Geochemistry and petrogenesis of Early Carboniferous volcanic rocks in East Junggar,North Xinjiang: Implications for post-collisional magmatism and geodynamic process |
| |
| Institution: | 1. Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, School of Earth and Space Sciences, Peking University, Beijing 100871, China;2. Department of Geology, Saint Mary''s University, Halifax, Nova Scotia B3H 3C3, Canada;3. Geological Survey of Canada (Atlantic), Bedford Institute of Oceanography, P.O. Box 1006, Dartmouth, Nova Scotia B2Y 4A2, Canada;1. Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China;2. HKU Shenzhen Institute of Research and Innovation, Shenzhen, China;3. Xinjiang Research Center for Mineral Resources, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China;4. Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090, Russia;5. The Novosibirsk State University, Pirogova Street 2, Novosibirsk 630090, Russia;1. Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. Chinese Academy of Sciences Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China;4. Department of Geosciences, Auburn University, Auburn, AL 36849, USA;1. Chengdu Centre, China Geological Survey, Chengdu 610081, China;2. Ministry of Education Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, China;3. Southwest Petroleum University, School of Geoscience and Technology, Chengdu 610500, China;4. Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines, Department of Geology, School of Resources and Civil Engineering, Northeastern University, Shenyang 110819, China;5. China Deep Exploration Center, Chinese Academy of Geological Sciences, Beijing 100037, China;1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2. Economic Geology Research Centre (EGRU), College of Science, Technology & Engineering, James Cook University, Townsville, QLD, 4811, Australia;3. China University of Geosciences, Beijing 100083, China |
| |
| Abstract: | Early Carboniferous volcanic rocks in the Batamayineishan Formation overlie unconformably the molasse deposits and the ophiolitic mélanges and are restricted in narrow zones along both sides of the Kalamaili orogenic belt in North Xinjiang, southern Central Asian Orogenic Belt. These rocks demonstrate the post-collisional setting in East Junggar commenced in Tournaisian and also mark an important transitional period from the final amalgamation to late Paleozoic voluminous juvenile granitoids in East Junggar. The volcanic rocks are composed of basalt, basaltic andesite, andesite, trachyte and rhyolite. Both mafic and felsic rocks are characterized by enrichments in large ion lithophile elements, light rare earth elements and depletion in Nb and Ta, low initial 87Sr/86Sr and high, positive ?Nd(t). Three groups of mafic rocks have been identified: Shoshonitic group 1 has the highest MgO, CaO, Ni and Cr and the lowest Na2O, Al2O3, La, Ba, La/Yb and Ba/Th with primary magma features; group 2 calc-alkaline and high-K calc-alkaline mafic rocks have the lowest K2O, P2O5, Th and Th/Nb, and the highest TiO2; and group 3 (shoshonitic to potassic alkaline) has the highest K2O, P2O5, La, Ba, La/Yb and Th/Nb, and the lowest TiO2. The A-type-like felsic rocks were derived from the differentiation of the mafic magma. Geological and geochemical evidences indicate that the Batamayineishan Formation was generated from the process of slab breakoff (detachment). Group 1 samples are produced by decompressional melting of the upwelling asthenosphere mainly composed of spinel and garnet (50:50) lherzolite which has been enriched by overlying metasomatized lithosphere during ascent. Group 2 is derived from 5–10% partial melting of shallower spinel-bearing lithospheric mantle induced by the hot rising asthenosphere, where the contribution of slab-derived fluid is predominant. Low partial melting (3–5%) of the mantle wedge and/or thickened lithospheric mantle enriched by slab-derived components generates group 3. Slab breakoff as an important geodynamic process accounts for the post-collisional magmatism between 343.5 Ma–330 Ma, providing a model for post-collisional crust–mantle interaction in the CAOB. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
