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Yu S.-Y.,Hebei United University | Xu Y.-X.,Hebei United University | Xu Y.-X.,CAS Institute of Geology and Geophysics | Guo Z.-L.,No. 706 Geological Team | And 4 more authors.
Northwestern Geology | Year: 2011

Situated in the middle part of the Central Asian Orogenic Belt (CAOB), the Altay orogenic belt (AOB) is an important metallogenic belt in China. Many economic deposits are distributed along southern margin of the AOB, e.g. Kaktal Pb-Zn deposit, Mengku iron deposit, Abagong iron deposit, and Tiemuerte Pb-Zn deposit, etc. , which all occur in the Kangbutiebao Formation stratum comprising low grade metamorphosed volcanic rocks. Using the LA-ICP-MS zircon U-Pb method, we obtain that the age of granite is 412. 7±0. 78Ma and that of andesitic tuff is 411. 2±3. 4Ma age, representing the eruption time of the granite and the meta-andesitic tuff at the Supute Anticline. This age indicates that an intense volcanic activity may occur in the early Devonian in the Supute Anticline in the southern margin of the Altay, suggesting an active continental margin setting during this time. They belong to the same event of product and have the same dynamic background with the extensive development of volcanic in this area. The Result provides important theoretical basis for the study of the Paleozoic tectonic evolution at Supute anticline and the Southern margin of Altay.

Zhang H.,University of Science and Technology Beijing | Xu J.H.,University of Science and Technology Beijing | Guo X.J.,No. 706 Geological Team | Xiao X.,University of Science and Technology Beijing | And 3 more authors.
Yanshi Xuebao/Acta Petrologica Sinica | Year: 2015

The Talate Pb-Zn deposit, located on the southeast limb of the Kelan volcanic-sedimentary basin in the Altay, is hosted in the metamorphic rock series of the upper second lithological section of Lower Devonian Lower Kangbutiebao formation (D1k1 2), and its disposition and occurrence are controlled by the regional NW fault, the Keyingong fault and the Abagong fault. The Pb-Zn ore bodies occur as stratabound deposit, with the overprints of late sulfide-quartz veins. There were two obvious mineralization periods based on ore occurrences that are submarine volcanic sedimentary exhalation and metamorphic hydrothermal superimposition. Considering mineral assemblages and crosscutting relations of veins, metamorphic overprints could be divided into two stages. In the early stage, bedding lentoid quartz veins distributed in the chlorite schist and the leptite of the ore-bearing horizon. The appearance of disseminated pyritization and the phenomenon that layered sphalerite were replaced by pyrite and chalcopyrite is obvious under the microscope. In the late stage, pyrite-chalcopyrite quartz veins cut chlorite schist and leptite or the massive Pb-Zn ores and sulfides are sparse and disseminated. Fluid inclusions in sphalerite of the submarine volcanic sedimentary exhalation contain residual L-V inclusions, secondary L-V inclusions and a spot of H2O-CO2 inclusions trapped in tiny fissures. Primary L-V inclusions have Th,tot = 267 ∼ 334°C, and secondary H2O-CO2 inclusions have Tm,CO2 = -61.2 ∼ -60.2°C and Th,CO2 = 6.5 ∼ 11.0°C. The fluid inclusions in early vein quartz of metamorphic period consist of a great number of H2O-CO2 inclusions, carbonic (CO2 ± CH4) inclusions and a few H2O-CO2-NaCl inclusions. H2O-CO2 inclusions are homogenized at the temperature of 294 ∼ 368°C, with salinities of 5.5% ∼ 7.4% NaCleqv. The carbonic inclusions have Tm,CO2 of -60.1 ∼ -58.5 °C, and Th,CO2 of -4.2 ∼ 20.6 °C. Fluid inclusions in late pyrite-chalcopyrite quartz veins consist of a great number of H2O-CO2 inclusions, CO2 ± CH4, inclusions, and secondary L-V inclusions. H2O-CO2 inclusions have 142 ∼ 360°C of Th,tot and 2.4% ∼ 16.5% NaCleqv of salinities. Carbonic inclusions have -61.5 ∼ -57.3°C of Tm,CO2, -27.0 ∼ -20.6°C and 27.1 ∼ 28.7°C of Th,CO2, and secondary L-V inclusions have -9.8 ∼ -1.3°C of Tm,ice and 205 ∼ 412°C of Th,tot. Regional CO2-rich fluids came from the orogeny of the Kelan basin, and affected metamorphism of ores and wall rocks, as well as metal enrichment. Deformed and metasomatic textures of ore in the Talate deposit and abundant CO2-rich fluids may explain that metamorphic fluids participate in the superimposed reformation and possess characteristic of multi-stage. The P-T trapping conditions of CO2-rich fluids coincide with those of late or post regional metamorphism.

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