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Mesozoic high-Mg andesites from the Daohugou area, Inner Mongolia : upper-crustal fractional crystallization of parental melt derived from metasomatized lithospheric mantle wedge.

Meng, Fanxue and Gao, Shan and Song, Zhaojun and Niu, Yaoling and Li, Xuping (2018) 'Mesozoic high-Mg andesites from the Daohugou area, Inner Mongolia : upper-crustal fractional crystallization of parental melt derived from metasomatized lithospheric mantle wedge.', Lithos., 302-303 . pp. 535-548.

Abstract

Mineral chemistry, major- and trace-element data, zircon U–Pb ages, and Sr–Nd isotopic data are presented for a suite of volcanic rocks from the Daohugou area, Ningcheng City, Inner Mongolia, on the northern margin of the North China Craton. Samples from the suite are of basaltic andesite to rhyolite in composition, with the rocks containing <60 wt% SiO2 have high MgO, Cr, and Ni contents, and classify as high-Mg andesites (HMAs). Zircons from a rhyolite yielded weighted mean 206Pb/238U age of 164 ± 1 Ma, indicating that the Daohugou volcanic suite is coeval with the Tiaojishan Formation of northern Hebei and western Liaoning Province. The HMAs have similar enriched-mantle I (EMI)-type isotopic compositions to each other, with low εNd (t) values, moderate (87Sr/86Sr) i ratios, enrichment in LREEs relative to LILEs, and depletion in HFSEs (e.g., Nb, Ta, Ti), indicating formation through protracted fractional crystallization of a common parental magma. The unusually low CaO contents and CaO/FeO ratios of olivine phenocrysts in the HMAs suggest that the parental melt was subduction-related. The results of Rhyolite-MELTS modelling indicates that HMAs may form through upper-crustal fractional crystallization from arc basalts. Therefore, the Daohugou HMAs were most likely formed through fractional crystallization of a parental melt derived from metasomatized lithospheric mantle at crustal depths. The addition of “water” to the cratonic keel may have played a key role in the destruction of the North China Craton.

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.2018.01.032
Publisher statement:© 2018 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:23 January 2018
Date deposited:06 February 2018
Date of first online publication:02 February 2018
Date first made open access:No date available

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