Metallogenic Characteristics And Prospecting Direction Of The Luyuan Gold Deposit In East Junggar,Xinjiang

The Luyuan gold deposit is located at the Qiongheba ore cluster area in the eastern segment of Yemaquan-Qiongheba Paleozoic arc belt,East Junggar,was a new discovered gold deposit recently.Ore-hosting strata contain one suite of intermediate-felsic volcanic lava intercalated with volcaniclastic rocks,with orebodies occurring as veins,banding,lentoid and controlled by faults.This paper studied the geological and geochemistry features in the Luyuan deposit.Several conclusions have been drawn as follows.?1?The zircon U–Pb chronology study shows that the weighted average age of rhyolite is 293.2±1.9Ma,which is considered to represent the magmatic event during Early Permian.Three samples from the gold-bearing quartz veins at Luyuan yielded an Rb–Sr isochron age of 291.6±5.3Ma,which is considered to represent the age of ore formation.?2?Geochemical data show that volcanic rocks of the Luyuan gold deposit consist mainly of calc-alkaline series with partial high-k calc-alkaline series.These samples are enriched in LILE but relatively depleted in HFSE,with strong negative Nb-Ta-Ti anomalies.These characteristics,along with the discrimination diagrams,indicate that volcanic rocks of the Luyuan gold deposit are certain differential production of primitive magma,and these volcanic rocks are from extensional setting of post-collisional period.Their island-arc characteristics carried by the volcanic rocks are inherited from pre-collisional arc component.?3?Petrographic observation indicates that fluid inclusions of the Luyuan gold deposit can be divided into three types,i.e.,liquid-rich aqueous inclusions?type-L?,vapor-rich aqueous inclusions?type-V?and monophase liquid aqueous inclusions?type-P?.Microthermometric measurements indicate that these inclusions yield total homogeneous temperatures of 115³49°C,salinities of 0.7⁸.8 wt.%NaCl eqv.,and densities of 0.66⁰.98 g/cm³.The ore-forming fluid of the Luyuan gold deposit is characteristic of low temperature,low salinity,and low density.Laser Raman analysis shows that gas compositions and liquid compositions of the ore-forming fluids are mainly H2O.?4?The hydrogen and oxygen isotopic compositions of the ore-forming fluids show that?D_H2O=-108.8‰^-129.0‰,?¹⁸O_H2O=-7.2‰⁴.6‰,which indicates that the ore-forming fluids were formed as a result of multiple fluids,and mainly were derived from meteoric water.?5?The sulfides have a narrow?³⁴S range of+0.2‰to+2.8‰,with an average of+1.35‰,suggesting that the sulfur is characteristic of magmatic sulfur.?6?The ²⁰⁶Pb/²⁰⁴Pb,²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios of sulfide from main metallogenic stage are 16.457¹8.084,15.267¹5.635 and 36.472³8.379,respectively.The?values vary from 9.11 to 9.58,while the?values vary from33.97 to 38.61.Isotopic compositions and feature parameters suggest that the anomalous lead of the Luyuan deposit should have a mixing origin,with part from the upper crustal material and the other from the mantle material.?7?Based on the geological and fluid inclusion features,we conclude that fluid-boiling during the mineralization stage may be the major cause of ore material precipitation,and the Luyuan deposit is a typical low sulfidation epithermal gold deposit.