Genesis Of Gold Mineralization In The Sandaowanzi Gold Ore Deposit,Heilongjiang Province-Geochemical Constraints Conditions Of Ores And Rocks

The Sandaowanzi gold telluride deposit is located in the northeast of the Great Xingan mountains,which is a unique gold telluride deposit in the world.Almost all the gold(>95%)of deposit is contained in gold tellurides.The Sandaowanzi gold telluride deposit has generality and speciality.With the research of geochemistry of the deposit,we could further understand the genesis of telluride gold deposit.(1)The research of metallogenic geochemical characteristics,alteration phenomenon and the morphological characteristics of the quartz vein contribute to further understanding of the metallogenic period and sequence.According to the correlation between tectonics and mineralization,the tectonics events could be divided into three periods:pretectonic metallogenic stage,syntectonic metallogenic stage and posttectonic metallogenic stage.(2)The results of rare earth elements(REE)from the ores and wall rocks show positive abnormity of Eu element,indicating that metallogenic environment obeys relative oxidation condition.According to the diagram of(La/Y)_N-?Eu,the metallogenetic materials are derived from crust-mantle source.(3)Based on the data of trace elements,the volcanic rocks in the area of Sandaowanzi are in the enrichment of Ba,U(LILE),and in the deficit of high field strength elements(HFSE)like Ti.The trace elements are lack of correlation between each other.According to the diagram of Th/Yb-Ta/Yb,the volcanic rocks are formed in the environment of active continental margin.From the trace elements of pyrites and previous research conclusions,the mineralization temperature of the Sandaowanzi gold deposit ranges from 220°C to 320°C,and the mineralization depth ranges from2.37 to 2.96 km.Because of these factors,the Sandaowanzi gold deposit belongs to epithermal deposit.(4)Magmatic activity,tectonic development,regional strata and the morphological characteristics of quartz vein play the role of controlling and division.Because Izanagi plate subducted into Eurosian plate in Mesozoic age,volcanic eruption belt and NE strike-slip faults and NW extension fracture developed in this region.In addition,the subduction between the plates contribute to the formation of magmatic hydrothermal in the crust-mantle zone and ascent and emplacement of metallogenic material.The gold precipitated and enriched along with NW extension fracture because the condition of shallow crust changed,which resulted in this epithermal deposit.