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Zhang Y.,CAS Institute of Geology and Geophysics | Zhang Y.,University of Chinese Academy of Sciences | Liang G.L.,Xinjiang Bureau of Geology and Mineral Resource | Qu X.,Xinjiang Bureau of Geology and Mineral Resource | And 6 more authors.
Acta Petrologica Sinica | Year: 2010

Granite porphyry in the Sangdewulan copper-molybdenum district in the Qiongheba area, East Junggar was characterized by the abundance of sanidine and quartz phenocrysts with intragranular fractures and fractured core zircons, which was formed in a pre- emplacement magma chamber. Zircon U-Pb dating results suggest that the fractured zircons formed at age of about 442. 2 ± 3. 5Ma, and the rim zircons at about 412. 7 ± 3. 3Ma. The age of about 413Ma shows the time of emplacement and crystallization of the granite porphyry. Hf isotopic data of zircons suggest that the fractured cores and rim had a similar value of εHfand tDM2, and were most possibly derived from a same magma resources. This indicates that magmatic activity in the Qiongheba arc appeared at least from 442 Ma in the Early-Paleozoic era. High εHf(t) value (10. 3 ∼ 15. 1) and relative big model ages (tDM2 =469 ∼761Ma) suggest that magma formed granite porphyry in the Sangdewulan district were likely derived from the remelting of Late-Proterozoic-Ordovician basaltic crust.

Xue C.,China University of Geosciences | Chi G.,University of Regina | Zhao X.,China University of Geosciences | Wu G.,China University of Geosciences | And 2 more authors.
Geoscience Frontiers | Year: 2015

The Halasu area is located in the southeastern margin of the Chinese Altai in Xinjiang, China. It is part of the Altaid orogenic collage where a number of porphyry-type Cu-Mo-Au deposits have been discovered in recent years. Geological mapping and drilling indicate the presence of various mineralized porphyritic intrusions in the Halasu Cu-Au deposit, which is currently under exploration. U-Pb dating of zircon crystals from four different mineralized porphyries reveals three significantly different ages of magmatic intrusion, i.e., ca. 372-382 Ma granodioritic porphyry and porphyritic granite, ca. 266 Ma quartz monzonitic porphyry, and ca. 216 Ma quartz dioritic porphyry. Re-Os dating of molybdenite from veinlet-dissemination ores in the granodioritic porphyry yields an age of mineralization of ca. 377 Ma, and Ar-Ar dating of K-feldspar from K-feldspar-quartz-chalcopyrite veins produces ages of ca. 269 and ca. 198 Ma. The mineralization (and alteration) ages correspond broadly to the three episodes of magmatic intrusion, suggesting three overprinting porphyry mineralization events that are significantly separated in time. The first episode of porphyry intrusion and mineralization may be related to the magmatic arc being above a plate subduction zone, and the second was formed in a late-collisional environment during the closing of the Junggar Ocean, whereas the third episode of mineralization took place in the post-collisional stage. This case study suggests that in orogens where major porphyry deposits have been found in magmatic arc environments, the potential of discovering late- to post-collisional porphyry deposits cannot be neglected; conversely, in orogens where most porphyry deposits have late- to post-collisional ages, more attention should be paid to porphyries that were formed earlier in magmatic arc environments. © 2015 China University of Geosciences (Beijing) and Peking University.

Lu Q.,Xinjiang Bureau of Geology and Mineral Resource | Lu Q.,Xinjiang Institute of Geotechnical Investigation | Dong W.,Xinjiang Architectural Design Institute
Shuili Xuebao/Journal of Hydraulic Engineering | Year: 2015

As one of the main geo-hazards in mountain regions, rock fall usually occurs in a sudden and brings about serious damage. Geological analysis as well as mathematical calculation and Rocfall Software are used to study the rock fall mechanism as well as stability and movement features. In addition, the preventive methods are put forwards. The research shows that the structural plains formed in the diagenesis period have been expanded and finally broken by the continuous geological process and serious freezing-thawing effect. The instability of rock fall will be aggravated by external factors such as rain/snow and earthquake according to the calculation results. The rock fall movement contains casting, crashing, bouncing and rolling. The maximum bouncing height is 11. 3m and the maximum motion energy is 304.6 kJ. Based on the analysis, the initiative and passive prevention plan is carried out to treat with the rock falls, meanwhile, to avoid disfiguring the landscape. ©, 2015, Shuili Xuebao/Journal of Hydraulic Engineering. All right reserved.

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