognized in the Chitudian Zn‐Pb ores, including aqueous, aqueous‐CO2, daughter‐mineral‐bearing aqueous, and daughter‐mineral‐bearing aqueous‐CO2 inclusions, with aqueous inclusion being most common. The homogenization temperatures of the fluid inclusions from the main mineralization stage are from 290°C to 340°C, and the salinities mainly from 3.7 to 14.8 wt% NaCl equivalent. In addition to CO2, CH4 and H2S were detected in the vapor phase and HS‐ in the liquid phase of the fluid inclusions by Laser Raman spectroscopy. The δ34SV‐CDT values of ore sulfides from the Chitudian deposit range from ?0.32‰ to 8.30‰, and show two modal peaks in the histogram, one from 1‰ to 4‰, and the other from 5‰ to 7‰. The former peak is similar to that of porphyry‐type Mo‐W deposits in the area, whereas the latter is relatively close to the sulfur in the strata. The ore sulfur may have been derived from both the magma and the strata. The Pb‐isotopic compositions of the ore minerals from Chitudian, with 206Pb/204Pb from 17.005 to l7.953, 207Pb/204Pb from 15.414 to 15.587, and 208Pb/204Pb from 37.948 to 39.036, are similar to those of Mesozoic porphyries in the Chitudian ore field, suggesting that the ore‐forming metals were mainly derived from the Mesozoic magmatic intrusions. The Chitudian Zn‐Pb deposit is interpreted to be a distal hydrothermal vein‐type deposit, which was genetically related to the proximal, skarn‐type Mo ore deposits in the region.  相似文献   

20.
The Miocene Qulong porphyry Cu‐Mo deposit, which is located at the Gangdese orogenic belt of Southern Tibet, is the largest porphyry‐type deposit in China, with confirmed Cu ～10 Mt and Mo ～0.5 Mt. It is spatially and temporally associated with multiphase granitic intrusions, which is accompanied by large‐scale hydrothermal alteration and mineralization zones, including abundant hydrothermal anhydrite. In addition to hydrothermal anhydrite, magmatic anhydrite is present as inclusions in plagioclase, interstitial minerals between plagioclase and quartz, and phenocrysts in unaltered granodiorite porphyry, usually in association with clusters of sulfur‐rich apatite in the Qulong deposit. These observations indicate that the Qulong magma‐hydrothermal system was highly oxidized and sulfur‐rich. Three main types of fluid inclusions are observed in the quartz phenocrysts and veins in the porphyry: (i) liquid‐rich; (ii) polyphase high‐salinity; and (iii) vapor‐rich inclusions. Homogenization temperatures and salinities of all type inclusions decrease from the quartz phenocrysts in the porphyry to hydrothermal veins (A, B, D veins). Microthermometric study suggests copper‐bearing sulfides precipitated at about 320–400°C in A and B veins. Fluid boiling is assumed for the early stage of mineralization, and these fluids may have been trapped at about 35–60 Mpa at 460–510°C and 28–42 Mpa at 400–450°C, corresponding to trapping depths of 1.4–2.4 km and 1.1–1.7 km, respectively.  相似文献   

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