The Mailong gold deposit is located in the eastern section of the East Kunlun orogenic belt and is one of the recently discovered important gold polymetallic deposits in the Qinhai Gouli region.The primary host rocks ...The Mailong gold deposit is located in the eastern section of the East Kunlun orogenic belt and is one of the recently discovered important gold polymetallic deposits in the Qinhai Gouli region.The primary host rocks of the Mailong gold deposit consist of intermediate-acid intrusive rocks from the Varisian and Indosinian periods,as well as the Precambrian Jinshuikou Group,with mineralization controlled by northeast and northwest faults.The alteration of the host rocks is mainly characterized by silicification,sericitization,chloritization,and carbonatization.Based on the cross-cutting relationships of the veins,the hydrothermal mineralization of the gold deposit can be categorized into three stages:the quartz-pyrite stage,the quartzpolymetallic sulfide stage,and the quartz-carbonate stage.Microthermometry of fluid inclusions indicates that the Mailong gold deposit belongs to a low-density(0.73–0.86 g/cm3),medium-temperature(240–340℃),and medium-salinity(4.01–10.74 wt%NaCl)NaCl-CO2-H2O fluid system.The C-H-O isotopic analysis suggests that the mineralizing fluids is derived from magmatic water,with later contributions from atmospheric precipitation.In-situ S isotopic results indicate that the mineralizing materials mainly derive from igneous rocks.A comprehensive analysis concludes that the Mailong gold deposit is a mesothermal hydrothermal vein-type gold deposit controlled by structural factors.展开更多
The Sakay gold deposit in Vientiane,Laos,is located in the Indochina landmass of the southeastern segment of the Tethys orogenic belt,specifically within the Vientiane-Pakse micro-landmass and the Vientiane-Pakse meta...The Sakay gold deposit in Vientiane,Laos,is located in the Indochina landmass of the southeastern segment of the Tethys orogenic belt,specifically within the Vientiane-Pakse micro-landmass and the Vientiane-Pakse metallogenic belt.This area is regionally significant for the concentration of minerals such as gold,copper,and tin.The host rocks of the deposit are intermediate volcanic lavas and volcanic tuffs,occurring in near-east-west brittle shear structural fractures through hydrothermal filling and metasomatism.The ore exhibits granular texture,subhedral texture,porphyritic texture,and oriented polycrystalline texture,with structural features such as disseminated,vein-like,and cataclastic breccia.The main ore minerals are pyrite,sphalerite,galena,and chalcopyrite,while the gangue minerals are primarily quartz,calcite,and dolomite.Gold is mainly present as included gold or fissure gold within the crystal lattices and microfractures of minerals such as pyrite and sphalerite.Based on mineral assemblages and generation timing,the mineralization can be divided into three stages:arsenopyrite-pyrite-dolomite-quartz(Ⅰ),sphalerite-galena-chalcopyrite-calcite(Ⅱ),and siderite(Ⅲ),with the latter stages often overlaying the former,showing evident cross-cutting and metasomatic phenomena.The surrounding rocks in the mining area are altered,mainly showing silicification,carbonatization,limonitization,sericitization,and chloritization.Preliminary studies suggest that this deposit is a low-temperature hydrothermal gold deposit within a brittle shear zone.展开更多
This paper describes a method for estimating the continuation of ore bodies at depth based on concentrationvolume(C-V)fractal modeling of the pyrite thermoelectric coefficient in the Pujon gold deposit,Democratic Peo...This paper describes a method for estimating the continuation of ore bodies at depth based on concentrationvolume(C-V)fractal modeling of the pyrite thermoelectric coefficient in the Pujon gold deposit,Democratic People’s Republic of Korea.The method is first established using data in the Kumjomdong area,a well-explored brownfield,and it is then applied to estimate the continuation of ore bodies at depth in the Pyongsandok area,a less-explored greenfield.The methodology consists of four steps:(1)3D modeling of ore bodies using surface geological mapping,mining tunnels in different levels,and a borehole dataset;(2)3D modeling of thermoelectricity coefficients from Au-bearing pyrites based on discrete smooth interpolation and C-V fractal techniques;(3)determination of levels used for calculation of the thermoelectric parameter of pyrite by C-V fractal modeling instead of traditional levels;and(4)determination of the thermoelectric parameter vertical gradient of pyrite reflecting the variation characteristics of pyrite thermoelectricity in the Pujon deposit.The results indicate that(1)pyrites in the Pujon deposit are dominantly P-type,and it is not reasonable to use traditional levels to calculate the thermoelectric parameter of pyrite;(2)thresholds determined by C-V fractal modeling can be used as levels to calculate the thermoelectric parameter of pyrite;(3)the thermoelectric parameter vertical gradient of pyrite ranges from 1 to 2 in the Pujon deposit;and(4)ore body Pyongsan No.9 extends 85 m to 235 m downward from the current borehole location.展开更多
Recently identified hydrothermal monazite from the Sidaogou deposit in the Liaodong Peninsula,is co-genetic with gold-bearing ore minerals and thus can serve as ideal proxy for dating the gold-mineralization event.Our...Recently identified hydrothermal monazite from the Sidaogou deposit in the Liaodong Peninsula,is co-genetic with gold-bearing ore minerals and thus can serve as ideal proxy for dating the gold-mineralization event.Our study effectively solved the dilemma of lack of any accurate age for the Sidaogou deposit.The Sidaogou deposit is hosted mainly by Paleoproterozoic metamorphic rocks of the Liaohe Group,and hydrothermal monazite therein occurs within voids or along micro-fractures in syn-ore pyrite and quartz.First in situ SIMS U-Th-Pb isotope data on this monazite from the Sidaogou deposit yielded an inverse Concordia age of 184±20 Ma,which is much younger than an^(40)Ar-^(39)Ar age of 1858.9±25.4 Ma obtained on muscovite from the host rock(Gaixian Formation),thus supporting a prominent Early Jurassic gold mineralization event in the Wulong gold field,which is distinct from previously established Early Cretaceous gold mineralization,held responsible for the nearby large Wulong gold deposit.Our new findings make it possible,together with previous studies,to formulate a model for the Early Jurassic magmatic-hydrothermal gold system in the area,for which a compressional setting during the westward subduction of the Paleo-Pacific Plate beneath the North China Craton is postulated.展开更多
The Taishang-Shuiwangzhuang gold deposit is located in the southeastern margin of Linglong gold field in the northern part of the Zhaoping Fault metallogenic belt of the Jiaodong gold province-the world’s third-large...The Taishang-Shuiwangzhuang gold deposit is located in the southeastern margin of Linglong gold field in the northern part of the Zhaoping Fault metallogenic belt of the Jiaodong gold province-the world’s third-largest gold metallogenic area.Major prospecting breakthroughs have been made at the depth of 600‒2500 m in recent years,with cumulative proven gold resources exceeding 700 t.Based on a large number of exploration data,the main characteristics of the deposit are described in detail,and the spatial coupling relationship between ore-controlling fault and main orebodies is discussed.The main orebodies occur as regular large veins,exhibiting branching and combination,expansion and contraction,and pinch-out and reoccurrence.They extend in a gentle wave pattern along their strikes and dip directions and generally have a pitch direction of NEE and a plunge direction of NEE.As the ore-controlling fault,the Zhaoping Fault has the characteristics of wave-like fluctuation,with its dip angle presenting three steps of steep-slow transition within the depth range of 2500 m.The gold mineralization enrichment area is mainly distributed in the step parts where the fault plane changes from steeply to gently.The ore-forming age,ore-forming fluid and ore-forming material sources and the genesis of the ore deposit are analyzed based on the research results of ore deposit geochemistry.The ore-forming fluids were H_(2)O-CO_(2)-NaCl-type hydrothermal solutions with a medium-low temperature and medium-low salinity.The H-O isotopic characteristics indicate that the fluids in the early ore-forming stage were possibly formed by degassing of basic magma and that meteoric water gradually entered the ore-forming fluids in the late ore-forming stage.The S and Pb isotopes indicate that the ore-forming materials mainly originate from the lower crust and contain a small quantity of mantle-derived components.The comprehensive analysis shows that the Taishang-shuiwangzhuang gold deposit was a typical“Jiaodong type”gold deposit.The strong crust-mantle interactions,large-scale magmatism,and the material exchange arising from the transformation from the ancient lower crust to the juvenile lower crust during the Early Cretaceous provided abundant fluids and material sources for mineralization.Moreover,the detachment faults formed by the rapid magmatic uplift and the extensional tectonism created favorable temperature and pressure conditions and space for fluid accumulation and gold precipitation and mineralization.展开更多
Since the first discovery of gold deposits on the northeastern margin of the Jiaolai Basin in Shandong Province at the end of the 20^(th) century,seven medium-sized to large/super-large gold deposits have been identif...Since the first discovery of gold deposits on the northeastern margin of the Jiaolai Basin in Shandong Province at the end of the 20^(th) century,seven medium-sized to large/super-large gold deposits have been identified in this region,with cumulative proven gold resources of 223 t.This study reviewed the metallogenic and geochemical characteristics of various gold deposits in this region,examined the sources of their ore-forming fluids and materials,as well as their gold metallogenic epochs and processes,and developed a gold metallogenic model.The gold deposits in this region are governed by both dense fractures and detachment structural systems along basin margins,primarily categorized into the altered rock type and the pyrite-bearing carbonate vein type.The latter type,a recently discovered mineralization type in the Jiaodong Peninsula,enjoys high gold grade,a large scale,and high gold mineral fineness,suggesting considerable prospecting potential.Both types of gold deposits show metallogenic epochs ranging from 116 Ma to 119 Ma.Their ore-forming fluids are identified as a CO_(2)-NaCl-H_(2)O fluid system characterized by moderate to low temperatures,moderate to low salinity,and low density,with the pyrite-bearing carbonate vein-type gold deposits manifesting slightly higher salinity.The C-H-O,S,and Pb isotopes of hydrothermal minerals reveal that the ore-forming fluids and materials are characteristic of crust-mantle mixing.Specifically,they were derived from mantle fluids in the early stages,mixed with stratum water and meteoric water in the later stages for mineralization.The gold metallogenic process is identified as follows:During the Early Cretaceous,the subduction of the Pacific Plate and the destruction of the North China Craton led to asthenospheric upwelling.The resulting fluids,after metasomatizing the enriched mantle,differentiated and evolved into C-H-O ore-bearing fluids,which were then mixed with crustal fluids.The mixed fluids migrated to the shallow crust,where they mingled with stratum water and meteoric water.Then,the fluids underwent unloading and final mineralization in detachment fault tectonic systems on basin margins.Due to differences in mixed crustal materials or the surrounding rocks involved in water-rock interactions,altered rock-and pyrite-bearing carbonate vein-type gold deposits were formed in acidic and alkaline fluid environments,respectively.展开更多
Dongguashan deposit is a large porphyry-skarn copper（gold） deposit in Tongling ore district. The Qingshanjiao intermediate acid intrusion of Yanshanian had a direct genetic relationship with mineralization. The magm...Dongguashan deposit is a large porphyry-skarn copper（gold） deposit in Tongling ore district. The Qingshanjiao intermediate acid intrusion of Yanshanian had a direct genetic relationship with mineralization. The magma origin, rock-forming dynamic background and rock-forming process were studied, and the rock-forming mechanism of Qingshanjiao intrusion was discussed, based on geological characteristics, detailed observation of petrography and systematic investigation of petrochemistry, trace elements and REE geochemistry characteristics of Qingshanjiao intrusion. The results show that Qingshanjiao rock body belongs to high-K calc-alkaline series with higher LREE elements, Th, Rb and Sr abundance, but depleted in HREE elements, Ba, Nb and Ta. The primary magma originated from the mantle-crust mixtures which were caused by basaltic magma of mantle mixing with syenite magma of partial melting of the lower crust, and the formation environment of Qingshanjiao intrusion was emplaced in the transitional environment from compression to extension. The Harker diagram and hybrid structures of plagioclase and potassium feldspar indicate that the fractional crystallization occurred in the process of magmatic evolution. The petrochemistry, trace elements and REE geochemistry characteristics indicate that the magma was contaminated by crustal material during the rock-forming. These results suggested that the Qingshanjiao intrusion was formed by fractional crystallization and assimilation and hybridization of mantle-crust magma in the transitional environment from compression to extensional.展开更多
The Jiaodong gold deposits are currently the most important gold resources（with Au reserves of〉4000 t） in China,and the leading gold-producing country globally（with Au production of ～428 t in2013）.Jiaodong is al...The Jiaodong gold deposits are currently the most important gold resources（with Au reserves of〉4000 t） in China,and the leading gold-producing country globally（with Au production of ～428 t in2013）.Jiaodong is also considered as perhaps the only world-class to giant gold accumulation on the planet where relatively young gold ores（ca.130-120 Ma） were deposited in rocks that are 2 Ga older.The Xincheng world-class high-grade gold deposit,with a proven reserve of 〉200 t gold,is one of the largest deposits in the giant gold province of the Jiaodong Peninsula.It is located in the northwestern part of the jiaobei Uplift,and hosted by ca.132-123 Ma Xincheng quartz monzonites and monzogranites.Ore zones are structurally controlled by the NE-trending and NW-dipping Jiaojia Fault and subsidiary faults,and are mainly restricted to the footwall of the fault.The dominant disseminated- and stockworkstyle ores are associated with strong sericitization,silicification,sulfidation and K-feldspathization,and minor carbonate wallrock alteration halos.The four mineralization stages are pyrite-quartz-sericite（stage 1）,quartz-pyrite（stage 2）,quartz-polysulfide（stage 3） and quartz-carbonate（stage 4）.Gold occurs dominantly as electrum,with lesser amounts of sulfide-hosted native gold and rare native silver and argentite,normally associated with pyrite,chalcopyrite,galena and sphalerite：the latter with proven resources of about 105 t Ag,713 t Cu,and 5100 t S.There are three types of ore-related fluid inclusions：type 1 aqueous-carbonate（H2O-CO2）,type 2aqueous（liquid H2O＋vapor H2O）,and type 3 CO2（liquid CO2 and vapor CO2） inclusions.Homogenization temperatures range from 221 to 304℃ for type 1 inclusions,with salinities of 2.4-13.3 wt.%NaCl eq.,and bulk densities of 0.858-1.022 g/cm～3.The δ～（34）S（CDT） values of hydrothermal sulfides are 4.3-10.6‰and δ～（18）O values of hydrothermal quartz have a median value of 13.0‰.δD values of fluid inclusions in hydrothermal quartz have a median value of-75‰.Calculated δ～（18）Owater has a median value of 5.2‰.The timing of gold mineralization at the Xincheng gold deposit is younger than 123±1 Ma,and likely between 120.9 and 119.9 Ma.A minerals system genetic model for the probable epizonal orogenic Xincheng deposit suggests an initial medium temperature,CO2-rich,and low salinity H2O-CO2 deeply sourced metamorphic ore fluid associated with dehydration and decarbonization of subducting Paleo-Pacific lithosphere.The Jiaojia Fault constrained the migration of ore-forming fluids and metals at the brittle-ductile transition.Fluid immiscibility,caused by episodic pressure drops,led to significant high-grade gold deposition in the giant Xincheng gold deposit.展开更多
The recently discovered Damoqujia （大磨曲家） gold deposit is a large shear zone-hosted gold deposit of disseminated sulphides located in the north of the Zhaoping （招平） fault zone, Jiaodong （胶东） gold province...The recently discovered Damoqujia （大磨曲家） gold deposit is a large shear zone-hosted gold deposit of disseminated sulphides located in the north of the Zhaoping （招平） fault zone, Jiaodong （胶东） gold province, China. In order to distinguish the temperature range of cluster inclusions from different mineralization stages and measure their compositions, 16 fluid inclusions and 5 isotopic geochemistry samples were collected for this study. Corresponding to different mineralization stages, the multirange peaks of quartz decrepitation temperature （250-270, 310-360 and 380-430℃） indicate that the activity of ore-forming fluids is characterized by multistage. The ore-forming fluids were predominantly of high-temperature fluid system （HTFS） by CO2-rich, and SO4^2--K^＋ type magmatic fluid during the early stage of mineralization and were subsequently affected by low-temperature fluid system （LTFS） of CH4-rich, and Cl^--Na^＋/Ca^2＋ type meteoric fluid during the late stage of mineralization. Gold is transferred by Au-HS^- complex in the HTFS, and Au-Cl^- complex can be more important in the LTFS. The transition of fluids from deeper to shallow environments results in mixing between the HTFS and LTFS, which might be one of the most key reasons for gold precipitation and large-scale mineralization. The ore-forming fluids are characterized by high-temperature, strong-activity, and superimposed mineralization, so that there is a great probability of forming large and rich ore deposit in the Damoqujia gold deposit. The main bodies are preserved and extend toward deeper parts, thereby suggesting a great potential in future.展开更多
It is quite evident that it is not anomalous metal transport,nor unique depositional conditions,nor any single factor at the deposit scale,that dictates whether a mineral deposit becomes a giant or not.A hierarchical ...It is quite evident that it is not anomalous metal transport,nor unique depositional conditions,nor any single factor at the deposit scale,that dictates whether a mineral deposit becomes a giant or not.A hierarchical approach thus is required to progressively examine controlling parameters at successively decreasing scales in the total mineral system to understand the location of giant gold deposits in non-arc environments.For giant orogenic,intrusion-related gold systems（IRGS） and Carlin-type gold deposits and iron oxide-copper-gold（IOCG） deposits,there are common factors among all of these at the lithospheric to crustal scale.All are sited in giant gold provinces controlled by complex fundamental fault or shear zones that follow craton margins or,in the case of most Phanerozoic orogenic giants,define the primary suture zones between tectonic terranes.Giant provinces of IRGS,IOCG,and Carlin-type deposits require melting of metasomatized lithosphere beneath craton margins with ascent of hybrid lamprophyric to granitic magmas and associated heat flux to generate the giant province.The IRGS and IOCG deposits require direct exsolution of volatile-rich magmatic-hydrothermal fluids,whereas the association of such melts with Carlin-type ores is more indirect and enigmatic.Giant orogenic gold provinces show no direct relationship to such magmatism.forming from metamorphic fluids,but show an indirect relationship to lamprophyres that reflect the mantle connectivity of controlling first-order structures.In contrast to their province scale similarities,the different giant gold deposit styles show contrasting critical controls at the district to deposit scale.For orogenic gold deposits,the giants appear to have formed by conjunction of a greater number of parameters to those that control smaller deposits,with resultant geometrical and lithostratigraphic complexity as a guide to their location.There are few giant IRGS due to their inferior fluid-flux systems relative to orogenic gold deposits,and those few giants are essentially preservational exceptions.Many Carlin-type deposits are giants due to the exceptional conjunction of both structural and lithological parameters that caused reactive and permeable rocks,enriched in syngenetic gold,to be located below an impermeable cap along antiformal ＂trends＂.Hydrocarbons probably played an important role in concentrating metal.The supergiant Post-Betze deposit has additional ore zones in strain heterogeneities surrounding the pre-gold Goldstrike stock.All unequivocal IOCG deposits are giant or near-giant deposits in terms of gold-equivalent resources,partly due to economic factors for this relatively poorly understood,low Cu-Au grade deposit type.The supergiant Olympic Dam deposit,the most shallowly formed deposit among the larger IOCGs,probably owes its origin to eruption of volatile-rich hybrid magma at surface,with formation of a large maar and intense and widespread brecciation,alteration and Cu-Au-U deposition in a huge rock volume.展开更多
The superlarge Baguamiao, large Liba and Xiaogouli gold deposits represent three typical gold deposits different from the Carlin type in the western Qinling Orogenic Belt. Based on Ar-Ar dating of quartz from ores, U-...The superlarge Baguamiao, large Liba and Xiaogouli gold deposits represent three typical gold deposits different from the Carlin type in the western Qinling Orogenic Belt. Based on Ar-Ar dating of quartz from ores, U-Pb dating of single zircon from granite, tracing of H and O isotopes and studies on the mineralogy and texture of spots and bleached alteration developed in wall rocks, this paper focuses the relations between gold deposits and granite to clarify the origin of gold deposits and the metallogenesis in the tectonic evolution of the Qinling Orogenic Belt. The comprehensive studies show that the age of the granite (148.1-244 Ma) is identical with that of the gold deposits (131.91-232.56 Ma). It is suggested that the granite has close temporal, spatial and genetic relationship with the gold deposits. The granite provides a heat source, water source and considerable amount of ore-forming material. Finally, it is concluded that the orogeny by collision, emplacement of the granite and positioning of the gold deposits represent a successive process. Both the granite and gold deposits resulted from the syn-orogeny and post-orogeny tectonic evolution.展开更多
With very few exceptions, orogenic gold deposits formed in subduction-related tectonic settings in accretionary to collisional orogenic belts from Archean to Tertiary times. Their genesis, including metal and fluid so...With very few exceptions, orogenic gold deposits formed in subduction-related tectonic settings in accretionary to collisional orogenic belts from Archean to Tertiary times. Their genesis, including metal and fluid source, fluid pathways, depositional mechanisms, and timing relative to regional structural and metamorphic events, continues to be controversial. However, there is now general agreement that these deposits formed from metamorphic fluids, either from metamorphism of intra-basinal rock sequences or de-volatilization of a subducted sediment wedge, during a change from a compressional to transpressional, less commonly transtensional, stress regime, prior to orogenic collapse. In the case of Archean and Paleoproterozoic deposits, the formation of orogenic gold deposits was one of the last events prior to cratonization. The late timing of orogenic gold deposits within the structural evolution of the host orogen implies that any earlier structures may be mineralized and that the current structural geometry of the gold deposits is equivalent to that at the time of their formation provided that there has been no significant post-gold orogenic overprint. Within the host volcano-sedimentary sequences at the province scale, world-class orogenic gold deposits are most commonly located in second-order structures adjacent to crustal scale faults and shear zones, representing the first-order ore-forming fluid pathways, and whose deep lithospheric connection is marked by lamprophyre intrusions which, however, have no direct genetic association with gold deposition. More specifically, the gold deposits are located adjacent to ～10°-25° district-scale jogs in these crustal-scale faults. These jogs are commonly the site of arrays of ～70° cross faults that accommodate the bending of the more rigid components, for example volcanic rocks and intrusive sills, of the host belts. Rotation of blocks between these accommodation faults causes failure of more competent units and/or reactivation and dilation of pre-existing structures, leading to deposit-scale focussing of ore-fluid and gold deposition.Anticlinal or antiformal fold hinges, particularly those of ＇locked-up＇ folds with ～30° apical angles and overturned back limbs, represent sites of brittle-ductile rock failure and provide one of the more robust parameters for location of orogenic gold deposits.In orogenic belts with abundant pre-gold granitic intrusions, particularly Precambrian granitegreenstone terranes, the boundaries between the rigid granitic bodies and more ductile greenstone sequences are commonly sites of heterogeneous stress and inhomogeneous strain. Thus, contacts between granitic intrusions and volcano-sedimentary sequences are common sites of ore-fluid infiltration and gold deposition. For orogenic gold deposits at deeper crustal levels, ore-forming fluids are commonly focused along strain gradients between more compressional zones where volcano-sedimentary sequences are thinned and relatively more extensional zones where they are thickened. World-class orogenic gold deposits are commonly located in the deformed volcano-sedimentary sequences in such strain gradients adjacent to triple-point junctions defined by the granitic intrusions, or along the zones of assembly of micro-blocks on a regional scale. These repetitive province to district-scale geometrical patterns of structures within the orogenic belts are clearly critical parameters in geology-based exploration targeting for orogenic gold deposits.展开更多
Orogenic disseminated and Carlin gold deposits share much similarity in alteration and mineralization.The disseminated orogenic Zhenyuan Au deposit along the Ailaoshan shear zone,southeastern Tibet,was selected to cla...Orogenic disseminated and Carlin gold deposits share much similarity in alteration and mineralization.The disseminated orogenic Zhenyuan Au deposit along the Ailaoshan shear zone,southeastern Tibet,was selected to clarify their difference.The alteration and mineralization from the different lithologies,including meta-quartz sandstone,carbonaceous slate,meta-(ultra)mafic rock,quartz porphyry and lamprophyre were researched.According to the mineral assemblage and replacement relationship in all types of host rocks,two reactions show general control on gold deposition:(1) replacement of earlier magnetite by pyrite and carbonaceous material;(2) alteration of biotite and phlogopite phenocrysts in quartz porphyry and lamprophyre into dolomite/ankerite and sericite.Despite the lamprophyre is volumetrically minor and much less fractured than other host rocks,it contains a large portion of Au reserve,indicating that the chemically active lithology has played a more important role in gold precipitation compared to structure.LA-ICP-MS analysis shows that Au mainly occurs as invisible gold in fine-grained pyrite disseminated in the host rocks,with Au content reaching to 258.95 ppm.The diagenetic core of pyrite in meta-quartz sandstone enriched in Co,Ni,Mo,Ag and Hg is wrapped by hydrothermal pyrite enriched in Cu,As,Sb,Au,Tl,Pb and Bi.Different host rock lithology has much impact on the alteration and mineralization features.Carbonate and sericite in altered lamprophyre show they have higher Mg than those developed in other of host rocks denoting that the carbonate and sericite incorporated Mg from phlogopite phenocrysts in the primary lamprophyre during alteration.The ore fluid activated the diagenetic pyrite in meta-quartz sandstone leading the hydrothermal pyrite enriched in Cu,Mo,Ag,Sb,Te,Hg,Tl,Pb and Bi,but the hydrothermal pyrite in meta-(ultra)mafic rock is enriched in Co and Ni as the meta-(ultra)mafic rock host rock contain high content of Co and Ni.However,Au and As shear similar range in both types of host rocks indicating that these two elements most likely come from the deep source fluid rather than the host rocks.It was shown in the disseminated orogenic gold deposit that similar hydrothermal alteration with mineral assemblage of carbonate (mainly dolomite and ankerite),sericite,pyrite and arsenopyrite develops in all types of host rocks.This is different from the Nevada Carlin type,in which alteration is mainly dissolution and silicification of carbonate host rock.On the other hand,Au mainly occur as invisible gold in both disseminated orogenic and Carlin gold deposits.展开更多
In the light of field investigation, microscopic study, X\|ray phase analysis and mineral infrared spectral analysis, it is considered that laumontitization is of extensive occurrence in the Axi gold orefield. The dev...In the light of field investigation, microscopic study, X\|ray phase analysis and mineral infrared spectral analysis, it is considered that laumontitization is of extensive occurrence in the Axi gold orefield. The development of laumontitization and its relationship to mineralization show that the laumontitization appeared mainly at the top of and in the periphery of orebodies, and occurred at the edge of the epithermal system or at the late stage of epithermal system evolution. Therefore, laumontitization can be used as an exploration indicator of epithermal gold deposits. The fluids responsible for laumontitization in the Axi gold orefield are similar to those producing hot spring\|type gold deposits or those from modern geothermal fields. Epithermal mineralization of the Axi gold deposit was dated at Carboniferous, indicating that the West Tianshan of China is a region favorable to epithermal\|type gold mineralization and preservation. Hence the West Tianshan of China is a target area for exploring epithermal gold deposits.展开更多
The Shangzhuang altered-rock type gold ore deposit is located in the middle segment of and controlled by the Wang＇ershan fault zone in the northwestern part of the Jiaodong gold province, China. The deformation evolu...The Shangzhuang altered-rock type gold ore deposit is located in the middle segment of and controlled by the Wang＇ershan fault zone in the northwestern part of the Jiaodong gold province, China. The deformation evolution, the structure of strain and stress fields and its ore-controlling effect in the Shangzhuang deposit are discussed in this paper. It is revealed that the deformation evolution has mainly undergone four phases： the early ductile deformation, the second NE-striking horizontal simple shear, the third NE-striking compression-shear and the final NW-striking compression. The mineralization happened during the third stage in which the maximum principal stress gradually transited from NE to NW. The 3-D numerical simulations of the stress field show that, on the condition that the maximum principal stress is NE-striking, the fracture development in the fault zone is favored, while when the maximum principal stress is NW-striking, the fault zone is relatively extensional and it is suitable for the influx and emplacement of ore-forming fluids. The compression-shear strain field during the mineralization is characterized by the λ-type structure, the positive flower structure, etc. Orebodies are mostly equidistantly located in the dilatational spaces, which are distributed in the integral compressional circumstances. And the dilatational spaces are developed where the fault attitude changes or shear joint systems develop. In the overall compression-shear stress field, the strain field bears self-similarity at multiple scales, including the orebody, ore deposit and orefield. The selfsimilarity of the structure comprises the subequidistant distribution of fractures at the same scale and the similar shape of the fractures at various scales. Yet, due to the special geological structure, the orebodies are mostly located in the hanging wall in the Shangzhuang deposit, which is different from most deposits in the Jiaodong gold province. Analyses of the ore-controlling stress and strain fields in the deposit provide an important basis for deposit seeking.展开更多
The Muruntau gold deposit in the Central Kyzylkum,Uzbekistan is one of the largest single gold deposits worldwide.Data available from the literature are reviewed with the aim to（1） integrate the present knowledge on...The Muruntau gold deposit in the Central Kyzylkum,Uzbekistan is one of the largest single gold deposits worldwide.Data available from the literature are reviewed with the aim to（1） integrate the present knowledge on this unique deposit from Russian and English literature;（2） show the considerable progress made in the understanding of the genesis of the Muruntau deposit during the last decades;and（3） point to problems still open for future research.Deposit formation occurred through a multi-stage process involving sedimentation,regional metamorphism including thrusting,magmatism with formation of hornfels aureoles and several stages of hydrothermal activity.According to recent knowledge,synsedimentary or pure metamorphic formation of gold mineralization seems unlikely.The role of granite magmatism occurring roughly within the same time interval as the main hydrothermal gold precipitation remains uncertain.There are no signs of interaction of matter between the magma（s） and the hydrothermal system（s）.On the other hand,there was an intense,high-temperature（above 400 ℃）fluid- wall rock interaction resulting in the formation of gold-bearing,cone-like stockworks with veins,veinlets and gold-bearing metasomatites.Several chemical and isotope indicators hint at an involvement of lower-crustal or mantle-related sources as well as of surface waters in ore formation.Deposit formation through brecciation involving explosion,hydrothermal or tectonic breccias might explain these data.Further investigations on breccia formation as well as on the exact timing of relevant sedimentary,metamorphic,magmatic and hydrothermal events are recommended.展开更多
Mineral assemblages formed during hydrothermal alteration reflect the geochemical composition of ore-forming fluids. Gold is mainly transported in solution as Au-CI and Au-S complexes. The change of physicochemical co...Mineral assemblages formed during hydrothermal alteration reflect the geochemical composition of ore-forming fluids. Gold is mainly transported in solution as Au-CI and Au-S complexes. The change of physicochemical conditions such as temperature, pressure, oxygen fugacity, and sulfur fugacity are effective mechanisms for gold precipitation. Gold tends to be concentrated in the vapor phase of fluids at high temperatures and pressures. Au-As and Au-Sb associations are common in gold deposit. Native antimony and/or arsenic -- native gold assemblages may precipitate from hydrothermal fluids with low sulfur fugacity. Hydrothermal fluids forming epithermal gold deposits are Au-saturated in most cases, whereas fluids of Carlin-type are Au-undersaturated. Quasi-steady As-bearing pyrite extracts solid solution Au from hydrothermal fluids through absorption. The capability of As-bearing pyrite to absorb An from under-saturated fluid is the key to the formation of large-scale Carlin-type deposits. With increasing new data, studies on the geochemistry of gold deposits can be used to trace the origin of ore-forming fluids, the source of gold, and the transporting form of Au and other ore-forming elements, such as Si, S, F, Cl, As and Ag.展开更多
The Phapon gold deposit, located in northern Laos, is a unique large-scale gold deposit in Luang Prabang-Loei metallogenic belt. It is hosted in the Lower Permian limestone and controlled by a NE-trending ductile-brit...The Phapon gold deposit, located in northern Laos, is a unique large-scale gold deposit in Luang Prabang-Loei metallogenic belt. It is hosted in the Lower Permian limestone and controlled by a NE-trending ductile-brittle fault system. There are three types of primary ore including auriferous calcite vein type, disseminated type, and breccia type, and the first two are important in the Phapon gold deposit. Based on fluid inclusion petrography and microthermometry, three types of primary fluid inclusions including type 1 liquid-rich aqueous, type 2 vapor-rich aqueous and type 3 daughter mineralbearing aqueous were identified in hydrothermal calcite grains. The ore-forming fluids are normally homogeneous, as indicated by the widespread type 1 inclusions with identical composition. The coexistence of type 1 and type 2 inclusions, showing similar final homogenization temperature but different compositions, indicate that fluid immiscibility did locally take place in both two types of ores. The results of microthermometry and H-O isotopes geochemistry indicate that there are little differences on ore-fluid geochemistry between the auriferous calcite vein-type and disseminated type ores. The oreforming fluids are characterized by medium-low temperatures(157–268 oC) and low salinity(1.6 wt.%–9.9 wt.% NaCl eq.). It is likely to have a metamorphic-dominant mixed source, which could be associated with dehydration and decarbonisation of Lower Permian limestone and Middle–Upper Triassic sandstones during the dynamic metamorphism. The fluid-wallrock interaction played a major role, and the locally occurred fluid-immiscible processes played a subordinate role in gold precipitation. Combined with the regional and ore deposit geology, and ore-fluid geochemistry, we suggest that the Phapon gold deposit is best considered to be a member of the epizonal orogenic deposit class.展开更多
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 ...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.展开更多
The Dayingezhuang gold deposit,hosted mainly by Late Jurassic granitoids on Jiaodong Peninsula in eastern China,contains an estimated 170 t of gold and is one of the largest deposits within the Zhaoping fracture zone....The Dayingezhuang gold deposit,hosted mainly by Late Jurassic granitoids on Jiaodong Peninsula in eastern China,contains an estimated 170 t of gold and is one of the largest deposits within the Zhaoping fracture zone.The orebodies consist of auriferous altered pyrite–sericite–quartz granites that show Jiaojia-type(i.e.,disseminated and veinlet)mineralization.Mineralization and alteration are structurally controlled by the NE-to NNE-striking Linglong detachment fault.The mineralization can be divided into four stages:(K-feldspar)–pyrite–sericite–quartz,quartz–gold–pyrite,quartz–gold–polymetallic sulfide,and quartz–carbonate,with the majority of the gold being produced in the second and third stages.Based on a combination of petrography,microthermometry,and laser Raman spectroscopy,three types of fluid inclusion were identified in the vein minerals:NaCl–H2 O(A-type),CO2–H2 O–NaCl(AC-type),and pure CO2(PC-type).Quartz crystals in veinlets that formed during the first stage contain mainly AC-type fluid inclusions,with rare PC-type inclusions.These fluid inclusions homogenize at temperatures of 251°C–403°C and have low salinities of 2.2–9.4 wt%NaCl equivalent.Quartz crystals that formed in the second and third stages contain all three types of fluid inclusions,with total homogenization temperatures of 216°C–339°C and salinities of 1.8–13.8 wt%NaCl equivalent for the second stage and homogenization temperatures of 195°C–321°C and salinities of 1.4–13.3 wt%NaCl equivalent for the third stage.In contrast,quartz crystals that formed in the fourth stage contains mainly A-type fluid inclusions,with minor occurrences of AC-type inclusions;these inclusions have homogenization temperatures of 106°C–287°C and salinities of 0.5–7.7 wt%NaCl equivalent.Gold in the ore-forming fluids may have changed from Au(HS)0 as the dominant species under acidic conditions and at relatively high temperatures and f O2 in the early stages,to Au(HS)2–under neutral-pH conditions at lower temperatures and f O2 in the later stages.The precipitation of gold and other metals is inferred to be caused by a combination of fluid immiscibility and water–rock interaction.展开更多
基金Supported by Qinghai Provincial Geological Exploration Special Fund Project(No.2023085029KY004).
文摘The Mailong gold deposit is located in the eastern section of the East Kunlun orogenic belt and is one of the recently discovered important gold polymetallic deposits in the Qinhai Gouli region.The primary host rocks of the Mailong gold deposit consist of intermediate-acid intrusive rocks from the Varisian and Indosinian periods,as well as the Precambrian Jinshuikou Group,with mineralization controlled by northeast and northwest faults.The alteration of the host rocks is mainly characterized by silicification,sericitization,chloritization,and carbonatization.Based on the cross-cutting relationships of the veins,the hydrothermal mineralization of the gold deposit can be categorized into three stages:the quartz-pyrite stage,the quartzpolymetallic sulfide stage,and the quartz-carbonate stage.Microthermometry of fluid inclusions indicates that the Mailong gold deposit belongs to a low-density(0.73–0.86 g/cm3),medium-temperature(240–340℃),and medium-salinity(4.01–10.74 wt%NaCl)NaCl-CO2-H2O fluid system.The C-H-O isotopic analysis suggests that the mineralizing fluids is derived from magmatic water,with later contributions from atmospheric precipitation.In-situ S isotopic results indicate that the mineralizing materials mainly derive from igneous rocks.A comprehensive analysis concludes that the Mailong gold deposit is a mesothermal hydrothermal vein-type gold deposit controlled by structural factors.
文摘The Sakay gold deposit in Vientiane,Laos,is located in the Indochina landmass of the southeastern segment of the Tethys orogenic belt,specifically within the Vientiane-Pakse micro-landmass and the Vientiane-Pakse metallogenic belt.This area is regionally significant for the concentration of minerals such as gold,copper,and tin.The host rocks of the deposit are intermediate volcanic lavas and volcanic tuffs,occurring in near-east-west brittle shear structural fractures through hydrothermal filling and metasomatism.The ore exhibits granular texture,subhedral texture,porphyritic texture,and oriented polycrystalline texture,with structural features such as disseminated,vein-like,and cataclastic breccia.The main ore minerals are pyrite,sphalerite,galena,and chalcopyrite,while the gangue minerals are primarily quartz,calcite,and dolomite.Gold is mainly present as included gold or fissure gold within the crystal lattices and microfractures of minerals such as pyrite and sphalerite.Based on mineral assemblages and generation timing,the mineralization can be divided into three stages:arsenopyrite-pyrite-dolomite-quartz(Ⅰ),sphalerite-galena-chalcopyrite-calcite(Ⅱ),and siderite(Ⅲ),with the latter stages often overlaying the former,showing evident cross-cutting and metasomatic phenomena.The surrounding rocks in the mining area are altered,mainly showing silicification,carbonatization,limonitization,sericitization,and chloritization.Preliminary studies suggest that this deposit is a low-temperature hydrothermal gold deposit within a brittle shear zone.
文摘This paper describes a method for estimating the continuation of ore bodies at depth based on concentrationvolume(C-V)fractal modeling of the pyrite thermoelectric coefficient in the Pujon gold deposit,Democratic People’s Republic of Korea.The method is first established using data in the Kumjomdong area,a well-explored brownfield,and it is then applied to estimate the continuation of ore bodies at depth in the Pyongsandok area,a less-explored greenfield.The methodology consists of four steps:(1)3D modeling of ore bodies using surface geological mapping,mining tunnels in different levels,and a borehole dataset;(2)3D modeling of thermoelectricity coefficients from Au-bearing pyrites based on discrete smooth interpolation and C-V fractal techniques;(3)determination of levels used for calculation of the thermoelectric parameter of pyrite by C-V fractal modeling instead of traditional levels;and(4)determination of the thermoelectric parameter vertical gradient of pyrite reflecting the variation characteristics of pyrite thermoelectricity in the Pujon deposit.The results indicate that(1)pyrites in the Pujon deposit are dominantly P-type,and it is not reasonable to use traditional levels to calculate the thermoelectric parameter of pyrite;(2)thresholds determined by C-V fractal modeling can be used as levels to calculate the thermoelectric parameter of pyrite;(3)the thermoelectric parameter vertical gradient of pyrite ranges from 1 to 2 in the Pujon deposit;and(4)ore body Pyongsan No.9 extends 85 m to 235 m downward from the current borehole location.
基金supported by the National Natural Science Foundation of China(No.42302079)Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(No.2024ZD1001301)Geological Surveying Project of CGS(No.DD20230356)。
文摘Recently identified hydrothermal monazite from the Sidaogou deposit in the Liaodong Peninsula,is co-genetic with gold-bearing ore minerals and thus can serve as ideal proxy for dating the gold-mineralization event.Our study effectively solved the dilemma of lack of any accurate age for the Sidaogou deposit.The Sidaogou deposit is hosted mainly by Paleoproterozoic metamorphic rocks of the Liaohe Group,and hydrothermal monazite therein occurs within voids or along micro-fractures in syn-ore pyrite and quartz.First in situ SIMS U-Th-Pb isotope data on this monazite from the Sidaogou deposit yielded an inverse Concordia age of 184±20 Ma,which is much younger than an^(40)Ar-^(39)Ar age of 1858.9±25.4 Ma obtained on muscovite from the host rock(Gaixian Formation),thus supporting a prominent Early Jurassic gold mineralization event in the Wulong gold field,which is distinct from previously established Early Cretaceous gold mineralization,held responsible for the nearby large Wulong gold deposit.Our new findings make it possible,together with previous studies,to formulate a model for the Early Jurassic magmatic-hydrothermal gold system in the area,for which a compressional setting during the westward subduction of the Paleo-Pacific Plate beneath the North China Craton is postulated.
基金financially supported by the National Key Research and Development Program of China(Grant No.2023YFC2906900)Key Research and Development Program of Shandong Province(Grant No.2023CXGC011001)+2 种基金The Taishan Scholars Talent Project(TSTP 20240847)The Open Project of Technology Innovation Center for Deep Gold Resources Exploration and Mining,Ministry of Natural Resources(Grant No.SDK202211,SDK202214)Science and Technology Project of Shandong Bureau of Geology and Mineral Exploration and Development(Grant No.KY202208)。
文摘The Taishang-Shuiwangzhuang gold deposit is located in the southeastern margin of Linglong gold field in the northern part of the Zhaoping Fault metallogenic belt of the Jiaodong gold province-the world’s third-largest gold metallogenic area.Major prospecting breakthroughs have been made at the depth of 600‒2500 m in recent years,with cumulative proven gold resources exceeding 700 t.Based on a large number of exploration data,the main characteristics of the deposit are described in detail,and the spatial coupling relationship between ore-controlling fault and main orebodies is discussed.The main orebodies occur as regular large veins,exhibiting branching and combination,expansion and contraction,and pinch-out and reoccurrence.They extend in a gentle wave pattern along their strikes and dip directions and generally have a pitch direction of NEE and a plunge direction of NEE.As the ore-controlling fault,the Zhaoping Fault has the characteristics of wave-like fluctuation,with its dip angle presenting three steps of steep-slow transition within the depth range of 2500 m.The gold mineralization enrichment area is mainly distributed in the step parts where the fault plane changes from steeply to gently.The ore-forming age,ore-forming fluid and ore-forming material sources and the genesis of the ore deposit are analyzed based on the research results of ore deposit geochemistry.The ore-forming fluids were H_(2)O-CO_(2)-NaCl-type hydrothermal solutions with a medium-low temperature and medium-low salinity.The H-O isotopic characteristics indicate that the fluids in the early ore-forming stage were possibly formed by degassing of basic magma and that meteoric water gradually entered the ore-forming fluids in the late ore-forming stage.The S and Pb isotopes indicate that the ore-forming materials mainly originate from the lower crust and contain a small quantity of mantle-derived components.The comprehensive analysis shows that the Taishang-shuiwangzhuang gold deposit was a typical“Jiaodong type”gold deposit.The strong crust-mantle interactions,large-scale magmatism,and the material exchange arising from the transformation from the ancient lower crust to the juvenile lower crust during the Early Cretaceous provided abundant fluids and material sources for mineralization.Moreover,the detachment faults formed by the rapid magmatic uplift and the extensional tectonism created favorable temperature and pressure conditions and space for fluid accumulation and gold precipitation and mineralization.
基金supported by the Program of the National Natural Science Foundation of China(Nos.41973048,U2006201)the Open Project of State Key Laboratory of Geological Processes and Mineral Resources(No.GPMR202203)+1 种基金the Key R&D Program of Shandong Province(No.2023CXGC011001),the Taishan Scholars.Program(tstp20240847)the Open Project of Shandong Engineering Research Center of Application and Development of Big Data for Deep Gold Exploration(No.SDK202207)。
文摘Since the first discovery of gold deposits on the northeastern margin of the Jiaolai Basin in Shandong Province at the end of the 20^(th) century,seven medium-sized to large/super-large gold deposits have been identified in this region,with cumulative proven gold resources of 223 t.This study reviewed the metallogenic and geochemical characteristics of various gold deposits in this region,examined the sources of their ore-forming fluids and materials,as well as their gold metallogenic epochs and processes,and developed a gold metallogenic model.The gold deposits in this region are governed by both dense fractures and detachment structural systems along basin margins,primarily categorized into the altered rock type and the pyrite-bearing carbonate vein type.The latter type,a recently discovered mineralization type in the Jiaodong Peninsula,enjoys high gold grade,a large scale,and high gold mineral fineness,suggesting considerable prospecting potential.Both types of gold deposits show metallogenic epochs ranging from 116 Ma to 119 Ma.Their ore-forming fluids are identified as a CO_(2)-NaCl-H_(2)O fluid system characterized by moderate to low temperatures,moderate to low salinity,and low density,with the pyrite-bearing carbonate vein-type gold deposits manifesting slightly higher salinity.The C-H-O,S,and Pb isotopes of hydrothermal minerals reveal that the ore-forming fluids and materials are characteristic of crust-mantle mixing.Specifically,they were derived from mantle fluids in the early stages,mixed with stratum water and meteoric water in the later stages for mineralization.The gold metallogenic process is identified as follows:During the Early Cretaceous,the subduction of the Pacific Plate and the destruction of the North China Craton led to asthenospheric upwelling.The resulting fluids,after metasomatizing the enriched mantle,differentiated and evolved into C-H-O ore-bearing fluids,which were then mixed with crustal fluids.The mixed fluids migrated to the shallow crust,where they mingled with stratum water and meteoric water.Then,the fluids underwent unloading and final mineralization in detachment fault tectonic systems on basin margins.Due to differences in mixed crustal materials or the surrounding rocks involved in water-rock interactions,altered rock-and pyrite-bearing carbonate vein-type gold deposits were formed in acidic and alkaline fluid environments,respectively.
基金Project(20091100704)supported by the Special Funds for Scientific Research of Land and Natural Resources,ChinaProject(2015CX008)supported by the Innovation Driven Plan of Central South University,China
文摘Dongguashan deposit is a large porphyry-skarn copper（gold） deposit in Tongling ore district. The Qingshanjiao intermediate acid intrusion of Yanshanian had a direct genetic relationship with mineralization. The magma origin, rock-forming dynamic background and rock-forming process were studied, and the rock-forming mechanism of Qingshanjiao intrusion was discussed, based on geological characteristics, detailed observation of petrography and systematic investigation of petrochemistry, trace elements and REE geochemistry characteristics of Qingshanjiao intrusion. The results show that Qingshanjiao rock body belongs to high-K calc-alkaline series with higher LREE elements, Th, Rb and Sr abundance, but depleted in HREE elements, Ba, Nb and Ta. The primary magma originated from the mantle-crust mixtures which were caused by basaltic magma of mantle mixing with syenite magma of partial melting of the lower crust, and the formation environment of Qingshanjiao intrusion was emplaced in the transitional environment from compression to extension. The Harker diagram and hybrid structures of plagioclase and potassium feldspar indicate that the fractional crystallization occurred in the process of magmatic evolution. The petrochemistry, trace elements and REE geochemistry characteristics indicate that the magma was contaminated by crustal material during the rock-forming. These results suggested that the Qingshanjiao intrusion was formed by fractional crystallization and assimilation and hybridization of mantle-crust magma in the transitional environment from compression to extensional.
基金financially supported by the National Natural Science Foundation of China(Grant No.41230311)the National Science and Technology Support Program(Grant No.2011BAB04B09)+1 种基金the Geological Investigation Work Project of China Geological Survey(Grant No.12120114034901)111 Project of China(Grant No.B07011)
文摘The Jiaodong gold deposits are currently the most important gold resources（with Au reserves of〉4000 t） in China,and the leading gold-producing country globally（with Au production of ～428 t in2013）.Jiaodong is also considered as perhaps the only world-class to giant gold accumulation on the planet where relatively young gold ores（ca.130-120 Ma） were deposited in rocks that are 2 Ga older.The Xincheng world-class high-grade gold deposit,with a proven reserve of 〉200 t gold,is one of the largest deposits in the giant gold province of the Jiaodong Peninsula.It is located in the northwestern part of the jiaobei Uplift,and hosted by ca.132-123 Ma Xincheng quartz monzonites and monzogranites.Ore zones are structurally controlled by the NE-trending and NW-dipping Jiaojia Fault and subsidiary faults,and are mainly restricted to the footwall of the fault.The dominant disseminated- and stockworkstyle ores are associated with strong sericitization,silicification,sulfidation and K-feldspathization,and minor carbonate wallrock alteration halos.The four mineralization stages are pyrite-quartz-sericite（stage 1）,quartz-pyrite（stage 2）,quartz-polysulfide（stage 3） and quartz-carbonate（stage 4）.Gold occurs dominantly as electrum,with lesser amounts of sulfide-hosted native gold and rare native silver and argentite,normally associated with pyrite,chalcopyrite,galena and sphalerite：the latter with proven resources of about 105 t Ag,713 t Cu,and 5100 t S.There are three types of ore-related fluid inclusions：type 1 aqueous-carbonate（H2O-CO2）,type 2aqueous（liquid H2O＋vapor H2O）,and type 3 CO2（liquid CO2 and vapor CO2） inclusions.Homogenization temperatures range from 221 to 304℃ for type 1 inclusions,with salinities of 2.4-13.3 wt.%NaCl eq.,and bulk densities of 0.858-1.022 g/cm～3.The δ～（34）S（CDT） values of hydrothermal sulfides are 4.3-10.6‰and δ～（18）O values of hydrothermal quartz have a median value of 13.0‰.δD values of fluid inclusions in hydrothermal quartz have a median value of-75‰.Calculated δ～（18）Owater has a median value of 5.2‰.The timing of gold mineralization at the Xincheng gold deposit is younger than 123±1 Ma,and likely between 120.9 and 119.9 Ma.A minerals system genetic model for the probable epizonal orogenic Xincheng deposit suggests an initial medium temperature,CO2-rich,and low salinity H2O-CO2 deeply sourced metamorphic ore fluid associated with dehydration and decarbonization of subducting Paleo-Pacific lithosphere.The Jiaojia Fault constrained the migration of ore-forming fluids and metals at the brittle-ductile transition.Fluid immiscibility,caused by episodic pressure drops,led to significant high-grade gold deposition in the giant Xincheng gold deposit.
基金supported by the National Natural Science Foundation of China (Nos. 40672064, 40572063)the 973-Project (No. 2006CB403506)Changjiang Scholars and Innovative Research Team in University and 111 Project of the Ministry of Education, China (No. B07011)
文摘The recently discovered Damoqujia （大磨曲家） gold deposit is a large shear zone-hosted gold deposit of disseminated sulphides located in the north of the Zhaoping （招平） fault zone, Jiaodong （胶东） gold province, China. In order to distinguish the temperature range of cluster inclusions from different mineralization stages and measure their compositions, 16 fluid inclusions and 5 isotopic geochemistry samples were collected for this study. Corresponding to different mineralization stages, the multirange peaks of quartz decrepitation temperature （250-270, 310-360 and 380-430℃） indicate that the activity of ore-forming fluids is characterized by multistage. The ore-forming fluids were predominantly of high-temperature fluid system （HTFS） by CO2-rich, and SO4^2--K^＋ type magmatic fluid during the early stage of mineralization and were subsequently affected by low-temperature fluid system （LTFS） of CH4-rich, and Cl^--Na^＋/Ca^2＋ type meteoric fluid during the late stage of mineralization. Gold is transferred by Au-HS^- complex in the HTFS, and Au-Cl^- complex can be more important in the LTFS. The transition of fluids from deeper to shallow environments results in mixing between the HTFS and LTFS, which might be one of the most key reasons for gold precipitation and large-scale mineralization. The ore-forming fluids are characterized by high-temperature, strong-activity, and superimposed mineralization, so that there is a great probability of forming large and rich ore deposit in the Damoqujia gold deposit. The main bodies are preserved and extend toward deeper parts, thereby suggesting a great potential in future.
基金funded by Talent Award under the 1000 Plan Project from the Chinese Government
文摘It is quite evident that it is not anomalous metal transport,nor unique depositional conditions,nor any single factor at the deposit scale,that dictates whether a mineral deposit becomes a giant or not.A hierarchical approach thus is required to progressively examine controlling parameters at successively decreasing scales in the total mineral system to understand the location of giant gold deposits in non-arc environments.For giant orogenic,intrusion-related gold systems（IRGS） and Carlin-type gold deposits and iron oxide-copper-gold（IOCG） deposits,there are common factors among all of these at the lithospheric to crustal scale.All are sited in giant gold provinces controlled by complex fundamental fault or shear zones that follow craton margins or,in the case of most Phanerozoic orogenic giants,define the primary suture zones between tectonic terranes.Giant provinces of IRGS,IOCG,and Carlin-type deposits require melting of metasomatized lithosphere beneath craton margins with ascent of hybrid lamprophyric to granitic magmas and associated heat flux to generate the giant province.The IRGS and IOCG deposits require direct exsolution of volatile-rich magmatic-hydrothermal fluids,whereas the association of such melts with Carlin-type ores is more indirect and enigmatic.Giant orogenic gold provinces show no direct relationship to such magmatism.forming from metamorphic fluids,but show an indirect relationship to lamprophyres that reflect the mantle connectivity of controlling first-order structures.In contrast to their province scale similarities,the different giant gold deposit styles show contrasting critical controls at the district to deposit scale.For orogenic gold deposits,the giants appear to have formed by conjunction of a greater number of parameters to those that control smaller deposits,with resultant geometrical and lithostratigraphic complexity as a guide to their location.There are few giant IRGS due to their inferior fluid-flux systems relative to orogenic gold deposits,and those few giants are essentially preservational exceptions.Many Carlin-type deposits are giants due to the exceptional conjunction of both structural and lithological parameters that caused reactive and permeable rocks,enriched in syngenetic gold,to be located below an impermeable cap along antiformal ＂trends＂.Hydrocarbons probably played an important role in concentrating metal.The supergiant Post-Betze deposit has additional ore zones in strain heterogeneities surrounding the pre-gold Goldstrike stock.All unequivocal IOCG deposits are giant or near-giant deposits in terms of gold-equivalent resources,partly due to economic factors for this relatively poorly understood,low Cu-Au grade deposit type.The supergiant Olympic Dam deposit,the most shallowly formed deposit among the larger IOCGs,probably owes its origin to eruption of volatile-rich hybrid magma at surface,with formation of a large maar and intense and widespread brecciation,alteration and Cu-Au-U deposition in a huge rock volume.
文摘The superlarge Baguamiao, large Liba and Xiaogouli gold deposits represent three typical gold deposits different from the Carlin type in the western Qinling Orogenic Belt. Based on Ar-Ar dating of quartz from ores, U-Pb dating of single zircon from granite, tracing of H and O isotopes and studies on the mineralogy and texture of spots and bleached alteration developed in wall rocks, this paper focuses the relations between gold deposits and granite to clarify the origin of gold deposits and the metallogenesis in the tectonic evolution of the Qinling Orogenic Belt. The comprehensive studies show that the age of the granite (148.1-244 Ma) is identical with that of the gold deposits (131.91-232.56 Ma). It is suggested that the granite has close temporal, spatial and genetic relationship with the gold deposits. The granite provides a heat source, water source and considerable amount of ore-forming material. Finally, it is concluded that the orogeny by collision, emplacement of the granite and positioning of the gold deposits represent a successive process. Both the granite and gold deposits resulted from the syn-orogeny and post-orogeny tectonic evolution.
基金financial support provided by the National Natural Science Foundation of China (Grant No. 41702070)
文摘With very few exceptions, orogenic gold deposits formed in subduction-related tectonic settings in accretionary to collisional orogenic belts from Archean to Tertiary times. Their genesis, including metal and fluid source, fluid pathways, depositional mechanisms, and timing relative to regional structural and metamorphic events, continues to be controversial. However, there is now general agreement that these deposits formed from metamorphic fluids, either from metamorphism of intra-basinal rock sequences or de-volatilization of a subducted sediment wedge, during a change from a compressional to transpressional, less commonly transtensional, stress regime, prior to orogenic collapse. In the case of Archean and Paleoproterozoic deposits, the formation of orogenic gold deposits was one of the last events prior to cratonization. The late timing of orogenic gold deposits within the structural evolution of the host orogen implies that any earlier structures may be mineralized and that the current structural geometry of the gold deposits is equivalent to that at the time of their formation provided that there has been no significant post-gold orogenic overprint. Within the host volcano-sedimentary sequences at the province scale, world-class orogenic gold deposits are most commonly located in second-order structures adjacent to crustal scale faults and shear zones, representing the first-order ore-forming fluid pathways, and whose deep lithospheric connection is marked by lamprophyre intrusions which, however, have no direct genetic association with gold deposition. More specifically, the gold deposits are located adjacent to ～10°-25° district-scale jogs in these crustal-scale faults. These jogs are commonly the site of arrays of ～70° cross faults that accommodate the bending of the more rigid components, for example volcanic rocks and intrusive sills, of the host belts. Rotation of blocks between these accommodation faults causes failure of more competent units and/or reactivation and dilation of pre-existing structures, leading to deposit-scale focussing of ore-fluid and gold deposition.Anticlinal or antiformal fold hinges, particularly those of ＇locked-up＇ folds with ～30° apical angles and overturned back limbs, represent sites of brittle-ductile rock failure and provide one of the more robust parameters for location of orogenic gold deposits.In orogenic belts with abundant pre-gold granitic intrusions, particularly Precambrian granitegreenstone terranes, the boundaries between the rigid granitic bodies and more ductile greenstone sequences are commonly sites of heterogeneous stress and inhomogeneous strain. Thus, contacts between granitic intrusions and volcano-sedimentary sequences are common sites of ore-fluid infiltration and gold deposition. For orogenic gold deposits at deeper crustal levels, ore-forming fluids are commonly focused along strain gradients between more compressional zones where volcano-sedimentary sequences are thinned and relatively more extensional zones where they are thickened. World-class orogenic gold deposits are commonly located in the deformed volcano-sedimentary sequences in such strain gradients adjacent to triple-point junctions defined by the granitic intrusions, or along the zones of assembly of micro-blocks on a regional scale. These repetitive province to district-scale geometrical patterns of structures within the orogenic belts are clearly critical parameters in geology-based exploration targeting for orogenic gold deposits.
基金jointly supported by the National Key Research and Development Project of China (Grant No.2016YFC0600307)the National Key Basic Research Development Program (973 Program+1 种基金 Grant No.2015CB452606)the fundamental research funds of university teachers(No.53200959708 and No.2-9-2018-126)
文摘Orogenic disseminated and Carlin gold deposits share much similarity in alteration and mineralization.The disseminated orogenic Zhenyuan Au deposit along the Ailaoshan shear zone,southeastern Tibet,was selected to clarify their difference.The alteration and mineralization from the different lithologies,including meta-quartz sandstone,carbonaceous slate,meta-(ultra)mafic rock,quartz porphyry and lamprophyre were researched.According to the mineral assemblage and replacement relationship in all types of host rocks,two reactions show general control on gold deposition:(1) replacement of earlier magnetite by pyrite and carbonaceous material;(2) alteration of biotite and phlogopite phenocrysts in quartz porphyry and lamprophyre into dolomite/ankerite and sericite.Despite the lamprophyre is volumetrically minor and much less fractured than other host rocks,it contains a large portion of Au reserve,indicating that the chemically active lithology has played a more important role in gold precipitation compared to structure.LA-ICP-MS analysis shows that Au mainly occurs as invisible gold in fine-grained pyrite disseminated in the host rocks,with Au content reaching to 258.95 ppm.The diagenetic core of pyrite in meta-quartz sandstone enriched in Co,Ni,Mo,Ag and Hg is wrapped by hydrothermal pyrite enriched in Cu,As,Sb,Au,Tl,Pb and Bi.Different host rock lithology has much impact on the alteration and mineralization features.Carbonate and sericite in altered lamprophyre show they have higher Mg than those developed in other of host rocks denoting that the carbonate and sericite incorporated Mg from phlogopite phenocrysts in the primary lamprophyre during alteration.The ore fluid activated the diagenetic pyrite in meta-quartz sandstone leading the hydrothermal pyrite enriched in Cu,Mo,Ag,Sb,Te,Hg,Tl,Pb and Bi,but the hydrothermal pyrite in meta-(ultra)mafic rock is enriched in Co and Ni as the meta-(ultra)mafic rock host rock contain high content of Co and Ni.However,Au and As shear similar range in both types of host rocks indicating that these two elements most likely come from the deep source fluid rather than the host rocks.It was shown in the disseminated orogenic gold deposit that similar hydrothermal alteration with mineral assemblage of carbonate (mainly dolomite and ankerite),sericite,pyrite and arsenopyrite develops in all types of host rocks.This is different from the Nevada Carlin type,in which alteration is mainly dissolution and silicification of carbonate host rock.On the other hand,Au mainly occur as invisible gold in both disseminated orogenic and Carlin gold deposits.
文摘In the light of field investigation, microscopic study, X\|ray phase analysis and mineral infrared spectral analysis, it is considered that laumontitization is of extensive occurrence in the Axi gold orefield. The development of laumontitization and its relationship to mineralization show that the laumontitization appeared mainly at the top of and in the periphery of orebodies, and occurred at the edge of the epithermal system or at the late stage of epithermal system evolution. Therefore, laumontitization can be used as an exploration indicator of epithermal gold deposits. The fluids responsible for laumontitization in the Axi gold orefield are similar to those producing hot spring\|type gold deposits or those from modern geothermal fields. Epithermal mineralization of the Axi gold deposit was dated at Carboniferous, indicating that the West Tianshan of China is a region favorable to epithermal\|type gold mineralization and preservation. Hence the West Tianshan of China is a target area for exploring epithermal gold deposits.
基金This paper is supported by the National Natural Science Foundation of China （Grant Nos. 40572063 and 40272051）；the Fostering Plan Fund for Trans-Century Excellent Talents and the Project 111 （No. B07011）.
文摘The Shangzhuang altered-rock type gold ore deposit is located in the middle segment of and controlled by the Wang＇ershan fault zone in the northwestern part of the Jiaodong gold province, China. The deformation evolution, the structure of strain and stress fields and its ore-controlling effect in the Shangzhuang deposit are discussed in this paper. It is revealed that the deformation evolution has mainly undergone four phases： the early ductile deformation, the second NE-striking horizontal simple shear, the third NE-striking compression-shear and the final NW-striking compression. The mineralization happened during the third stage in which the maximum principal stress gradually transited from NE to NW. The 3-D numerical simulations of the stress field show that, on the condition that the maximum principal stress is NE-striking, the fracture development in the fault zone is favored, while when the maximum principal stress is NW-striking, the fault zone is relatively extensional and it is suitable for the influx and emplacement of ore-forming fluids. The compression-shear strain field during the mineralization is characterized by the λ-type structure, the positive flower structure, etc. Orebodies are mostly equidistantly located in the dilatational spaces, which are distributed in the integral compressional circumstances. And the dilatational spaces are developed where the fault attitude changes or shear joint systems develop. In the overall compression-shear stress field, the strain field bears self-similarity at multiple scales, including the orebody, ore deposit and orefield. The selfsimilarity of the structure comprises the subequidistant distribution of fractures at the same scale and the similar shape of the fractures at various scales. Yet, due to the special geological structure, the orebodies are mostly located in the hanging wall in the Shangzhuang deposit, which is different from most deposits in the Jiaodong gold province. Analyses of the ore-controlling stress and strain fields in the deposit provide an important basis for deposit seeking.
基金supported by several grantsfrom DAAD,DFG(Wo 489/15-1,15-2KL 692/11-1,11-2)+1 种基金NSERC,NHM CERCAMS,IGCP(IGCP-473)the IGCP project 592 sponsored by IUGS and UNESCO
文摘The Muruntau gold deposit in the Central Kyzylkum,Uzbekistan is one of the largest single gold deposits worldwide.Data available from the literature are reviewed with the aim to（1） integrate the present knowledge on this unique deposit from Russian and English literature;（2） show the considerable progress made in the understanding of the genesis of the Muruntau deposit during the last decades;and（3） point to problems still open for future research.Deposit formation occurred through a multi-stage process involving sedimentation,regional metamorphism including thrusting,magmatism with formation of hornfels aureoles and several stages of hydrothermal activity.According to recent knowledge,synsedimentary or pure metamorphic formation of gold mineralization seems unlikely.The role of granite magmatism occurring roughly within the same time interval as the main hydrothermal gold precipitation remains uncertain.There are no signs of interaction of matter between the magma（s） and the hydrothermal system（s）.On the other hand,there was an intense,high-temperature（above 400 ℃）fluid- wall rock interaction resulting in the formation of gold-bearing,cone-like stockworks with veins,veinlets and gold-bearing metasomatites.Several chemical and isotope indicators hint at an involvement of lower-crustal or mantle-related sources as well as of surface waters in ore formation.Deposit formation through brecciation involving explosion,hydrothermal or tectonic breccias might explain these data.Further investigations on breccia formation as well as on the exact timing of relevant sedimentary,metamorphic,magmatic and hydrothermal events are recommended.
基金the National Natural Science Foundation of China(Nos.41072041,40821002) for financial support
文摘Mineral assemblages formed during hydrothermal alteration reflect the geochemical composition of ore-forming fluids. Gold is mainly transported in solution as Au-CI and Au-S complexes. The change of physicochemical conditions such as temperature, pressure, oxygen fugacity, and sulfur fugacity are effective mechanisms for gold precipitation. Gold tends to be concentrated in the vapor phase of fluids at high temperatures and pressures. Au-As and Au-Sb associations are common in gold deposit. Native antimony and/or arsenic -- native gold assemblages may precipitate from hydrothermal fluids with low sulfur fugacity. Hydrothermal fluids forming epithermal gold deposits are Au-saturated in most cases, whereas fluids of Carlin-type are Au-undersaturated. Quasi-steady As-bearing pyrite extracts solid solution Au from hydrothermal fluids through absorption. The capability of As-bearing pyrite to absorb An from under-saturated fluid is the key to the formation of large-scale Carlin-type deposits. With increasing new data, studies on the geochemistry of gold deposits can be used to trace the origin of ore-forming fluids, the source of gold, and the transporting form of Au and other ore-forming elements, such as Si, S, F, Cl, As and Ag.
基金financially supported by the China Geological Survey Project (No. 121201010000150013)
文摘The Phapon gold deposit, located in northern Laos, is a unique large-scale gold deposit in Luang Prabang-Loei metallogenic belt. It is hosted in the Lower Permian limestone and controlled by a NE-trending ductile-brittle fault system. There are three types of primary ore including auriferous calcite vein type, disseminated type, and breccia type, and the first two are important in the Phapon gold deposit. Based on fluid inclusion petrography and microthermometry, three types of primary fluid inclusions including type 1 liquid-rich aqueous, type 2 vapor-rich aqueous and type 3 daughter mineralbearing aqueous were identified in hydrothermal calcite grains. The ore-forming fluids are normally homogeneous, as indicated by the widespread type 1 inclusions with identical composition. The coexistence of type 1 and type 2 inclusions, showing similar final homogenization temperature but different compositions, indicate that fluid immiscibility did locally take place in both two types of ores. The results of microthermometry and H-O isotopes geochemistry indicate that there are little differences on ore-fluid geochemistry between the auriferous calcite vein-type and disseminated type ores. The oreforming fluids are characterized by medium-low temperatures(157–268 oC) and low salinity(1.6 wt.%–9.9 wt.% NaCl eq.). It is likely to have a metamorphic-dominant mixed source, which could be associated with dehydration and decarbonisation of Lower Permian limestone and Middle–Upper Triassic sandstones during the dynamic metamorphism. The fluid-wallrock interaction played a major role, and the locally occurred fluid-immiscible processes played a subordinate role in gold precipitation. Combined with the regional and ore deposit geology, and ore-fluid geochemistry, we suggest that the Phapon gold deposit is best considered to be a member of the epizonal orogenic deposit class.
文摘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.
基金jointly supported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant no.XDA20070304)the China Geological Survey(DD20160024 and grant no.121201102000150011)+1 种基金the China Postdoctoral Science Foundation funded project(Grant no.2016M590119)the National Natural Science Foundation of China(Grant no.41320104004,41602084)
文摘The Dayingezhuang gold deposit,hosted mainly by Late Jurassic granitoids on Jiaodong Peninsula in eastern China,contains an estimated 170 t of gold and is one of the largest deposits within the Zhaoping fracture zone.The orebodies consist of auriferous altered pyrite–sericite–quartz granites that show Jiaojia-type(i.e.,disseminated and veinlet)mineralization.Mineralization and alteration are structurally controlled by the NE-to NNE-striking Linglong detachment fault.The mineralization can be divided into four stages:(K-feldspar)–pyrite–sericite–quartz,quartz–gold–pyrite,quartz–gold–polymetallic sulfide,and quartz–carbonate,with the majority of the gold being produced in the second and third stages.Based on a combination of petrography,microthermometry,and laser Raman spectroscopy,three types of fluid inclusion were identified in the vein minerals:NaCl–H2 O(A-type),CO2–H2 O–NaCl(AC-type),and pure CO2(PC-type).Quartz crystals in veinlets that formed during the first stage contain mainly AC-type fluid inclusions,with rare PC-type inclusions.These fluid inclusions homogenize at temperatures of 251°C–403°C and have low salinities of 2.2–9.4 wt%NaCl equivalent.Quartz crystals that formed in the second and third stages contain all three types of fluid inclusions,with total homogenization temperatures of 216°C–339°C and salinities of 1.8–13.8 wt%NaCl equivalent for the second stage and homogenization temperatures of 195°C–321°C and salinities of 1.4–13.3 wt%NaCl equivalent for the third stage.In contrast,quartz crystals that formed in the fourth stage contains mainly A-type fluid inclusions,with minor occurrences of AC-type inclusions;these inclusions have homogenization temperatures of 106°C–287°C and salinities of 0.5–7.7 wt%NaCl equivalent.Gold in the ore-forming fluids may have changed from Au(HS)0 as the dominant species under acidic conditions and at relatively high temperatures and f O2 in the early stages,to Au(HS)2–under neutral-pH conditions at lower temperatures and f O2 in the later stages.The precipitation of gold and other metals is inferred to be caused by a combination of fluid immiscibility and water–rock interaction.
