Source Enrichment Control on the Scale of Magmatic-Hydrothermal W-Sn Mineralization:Insights from Triassic and Jurassic Magma Reservoirs in the Continental Crust,Xitian,South China

There are two factors,source composition and magmatic differentiation,potentially controlling W-Sn mineralization.Which one is more important is widely debated and may need to be determined for each individual deposit.The Xitian granite batholith located in South China is a natural laboratory for investigating the above problem.It consists essentially of two separate components,formed in the Triassic at ca.226 Ma and Jurassic at ca.152 Ma,respectively.The Triassic and Jurassic rocks are both composed of porphyritic and fine-grained phases.The latter resulted from highlydifferentiated porphyritic ones but they have similar textural characteristics and mineral assemblages,indicating that they reached a similar degree of crystal fractionation.Although both fine-grained phases are highly differentiated with elevated rare metal contents,economic W–Sn mineralization is rare in the Triassic granitoids and this can be attributed to less fertile source materials than their Jurassic counterparts,with a slightly more enriched isotopic signature and whole-rockεNd(226 Ma)of−10.4 to−9.2(2σ=0.2)compared withεNd(152 Ma)of−9.2 to−8.2(2σ=0.2)for the Jurassic rocks.The initial W-Sn enrichment was derived from the metasedimentary rocks and strongly enhanced by reworking of the continental crust,culminating in the Jurassic.

Mineralization of the Liwu large-scale stratiform copper deposits in Sichuan Province, China: Constraints from fluid inclusions

The Liwu stratiform copper deposit is located in the northwestern Jianglang dome,western China.Current studies mainly focus on the genetic type and mineralization of this deposit.Detailed fluid inclusion characteristics of metallogenic period quartz veins were studied to reveal the ore-forming fluid features.Laser Raman analysis indicates that the ore-forming fluids is a H_(2)O-NaCl-CH_(4)(-CO_(2))system.Fluid inclusions microthermometry shows a homogenization temperature of 181-375°C and a salinity of 5.26%-16.99%for the disseminated-banded Cu-Zn mineralization;but a homogenization temperature of 142-343°C and a salinity of 5.41%-21.19%for the massive-veined Cu-Zn mineralization.These features suggest a medium-high temperature and a medium salinity for the ore-forming fluids.H-O isotopic data indicates that the ore-forming fluids were mainly from the metamorphic and magmatic water,plus minor formation water.And sulfur isotopic data indicates that sulfur was mainly derived from the formation and magmatic rocks.Metallogenesis of the disseminated-banded mineralization was mainly correlated with fluid mixing and water-rock reaction;whereas that of the massive-veined mineralization was mainly correlated with fluid boiling.The genetic type of the deposit is a medium-high temperature hydrothermal deposit related to magmatism and controlled by shear zones.This study is beneficial to understand the stratiform copper deposit.

Numerical modelling of structural controls on fluid flow and mineralization

This paper presents the results of a set of numerical models focussing on structural controls on hydrothermal mineralization. We first give an overview of natural phenomena of structurally-controlled ore formation and the background theory and mechanisms for such controls. We then provide the results of a group of simple 2D numerical models validated through comparison with Cu-vein structure observed near the Shilu Copper deposit （Yangchun, Guangdong Province, China） and finally a case study of 3D numerical modelling applied to the Hodgkinson Province in North Queensland （Australia）. Two modelling approaches, discrete deformation modelling and continuum coupled deformation and fluid flow modelling, are involved. The 2D model-derived patterns are remarkably consistent with the Cu-vein structure from the Shilu Copper deposit, and show that both modelling approaches can realistically simulate the mechanical behaviours of shear and dilatant fractures. The continuum coupled deformation and fluid flow model indicates that pattern of the Cu- veins near the Shilu deposit is the result of shear strain localization, development of dilation and fluid focussing into the dilatant fracture segments. The 3D case-study models （with deformation and fluid flow coupling） on the Hodgkinson Province generated a number of potential gold mineralization

Basin Fluid Mineralization during Multistage Evolution of the Lanping Sedimentary Basin,Southwestern China

The Lanping sedimentary basin has experienced a five-stage evolution since the late Paleozoic： ocean-continent transformation （late Paleozoic to early mid-Triassic）; intracontinental rift basin （late mid-Triassic to early Jurassic）; down-warped basin （middle to late Jurassic）; foreland basin （Cretaceous）; and strike-slip basin （Cenozoic）. Three major genetic types of Ag-Cu polymetallic ore deposits, including the reworked hydrothermal sedimentary, sedimentary-hydrothermally reworked and hydrothermal vein types, are considered to be the products of basin fluid activity at specific sedimentary-tectonic evolutionary stages. Tectonic differences of the different evolutionary stages resulted in considerable discrepancy in the mechanisms of formation-transportation, migration direction and emplacement processes of the basin fluids, thus causing differences in mineralization styles as well as in genetic types of ore deposit.

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.

Metallogenetic Mechanism and Timing of Late Superimposing Fluid Mineralization in the Dongguashan Diplogenetic Stratified Copper Deposit,Anhui Province

An important diplogenetic mineralization event superimposed on pre-existing exhalation sediments in the Tongling area, Anhui province, was triggered by widespread granitic magmatism along the northeastern margin of the Yangtze Block during 140–135 Ma under extensional tectonic circumstances following the collision between the North China and Yangtze blocks. The main orebodies of the Dongguashan copper deposit, a typical diplogenetic stratified deposit among many polymetallic ore deposits in China, are hosted by strata between Upper Devonian sandstone and Carboniferous limestone, and its mineralization was genetically related to the Qingshanjiao intrusive. The Rb-Sr isotopic isochron of the Qingshanjiao intrusive yields an age of about 136.5±1.4 Ma. The ore-forming fluid reflected by the inclusion fluid in quartz veins is characterized by high temperature and high salinity, and its age was also determined by Rb -Sr isotope dating as 134±11 Ma. Oxygen and hydrogen isotope composition data suggest that the ore-forming fluid was derived mainly from magmatism. By integrating these isotopic dating data, characteristics of fluid inclusions and the geology of the deposit, the mineralization of the Dongguashan copper deposit is divided into two stages. First, a stratiform sedimentary deposit or protore layer formed in the Late Devonian to the Early Carboniferous, while in the second stage the pre-existing protore was superimposed by hydrothermal fluid that was derived from the Yanshanian magmatic activities occurring around 135 Ma ago. This two-stage mineralization formed the Dongguashan statiform copper deposit. Associated “porphyry” mineralization found in the bottom of and in surrounding intrusive rocks of the orebodies might have occurred in the same period as a second-stage mineralization of this deposit.

EVOLUTION OF ORE-FORMING FLUIDS AND Ag-Cu POLYMETAL MINERALIZATION IN THE LANPING BASIN, YUNNAN

The Lanping Mesozoic—Cenozoic sedimentary basin, situated in the Middle section of the “Sanjiang" (Nujiang—Lancangjiang—Jinshajiang) area in the east margin of the Tibet plateau, is well known for its large production of base\|metal sulphide deposits. The worldwide famous super\|large Jinding Pb\|Zn deposit is located in the middle of the basin. The evolution history of the Lanping basin since Mesozoic can be divided into six stages, i.e., ①active continental marginal basin (T 1—T 2); ②back\|arc rift basin (T 3—J 1); ③intracontinental depressive basin (J 2—J 3); ④foreland basin (K); ⑤strike\|slipping and mutual thrusting (E 1—E 3); and ⑥strike\|slipping and pull\|apart basin (N 1\|present). Three main types of Ag\|Cu polymetal deposits are recognized in the basin. Deposits of sedimentary exhalation\|hydrothermal reworking origin (type Ⅰ) are hosted chiefly in limestones, dolomitic limestones, and siliceous rocks of the Upper Triassic Sanhedong Formation (T 3 s ) in Sanshan area. Deposits formed through normal chemical sedimentation in closed to semi\|closed environments (type Ⅱ; e.g., Jinman and Baiyangchang) during the depressive and foreland basin stages occur in various horizons of Jurassic and Cretaceous ages. Hydrothermal reworking on deposits of this type during the Himalayan period are locally pronounced, especially in the west margin of the basin near the Lancangjiang thrust fault. The third deposit type in the basin (type Ⅲ; e.g., Baiyangping and Fulongchang) is the Ag\|bearing tetrahedrite vein deposits occurring almost in all Mesozoic—Cenozoic strata, especially in the Cretaceous. Ore minerals formed during synsedimentary periods of types Ⅰ and Ⅱ are relatively simple and dominated by chalcopyrite and bornite, though sphalerite, galena, pyrite, tetrahedrite and pyrite are also present. In the deposits of type Ⅲ as well as in the ores formed during the hydrothermal reworking period in deposits of type Ⅰ and Ⅱ, ore minerals are extremely complicated and characterized by predominant Ag\|bearing tetrahedrite and other complex sulfosalts of Cu\|Ni\|Co\|Fe\|As\|S and Cu\|Bi\|S series. The associated gangue minerals are mainly quartz, siderite, Fe\|dolomite, barite, and celestite.

A Fluid Inclusion Study of Vein-type Copper Mineralization in the East Wulasigou Pb-Zn-Cu Deposit,Altay,Northwestern China

The Wulasigou Cu-Pb-Zn deposit,located 15 km northwest of Altay city in Xinjiang,is one of many Cu-Pb-Zn polymetallic deposits in the Devonian Kelan volcanic-sedimentary basin in southern Altaids.Two mineralizing periods can be distinguished：the marine volcanic sedimentary PbZn mineralization period,and the metamorphic hydrothermal Cu mineralization period,which is further divided into an early bedded foliated quartz vein stage（Q1） and a late sulfide-quartz vein stage（Q2） crosscutting the foliation.Four types of fluid inclusions were recognized in the Q1 and Q2 quartz from the east orebodies of the Wulasigou deposit：H2O-CO2 inclusions,carbonic fluid inclusions,aqueous fluid inclusions,and daughter mineral-bearing fluid inclusions.Microthermometric studies show that solid CO2 melting temperatures（T（m,CO2）） of H2O-CO2 inclusions in Ql are from-62.3℃ to-58.5C,clathrate melting temperatures（T（m,clath）l） are from 0.5 C to 7.5 C,partial homogenization temperatures（T（h,CO2）） vary from 3.3℃ to 25.9℃（to liquid）,and the total homogenization temperatures（T（h,tot）） vary from 285℃ to 378℃,with the salinities being 4.9%-15.1%NaCl eqv.and the CO2-phase densities being 0.50-0.86 g/cm-3.H2O-CO2 inclusions in Q2 have T（m,CO2） from-61.9℃ to-56.9℃,T（m,clath）from 1.3℃ to 9.5℃,T（h,CO2） from 3.4℃ to 28.7℃（to liquid）,and T（h,tot） from 242℃ to 388℃,with the salinities being 1.0%-15.5%NaCl eqv.and the CO2-phase densities being 0.48-0.89 g/cm-3.The minimum trapping pressures of fluid inclusions in Q1 and Q2 are estimated to be 260-360 MPa and180-370 MPa,respectively.The δ-（34）S values of pyrite from the volcanic sedimentary period vary from2.3‰ to 2.8‰（CDT）,and those from the sulfide-quartz veins fall in a narrow range of-1.9‰ to 2.6‰（CDT）.The δD values of fluid inclusions in Q2 range from-121.0‰ to-100.8‰（SMOW）,and theδ-（18）O（H2O） values calculated from δ-（18）O of quartz range from-0.2‰ to 8.3‰（SMOW）.The δD-δ-（18）O（H2O）data are close to the magmatic and metamorphic fields.The fluid inclusion and stable isotope data documented in this study indicate that the vein-type copper mineralization in the Wulasigou Pb-Zn-Cu deposit took place in an orogenic-metamorphic enviroment.

Melt extraction and mineralization: A case study from the Shuangjianzishan supergiant Ag-Pb-Zn deposit(208 Mt), Inner Mongolia, NE China

The supergiant Shuangjianzishan(SJZ) Ag-Pb-Zn deposit is in the southern segment of the Great Hinggan Range(SGHR), northeast China. Previous studies suggest the ore-forming material and fluid originated from the magmatic system, and the mineralization age was consistent with the diagenetic age. However,the relationship between granitic magmatism and mineralization is still unclear in the SJZ. In this study, CH-O-He-Ar and in-situ S-Pb isotope analyses were conducted to determine the sources of ore-forming fluids and metals, which were combined with geochemistry data of SJZ granitoids from previous studies to constrain the relationship between the magmatism and the mineralization. The C-H-O-He-Ar-S-Pb isotopic compositions suggested the SJZ ore-forming material and fluids were derived from a magmatic source, which has mixed a small amount of mantle-derived materials. In addition, the disseminated sulfide from the syenogranite has comparable S-Pb isotopic composition with the sulfide minerals from ore veins,suggesting that the generation of the SJZ ore-forming fluids has a close relationship with the syenogranite magmatism. Combining with the geochemical characters of the syenogranite, the authors proposed that the mantle-derived fingerprint of the SJZ ore-forming fluid might be caused by the parent magma of the syenogranite, which was derived from partial melting of the juvenile lower crust, and underwent the residual melts segregated from a crystal mush in the shallow magma reservoir. The extraction of the syenogranite parent magma further concentrated the fertilized fluids, which was crucial to mineralization of the SJZ Ag-Pb-Zn deposit.

Geology and mineralization of the Daheishan supergiant porphyry molybdenum deposit(1.65 Bt),Jilin,China:A review

The Daheishan supergiant porphyry molybdenum deposit(also referred to as the Daheishan deposit)is the second largest molybdenum deposit in Asia and ranks fifth among the top seven molybdenum deposits globally with total molybdenum reserves of 1.65 billion tons,an average molybdenum ore grade of 0.081%,and molybdenum resources of 1.09 million tons.The main ore body is housed in the granodiorite porphyry plutons and their surrounding inequigranular granodiorite plutons,with high-grade ores largely located in the ore-bearing granodiorite porphyries in the middle-upper part of the porphyry plutons.Specifically,it appears as an ore pipe with a large upper part and a small lower part,measuring about 1700 m in length and width,extending for about 500 m vertically,and covering an area of 2.3 km^(2).Mineralogically,the main ore body consists of molybdenite,chalcopyrite,and sphalerite horizontally from its center outward and exhibits molybdenite,azurite,and pyrite vertically from top to bottom.The primary ore minerals include pyrite and molybdenite,and the secondary ore minerals include sphalerite,chalcopyrite,tetrahedrite,and scheelite,with average grades of molybdenum,copper,sulfur,gallium,and rhenium being 0.081%,0.033%,1.67%,0.001%,and 0.0012%,respectively.The ore-forming fluids of the Daheishan deposit originated as the CO_(2)-H_(2)O-NaCl multiphase magmatic fluid system,rich in CO_(2)and bearing minor amounts of CH4,N2,and H2S,and later mixed with meteoric precipitation.In various mineralization stages,the ore-forming fluids had homogenization temperatures of>420℃‒400℃,360℃‒350℃,340℃‒230℃,220℃‒210℃,and 180℃‒160℃and salinities of>41.05%‒9.8%NaCleqv,38.16%‒4.48%NaCleqv,35.78%‒4.49%NaCleqv,7.43%NaCleqv,and 7.8%‒9.5%NaCleqv,respectively.The mineralization of the Daheishan deposit occurred at 186‒167 Ma.The granites closely related to the mineralization include granodiorites(granodiorite porphyries)and monzogranites(monzogranite porphyries),which were mineralized after magmatic evolution(189‒167 Ma).Moreover,these mineralization-related granites exhibit low initial strontium content and high initial neodymium content,indicating that these granites underwent crust-mantle mixing.The Daheishan deposit formed during the Early-Middle Jurassic,during which basaltic magma underplating induced the lower-crust melting,leading to the formation of magma chambers.After the fractional crystallization of magmas,ore-bearing fluids formed.As the temperature and pressure decreased,the ore-bearing fluids boiled drops while ascending,leading to massive unloading of metal elements.Consequently,brecciated and veinlet-disseminated ore bodies formed.

Fluid Inclusion Investigations of the Masjed Daghi Copper-Gold Porphyry-Epithermal Mineralization, East Azerbaijan Province, NW Iran

The Masjed Daghi mineralization is located 30 km southeast of Jolfa city at the bank of Araxes River, northwest Iran. This area is situated in the Alborz-Azarbaijan structural zone of Iran. The most widespread rocks in the mineralization area are andesite and trachyandesite, while there are rock units of latite tuff, andesitic agglomerate, and hornblende porphyry basalt in eastern hills and Eocene flysch in the southern part of the area. Several intrusive bodies are present in the study area, from which the dominant intrusive rock hosting the mineralization is diorite porphyry. The mineralized rock units of the area are cut by different diorite ad mafic dikes. The most prevalent texture of mineralization is dissemination, while open space filling textures including veins and veinlets, are common as well. Diverse types of alteration including potassic, phyllic, argillic, silicification, and a little of carbonatization were recognized in the field and microscopic observations as well as by XRD. In addition to thick silica veins and stockwork zones, some silica, barite, sulfide, and calcite veins and veinlets have occurred in the Masjed Daghi mineralization area. In this research, 26 doubly polished thin sections (wafers) were prepared and investigated. Four samples were taken from surface veins, while 22 samples were chosen from core samples (of 6 boreholes) of white and grey-white silica, and silica-barite veins. The fluid inclusion studies on 105 primary fluid inclusions indicated five phases for inclusions including: 1) liquid or gas, 2) liquid and gas, 3) liquid, gas, and solid, 4) liquid, gas, halite, and solid, and 5) liquid, gas, halite, and two types of solids. The data gained from fluid inclusions approved two mineralization fluids which caused porphyry and epithermal mineralizations. The porphyry fluid inclusions were homogenized in temperatures of 122°C to 550°C with a maximum of 700°C and average salinity of 55 wt% NaCl equivalent, while the epithermal inclusions indicated an average homogenization temperature of 186°C with an average salinity of 6.23 wt% NaCl equivalent.

Fluid-melt Inclusions in Fluorite of the Huanggangliang Skarn Iron-Tin Deposit and Their Significance to Mineralization

For the first time, fluid-melt inclusions are found in fluorite of the Huanggangliang skarn iron-tin deposit (HSID). The fluorite was formed in the main stage of mineralization, named the hydro-skarnization stage. The inclusions contain various components such as Fe, Mg and Cr from deep sources. The melts of primary inclusions are mainly Ca- and F-rich and those of secondary inclusions tend to become Si-rich. During this evolution process, the melts and iron daughter minerals decreased and even vanished. These facts reveal that the evolution of the primary mineralizing fluids and the differentiation of the fluids and melts are the main factors leading to the deposition of Fe, Sn and other elements. This discovery confirms the magmatic genesis of the HSID and has filled in the gaps in the research of magmatogenic skarn deposits and furnished new methods for such research. Furthermore, it has enlarged the scope of the research on fluid inclusions.

Evolution of Diagenetic Fluid of the Dawsonite-Bearing Sandstone in the Jiyang Depression,Eastern China

Based on the petrology,isotope geochemistry and fluid inclusions analysis,we established the evolutionary mode of the diagenetic fluid of dawsonite-bearing sandstone in the Jiyang Depression.Dawsonite-bearing sandstone is characterized by double injection of CO_(2)and oil-gas in the Jiyang Depression that have experienced a relatively complex diagenetic fluid evolution process.The diagenetic sequence of secondary minerals involves secondary enlargement of quartz,kaolinite,first-stage calcite,dawsonite,second-stage calcite,ferrocalcite,dolomite and ankerite.Hydrocarbon charging in the dawsonite-bearing sandstone occurred at around 2.6–0 Myr.The CO_(2)charging event occurred during Dongying tectonism,forming the Pingfangwang CO_(2)gas reservoir,which provided an abundant carbon source for dawsonite precipitation.Carbon and oxygen isotopic compositions of dawsonite demonstrate that CO_(2)forming the dawsonite was of an inorganic origin derived from the mantle,and that water mediating the proc-ess during dawsonite precipitation was sequestered brine with a fluid temperature of 82℃.The evolutionary sequence of the diagenetic fluid in the dawsonite-bearing sandstone was:alkaline syngenetic fluids,weak alkaline fluids during organic acid forma-tion,acidic fluids in the early stage of CO_(2)injection,alkaline fluids in the late stage of CO_(2)injection,and weak alkaline fluids during oil and gas charging.The mode indicates an increase in-HCO_(3)because of the CO_(2)injection,and the loss of Ca^(2+)and Mg^(2+)due to the precipitation of carbonate minerals.Therefore,the evolutionary mode of diagenetic fluids is in good agreement with high HCO_(3)^(-),low Ca^(2+)and low Mg^(2+)composition of the present formation water in the dawsonite-bearing sandstone.

Study on Epithermal Gold Mineralization System at Shwebontha Prospect,Monywa Copper-Gold Ore Field,Central Myanmar

The Shwebontha prospect area is situated in the Central Volcanic Belt,central Myanmar,where the well-known Sagaing Fault serves as its eastern boundary.This study aims to document key the mineralogy,host rock geochemistry and ore mineralizing fluids.The mineralization,hosted by Upper Oligocene to Middle Miocene rhyolites,displays a strong lithological control.Mineralization is characterized by gold-bearing silicified massive ore and chalcedonic quartz veins in which sulfides are clustered and disseminated not only in quartz gangue but also in rhyolite host rocks.The significant ore minerals in the mineralized veins include pyrite,sphalerite,galena,chalcopyrite,and gold.Common hydrothermal alterations such as silicic,argillic and propylitic alteration types are recognized.According to the fluid inclusion data and interpretation,ore mineralizing fluids in the research area are characterized by formation temperatures of 260-280℃ and salinity of 0.35-2.41%wt.NaCl eq.respectively.Mixing of hydrothermal fluids was generally considered to be an effective mechanism for ore transport and deposition.

Relationship between CO_2-bearing fluid and gold mineralization in Haigou gold deposit of Jilin

Haigou gold deposit is a typical orogenic gold deposit. There are a reasonable amount of fluid inclusions in the gold deposit,including three types: CO2-H2O-Na Cl inclusions,pure CO2 inclusions and Na Cl-H2 O inclusions,of which most of them are CO2-bearing inclusions. The fluid salinity is 1. 43%- 9. 08%,mainly concentrated in the range of 4. 69%- 5. 41%,the density of CO2 is 0. 69- 0. 80 g / cm3,indicating that the mineralization fluid is low-medium salinity and low density fluid. A series of studies on gold-bearing quartz vein and fluid inclusions show that there exists a positive correlation between the degree of the gold mi-neralization and the amount of CO2 in the inclusions,which means the more CO2-bearing inclusions there are,the higher the content of gold is. CO2 is mainly derived from mantle fluid,and the ore-forming fluid should be derived from mantle fluid and the crust shallow fluid. The conclusions have important denotative meaning on the metallogenic mechanism of orogenic gold deposit and the deep prospecting on metal deposit.

GEOTHERMAL FLUID MINERALIZATION──A NEW HYDROTHERMAL MINERALIZATION MODEL

In hydrothermal mineralization regime, there should be some other models besideS the commonly accepted traditional magmatic and metamorphic hydrothermal ones. The authors suggest a new model named as geothermal nuid mineralization and believe it is an important and distinguishable hydrotherma1 mineralization model. The discussions are focused on several aspects of the new model in its distinguishing features in essential factors of hydrothermal mineralization, essential metallogenic conditions, common metallogenic characteristics, general mineralization process,geotectonic control and metallogenic importance.

Metallogenic Processes:Evidencesfrom Zoning Patterns of Mineralization and alteration and fluid inclusion geochemistryin the Lehong Zn-Pb Deposit in Northeastern Yunnan, China

1 Introduction The large clusters of Zn-Pb deposits in northeastern Yunnan,located in the southwestern margin of the Yangtze Block,are an important part of the Sichuan-YunnanGuizhou Pb-Zn Poly-metallic Metallogenic Triangle Area

Magmatic-hydrothermal Evolution and Mineralization Mechanisms of the Wangjiazhuang Cu(-Mo)Deposit in the Zouping Volcanic Basin,Shandong Province,China:Constraints from Fluid Inclusions

The Wangjiazhuang Cu(-Mo)deposit,located within the Zouping volcanic basin in western Shandong Province,China,is unique in this area for having an economic value.In order to expound the metallogenetic characteristics of this porphyry-like hydrothermal deposit,a detailed fluid inclusion study has been conducted,employing the techniques of representative sampling,fluid inclusion petrography,microthermometry,Raman spectroscopy,LA-ICP-MS analysis of single fluid inclusions,as well as cathode fluorescence spectrometer analysis of host mineral quartz.The deposit contains mainly two types of orebodies,i.e.veinlet-dissemination-stockwork orebodies in the K-Si alteration zone and pegmatiticquartz sulfide veins above them.In addition,minor breccia ore occurs locally.Four types of fluid inclusions in the deposit and altered quartz monzonite are identified:L-type one-or two-phase aqueous inclusions,V-type vapor-rich inclusions with V/L ratios greater than 50%-90%,D-type multiphase fluid inclusions containing daughter minerals or solids and S-type silicate-bearing fluid inclusions containing mainly muscovite and biotite.Ore petrography and fluid inclusion study has revealed a three-stage mineralization process,driven by magmatic-hydrothermal fluid activity,as follows.Initially,a hydrothermal fluid,separated from the parent magma,infiltrated into the quartz monzonite,resulting in its extensive K-Si alteration,as indicated by silicate-bearing fluid inclusions trapped in altered quartz monzonite.This is followed by the early mineralization,the formation of quartz veinlets and dissemination-stockwork ores.During the main mineralization stage,due to the participation and mixing of meteoric groundwater with magmatic-sourced hydrothermal fluid,the cooling and phase separation caused deposition of metals from the hydrothermal fluids.As a result,the pegmatitic-quartz sulfide-vein ores formed.In the late mineralization stage,decreasing fluid salinity led to the formation of L-type aqueous inclusions and chalcopyrite-sulfosalt ore.Coexistence of V-type and D-type inclusions and their similar homogenization temperatures with different homogenization modes suggest that phase separation or boiling of the ore-forming fluids took place during the early and the main mineralization stages.The formation P-T conditions of S-type inclusions and the early and the main mineralization stages were estimated as ca.156-182 MPa and 450-650℃,350-450℃,18-35 MPa and 280-380℃,8-15 MPa,respectively,based on the microthermometric data of the fluid inclusions formed at the individual stages.

An overview of hydrodynamic studies of mineralization

Fluid flow is an integral part of hydrothermal mineralization, and its analysis and characterization constitute an important part of a mineralization model. The hydrodynamic study of mineralization deals with analyzing the driving forces, fluid pressure regimes, fluid flow rate and direction, and their relationships with localization of mineralization. This paper reviews the principles and methods of hydrodynamic studies of mineralization, and discusses their significance and limitations for ore deposit studies and mineral exploration. The driving forces of fluid flow may be related to fluid overpressure, topographic relief, tectonic deformation, and fluid density change due to heating or salinity variation, depending on specific geologic environments and mineralization processes. The study methods may be classified into three types, megascopic （field） observations, microscopic analyses, and numerical modeling. Megascopic features indicative of significantly overpressured （especially lithostatic or supralithostatic） fluid systems include horizontal veins, sand injection dikes, and hydraulic breccias. Microscopic studies, especially microthermometry of fluid inclusions and combined stress analysis and microthermometry of fluid inclusion planes （FIPs） can provide important information about fluid temperature, pressure, and fluid-structural relationships, thus constraining fluid flow models. Numerical modeling can be carried out to solve partial differential equations governing fluid flow, heat transfer, rock deformation and chemical reactions, in order to simulate the distribution of fluid pressure, temperature, fluid flow rate and direction, and mineral precipitation or dissolution in 2D or 3D space and through time. The results of hydrodynamic studies of mineralization can enhance our understanding of the formation nrocesses of hvdrothermal denosits, and can be used directly or indirectly in mineral exnloration.