Geology,Geochemistry And Metallogenesis Of The Tiyier Gold Deposit In Western Junggar,Xinjiang

The Tiyier gold deposit lies in the south of the Western Junggar Basin which locates in the northwest of the Daerbute fault.It is an andesitic porphyrite related magmatic hydrothermal deposit located in Hatu-Baogutu ore concentration area.It belongs a middle scale primary gold deposit with its gold resources reserves reaching8.05 tons.The major outcropped strata in the mining area are Carboniferous marine volcanic rocks.The ore-body is hosted in an andesite porphyrite vein and is obviously controlled by faults.The andesitic porphyrite and volcanic rocks are studied in detail through whole rock analyses of major and trace elements and H-O-C-S-Pb isotope analyses.Combining with the previous studies on Chronology and tectonic background,petrogenesis,the source of ore forming fluids and materials and the metallogenesis are disscussed.The main results of this study include:1.The volcanic rocks in the Tiyier mining area is complex and consists of basic,intermediate and acid igneous rocks and origined from mantle-sourced magma.The intermediate and acid igneous rocks located at the continental volcanic arc,and the basic igneous rocks located at the oceanic island arc.Andesitic porphyrite,highly differentiated(DI=76.01?85.71),is rich in alkali,K₂O and rare-earth elements(?REE=224.63?314.01?g/g)with intense fractionation(LREE/HREE=12.17?14.27)and belongs to alkaline series,showing characteristics of intermediate-acid igneous rocks from crustal source rock.They have the geochemistry characteristics of the continental volcanic arc.2.In different mineralization stage of ores,most of the?D and?¹⁸O of quartz are-61.5‰?-79.8‰and 4.45‰?9.65‰respectively,and two?¹³C_V-PDBof calcite are-2.6‰and-5.9‰,which suggests that the ore-forming fluid of the Tiyier gold deposit is mainly magmatic water and was added into a little fluid in the late stage.3.The sulfur isotope composition of most samples suggests the characteristic of magmatic origin(?³⁴S=-1.4‰?1.7‰).The lead isotope results are quite even,suggesting a source from the lowercrust.The ore material might come from juvenile fluids in magma and lower crust.4.The mineralization age(274±11Ma)of the Tiyier gold deposit was younger than the strata and andesitic porphyrite(369?355Ma).This deposit was formed under regional orogeny in the Permian,belongs to magmatic-hydrothermal type gold deposit.