Genesis Of Hulalin Gold Deposit In Upper Heilongjiang Basin

The Hulalin deposit in the Upper Heilongjiang Basin is located on the northern edge of the Erguna microblock in the northern part of the Greater Xing'an Mountains in the eastern section of the Xingmeng orogenic belt,sand wiched between the Mongolian Okhotsk suture zone and the Deerbugan fault.This article is based on rock and ore deposit petrography,chalcography,diagenetic chronology,rock geochemistry,pyrite LA-ICP-MS in situ,Hf,and S,Pb isotope geochemistry study.To determine the diagenetic age of the rock and the rock types,and then discusses diagenesis,source of ore-forming materials,combination characteristic,speculate that the formation background and evolution mechanism,deduce the relationship between diagenesis and mineralization.(1)The diagenetic age of granite in the Hulalin deposit is 249.8 ± 1.7Ma.The diagenetic age of granite porphyry and quartz porphyry is 141.7 ? 144.9Ma.There existence of two phases of Early Triassic(? 250Ma)and Early Cretaceous(? 143.5Ma)in the deposit.(2)The Early Triassic granites in the Hulalin deposit are a set of high-potassium calcium-alkaline type I granites.The rocks are rich in silicon and aluminum,which are the products of highly crystalline differentiation of magma.The rocks are rich in light rare earths,large ion lithophilic elements(LILEs),relatively depleted medium and heavy rare earths,and high field strengthelements(HFSEs).Based on the zircon Hf isotope,trace characteristics,and tectonic setting,it is believed that the rock formed in the Mongolian-Okhotsk crust subduction tectonic background of the Erguna block.(3)The Early Cretaceous granite porphyry and quartz porphyry of the Hulalin deposit are type I granites with a transition from high-potassium calcium-alkaline to potash basalt,which are the products of separation and crystallization during different evolution stages of homogeneous magma in the same period.The rocks are relatively rich in light rare earth and large ion lithophilic elements(LILEs),relatively depleted heavy rare earths and high field strength elements(HFSEs).Based on the zircon Hf isotope,trace characteristics,and tectonic background,it is believed that the rock was formed in the Erguna block and the Siberian continent in a post-collision environment,and the ancient crust melted under the tectonic background of extrusion to extension,and there was a small amount of new crust Physical participation(4)The results of LA-ICP-MS in situ test of pyrite of the Hulalin deposit show that Co,Ni,As,Se elements occur in pyrite in the form of homomorphism.However,Au,Ag,Cu,Pb,Zn,Bi,Te,Mo,V,Cr,Mn,Sb,Sn,Ga and other elements occur in pyrite or in the form of particles or independent minerals.The S and Pb test results of the pyrite-bearing orebodies in the Hulalin deposit show that the source of the ore-forming fluid is deep magma.The ore deposit was formed in the extension of the Erguna block and the Siberian continent.It is a porphyry-type gold deposit superimposed with superficial and low-temperature hydrothermal fluids.