The Qilishan gold deposit is located in the southern Zhaolai gold ore belt in the northwestern Jiaodong region.A total of seven gold ore bodies have been found in the mining area.Linglong gneissic biotite granite and ...The Qilishan gold deposit is located in the southern Zhaolai gold ore belt in the northwestern Jiaodong region.A total of seven gold ore bodies have been found in the mining area.Linglong gneissic biotite granite and the NE trending Lingbei fracture control the output and distribution of the gold deposit.The ore bodies with veined or irregular shape occur in the structural alteration zone.The ore bodies of different sizes are NE trending and SE dipping.The constituent minerals of the ores mainly include pyrite,chalcopyrite,native gold,electrum,argentite,matildite,hematite,quartz and calcite.The ores are characterized by metasomatic dissolution structure,as well as veined and brecciated structures.The ore-forming process is divided into four stages,namely quartz-,pyrite-,polymetallic-and carbonate stages.Study on fluid inclusion shows that the deposit is composed of gas-liquid two-phase inclusions （Ⅰ） and three-phase inclusions containing CO2 （Ⅱ）,and that the former dominates.The homogenization temperature is 259.6℃-373.7℃ ; the salinity of three-phase inclusions containing CO2is 5.77%-9.84% （NaCl） ; the salinity of gas-liquid two-phase inclusions is 6.58%-8.54% （NaCl） ; and the estimated ore-forming pressure is 55.2-82.2 MPa.According to the nonlinear relationship between the depth and pressure of the fluid in the fracture zone,the ore-forming depth of the Qilishan gold deposit is calculated as 5.95-7.14 km.It is preliminarily determined that the deposit is a mesophilic and hypothermal gold deposit.展开更多
Large-scale gold mineralization during the Early Cretaceous is identified in the Jiao-dong Peninsula of China.Sources of ore-forming fluids remain debated.We study the Qilishan gold deposit in the northwestern Jiaodon...Large-scale gold mineralization during the Early Cretaceous is identified in the Jiao-dong Peninsula of China.Sources of ore-forming fluids remain debated.We study the Qilishan gold deposit in the northwestern Jiaodong Peninsula with detailed mineralogical observation and in-situ sulfur isotope analyses,in order to reveal the gold occurrence and the origin of ore-forming fluids.The Qilishan gold deposit is mainly clastic altered rock-type in mineralization,and ore minerals are visible native gold,electrum,pyrite,chalcopyrite and galena,gangue minerals as quartz,sericite and calcite.The gold occurrence includes inclusion and intergranular types,formed within pyrites and chalcopy-rites and along their fissures.In-situ sulfur isotope analysis of gold-bearing sulfides suggests that the Qilishan deposit is enriched in heavy sulfur,withδ34S values mainly from+8.0‰to+12.0‰.δ34S val-ues increase gradually with the fluid evolution from the early to late stages,which is interpreted to be related to the loss of sulfur via sulfide precipitation.The crystallization of sulfides from hydrothermal fluids may have triggered the instability of Au(HS)2,and finally led to gold precipitation.Combined with sulfur isotope compositions of other gold deposits(n=43)and wall-rocks in the Jiaodong Peninsu-la,it is proposed that the ore-forming fluids were probably not directly originated from metamorphic wall-rocks(e.g.,Jiaodong Group).Moreover,the relatively long time interval rules out the possibility that the gold mineralization(ca.120 Ma)was associated with granitic magma activities(mostly 160-150 Ma).Possible ore genesis scenario is that,long-term subduction of slabs(e.g.,the Paleo-Pacific)with gold-enriched pyritic materials and crustal sedimentary rocks resulted in both high Au contents and positiveδ34S values of sulfur in the lithospheric mantle below the North China Craton.Subse-quently,devolatilization of the metasomatized mantle produced auriferous fluids that migrated up-ward along translithospheric fault systems,and gold finally precipitated in favorable structural posi-tions,generating the world-class Jiaodong deposits in the Early Cretaceous.展开更多
基金Supported by Project of Alternative Resources Prospecting in Crisis Mines(No.200623018)
文摘The Qilishan gold deposit is located in the southern Zhaolai gold ore belt in the northwestern Jiaodong region.A total of seven gold ore bodies have been found in the mining area.Linglong gneissic biotite granite and the NE trending Lingbei fracture control the output and distribution of the gold deposit.The ore bodies with veined or irregular shape occur in the structural alteration zone.The ore bodies of different sizes are NE trending and SE dipping.The constituent minerals of the ores mainly include pyrite,chalcopyrite,native gold,electrum,argentite,matildite,hematite,quartz and calcite.The ores are characterized by metasomatic dissolution structure,as well as veined and brecciated structures.The ore-forming process is divided into four stages,namely quartz-,pyrite-,polymetallic-and carbonate stages.Study on fluid inclusion shows that the deposit is composed of gas-liquid two-phase inclusions （Ⅰ） and three-phase inclusions containing CO2 （Ⅱ）,and that the former dominates.The homogenization temperature is 259.6℃-373.7℃ ; the salinity of three-phase inclusions containing CO2is 5.77%-9.84% （NaCl） ; the salinity of gas-liquid two-phase inclusions is 6.58%-8.54% （NaCl） ; and the estimated ore-forming pressure is 55.2-82.2 MPa.According to the nonlinear relationship between the depth and pressure of the fluid in the fracture zone,the ore-forming depth of the Qilishan gold deposit is calculated as 5.95-7.14 km.It is preliminarily determined that the deposit is a mesophilic and hypothermal gold deposit.
基金We thank constructive suggestions from editors and anonymousreviewers.This research was supported by the NationalKey R&D Plan(No.2018YFC0603801)the Open ResearchProject from the State Key Laboratory of Geological Processesand Mineral Resources,China University of Geosciences(No.GPMR201816)+3 种基金Fundamental Research Funds for the CentralPublic Welfare Research Institutes(Nos.KK1914,KK2013)the National Natural Science Foundation of China(Nos.41911530106,41772084)the Chinese Geological Survey Program(Nos.DD20160055,DD20190379)Key Laboratory ofRegional Geology and Mineralization,Hebei GEO University(No.HGU-RGMKF192).
文摘Large-scale gold mineralization during the Early Cretaceous is identified in the Jiao-dong Peninsula of China.Sources of ore-forming fluids remain debated.We study the Qilishan gold deposit in the northwestern Jiaodong Peninsula with detailed mineralogical observation and in-situ sulfur isotope analyses,in order to reveal the gold occurrence and the origin of ore-forming fluids.The Qilishan gold deposit is mainly clastic altered rock-type in mineralization,and ore minerals are visible native gold,electrum,pyrite,chalcopyrite and galena,gangue minerals as quartz,sericite and calcite.The gold occurrence includes inclusion and intergranular types,formed within pyrites and chalcopy-rites and along their fissures.In-situ sulfur isotope analysis of gold-bearing sulfides suggests that the Qilishan deposit is enriched in heavy sulfur,withδ34S values mainly from+8.0‰to+12.0‰.δ34S val-ues increase gradually with the fluid evolution from the early to late stages,which is interpreted to be related to the loss of sulfur via sulfide precipitation.The crystallization of sulfides from hydrothermal fluids may have triggered the instability of Au(HS)2,and finally led to gold precipitation.Combined with sulfur isotope compositions of other gold deposits(n=43)and wall-rocks in the Jiaodong Peninsu-la,it is proposed that the ore-forming fluids were probably not directly originated from metamorphic wall-rocks(e.g.,Jiaodong Group).Moreover,the relatively long time interval rules out the possibility that the gold mineralization(ca.120 Ma)was associated with granitic magma activities(mostly 160-150 Ma).Possible ore genesis scenario is that,long-term subduction of slabs(e.g.,the Paleo-Pacific)with gold-enriched pyritic materials and crustal sedimentary rocks resulted in both high Au contents and positiveδ34S values of sulfur in the lithospheric mantle below the North China Craton.Subse-quently,devolatilization of the metasomatized mantle produced auriferous fluids that migrated up-ward along translithospheric fault systems,and gold finally precipitated in favorable structural posi-tions,generating the world-class Jiaodong deposits in the Early Cretaceous.
