Geological,Geochemical Characteristics And Genesis Of The Jinshuiquan Gold Deposit In The East Junggar,Xinjiang

The Jinshuiquan gold deposit is located in the Kalamaili metallogenic belt in the East Junggar,Xinjiang Province,between the Kalamaili deep fault and the major disruption of Qingshui-Sujiquan.So far,predecessors only briefly introduced the geological characteristics of the Jinshuiquan gold deposit.However,studies focused on the feature and source of ore-forming fluid,metallogenic physico-chemical conditions,metallogenic age and ore genesis have not been well discussed.The detailed laboratory study based on field geological survey is carried out,including rock-mineral microscopic identification,fluid inclusion test,stable isotope analysis,wall rock alteration element migration and hydrothermal zircon geochronology for the Jinshuiquan gold deposit.The genetic type as well as the metallogenic model of the deposit is determined and preliminarily established in the study.The deposit occurs in a suite of low greenschist facies sedimentary metamorphic rocks of the Middle Devonian strata.The ore bearing rocks are tuff,tuffaceous sandstone and quartz magnesite.Ore deposit is controlled by secondary left slip faults running NWW or NW directions in the Kalamaili fault zone.Hydrothermal mineralization is divided into 3stages in which the second stage is gold metallogenic stage,whose strike is NWW and dip is NE.Ore from the Jinshuiquan gold deposit are classified into two types:quartz vein type and altered rock type.The latter is more common deep in the ore bodies.Ore textures consist of crystalline texture,metasomatic texture and pressure texture.Meanwhile,ore structures mainly contain filling ore structure and metasomatic ore structure.The metallic minerals are basicly pyrite and arsenopyrite,followed by native gold,sphalerite,chalcopyrite etc.The nonmetallic minerals are mainly quartz,calcite,magnesite,talc and sericite,followed by chlorite,epidote etc.The patrical size of sulfide mineral is fine,meanwhile the total content is less than 5%.Gold grade is in a great range,up to 20 g/t.The percentage of native gold is high,the range is 883⁹09.Ore bearing hydrothermal fluids cause different metasomatic alteration of tuff and ultrabasic rocks.The alteration has a certain zonation.The alteration types of the tuff rock are mainly silicification,pyrite mineralization,arsenopyrification,sericite and chloritization,while the alteration types of ultrabasic rock are mainly silicification,talcization,magnesitization,serpentinization etc.Water-rock reaction between ore-forming fluid and tuff rock as well as a large mount of CO₂ escaping from ore-forming fluid during talcization and magnesitization of ultrabasic rocks may be the main mechanism of gold precipitation of the Jinshuiquan gold deposit.Fluid inclusion analyses indicate that metallogenic fluid belong to the system H₂O-CO₂occurred at moderate-high temperature,low salinity and moderate density.The hydrogen and oxygen isotope composition of ore-forming fluid showed the characteristics of metamorphic water.LA-ICP-MS U-Pb dating on hydrothermal zircons gave a weighted average²⁰⁶Pb/²³⁸U age of 314.9±3.2 Ma,indicating that the Jinshuiquan gold deposit was formed in Late Carboniferous epoch and this epoch is an important gold mineralization period in the Kalamaili gold belt.In conclusion,characteristics of the Jinshuiquan gold deposit exhibited in metallogenic background,geology,ore-control structure,host rock,wall rock alteration,mineral paragenesis combination,metallogenic time,the feature and source of ore-forming fluid are all consistent with those of orogenic gold deposit origins,indicated that the Jinshuiquan gold deposit is a typical orogenic gold deposit.