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The origin and geodynamic significance of the Mesozoic dykes in eastern continental China.

Kong, Juanjuan and Niu, Yaoling and Sun, Pu and Xiao, Yuanyuan and Guo, Pengyuan and Hong, Di and Zhang, Yu and Shao, Fengli and Wang, Xiaohong and Duan, Meng (2019) 'The origin and geodynamic significance of the Mesozoic dykes in eastern continental China.', Lithos., 332-333 . pp. 328-339.

Abstract

We sampled 22 Mesozoic dykes in eastern continental China and carried out a detailed study on these samples, including KAr and zircon UPb geochronology, and elemental and Sr-Nd-Pb-Hf isotope geochemistry. Their KAr and zircon ages of 130–110 Ma are broadly consistent with the timing of the lithosphere thinning and the emplacement ages of widespread granitoids in the vast region, explicitly pointing to a common cause in space and time. The dykes represent evolved alkaline basaltic melts intruding the Mesozoic granitoids. Their rare earth element (REE) and multi-element patterns differ from the present-day ocean island basalts (OIB), but show strong arc-like signatures (e.g., enrichment in Rb and Pb and depletion in Nb, Ta and Ti). They show high (87Sr/86Sr)i (0.7048 to 0.7103), low εNd(t) (−12.3 to −5.7), low εHf(t) (−16.5 to −8.0) and low (206Pb/204Pb) i (18.79–18.85). These Mesozoic dykes are best understood as resulting from melting of geochemically enriched sub-continental lithospheric mantle (SCLM), whose geochemical enrichment is consistent with prior metasomatism with the agent being hydrous melt coming from subduction of the Paleo-Pacific plate at ~120 Ma or earlier. Similar to the present-day situation, the paleo-Pacific slab may have also existed stagnant in the mantle transition zone in the Mesozoic. The slab dehydrated and released water in the form of hydrous melt that percolated through and metasomatized the mantle lithosphere, and weakened the base of the lithosphere while producing basaltic melts that evolved to intermediate-felsic compositions of these dykes. The basaltic magmas that underplated and melted the lower crust to generate the widespread Mesozoic granitoids in eastern continental China.

Item Type:Article
Full text:(AM) Accepted Manuscript
Available under License - Creative Commons Attribution Non-commercial No Derivatives.
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1016/j.lithos.2019.02.024
Publisher statement:© 2019 This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Date accepted:27 February 2019
Date deposited:06 March 2019
Date of first online publication:06 March 2019
Date first made open access:06 March 2020

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