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1.
The Dongshengmiao Pb-Zn deposit located in the Mesoproterozoic aulacogen in a passive continental margin in the north- west margin of the North-China Craton is widely considered to be a untypical SEDEX deposit.Recently,new types of mineralization such as chalcopyrite veins and re-crystallized sphalerite ores with visible hydrothermal alteration have been found in the deposit at depth.In this paper we report the decrepitation temperatures of fluid inclusions in chalcopyrite,sphalerite and quartz from these new types of ores.The decrepitation temperatures of fluid inclusions in chalcopyrite(4 samples),sphalerite(2 samples)and quartz(5 samples)are 303～456℃,97～497℃,146～350℃and 350～556℃,respectively.The decrepitation temperatures of fluid inclusions in the vein-type chalcopyrite are similar to the decrepitation temperatures of fluid inclusions in chalcopyrite from the Hercynian Oubulage porphyry Cu-Au deposit(313～514℃)and the Chehugou porphyry Cu-Mo deposit(277～485℃),supporting our interpretation that the Dongshengmiao deposit was overprinted by magmatic hydrothermal mineralization.The decrepitation temperatures of fluid inclusions in re-crystallized sphalerite from the Dongshengmiao deposit are characterized by two peaks,97～358℃and 358～497℃.The decrepitation temperatures of fluid inclusions in quartz in ehalcopyrite veins from the Dongshengmiao deposit are also characterized by two peaks,146～350℃and 350～556℃.The lower and higher temperature peaks in both cases are considered to represent two separate mineralization events,original SEDEX mineralization and magmatic hydrothermal overprinting,respectively.The higher decrepitation temperatures of fluid inclusions in quartz and sphalerite from the Dongshengmiao deposit are similar to the decrepitation temperatures(340～526℃)of fluid inclusions in sphalerite from the Baiyinnuoer skarn-type Pb-Zn deposit in the region. Replacement of pyrite by sphalerite and overgrowth of chalcopyrite on pyrite in the Dongshengmiao support our interpretation that the original SEDEX mineralization was overprinted by magmatic hydrothermal activity in the deposit.Our results suggest that there may be separate porphyry and skarn-type deposits related to Hercynian magmatism and associated hydrothermal activities in the Langshan area, which are potential exploration targets in the future.  相似文献   

2.
The Hetai ductile shear zone-hosted gold deposit occurs in the deep-seated fault mylonite zone of the Sinian-Silurian metamorphic rock series. In this study there have been discovered melt inclusions, fluid-melt inclusions and organic inclusions in ore-bearing quartz veins of the ore deposit and mylonite for the first time. The homogenization temperatures of the various types of inclusions are 160℃, 180 - 350℃, 530℃ and 870℃ for organic inclusions, liquid inclusions, two-phase immiscible liquid inclusions and melt inclusions, respectively. Ore fluid is categorized as the neutral to basic K+ -Ca2+ -Mg2+ -Na+ - SO2- 4-HCO3-Cl- system. The contents of trace gases follow a descending order of H2O＞CO2＞CH4＞(or ＜ ) H2＞CO＞C2H2＞C2I-I6＞O2＞N2.The concentrations of K , Ca2 + ,SO2-4,HCO3-,Cl- H2O and C2H2 in fluid inclusions are related to the contents of gold and the Au/Ag ratios in ores from different levels of the gold deposit. This is significant for deep ore prospecting in the region. Daughter minerals in melt inclusions were analyzed using SEM. Quartz, orthoclase, wollastonite and other silicate minerals were identified. They were formed in different mineral assemblages.This analysis further proves the existence of melt inclusions in ore veins. Sedimentary metamorphic rocks could form silicate melts during metamorphic anatexis and dynamic metamorphism, which possess melt-solution characteristics. Ore formation is related to the multi-stage forming process of silicate melt and fluid.  相似文献   

3.
Gold-bearing quartz veins of the Taihua Group consisting of Archean metavolcanic rocks are a main gold deposit type in the Xiao Qinling area,one of the three biggest gold production areas in China.The quartz veins experienced strong alteration characterized by a typical mesothermal hydrothermal altered mineral assemblage.The grade of gold is affected by the contents of sulphides,e.g.galena,pyrite and chalcopyrite.Results of minor elements analysis for the of gold-bearing quartz veins indicate higher contents of Au and high contents of Ag,Pb,Cu,Cd,W,and Mo.Abundant fluid inclusions were found in the gold-bearing quartz veins.Three types of fluid inclusions were identified:(1) aqueous inclusions;(2) CO 2-bearing inclusions;and(3) daughter crystal-bearing fluid inclusions.Homogenization temperatures ranged from 110 to 670℃ with low and high peaks appearing at 160 180℃ and 280 300℃,respectively.The salinity of aqueous inclusions varies between 1.8 wt% and 38.2 wt% NaCl.The homogenization temperature and salinity show a positive correlation.The H and O isotopes of fluid inclusions in the gold-bearing quartz veins indicate that magmatic solution and metamorphic hydrothermal solution,together with meteoric water,were involved in the formation of gold-bearing fluid.Mesozoic magma activities related to granite intrusions should be the main source of CO 2 fluid with higher temperature and salinity.  相似文献   

4.
某含钽铌花岗岩成岩成矿温度的研究   总被引：1，自引：0，他引：1  
Formation temperatures are obtained for a tantalum-niobium-bearing granite(512-530℃）,the feldspar-quartz zone(495℃）,the quartz zone(483℃）in the pegmatoid and wolframite-quartz vein(262-273℃,no pressure corection has been made through studies of fluid inclusions in quartz,wolframite,Mn-rich columbite microlite and other minerals,The results demonstrate that petrogenesis and metallogenesis of this district are a protracted,multistage process.  相似文献   

5.
Abundant fluid-melt inclusions are found in the aegirine-augite-barite pegmatite and carbonatite veins in the Mianning REE deposit,Sichuan,They were trapped in early stage fluorite and quartz from a salt-melt system at temperatures higher than 5000℃,Meanwhile,fluid inclusions are also present in alrge amounts in bastnaesite.Homogenized between 150 and 270℃,these inclusions are thought to be representative of the physico-chemical conditions of REE mineralization.These results show that the Mianning REE deposit is of typical hydrothermal origin developed from a salt-melt system.  相似文献   

6.
《地学前缘(英文版)》2020,11(4):1145-1161
The Budunhua Cu deposit is located in the Tuquan ore-concentrated area of the southern Great Xing'an Range,NE China.This deposit includes the southern Jinjiling and northern Kongqueshan ore blocks,separated by the Budunhua granitic pluton.Cu mineralization occurs mainly as stockworks or veins in the outer contact zone between tonalite porphyry and Permian metasandstone.The ore-forming process can be divided into four stages involving stage Ⅰ quartz-pyrite-arsenopyrite;stage Ⅱ quartz-pyrite-chalcopyrite-pyrrhotite;stage Ⅲ quartz--polynetallic sulfides;and stage IV quartz-calcite.Three types of fluid inclusions(FIs) can be distinguished in the Budunhua deposit:liquid-rich two-phase aqueous FIs(L-type),vapour-rich aqueous FIs(V-type),and daughter mineral-bearing multi-phase FIs(S-type).Quartz of stages Ⅰ-Ⅲ contains all types of FIs,whereas only L-type FIs are evident in stage Ⅳ veins.The coexisting V-and S-type FIs of stages Ⅰ-Ⅲ have similar homogenization temperatures but contrasting salinities,which indicates that fluid boiling occurred.The FIs of stages Ⅰ,Ⅱ,Ⅲ,and Ⅳyield homogenization temperatures of 265-396℃,245-350℃,200-300℃,and 90-228℃ with salinities of3.4-44.3 wt.%,2.9-40.2 wt.%,1.4-38.2 wt.%,and 0.9-9.2 wt.% NaCl eqv.,respectively.Ore-forming fluids of the Budunhua deposit are characterized by high temperatures,moderate salinities,and relatively oxidizing conditions typical of an H_2 O-NaCl fluid system.Mineralization in the Budunhua deposit occurred at a depth of0.3-1.5 km,with fluid boiling and mixing likely being responsible for ore precipitation.C-H-O-S-Pb isotope studies indicate a predominantly magmatic origin for the ore-forming fluids and materials.LA-ICP-MS zircon U-Pb analyses indicate that ore-forming tonalite porphyry and post-ore dioritic porphyrite were formed at 151.1±1.1 Ma and 129.9±1.9 Ma,respectively.Geochemical data imply that the primary magma of the tonalite porphyry formed through partial melting of Neoproterozoic lower crust.On the basis of available evidence,we suggest that the Budunhua deposit is a porphyry ore system that is spatially,temporally,and genetically associated with tonalite porphyry and formed in a post-collision extensional setting following closure of the Mongol-Okhotsk Ocean.  相似文献   

7.
The Tongcun Mo(Cu) deposit in Kaihua city of Zhejiang Province,eastern China,occurs in and adjacent to the Songjiazhuang granodiorite porphyry and is a medium-sized and important porphyry type ore deposit.Two irregular Mo(Cu) orebodies consist of various types of hydrothermal veinlets.Intensive hydrothermal alteration contains skarnization,chloritization,carbonatization,silicification and sericitization.Based on mineral assemblages and crosscutting relationships,the oreforming processes are divided into five stages,i.e.,the early stage of garnet + epidote ± chlorite associated with skarnization and K-feldspar + quartz ± molybdenite veins associated with potassicsilicic alteration,the quartz-sulfides stage of quartz + molybdenite ± chalcopyrite ± pyrite veins,the carbonatization stage of calcite veinlets or stockworks,the sericite + chalcopyrite ± pyrite stage,and the late calcite + quartz stage.Only the quartz-bearing samples in the early stage and in the quartzsulfides stage are suitable for fluid inclusions(FIs) study.Four types of FIs were observed,including1) CO_2-CH_4 single phase FIs,2) CO_2-bearing two- or three-phase FIs,3) Aqueous two-phase FIs,and4) Aqueous single phase FIs.FIs of the early stages are predominantly CO_2- and CH_4-rich FIs of the CO_2-CH4-H_2O-NaCl system,whereas minerals in the quartz-sulfides stage contain CO_2-rich FIs of the CO_2-H_2O-NaCl system and liquid-rich FIs of the H_2O-NaCl system.For the CO_2-CH_4 single phase FIs of the early mineralization stage,the homogenization temperatures of the CO_2 phase range from 15.4 ℃ to 25.3 ℃(to liquid),and the fluid density varies from 0.7 g/cm~3 to 0.8 g/cm~3;for two- or three-phase FIs of the CO_2-CH_4-H_2O-NaCl system,the homogenization temperatures,salinities and densities range from 312℃ to 412℃,7.7 wt%NaCl eqv.to 10.9 wt%NaCl eqv.,and 0.9 g/cm~3 to 1.0 g/cm~3,respectively.For CO_2-H_2O-NaCI two- or threephase FIs of the quartz-sulfides stage,the homogenization temperatures and salinities range from255℃ to 418℃,4.8 wt%NaCl eqv.to 12.4 wt%NaCl eqv.,respectively;for H_2O-NaCl two-phase FIs,the homogenization temperatures range from 230 ℃ to 368 ℃,salinities from 11.7 wt%NaCl eqv.to16.9 wt%NaCl eqv.,and densities from 0.7 g/cm~3 to 1.0 g/cm~3.Microthermometric measurements and Laser Raman spectroscopy analyses indicate that CO_2 and CH_4 contents and reducibility(indicated by the presence of CH_4) of the fluid inclusions trapped in quartz-sulfides stage minerals are lower than those in the early stage.Twelve molybdenite separates yield a Re-Os isochron age of 163 ± 2.4 Ma,which is consistent with the emplacement age of the Tongcun,Songjiazhuang,Dayutang and Huangbaikeng granodiorite porphyries.The S18OSMow values of fluids calculated from quartz of the quartz-sulfides stage range from 5.6‰ to 8.6‰,and the JDSMOw values of fluid inclusions in quartz of this stage range from-71.8‰ to-88.9‰,indicating a primary magmatic fluid source.534SV-cdt values of sulfides range from+1.6‰ to +3.8‰,which indicate that the sulfur in the ores was sourced from magmatic origins.Phase separation is inferred to have occurred from the early stage to the quartz-sulfides stage and resulted in ore mineral precipitation.The characteristics of alteration and mineralization,fluid inclusion,sulfur and hydrogen-oxygen isotope data,and molybdenite Re-Os ages all suggest that the Tongcun Mo(Cu) deposit is likely to be a reduced porphyry Mo(Cu) deposit associated with the granodiorite porphyry in the Tongcun area.  相似文献   

8.
The Chalukou porphyry Mo deposit, located in the Great Hinggan Range, is the largest Mo deposit in northeast China, although the age and genesis of the associated magmatic intrusions remain debated.Here we report zircon U-Pb ages and trace elements, whole rock geochemistry and Sre Nd isotope data with a view to understand the relationship between the magmatism and molybdenum mineralization.Zircon U-Pb analysis yield an age of 475 Ma for rhyolite in the older strata, 168 Ma for the premineralization monzogranite, and 154 Ma for the syn-mineralization granite porphyry. The granite porphyry and quartz porphyry are considered as the ore-forming intrusions. These rocks are peraluminous, alkali-calcic, and belong to high-K to shoshonitic series with a strong depletion of Eu. They also display characteristics of I-type granites. The rocks exhibit wide variations of(87 Sr/86 Sr)iin the range of 0.705426 -0.707363, and ε_(Nd)(t) of -3.7 to 0.93. Zircon REE distribution patterns show characteristics between crust and the mantle, implying magma genesis through crust-mantle interaction. The Fe_2O_3/FeO values(average 1) for the whole rock and EuN/Eu*Nvalues(average 0.45), Ce~(4+)/Ce~(3+) values(average 301)for zircon grains from the granite porphyry are higher than those from other lithologies. These features suggest that the ore-forming intrusions(syn-mineralization porphyry) had higher oxygen fugacity conditions than those of the pre-mineralization and post-mineralization rocks. The Chalukou Mo deposit formed in relation to the southward subduction of the Mongol-Okhotsk Ocean. Our study suggests that the subduction-related setting, crust-mantle interaction, and the large-scale magmatic intrusion were favorable factors to generate the super-large Mo deposits in this area.  相似文献   

9.
According to the metallogenic theory by transmagmatic fluid(TMF).one magmalic intrusion is a channel of ore-bearing fluids,but not their source.Therefore,it is possible to use TMF’s ability for injection into and for escaping from the magmatic intrusion to evaluate its ore-forming potential.As the ore-bearing fluids cannot effectively inject into the magmatic intrusion when the magma fully crystallized, the cooling time and rates viscosity varied can be used to estimate the minimum critical thickness of the intrusion.One dimensional heat transfer model is used to determine the cooling time for three representative dikes of different composition(granite porphyry,quartz diorite and diabase) in the Shihu gold deposit.It also estimated the rates viscosity varied in these lime interval.We took the thickness of dike at the intersection of the cooling time—thickness curve and the rates viscosity varied versus thickness curve as the minimum critical thickness.For the ore-bearing fluids effectively injecting into the magma,the minimum critical thicknesses for the three representative dikes are 33.45 m for granite porphyry,8.22 m for quartz diorite and 1.02 m for diabase,indicating that ore-bearing dikes must be thicker than each value.These results are consistent with the occurrence of ore bodies,and thus they could be applied in practice.Based on the statistical relationship between the length and the width of dikes.these critical thicknesses are used to compute critical areas:0.0003—0.0016 km~2 for diabase. 0.014—0.068 km~2 for quartz diorite and 0.011—0.034 km~2 for granite porphyry.This implies that orebearing minor intrusions have varied areas corresponding to their composition.The numerical simulation has provided the theoretical threshold of exposed thickness and area of the ore-bearing intrusion.These values can be used to determine the ore-forming potentials of dikes.  相似文献   

10.
The Tashan porphyry tin polymetallic deposit is located at the southwest part of the Lianhuashan Fault in the eastern Guangdong province. It is one of the three typical porphyry tin deposits in China. In this paper, we reported cassiterite and zircon U-Pb ages, geochemistry and Lu-Hf isotopes of the ore-bearing granite porphyry in the orefield. Zircon LA-ICP-MS U-Pb dating yielded a concordant ages of 136.8±1.1 Ma, whereas analyses of cassiterite yielded a 206Pb/238U-207Pb/238U concordia lower intercept age of 133.6±8.6 Ma and a Tera-Wasserburg lower intercept age of 136.5±8.1 Ma, which suggest a genetic link between the granite porphyry and the ore mineralization. The εHf(t) values of -4.87 to -2.07 and tDM2 ages 1322 Ma to 1507 Ma for zircon from the granite porphyry show that the Tashan granite porphyry was likely derived from partial melting of the Mesoproterozoic crustal rocks with minor input of mantle material. © 2018, Science Press. All right reserved.  相似文献   

11.
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   

12.
Melt and fluid inclusions were investigated in six quartz phenocryst samples from the igneous rocks of the extrusive (ignimbrites and rhyolites) and subvolcanic (granite porphyries) facies of the Lashkerek Depression in the Kurama mining district, Middle Tien Shan. The method of inclusion homogenization was used, and glasses from more than 40 inclusions were analyzed on electron and ion microprobes. The chemical characteristics of these inclusions are typical of silicic magmatic melts. The average composition is the following (wt %): 72.4 SiO2, 0.06 TiO2, 13.3 Al2O3, 0.95 FeO, 0.03 MnO, 0.01 MgO, 0.46 CaO, 3.33 Na2O, 5.16K2O, 0.32 F, and 0.21 Cl. Potassium strongly prevails over sodium in all of the inclusions (K2O/Na2O averages 1.60). The average total of components in melt inclusions from five samples is 95.3 wt %, which indicates a possible average water content in the melt of no less than 3–4 wt %. Water contents of 2.0 wt % and 6.6 wt % were determined in melt inclusions from two samples using an ion microprobe. The analyses of ore elements in the melt inclusions revealed high contents of Sn (up to 970 ppm), Th (19–62 ppm, 47 ppm on average), and U (9–26 ppm, 18 ppm on average), but very low Eu contents (0.01 ppm). Melt inclusions of two different compositions were detected in quartz from a granite porphyry sample: silicate and chloride, the latter being more abundant. In addition to Na and K chlorides, the salt inclusions usually contain one or several anisotropic crystals and an opaque phase. The homogenization temperatures of the salt inclusions are rather high, from 680 to 820°C. In addition to silicate inclusions with homogenization temperatures of 820–850°C, a primary fluid inclusion of aqueous solution with a concentration of 3.7 wt % NaCl eq. and a very high density of 0.93 g/cm3 was found in quartz from the ignimbrite. High fluid pressure values of 6.5–8.3 kbar were calculated for the temperature of quartz formation. These estimates are comparable with values obtained by us previously for other regions of the world: 2.6–4.3 kbar for Italy, 3.7 kbar for Mongolia, 3.3–8.7 kbar for central Slovakia, and 3.3–9.6 kbar for eastern Slovakia. Unusual melt inclusions were investigated in quartz from another ignimbrite sample. In addition to a gas phase and transparent glass, they contain spherical Feoxide globules (81.2 wt % FeO) with high content of SiO2 (9.9 wt %). The globules were dissolved in the silicate melt within a narrow temperature range of 1050–1100°C, and the complete homogenization of the inclusions was observed at temperatures of 1140°C or higher. The combined analysis of the results of the investigation of these inclusions allowed us to conclude that immiscible liquids were formed in the high-temperature silicic magma with the separation of iron oxide-dominated droplets.  相似文献   

13.
Hydrothermal alteration and mineralization at the Wunugetu porphyry Cu–Mo deposit, China, include four stages, i.e., the early stage characterized by quartz, K-feldspar and minor mineralization, followed by a molybdenum mineralization stage associated with potassic alteration, copper mineralization associated with sericitization, and the last Pb–Zn mineralization stage associated with carbonation. Hydrothermal quartz contains three types of fluid inclusions, namely aqueous (W-type), daughter mineral-bearing (S-type) and CO2-rich (C-type) inclusion, with the latter two types absent in the late stage. Fluid inclusions in the early stage display homogenization temperatures above 510°C, with salinities up to 75.8 wt.% NaCl equivalent. The presence of S-type inclusions containing anhydrite and hematite daughter minerals and C-type inclusions indicates an oxidizing, CO2-bearing environment. Fluid inclusions in the Mo- and Cu-mineralization stages yield homogenization temperatures of 342–508°C and 241–336°C, and salinities of 8.6–49.4 and 6.3–35.7 wt.% NaCl equivalent, respectively. The presence of chalcopyrite instead of hematite and anhydrite daughter minerals in S-type inclusions indicates a decreasing of oxygen fugacity. In the late stage, fluid inclusions yield homogenization temperatures of 115–234°C and salinities lower than 12.4 wt.% NaCl equivalent. It is concluded that the early stage fluids were CO2 bearing, magmatic in origin, and characterized by high temperature, high salinity, and high oxygen fugacity. Phase separation occurred during the Mo- and Cu-mineralization stages, resulting in CO2 release, oxygen fugacity decrease and rapid precipitation of sulfides. The late-stage fluids were meteoric in origin and characterized by low temperature, low salinity, and CO2 poor.  相似文献   

14.
The Xihuashan tungsten deposit, Jiangxi province, China, is a world-class vein-type ore deposit hosted in Cambrian strata and Mesozoic granitic intrusions. There are two major sets of subparallel ore-bearing quartz veins. The ore mineral assemblage includes wolframite and molybdenite, with minor amounts of arsenopyrite, chalcopyrite, and pyrite. There are only two-phase aqueous-rich inclusions in wolframite but at least three major types of inclusions in quartz: two- or three-phase CO2-rich inclusions, two-phase pure CO2 inclusions and two-phase aqueous inclusions, indicating boiling. Fluid inclusions in wolframite have relatively higher homogenization temperatures and salinities (239–380°C, 3.8–13.7 wt.% NaCl equiv) compared with those in quartz (177–329°C, 0.9–8.1 wt.% NaCl equiv). These distinct differences suggest that those conventional microthermometric data from quartz are not adequate to explain the ore formation process. Enthalpy–salinity plot shows a linear relationship, implying mixing of different sources of fluids. Although boiling occurred during vein-type mineralization, it seems negligible for wolframite deposition. Mixing is the dominant mechanism of wolframite precipitation in Xihuashan. δ34S values of the sulfides range from −1.6 to +0.1‰, indicative of a magmatic source of sulfur. δ18O values of wolframite are relatively homogeneous, ranging from +4.8‰ to +6.3‰. Oxygen isotope modeling of boiling and mixing processes also indicates that mixing of two different fluids was an important mechanism in the precipitation of wolframite.  相似文献   

15.
Situated in the Henan-Shaanxi fault-uplift area on the southern margin of the Sino-Korean Paraplatform, the Jinduicheng porphyry molybdenum deposit is the most important molybdenum producer in China. During Yenshanian the Jinduicheng granite porphyry was emplaced in metaspilite of the Proterozoic Xionger Group, controlled by a NW-trending fault. Mineral compositions are mainly quartz (25–40%), microcline and microcline-perthite (27–40%) and plagioclase (An 8–14, 14–32%), associated with minor biotite and muscovite, and phenocrysts are made up of K-feldspar, quartz and plagioclase. Accessory minerals include magmatite, apatite and zircon. The porphyry contains SiO2 73.83% and K2O + Na2O 8.06% (with K2O/Na2O ratio being 1.82), beloning to the calc-alkaline series. Mineralization occurs in the porphyry body and biotitized and hornfelsized spilite within the exocontact zone. The maximum depth of mineralization reaches 1000 meters below the surface. According to mineral assemblage, ore veins are classified into five types: (1) pyrite-quartz; (2) pyrite-K-feldspar-quartz; (3) pyrite-molybdenite-quartz; (4) pyrite-molybdenite-K-feldspar-quartz; and (5) muscovitefluorite-pyrite-molybdenite-quartz. As the most important economic molybdenum mineral, molybdenite occurs in various forms. Wall-rock alterations show a gross zonation of K-feldspathization-greisenization → silicification → propylitization from the porphyry outwards, of which silicification is most intense and has close genetic relationship with Mo mineralization. Fluid inclusion studies yield homogeneous temperatures ranging from 250 to 240°C, with the main stage between 400 and 300°C. Gas inclusions frequently coexist with multiphase inclusions containing such daughter minerals as halite, sylvite, molybdenite and K-feldspar. Under moderate-high temperatures, lowerfo2, highfs2 and weak acidity conditions, boiling of ore-forming fluids is a prerequisite for the precipitation of molybdenite. Sulfur, oxygen and carbon isotopic compositions suggest that at the high temperature stage (450°C) magmatic water is dominant and at the main ore-forming stage a mixture of magmatic water and meteoric water is expected. At the late stage, the mixture is predominated by meteoric water. Sulfur and molybdenum are mostly of magmatic origin.  相似文献   

16.
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   

17.
魏家钨矿床位于湘南西部铜山岭地区,是近年来在南岭成矿带西端新发现的一超大型矽卡岩型钨矿床。矿体主要产于祥林铺花岗岩与其围岩的接触带内,其形成与祥林铺花岗岩密切相关。为厘清其成岩成矿时代,本文对魏家钨矿区的花岗斑岩和石英斑岩进行了锆石LA-MC-ICP-MS U-Pb测年。结果显示,矿区花岗斑岩侵位时间为(157.8±0.9)Ma(MSWD=1.06),石英斑岩侵位时间为(158.3±1.4)Ma(MSWD=0.2)。矿区内花岗斑岩与石英斑岩侵位时间在误差范围内一致,表明两者可能是同一岩浆演化至不同阶段的产物,矿区内花岗质岩浆活动与钨多金属成矿作用时限约为158 Ma,为南岭地区中生代"大规模成矿"作用(160~150 Ma)的组成部分。另外,花岗斑岩中捕获有少量加里东期的岩浆锆石(435 Ma),指示该区曾发生加里东期岩浆活动,这与华南地区广泛存在的加里东期构造岩浆活动事件吻合。魏家钨矿成岩成矿时代的厘定对于在南岭成矿带西端寻找晚侏罗世钨矿具有重要的指示意义。  相似文献   

18.
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   

19.
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   

20.
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   

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