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Slab break-off and the formation of Permian mafic-ultramafic intrusions in southern margin of Central Asian Orogenic Belt, Xinjiang, NW China

Citation

Song, XY and Xie, W and Deng, YF and Crawford, AJ and Zheng, WQ and Zhou, GF and Deng, G and Cheng, SL and Li, J, Slab break-off and the formation of Permian mafic-ultramafic intrusions in southern margin of Central Asian Orogenic Belt, Xinjiang, NW China, Lithos: An International Journal of Mineralogy, Petrology, and Geochemistry, 127, (1-2) pp. 128-143. ISSN 0024-4937 (2011) [Refereed Article]


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DOI: doi:10.1016/j.lithos.2011.08.011

Abstract

The Baishiquan and Pobei Early Permian mafic–ultramafic intrusions were emplaced into Proterozoic metamorphic rocks in the Central Tianshan and the Beishan Fold Belt, northern Xinjiang, NW China. The Baishiquan intrusion comprises mainly gabbro, and mela-gabbro sills occurring within and along the margins of the gabbro body. In the Pobei intrusion, two distinct gabbroic packages, a lower gabbro and the main gabbro, are intruded and overlain by small cumulate wehrlite bodies. Both intrusions are characterized by enrichments of large ion lithophile elements and Th and U relative to the high field strength elements, and show strong negative Nb and Ta anomalies and positive K and Pb anomalies, leading to higher Th/Yb and Nb/Yb than in mid-ocean ridge basalt and ocean island basalt. These features are comparable with subduction-related mafic rocks and post-collisional magmas. Geological and geochemical considerations indicate that the parental magmas of the two intrusions were derived from decompression melting of ascending asthenosphere and reacted with overlying subduction-modified lithospheric mantle. We believe that these parental magmas were generated by post-collisional extension along the Chinese Tianshan, perhaps triggered by slab break-off or delamination of thickened lithosphere. Relatively lower (143Nd/144Nd)i and higher (87Sr/86Sr)i than other Permian mafic–ultramafic intrusions in the eastern Chinese Tianshan indicate that the parental magmas of these two intrusions experienced significant contamination by old crustal rocks.

Item Details

Item Type:Refereed Article
Keywords: Central Asian Orogenic Belt; NW China; Permian; Mafic–ultramafic intrusion; Slab break-off
Research Division:Earth Sciences
Research Group:Geology
Research Field:Igneous and Metamorphic Petrology
Objective Division:Mineral Resources (excl. Energy Resources)
Objective Group:Mineral Exploration
Objective Field:Mineral Exploration not elsewhere classified
Author:Crawford, AJ (Professor Anthony Crawford)
ID Code:74871
Year Published:2011
Web of Science® Times Cited:48
Deposited By:Centre for Ore Deposit Research - CODES CoE
Deposited On:2011-12-14
Last Modified:2012-04-19
Downloads:2 View Download Statistics

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