Research On Metallogenesis Of Gold Deposits In The Kunlun River Area,East Kunlun Mountains,Qinghai Province

The Kunlun River area is located in the western section of the EKOB in Qinghai Province,and has a large gold mineralization potential.However,due to the poor natural conditions in this area,mineral exploration work is still in the initial stage,and the degree of deposit research is generally low,far inferior to mature ore concentration areas such as Wulonggou and Guli.In this study,we have conducted a systematic study of magmatic rocks and mineralisation in the gold deposits such as Heihaibei,Lalingzaohuo,Jiazutashixi,Jiazutashidong,Heicigou,and Xiaohongshanbei.The main insights gained are as follows:1.The Wanbaogou oceanic basalt plateau was formed in the Neoproterozoic（768-762Ma）and is closely related to mantle plume activity that led to the breakup of Rodinia supercontinent.2.The Proto-Tethys Ocean was still in the subduction stage during the Late Ordovician,and in the Middle Silurian,the EKOB entered the post-collision extension stage of the Proto-Tethys evolution,indicating that the ocean closed no later than the Middle Silurian;The final closing of the Paleo-Tethys Ocean and plate collision began in the Middle Triassic,and the EKOB entered the post-collision extension stage during the Late Triassic.3.Discussed the geological characteristics,mineralization age,the source of ore-forming fluids and materials of the gold deposits in the Kunlun River area,and their relationship with tectonic magmatic activities in the EKOB.Determined the different genetic types of the deposits.（1）Based on a comprehensive analysis of trace element correlations and lead isotope compositions of pyrite from Lalingzaohuo,Jiazutashixi,Jiazutashidong deposits,it is further clarified that there is an upper mantle source of gold in the EKOB;（2）It is proposed that the Heihaibei gold deposit is an intrusion-related gold deposit,rather than an orogenic gold deposit previously believed.Gold ore bodies are mainly hosted in the Late Ordovician monzogranite,and the soil anomaly characteristics show that element anomalies such as Au,Ag,W,Sn,etc.are mainly concentrated around the monzogranite.The ore-forming fluids and materials mainly originate from magmatic hydrothermal source,and are closely related to the Late Ordovician monzogranite.Based on the zircon U-Pb ages of the monzogranite,it is preliminarily estimated that the formation age of the deposit is 454±3 Ma.（3）The gold deposits of Lalingzaohuo,Jiazutashixi,Jiazutashidong,and Xiaohongshanbei are orogenic gold deposits controlled by structures.Among them,the nearly E-W trending ore-bearing fractured zones delineated by gold deposits such as Jiazutashixi,Jiazutashidong are mostly surface eluvial or oxidation zones,and non primary ore-bearing fractured zones;Moreover,the excavation depth of the exploratory trench is not enough to well expose the occurrence of the ore body.Based on field investigation and comprehensive analysis of existing geological data,it is proposed that the ore bodies of gold deposits such as Jiazutashixi,Jiazutashidong are mainly controlled by near N-S trending ore-bearing fractured zones rather than near E-W trending ones;The ore bodies of gold deposits such as Lalingzaohuo,Xiaohongshanbei are mainly controlled by NWW trending ore-bearing fractured zones or ductile shear zones.The ore-forming fluids of the above gold deposits are characterized by medium temperature,low salinity,low density,and rich in CO₂.The ore-forming fluids mainly originate from mantle derived primary water/primary magma water.The sulfur isotope compositions show the characteristics of mantle derived sulfur/magma sulfur,and the lead isotope compositions show the characteristics of mixed crust and mantle lead isotopes in orogenic belts.（4）It is proposed that the Heicigou gold deposit is a porphyry type gold deposit.Gold ore bodies mostly occur on the top of strongly silicified granite porphyry or in the contact zone with the front edge of the surrounding strata.The mineralization type is mainly veined disseminated,with a large area of limonite developed,but the gold grade is relatively low.It has typical areal type alteration features,surrounded by granite porphyry,and is successively divided into sericitization zone,argillic zone and propylitic zone from inside to outside.The ore bodies are mainly located within the sericitization zone.Porphyry bodies are small in scale,with high silicon and potassium geochemical characteristics,and formed in a volcanic arc environment formed by ocean subduction;The ore-forming fluids belong to a CH₄-CO₂-H₂O-Na Cl system,exhibiting characteristics of medium-high temperature,low salinity,and low density,as well as characteristics of mantle derived fluids;According to the zircon U-Pb ages of granite porphyry,it is preliminarily estimated that the formation age of the deposit is 249±2 Ma.4.The gold metallogenic series in the Kunlun River area of the East Kunlun Mountains have been established and divided into three different types of gold deposits:intrusion-related gold deposits,porphyry type gold deposits,and orogenic type gold deposits.The gold metallogenic model in the Kunlun River area of the East Kunlun Mountains has been established;The regional metallogenic regularity of intrusion-related gold deposits,porphyry type gold deposits,and orogenic type gold deposits is summarized.