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Yang G.,Changan University | Li Y.,Changan University | Yang B.,Changan University | Liu Z.,Changan University | And 2 more authors.
Earth Science Frontiers | Year: 2013

As a part of Central Asian Orogenic Belt (CAOB), the West Junggar is located at the southern margin of the CAOB. Several ophiolitic mélanges were formed and preserved in the West Junggar. The Darbut ophiolitic mélange (DOM) in the West Junggar is the largest and one of the best-preserved Paleozoic ophiolitic mélanges in the CAOB. Harzburgite, lherzolite, dunite, chromitite, troctolite, gabbro, diabase, pillow lava, massive basalt, and chert occurred as blocks within the serpentinite mélange. Based on petrology, petrography, isotopic geochronology and geochemical analysis for the alkaline basalt in the DOM, the alkaline basalt yielded a weighted mean 206Pb/238U age of (375±2) Ma by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), suggesting a Late Devonian emplacement. Furthermore, the alkaline basalt have typical geochemical characteristics to those of OIB, with moderate SiO2 (45.24%~49.86%), high MgO (2.45%~6.85%), TiO2 (3.17%~3.77%) and Na2O+K2O (2.37%~5.34%), characterized by alkaline basalt. The rare earth element (REE) and trace element distribution patterns are similar to those of oceanic island basalt (OIB), with light REE (LREE) and large ion lithophile element (LILE, Rb, Ba, Th) enrichment, no obvious high field strength element (HFSE, Zr, Hf, Nb, Ta) negative anomaly, indicating the origin from enriched mantle that contains 5%~10% spinel and garnet lherzolite partial melting. These observations, in combination with sedimentary and volcanic rocks, and previous work in this region, indicate that the alkaline basalt from the DOM might be correlated with Late Devonian mantle plume-related magmatism of ocean island setting within the ocean floor. That is to say, the alkaline basalt from the DOM is the product of a Late Devonian mantle plume, showing that the Late Devonian mantle plume-related magmatism must exist in the CAOB. If the plume model as proposed here is correct, it would suggest that mantle plume activity might have significantly contributed to the crustal growth in the CAOB. Source

Li Y.,Changan University | Li Y.,MLR Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits | Wang Z.,Changan University | Duan F.,Changan University | And 4 more authors.
Geotectonica et Metallogenia | Year: 2016

The relationship clearly show orogeny-coupled basin formation between Wuerkashier Mountain and E Min basin in West Junggar. The boundary of the basin is somewhat parallel to the orogenic belt. The sedimentary rocks in the "mountain" area include the Silurian-Carboniferous marine terrigenous clastic rocks and volcanic rocks, whereas in the "basin" area sedimentary rocks consist of the Permian continental molasse and Neogene red glutenite and accumulation of Quaternary river terraces, with a typical marine-continental double layered structure. The edge of the basin is limited by the Barleik foreland thrust belt. "Mountain" area develop such thrust nappe as shovel type thrust fault, snakeheads structure and imbricate fan structure. This indicates that the combination of "basin"-"mountain" is a typical foreland basin system. E Min foreland basin formed in the Early Permian, and belongs to the "Premature" foreland basin, which is characterized by weak impact of the later thrust deformation and obvious features of the early structure of foreland basin. This achievement provides important information for basin analysis, tectonic evolution, sedimentation and orogeny-coupled basin formation of the E Min basin as well as the West Junggar basin. © 2016, Science Press. All right reserved. Source

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