Genesis Of The Duobuza Copper Deposit In The Western Bangong Co-nujiang Metallogenic Belt, Tibet

Based on the full collection, analysis and summary of the previous data and onthe basis of the research, based on the large amount of field work, to the theory ofplate tectonics and collision orogenic belt theory as a foundation, system usingmodern metallogeny, geochemical theory and high precision analysis method,through to the Duobuza porphyry copper deposit role of research, has made thefollowing achievements and understanding:Through the Duobuza mining ore and mineral crystallization sequence andtypical mineral paragenesis relationship between the analysis and study, think ofDuobuza porphyry copper deposit ore forming process can be divided into3periods,respectively, magmatic mineralization period, hydrothermal mineralization stage andsupergene stage. Among them, hydrothermal period was divided into two stages:early stage between pyrite and chalcopyrite and late calcite gypsum phase, in whichthe hydrothermal period is the main metallogenic epoch.Mining granodiorite porphyry rock geochemical characteristics of majorelements: SiO₂content distribution in62.14%⁶8.49%, average65.44%, aluminumrich Al₂O₃（14.31%¹5.47%）, MgO （1.19%².50%）, TFe （1.81%¹1.74%）, CaO（1.5%⁶.13%） low TiO2（0.274%⁰.575%）, rich K₂O (1.15%⁴.82%, depletedNa₂O （0.21%⁴.46%）; rare earth elements content was relatively low, the relativeenrichment of light rare earth elements （LREE/HREE=3.76⁴.37, average4）, withdelta Eu weak loss or weak enrichment （δEu=0.58⁰.93, an average of0.81）, REEfractionation degree is low characteristic.Granodiorite porphyry and metamorphicsandstone relative enrichment of large ion lithophile elements Rb, K, Th, Ba, La, Ce,Sr, strongly depleted in high strength element Nb, Ta, P, Ti. Mining area and mineralization related to the granodiorite porphyry was formed in the late collisionorogenic phase.Duobuza mining lead isotope radioactive lead isotopic characteristics, the leadelements mainly comes from the mantle; sulfur isotopes in the frequency histogramshows apparent tower distribution characteristics, may be mainly derived from deepmagma, time for shell source; by calculating the mapping that mining area total sulfurisotope of-0.8per thousand, a meteorite sulfur isotopic characteristics, show that theore-bearing fluid from the mantle; noble gas isotope indicate fluid with thecrust-mantle mixing source characteristics.By collecting previous information identifying the Duobuza porphyry copperdeposit metallogenic age into the rock, the rock mass for the complex rock mass, themain magma ore-bearing porphyries and granodiorite porphyry zircon SHRIMP agewere117.1+1Ma and127.8+2.6Ma, formed in Yanshan in late. Duobuza porphyrycopper metallogenic age was120.4Ma+1.7Ma. Duobuza porphyry copper depositshow that with Yanshan in late and early Himalayan magmatism related printing-Asian continental collision late effects and the formation of the deposit.Multiphase inclusions are well developed in the mining area with solid-phasedaughter minerals. Duobuza mining area of fluid inclusions is a remarkablecharacteristic of solid mineral multiphase inclusions （total package bodydevelopment of more than7%of the total）, and there can be a variety of types ofmineral. Ore forming fluid with high temperature （homogenization temperature291to385.2℃） high salinity （36.02⁴2.10wt%） high density feature.Mineralization process: In Duobuza mining area, Yanshan acidic rock along thefracture and regional interlayer weak belt up emplacement. Early stage, ore-bearingmagmatic hydrothermal migrates upward extraction part of crustal minerals. At thistime the inner and outer contact zone in rock formation of the bell type ofhydrothermal alteration minerals and skarn. Subsequently, the temperature decreases,Subsequently, the surface precipitation begins along fracture gradually downwardpenetration, multiple silicide formation. Ore formation, in the late tectonic movementformed under the influence of Duobuza deposit, precursor and an oxidizing primarysulfide ore surface oxidation.