Ore Genesis Of The Sandaowanzi Telluride-Gold Deposit In Heilongjiang Province

Sandaowanzi gold deposit,east of Heihe city,Heilongjiang province,located in the east edge of Xingan Plot,northwest of the Hegenshan-Heihe Fault.The deposit was first explored in the 1990 s.In this paper,we focus specifically on the geological setting,chronology of the mineralization and diagenesis,geochemistry,fluid inclusions and isotopic geochemical studies suggest that the Sandaowanzi deposit is low-sulfidation epithermal gold deposit,related to alkaline rock.Through the field found that the Sandaowanzi gold deposit are mainly hosted in northwest extensional faulting.The orebodies shape are main occur as quartz vein.The ore minerals are mainly pyrite,secondly chalcopyrite,sphalerite,galena,sylvanite,hessite,and petzite,etc;gangue minerals are mainly consisted of quartz,plagioclase,adularia,kaolinite,chlorite,epidote,sericite and calcite,etc.The wall-rock alteration is mainly silicification,sericitization,propylitization,kaolinization and carbonation etc and the alteration zoning is asymmetrical distribution in the quartz veins in banding.The alteration zoning from the orebody to wall rock is silicification zone,phyllic zone and propylitization zone,respectively.Alteration in order to propylitization-sericitizationkaolinization-silicification?white quartz?-silicification?dark quartz?-carbonation,late alteration superimposed on early,make alteration boundaries blurred.Silicification is closely related to mineralization.The fluid inclusions in Sandaowanzi gold deposit are mainly liquid-rich inclusion?W-type?,pure vapor inclusion?V-type?,and pure liquid inclusion?L-type?.The homogeneous temperature of the fluid inclusions are 160³49?,corresponding salinities of 1.22⁵.81 wt.% NaCleqv.These features indicate that the early ore-forming fluid belongs to a medium-temperature,low salinities,with the main gas components of H₂ O,and CO₂.Subsequently,the fluids evolved into low-to medium-temperature,with low salinities during main stages,belongs to a H₂O–NaCl-CO₂ system with minor CH₄,FIs trapped during the last mineralization stages have low salinities and temperatures,belongs to a H₂O–NaCl system.Zircon LA-ICP-MS U-Pb dating of ore-forming trachydacite porphyry and the sericatic age of ⁴⁰Ar/³⁹ Ar are 124.2±0.9 Ma?n=18,MSWD=0.5?and 122.4±3.9 Ma,dating indicates that metallogenic age between 124 and 122 Ma.Element geochemical characteristics reflect that the volcanic rock of Tamulangou formation charactered by enrichment of large ion lithophile element?such as Cs?K?Rb?Ba?LREE?,relatively depletion of high field strength elements?Nb?Ta?Zr?Hf?and notable depletion of Th,U and Nb,Ta,indicating the volcanic magma was derived from the lithospheric mantle by fluid metasomatism,But there are join of crust component in the process of magma evolution and emplacement.Comparative studies suggest the diagenesis and mineralization of the Sandaowanzi gold deposit occurred in early of the Early Cretaceous,formed in the extrusional environment under magmatic arc or the back-arc region of an immature continental margin and is associated with the subduction of Paleo-Pacific plate.