Geology And Genesis Of Baxi Copper Deposit In The Eastern Junggar, China

The Baxi copper deposit is the located in the eastern of the Yemaquan-Qiongheba island-arc belt,which is the newly discovered deposit in the Qiongheba ore centralization area in the Eastern Junggar.There are two stages intermediate-acid intrusive rocks during the Silurian and the Early Carboniferous within the Baxi copper district,are represented by granodiorite?430.1±4.4Ma?,monzogranite?419.5±4.1Ma?and quartzdiorite?346.6±3.6Ma?,respectively.The mineralization of the Baxi copper deposit is related to quartzdiorite,quartz monzodiorite and diorite porphyrite that emplacement at the early Carboniferous?fig.3?,which formed during the Early Carboniferous?Visean?.The whole-rock chemical data suggest that the quartzdiorite is intermediate-acid I-island arc magmatic rocks with Na-rich,Quasi aluminum to weaker peraluminous and calc-alkaline.The REE of the rocks are relative enrichment of LREE,and enriched in large-ion lithophile elements?LILE?Rb,Ba,U,Sr and depleted in high field strength elements?HFSE?Th,Nb,Ta,Ti,P.The ore body has typically features of alteration-mineralization zoning in porphyry copper deposit,which comprises,centrally from the bottom upward,several of potassic,phyllic,argillic and prophylitic.That are corresponding to diorite porphyrite,quartzdiorite,quartz monzodiorite and sedimentary wall rocks respectively.The main ore minerals are chalcopyrite and pyrite.The study about fluid inclosures in the potassic and sericitic zones show that the temperature of the ore-forming fluids exceed 500?.The mineralization is related to magmatic hydrothermal fluids,which are derived from intrusive emplacement during the Early Carboniferous.The metallogenic fluids are represented by high temperature and low salinity in the early stage of mineralization,transform into high temperature and high salinity in the main stage,and low temperature and low salinity in late stage.The ?Hf?t?values of the granodiorite?430.1±4.4Ma?,monzogranite?419.5±4.1Ma?and quartzdiorite?346.6±3.6Ma?are 14.16±0.29,14.17±0.27 and 14.70±0.42,respectively.The three TDM₂ are 440Ma⁶09Ma,445Ma⁶03Ma,355Ma⁴74Ma.The data show that the two stages intermediate-acid intrusive rocks all have high?Hf?t?values and young TDM₂.The samples fall near the boundaries of depleted mantle?DM?in ²⁰⁶Pb/²³⁸U age-?Hf?t?diagram?fig 6-4?.The data imply that there are at least two events of the growth and of continental crust in this district.Combine their tectonic setting and geochemical characteristics,they're the corresponding event of the closure of the Paleo-Asian Ocean and the Karamaili oceanic basin,respectively.