Carboniferous Granitic Magma Activity And Gold Mineralization In The Kalamaily Region, Northern Xinjiang

The Kalamaily region,located in the eastern Junggar Basin,Xinjiang,is tectonically in the southern margin of East Junggar arc basin which belongs to Central Asian orogenic belt.Ophiolite blocks expose intermittently along the northwest extended Qingshui-Sujiquan and Kalamaily faults,and occur as melanges,as being mixed by the extensively distributed late Paleozoic volcanic-sedimentary formations.In Carboniferous massive granitic magma activities developed within this northern area.Most of the gold deposits are distributed in the ophiolitic melange zone that underwent ductile shear deformation.Gold deposits are distributed band-shaped and bear the character of subsection concentration.In the current,the progresses of the research on the genesis and metallogenic prognosis for gold deposites in the Kalamaily region is slower,one of the reasons is due to the complexities of metallogenic environment and ore-controlling factors,the other is caused as a result of the research is not comprehensive,such as many granite-related gold deposits have been found at home and abroad,the genetic relationships between granite magma activity and gold mineralization in the Kalamaily region is not too much to discuss.Using petrology,petrogeocehmistry,fluid-inclusion geochemistry,zircon LA-ICP-MS U-Pb geochronology and stable isotope methods on the base of thorough geological investigation,this work intensively studied the features of Carboniferous granites and gold deposits in the Kalamaily region,their genetic relationships,and the dynamic mechanisms of diagenesis and mineralization.The aimes of this works are to find an effective methods of metallogenic prognosis.The main results are as follows:1.It is confirmed that granitic activities can be divided into two periods,namely the calc-alkaline period in the early Carboniferous?350³40 Ma?and the alkaline period in the late Carboniferous?320³10 Ma?.The formation of low potassium calc-alkaline granite in the early Carboniferous is related to the partial melting of Devonian oceanic crust.While the sources of high potassium calc-alkaline granite in the early Carboniferous and alkaline granite in the late Carboniferous are Devonian oceanic crust and some terrigenous matters.2.There exist two periods of gold mineralization which are intimately coupled with the early and late Carboniferous granitic magma activities.The earlier mineralization period is related to the low potassium calc-alkaline granitic magma activity,and the later one to the alkaline granitic magma activity.The earlier gold deposits'metallogenic environment is a compressional tectonic setting.It's ore-forming fluid was magmatic water,and the materials came from the Earth's mantle.The later gold deposits'metallogenic environment is the tectonic setting which changed from compression to extension;The ore-forming fluid was precipitation affected magmatic water,and the materials came from the Earth's mantle which were partly mixed by the crustal matters.3.The metallogenetic mechanisms are different between the earlier and the later mineralization period.Au may be migrate in the form of Au?HS?₂^-and subside affected by the water-rock reaction in the earlier one.The later one have two mineralization styles,the fine-disseminated type and the porphyry type,due to different evolutions of the alkaline granitic magma activity.The later one may be most affected by the late formation material.4.It is confirmed that they have different key ore controlling factors and ore guides of prospecting of two periods of gold mineralization which are intimately coupled with the early and late Carboniferous granitic magma activities.The earlier Ore bodies are jointly controlled by both the low potassium calc-alkaline granite body and near EW trending folds and faults,and Mg-OH and CO₃^2-were the main remote sensing alteration information.The Later Ore bodies are jointly controlled by both alkaline granite body and NW strike-slip,and Al-OH and CO₃^2-were the main remote sensing alteration information.Based on the theoretical study,two prospecting areas were delineated,from where gold ore bodies were found.