Subduction-related metasomatic mantle source in the eastern Central Asian Orogenic Belt: Evidence from amphibolites in the Xilingol Complex,Inner Mongolia,China |
| |
| Institution: | 1. State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, Hubei, China;2. Geology and Geochemistry group, Department of Earth Sciences, VU University Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands;3. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;4. Institute of Earth Sciences, Academia Sinica, Taipei 115, Taiwan;5. Department of the Earth and Environmental Sciences, National Chung-Cheng University, Jiayi 621, Taiwan;1. College of Earth Sciences, Guilin University of Technology, Guilin 541004, China;2. The Institute for Geoscience Research (TIGeR), Department of Applied Geology, Curtin University, GPO Box U1987, Perth, WA 6845, Australia;3. School of Earth Science and Resources, Chang''an University, Shannxi, Xi''an 710054, China;4. The Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, School of Earth and Space Sciences, Peking University, Beijing 100871, China;5. Radiogenic Isotope Facility, School of Earth Sciences, The University of Queensland, Brisbane, QLD 4072, Australia;1. Department of Geology, Northwest University, Xi’an, 710069, China;2. Department of Earth Sciences, The University of Hong Kong, Pokfulam, Road, Hong Kong, China;3. Department of Geology and Environmental Science, University of Pittsburgh, Pittsburgh, Pennsylvania, USA;1. The Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, School of Earth and Space Sciences, Peking University, Beijing 100871, PR China;2. College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, PR China;1. Department of Earth Sciences, The University of Hong Kong, Hong Kong, China;2. Department of Geology and Environmental Science, University of Pittsburgh, Pittsburgh, USA;3. State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi''an, China |
| |
| Abstract: | The Central Asian Orogenic Belt (CAOB) formed mainly in the Paleozoic due to the closure of the Paleo-Asian oceanic basins and accompanying prolonged accretion of pelagic sediments, oceanic crust, magmatic arcs, and Precambrian terranes. The timing of subduction–accretion processes and closure of the Paleo-Asian Ocean has long been controversial and is addressed in a geochemical and isotopic investigation of mafic rocks, which can yield important insight into the geodynamics of subduction zone environments. The Xilingol Complex, located on the northern subduction–accretion zone of the CAOB, mainly comprises strongly deformed quartzo-feldspathic gneisses with intercalated lenticular or quasi-lamellar amphibolite bodies. An integrated study of the petrology, geochemistry, and geochronology of a suite of amphibolites from the complex constrains the nature of the mantle source and the tectono-metamorphic events in the belt. The protoliths of these amphibolites are gabbros and gabbroic diorites that intruded at ca. 340–321 Ma with positive εHf(t) values ranging from + 2.89 to + 12.98. Their TDM1 model ages range from 455 to 855 Ma and peak at 617 Ma, suggesting that these mafic rocks are derived from a depleted continental lithospheric mantle. The primitive magma was generated by variable degrees of partial melting of spinel-bearing peridotites. Fractionation of olivine, clinopyroxene and hornblende has played a dominant role during magma differentiation with little or no crustal contamination. The mafic rocks are derived from a Late Neoproterozoic depleted mantle source that was subsequently enriched by melts affected by slab-derived fluids and sediments, or melts with a sedimentary source rock. The Carboniferous mafic rocks in the northern accretionary zone of the CAOB record a regional extensional event after the Early Paleozoic subduction of the Paleo-Asian Ocean. Both addition of mantle-derived magmas and recycling of oceanic crust played key roles in significant Late Carboniferous (ca. 340–309 Ma) vertical crustal growth in the CAOB. Amphibolite–facies metamorphism (P = 0.34–0.52 GPa, T = 675–708 °C) affected these mafic rocks in the Xilingol Complex at ca. 306–296 Ma, which may be related to the crustal thickening by northward subduction of a forearc oceanic crust beneath the southern margin of the South Mongolian microcontinent. The final formation of the Solonker zone may have lasted until ca. 228 Ma. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
