Mineralogical study and significance of the basalt-hosted Carlin-type Au deposits in southwestern Guizhou Province,China

The Jiadi and Damaidi gold deposits in southwest Guizhou Province are the largest basalt-hosted Carlintype gold deposits recently discovered in China.This study uses the Tescan Integrated Mineral Analyzer,supported by detailed field investigations,regional geological data,and extensive sample collections,including mineralized ore,altered wall rock,and unaltered basalt samples,for orebearing and geochemical analyses.Comparative analysis between altered and unaltered basalt samples revealed a mineral assemblage of sericite,quartz,and pyrite.This mineral composition forms through the hydrothermal alteration of unaltered basalt,originally containing feldspar,pyroxene,and ilmenite.The wall rock primarily features sericite,quartz,and hematite.During the alteration process,major,trace,and rare earth elements notably migrate.In the Jiadi deposit,K_(2)O,Rb,Au,and REE significantly increase,while Na_(2)O,CaO,MgO,and MnO decrease.SiO_(2),Al_(2)O_(3),and Fe_(2)O_(3)levels remain relatively stable.In the Damaidi deposit,K_(2)O,Rb,and Au enrich,contrasting with the depletion of Na_(2)O,CaO,MgO,and MnO,while SiO_(2),Fe_(2)O_(3),Al_(2)O_(3),TiO_(2),and REE show no significant changes.In the wall rock,TiO_(2),Al_(2)O_(3),K_(2)O,and REE increase,while Na_(2)O,CaO,MgO,and MnO decrease;SiO_(2)and Fe_(2)O_(3)content remains unchanged.The mineralization process likely originated from mid-to low-temperature,reductive magmatic hydrothermal fluids rich in CO_(2),CH_(4),N_(2),H^(+),S^(2-),HS^(-),H_(3)AsO_(3),and[Au(HS_(2)]^(-).These fluids migrated to tectonically weak zones in the Lianhuashan area,where Emeishan basalts are present.They reacted with Fe-bearing minerals in the basalt,such as ferro-hornblende and ilmenite,forming pyrite,arsenic-bearing pyrite,and arsenopyrite,thus enriching Au in these minerals.Additionally,K^(+)and H^(+)in the fluid reacted with plagioclase in the basalt,forming sericite and quartz.As the fluid entered the wall rock from structural weak zones,its oxidation increased,leading to the complete or partial reaction of Fe-bearing minerals in the wall rock,resulting in the formation of hematite or magnetite.This mineralization process is similar to that observed in carbonate-hosted Carlin-type gold deposits in southwest Guizhou,with the primary distinction being the iron source.In carbonate deposits,iron originates from ferridolomite within the wall rock,while in basalt-hosted deposits,it derives from ferripyroxene and ilmenite.

A new method of searching for concealed Au deposits by using the spectrum of arid desert plant species

With the increase of exploration depth,it is more and more difficult to find Au deposits.Due to the limitation of time and cost,traditional geological exploration methods are becoming increasingly difficult to be effectively applied.Thus,new methods and ideas are urgently needed.This study assessed the feasibility and effectiveness of using hyperspectral technology to prospect for hidden Au deposits.For this purpose,48 plant(Seriphidium terrae-albae)and soil(aeolian gravel desert soil)samples were first collected along a sampling line that traverses an Au mineralization alteration zone(Aketasi mining region in an arid region of China)and were used to obtain soil Au contents by a chemical analysis method and the reflectance spectra of plants obtained with an Analytical Spectral Device(ASD)FieldSpec3 spectrometer.Then,the corresponding relationship between the soil Au content anomaly and concealed Au deposits was investigated.Additionally,the characteristic bands were selected from plant spectra using four different methods,namely,genetic algorithm(GA),stepwise regression analysis(STE),competitive adaptive reweighted sampling(CARS),and correlation coefficient method(CC),and were then input into the partial least squares(PLS)method to construct a model for estimating the soil Au content.Finally,the quantitative relationship between the soil Au content and the 15 different plant transformation spectra was established using the PLS method.The results were compared with those of a model based on the full spectrum.The results obtained in this study indicate that the location of concealed Au deposits can be predicted based on soil geochemical anomaly information,and it is feasible and effective to use the full plant spectrum and PLS method to estimate the Au content in the soil.The cross-validated coefficient of determination(R2)and the ratio of the performance to deviation(RPD)between the predicted value and the measured value reached the maximum of 0.8218 and 2.37,respectively,with a minimum value of 6.56μg/kg for the root-mean-squared error(RMSE)in the full spectrum model.However,in the process of modeling,it is crucial to select the appropriate transformation spectrum as the input parameter for the PLS method.Compared with the GA,STE,and CC methods,CARS was the superior characteristic band screening method based on the accuracy and complexity of the model.When modeling with characteristic bands,the highest accuracy,R2 of 0.8016,RMSE of 7.07μg/kg,and RPD of 2.20 were obtained when 56 characteristic bands were selected from the transformed spectra(1/lnR)'(where it represents the first derivative of the reciprocal of the logarithmic spectrum)of sampled plants using the CARS method and were input into the PLS method to construct an inversion model of the Au content in the soil.Thus,characteristic bands can replace the full spectrum when constructing a model for estimating the soil Au content.Finally,this study proposes a method of using plant spectra to find concealed Au deposits,which may have promising application prospects because of its simplicity and rapidity.

Characteristics and Genesis of Fine-Clastic Rock-Type Au Deposits in the Liaodong Rift

Gold deposits occurring in the Liaodong rift are located in interlayered carbonate rocks and fine-clastic rocks, belonging to the middle and upper parts of the lower Proterozoic. Compared with the Carlin-type Au deposits abroad and gold deposits in Yunnan-Guizhou-Guangxi, Qinling and western Sichuan Province, they are similar in many respects. This paper discusses the geological features of ore-bearing formations and ore-filling structures and metallogenetic characteristics. Through the discussion on the sources of ores, heat and water, it points out that the Au deposits belong to vadose reworked hydrothermal deposits. This conforms to the principle of “mineralization in the neighbouring areas”, i.e., the deposits are formed in nearby ore-bearing layers, and the latest hydrothermal event was the main factor in forming the Au deposits.

Geology and mineralization of the Dongping supergiant alkalic-hosted Au-Te deposit(>100 t Au)in Northern Hebei Province,China:A review

The Dongping deposit is the largest alkalic-hosted gold deposit in China containing>100 t of Au.This paper presents a new understanding for Dongping ore system,based on the previous studies.The mineralization originally occurred at 400-380 Ma,simultaneous with emplacement of the Shuiquangou alkaline complex,and was overprinted by the hydrothermal activity in the Yanshanian.Isotope compositions of ores indicate metals of the deposit are mainly provided by the Shuiquangou complex.Ore-forming fluids are characterized by increasing oxygen fugacity and decreasing sulfur fugacity,while tellurium fugacity increased in the Stage II-2 and decreased in Stage II-3.These systematic changes are closely related to the processes of mineral precipitation and fluid evolution.Sulfide precipitation from Stage Ⅰ to Stage Ⅱ was triggered by fluid boiling,which leads to the precipitation of Pb-Bi-Te,due to decrement of sulfur fugacity.Condensation of gas phase containing high concentration of H_2Te leads to precipitation of Te-Au-Ag minerals and native tellurium.Based on these hypotheses,this paper present a polyphase metallogenic model as follow.During the Devonian,fluids were released from alkaline magmas,which carried ore-forming materials form the surrounding rocks and precipitate the early ores.During the Jurassic-Cretaceous,fluorine-rich fluids exsolved from highly factionated Shangshuiquan granite,which extracted and concentrated Au from the Shuiquangou complex and the Sanggan Group metamorphic rocks,and finally formed the Dongping gold deposit.

^40Ar/^39Ar and Rb-Sr Ages of the Tiegelongnan Porphyry Cu-(Au)Deposit in the Bangong Co-Nujiang Metallogenic Belt of Tibet,China:Implication for Generation of Super-Large Deposit

The Tiegelongnan deposit is a newly discovered super-large porphyry-epithermal Cu-（Au） deposit in the western part of the Bangong Co-Nujiang metallogenic belt, Tibet（China）. Field geology and geochronology indicate that the porphyry mineralization was closely related to the Early Cretaceous intermediate-felsic intrusions（ca. 123–120 Ma）. Various epithermal ore and gangue mineral types were discovered in the middle-shallow part of the orebody, indicating the presence of epithermal mineralization at Tiegelongnan. Potassic, propylitic, phyllic and advanced argillic alteration zones were identified. 40Ar/39Ar dating of hydrothermal biotite（potassic zone）, sericite（phyllic zone）, and alunite（advanced argillic zone） in/around the ore-bearing granodiorite porphyry yielded 121.1±0.6 Ma（1σ）, 120.8±0.7 Ma（1σ） and 117.9±1.6 Ma（1σ）, respectively. Five hydrothermal mineralization stages were identified, of which the Stage IV pyrite was Rb-Sr dated to be 117.5±1.8 Ma（2σ）, representing the end of epithermal mineralization. Field geology and geochronology suggest that both the epithermal and porphyry mineralization belong to the same magmatic-hydrothermal system. The Tiegelongnan super-large Cu-（Au） deposit may have undergone a prolonged magmatichydrothermal evolution, with the major mineralization event occurring at ca.120–117Ma.

He–Ar Isotopic Tracing of Pyrite from Ore-forming Fluids of the Sanshandao Au Deposit, Jiaodong Area

The Sanshandao Au deposit is located in the famous Sanshandao metallogenic belt,Jiaodong area.To date,accumulative Au resources of 1000 t have been identified from the belt.Sanshandao is a world-class gold deposit with Au mineralization hosted in Early Cretaceous Guojialing-type granites.Thus,studies on the genesis and ore-forming element sources of the Sanshandao Au deposit are crucial.He and Ar isotopic analyses of fluid inclusions from pyrite(the carrier of Au)indicate that the fluid inclusions have 3 He/4 He=0.043–0.21 Ra with an average of 0.096 Ra and 40 Ar/36 Ar=488–664 with an average of 570.8.These values represent the initial He and Ar isotopic compositions of ore-forming fluids for trapped fluid inclusions.The comparison of H–O isotopic characteristics combined with deposit geology and wall rock alteration reveals that the ore-forming fluids of the Sanshandao Au deposit show mixed crust–mantle origin characteristics,and they mainly comprise crust-derived fluid mixed with minor mantle-derived fluid and meteoric water during the uprising process.The ore-forming elements were generally sourced from pre-Cambrian meta-basement rocks formed by Mesozoic reactivation and mixed with minor shallow crustal and mantle components.

Gold and antimony metallogenic relations and ore-forming process of Qinglong Sb(Au) deposit in Youjiang basin, SW China: Sulfide trace elements and sulfur isotopes

In the northwestern margin of the Youjiang basin(NWYB)in SW China,many Carlin-like gold deposits are highly antimony(Sb)-rich,and many vein-type Sb deposits contain much Au.These deposits have similar ages,host rocks,ore-forming temperatures,ore-related alterations and ore mineral assemblages,but the Au and Sb metallogenic relations and their ore-forming process remain enigmatic.Here we investigate the large Qinglong Sb deposit in the NWYB,which has extensive sub-economic Au mineralization,and present a new metallogenic model based on in-situ trace elements(EPMA and LA-ICP-MS)and sulfur isotopes(NanoSIMS and fs-LA-MC-ICPMS)of the ore sulfides.At Qinglong,economic Sb ores contain coarse-grained stibnite,jasperoid quartz and fluorite,whilst the sub-economic Au–Sb ores comprise dominantly veined quartz,arsenian pyrite and fine-grained stibnite.Three generations of ore-related pyrite(Py1,Py2 and Py3)and two generations of stibnite(Stb1 and Stb2)are identified based on their texture,chemistry,and sulfur isotopes.The pre-ore Py1 is characterized by the lower ore element(Au,As,Sb,Cu and Ag)contents(mostly below the LA-ICP-MS detection limit)and Co/Ni ratios(average 0.31)than the ore-stage pyrites(Py2 and Py3),implying a sedimentary/diagenetic origin.The Py2 and Py3 have elevated ore element abundance(maximum As=6500 ppm,Au=22 ppm,Sb=6300 ppm,Cu=951 ppm,Ag=77 ppm)and Co/Ni ratios(average 1.84),and have positive As vs.Au–Sb–Cu–Ag correlations.Early-ore Stb1 has lower As(0.12–0.30 wt.%)than late-ore Stb2(0.91–1.20 wt.%).These features show that the progressive As enrichment in ore sulfides is accompanied by increasing Au,Sb,Cu and Ag with the hydrothermal evolution,thereby making As a good proxy for Au.As-rich,As-poor and As-free zones are identified via NanoSIMS mapping of the Au-bearing pyrite.The As-rich zones in the Qinglong Au-bearing pyrites(Py2 and Py3)and ore stibnites(Stb1 and Stb2)have narrowδ^(34)SH_(2)S ranges(-8.9‰to +4.1‰,average-3.1‰)and-2.9‰to +6.9‰,average + 1.3‰),respectively,indicating that the Au-rich and Sb-rich fluids may have had the same sulfur source.Published in-situ sulfur isotopic data of pyrite As-rich zones from other Carlin-like Au deposits(Shuiyindong,Taipingdong,Nayang,Getang and Lianhuashan)in the NWYB have similar ore-fluidδSH_(2)S values(-4.5‰to +6.7‰,average-0.6‰)to those of Qinglong.Therefore,we infer that the sulfur of both Au and Sb mineralization was derived from the same magmatic-related source(0±5‰)in the NWYB.Moreover,the core of pyrites(Py1)has variable S isotope fractionation(-18.9‰to +18.1‰,mostly +3‰to +12‰),suggesting that the higher-^(34)S H_(2)S was produced by bacterial sulfate reduction(BSR).The hydrothermal pyrite(Py2 and Py3)δ^(34)S values gradually decrease with increasing As concentrations,and ultimately,within the restricted range(-5‰to +5‰)in As-rich zones.This variation implies that the As-rich pyrite was formed through ongoing interactions of the magmatic-hydrothermal fluid with pre-existing sedimentary pyrites,causing the progressive decreasing δ^(34)S values with As content increase,Hence,the fluid/mineral interaction may have generated the observed variation in δ^(34)S and As contents.Overall,comparing the Au and Sb deposits in the NWYB,we favor a magmatic-related source for the Au–Sb–As-rich fluids,but the Au-and Sb-ore fluids were likely evolved at separate stages in the ore-forming system.

Geology, geochronology and geochemistry of large Duobaoshan Cu-Mo-Au orefield in NE China: Magma genesis and regional tectonic implications

Duobaoshan is the largest porphyry-related Cu-Mo-Au orefield in northeastern(NE)Asia,and hosts a number of large-medium porphyry Cu(PCDs),epithermal Au and Fe-Cu skarn deposits.Formation ages of these deposits,from the oldest(Ordovician)to youngest(Jurassic),have spanned across over 300 Ma.No similar orefields of such size and geological complexity are found in NE Asia,which reflects its metallogenic uniqueness in forming and preserving porphyry-related deposits.In this study,we explore the actual number and timing of magmatic/mineralization phases,their respective magma genesis,fertility,and regional tectonic connection,together with the preservation of PCDs.We present new data on the magmatic/mineralization ages(LA-ICP-MS zircon U-Pb,pyrite and molybdenite Re-Os dating),whole-rock geochemistry,and zircon trace element compositions on four representative deposits in the Duobaoshan orefield,i.e.,Duobaoshan PCD,Tongshan PCD,Sankuanggou Fe-Cu skarn,and Zhengguang epithermal Au deposits,and compiled published ones from these and other mineral occurrences in the orefield.In terms of geochronology,we have newly summarized seven magmatic phases in the orefield:(1)Middle-Late Cambrian(506-491 Ma),(2)Early and Middle Ordovician(485-471 Ma and~462 Ma),(3)Late Ordovician(450-447 Ma),(4)Early Carboniferous and Late-Carboniferous to Early Permian(351-345 and 323-291 Ma),(5)Middle-Late Triassic(244-223 Ma),(6)Early-Middle and Late Jurassic(178-168 Ma and~150 Ma),and(7)Early Cretaceous(~112 Ma).Three of these seven major magmatic phases were coeval with ore formation,including(1)Early Ordovician(485-473 Ma)porphyry-type Cu-Mo-(Au),(2)Early-Middle Triassic(246-229 Ma)porphyry-related epithermal Au-(Cu-Mo),and(3)Early Jurassic(177-173 Ma)Fe-Cu skarn mineralization.Some deposits in the orefield,notably Tongshan and Zhengguang,were likely formed by more than one mineralization events.In terms of geochemistry,ore-causative granitoids in the orefield exhibit adakite-like or adakite-normal arc transitional signatures,but those forming the porphyry-/epithermal-type Cu-Mo-Au mineralization are largely confined to the former.The varying but high Sr/Y,Sm/Yb and La/Yb ratios suggest that the ore-forming magmas were mainly crustal sourced and formed at different depths(clinopyroxene-/amphibole-/garnet-stability fields).The adakite-like suites may have formed by partial melting of the thickened lower crust at 35-40 km(for the Early Ordovician arc)and>40 km(for the Middle-Late Triassic arc)depths.The Early Jurassic Fe-Cu skarn orecausative granitoids show an adakitic-normal arc transitional geochemical affinity.These granitoids were likely formed by partial melting of the juvenile lower crust(35-40 km depth),and subsequently modified by assimilation and fractional crystallization(AFC)processes.In light of the geological,geochronological and geochemical information,we proposed the following tectonometallogenic model for the Duobaoshan orefield.The Ordovician Duobaoshan may have been in a continental arc setting during the subduction of the Paleo-Asian Ocean,and formed the porphyry-related deposits at Duobaoshan,Tongshan and Zhengguang.Subduction may have ceased in the latest Ordovician,and the regional tectonics passed into long subsidence and extension till the latest Carboniferous.This extensional tectonic regime and the Silurian terrestrial-shallow marine sedimentation had likely buried and preserved the Ordovician Duobaoshan magmatic-hydrothermal system.The south-dipping Mongol-Okhotsk Ocean subduction from north of the orefield had generated the Middle-Late Triassic continental arc magmatism and the associated Tongshan PCD and Zhengguang epithermal Au mineralization(which superimposed on the Ordovician PCD system).The Middle Jurassic closure of Mongol-Okhotsk Ocean in the northwestern Amuria block(Erguna terrane),and the accompanying Siberia-Amuria collision,may have placed the Paleo-Pacific subduction system in NE China(including the orefield)under compression,and formed the granodiorite-tonalite and Fe-Cu skarn deposits at Sankuanggou and Xiaoduobaoshan.From the Middle Jurassic,the consecutive accretion of Paleo-Pacific arc terranes(e.g.,Sikhote-Alin and Nadanhada)onto the NE Asian continental margin may have gradually distant the Duobaoshan orefield from the subduction front,and consequently arc-type magmatism and the related mineralization faded.The minor Late Jurassic and Cretaceous unmineralized magmatism in the orefield may have triggered mainly by the far-field extension led by the post-collisional(Siberia-Amuria)gravitational collapse and/or Paleo-Pacific backarc-basin opening.

Geochemistry, Geochronology and Lu-Hf Isotopes of Peraluminous Granitic Porphyry from the Walegen Au Deposit, West Qinling Terrane

Walegen Au deposit is closely correlated with granitic intrusions of Triassic age, which are composed of granite and quartz porphyries. Both granite porphyry and quartz porphyry consist of quartz, feldspar and muscovite as primary minerals. WeaMy peraluminous granite porphyry （A/ CNK=1.10-1.15） is enriched in LREE, depleted in HREE with Nb-Ta-Ti anomalies, and displays subduction-related geochemistry. Quartz porphyry is strongly peraluminous （A/CNK=1.64-2.81） with highly evolved components, characterized by lower TiO2, REE contents, Mg#, K/Rb, Nb/Ta, Zr/Hf ratios and higher Rb/Sr ratios than the granite porphyry. REE patterns of quartz porphyry exhibit lanthanide tetrad effect, resulting from mineral fractionation or participation of fluids with enriched F and CI. LA- ICP-MS zircon U-Pb dating indicates quartz porphyry formed at 233±3 Ma. The ages of relict zircons from Triassic magmatic rocks match well with the detrital zircons from regional area. In addition, εHf（t） values of Triassic magmatic zircons from the granite and quartz porphyries are -14.2 to -9.1 （with an exception of ＋4.1） and -10.8 to -8.6 respectively, indicating a crustal-dominant source. Regionally, numerous Middle Triassic granitoids were previously reported to be formed under the consumption of Paleotethyan Ocean. These facts indicate that the granitic porphyries from Walegen Au deposit may have been formed in the processes of the closing of Paleotethyan Ocean, which could correlate with the arc-related magmatism in the Kunlun orogen to the west and the Qinling orogen to the east.

Petrogenesis and Tectonic Significance of the Three-Period Porphyries from the Daruoluolong Cu(Au) Deposit, Tibet, China

Objective The Daruoluolong deposit is the first high-grade Cu(Au)deposit discovered in the middle section of the Bangonghu-Nujiang(herein after referred to as Ban-Nu)metallogenic belt,which has not been documented about previously.This deposit is located in Shuanghu County of northern Tibet,and its geotectonic position belongs to the

Hydrothermal evolution and source of metallogenic materials of Beiya Au polymetallic deposit,western Yunnan,China

The Beiya porphyry-skarn gold-polymetallic deposit is one of the largest gold deposits in China and it also contains significant amounts of silver and base metals.The ore-bearing monzonitic granite porphyry occurs as a stock,of which the skarn type gold-copper-iron ore bodies are controlled by the contact zone between alkali-rich monzonitic granite porphyry and the limestone,and the gold-silver polymetallic mineralization is controlled by interlayer structure.Alteration and mineralization occur around the intrusion and exterior of monzonitic granite porphyry.Ore mineral formation sequence is as follows:skarn minerals→magnetite→pyrite→chalcopyrite/bornite+pyrite+gold→pyrite+galena+gold(silver).Petrographic studies of fluid inclusions indicate that the following types of inclusions exist in the pre-mineralization quartz-pyrite stage:gas-liquid two-phase inclusions(L-type),three-phase inclusions with daughter minerals(D-type)and gas-rich inclusions(V-type).The colorless transparent quartz in the main gold-chalcopyrite-pyrite stage mainly consists of L-type and V-type inclusions,whereas the inclusions in the late gold-silver-galena stage are mainly L-type.The evolution of ore-forming fluids shows a trend from high temperature,high salinity to medium-low temperature and low salinity.Medium-low density fluids play a dominant role in mineral component migration and transportation.Fluid cooling and boiling are the main mechanisms of gold-copper precipitation,while the involvement of atmospheric water and pH reduction are the main mechanisms of gold-silver polymetallic precipitation.The fluids in the quartz-pyrite stage before mineralization and the main gold-chalcopyrite-pyrite stage are dominated by magmatic water,while in the gold-silver-galena stage the fluids are dominated by atmospheric water.Isotope tracers show that S and Pb are mainly derived from monzonitic granite porphyry,not from limestone of the Beiya Formation.

Hydrous Juvenile Lower Crust at the Western Yangtze Craton Margin as the Main Source of the Beiya Porphyry-skarn Au Deposit

The Beiya porphyry-skarn Au deposit is one of the largest gold deposits in China,temporally and spatially associated with Eocene intrusions in a post-collisional setting in western Yunnan,China.In this study,we report new whole-rock geochemistry,Sr-Nd isotope,zircon U-Pb geochronology and in situ zircon Hf-O isotopes of quartz-monzonite and biotite-monzonite porphyries from the Beiya deposit.The porphyry-skarn mineralization at the Beiya deposit is mainly associated with the quartz monzonite porphyry(35.8±0.6 Ma),while the biotite-monzonite porphyry(34.3±0.5 Ma)represents a post-mineralization intrusion crosscutting the main orebodies and the quartz-monzonite porphyry.Both intrusions have high-K and adakitic composition and are characterized by high Sr/Y ratios,high SiO_(2)and Al_(2)O_(3)concentrations(SiO_(2)=69.80-73.86 wt%;Al_(2)O_(3)=14.11-15.19 wt%),and low MgO,Cr,and Ni concentrations(MgO=0.2-1.0 wt%;Cr=1.76-11.13 ppm;Ni=2.52-11.72 ppm).Their Sr-Nd isotope compositions(^(87)Sr/^(86)Sr=0.7066-0.7077;εNd(t)=−5.3 to−1.5)are consistent with the lower crustal-derived amphibolite xenoliths(^(87)Sr/^(86)Sr=0.7060-0.7100;εNd(t)=−10.0 to 0.0),indicating that they might be derived from a thickened juvenile lower crust beneath the Yangtze Craton.The biotite-monzonite porphyry has lower zirconδ^(18)O values of+5.3‰to+6.8‰and higherεHf(t)values of−2.3 to+5.5 than those of the quartz-monzonite porphyry withδ^(18)O values of+7.1‰to+8.2‰andεHf(t)values of−3.8 to+1.5,implying that they were derived from different parts of the lower crust.High Ba/La and Pb/Ce ratios suggest that the quartz-monzonite porphyry is derived from a volatiles-rich reservoir.Relatively higher La/Yb,Sm/Yb and Dy/Yb ratios of the biotite-monzonite porphyry indicate residual garnet in the source,indicating a deeper source than that of the quartz-monzonite porphyry.The hydrous components should be represented by the amphibole-rich lithologies,which has relatively shallower depth than that of the garnet-bearing mafic thickened lower crust.Our data suggest that the mineralized quartz-monzonite porphyry at the Beiya deposit is derived from partial melting of amphibole-rich lithologies in the upper part of the thickened juvenile lower crust beneath the Yangtze Craton,while the post-mineralization biotite-monzonite porphyry is derived from the basal,and volatiles-poor,part of the juvenile lower crust.

Au(Cu)Ore-Fluid Dynamics in Bordering OrogenicBelt of Simao-Nanping Basin, Yunnan Province

The paleohydrogeologic condition and the tectonic stress field during the mineralization epoch of the Au (Cu) ore fluid in the bordering orogenic belt of Simao-Nanping basin reveal that the complicated paleohydrodynamic condition during the Devonian-Carboniferous period in the northern Ailao-shan was favorable for the pre-enrichment of the mineral elements, and that the migration and the distribution of the groundwater were controlled by the tectonic stress field and driven by temperature and hydraulic gradients during the Yanshan-Himalayan movement epoch. Therefore, the determination of the low-pressure zone of the maximum principal stress is effective for the location of the Au deposits (ore spots).

Mineralization,Geochemistry and Zircon U-Pb Ages of the Paodaoling Porphyry Gold Deposit in the Guichi Region,Lower Yangtze Metallogenic Belt,Eastern China

The newly discovered Paodaoling porphyry Au deposit from the Guichi region, Lower Yangtze River Metallogenic Belt （LYRB）, contains 〉35 tons of Au at an average grade of -1.7 g/t. It is a porphyry ＇Au-only＇ deposit, as revealed by current exploration in the depths, mostly above -400 m, which is quite uncommon among coeval porphyry mineralization along the LYRB. Additionally, there are also Cu-Au bearing porphyries and barren alkaline granitoids in the Paodaoling district. Zircon LA-ICP-MS U-Pb dating of the Cu-Au-bearing porphyries yield an age of 141-140 Ma, falling within the main magmatic stage of the LYRB, whereas the barren granites give an age of 125-120 Ma, coeval with the regional A- type granites. The Cu-Au-bearing porphyries are LILE-, LREE-enriched and HFSE-depleted, typical of arc magmatic affinities. The barren granites are HFSE-enriched, with lower LREE/HREE ratios and pronounced negative Eu anomalies. The Cu-Au-bearing porphyries in the Paodaoling district have high oxygen fugacities and high water content. Pyrite sulfur isotopes of the Paodaoling gold deposit indicate a magmatic-sedimentary mixed source for the ore-forming fluids. Based on the alteration and poly-metal zonation of the deepest exploration drill hole from the Paodaoling Au deposit, we propose that Cu ore bodies could lie at depth beneath the current Au ore bodies. The magmatism and associated Cu-Au mineralization of the Paodaoling district are likely to have formed in a subduction setting, during slab rollback of the paleo-Pacific plate.

Cenozoic Mineralization in China,as a Key to Past Mineralization and a Clue to Future Prospecting

Many Cenozoic metal deposits have been found during the past decade. Among them, the Fuwan Ag deposit in Guangdong is the largest Ag deposit in China. Besides, the largest Cu deposit of China in Yulong, Tibet, the largest Pb-Zn deposit of China in Jinding, Yunnan, and the largest Au deposit of China in Jinguashi, Taiwan, were also formed in the Cenozoic. Why so many important “present” deposits formed during such a short period of geological history is the key problem. The major reason is that different tectonic settings control different kinds of magmatic activity and mineralization at the same time. In southwestern China, porphyry-type Cu deposits such as Yulong were formed during the early stage of the Himalayan orogeny, sediment-hosted Pb-Zn deposits such as Jinding were formed within intermontane basins related to deep faults, and carbonatite-related deposits such as the Maoniuping REE deposit and alkalic magmatic rock-related deposits such as the Beiya Au deposit originated from the mantle source. In southeastern China, the Fuwan Ag deposit was related to continental rifting which was triggered by the mantle plume. In Taiwan, the Jinguashi Au deposit was formed during the subduction process of an oceanic plate beneath a continental plate. Besides, the features such as the diversification, inheritance, large size, deep source of metals and fluids of the Cenozoic (Present or Recent) mineralization can be used as a key to the search for past deposits.

Deep gold mineralization features of Jiaojia metallogenic belt,Jiaodong gold Province:Based on the breakthrough of 3000 m exploration drilling

Recently,continuous breakthroughs have been made about deep gold prospecting in the Jiaodong gold province area of China.Approximately 5000 t of cumulative gold resources have been explored in Jiaodong,which has thus become an internationally noteworthy gold ore cluster.The gold exploration depth has been increased to about 2000 m from the previous<1000 m.To further explore the mineralization potential of the Jiaodong area at a depth of about 3000 m,the Shandong Institute of Geological Sciences has drilled an exploratory drillhole named“Deep drillhole ZK01”to a depth of 3266 m.Hence,as reported herein,the mineralization characteristics of the Jiaojia metallogenic belt have been successfully documented.ZK01 is,to date,the deepest borehole with an gold intersect in China,and constitutes a significant advance in deep gold prospecting in China.The findings of this study further indicate that the depth interval of 2000 m to 4000 m below the ground surface in the Wuyi Village area incorporates 912 t of inferred gold resources,while the depth interval of 2000 m to 4000 m below the surface across the Jiaodong area possesses about 4000 t of inferred gold resources.The Jiaojia Fault Belt tends to gently dip downward,having dip angles of about 25°and about 20°at vertical depths of 2000 m and 2850 m,respectively.The deep part of the Jiaojia metallogenic belt differs from the shallow and moderately deep parts about fracturing,alteration,mineralization,and tectonic type.The deep zones can generally be categorized from inside outward as cataclastic granite,granitic cataclasite,weakly beresitized granitic cataclasite,beresitized cataclasite,and gouge.These zones exhibit a gradual transitional relation or occur alternately and repeatedly.The mineralization degree of the pyritized cataclastic granite-type ore in the deep part of the Jiaojia metallogenic belt is closely related to the degree of pyrite vein development;that is,the higher the pyrite content,the wider the veins and the higher the gold grade.Compared to the shallow gold ores,the deep-seated gold ores have higher fineness and contain joseite,tetradymite,and native bismuth,suggesting that the deep gold mineralization temperature is higher and that mantle-sourced material may have contributed to this mineralization.ZK01 has also revealed that the deep-seated ore bodies in the Jiaojia metallogenic belt are principally situated above the main fracture plane(gouge)and hosted within the Linglong Granite,contradicting previous findings indicating that the moderately shallow gold ore bodies are usually hosted in the contact zone between the Linglong Granite and Jiaodong Group or meta-gabbro.These new discoveries are particularly significant because they can help correct mineralization prospecting models,determine favorable positions for deep prospecting,and improve metallogenic prediction and resource potential evaluation.

Role of Hematite-Rich Host Rocks in the Gold Mineralization of the Woxi Au(-Sb-W) Ore Deposit in Western Jiangnan Orogen of South China

The formation of many hydrothermal gold deposits is closely related to iron-rich rocks. The host rocks of the Madiyi Formation of the Mid-to Late Neoproterozoic Banxi Group for the Woxi Au(-Sb-W) deposit, which is located in western Hunan Province of the western Jiangnan Orogen, South China, is rich in hematite, which provides a good example for studying the relationship between the formation of gold deposit and iron-rich rocks. Field investigation and petrographic observation on the unaltered, weakly altered and strongly altered rocks demonstrate that the bleaching is caused by a combination of carbonatization, sulfidation and sericitization. Mass balance calculation suggests that, during decolourization there is no change in TFe_(2)O_(3), while FeO is gained and Fe_(2)O_(3)is lost. Geochemical modeling found that Au was mainly present as AuHS(aq) and Au(HS)-2, and that the water-rock interactions decreased the sulfur fugacity which destroyed the stability of such aqueous complexes. Combined with the locally occurred native gold in quartz veins, it is concluded that the major gold precipitation mechanisms are sulfidation and fluid boiling. Based on previous geochronological and geochemical research further gold mineralization is proposed to be generated by deep sourced magmatic or metamorphic fluid migrated upward along the Woxi fault, and the iron-rich Madiyi Formation is the idea chemical trap for gold deposition. The decrease of sulfur contents caused by fluid-rock interactions and fluid boiling are the major mechanisms for gold mineralization.

Chemical vapor deposition of monolayer WS2 nano- sheets on Au foils toward direct application in hydrogen evolution

Monolayer tungsten disulfide （WS2）, a typical member of the semiconducting transition metal dichalcogenide family has drawn considerable interest because of its unique properties. Intriguingly the edge of WS2 exhibits an ideal hydrogen binding energy which makes WS2 a potential alternative to Pt-based electrocatalysts for the hydrogen evolution reaction （HER）. Here, we demonstrate for the first time the successful synthesis of uniform monolayer WS2 nanosheets on centimeter- scale Au foils using a facile, low-pressure chemical vapor deposition method. The edge lengths of the universally observed triangular WS2 nanosheets are tunable from -100 to N1,000 nm. The WS2 nanosheets on Au foils featuring abundant edges were then discovered to be efficient catalysts for the HER, exhibiting a rather high exchange current density of -30.20 μA/cm2 and a small onset potential of Nl10 mV. The effects of coverage and domain size （which correlate closely with the active edge density of WS2） on the electrocatalytic activity were investigated. This work not only provides a novel route toward the batch-production of monolayer WS2 via the introduction of metal foil substrates but also opens up its direct application for facile HER.

An in situ STM investigation of EMITFSI ionic liquid on Au(111)in the presence of lithium salt

We report an in situ scanning tunneling microscopic study of surface morphology changes in Au（111） electrode in 1-ethyl-3-methylimidazolium bis（trifluoromethylsulfonyl）imide （EMITFSI） ionic liq- uid containing LiTFSI salt. The surface processes can be divided into three stages： In the first stage, a re- duction wave of dissolved oxygen in the ionic liquid appears at approximately 2.0 V and a network structure covers the surface afterward; in the second stage at around 1.5 V, reduction of trace water is initiated and a surface film containing lithium hydroxide is formed; in the third stage, as potential is further decreased to 0.85 V, decomposition of the EMITFSI ionic liquid occurs, which is accompanied by lithium underpotential deposition and Au-Li alloying. In this stage, the surface experiences significant morphological changes with formation of many clusters on the surface, and even- tually becomes electronically less conductive. This unique surface film is understood to be the initial stage formation of a solid electrolyte interphase on gold, which may be a common feature in ionic liquids in the presence of lithium salt.