Early Jurassic intra-oceanic subduction initiation along the Bangong Meso-Tethys: Geochemical and geochronological evidence from the Shiquanhe ophiolitic complex, western Tibet

• Published in: Lithos Vol. 416-417; p. 106657
• Main Authors: Zeng, Xiao-Wen, Wang, Ming, Li, Hang, Chi, Peng, Shen, Di
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2022
• Subjects: Bangong-Nujiang suture; Fore-arc spreading; Geochemistry; Subduction initiation; Tibet; Subduction initiation; Geochemistry; Fore-arc spreading; Tibet; Bangong-Nujiang suture
• ISSN: 0024-4937; 1872-6143
• DOI: 10.1016/j.lithos.2022.106657

Due to the unclear tectonic setting of the Jurassic ophiolites within the Bangong-Nujiang suture, how and when intra-oceanic subduction initiated within the Bangong Meso-Tethys remain controversial. Based on the new petrological, geochemical, and geochronological data reported in this paper, ∼190–180 Ma MORB-like ophiolites and OIB-like mafic rocks were identified from the Shiquanhe ophiolitic complex in the western Bangong-Nujiang suture. The MORB-like gabbros exhibit strong light rare earth elements (LREEs) and heavy rare earth elements (HFSEs) depletion and were derived from partial melting of a highly refractory depleted mantle source with limited slab-derived fluids. The OIB-like mafic rocks are enriched in LREEs and HFSEs and were originated from the melting of upwelling asthenospheric mantle without subduction additions. The data for the MORB-like ophiolites reported in this paper and previously published data demonstrate the formation of Early Jurassic fore-arc ophiolites in response to the Early Jurassic intra-oceanic subduction initiation within the Bangong-Nujiang suture. The Early Jurassic OIB-like rocks formed in the extensional tectonic setting, together with regional geological evidence, suggest that the Early Jurassic initial subduction event within the Bangong Meso-Tethys resulted in broad upper plate extension. Our study not only reveals the intra-oceanic subduction initiation age of the Bangong Meso-Tethys but also implies that subduction initiation can cause strong extension in a wider region of the upper plate in the Tethys oceanic system, not just in the fore-arc region. •Discovery of MORB-like fore-arc ophiolite (190–185 Ma) in the Shiquanhe area.•Identifying of OIB-like gabbro-monzonite (185–180 Ma) in the Shiquanhe melange.•Confirming Early Jurassic intra-oceanic subduction initiation in Bangong Ocean.