Research On The Metallogenic Geological Background And Genesis Of Huanglonggou Ore Block In Shenshuitan Gold Deposit In The Wulonggou Ore Concentration Area In The Eastern Kunlun Orogenic Belt, Qinghai Province

The Wulonggou area,whose geological position situate in the Eastern Kunlun Orogen of northern Tibetan plateau,is bounded on the west by Dachagou,on the the east by Wuminggou,on the north by the exit of Wulonggou and on the south by Zhongzhigou as well as Baidungou,and divided into 31 gold mining areas and 52 deposits?ore spots?,which is a noble ore concentration area in the Eastern Kunlun area.There are three important NW-NWW direction ductile shear zones,which are Yanjinhou?Shihuigou?ductile shear zone,Yingshigou-Hongqigou ductile shear zone and Sandaoliang-Kushuiquan ductile shear zone.Shenshuitan mining area belongs to Yingshigou-Shenshuitan ductile shear zone,and its mineralization has a strong relationship with the No.?Fault.The Shenshuitan mining area consists of three ore sections,Shuidonggou,Huanglonggou and Heishigou,totally containing 38 delineated gold ore bodies.In this research,we put the Huanglonggou Ore Block in a high position.The mineral type is mainly altered rock.The ore minerals contain pyrite,galena,sphalerite,pyrrhotite,chalcopyrite and arsenopyrite,and gangue minerals contain quartz,calcite,feldspar,amphibole,sericite and chlorite.The textures of these ores are subhedral granular-allotriomorphic,metasomatic,fragmental,a small amount of inclusion,and the structures are the infection-like structure,reticulate vein structure,veinlet structure and breccia structure,etc.There are three kinds of gold occurrence form,including encapsulating gold,intergranular gold and fissure gold.And encapsulating gold is the main form,which gold can be found in Arsenopyrite,pyrite,white iron ore,stibnite and stibnite.The alterations of wall-rock are silicification,sericitization,pyritization and Kaolinite,as well as a little of carbonation,chloritization.The mineralization can be divided into the hydrothermal and metallogenic periods,and furthermore,the hydrothermal period can be divided into quartz-sulfide and calcite-sulfide stages.The researches of geochemistry in this mining area further reveal the genesis of the deposit.The?D and?¹⁸O of quartz and sericite from the quartz-sulfide stage are-2.29⁺5.11‰and-113.9^-68.4‰,indicated the water of hydrothermal fluid of quartz-sulfide stage mainly derived from deeply metamorphic water.The ²⁰⁶Pb/²⁰⁴Pb,²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb of sulfide from the quartz-sulfide stage are 18.071¹9.341,15.530¹5.673 and 37.908³8.702,indicated the lead mainly came from the metamorphic rocks but still had possibility of partly mixing the surfer from granite.However,the²⁰⁶Pb/²⁰⁴Pb,²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb of sulfide from calcite-sulfide stage are18.418¹9.454,15.627¹5.666 and 38.449³8.576,indicated the lead was from metamorphic wall rocks but not related with granite.And the two stage lead isotope characters both reveal the settings of mineralization correlate to the orogen background.As for the analysis of surfer isotope,we used two kinds of text methods,the bulk and SIMS in situ surfer isotope analysis,and they don't show much difference within the range of error.The data showed the sulfur isotope of?³⁴S_H2S from quartz-sulfide stage are-8.80⁺10.70‰,and the calcite-sulfide stage are+1.10⁺6.07‰.Both of them show the source of metallogenic material is average crust,which means metamorphic strata and granite.The?³⁴S of quartz-sulfide stage sulfides are-7.30⁺11.04‰,which is similar with sedimentary-controlled orogenic gold deposits.The?³⁴S of sulfides from calcite-sulfide stage are+2.32⁺7.92‰,which are the typical characters of?³⁴S of sulfide in settings of orogen.This study contained the method of LA-ICP-MS U-Pb dating to constrain the precise timing of the Huanglonggou granodiorite cut by gold-bearing fractured altered rocks.The results indicated the Honglonggou granodiorite formed in Late Triassic Carnian?221 Ma?,and combined this age with the formal studies,we conclude the Shenshuitan gold deposit was formed not early before 215 Ma,but not late after the ending of Late Triassic.According to the research of the geochemistry analysis of Huanglonggou granodiorite and zircon Lu-Hf,they showed this rock formed at the geological setting of soft collision and northward subducting of Paleo-Tethys oceanic slab,so the magma is derived from the partial melt of the oceanic crust.So it further constrained the metallogenic geological background of Huanglonggou ore block are subduction environment.