Analysis Of Ore-forming Geologic Conditions Of Porphyry Copper Deposit In Halasu Area In Qinghe County, Xinjiang Autonomous Region

This paper relies on the project "The positioning exploration of Halasu porphyry copper deposit in Qinghe county, Xinjiang autonomous region", which is studied by China university of Geosciences, Beijing and No 4 geology team of Xinjiang geology and mining bureau. .Halasu porphyry copper deposit is located at the south margin of the east section of Altai mountain, the southwest margin of Siberia plate , northeast margin of Zungar plate, where is the oblique collision and jointing position of the two plates. The area is located in the intersection position of Eerqisi structural belt and Keketuohai-Ertai faults belt in NNW .Early-middle Devonian bimodal igneous rock formation deposited in this area. The tectonic setting is bimodal rift. There are good ore-forming geologic conditions and the conditions of porphyry copper forming. Based on field geology study and rich data, the author studied the structure shape,the distribution of intrusions, ore deposit geology, genesis of ore deposit in Halasu copper mine. The main results and awareness are as following:(1)The mine is located in the Eerqisi regional fault belt which is in the contact of Siberia plate and Hasake-Zungar plate. Faults in this area developed well with main strike in NW. .The area is in the east extension range of Eerqisi ductile shear zone with obvious ductile shear deformation. Not only did faults in NW control the distribution of ore bodies, but also controlled the distribution and shape of porphyry mass related to ore-forming and the medium-basic volcanic group. Ductile shear structural movement in the end of early conboniferous strongly metamorphosed strata in each epoch formed before and granitoid roks in subduction period. In the process of forming and evolvement, the movement impelled the ore-forming elements to gradually travel ,and extracted and enriched them into ore.(2)The main intrusion rocks in the mine are in middle-late Hercynian with two intrusion stages mainly. Monzonitic granite, granodiorite porphyry dyke and quarts diorite are in the early stage while a lot of othophyre dykes in the late stage. Granodiorite ,quarts diorite dykes are main host rock of mineralization. Othophyre dykes commonly cuts ore body and other rock bodies and were not deformed at all, which indicates that it is the product in the late stage of ore-forming.(3)Porphyry copper deposits in Halasu copper mine mainly distributed on the northeast side of Kalaxiangeer faults belt which is in NW orientation. The host strata are middle Devonian neutral-basic igneous rock and pyroclastic rock. Copper mineralization isconcentrated in quarts diorite and granodiorite porphyry which is strongly potash feldspar altered.(4)S isotopes and Pb isotopes indicate the main ore-forming materials are from volcanic rock and granite- dioritic porphyry dyke. H and O isotopes indicate the ore-forming fluids are the mixture of magmatic water and mefeoric water.(5)Middle Devonian- early Carboniferous granodiorite porphyry, quarts diorite, dioritie porphyrite, monzonitic granite were the main provider of force and material of the first period of copper mineralization.(6)In Triassic, the belt was influenced by Keketuohai-Ertai faults belt with obvious tectonic-magma-fluid movements, mainly the intrusion of orthophyre dyke accompanied by typical potash feldspar alteration. The former porphyry copper mineralization was overprinted by obvious tectonic-fluid movement, which formed the second period of mineralization.