Subducted oceanic slab break-off in a post-collisional setting: Constraints from petrogenesis of Late Carboniferous dykes in central West Junggar, Xinjiang, NW China

Gao, Rui, Li, Jinke, Kerr, Andrew C. ORCID: https://orcid.org/0000-0001-5569-4730, Wu, Tao, Xiao, Long, Wang, Guocan and He, Xinxing 2023. Subducted oceanic slab break-off in a post-collisional setting: Constraints from petrogenesis of Late Carboniferous dykes in central West Junggar, Xinjiang, NW China. Geological Magazine 160 (9) , pp. 1711-1741. 10.1017/S0016756823000663

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Abstract

Numerous Late Carboniferous – Early Permian dykes are found in West Junggar and represent an important part of the Central Asian Orogenic Belt. In this contribution, we use these dykes to assess the tectonic regime and stress state in the Late Carboniferous – Early Permian. The West Junggar dykes are mainly diorite/dioritic porphyrite with minor diabase and were formed in 324–310 Ma. They have been divided into two groups based on their orientation, petrology and geochronology. Group 1 dykes mostly comprise WNW-striking dioritic porphyrite and NE-striking diorite with minor diabase and resemble the Karamay-Baogutu sanukitoid. They were probably formed from depleted mantle at a relatively high temperature and pressure with the addition of 1–2% sediment/sedimental partial melt and 0–5% trapped oceanic crust-derived melts. Group 2 dykes are ENE-striking and are similar to sanukite in the Setouchi Volcanic Belt. These dykes were also derived from depleted mantle at a shallow depth but high temperature with the addition of 2–3.5% sediment/sedimental partial melt. Magma banding and injection folds in dykes and host granitoids indicate magma flow. Paleostress analysis reveals that both groups of dykes were formed in a tensile stress field. Their emplacement is favoured by presence of pre-existing joints or fractures in the host granitoids and strata. We conclude that large-scale asthenosphere mantle upwelling induced by trapped oceanic slab-off can explain the magmatism and significant continental crustal growth of West Junggar during Late Carboniferous to Early Permian.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
Publisher:	Cambridge University Press
ISSN:	0016-7568
Date of First Compliant Deposit:	23 October 2023
Date of Acceptance:	11 October 2023
Last Modified:	16 Jan 2024 13:44
URI:	https://orca.cardiff.ac.uk/id/eprint/163424

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