Alaskan-type Kedanshan intrusion (central Inner Mongolia, China): Superimposed subduction between the Mongol-Okhotsk and Paleo-Pacific oceans in the Jurassic

Dong, Jinlong; Song, Shuguang; Wang, Mingming; Allen, Mark B.; Su, Li; Wang, Chao; Yang, Liming; Xu, Bei

Abstract

The Xing’an-Inner Mongolia accretionary belt in the eastern Central Asian Orogenic Belt (CAOB) was produced by the subduction of three oceanic plates: the Paleo-Asian, Mongol-Okhotsk and Paleo-Pacific oceanic plates. The interactions between these plates remain unclear. Here we report an Alaskan-type ultramafic-mafic intrusion in the Kedanshan area, central Inner Mongolia, China. The main lithologies of this intrusion include cumulate dunite, pyroxene peridotite, olivine pyroxenite and cumulate gabbro, with late gabbroic/anorthositic dykes. Minerals and whole-rock compositional variations display characteristics of an arc cumulate trend (Alaskan-type), through fractional crystallization of Mg-rich and hydrous basaltic magma associated with oceanic subduction. Zircons from two gabbro samples yield Early Jurassic ages of 193 ± 6 Ma and 179 ± 4 Ma, respectively. We conclude that this ultramafic-mafic complex is an accumulated intrusion from an arc-related, high-Mg magma chamber above a supra-subduction zone. Considering the ages, location and tectonic setting of the complex, we suggest that it was most likely generated by melting of a large and triangle-shaped mantle wedge during superimposed subduction between the Mongol-Okhotsk and the Paleo-Pacific oceanic plates in the Jurassic.

Citation

Dong, J., Song, S., Wang, M., Allen, M. B., Su, L., Wang, C., …Xu, B. (2018). Alaskan-type Kedanshan intrusion (central Inner Mongolia, China): Superimposed subduction between the Mongol-Okhotsk and Paleo-Pacific oceans in the Jurassic. Journal of Asian Earth Sciences, 167, 68-81. https://doi.org/10.1016/j.jseaes.2017.11.010

• Journal Article Type: Article
• Acceptance Date: Sep 24, 2017
• Online Publication Date: Nov 4, 2017
• Publication Date: Nov 30, 2018
• Deposit Date: Nov 22, 2017
• Publicly Available Date: Nov 4, 2018
• Journal: Journal of Asian Earth Sciences
• Print ISSN: 1367-9120
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 167
• Pages: 68-81
• DOI: https://doi.org/10.1016/j.jseaes.2017.11.010
• Public URL: https://durham-repository.worktribe.com/output/1343458