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Zhang Q.,China University of Geosciences | Xue C.-J.,China University of Geosciences | Zhao X.-B.,China University of Geosciences | Feng B.,China University of Geosciences | And 5 more authors.
Geology in China | Year: 2015

The Asian gold belt extends into Western Tianshan Mountains, showing great prospecting foreground and potentiality. The Katebasu gold deposit is a newly-discovered large-sized deposit, with 87t gold reserves and 3.84 g/t average gold grade. The deposit is situated in a deformation band near the north Nalati fracture on the northern margin of the Middle Tianshan Mountains. Gold orebody, lenticular or tabular in form, is controlled by the alteration zone along with the brittle and ductile fracture zone in the monzonite granite. The center of the gold orebody is silicified rock with gold-bearing pyritization, and the edge is sericite chlorite epidote altered rock with gold-bearing pyritization. The pyrite and chacopyrite are main gold carriers, with ionic gold in pyrite, while embedded-gold and fissure-gold constitute the main forms in chacopyrite. The geological bodies of the Katebasu large-sized gold deposit consist of monzonite granite, with a (346.3±3.3) Ma zircon U-Pb concordia age, suggesting Early Carboniferous. The isochron age of the ore-bearing pyrite is (310.9±4.2) Ma, implying Late Carboniferous, appximately 35 Ma later than monzonite granite. The key to gold mineralization was the tectonic fluidization caused by the closure of South Tianshan Ocean and the collision of Tarim plate with Middle Tianshan landmass. Ore-forming fluids of gold were mesothermal to hyperthermal (270-390 °C) and low-middle salinity (7%-16% NaCl eq.) ones rich in C02, with the data δ18OH2O (V-SMOW)=1.6%O-6.4%O and δD H2O (V-SMOW)=-64%O-107%o, showing characteristics of deep metamorphism fluids. The average (187Os/188Os)i of the pyrite in gold ore is 1.449±0.052, and the REE patterns and Pb isotope (206Pb/204Pb=18.129-18.773,207Pb/204Pb=15.459-15.554,208Pb/204Pb=37.707-38.123) have similarity or relevance to the earth crust of the Middle Tianshan Mountains, suggesting that the metallogenic material was derived form the earth crust. The δ34S values of the sulfide are 6.92%o-12.15%o, implying that the S of the ore came from Thermochemical Sulfate Reduction (TSR) of the marine strata of Paleozoic. The Katebasu gold deposit was controlled by the shatter tectonic stresses between the Tarim plate and the Middle Tianshan zone in Late Carboniferous epoch, produced by the structure-altered Tianshan rock and belonging to the collision-orogeny gold deposit. The results achieved by the authors provide valuable guide for the continuous prospecting breakthrough in Western Tianshan Mountains of Xinjiang.

Yang W.-Z.,No. 1 Geological Survey Party | Xue C.-J.,China University of Geosciences | Zhao X.-B.,China University of Geosciences | Zhao S.-M.,No. 1 Geological Survey Party | And 8 more authors.
Geological Bulletin of China | Year: 2013

World-class Au-Cu deposits are distributed along Middle Tianshan Mountains of Uzbekistan and Kyrgyzstan. Special attention should be paid to Au-Cu prospecting in China's Middle Tianshan and its northern and southern edges. Recendy, a large Au-Cu deposit of Kateba'asu in Xinyuan County of Xinjiang was discovered by No.1 Geological Survey Party of Xinjiang Bureau of Geology and Mineral Exploration and Mining. The Kateba'asu Au-Cu deposit is located on the northern margin of the Middle Tianshan Mountains of Xinjiang, ~30 km southeast of Xinyuan County. Gold-copper mineralization mainly occurs in the alteration zone of Carboniferous monzonitic granite intrusion. Au-Cu ore bodies are a few to several thousand meters long and several to dozens of meters thick, assume tabular and lenticular forms, and have average grades of gold 3.84 g/t and copper 0.65%. The ore bodies in the upper part are mainly associated with gold mineralization and copper mineralization which increases with the depth. Ore minerals include pyrite and chalcopyrite, which are probably the main gold-bearing minerals. Gold-copper mineralization was closely related to the hydrothermal process after the emplacement of granite intrusions (e.g., monzonitic granite, alkali-feldspar granite, granodiorite). The Kateba'asu Au-Cu deposit possesses great economic value and also indicates the existence of high prospecting potential in the Middle Tianshan Mountains of west Xinjian. The discovery of Kateba'asu large Au-Cu deposit gives us an example of the new prospecting model, in which geological survey goes ahead and then guides the commercial exploration, thus finally realizing important breakthrough.

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