Unveil the Redox Evolution of Ore-forming Fluids using Sulfur Isotope:A Case Study of the Zhengguang Intermediate Sulfidation Epithermal Au-Zn Deposit,NE China

Oxygen fugacity(fO_(2))is a key intensity variable during the entire magmatic-hydrothermal mineralization courses.The redox state and its variations between different stages of the ore-forming fluids of intermediate sulfidation epithermal deposits are rarely deciphered due to the lack of appropriate approaches to determine fO_(2)of the fluids.Here,we reported theδ^(34)S of the sulfides from three different stages(stageⅠ,Ⅱ,Ⅲ)of Zhengguang,an Early Ordovician Au-rich intermediate sulfidation(IS)epithermal deposit,to decipher the redox evolution of the ore-forming fluids.The increasingδ^(34)S values from stageⅠpyrite(pyl,average-2.6‰)through py2(average-1.9‰)to py3(average-0.2‰)indicates a decrease of the oxygen fugacity of the ore-forming fluids.A compilation ofδ^(34)S values of sulfides from two subtypes of IS deposits(Au-rich and Ag-rich)from NE China shows that theδ^(34)S values of sulfides from Au-rich IS deposits are systematically lighter than those of Ag-rich IS Ag-Pb-Zn deposit,indicating the ore-forming fluids of the former are more oxidized than the latter.We highlight that sulfur isotopic composition of hypogene sulfides is an efficacious proxy to fingerprint the oxygen fugacity fluctuations of epithermal deposits and could potentially be used to distinguish the subtypes of IS deposits.

Rb-Sr Dating of Pyrite and Quartz Fluid Inclusions and Origin of Ore-forming Materials of the Jinshan Gold Deposit, Northeast Jiangxi Province, South China

The Jinshan gold deposit is located in the Northeast Jiangxi province,South China,which related to the ductile shear zone.It contains two ore types,i.e.the alteration-type ore and the goldbearing quartz vein ore.Rb-Sr age dating is applied to both gold-bearing pyrite in the alteration-type ore and fluid inclusion in the gold-bearing quartz vein to make clear the time of the gold mineralization of the Jinshan deposit.Analytical results of this study yielded that the age of the alteration-type ore bodies is about 838±110Ma,with an initial 87Sr/86Sr value of 0.7045±0.0020.However,the age of the gold-bearing quartz vein-type ore is about 379±49Ma,and the initial 87Sr/86Sr is 0.7138±0.0011.Based on the age data from this work and many previous studies,the authors consider that the Jinshan gold deposit is a product of multi-staged mineralization,which may include the Jinninian,Caledonian,Hercynian,and Yanshanian Periods.Among them,the Jinninian Period and the Hercynian Period might be the two most important ore-forming periods for Jinshan deposit.The Jinninian Period is the main stage for the formation of alteration-type ore bodies,while the Hercynian Period is the major time for ore bodies of gold-bearing quartz vein type.The initial values of the 87Sr/86Sr from this study,as well as the previous isotope and trace element studies,indicate that the ore-forming materials mainly derived from the metamorphic wall rocks,and the ore-forming fluids mainly originated from the deep metamorphic water.

Characteristics and origin of ore-forming fluids of Jinchangqing gold (copper) ore deposit (s) in Xiangyun, Yunnan Province

On the basis of results of the studies of primary fluid inclusions, and the hydrogen and oxygen isotope data, the authors concluded that the early-stage ore-forming fluid from the Jinchangqing gold (copper) ore deposit is a kind of sulfate type hot brine characterized by medium temperature and salinity, genetically related to the late-stage ore-forming fluid derived from an acidic and more reductive environment. However, the late-stage ore-forming fluid is a sort of low temperature and low salinity chloride-type hot brine which originated from a lower pressure, acidic and more oxidative environment. In general, the ore fluids were derived from the late-stage, or largely from the early-stage groundwater-derived meteoric water, which has a 12‰-17‰ heavier oxygen isotopic composition than the original rain water (δ{}+{18}O={-15.3‰}), and were formed during gold mineralization as a product of oxygen isotope exchange during the reaction between ore-forming fluid and wall rocks under a lower water/rock ratio condition.

Trace element and sulfur isotope compositions of pyrite from the Tianqiao Zn–Pb–Ag deposit in Guizhou province,SW China:implication for the origin of ore-forming fluids

The Tianqiao Zn–Pb–Ag deposit in SW China,hosted by Devonian and Carboniferous limestone and clay rocks,is composed of sulfides such as sphalerite,galena,and pyrite.Pyrite is present in different paragenetic stages and can be divided into four types based on textures and mineral assemblages.Pyrite from the adjacent Shanshulin deposit(Py-SSL)is also used for comparison.Py1 shows framboid texture with grain diameter up to 1 mm and was commonly replaced by sphalerite.Py2 is characterized by overgrowth texture and displays inner oscillatory zoning.Py2 is associated with abundant sphalerite and galena.Py3 shows replacement relics textures where galena fills the fractures of pyrite.Py4 is a euhedral to subhedral crystal disseminated in dolomite and is characterized by deformation and fragmentation textures.Minor sphalerite and galena are associated with Py4.Py-SSL is subhedral and disseminated in dolomite,similar to Py4.Py1 was formed by a diagenetic or sedimentary process,whereas Py2 and Py3 were formed by multiple stages of ore fluids.Py4 and Py-SSL were formed at the carbonate-sulfide stage,but Py4 suffered from deformation after its formation.Py1,Py2,and Py3 are characterized by relative enrichment of Sb,Cu,and As,in contrast to Py4 and Py-SSL with higher Cr,W,Ge,Sn,Tl,Ni,and Ga contents.However,critical metals such as Ge,Ga,and In in pyrite are generally lower than10 ppm,which are not economically important.The trace element variation in Tianqiao pyrite with paragenesis results from fluid evolution in the Pb–Zn ore system and competition with co-precipitating minerals.Diagenetic and ore-forming hydrothermal fluids are responsible for the formation of different types of pyrite.Ore-related pyrite from the Tianqiao and Shanshulin deposits has Co and Ni distribution features similar to pyrite from sedimentary pyrite and submarine hydrothermal vents,different from those in volcanogenic massive sulfide,iron oxide-copper–gold,and porphyry Cu deposits,indicating their derivation of relatively low-temperature(<~250°C)hydrothermal fluids,similar to basin brines or seawater.,via fluid-rock interaction.This conclusion is also supported by the sulfur isotope composition of sulfides which are 13.0–13.5%,and 15.6–20.5%for Tianqiao and Shanshulin deposits,respectively.

In, Sn, Pb and Zn Contents and Their Relationships in Ore-forming Fluids from Some In-rich and In-poor Deposits in China

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 Inpoor 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 7×10^-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 oreforming 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.

Numerical Modelling of Ore-forming Dynamics of Fractal Dispersive Fluid Systems

Based on an analysis of the fractal structures and mass transport mechanism of typical shear-fluid-ore formation system, the fractal dispersion theory of the fluid system was used in the dynamic study of the ore formation system. The model of point-source diffusive illuviation of the shear-fluid-ore formation system was constructed, and the numerical simulation of dynamics of the ore formation system was finished. The result shows that: (1) The metallogenic system have nested fractal structure. Different fractal dimension values in different systems show unbalance and inhomogeneity of ore-forming processes in the geohistory. It is an important parameter to symbolize the process of remobilization and accumulation of ore-forming materials. Also it can indicate the dynamics of the metallogenic system quantitatively to some extent. (2) In essence, the fractal dispersive ore-forming dynamics is a combination of multi-processes dominated by fluid dynamics and supplemented by molecule dispersion in fluids and fluid-rock interaction. It changes components and physico-chemical properties of primary rocks and fluids, favouring deposition and mineralization of ore-forming materials. (3) Gold ore-forming processes in different types of shear zones are quite different. (1) In a metallogenic system with inhomogeneous volumetric change and inhomogeneous shear, mineralization occurs in structural barriers in the centre of a shear zone and in geochemical barriers in the shear zone near its boundaries. But there is little possibility of mineralization out of the shear zone. (2) As to a metallogenic system with inhomogeneous volumetric change and simple shear, mineralization may occur only in structural barriers near the centre of the shear zone. (3) In a metallogenic system with homogeneous volumetric change and inhomogeneous shear, mineralization may occur in geochemical barriers both within and out of the shear zone.

Geochemical Characteristics and Sources of Ore-forming Fluids of the Mayuan Pb-Zn Deposit,Nanzheng,Shaanxi,China

The Mayuan stratabound Pb-Zn deposit in Nanzheng,Shaanxi Province,is located in the northern margin of the Yangtze Plate,in the southern margin of the Beiba Arch.The orebodies are stratiform and hosted in breciated dolostone of the Sinian Dengying Formation.The ore minerals are primarily sphalerite and galena,and the gangue minerals comprise of dolomite,quartz,barite,calcite and solid bitumen.Fluid inclusions from ore-stage quartz and calcite have homogenization tempreatures from 98 to 337℃ and salinities from 7.7 wt%to 22.2 wt%（NaCl equiv.）.The vapor phase of the inclusions is mainly composed of CH_4 with minor CO_2 and H_2S.The δD_（fluid） values of fluid inclusions in quartz and calcite display a range from-68‰ to-113‰（SMOW）,and the δ^（18）O_（fluid）values calculated from δ^（18）O_（quartz） and δ^（18）O_（calcite） values range from 4.5‰ to 16.7‰（SMOW）.These data suggest that the ore-forming fluids may have been derived from evaporitic sea water that had reacted with organic matter.The δ^（13）C_（CH4） values of CH_4 in fluid inclusions range from-37.2‰ to-21.0‰（PDB）,suggesting that the CH_4 in the ore-forming fluids was mainly derived from organic matter.This,together with the abundance of solid bitumen in the ores,suggest that organic matter played an important role in mineralization,and that the thermochemical sulfate reduction（TSR） was the main mechanism of sulfide precipitation.The Mayuan Pb-Zn deposit is a carbonate-hosted epigenetic deposit that may be classified as a Mississippi Valley type（MVT） deposit.

Characteristics of Pegmatite-Related Fluids and Significance to Ore-Forming Processes in the Zhaxikang Pb-Zn-Sb Polymetallic Deposit,Tibet,China

The Zhaxikang Pb-Zn-Sb polymetallic deposit is one of the most important deposits in the newly recognized southern Tibet antimony-gold metallogenic belt.Compared to the porphyry deposits in the Gangdese belt,much less researches have addressed these deposits,and the genesis of the Zhaxikang deposit is still controversial.Based on field investigation,petrographic,microthermometric,Laser Raman Microprobe（LRM） and SEM/EDS analyses of fluid,melt-fluid,melt and solid inclusions in quartz and beryl from pegmatite,this paper documents the characteristics and the evolution of primary magmatic fluid which was genetically related to greisenization,pegmatitization,and silification in the area.The results show that the primary magmatic fluids were derived from unmixing between melt and fluid and underwent a phase separation process soon after the exsolution.The primary magmatic fluids are of low salinity,high temperature,and can be approximated by the H_2O-NaCl-CO_2 system.The presence of Mn-Fe carbonate in melt-fluid inclusions and a Zn-bearing mineral（gahnite） trapped in beryl and in inclusions from pegmatite indicates high Mn,Fe,and Zn concentrations in the parent magma and magmatic fluids,and implies a genetic link between pegmatite and Pb-Zn-Sb mineralization.High B and F concentrations in the parent magma largely lower the solidus of the magma and lead to late fluid exsolution,thus the primary magmatic fluids related to pegmatite have much lower temperature than those in most porphyry systems.Boiling of the primary magmatic fluids leads to high-salinity and high-temperature fluids which have high capacity to transport Pb,Zn and Sb.The decrease in temperature and mixing with fluids from other sources may have caused the precipitation of Pb-Zn-Sn（Au） minerals in the distal fault systems surrounding the causative intrusion.

REE Geochemistry of Fluorite from the Maoniuping REE Deposit,Sichuan Province,China:Implications for the Source of Ore-forming Fluids

Fluorite is one of the main gangue minerals in the Maoniuping REE deposit, Sichuan Province, China. Fluorite with different colors occurs not only within various orebodies, but also in wallrocks of the orefield. Based on REE geochemistry, fluorite in the orefleld can be classified as the LREE-rich, LREE-flat and LREE-depleted types. The three types of fluorite formed at different stages from the same hydrothermal fluid source, with the LREE-rich fluorite forming at the relatively early stage, the LREE-flat fluorite in the middle, and the LREE-depleted fluorite at the latest stage. Various lines of evidence demonstrate that the variation of the REE contents of fluorite shows no relation to the color. The mineralization of the Maouiuping REE deposit is associated spatially and temporally with carbonatite-syenite magmatism and the ore-forming fluids are mainly derived from carbonatite and syenite melts.

Ore-forming Fluid Systems and Mineralization in the Eastern Jiangnan Uplift in the Border Area of Anhui and Jiangxi Provinces, China

Obvious differences in mineralization characteristics exist between the southern and northern parts of the eastern part of the Jiangnan Uplift in northern Jiangxi Province and southern Anhui Province. The regional metallogeny is discussed, and the ore-forming fluid systems are classified in this article. It is proposed that the fluid ore-forming activities in the Jiangnan Uplift both in northern Jiangxi and southern Anhui have close relationships with the crust-mantle interaction and magmatic-tectonic activities. The types and scales of the mineralization on the both sides of the eastern Jiangnan Uplift were determined by fluid ore-forming systems and geological backgrounds.

Fluid Evolution and Ore-forming Processes of the Jiama Cu Deposit, Tibet： Evidence from Fluid Inclusions

The Jiama deposit is a large copper deposit in Tibet. Mineralization occurs in three different host rocks： skarn, hornfels and porphyry. A detailed fluid inclusion study was conducted for veins in the different host rocks to investigate the relationship between fluid evolution and ore-forming processes. Based on examination of cores from 36 drill holes, three types of veins （A, B and D） were identified in the porphyries, four types （I, II, III and IV） in the skarn, and three （a, b and c） in the hornfels. The crosscutting relationships of the veins and that of the host rocks suggest two hydrothermal stages, one early and one late stage. Fluid inclusions indicate that the Jiama hydrothermal fluid system underwent at least two episodes of fluid boiling. The first boiling event occurred during the early hydrothermal stage, as recorded by fluid inclusions hosted in type A veins in the porphyries, type a veins in the hornfels, and wollastonite in the skarns. This fluid boiling event was associated with relatively weak mineralization. The second boiling event occurred in the late hydrothermal stage, as determined from fluid inclusions hosted in type B and D veins in the porphyries, type I to IV veins in the skarns, and type b and c veins in the hornfels. This late boiling event, together with mixing with meteoric water, was responsible for more than 90% of the metal accumulation in the deposit. The first boiling only occurred in the central part of the deposit and the second boiling event took place across an entire interlayered structural zone between hornfels and marble. A spatial zoning of ore-elements is evident, and appears to be related to different migration pathways and precipitation temperatures of Cu, Mo, Pb, Zn, Au and Ag.

Ore-forming Fluid Characteristics of the Saishitang Cu-polymetallic Deposit in Qinghai Province,China

Saishitang Cu-polymetallic deposit is located in the southeast section of Late Paleozoic arcfoid in the southeastern margin of Qaidam platform. Accoring to the geological process of the deposit, four mineralization episodes were identified： melt/fluid coexisting period （O）, skarn period （A）, first sulfide period （B） and second sulfide period （C）, and 10 stages were finally subdivided. Three types of inclusions were classified in seven stages, namely crystal bearing inclusions （type I）, aqueous inclusions （type Ⅱ） and pure liquid inclusions （type Ⅲ）. Type I and Ⅱ inclusions were observed in stage O1, having homogenization temperature from 252 to 431℃, and salinities ranging from 24.3% to 48.0%. Type I inclusion was present in stage A1, having homogenization temperature from 506 to 548℃, and salinities ranging from 39.4% to 44.6%. In stage B1, type Ⅱ and Ⅲ inclusions were observed, with homogenization temperature concentrating between 300-400℃, and salinities from 0.4% to 4.3%. Type II inclusions were present in stage B2, with homogenization temperature varying from 403 to 550℃. In stage C1, type I and II inclusion commonly coexisted, and constituted a boiling inclusion group, having homogenization temperatures at 187-463℃, and salinities in a range of 29.4%-46.8% and 2.2%-11.0%. Type II and III inclusions were developed in stage C2, having homogenization temperature at 124-350℃, and salinities ranging between 1.6% and 15.4%. In stage C3, type Ⅱ and Ⅲ inclusions were presented, with a homogenization temperature range of 164-360℃, and salinities varying from 4.0% to 11.0%. The results of micro-thermal analysis show that fluids are characterized by high temperature and high salinity in stage O1 and A1, and experienced slight decrease in temperature and dramatic decrease in salinity in stage B1 and B2. In stage C1, the salinity of fluid increased greatly and a further decrease of temperature and salinity occurred in stage C2 and C3. Fluids boiled in stage C1. With calculated pressure of 22 MPa from the trapping temperature of 284- 289℃, a mineralization depth of 2.2 km was inferred. Results of Laser Raman Spectroscopy show high density of H2_O, CH_4 and CO_2 were found as gas composition. H-O isotope study indicates the ore- forming fluids were the mixture of magmatic water and meteoric water. Physicochemical parameters of fluids show oxygen and sulfur fugacity experienced a decrease, and redox state is weakly reducing. Along with fluid evolution, oxidation has increased slightly. Comprehensive analysis shows that melt exsolution occurred during the formation of quartz diorite and that metal elements existed and migrated in the form of chlorine complex. Immiscible fluid separation and boiling widely occurred after addition of new fluids, bringing about dissociation of chlorine-complex, resulting in a great deal of copper precipitation. In conclusion, Saishitang deposit, controlled by regional tectonics, is formed by metasomatism between highly fractionated mineralization rock body and wall rock, and belongs to banded skarn Cu-polymetallic deposit.Abstract： Saishitang Cu-polymetallic deposit is located in the southeast section of Late Paleozoic arcfoid in the southeastern margin of Qaidam platform. Accoring to the geological process of the deposit, four mineralization episodes were identified： melt/fluid coexisting period （O）, skarn period （A）, first sulfide period （B） and second sulfide period （C）, and 10 stages were finally subdivided. Three types of inclusions were classified in seven stages, namely crystal bearing inclusions （type I）, aqueous inclusions （type Ⅱ） and pure liquid inclusions （type Ⅲ）. Type I and II inclusions were observed in stage O1, having homogenization temperature from 252 to 431℃, and salinities ranging from 24.3% to 48.0%. Type I inclusion was present in stage A1, having homogenization temperature from 506 to 548℃, and salinities ranging from 39.4% to 44.6%. In stage B1, type II and III inclusions were observed, with homogenization temperature concentrating between 300-400℃, and salinities from 0.4% to 4.3%. Type II inclusions were present in stage B2, with homogenization temperature varying from 403 to 550℃. In stage C1, type I and II inclusion commonly coexisted, and constituted a boiling inclusion group, having homogenization temperatures at 187-463℃, and salinities in a range of 29.4%-46.8% and 2.2%-11.0%. Type II and III inclusions were developed in stage C2, having homogenization temperature at 124-350℃, and salinities ranging between 1.6% and 15.4%. In stage C3, type II and Ⅲ inclusions were presented, with a homogenization temperature range of 164-360℃, and salinities varying from 4.0% to 11.0%. The results of micro-thermal analysis show that fluids are characterized by high temperature and high salinity in stage O1 and A1, and experienced slight decrease in temperature and dramatic decrease in salinity in stage B1 and B2. In stage C1, the salinity of fluid increased greatly and a further decrease of temperature and salinity occurred in stage C2 and C3. Fluids boiled in stage C1. With calculated pressure of 22 MPa from the trapping temperature of 284- 289℃, a mineralization depth of 2.2 km was inferred. Results of Laser Raman Spectroscopy show high density of H_2O, CH_4 and CO_2 were found as gas composition. H-O isotope study indicates the ore- forming fluids were the mixture of magmatic water and meteoric water. Physicochemical parameters of fluids show oxygen and sulfur fugacity experienced a decrease, and redox state is weakly reducing. Along with fluid evolution, oxidation has increased slightly. Comprehensive analysis shows that melt exsolution occurred during the formation of quartz diorite and that metal elements existed and migrated in the form of chlorine complex. Immiscible fluid separation and boiling widely occurred after addition of new fluids, bringing about dissociation of chlorine-complex, resulting in a great deal of copper precipitation. In conclusion, Saishitang deposit, controlled by regional tectonics, is formed by metasomatism between highly fractionated mineralization rock body and wall rock, and belongs to banded skarn Cu-polymetallic deposit.

A Study on the Ore-forming Effect of Mantle-derived Fluid

Based on summarizing of the effect of mantle-derived fluid on the formation of ores, especially on gold ore, and with the latest investigations, such as the formation of ore from the action of shallow-deep fluid, the transportation effect of the thermal energy by mantle-derived fluid, this paper mainly aims at the effect of mantle-derived fluid on the generation of hydrocarbons. With the proof from geochemistry and fluid inclusion, it was suggested that the mantle-derived fluid not only supplied source materials for hydrocarbons, but also supplied essential energy and matter necessary for the generation of hydrocarbons. The mantle-derived fluid had a good effect, but at the same time it had an adverse effect under specific conditions, on the formation of reservoirs. This paper also discusses the future direction and significance of studying mantle-derived fluid.

Ore-forming Fluid and Mineral Source of the Hongshi Copper Deposit in the Kalatage Area, East Tianshan, Xinjiang, NW China

The Hongshi copper deposit is located in the middle of the Kalatage ore district in the northern segment of the Dananhu-Tousuquan island-arc belt in East Tianshan, Xinjiang, NW China. This study analyses the fluid inclusions and H, O, and S stable isotopic compositions of the deposit. The fluid-inclusion data indicate that aqueous fluid inclusions were trapped in chalcopyrite-bearing quartz veins in the gangue minerals. The homogenization temperatures range from 108°C to 299°C, and the salinities range from 0.5% to 11.8%, indicating medium to low temperatures and salinities. The trapping pressures range from 34.5 MPa to 56.8 MPa. The δ^（18）O_（H_2O） values and δD values of the fluid range from -6.94‰ to -5.33‰ and from -95.31‰ to -48.20‰, respectively. The H and O isotopic data indicate that the ore-forming fluid derived from a mix of magmatic water and meteoric water and that meteoric water played a significant role. The S isotopic composition of pyrite ranges from 1.9‰ to 5.2‰, with an average value of 3.1‰, and the S isotopic composition of chalcopyrite ranges from -0.9‰ to 4‰, with an average value of 1.36‰, implying that the S in the ore-forming materials was derived from the mantle. The introduction of meteoric water decreased the temperature, volatile content, and pressure, resulting in immiscibility. These factors may have been the major causes of the mineralization of the Hongshi copper deposit. Based on all the geologic and fluid characteristics, we conclude that the Hongshi copper deposit is an epithermal deposit.

Characteristics and evolution of ore-forming fluids of the Chongjiang copper deposit in the Gangdise porphyry copper belt, Tibet

Petrography, microthermometry, and scanning electron microscope/energy dispersive spectrometer （SEM/EDS） studies were performed on the fluid inclusions in the ore-beating quartz veins and quartz phenocrysts in the porphyry of the Chongjiang porphyry copper deposit. The analyses of the fluid inclusions indicate that the ore-forming fluids were exsolved from magma. They are near-saturated, supercritical, rich in volatile constituents, and have the capture temperature of 362-389℃ and salinities of 17.7wt%- 18.9wt% NaC1 eq. With the decreasing of temperature and pressure, the supercritical fluids were separated into a low salinity vapor phase and a high salinity liquid phase. During quartz-sericitization, the high salinity fluid boiled and separated into a low salinity vapor phase and a high salinity liquid phase. The high salinity inclusions that formed in the boiling process had daughter mineral melting temperatures higher than the homogenization temperatures of the vapor and liquid phases. The late fluids that are responsible for argillization are of lower temperature and salinity.

The Geology, Fluid Inclusions, and O-S Isotopes of the Mibei Gold Deposit, Hunan Province, Southern China

The Mibei gold deposit,located in the southwestern part of the Xuefengshan uplift zone,the middle section of the Jiangnan orogenic belt in southern China,has estimated gold resources of approximately seven tons.This deposit is primarily a quartz vein-type gold deposit,with ore bodies occurring mainly within Neoproterozoic metasediments.The main metallic minerals in the ore are pyrite,chalcopyrite,and arsenopyrite.In this study,the petrography and microthermometry of ore-forming fluid inclusions,oxygen isotopes of gold-bearing quartz,and sulfur isotopes of goldbearing sulfides and arsenopyrite were analyzed.Three types of fluid inclusions were identified:type Ⅰa three-phase inclusions comprising vapor and two phases of liquids(V_(CO_(2))+L_(CO_(2))+L_(H2O)),type Ⅰb two-phase liquids(L_(CO_(2))+L_(H2O)),typeⅡ two-phase vapor-rich inclusions(V/V+L> 50%),and type Ⅲ pure liquid inclusions.Type Ⅰ inclusions were heated uniformly to the liquid phase,type Ⅱ inclusions were heated uniformly to the gas phase,and type Ⅲ inclusions were heated without change.In general,the temperature range of homogenization to liquid phase of fluid inclusions in the Mibei gold deposit is 204-227℃.The salinity of the inclusion ranges from 4.6 to 12.2 wt% NaCl equiv.The δ~(18)O_(SMOW) of gold-bearing quartz varies from 16.9‰ to 17.5‰.The δ~(18)O_(H2O) of gold-bearing quartz are varied from 6.5‰ to 7.5‰.The δ~(34)S values of gold-bearing pyrite range from 1.7‰ to 6.8‰.The δ~(34)S values of gold-bearing arsenopy rite range from 5.6%o to 5.9‰.Theδ~(34)S values of pyrite from wall rocks slate range from 6.4‰ to 11.6‰.This evidence implies that the ore-forming fluids of the Mibei gold deposit originated from magmatic-hydrothermal processes,mixing with minor S from the surrounding metasediments.Combined with the evolution of the Jiangnan orogenic belt,due to the magmatic and tectonic activities of the Xuefengshan uplift during the Caledonian period,the fault seal mechanism controlled the ore-forming process.Overall,the Mibei gold deposit is more akin to a magmatic-hydrothermal gold deposit.

Ore-forming mechanism of Xiajinbao gold deposit in Pingquan, Hebei based on fluid inclusions and stable isotopes

The Xiajinbao gold deposit is located in Yong’an-Xiayingfang-Maojiagou polymetallic metallogenic belt,which is animportant metallogenic belt in North China block.In this paper,we present a detailed study on fluid inclusions and stable isotopes ofthe Xiajinbao gold deposit,Hebei Province,China,aiming at discussing the ore source,evolution of ore-forming fluid andore-forming mechanism of the deposit.The macroscopic geological characteristics,S and Pb isotopic analysis results show that thesource of ore-forming materials is mainly from granitic magma,and subordinately from country rocks.H and O isotopic compositionfeatures indicate that the ore-forming fluid is mainly derived from magmatic water.Fluid inclusion characteristics show that theore-forming fluid experienced boiling during the early mineralization stage,which led to the precipitation of gold.Fluid mixingdominated the precipitation of the ore-forming materials during the middle and late stages.The gold precipitation was caused bywater/rock reaction throughout the whole ore-forming process.

Ore-forming fluid characteristics and ore-forming materials source of the Tudimiaogou – Yindongshan lead-zinc polymetallic orefield, west Henan

1 Introduction The Tudimiaogou-Yindongshan lead-zinc polymetallic orefield is located in the Tudimiaogou-Weimoshi lead and zinc silver polymetallic metallogenic belt.The belt is an important part of southwestern Henan lead and zinc

Characteristics of Ore-forming Fluid of the Gaoshan Gold-Silver Deposit in the Longquan Area, Zhejiang Province and its Implications for the Ore Genesis

The Gaoshan gold-silver deposit, located between the Yuyao-Lishui Fault and Jiangshan- Shaoxing fault in Longquan Area, occurs in the Suichang-Longquan gold-silver polymetallic metallogenic belt. This study conducted an investigation for ore-forming fluids using microthermometry, D-O isotope and trace element. The results show that two types of fluid inclusions involved into the formation of the deposit are pure liquid phase and gas-liquid phase aqueous inclusions. The homogenization temperature and salinity of major mineralization phase ranges from 156~C to 236~C （average 200~C） and 0.35% to 8.68% （NaCleqv） （average 3.68%）, respectively, indicating that the ore-forming fluid is characteristic of low temperature and low salinity. The ore- forming pressure ranges between in 118.02 to 232.13＂105 pa, and it is estabmiated that the ore- forming depth ranges from 0.39 to 0.77 km, indicating it is a hypabyssal deposit in genesis. The low rare earth elements content in pyrites, widely developed fluorite in late ore-forming stage and lack of chlorargyrite （AgCI）, indicates that the ore-forming fluid is rich in F rather than CI. The ratios of Y/ Ho, Zr/Hf and Nb/Ta of between different samples have little difference, indicating that the later hydrothermal activities had no effects on the former hydrothermal fluid. The chondrite-normalized REE patterns of pyrites from country rocks and ore veins are basically identical, with the characteristics of light REE enrichment and negative Eu anomalies, implying that the ore-forming fluid was oxidative and derived partly from the country rocks. The JD and jlSo of fluid inclusions in quartz formed during the main metallogenic stage range from -105%o to -69 %0 and -6.01%o to -3.81%o, respectively. The D-O isotopic diagram shows that the metallogenic fluid is characterized by the mixing of formation water and meteoric water, without involvement of magmatic water. The geological and geochemical characteristics of the Gaoshan gold-silver deposit are similar to those of continental volcanic hydrothermal deposit, and could be assigned to the continental volcanic hydrothermal gold-silver deposit type.

Characteristics of the ore-forming fluid in the Huayuan Pb-Zn ore filed, Northwest of Hunan Province, China

1 Geological Setting The Huayuan Pb-Zn ore field in Xiangxi is located in the southeastern margin of the Yangtze block and the mid-segment of the West Hunan-West Hubei metallogenic belt.The exposed stratum are the lower