Mo isotope evidence for the significance of subducted continental crust in formation of post-collisional porphyry Cu deposits

Fan, Jing Jing, Wang, Qiang, Long, Xiao Ping, Wyman, Derek A., Kerr, Andrew C. ORCID: https://orcid.org/0000-0001-5569-4730, Li, Jie, Wang, Zi Long, Gong, Lin, Xu, Dong Jing, Yang, Qi Ji, Zhang, Le and Cui, Ze-Xian 2025. Mo isotope evidence for the significance of subducted continental crust in formation of post-collisional porphyry Cu deposits. Chemical Geology 680 , 122683. 10.1016/j.chemgeo.2025.122683 Item availability restricted.

PDF - Accepted Post-Print Version Restricted to Repository staff only until 12 February 2026 due to copyright restrictions. Download (5MB)

Abstract

Porphyry systems in continental collision belts contain substantial copper (Cu) and molybdenum (Mo) resources. However, unraveling their magma source compositions poses a significant challenge due to the superposition of previous oceanic subduction fingerprints. We report Mo isotope data on post-collisional (Oligocene–Miocene) Cu (Mo)-bearing porphyries (CBPs) and related barren-ore rocks (including Eocene granites and Miocene high-Mg diorites and ore-barren granites) in the eastern Gangdese belt, southern Tibet. The Eocene granites with high δ98/95Mo values (0.37–0.58 ‰) and K2O, Th contents originated from anoxic sediment-modified juvenile lower crust related to oceanic subduction. The Miocene high-Mg diorites with shoshonitic characteristic have extremely low δ98/95Mo of −1.20 ‰ to −0.92 ‰, possibly deriving from a lithospheric mantle metasomatized by slab melts from subducted Indian crust. By contrast, the CBPs show moderate and variable δ98/95Mo values (−0.85 ‰ to 0.34 ‰), reflecting either source or magma mixing of juvenile Asian lithosphere and subducting continental crust-derived melt components. The Miocene ore-barren granites have element compositions similar to the CBPs but are more Na-rich and have lower Th contents, slightly depleted Sr-Nd isotopes, and heavy Mo isotopes (−0.14 ‰ to 0.23 ‰), implying lower amounts of continental components in their magma source. Our Mo isotope data thus provides solid evidence for the incorporation of subducted Indian slab melts into the CBP magmas. Furthermore the CBPs contain more Indian components than the Miocene ore-barren granites, suggesting that the input of subducted continental crust melts is critical in the formation of post-collisional porphyry systems possibly by oxidizing the overlying fertile lithosphere.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Earth and Environmental Sciences
Publisher:	Elsevier
ISSN:	0009-2541
Date of First Compliant Deposit:	7 March 2025
Date of Acceptance:	11 February 2025
Last Modified:	10 Mar 2025 15:15
URI:	https://orca.cardiff.ac.uk/id/eprint/176706

Actions (repository staff only)

Edit Item