Red Clay Type Gold Deposits in China

Red clay type gold deposits,located in the south of China,are situated not only in orogenic belts,but also in inner cratons,where climate is tropical-subtropical with clear arid and humid.The lateritic weathering crust often can be divided into five zones,including topsoil,siliceous duricrust zone,multi-color zone(or red clay zone in some deposits),pallid zone and saprolite zone from surface to the base rock,several of which are absent in some deposits.The base rocks are composed mainly of carbonate rocks with minor clastic rocks,intermediate-basic volcanic rocks and intermediate-acid and alkalic intrusions.The orebodies are mainly located in the multi-color zone with part of them in the pallid and saprolite zones.The ore sources include orebodies of Carlin-type gold deposits and porphyry gold deposits,as well as gold-rich base rocks.The red clay type gold deposits experienced early-stage endogenic gold mineralization and laterization during the Tertiary and Quaternary.The areas with endogenic gold deposits,especially Carlin-type gold deposits and porphyry gold deposits in karst depressions on the plateau,structual erosional platforms in the middle-lower mountains,and intermountain basins in southern China are well worth studying to trace red clay type gold deposits.

The Bulong Gold Deposit-a Quartz-Barite Vein Type Gold Deposit in Xinjiang:Geological Characteristics and S, He and Ar Isotopic Compositions

The Bulong gold deposit, located in the southwest Tianshan in China, occurs in the Upper Devonian finegrained clastic rocks. The gold orebodies are controlled by an gently inclined interlayer fractured zone. They are hosted only in quartz-barite veins though there are barite veins and quartz veins in the ore district. The δ34S values of pyrite in the ores range from 14.6‰ to 19.2‰ and those of barite from 35.0‰ to 39.6‰, indicating that the sulfur was derived from the strata. 3He/4He ratios of fluid inclusions in pyrite are 0.24-0.82 R/Ra, approximating to that of the crust. The 40Ar/39Ar ratios range from 338 to 471, slightly higher than that of the atmosphere. 40Ar /4He ratios of ore fluids range from 0.015 to 0.412 with a mean of 0.153. Helium and argon isotope compositions of fluid inclusions show that the ore fluids of the Bulong gold deposit were mainly derived from the crust.

Genetic Types and Metallogenic Model for the Polymetallic Copper–Gold Deposits in the Tongling Ore District, Anhui Province, Eastern China

The Tongling ore district is one of the most economically important ore areas in the Middle–Lower Yangtze River Metallogenic Belt, eastern China. It contains hundreds of polymetallic copper–gold deposits and occurrences. Those deposits are mainly clustered(from west to east) within the Tongguanshan, Shizishan, Xinqiao, Fenghuangshan, and Shatanjiao orefields. Until recently, the majority of these deposits were thought to be skarn-or porphyry–skarn-type deposits; however there have been recent discoveries of numerous vein-type Au, Ag, and Pb-Zn deposits that do not fall into either of these categories. This indicates that there is some uncertainty over this classification. Here, we present the results of several systematic geological studies of representative deposits in the Tongling ore district. From investigation of the ore-controlling structures, lithology of the host rock, mineral assemblages, and the characteristics of the mineralization and alteration within these deposits, three genetic types of deposits(skarn-, porphyry-, and vein-type deposits) have been identified. The spatial and temporal relationships between the orebodies and Yanshanian intrusions combined with the sources of the ore-forming fluids and metals, as well as the geodynamic setting of this ore district, indicate that all three deposit types are genetically related each other and constitute a magmatic–hydrothermal system. This study outlines a model that relates the polymetallic copper–gold porphyry-, skarn-, and vein-type deposits within the Tongling ore district. This model provides a theoretical basis to guide exploration for deep-seated and concealed porphyry-type Cu(–Mo, –Au) deposits as well as shallow vein-type Au, Ag, and Pb–Zn deposits in this area and elsewhere.

A Comparison of Carlin-type Gold Deposits：Guizhou Province,Golden Triangle,Southwest China,and Northern Nevada,USA

Several Au deposits in Guizhou Province,southwest China,described as being similar to the highly productive Carlin-type gold deposits in northern Nevada.USA,were examined to identify similarities and differences between the two districts.Samples were collected along transects from lowto high-grade rock,where possible,and fram stockpiles at the Shuiyindong,Zimudang,Taipingdong,Yata and Jinfeng(formerly Lannigou)deposits.Methods used to examine ore and alteration minerals included hand-sample description:reflectance spectroscopy using an ASD Terraspec spectrometer;analyses of hand samples by carbonate staining with Alizaren red and potassium ferricyanide;transmitted and reflected light petrography;chemical analyses,mineral identification,and imaging using a JEOL.JSM-5610 scanning electron microscope:and quantitative chemical analyses using a JEOL JXA-8900 electron probe microanalyzer.Geochemical analyses of hand samples for 52 elements were done by ALS Chemex.Results indicate both similarities and differences between the two districts.Both districts have similar geologic histories.and deposits at both locations appear to have formed as a result of similar tectonic events.though the district in southwest China lacks evidence of eoeval felsic igneous activity;however,the ore-stage minerals and the fluids that produced the minerals and deposits have some significant differences.The Nevada deposits were dominated by fluid-rock reaction in which host rock Fe was sulfidized to form Au-bearing pyrite.Although ore fluids sulfidized host rock Fe in the Cuizhou deposits.the timing of Fe metasomatism is unknown,so whether the deposits formed in response to sulfidation or pyritization is unclear.Fluid-rock reaction between an acidic,aqueous fluid and highly reactive calcareous rocks in Nevada caused extensive decarbonatization of host rocks,jasperoid replacemerit of carbonate minerals,and alteration of silty rock components to illite and kaolinite.In Guizhou,CO2-bearing ore fluids with temperatures and pressures approaching 100℃ and 500 bars greater than temperatures and pressures detemained for ore fluids in the Nevada deposits,deposited Aubearing pyrite.In examined Guizhou deposits these fluids carbonatized host rocks and farmed both replacement and open-space-filling ore.The fluids,which may have been immiscible,were sufficiently overpressured to fracture wall rocks and to create significant open space filled by vein quartz.While deposit architecture,tectonic setting,and host rocks in Guizhou are quite similar to northern Nevada,ore and alteration minerals suggest that ore-forming processes in examined Guizhou deposits have important similarities to processes associated with formation of orogenic Au systems.The Guizhou deposits display characteristics of both Carlin-type and orogenic systems,perhaps indicating formation at conditions somewhat intermediate to conditions for Carlin-type deposits and orogenic systems.

S, C, O, H, and Pb isotopic studies for the Shuiyindong Carlin-type gold deposit, Southwest Guizhou, China: constraints for ore genesis

The Shuiyindong gold deposit is one of the most famous and largest Carlin-type gold deposits in China and is located in southwest Guizhou, in the eastern part of the Huijiabao anticline. The Shuiyindong's gold mineralization occurred in bioclastic limestone of the Permian Longtan Formation. Sulfur, carbon, hydrogen, oxygen, and lead isotopic compositions are reported in this paper. The properties and sources of ore-forming fluid have been discussed and a metallogenic model for the Shuiyindong gold deposit has been proposed. The d34 S values of stibnite, realgar, orpiment, pyrite from orebodies, and pyrite from quartz veins are similar to or slightly higher than the d34 S values of mantle sulfur. It is suggested that the sulfur of hydrothermal sulfides was likely of magmatic origin with minor heavy sulfur contributed from the country rocks. The measured d D values and calculated d18OH2 O values of inclusion fluid in quartz plotted within or below a magmatic hydrothermal fluid field far from the meteoric water line. This indicates that the ore-forming fluid for the main-stage gold mineralization could have been derived mainly from a magmatic source and mixed with a small amount of meteoric water. The carbon and oxygen isotopic compositions of calcites in the d18 O vs. d13 C diagram suggest that the CO2 in ore-forming fluid was derived from dissolution of bioclastic limestone and oxidation of sedimentary organic carbon in limestone. However, the d13 C values of ore-related calcites, which contain intergrown realgar and/or orpiment, are similar to those of mantle carbon. Although no igneous intrusive rock has been observed in the vicinity of the gold deposits, the possibility of mantle fluid integrated into the ore-forming fluid cannot be eliminated based on the d13 C values of ore-related calcites. The lead isotopes of sulfides are distributed near the growth curves of upper crust and orogenic belt in the plumbotectonic diagram. Their calculated Dc and Db values plotted within the magmatism field of crust-mantle subduction zone in the Dc- Db diagram. This suggests that the lead of sulfides has an intimate connection with magmatism. Our S, H, O, C, and Pb isotopic studies for the Shuiyindong Carlin-type gold deposit in Guizhou manifest a concordant possibility that the ore-forming fluid was mainly derived from magmatic fluid with minor contribution from the surrounding strata. With the integration of comprehensive geology and isotopic geochemistry, we have proposed a magmatic hydrothermal model for the origin of the Shuiyindong gold deposit.

In-situ sulfur isotope and trace element of pyrite constraints on the formation and evolution of the Nibao Carlin-type gold deposit in SW China

The fault-controlled Nibao Carlin-type gold deposit,together with the strata-bound Shuiyindong deposit,comprise a significant amount of the disseminated gold deposits in southwestern Guizhou Province,China.Five main types and two sub-types of pyrite at the Nibao deposit(Py1a/Py1b,Py2,Py3,Py4,Py5)were distinguished based on detailed mineralogical work.Py1,Py2and Py3 are Au-poor,whereas Py4 and Py5 are Au-rich,corresponding to a sedimentary and hydrothermal origin,respectively.Through systematic in situ analyses of NanoSIMS sulfur isotopes,the framboid pyrite Py1a with negative δ^34S values(-53.3 to-14.9%)from the Nibao deposit were found to originate from bacterial sulfate reduction(BSR)processes in an open and sulfate-sufficient condition while the superheavy pyrite Py1b(73.7–114.8%)is probably due to the potential influence of closed-system Rayleigh fractionation or the lack of preservation of deepsea sediments.Data of Py2 and Py3 plot within the area of S isotope compositions from biogenic and abiogenic sulfate reduction.In view of few coeval magmatic rocks in the mining district,the near zero δ^34S values of the Au-rich pyrites(Py4 and Py5)may discount the potential involvement of magmatic but metamorphic or sedimentary origin.LA-ICP-MS and TEM work show that Au in ore-related pyrite is present as both nanoparticles and structurally bound.LA-ICP-MS analyses show that the Au-rich pyrite also contains higher As,Cu,Sb,Tl and S than other types of pyrite,which inferred a distal manifestation of deep hydrothermal mineralization systems.

Metallogenic model and prognosis of the Shuiyindong super-large strata-bound Carlin-type gold deposit, southwestern Guizhou Province, China

The Shuiyindong deposit is one of the largest (more than 100 tonnes of Au) and highest grade (more than 7×10-6-10×10-6), strata-bound Carlintype gold deposits in southwestern Guizhou Province, China. The deposit is controlled by both structure and favorable lithology. It is situated near the axis of the striking Huijiabao anticline and is hosted in bioclastic limestone of the Permian Longtan Formation. Gold mineralization occurred under low temperature with Th of 220℃± and is closely associated with decarbonation, silicification, sulfidation and dolomitization. The deposit has a characteristic elemental assemblage of Au-As-Hg-Tl. Studies of geochemistry and isotope compositions indicated that the ore-bearing materials and fluids of the gold deposit mainly originated from a plutonic source, and possess a mixing feature with the strata matter during transportation from mantle to crust. Fluid inclusions in vein quartz from the gold deposit are rich in volatile flux, indicating that metallogenic fluid is an overpres-sured one. The activity and geothermal state of the Earth's crust in the long period of time are favorable for the formation of overpressured fluids in a large area, and extensive structures would drive the fluids into ore-forming sys-tem and make gold deposits formed. The complexity of structural movement in the upper crust of southwestern Guizhou Province resulted in complicated gold mineralization. Through metallogenic prognosis and exploration, the proven reserves of the deposit increased by tens of tonnes of Au and the deposit has become a super-large strata-bound Carlin-type gold deposit.

Geochemical characteristics and metallogenesis of Carlin-type gold deposits in the Sandu-Danzhai metallogenic zone,Guizhou Province,China

Geochemical studies of the Paiting and Miaolong Carlin-type gold deposits in the Sandu-Danzhai metal-logenic zone,Guizhou Province,have shown that the mineralized-altered rocks show LREE-enrichment patterns,generally displaying negative Eu anomalies(δEu=0.51?0.97) and unobvious negative Ce anomalies(δCe=0.86?0.99).Calcite and fluorite in relation with metallogenesis show MREE-enrichment patterns,generally displaying rather weak negative Eu anomalies(δEu=0.74?0.93) and weak negative Ce(δCe=0.70?0.98) anomalies.The δ13CPDB values of carbon in calcite are-1.61‰?-5.82‰,the δ18OSMOW values of oxygen are 13.97‰?19.24‰,and the δ34SCDT values of sulfur in stibnite are 17.72‰?21.68‰.In regard to δD and δ18O,ore-forming fluids pos-sess the characteristics of metamorphic water.The process of metallogenesis of the Carlin-type gold deposits is con-trolled by the Yanshanian tectonic activities.The Yanshanian movement promoted the migration and mobilization of metamorphic fluids in the extensively developed medium-to high-grade metamorphic rocks in this region,carrying primarily enriched gold and associated elements such as Hg,As,and Sb in the Sinian metamorphosed black shales and Lower Cambrian black shales.The ore-forming fluids found their way into a suitable metallogenic environment along the fault zone,followed by gold precipitation to form gold deposits.

A study on the genetic relations between Permian Longtan Formation coal series strata and Carlin-type gold deposits,southwestern Guizhou Province,China

A large number of the Carlin-type gold deposits occur in the Longtan Formation in southwestern Guizhou Province.The Long-tan Formation contains abundant basalt,tuff and siliceous rocks.All rocks of the Longtan Formation are enriched in gold,which were deposited in a limited platform environment in the transition zone from marine to continental.The process of sedimentation was accompanied by the eruption of Emeishan basalt and hydrothermal deposition controlled by co-sedimentary submarine deep faults in the west,which led to the formation of a peculiar gold-bearing formation with coal series strata.This formation controlled the occurrence of the Carlin-type gold deposits in southwestern Guizhou Province.In response to the remobilization of the Emei mantle plume during the Yanshanian period,As,Au and other ore-forming materials were continuously extracted by deeply circulating waters from the Emeishan basalt and coal seams,thereafter forming ore-forming hydrothermal solutions.When these elements were transported in the coal seams,large amounts of As,Au and other elements were enriched in pyrite within the coal seams,thus forming high-As coal and Carlin-type gold deposits in the Longtan Formation coal series strata.

Geochemical Tracing of Ore-forming Material Sources of Carlin-type Gold Deposits in the Yunnan-Guizhou-Guangxi Triangle Area --A Case Study of the Application of the Combined Silicon Isotopes Geochemistry and Siliceous Cathodoluminescence Analysis

Abstract This paper deals with characteristics of silicon isotope compositions and siliceous cathodoluminescence of host rocks, ores and hydrothermal silicified quartz of the Carlin-type ore deposits in the Yunnan-Guizhou-Guangxi triangle area. The study shows that primary silicified quartz is nonluminescent but quartz in host rocks and secondary silicified quartz are luminescent by the action of cathode rays. Correspondingly, silicon isotope compositions of host rocks, ores and hydro6thermal quartz veins are clearly distinguished. In strata from the Middle Triassic to the “Dachang” host bed, δ30Si of the host rocks ranges from 0.0% ?0.3%, while that of primary ore-forming silicified fluids from ?0.1% to ?0.4%; in the Upper Permian and Lower Carboniferous strata and Indosinian diabase host beds, δ30Si of the host rocks is from ?0.1% to ?0.2% and that of the primary silicified quartz veins from 0.3 % ?0.5 %. This pattern demonstrates the following geochemical mineralization process, primary ore-forming siliceous fluids migrated upwards quickly along the main passages of deep-seated faults from mantle to crust and entered secondary faults where gold deposits were eventually formed as a result of permeation and replacement of the siliceous ore-forming fluids into different ore-bearing strata. This gives important evidence for the fact that ore-forming fluids of this type of gold deposits were mainly derived from upper mantle differentiation and shows good prospects for deep gold deposits and geochemical background for large and superlarge gold deposits.

A New Genetic Type of Gold Deposits-Meso-Epithermal Carbonate-Type Gold Deposits as Exemplified by the Baguamiao Superlarge Gold Deposit

Gold deposits of the meso-epithermal carbonate type were first proposed based on the study of the Baguamiao gold deposit.This new type of gold deposits has many unique characteristics as follows:(1)Obviously strata-bound.The gold deposits are hosted in Middle Devonian turbidite formations;(2)Structrually controlled.Struc-ture is an important factor leading to metallogenesis of this type of gold deposits.The shape and distribution of orebodies are controlled by byittle-ductile shear zones;(3)Multi-stage wall-rock alteration.According to the characteristics of mineral assemblage,gold mineralization can be classified into three stages in association with various wall-rock al-terations.Wall-rock alterations closely genetically related to the gold mineralization are ankerization ,silicification,pyrrhotization and pyritization ;(4)Mineral compositions of the orebodies are mainly pyrrhotite,pyrite,marcasitolite,chalcopyrite,quartz,ankerite,and sericite.Gold mineralization is associated closely in space and time with iron sulfides;(5)Rare elements and REE in ores are low in contents relative to those of the crust.Au content varies from 1.91g/t to 11.15g/t ,averaging 5.5g/t;(6)Studies of sulfur,hydrogen,oxygen and carbon isotopes in main gangue minerals (quartz and ankerite)indicate that fluids and ore-forming materials came from deep-seated sources;(7)Three types of inclusions are recognized in terms of their composition and the vapor amounts of inclusions.The homogenization temperatures of inclusions range from 210℃to 310℃,averaging 230℃,showing that this type of gold deposits belongs to the meso-epithermal type;(8)Metallogenic age of this type of gold deposits is similar to that of the collision between the Yangtze Plate and the North China Plate,indicating that gold deposits of this type are genetically related to continental-margin plate activity.

Geochemical Characteristics of the Jinjiazhuang Ultrabasic Rock-Type Gold Deposit in Chicheng County, Hebei Province

The Jinjiazhuang gold deposit occurs in the Zhangjiakou gold field, Northwest Hebei. The ore bodies are mostly hosted in Xiaozhangjiakou ultrabasic rocks dominated by diopsidite. Electron microprobe analyses indicate that the deposit is characterized by the enrichment of some platinum group elements in principal metallic minerals such as chalcopyrite, galena, sphalerite and pyrite, and the presence of millerite. Stable isotope studies show that carbon, sulfur and most of the metallogenic elements were probably derived largely from the host Xiaozhangjiakou ultrabasic rocks and that it is possible that the ore\|forming fluid was predominated by meteoric water.

Trace Elements in Fluid Inclusions in the Carlin-Type Gold Deposits, Southwestern Guizhou Province

Fluid inclusions in quartz from the Lannigou and Yata Carlin\|type gold deposits in southwestern Guizhou were analyzed by inductively coupled plasma\|mass spectrometry for their trace elements (Co, Ni, Cu, Pb, Zn, Pt, etc.). The results show that quartz fluid inclusions entrapped at different ore\|forming stages contain higher Co, Ni, Cu, Pb and Zn. It has been found for the first time that the ore\|forming fluids responsible for the Carlin\|type gold deposits are rich in Pt. From this it can be concluded that basic volcanic rocks seem to be one of the important sources of ore\|forming materials for the Carlin\|type gold deposits.

Geochemistry of Main Types of Gold Deposits in Shear Zones, China

Shear zone hosted gold deposits in China can be divided into four types: ductile,brittle ductile,ductile brittle and brittle, of which the ductile and brittle types are the basic ones. All these types of gold deposits have their own geochemical characteristics. The Hetai gold deposit in Guangdong Province, for example, is a mylonite type gold deposit in a ductile shear zone. With increasing mylonitization, obvious changes took place in trace elements in minerals and rocks, enriching gold and mineralizing elements. The S and Pb isotope data indicated that the ore forming materials were derived from the strata. Hydrogen and oxygen isotopic and fluid inclusion studies also implied that the ore forming fluid was much closer to meteoric water from the early to the late ore forming stage. The Linglong gold deposit, Shangdong Province, is a quartz\|type gold deposit in a brittle shear zone. Changes in rocks, minerals and trace elements occurred in the process of formation of gold quartz veins, and the analytical results of S, Pb, H and O isotopes showed that ore deposition is connected not only with the Jiaodong Group, but also with anatexic granites.

Carlin-Type Gold Deposits in Qinling and Some Related Problems

The sediment hosted disseminated gold deposits in the Qinling region are of sedimentation slight metamorphic origin superimposed by hydrothermal reworking at moderate low temperatures and are well comparable with the typical Carlin gold deposits in the United States. In view of the confusing concept concerning the \!sediment hosted" and \!Carlin type" gold deposits, the authors propose that the term \!sediment hosted gold deposit" should be used in a broad sense which encompasses at least the four subtypes, i.e., the Carlin type, the metamorphic fine clastic type, the hydrothermal sedimentary type and the vein type. In other words, the \!Carlin type" should not be used as a synonym for \!sediment hosted" but is recommended as a subtype under the general category of \!sediment hosted gold deposits".

THE GEOLOGY AND GENESIS OF THE Q1YUGOU EXPLOSIVE BRECCIA TYPE GOLD DEPOSITS,HENAN PROVINCE

The Qiyugou explosive breccia type gold deposits of northwestern Songxian, Henan Province is situated at the East Qinling, on the southern margin of the North China Platform.The basement rocks are the Archean Taihua Group gneisses which were overlaid by the Proterozoic Xionger Group metaandesites. NW-and NE-trending folds and fractures are well developed. Nlagmatism of the Mid-Late Yanshan Epoch led to the formation of the Huashan granite batholith and a variety of acid/alkali dykes, meanwhile more than thirty explosive breccia bodies had been brought about. The most important deposit type is the explosive breccia type represented by the Qiyugou deposit, meanwhile there are structure fracture altered rock type,the goldbearing quartz vein type, as well as porphyry-breccia type. All these types are the terminal products of the evolution and differentiation of the syntectic magma originated from lower crust or upper mantle. They are controlled by a unified structural pattern occurred in the same

ORE FLUID GEOCHEMISTRY OF THE JINLONGSHAN CARLIN-TYPE GOLD ORE BELT IN SHAANXI PROVINCE, CHINA

The Jinlongshan gold ore belt in southern Shaanxi Province contains a number of Carlin-type gold deposits in the Qinling collisional orogenic belt. Their fluid inclusions are of the Na-Cl- type. From the main metallogenic stage to later stages, the total quantity of anions and cations, temperature and deoxidation parameter (R) for fluid inclusions all gradually decreased, suggesting the gradual intensification of fluid oxidation, the reduction of metallogenic depth and the input of meteoric water and organic components. The deposits were formed during crustal uplifting and hence had similar tectonic settings to orogenic gold deposits. The CO-2 contents and CO-2/H-2O values of the ore fluid increased from early to late stages, and the wall-rock alteration is represented by decarbonation, which is inconsistent with the characteristics of orogenic gold deposits. It is also discovered that Na, K, SO{2-}-4, Cl- and the total amounts of anions and cations in the inclusions in quartz are higher than those in the coexisting calcite. The H, O and C isotope ratios indicate that the ore fluid was sourced from meteoric water and metamorphic devolatilisation of the sedimentary rocks that host the ores. The high background {δ{}{18}O} and {δ{}{13}C} values of wall rocks resulted in high {δ{}{18}O} and {δ{}{13}C} values of ore fluid and also high {δ{}{18}O} and {δ{}{13}C} values of hydrothermal minerals such as quartz and carbonate. The carbon in ore fluid stemmed largely from the hosting strata. The {δ{}{18}O} and {δ{}{13}C} values of Fe-calcite and the δD values of fluid inclusions are lower than those of calcite and quartz. In terms of the theory of coordination chemistry, all these differences can be ascribed to water-rock interaction in the same fluid system, instead, to the multi-source of ore fluid.

U-Pb SHRIMP Dating of Zircon from Quartz Veins of the Yangshan Gold Deposit in Gansu Province and Its Geological Significance

The Yangshan gold deposit is a super-large fine-grained disseminated gold deposit located in southern Gansu Province. Its metallogenic age has been determined by using the cathodoluminescence image and ion probe U-Pb dating techniques. It is found that zircons from quartz veinlet of the fine-grained disseminated gold ore show characters of magmatic origin with prism idiomorphism, oscillatory zoning and dominant Th/U ratios of 0.5-1.5. Three main populations of zircons are obtained, giving average 206Pb/238U ages of 197.6±1.7 Ma, 126.9±3.2 Ma and 51.2±1.3 Ma respectively. The first age corresponds to the K-Ar age of the plagiogranite dike, while the latter two ages indicate that buried Cretaceous and Tertiary intrusives exist in the orefield, suggesting that the Yangshan gold deposit was genetically related to the three magmatic hydrothermal activities. By contrast, zircons from coarse gold-bearing quartz vein in the mining area are much older than the host rock, indicating that the vein was formed earlier and was not contaminated by later magmatic fluids. It is concluded that the coupling of multiperiodic hydrothermal activities in the mining area has contributed a lot to mineralization of the Yangshan gold deposit.

Experimental Study on Gold Dissolution from Hosting Minerals of the Hadamengou Gold Deposit and the Implications

The Hadamengou gold deposit is located in western part of the northern margin of the North China craton. It is a hydrothermal deposit related to alkaline magmatism. Dissolution of Au, Fe from pyrite and iron oxide （including magnetite and hematite） individual minerals in the three main types of ore shows： in iron oxides （magnetite and hematite）, Au and Fe were dissolved simultaneously and their solubilities are positively correlated, which means Au is mainly chemical-bonded （lattice gold） and/or colloidal-adsorbed in iron oxides; while in pyrite, on the contrary, Au dissolution obviously lags behind Fe and the solubility of Au shows negative relationship with that of Fe, which indicates Au is mainly hosted as grains of elemental gold （or native gold） within pyrite. Previous studies revealed that the Hadamengou gold deposit is characterized by intensive K-feldspathization and holds high content of iron oxides occasionally replaced by sulfides, which was caused by oxidizing K-enriched alkaline fluids under a stretching geodynamic setting. These geological features, together with the high Au-content in iron oxides, comparable with that of the Olympic Dam deposit in South Australia, suggest that this deposit is the first example of iron oxide-type gold deposits in China.