Geochemical Characteristics And Metallogenic Significance Of Tuwu Porphyry Copper Deposit In East Tianshan

The Tuwu copper deposit,the most typical porphyry copper deposits in East Tianshan area,is located in the middle of the Dananhu late Paleozoic island arc of Junggar plate.The second rock group of Carboniferous Qiershan Group is the main ore strata.The ore bodies are controlled by the Kangguertage faults in south and the Dacaotan fracture in north.The mother rock is plagioclase and the wall rock is the diorite.The diorite is alternated by plagioclase.The main volcanic is Qiershan Group of Carboniferous.The deposit locate in gravity anomalies and high Cu background zone.The rock alteration is well-developed;main ore body is in quartz-sericite zone.According to the fieldwork,and the laboratory experiments analyzed and the basis of data,draw the conclusions below:The plagioclase belong to the ? type granite,and has the Adakite nature.Sample show it belongs to sodium sub-alkaline K calc-alkaline series.The spider diagram is rightist and rich in big LILE loss in HFSE,the Nb-Ta negative anomalies.The REE patterns is rightist.LREE fractionation and ?Eu with ?Ce is not obvious.Diorite is sodium sub-alkaline series.Big LIEE is enrichment relative to HFSE and Ta?Nb?Ti negative anomalies.LREE is enrichment and LREE fractionation is not obvious,?Eu and ?Ce is weak.The zircon of the plagioclase sample TW-005-502-3 is long between 81nm?255nm,width 38nm?85nm and the aspect ratio is 1.8:1?3:1.The zircon have good self-shaped,clean and transparent,and they have clear shock belts,show that they have magmatic origin character.The Th content ranage 29×10-6?134×10-6,The U content ranage 65×10-6-208×10-6.The ratio of Th/U of the TW-005-502-3 is 0.29?0.79,all greater than 0.1,show that their has magmatic origin character.The zircon 206Pb/238U age is 325.3±4.8?351.0±6.3Ma,and the weighted mean 206Pb/238U age is334.6±2.8Ma(N=13,MSWD=0.47),show that the plagioclase formed in the Carboniferous.The molybdenite sample has 187Re1913±17×10-6 and 187Os9888±78×10-6,the model ages is 309.5±4.5Ma,combine with the plagioclase and diorite zircon U-Pb age show that the tuwu porphyry copper deposit is formed in the Carboniferous.The S isotope test results ?34Sv-CDT of pyrite and chalcopyrite is-3‰?1.7‰,and an average is 0.15‰,combine with the high Re of molybdenite show that the mineralization material mainly from mantle.The trace element?REE and the tectonic setting discrimination diagrams with the geochronology evidence show that the Tuwu porphyry copper deposit formed in Carboniferous active continental marin of Junggar plate.And the Tuwu porphyry copper deposit is the product of the North Tianshan Ocean subduct toward north.