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1.
The author’s database, which presently includes data from more than 18500 publications on fluid and melt inclusions in minerals and is continuing to be appended, was used to generalize results on physicochemical parameters of the formation of hydrothermal deposits and occurrences of tin and tungsten. The database includes data on 320 tin and tin-tungsten deposits and occurrences and 253 tungsten and tungstentin deposits around the world. For most typical minerals of these deposits (quartz, cassiterite, tungsten, scheelite, topaz, beryl, tourmaline, fluorite, and calcite), histograms of homogenization temperatures of fluid inclusions were plotted. Most of 463 determinations made for cassiterite are in the range of 300–500°C with maximum at 300–400°C, while those for wolframite and scheelite (453 determinations) fall in the range of 200–400°C with maximum at 200–300°C. Representative material on pressures of hydrothermal fluids included 330 determinations for tin and 430 determinations for tungsten objects. It was found that premineral, ore, and postmineral stages spanned a wide pressure range from 70–110 bar to 6000–6400 bar. High pressures of the premineral stages at these deposits are caused by their genetic relation with felsic magmatism. Around 50% of pressure determinations lie in the range of 500–1500 bar. The wide variations in total salinity and temperatures (from 0.1 to 80 wt % NaCl equiv and 20–800°C) were obtained for mineral-forming fluids at the tin (1800 determinations) and tungsten (2070 determinations) objects. Most of all determinations define a salinity less than 10 wt % NaCl equiv. (∼60%) and temperature range of 200–400°C (∼70%). The average composition of volatile components of fluids determined by different methods is reported. Data on gas composition of the fluids determined by Raman spectroscopy are examined. Based on 180 determinations, the fluids from tin objects have the following composition (in mol %): 41.2 CO2, 39.5 CH4, 19.15 N2, and 0.15 H2S. The volatile components of tungsten deposits (190 determinations) are represented by 56.1 CO2, 30.7 CH4, 13.2 N2, and 0.01 H2S. Thus, the inclusions of tungsten deposits are characterized by higher CO2 content and lower (but sufficiently high) contents of CH4 and N2. The concentrations of tin and tungsten in magmatic melts and mineral-forming fluids were estimated from analysis of individual inclusions. The geometric mean Sn contents are 87 ppm (+ 610 ppm/−76 ppm) in the melts (569 determinations) and 132 ppm (+ 630 ppm/−109 ppm) in the fluids (253 determinations). The geometric mean W values are 6.8 ppm (+ 81/−6.2 ppm) in the magmatic melts (430 determinations) and 30 ppm (+ 144 ppm/−25 ppm) in the mineral-forming fluids (391 determinations).  相似文献   

2.
The authors’ database (which includes data from more than 17500 publications on fluid and melt inclusions in minerals) was used to generalize information on the principal physicochemical parameters of natural mineral-forming fluids (temperature, pressure, density, salinity of aqueous solutions, and the gas composition of the fluids). For 21 minerals, data are reported on the frequency of occurrence of the homogenization temperatures of fluid inclusions in various temperature ranges, which make it possible to reveal temperature ranges most favorable for the crystallization of these minerals. Data on 5260 determinations were used to evaluate the frequency of occurrence of certain temperature and pressure ranges of natural fluids within the temperature intervals of 20–1200°C and 1–12000 bar. Within these intervals, frequencies of occurrence were evaluated for water-dominated and water-poor or water-free fluid inclusions in minerals. The former are predominant at temperatures below 600°C and pressures below 4000 bar, whereas the latter dominate at temperatures of 600–1200°C and pressures of 4000-12000 bar. Illustrative examples are presented for visually discernible magmatic water that exists as an individual high-density phase in melt inclusions in minerals from various rocks sampled worldwide (in the Caucasus, Italy, Slovakia, United States, Uzbekistan, New Zealand, Chile, and others). Attention is drawn to the fact that extensive data testify to fairly high (>1000–1500 bar) pressures during hydrothermal mineral-forming processes. These pressures are much higher not only than the hydrostatic but also the lithostatic pressures of the overlying rocks. Data on more than 18000 determinations are used to evaluate the frequency of occurrence of certain temperature and salinity ranges of mineral-forming fluids within the intervals of 20–1000°C and 0–80 wt % equiv. NaCl and certain temperature and density ranges of these fluids at 20–1000°C and 0.01–1.90 g/cm3. Information is presented on the gas analysis methods most commonly applied to natural fluids in studying fluid inclusions in minerals in 1965–2007. The average composition of the gaseous phase of natural inclusions is calculated based on more than 3000 Raman spectroscopic analyses (the most frequently used method for analyzing individual inclusions).  相似文献   

3.
The Asachinskoe epithermal Au-Ag deposit (southern Kamchatka) is referred to as low-sulfidation in quartz-adularia-sericite in Corbett's classification. Research into fluid inclusions of its minerals gave an insight into the PT-conditions of formation and gas composition of ore-forming fluids as well as the vertical variations in these parameters to a depth of more than 200 m within a 2 km long horizontal site of the deposit ore zone. It is shown that mineral assemblages formed at 320 to <100 °C. Ore-forming hydrothermal solutions were poor in salts (3–9.2 wt.% NaCl equiv.), with NaCl being the main component. Mineral assemblages with high contents of Au crystallized at 250–175 °C. Ore-free quartz-carbonate veins formed at 80–120 °C. High-temperature (300–320 °C) veins also lack ores. Rich gold ores were deposited in the environments where ore-bearing fluids boiled, mixing with meteoric waters.  相似文献   

4.
Melt inclusions and aqueous fluid inclusions in quartz phenocrysts from host felsic volcanics, as well as fluid inclusions in minerals of ores and wall rocks were studied at the Cu-Zn massive sulfide deposits in the Verkhneural’sk ore district, the South Urals. The high-temperature (850–1210°C) magmatic melts of volcanic rocks are normal in alkalinity and correspond to rhyolites of the tholeiitic series. The groups of predominant K-Na-type (K2O/Na2O = 0.3–1.0), less abundant Na-type (K2O/Na2O = 0.15–0.3), and K-type (K2O/Na2O = 1.9–9.3) rhyolites are distinguished. The average concentrations (wt %) of volatile components in the melts are as follows: 2.9 H2O (up to 6.5), 0.13 Cl (up to 0.28), and 0.09 F (up to 0.42). When quartz was crystallizing, the melt was heterogeneous, contained magnetite crystals and sulfide globules (pyrrhotite, pentlandite, chalcopyrite, bornite). High-density aqueous fluid inclusions, which were identified for the first time in quartz phenocrysts from felsic volcanics of the South Urals, provide evidence for real participation of magmatic water in hydrothermal ore formation. The fluids were homogenized at 124–245°C in the liquid phase; the salinity of the aqueous solution is 1.2–6.2 wt % NaCl equiv. The calculated fluid pressure is very high: 7.0–8.7 kbar at 850°C and 5.1–6.8 kbar at 700°C. The LA-ICP-MS analysis of melt and aqueous fluid inclusions in quartz phenocrysts shows a high saturation of primary magmatic fluid and melt with metals. This indicates ore potential of island-arc volcanic complexes spatially associated with massive sulfide deposits. The systematic study of fluid inclusions in minerals of ores and wall rocks at five massive sulfide deposits of the Verkhneural’sk district furnished evidence that ore-forming fluids had temperature of 375–115°C, pressure up to 1.0–0.5 kbar, chloride composition, and salinity of 0.8–11.2 (occasionally up to 22.8) wt % NaCl equiv. The H and O isotopic compositions of sericite from host metasomatic rocks suggest a substantial contribution of seawater to the composition of mineral-forming fluids. The role of magmatic water increases in the central zones of the feeding conduit and with depth. The dual nature of fluids with the prevalence of their magmatic source is supported by S, C, O, and Sr isotopic compositions. The TC parameters of the formation of massive sulfide deposits are consistent with the data on fluid inclusions from contemporary sulfide mounds on the oceanic bottom.  相似文献   

5.
Homogenization temperature and salinity were determined for fluid inclusions in mostly quartz and partly sphalerite, cassiterite, and barite from the 28 tin-polymetallic ore deposits in Bolivia. Generally, the homogenization temperatures and salinities of these fluid inclusions are comparatively high for ore deposits formed by cassiterite mineralization, such as Morococala and Avicaya in the Oruro district, frequently indicating a temperature higher than 300°C and salinity higher than 20 equiv. wt% NaCl. Particularly, it is quite possible that tin deposits associated with the W-Bi and tourmaline mineralizations such as Viloco and Caracoles have been produced by such high-temperature hypersaline fluid ranging up to 500°C and 56 equiv. wt% NaCl, similar to the porphyry copper type. This feature reveals that the hydrothermal fluid related to the Sn-W-Bi mineralization may be of magmatic origin. Homogenization temperatures for the Pb-Zn deposits with no tin minerals are low, mostly ranging 170°–300°C. At the Avicaya-Bolivar mining area in the Oruro district as well as at the Tasna and Chocaya-Animas mining areas in the Quechisla district temperature gradients consistent with the zonal distributions of ore minerals were confirmed.  相似文献   

6.
Physicochemical factors of formation of Au-As,Au-Sb,and Ag-Sb deposits   总被引:1,自引:0,他引:1  
The physicochemical formation conditions of Au-As, Au-Sb, and Ag-Sb ores characterized by similar paragenetic mineral assemblages and sets of major ore elements but differing in their proportions have been studied. The composition of the solutions filling fluid inclusions in minerals of Au-Sb deposits, combined with mineralogical and geochemical data, indicates that these deposits were formed from a near-neutral to alkalescent chloride-sulfide (<5 wt % NaCl) solution. Au-As and Au-Sb deposits were formed from fluids of the same type, consisting of a predominately CO2-CH4 gas phase with N2 and a low-saline chloride-sulfide solution, where Au and Ag were predominantly transported as dihydrosulfide species and Sb as sulfide and hydroxy complexes. Superimposed minerals of the sulfide-sulfosalt stage that precipitated from chloride-rich solutions (up to 30 wt % NaCl equiv), which contained Ca and Fe chlorides in addition to NaCl, are identified at some Au-Sb deposits. These solutions are similar in composition to the ore-forming fluids of Ag-Sb deposits. Chloride complexes are dominant Au and Ag species in acid chloride-rich solutions of Ag-Sb deposits (up to 38 wt % NaCl equiv), while chloride and hydroxy complexes are characteristic of Sb. These solutions are distinguished by high concentrations of Ag, Sb, Cu, Fe, Mn, Bi, Pb, and Zn. The mineralogical and geochemical specialization of Ag-Sb ore is caused by chemical features of highly concentrated chloride solutions enriched in Ag, Sb, and Cu and by a relatively low Au content within the pH interval 3.5–4.0 (10?6 m). The factors controlling formation of Au-As deposits are a high capacity of a low-chloride sulfide solution with respect to metals and a high Au concentration therein (two orders higher than that of solutions of Ag-Sb deposits). The enrichment of the pyrite-arsenopyrite paragenetic assemblage in gold is a result of juxtaposed stability fields of native gold, arsenopyrite, and pyrite and their mass deposition with a decrease in temperature from 400 to 300°C. The main cause of the specific mineralogy and geochemistry of Au-Sb deposits is a high metal capacity of a near-neutral low-chloride sulfide fluid with respect to Sb, Au, and Ag, but a low Ag content. The mineralogical and fluid inclusion data combined with computer thermodynamic simulation allowed us to establish the factors of ore formation at P-T-X parameters close to natural conditions and made it possible to characterize the joint deposition of gold and silver in quantitative terms.  相似文献   

7.
Physicochemical parameters of the origin of Cu and Mo deposits are reviewed based on an original database that currently includes information from more than 21000 publications on fluid and melt inclusions hosted in various minerals. The deposits are classified into three types: (i) Cu–Mo (usually porphyry), (ii) Cu (usually without Mo but often with base metals), and (iii) Mo (without Cu but often with Be and W). For these deposits, the temperature and pressure of their origin and the density, salinity, and gas composition of the fluids are discussed. The average composition of the dominant volatile components of natural fluids is reported for Cu and Mo deposits and is compared with the composition of volatiles in fluids at Au, Sn, W, Pb, and Zn deposits. Data on individual inclusions are used to evaluate the Cu and Mo concentrations in the magmatic silicate melts and mineral-forming fluids.  相似文献   

8.
The first data on study of individual fluid inclusions in the Zhilnoye deposit have been obtained. It has been found that the gold-bearing quartz veins of the deposit were formed by heterogeneous hydrothermal fluids with low salt concentrations (0.2–3.6 wt% equiv. NaCl under intermediate temperature conditions of 246–350°C). The fluid pressure was 80–160 bar corresponding to 0.3–0.6 km depths of formation under hydrostatic conditions. The parameters of the mineral-forming fluids of the Zhilnoye deposit correspond to typical parameters of the fluids of epithermal deposits.  相似文献   

9.
In this review, we describe the geological characteristics and metallogenic–tectonic origin of Fe deposits in the Altay orogenic belt within the Xinjiang region of northwestern China. The Fe deposits are found mainly within three regions (ordered from northwest to southeast): the Ashele, Kelan, and Maizi basins. The principal host rocks for the Fe deposits of the Altay orogenic belt are the Early Devonian Kangbutiebao Formation, the Middle to Late Devonian Altay Formation, with minor occurrences of Lower Carboniferous and Early Paleozoic metamorphosed volcano-sedimentary rocks. The principal mineral-forming element groups of the deposits are Fe, Fe–Cu, Fe–Mn, Fe–P, Fe–Pb–Zn, Fe–Au, and Fe–V–Ti. The Fe deposits are associated with distinct formations, such as volcanic rocks, skarn deposits, pegmatites, granite-related hydrothermal vein mineralization, and mafic pluton-related V–Ti-magnetite deposits. The Fe deposits are most commonly associated with volcanic rocks in the upper Kangbutiebao Formation, in the volcano-sedimentary Kelan Basin, and in skarn deposits at several localities, including the lower Kangbutiebao Formation in the volcano-sedimentary Maizi Basin, and the Altay Formation at Jiaerbasidao–Kekebulake region. Homogenization temperatures of fluid inclusions in the prograde, retrograde and sulfide stages of the skarn type deposit are mainly medium- to high-temperature (cluster between 200 and 500 °C), medium-temperature (cluster between 200 and 340 °C) and low- to medium temperature (cluster between 160 and 300 °C), respectively. Ore fluids in the sedimentation period in the volcano-sedimentary type deposit are characterized by low- to medium temperature (with a peak around 190 °C), low to moderate salinity (3.23 to 22.71 wt.% NaCl equiv). Ore fluids in the pegmatite type deposit are characterized by low- to medium temperature (with a peak at 240 °C), low salinity (with a peak around 9 wt.% NaCl equiv). An analysis of the isotopic data for Fe deposits from the Altay orogenic belt indicates that the sulfur was derived from several sources, including volcanic rocks and granite, as well as bacterial reduction of sulfate from seawater. The present results indicate that different deposit types were derived from various sources. The REE geochemistry of rocks and ores from the Fe deposits in the Altay orogenic belt suggests that the ore-forming materials were derived from mafic volcanic rocks. Based on isotopic age data, the timing of the mineralization can be divided into four broad intervals: Early Devonian (410–384 Ma), Middle Devonian (377 Ma), Early Permian (287–274 Ma), and Early Triassic (c. 244 Ma). The ore-forming processes of the Fe deposits are closely related to volcanic activity and the emplacement of intermediate and felsic intrusions. We conclude that Fe deposits within the Altay orogenic belt developed in a range of tectonic settings, including continental arc, post-collisional extensional settings, and intracontinental settings.  相似文献   

10.
There are 10 types of tungsten ore deposits in South China: granite, porphyry, volcanic, pegmatite, skarn, greisen, wolframite-quartz ± microcline veins, stratabound, ferberite-quartz veins and placer. Most are chronologically related to Yenshanian granites. Integrated field, mineralogic, fluid inclusion and geochemical studies were undertaken to determine the characteristics and origin of the ores. Most of the tungsten ore deposits are also spatially related to Yenshanian granites. These granites include several intrusions, isotopically dated at 160–180 m. y. and 70–100 m. y. The concentration of trace elements, especially W Mo, Sn, Ta, Nb, Li, and F are relatively high in the granites. In the granites of South China, the average WO3 is 4.35 ppm, but in Yenshanian granites, which are the youngest of these, the average WO3 is 5.16 ppm. In the youngest of Yenshanian granites, a light mica-albite granite has been identified, whose average WO3 is as high as 242.3 ppm. From this line of evidence, the tungsten ore deposits in South China are considered to be genetically related to Yenshanian granites. Wolframite-sulfide-quartz veins and scheelite skarns provide the bulk of the reserves and production. There are many different kinds of alteration associated with the different tungsten ore deposits, but the principal ones are silicification, greisenization, potash-feldspathization and chloritization. Four types of fluid inclusions were found:
  1. Liquid-rich;
  2. Gas-rich;
  3. Liquid CO2-bearing;
  4. Polyphase with daughter minerals.
Most common are type I inclusions. Type IV fluid inclusions only appeared in the porphyry and skarns. In skarns, type IV inclusions are evidently confined to the early stage, i.e., the simple silicate stage, but in the later scheelite mineralization stage, only types I and III inclusions occurred. Types II and III were found in the wolframite-quartz-sulfide veins, especially at the top of the veins. Homogenization temperature and salinity were determined on the inclusions, and the pressure of formation was estimated from the inclusions. The homogenization temperatures of some of these types of tungsten ore deposits are as follows: porphyry, 386°C; greisen, 244–301°C; granite, 220°C; wolframite-sulfide-quartz veins, 240–310°C; wolframite-microcline-quartz veins, 267–325°C; stratabound, 219°C; and ferberite-quartz veins. 142°C. The salinity of fluid inclusions in the wolframite-sulfide-quartz veins type was only 5–10% equiv. NaCl. The pressures of formation, determined from the tomperature of homogenization, volume and density of phases in H2O-CO2 inclusions, from veins in three different wolframite-sulfide-quartz deposits, were 450, 550, and 750 atm., respectively. Most of the tungsten ore deposits were formed between 220°C and 390°C, with the porphyry highest and the ferberite-quartz veins type lowest. In the wolframite sulfide-quartz veins, four stages can be recognized: oxide-silicate; wolframitequartz-beryl; wolframite-quartz-sulfide; and carbonate. Throughout this sequence, the salinity and temperature decrease, e. g., from 293°C to 129°C. It is concluded that these particular tungsten deposits were formed from a dilute water solution at moderate to high temperatures and at moderate pressures.  相似文献   

11.
The Chalukou giant Mo deposit in the Heilongjiang Province, northeastern China, is a porphyry deposit hosted in an intermediate‐felsic complex surrounded by Mesozoic volcano–sedimentary rocks. The mineralization process is composed of four stages, including quartz + K‐feldspar (Stage I), quartz + molybdenite (Stage II), pyrite + chalcopyrite + quartz ± other sulphides (Stage III) and carbonate ± fluorite ± quartz (Stage IV). The mineralization is generally associated with intense K‐feldspar‐, fluorite‐, phyllic‐ and propylitic alteration. Primary fluid inclusions (FIs) in quartz include four compositional types, i.e. pure carbonic (PC‐type), aqueous‐carbonic (C‐type), daughter mineral‐bearing (S‐type) and aqueous (W‐type) inclusions. Halite, sylvite and hematite are recognized as the daughter minerals in Stage I S‐type FIs, whereas molybdenite and chalcopyrite occur as daughter minerals in Stage II S‐type FIs. High‐salinity and high pressure (>220 MPa) FIs exist in Stage I quartz veins, characterized by homogenization through halite dissolution at temperatures of 324 to 517 °C. The paucity of coexisting vapour‐rich FIs with similar homogenization temperatures at this stage indicates that the initial S‐type inclusions have directly exsolved from the magma rather than boiling off of a low‐salinity vapour. Stage I quartz has captured the C‐ and W‐type FIs, which have totally homogenized at 270–530 °C with salinities of 1.6–17.0 wt.% NaCl equiv. At Stage II, the coexistence of all FI types were only observed at pressures of 150–218 MPa and temperatures of 352–375 °C, with two salinity clusters of 0.9–16.6 wt.% NaCl equiv. and 37–56 wt.% NaCl equiv. Stage III quartz contains W‐type FIs with homogenization temperatures of 158–365 °C, salinities of 0.5–9.0 wt.% NaCl equiv., and minimum pressures of 12–116 MPa; whilst Stage IV fluorite or calcite only contains W‐type FIs with homogenization temperatures of 121–287 °C, salinities of 0.5–5.3 wt.% NaCl equiv., and minimum pressures of 10–98 MPa. The estimated trapping pressure from Stages II to III suggests an alternating lithostatic–hydrostatic fluid‐system caused by fluid boiling. Ore fluids at the Chalukou Mo deposit may have been evolved from a CO2‐rich, high‐salinity, and high‐oxygen fugacity (fO2) magma system, to a CO2‐poor, low‐salinity, and low‐fO2 epithermal system. Two key points may have contributed to the formation of the Chalukou giant Mo deposit: The magmatic origin and fluid boiling that has resulted in decompression and rapid precipitation of metals. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

12.
The Phu Lon skarn Cu–Au deposit is located in the northern Loei Fold Belt (LFB), Thailand. It is hosted by Devonian volcano-sedimentary sequences intercalated with limestone and marble units, intruded by diorite and quartz monzonite porphyries. Phu Lon is a calcic skarn with both endoskarn and exoskarn facies. In both skarn facies, andradite and diopside comprise the main prograde skarn minerals, whereas epidote, chlorite, tremolite, actinolite and calcite are the principal retrograde skarn minerals.Four types of fluid inclusions in garnet were distinguished: (1) liquid-rich inclusions; (2) daughter mineral-bearing inclusions; (3) salt-saturated inclusions; and (4) vapor-rich inclusions. Epidote contains only one type of fluid inclusion: liquid-rich inclusions. Fluid inclusions associated with garnet (prograde skarn stage) display high homogenization temperatures and moderate salinities (421.6–468.5 °C; 17.4–23.1 wt% NaCl equiv.). By contrast, fluid inclusions associated with epidote (retrograde skarn stage) record lower homogenization temperatures and salinities (350.9–399.8 °C; 0.5–8 wt% NaCl equiv.). These data suggest a possible mixing of saline magmatic fluids with external, dilute fluid sources (e.g., meteoric fluids), as the system cooled. Some fluid inclusions in garnet contain hematite daughters, suggesting an oxidizing magmatic environment. Sulfur isotope determinations on sulfide minerals from both the prograde and retrograde stages show a uniform and narrow range of δ34S values (?2.6 to ?1.1 δ34S), suggesting that the ore-forming fluid contained sulfur of orthomagmatic origin. Overall, the Phu Lon deposit is interpreted as an oxidized Cu–Au skarn based on the mineralogy and fluid inclusion characteristics.  相似文献   

13.
湖南东坡柴山-蛇形坪一带铅锌矿床流体包裹体研究   总被引:2,自引:1,他引:1  
东坡柴山-蛇形坪一带铅锌矿床位于千里山岩体西南侧的远接触带上,由脉状、柱状和席状的铅锌矿体组成,在矿体周围明显发生碳酸盐化和硅化作用。该带矿床中闪锌矿、萤石、石英和方解石内流体包裹体类型主要包括富液相包裹体、富气相包裹体和含子矿物包裹体;其流体包裹体的均一温度范围为140~395℃,在350℃、240~260℃和200~220℃处分别出现峰值,反映该期热液流体在形成脉状、柱状铅锌矿体过程中可能包含了不同的捕获事件,其中方解石内出现的气体包裹体同与其共生的液体包裹体的均一温度相近,两者均一温度范围主要集中在268~395℃,峰值为350℃,液相包裹体w(NaCleq)范围为9%~11%,表明流体发生过气液相分离的沸腾作用;闪锌矿、萤石、石英和方解石中流体包裹体w(NaCleq)范围为0~23%,峰值9%~10%。流体包裹体的均一温度和盐度特征与岩浆热液流体演化到裂隙阶段静水压力条件下的流体相近。闪锌矿中流体包裹体内存在方解石和白云石子矿物,表明铅锌矿的成矿作用发生在富集碳酸盐的热液流体中。千里山花岗岩体晚期释放的流体沿着不同的通道上升,当它冷却到低于400℃,这些地区产生了脆性裂隙,流体沿着裂隙继续上升,并且发生沸腾作用,因此,温度在340~400℃时,w(NaCleq)为7%左右的流体分成了w(NaCleq)约10%的液相流体和w(NaCleq)约0.02%的气相流体,由于温度和压力的迅速降低,成矿物质沿着裂隙和空洞沉淀成矿,形成了东坡矿区的脉状、柱状和席状的铅锌矿体。  相似文献   

14.
The succession of mineral assemblages, chemistry of gangue and ore minerals, fluid inclusions, and stable isotopes (C, O, S) in minerals have been studied in the Mangazeya silver–base-metal deposit hosted in terrigenous rocks of the Verkhoyansk Fold–Thrust Belt. The deposit is localized in the junction zone of the Kuranakh Anticlinorium and the Sartanga Synclinorium at the steep eastern limb of the Endybal Anticline. The deposit is situated at the intersection of the regional Nyuektame and North Tirekhtyakh faults. Igneous rocks are represented by the Endybal massif of granodiorite porphyry 97.8 ± 0.9 Ma in age and dikes varying in composition. One preore and three types of ore mineralization separated in space are distinguished: quartz–pyrite–arsenopyrite (I), quartz–carbonate–sulfide (II), and silver–base-metal (III). Quartz and carbonate (siderite) are predominant in ore veins. Ore minerals are represented by arsenopyrite, pyrite, sphalerite, galena, fahlore, and less frequent sulfosalts. Three types of fluid inclusions in quartz differ in phase compositions: two- or three-phase aqueous–carbon dioxide (FI I), carbon dioxide gas (FI II), and two-phase (FI III) containing liquid and a gas bubble. The homogenization temperature and salinity fall within the ranges of 367–217°C and 13.8–2.6 wt % NaCl equiv in FI I; 336–126°C and 15.4–0.8 wt % NaCl equiv in FI III. Carbon dioxide in FI II was homogenized in gas at +30.2 to +15.3°C and at +27.2 to 29.0°C in liquid. The δ34S values for minerals of type I range from–1.8 to +4.7‰ (V-CDT); of type II, from–7.4 to +6.6‰; and of type III, from–5.6 to +7.1‰. δ13C and δ18O vary from–7.0 to–6.7‰ (V-PDB) and from +16.6 to +17.1 (V-SMOW) in siderite-I; from–9.1 to–6.9‰ (V-PDB) and from +14.6 to +18.9 (V-SMOW) in siderite-II; from–5.4 to–3.1‰ (V-PDB) and from +14.6 to +19.5 (V-SMOW) in ankerite; and from–4.2 to–2.9‰ (V-PDB) and from +13.5 to +16.8 (V-SMOW) in calcite. The data on mineral assemblages, fluid inclusions, and ratios of stable isotopes allow us to speak about the formation of the Mangazeya deposit in relation to the activity of the hydrothermal–magmatic system. The latter combines emplacement of subvolcanic granitic stocks and involvement of fluids variable in salinity and temperature in ore deposition zone. The fluids released from crystallizing felsic magma and were formed in a convective cell by heating of meteoric and marine waters. The mechanism of ore deposition is related to phase separation (boiling) and mixing of fluids.  相似文献   

15.
Lianhuashan mine in South China represents a new type of tungsten ore which can be described as a porphyry tungsten deposit. It is associated with a quartz porphyry stock of Yenshanian age (about 70–135 m. y.). The ore occurs in zone surrounding the contact of the quartz porphyry with Jurassic sandstone and extends into both rock bodies. The ore occurs either as the matrix of breccia or in the form of a very fine network of cross cutting veinlets. The major tungsten minerals are wolframite and scheelite associated with sulfide minerals of Mo, Fe, Cu, Pb and cassiterite. The minerals are fine-grained. There is zoned alteration in the wall rocks. From the center of the quartz porphyry toward the wall rocks one finds: potassic alteration, silicification-sericitization, and chloritization. All these features are similar to those of porphyry copper mineralization. Fluid inclusion studies show three types of inclusion: liquid-rich (Type I), gas-rich (Type II), and polyphase with daughter minerals (Type III) fluid inclusions. The homogenization temperatures of Type I range from 210° to 380°C, with a salinity of 2–15 wt.% NaCl equiv., those of Type II from 270° to 420°C, and those of Type III from 240° to 400°C with a salinity of 31–33 wt.% NaCl equiv. The closely associated group of gas-rich and daughter mineral-bearing fluid inclusions homogenized at almost the same temperatures. Such results indicate boiling of oreforming fluids. These fluid inclusion data indicate that low salinity (Type I) and high salinity fluids (Type III) responsible for porpb yry copper deposits are the same as those for porphyry tungsten ore deposits. These observations suggest that the Lianhuashan tungsten ore deposit is a porphyry tungsten deposit and was formed by hydrothermal fluids similar to those responsible for the well-known porphyry copper deposits.  相似文献   

16.
The Engteri is a new hidden Au-Ag deposit in the Russian segment of the Pacific ore belt. The discovery of this deposit merits special attention, because it involves repeated attempts to reappraise a lowprospective ore occurrence, which were crowned with success as a result of fulfillment of large-scale drilling project. The average Au grade is 18.6 gpt. The deposit is classified as the gold geochemical type of Au-Ag deposits. The major ore mineral is pyrite, which amounts to no less than 95% of the total ore minerals. The native phases comprise electrum and to a lesser extent native gold of low fineness (730). The homogenization temperature of fluid inclusions is 125–255°C with a distinct maximum at 145–150°C. Despite blind localization of some orebodies, the Engteri deposits bears evidence for a deep erosion level: (1) small vertical range of economic mineralization (50–100 m); (2) predominant occurrence of massive sugarlike quartz with a low sulfide content; (3) prevalence of massive and brecciated textures above rhythmically banded textures; and (4) lack of low-temperature propylites. The southern part of the ore field distinguished by occurrence of rhythmically banded, framework-tabular, and brecciated texture has the best prospect for revealing new orebodies. The Engteri deposit allowed us to outline the following prospecting guides and methods of prospecting for hidden Au-Ag deposits: (1) these deposits are regularly arranged in ore clusters between heavy concentrate anomalies of cinnabar and gold-silver or silver-base-metal occurrences (method of missed link); (2) findings of fragments of ore mineral assemblages with sporadically high Au and Ag contents in barren calcite-quartz veins (method of indicators); (3) linear zones of ankeritization in the fields of low- and mediumtemperature propylites (mapping of metasomatic rocks); and (4) pyrite-quartz veinlets with rhythmically banded pockets (mineralogical mapping of halos of stringer-disseminated mineralization).  相似文献   

17.
The Dongpo tungsten ore deposit, the largest scheelite skarn deposit in China, is located at the contact of a 172-m. y. biotite granite with a Devonian marble. The mineralization associated with the granite includes W, Bi-Mo, Cu-Sn and Pb-Zn ores. Several W mineralization stages are shown by the occurrence of ore in massive skarn deposits and in later cross-cutting veins. The high garnet/pyroxene ratio, the hedenbergite and diopside-rich pyroxene and the andradite-rich garnet show the deposit belongs to the oxidized skarn type. Detailed fluid inclusion studies of granite, greisen, skarn and vein samples reveal three types of fluid inclusion: (1) liquid-rich, (2) gas-rich and (3) inclusions with several daughter minerals. Type (3) is by far the most common in both skarn and vein samples. The dominant daughter mineral in fluid inclusions is rhembic, highly birefringent, and does not dissolve on heating even at 530°C. We assume that this mineral is calcite. The liquid phase in most of the fluid inclusions has low to moderate salinities: 0–15 wt. %; in a few has higher salinities (30–40 wt. % NaCl equivalent). The homogenization temperatures of inclusions in the skarn stage range from 350°C to 530°C, later tungsten mineralization-stage inclusions homogenize between 200°C and 300°C, as do inclusions in veins. Fluid inclusions in granite and greisen resemble those of the late tungsten mineralization stage, with low salinity and homogenization temperatures of 200°–360°C. The tungsten-forming fluids are probably a mixture that came from biotite granite and the surrounding country rocks.  相似文献   

18.
Abstract Standard petrographic, microthermometric and Raman spectroscopic analyses of fluid inclusions from the metamorphosed massive sulphide deposits at Ducktown, Tennessee, indicate that fluids with a wide range of compositions in the C–O–H–N–S–salt system were involved in the syn- to post-metamorphic history of these deposits. Primary fluid inclusions from peak metamorphic clinopyroxene contain low-salinity, H2O–CH4 fluids and calcite, quartz and pyrrhotite daughter crystals. Many of these inclusions exhibit morphologies resembling those produced in laboratory experiments in which confining pressures significantly exceed the internal pressures of the inclusions. Secondary inclusions in metamorphic quartz from veins, pods, and host matrix record a complex uplift history involving a variety of fluids in the C–O–H–N–salt system. Early fluids were generated by local devolatilization reactions while later fluids were derived externally. Isochores calculated for secondary inclusions in addition to the chronology of trapping and morphological features of primary and secondary fluid inclusions suggest an uplift path which was concave toward the temperature axis over the P–T range 6–3 kbar and 550–225° C. Immiscible H2O–CH4–N2–NaCl fluids were trapped under lithostatic to hydrostatic pressure conditions at 3–0.5 kbar and 215 ± 20° C. Entrapment occurred during Alleghanian thrusting, and the fluids may have been derived by tectonically driven expulsion of pore fluids and thermal maturation of organic material in lower-plate sedimentary rocks which are thought to underlie the deposits. Episodic fracturing and concomitant pressure decreases in upper-plate rocks, which host the ore bodies, would have allowed these fluids to move upward and become immiscible. Post-Alleghanian uplift appears to have been temperature-convex. Uplift rates of 0.10–0.05 mm year?1 from middle Ordovician to middle Silurian – late Devonian, and 0.07–0.12 mm year?1 from middle Silurian – late Devonian to late Permian are suggested by our uplift path and available geochronological data.  相似文献   

19.
The Nuri Cu‐W‐Mo deposit is located in the southern subzone of the Cenozoic Gangdese Cu‐Mo metallogenic belt. The intrusive rocks exposed in the Nuri ore district consist of quartz diorite, granodiorite, monzogranite, granite porphyry, quartz diorite porphyrite and granodiorite porphyry, all of which intrude in the Cretaceous strata of the Bima Group. Owing to the intense metasomatism and hydrothermal alteration, carbonate rocks of the Bima Group form stratiform skarn and hornfels. The mineralization at the Nuri deposit is dominated by skarn, quartz vein and porphyry type. Ore minerals are chalcopyrite, pyrite, molybdenite, scheelite, bornite and tetrahedrite, etc. The oxidized orebodies contain malachite and covellite on the surface. The mineralization of the Nuri deposit is divided into skarn stage, retrograde stage, oxide stage, quartz‐polymetallic sulfide stage and quartz‐carbonate stage. Detailed petrographic observation on the fluid inclusions in garnet, scheelite and quartz from the different stages shows that there are four types of primary fluid inclusions: two‐phase aqueous inclusions, daughter mineral‐bearing multiphase inclusions, CO2‐rich inclusions and single‐phase inclusions. The homogenization temperature of the fluid inclusions are 280°C–386°C (skarn stage), 200°C–340°C (oxide stage), 140°C–375°C (quartz‐polymetallic sulfide stage) and 160°C–280°C (quartz‐carbonate stage), showing a temperature decreasing trend from the skarn stage to the quartz‐carbonate stage. The salinity of the corresponding stages are 2.9%–49.7 wt% (NaCl) equiv., 2.1%–7.2 wt% (NaCl) equiv., 2.6%–55.8 wt% (NaCl) equiv. and 1.2%–15.3 wt% (NaCl) equiv., respectively. The analyses of CO2‐rich inclusions suggest that the ore‐forming pressures are 22.1 M Pa–50.4 M Pa, corresponding to the depth of 0.9 km–2.2 km. The Laser Raman spectrum of the inclusions shows the fluid compositions are dominated in H2O, with some CO2 and very little CH4, N2, etc. δD values of garnet are between ?114.4‰ and ?108.7‰ and δ18OH2O between 5.9‰ and 6.7‰; δD of scheelite range from ?103.2‰ to ?101.29‰ and δ18OH2O values between 2.17‰ and 4.09‰; δD of quartz between ?110.2‰ and ?92.5‰ and δ18OH2O between ?3.5‰ and 4.3‰. The results indicate that the fluid came from a deep magmatic hydrothermal system, and the proportion of meteoric water increased during the migration of original fluid. The δ34S values of sulfides, concentrated in a rage between ?0.32‰ to 2.5‰, show that the sulfur has a homogeneous source with characteristics of magmatic sulfur. The characters of fluid inclusions, combined with hydrogen‐oxygen and sulfur isotopes data, show that the ore‐forming fluids of the Nuri deposit formed by a relatively high temperature, high salinity fluid originated from magma, which mixed with low temperature, low salinity meteoric water during the evolution. The fluid flow through wall carbonate rocks resulted in the formation of layered skarn and generated CO2 or other gases. During the reaction, the ore‐forming fluid boiled and produced fractures when the pressure exceeded the overburden pressure. Themeteoric water mixed with the ore‐forming fluid along the fractures. The boiling changed the pressure and temperature, oxygen fugacity, physical and chemical conditions of the whole mineralization system. The escape of CO2 from the fluid by boiling resulted in scheelite precipitation. The fluid mixing and boiling reduced the solubility of metal sulfides and led the precipitation of chalcopyrite, molybdenite, pyrite and other sulfide.  相似文献   

20.
Gold deposits in the Taihang Mountains, northern China, mainly consist of quartz sulfide veins in granitoid plutons. This paper describes the geological setting of the gold deposits, and presents the results of microthermometric, Fourier transform infrared spectra, and stable isotope analyses of ore—forming fluids for the purpose of examining the characteristics of these fluids. The ore—forming fluid was of high temperature (up to 380°C) and high salinity (33–41 wt% NaCl equiv.), represented by type I inclusions (with daughter minerals). This fluid evolved to low salinity at low temperatures recorded in type II (liquid-rich) and III inclusions (vapor—rich). Primary type II inclusions coexist with type III inclusions in quartz. Type III inclusions have almost the same homogenization temperatures as type II inclusions. This probably reflects boiling. The secondary fluid inclusions homogenized at lower temperatures, and have lower salinities than primary inclusions. Based on microthermometric data, we propose that the high—temperature fluid that separated from residual magma corresponded to the ore—forming fluid represented by type I inclusions. This fluid mixed with meteoric water in the upper part of the granitic pluton and was diluted. The diluted fluid boiled, probably due to abrupt pressure decrease, and formed liquid—rich type II inclusions and vapor—rich type III inclusions. The deposition of sulfide minerals and gold probably occurred during boiling.  相似文献   

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