The Comparative Study On Deposit Geochemical Characteristics Of Gaerqiong,Duobuza Copper-gold Deposit,Tibet

Gaerqiong and Duobuza copper-gold deposits are located in the west of BangongLake-Nujiang Metallogenic Belt. The former lies in Cuoqing-Shenzha Magmatic Arcin the south margin of this metallogenic belt, while the latter lies in Zhapu-DuobuzaMagmatic Arc in the north margin of the belt. As the first copper-gold deposit in thewest of the metallogenic belt which has done researches in details, the reserves ofgold in Gaerqiong copper-gold deposit has reached a large scale. The deposits aremainly composed by two main ore bodies I,II and34small ore bodies. The main orebodies are concealed-half concealed ore bodies in general, which are controlled by thenortheast-southwest faults F1,F2and their secondary faults tectonic systems in themining area. Recent years of explorations and studies have shown that Duobuzacopper-gold deposit is the mega-rich porphyry Gold-Copper deposit which has thesuper prospecting. The main ore bodies are composed by ore body I,II and areconcealed-half concealed ore bodies.This article is on the basis of former works, through the comparative studies ofthe two deposits in their geochemical characteristics, including rock geochemistrycharacteristics, fluid inclusion characteristics and isotopic geochemistrycharacteristics, in order to find the differences and similarities between the twomining areas on tectonic environment, ore-forming fluids and ore-forming materialsources, to reveal the geodynamic background of the two deposits.Gaerqiong ore-bearing rock is mainly calc-alkaline granite series which isbetween metaluminous and peraluminous series. Here the granite porphyry belongs tothe metaluminous-weakly peraluminous series. Duobuza mineralized porphyry isperaluminous-calc-alkaline granite series. They both share the characteristics of theisland arc magma. In Gaerqiong deposit,there are mainly medium-high temperature,low-salinity fluids which are mixed with the magma and meteoric water, partly hightemperature and salinity fluids; fluids are most high salinity, high temperature fluids,partly medium-low temperature, low salinity fluid in Duobuza deposit. S isotopestudies have shown that the source of sulfur in Gaerqiong deposit has thecharacteristics of mantle-derived sulfur; In Duobuza deposit, sulfur displayscharacteristics of mantle source and mixed source derived. Pb isotopic studies havenoticed that, in Gaerqiong, metallogenic materials are mainly derived from the lowercrust. In the same time the source of lead appears characteristics of orogenic beltwhich should be the mixture of the lower crust and upper mantle sources; in Duobuza deposit, metallogenic materials may come from the upper mantle source and also hascharacteristics of mixed lead in orogenic belt. The source region may bemetasomatized by melt of subducted sediment.Integrated studies have shown that Gaerqiong copper-gold deposit is formed inthe late Cretaceous Tectonic Setting of the collision, belongs to skarn-porphyrydeposit; while Duobuza copper-gold deposit is formed in the early Cretaceoussubduction tectonics background, belongs to the porphyry copper-gold deposit, bothof them belong to the porphyry Mineralization Series.