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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(H_2O-CO_2),type 2aqueous(liquid H_2O+vapor H_2O),and type 3 CO_2(liquid CO_2 and vapor CO_2) 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,CO_2-rich,and low salinity H_2O-CO_2 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.
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 in 2013) .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 Gaonger. 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 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 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 (H 2 O-CO 2), type 2aqueous (liquid H 2 O + vapor H 2 O), and type 3 CO 2 (liquid CO 2 and vapor CO 2) inclusions. Homogenization temperatures range from 221 to 304 ° C 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 med ian valueof-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, CO 2 -rich, and low salinity H 2 O-CO 2 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.