Sediment recycling by continental subduction indicated by B-Hf-Pb-Nd isotopes from Miocene?Quaternary lavas in the northern margin of Tibet

Zhang, Xiu-Zheng, Wang, Qiang, Kerr, Andrew C. ORCID: https://orcid.org/0000-0001-5569-4730, Wei, Gang-Jian, Qi, Yue, Liu, Ying and Yang, Yu-Cheng 2023. Sediment recycling by continental subduction indicated by B-Hf-Pb-Nd isotopes from Miocene?Quaternary lavas in the northern margin of Tibet. Lithos 444-44 , 107109. 10.1016/j.lithos.2023.107109

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Abstract

Although it has been argued that sediment recycling plays an important role in the differentiation of the continental crust, boron (B) isotopic data does not support a direct input of subducted sediments into arc magmas. This raises questions about the viability of sediment recycling as a process in the differentiation of continental crust. Here, we report B isotopic data from Miocene–Quaternary lavas derived from different sources in the northern margin of Tibet. These lavas have high B contents and negative δ11B values close to those of continental sediments. Strongly peraluminous rhyolites have the highest B (93 to 1559 ppm) contents with negative δ11B (−9.7 to −17.9) values. Adakitic dacites and trachyandesites exhibit the lowest B (18 to 29 ppm) contents with markedly negative δ11B (−12.0 to −35.7) values whereas olivine leucitites have B (37.2 to 59.3 ppm) contents with negative δ11B (−8.3 to −15.6) values. These lavas also have enriched Hf-Pb-Nd isotopic compositions similar to those of sediments. This data, combined with numerical modelling and geophysical and tectonic data for Cenozoic continental subduction in the northern margin of Tibet, indicates that: (1) the strongly peraluminous rhyolites were generated by partial melting of mica-bearing continental sedimentary rocks subducted to the depth of mid-to-lower crust; (2) adakitic lavas were derived by partial melting of sediment-bearing thickened lower crust underwent dehydration and eclogites-facies metamorphism; and (3) olivine leucitites were generated by partial melting of enriched mantle metasomatized by sediment-bearing eclogite-facies crust-derived melts. Thus, at continental convergent margins, continental subduction is an important mechanism for sediment recycling and the evolution of continental crust.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
Publisher:	Elsevier
ISSN:	0024-4937
Date of First Compliant Deposit:	10 March 2023
Date of Acceptance:	1 March 2023
Last Modified:	11 Nov 2024 11:30
URI:	https://orca.cardiff.ac.uk/id/eprint/157659

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