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Effects of decarbonation on elemental behaviors during subduction-zone metamorphism: Evidence from a titanite-rich contact between eclogite-facies marble and omphacitite

Xiao, Y.Y.; Niu, Yaoling; Zhang, H.F.; Wang, K.-L.; Iizuka, Y.; Lin, J.Y.; Tan, Y.L.; Xu, Y.J.

Effects of decarbonation on elemental behaviors during subduction-zone metamorphism: Evidence from a titanite-rich contact between eclogite-facies marble and omphacitite Thumbnail


Authors

Y.Y. Xiao

Yaoling Niu

H.F. Zhang

K.-L. Wang

Y. Iizuka

J.Y. Lin

Y.L. Tan

Y.J. Xu



Abstract

In this paper, we show the effects of subducted carbonates on geochemical processes during subduction-zone metamorphism (SZM) through the study of an eclogite-facies marble coexisting with metabasite from the ultrahigh pressure metamorphic belt of the Chinese Western Tianshan orogen. Between the marble and metabasite is a titanite-rich contact resulting from fluid-facilitated metamorphic reactions between the two lithologies, and recording elemental changes of geodynamic significance. Because this titanite-rich contact is dominated by titanite (an important host for high field strength elements, HFSEs) without white micas (an important host for large ion lithophile elements, LILEs), HFSEs are largely conserved in titanite whereas LILEs are moved away. This observation emphasizes the potential significance of subducting carbonate in retaining HFSEs in the slab through the formation and stabilization of titanite, contributing to the characteristic “arc signature” unique to subduction-zone magmatism (i.e., high LILEs, low HFSEs). The implicit assumption in this interpretation is that the observed lithological assemblage represents residues of subducting oceanic crust that has undergone major episodes of dehydration. Subducted carbonates also have significant implications for the origin of mantle isotopic heterogeneity as revealed from oceanic basalts.

Citation

Xiao, Y., Niu, Y., Zhang, H., Wang, K., Iizuka, Y., Lin, J., …Xu, Y. (2017). Effects of decarbonation on elemental behaviors during subduction-zone metamorphism: Evidence from a titanite-rich contact between eclogite-facies marble and omphacitite. Journal of Asian Earth Sciences, 135, 338-346. https://doi.org/10.1016/j.jseaes.2017.01.006

Journal Article Type Article
Acceptance Date Jan 11, 2017
Online Publication Date Jan 12, 2017
Publication Date Jan 12, 2017
Deposit Date Feb 6, 2017
Publicly Available Date Mar 29, 2024
Journal Journal of Asian Earth Sciences
Print ISSN 1367-9120
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 135
Pages 338-346
DOI https://doi.org/10.1016/j.jseaes.2017.01.006

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