The East Kunlun orogenic belt is located in the northeast of Qinghai-Tibet Plateau,which is one of the main orogenic belts in Qinghai-Tibet Plateau in China.It is an ideal area to study the magmatic activities and geodynamic processes related to the closure of the Proto-Tethys Ocean.The Nagenglongwa Gold Deposit is located in the southeast of the East Kunlun orogenic belt and is a typical mesothermal vein type gold deposit.Based on the study of petrology,zircon U-Pb chronology,and whole-rock geochemistry of the amphibole-rich mafic rocks in the Nageng-longwa Gold District,the genetic types and source region have been discussed,and the geodynamic setting has been restored.On this basis,the relationship with the gold mineralization is discussed.The zircon U-Pb age indicates that the emplacements of the amphibole-rich mafic rocks are located at 424.5 Ma±2.4 Ma,which are the products of magmatic activities in the late Silurian epoch.The petrogeochemistry results indicate that the amphibole-rich mafic rocks have the characteristics of low SiO₂,high Al₂O₃ and Mg#,revealing mantle origin attribute.The samples with the high K₂O contents belong to the series of high potassium calcium alkaline-potassium basalt.The samples display strong enrichment in light rare earth element and depletion in heavy rare earth element(w(La)N/w(Yb)N value is 33.24-52.14),enrichment of large-ion lithosphile elements (Rb,Ba,K,Pb),and relative depletion of high field-strength elements (Nb,Ta,Ti,Zr,Hf),demonstrating that the mantle source region has been extensively metasomatized by fluid.To sum up,it is considered that the amphibole-rich mafic rocks are the products of partial melting of the lithospheric mantle metasomatized by subduction fluid.Based on the geological evidence of other magmatic and sedimentary records in the region,it is considered that the amphibole-rich mafic rocks are the products of the strong extensional tectonic setting caused by the subduction plate fragments after the closure of the Proto-Tethian Ocean.The strong post-collision extensional setting provides the necessary thermodynamic and kinetic conditions for the upward migration of gold-bearing mantle fluids.