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Tashkent, Uzbekistan

Nurtaev B.,Institute of Geology and Geophysics | Kharin V.,Institute of Mineral Resources | McCann T.,University of Bonn | Valdivia-Manchego M.,University of Bonn
Journal of Geodynamics | Year: 2013

The Nuratau Fault Zone in eastern Uzbekistan forms part of the western prolongation of the Tien Shan, an extensive orogenic zone located along the margin of the Central Asian Orogenic Belt. The Nuratau region is geologically complex, forming part of the suture zone between the Kazakh-Kyrgyz continent and the Alai microcontinent. A model is proposed suggesting modified N-directed subduction model, where an extensive fold-and-thrust belt developed in the Nuratau region. This, coupled with significant transform activity would have resulted in major segmentation of the existing stratigraphy in the region, as well as the development of a foredeep basin to the north of the fold-and-thrust belt. Regional suturing and collision was variable. Indeed, the collisional history probably involved multi-phase subduction/accretion of various microcontinents, ancient island arcs, and fragments of oceanic islands. Final collision would have produced an eroding basinal high in the region of the Nuratau mountains, which issued sediment both northwards into the remnant basin of the Turkestan Ocean, but also to the south into the newly forming Amu Darya Basin. © 2013. Source

Zeng Q.,University of Western Australia | Zeng Q.,Institute of Mineral Resources | Mccuaig T.C.,University of Western Australia | Tohver E.,University of Western Australia | And 2 more authors.
Geological Journal | Year: 2014

The Qinling Orogen is located between the North China and South China cratons. The Mianlue Suture is the key boundary between the orogen and the South China Craton marking where the South China Craton subducted northward beneath the North China Craton during the late Triassic. Another older suture, the Shangdan Suture, divides the orogen into the North Qinling and South Qinling terranes. Our new geochronological data on eight granite plutons in the South Qinling Terrane indicate that the major phase of the Zhongchuan Granite is 219.5±2.1Ma, Luchuba is 217.1±1.0Ma, Baijiazhuang is 215.9±3.0Ma, Jiaochangba is 213.9±1.7Ma, Lvjing is 214.5±2.1Ma, Xiba is 215.6±1.8Ma, Wenquan is 217.3±2.1Ma and Fengxian is 240.9±1.0Ma. Compiled results reveal widespread magmatism began in the northwestern part of the South Qinling Terrane at ~240-250Ma and episodically progressed to the southeast in the North Qinling Terrane. Magmatism was then widespread throughout the South Qinling Terrane during the Late Triassic. A new division of Triassic intrusions has been proposed across the Qinling Orogen based on critical geochemical and geochronological differences. First, the western part of the South Qinling Terrane, (western South Qinling suite), is significantly enriched in large ion lithophile elements, including Cs, Rb, U, Th and K, whereas the eastern part of the South Qinling Terrane, (eastern South Qinling suite), has moderate enrichment in these elements. Second, there is an obvious transition from calcium to potassium enrichment in the Late Triassic western-South-Qinling suite, whereas the Late Triassic eastern South Qinling suite appears to follow a curved trajectory starting from high Na through K to high Ca. Third, the Ba and Sr concentrations of the western South Qinling suite have marked troughs, whereas the eastern South Qinling suites have relative enrichment of the two elements. The source of the Triassic magma becomes increasingly juvenile towards the east-southeast in the Qinling Orogen. Geochemical and isotopic data indicate that there are differences in the granites across the Chengxian-Huixian-Fengxian Fault within the western South Qinling Orogen, which highlight the tectonic significance of this northeast-trending fault that is now recognized as a significant boundary within the orogen. The identification of such a large-scale structure should attract some exploration attention, since this fundamental lineation is likely to be associated with some large mineral systems. © 2014 John Wiley & Sons, Ltd. Source

Qin Y.,Chinese Academy of Geological Sciences | Wang D.,Institute of Mineral Resources | Wu L.,Anhui Geological Survey | Wang K.,Anhui Geological Survey | Mei Y.,Yichang Institute of Geology and Mineral Resources
Acta Geologica Sinica | Year: 2010

Dongyuan W deposit is a newly-found large-scale scheelite deposit, which is also the biggest one in south of Anhui province. The discovery of the Dongyuan W deposit set the direction for mineral exploration and laid groundwork for further exploration. This paper preliminarily analyzed regional structural background and metallogenic controlling factors, firstly obtained U-Pb age of zircon by using SHRIMP. The results showed that ore-forming age of the granite-porphyry in the Dongyuan porphyry W deposit is 148. 6 ±1. 8 Ma (n = 16, MSWD=1. 5), and the granite porphyry rock was product of late Jurassic magmatic movement. The results also suggested that the regional tungsten mineralization might extend from South China to the Middle and Lower Reach of the Yangtze River. Source

Seltmann R.,Natural History Museum in London | Konopelko D.,Saint Petersburg State University | Biske G.,Saint Petersburg State University | Divaev F.,Institute of Mineral Resources | Sergeev S.,Russian Geological Research Institute VSEGEI
Journal of Asian Earth Sciences | Year: 2011

The Hercynian Tien Shan (Tianshan) orogen formed during Late Palaeozoic collision between the Karakum-Tarim and the Kazakhstan paleo-continents. In order to constrain timing of Hercynian post-collisional magmatism, 27 intrusions were sampled for U-Pb zircon dating along a ca 2000 km - long profile in Uzbekistan and Kyrgyzstan. The samples were dated utilizing sensitive high resolution ion microprobe (SHRIMP-II). The obtained ages, together with previously published age data, allowed the timing of Hercynian post-collisional magmatism to be constrained and interpreted in the context of the Paleozoic magmatic evolution of the region. Apart from Hercynian post-collisional magmatism, two older magmatic episodes have been recognized, and the following sequence of events has been established: (1) approximately 10 Ma after cessation of continuous Caledonian magmatism a number of Late Silurian-Early Devonian intrusions were emplaced in the Middle and Northern Tien Shan terranes between 420 and 390 Ma. The intrusions probably formed in an extensional back arc setting during coeval subduction under the margins of Caledonian Paleo-Kazakhstan continent; (2) the next relatively short Late Carboniferous episode of subduction under Paleo-Kazakhstan was registered in the Kurama range of the Middle Tien Shan. Calc-alkaline volcanics and granitoids with ages 315-300 Ma have distinct metallogenic affinities typical for subduction-related rocks and are not found anywhere outside the Middle Tien Shan terrane west of the Talas-Farghona fault; (3) the Early Permian Hercynian post-collisional magmatism culminated after the closure of the Paleo-Turkestan ocean and affected the whole region across terrane boundaries. The post-collisional intrusions formed within a relatively short time span between 295 and 280 Ma. The model for Hercynian post-collisional evolution suggests that after collision the Tien Shan was affected by trans-crustal strike-slip motions which provided suitable conduits for ascending asthenospheric material and heat influx in the crust. This produced both granitoid magmas and hydrothermal fluid flow. As a result post-collisional intrusions and orogenic Au deposits, known in the region, formed coevally and were tectonically controlled; (4) between 240 and 220 Ma a Triassic thermal event affected the region resulting in resetting and growth of new zircon grains which is detected on a regional scale. Probably the influx of heat into the crust during the Triassic was tectonically focused and varied significantly in different terranes. In the region under investigation the Triassic thermal event was not accompanied by any significant magmatic activity. Thus, after cessation of Hercynian post-collisional magmatism ca 280 Ma ago there was a long magmatically quiet period in the Tien Shan. © 2010. Source

Li H.,Institute of Mineral Resources | Wang X.,Institute of Mineral Resources | Ye H.,Institute of Mineral Resources | Yang L.,China National Offshore Oil Corporation
Acta Geologica Sinica | Year: 2012

The Mesozoic porphyry assemblage in the Jinduicheng area is a special molybdenum area in China, the Mo deposits, including the Jinduicheng, Balipo, Shijiawan, Huanglongpu, are distributed. The emplacement age and geochemical features of the granites in the Jinduicheng area can provide essential information for the exploration and development of the porphyry molybdenum deposit. In this study, we report LA-ICP-MS zircon U-Pb age and zircon Hf isotopic compositions of granite porphyries from the Jinduicheng area, and provide insights on the petrogensis and source characteristics of the granites. The results show that the zircon U-Pb ages of the Jinduicheng granite porphyry (143±1 Ma) and the Balipo granite (154±1 Ma), agree well with the Re-Os ages of molybdenite in the Jinduicheng molybdenum polymetallic deposit (139±3 Ma) and the Balipo molybdenum polymetallic deposit (156±2 Ma), indicating that the emplacement of granite porphyries occurred between Late Jurassic and Early Cretaceous. Zircons granite from the Jinduicheng area give the values mainly ranging from -10 to -16, and -20 to -24, respectively, corresponding to two-stage model ages (fane: mainly focused on 1.86-2.0 Ga, and 2.2-2.6 Ga, respectively) of zircons of the granite from the Jinduicheng values. The ore-forming materials are mainly derived from crust, with minor mantle substances. Zircons of the granite from the Balipo area give ε Hf (t) values ranging from -18 to -20, -28 to -38, and -42 to -44, respectively, corresponding to two-stage model ages (t dm2= mainly focused on 1.88-3.0 Ga, and 3.2-3.90 Ga, respectively), the ε Hf (t) values of the Jinduicheng porphyry more than that of the Balipo porphyry, and two-stage model ages (foiva) less than that of the BaUpo porphyry, shows that he source of the porphyries originated from ancient lower crustal materials in the Jinduicheng area, and mixed younger components, more younger components contributed for the source of the Jinduicheng porphyry. Source

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