Metallogenic Source And Ore Genesis Of Typical Iron Deposits In The Central Segment Of Awulale Metallogenic Belt, Xinjiang

Awulale metallogenic belt is located in the contact part of the Kazakhstan-Junggar plate and the Karakum-Tarim plate, where has many large and medium-sized iron ore deposits. The work has been completed mainly concentrated in the east.So this paper choose the Songhu, Qiongkuer and Nixintage iron deposits as studyobjects that we can do better understanding of the metallogenic regularity. On thebasis of describing the geological characteristics of ore deposits and dividing themetallogenic stages, we got some conclusions about metallogenic tectonicbackground, ore-forming material sources, mineralogenetic epoch and deposit typethrough electron probe test, the single mineral trace elements analysis, geochemistry,U-Pb chronology, Hf isotope test and stable isotope study.1. Early magnetites were associated with high K-acidic magmatic hydrothermalsystem in Songhu iron deposit, late magnetites were formed in the late magmaticactivity or period of inactivity which characterized by hydrothermal origin.Magnetites from the Qiongkuer iron deposit also formed in two stages(early and late),its structure characteristics and the element content are different from the Songhu irondeposit, may be because of the strong hydrothermal superimposed reformation.2. Magnetites from the Nixintage iron deposit formed in three stages(early,middle, late), Electron microprobe analyses show that it formed related to themagmatic activity. The magnetites are rich in Zn, Sc, Co, Cu, has the characteristics ofmagmatic and hydrothermal metasomatic origin of magnetite. Content of Ni and theratio of Ti/V is generally low, so we can rule out the possibility of magmatic origin.Above all, magnetites formed in the hydrothermal process.3. Magmatic rock in the Nixintage iron deposit is active continental marginmagmatic arc granite, plagioclase granite is the same as the source of monzoniticgranite. The former one has the feature of low potassium weakly peraluminouscalcium alkaline, two ages of ziron U-Pb LA-CIP-MS are324.5±2.0Ma and 322.9±2.6Ma; the latter one belongs to metaluminous shoshonite series, two ages ofziron U-Pb LA-CIP-MS are334.4±2.3Ma and333.6±2.2Ma. Zircon Hf isotopiccompositions show that magma comes from relatively young mantle material with thehybridization of ancient crust.4. δ34S of pyrites from three deposits ranges from-3‰to3.7‰which closes tothe mantle sulfur isotopic composition, infers sulfur source is simple, ore-formingmaterials come from deep magma system. Carbon and oxygen isotopes show thatore-forming fluid has the characteristics of magmatic water mixed with sea water, butmagmatic water is the main source.5. With the considering of regional tectonic background and previous researchresults, we think that the Songhu, Qiongkuer, Nixintage iron deposits formed in theisland-arc environment and constitute a tectono-magmatic metallogenic system. TheSonghu and Qiongkuer are marine volcanic-hydrothermal deposits and formed inone mineralization. The Nixintage is a marine subvolcanic-hydrothermal depositwhich formed later, cryptoexplosion maked its mineralization characteristicssignificantly different from the first two iron deposit.