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Zhang Y.,China University of Geoseienees | Zhang Y.,Chengdu Institute of Geology and Mineral Resources | Wang Q.F.,China University of Geoseienees | Zhang J.,China University of Geoseienees | And 2 more authors.
Acta Petrologica Sinica | Year: 2012

Based on regional geological settings and characteristics of ore geology, this article made research on element geochemistry, fluid inclusion geochemistry and isotope geochemistry to make an estimate of the origins of ore-forming materials and fluids as well as metallogenic physicochemical conditions for Ajialongwa gold deposit located in Ganzi-Litang suture zone. It was hosted in the Ajialongwa fracture zone that developed at Himalayan stage and secondary to the Rize-Samalongwa deep fault, and the ore-hosting rock was ophiolite of Upper Triassic Waneng Formation. Ore minerals were mainly arsenopyrits and arsenian pyrits, fine disseminated of the distribution, while gangue minerals included quartzes, carbonate minerals, seristes, and so on. Mineralizd element association was Au, As, Sb, W, B and Hg. Chondrile normalized rare earth element patterns of ore and host rocks as well as δ 34S and Pb isotope compositions of their sulfides were consistent (δ 34S = - 13.249‰ ∼ - 8.091‰; the composition of Pb isotope was near to the growth curve of upper crust in Zartman graphic), proving that the ore-forming materials were sourced from host rocks. There were only single- and two-phases aqueous ore-forming fluid inclusions in quartzes and calciles of mineralization stage (the H 2O content was 91.80 mol% ∼ 97.63mol% ), which were low in homogenous temperature (T h = 120 ∼ 215°C), salinity (0.18% ∼ 6.16% NaCleqv), CO 2 (2.015 mol% ∼ 7.297mol% ) and trapping pressure (2.21 ∼ 19.62bar) ; the ore-forming fluids were in weak reduction, which parameters ranged from 0.087 to 0.230; the δD values ranged from - 124.243‰ to - 114.968‰, and the δ 18O from -0.36‰ to 1.91‰, which variation ranges were narrow. It not only showed the ore-forming fluids were meteoric water, having taken circulation at shallow depth, but also reflected metallogenic physicochemical conditions. The evidences, including ore mineral assemblage, fluid inclusions temperature and compositions, elemental and isotopic features of ores, all supported a Carlin-like type genesis for the Ajialongwa deposit possibly formed in Cenozoic.

Ma G.,Changchun Institute of Technology | Liu F.,Henan Institute of Geology Survey | Su L.,China University of Geoseienees | Han Y.,China University of Geoseienees | Wang Q.,Jilin University
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2013

The Xiaoqinling area is an important composition of southern segment of the Trans-North China Orogen within the North China craton. It is of an important significance to study construction, metamorphism, especially magmatism for revealing tectonic history of the Xiaoqinling area during the Paleo-to Mid-Proterozoic. This paper reports zircon LA-ICP-MS U-Pb dating results from the Proterozoic syenite dyke in the northern Xiaoqinling Mt. The dating results indicate that the syenite formed in(1831.0±6.8) Ma (95% conf., MSWD = 0.37), i. e., the Paleoproterozoic. Combined with the published data, we consider that the syenite from the Xiaoqinling Mt. formed under a crust thinning environment related to a Larger Igneous Province.

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