Geological And Geochemical Characteristics And Ore Genesis Of Kuokuqueke Fe-Cu Deposit In West Tianshan,Xinjiang

The Late Paleozoic Boluokenu island arc belt,located at the north margin of West Tianshan,Xinjiang,hosts a series of skarn-porphyry iron copper polymetallic deposits and intermediate-acid intrusions.This paper use the methods of field geological mapping,profile survey and geological logging to study the geological characteristics of Kuokuqueke skarn-type Fe-Cu deposit which lies in the middle of the arc belt,and combine with microscopic identification and advanced testing technology to study elemental geochemistry,mineral chemistry,isotope chronology,ore deposite geochemistry and fluid inclusion,and some important progress and understanding were achieved,mainly includes the following points:?1?The main strata of mineral area is Silurian Nilka River Fomation,the ore types mainly include skarn magnetite,hematite and lead-zinc ore,the main wall rock alteration include skarnization,sericitization,chloritization,silicification and carbonatation,the metallogenic periods can be divided into skarn period,oxide stage and quartz-sulfide stage.?2?The ore-forming rocks are enriched in SiO₂ and K₂O with A/CNK<1.1,belonging to I-type granite of high-K calc-alkaline series.They are enriched in LREE and LILE with clear negative Eu anomalies,and are depleted in HREE and HFSE.The Nb/Ta ratio?9.8¹3.3?,the MgO contents in biotite?9.45%¹0.99%?and the M values of amphibole?0.73⁰.85?are all between crust-derived type and mantle type.LA-ICP-MS U-Pb isotopic dating on zircons from Kuokuqueke granite and diorite yielded similar ages of 362.8±2.8 Ma and 363.4±3.7 Ma.The Rb-Yb+Nb and Rb-Yb+Ta diagrams indicate that most of the rocks belong to volcanic arc granitoids.The Sr/Y-Y and?La/Yb?N-YbN diagrams show all of them are island-arc rocks,all of these data suggest that the Kuokuqueke intrusion formed under the tectonic setting of subduction during late Devonian.Zircon saturation temperature?705?⁷60??and biotite formation temperature?710?⁷50??suggest that the magma originated from partial melting of the lower crust.Th/Ce-Sr/Th and Th/Yb-Sr/Yb diagrams show that the diagenetic fluid is from dehydration of sediments.Harker diagram and the strong depletion of Ba,Sr,P,Ti and Eu indicate that the rocks have undergone crystallization differentiation.?3?The studies of fluid inclusions showes that the ore-forming fluid of Kuokuqueke deposit belongs to medium-high temperature and medium-high salinity,immiscibility of the ore-forming fluid during the whole metallogenic stage is the main reason for the metallic mineral precipitation.?4?The stable isotope studies show that S and C is mainly derived from deep granitic magma,Pb is mainly derived from magmatism which caused by plate subduction.?5?The studys suggested that the Kuokuqueke granite mainly formed from partial melting of the lower crust caused by dehydration of the subduction zone when the North Tianshan ocean subducted to the Yili plate during the late Devonian,the pluton intruded into the carbonate rocks of the Nilka River Fomation,hydrothermal fluids rise in the fissure and forming Kuokuqueke skarn-type Fe-Cu deposit.