Metallogenic Regularity Of Huangniping Gold Deposit In Southwestern Shaanxi Province

The Huangniping gold deposit in Shaanxi province is located in the southern margin of the Yangpingguan fault which straddles the boundary in the back-Longmenshan orogen of the nortern margin of the Yangtze plate in the south,was gold deposit of quartz vein type and tectonic altered rock type.Based on the project of Huangniping gold exploration in Ningqiang county,Shaanxi Province,this paper studies the geological characteristics and genesis of the deposit.Through analysis the relationship of the ore body and the strata,structure,magmatic rocks and the wall rock alteration,We sysmetically studied the geological characterisitcs,ore control factors,mineralogenetic epoch,ore-forming material source and the genesis of the deposit,and alsoeatablished the metallogenic model of Huangniping deposit.The results of this study area as follows:The gold bearing minerals include arsenopyrite and pyrite.The content of the element ninickel in the pyrite is low.The cobalt to nickel ratio is generally from 1 to 3.However,the monaziteis rich in Ce2O3 and La2O3 and poor in Gd2O3.So the author considers that the gold deposit was probably formed by the low-temperature hydrothermal metasomatism.The ore-controlling structure of the Huangniping gold deposit is not only the strata and the fault,but also the position which provide the enrichment space for the ore forming fluid.The ore forming space is controlled by the strike-slip fault formed in the mid-term of the thrusting deformation and also the overlap in the late-term of the thrusting deformation.The ore bodies are almost concealed and semi-concealed.The characterisitics of the ore bodies in four section of Huangniping gold deposit are similar,such as the morphology of the ore bodies,the ore types,the gold bearing minerals and the wall-rock alteration etc.It seems that they are closely related.The Huangniping belongs to that of ductile shear zone type.The ore-forming fluid comes from the basement volcanic rocks which suffered the ductile shear process.It seems that there should be blind ore-body in the deep.The mineralization mechanism of the Huangniping gold deposit is as follows:(1)With the overthrusting process of the North China plate towards the Yangtze plate from north to south in Yanshannian period,the gold ouucred in the volcanic rock evolved into gold bearing hydrothermal in the process of the ductile shear of the basement volcanic rocks in the deep.The gold bearing hydrothermal migrated upward along the fault and then enriched in the low metaporphic greenschist facies formation.(2)The main ore minerals,such as pyrite,arsenopyrite,chalcopyrite,tetrahedrite,brookite,sphalerite,hematite and limonite and so on are a min-temperature mineral assemblage.It can be concluded that the deposit belongs to mid-temperature hydrothermal alteration type.