Melt-Lithosphere Interaction Controlled Compositional Variations in Mafic Dikes from Fujian Province, Southeastern China
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ISSN 1674-487X
Melt-Lithosphere Interaction Controlled Compositional Variations in Mafic Dikes from Fujian Province, Southeastern China Zhuliang Lei
1
, Gang Zeng *1, Jianqiang Liu *2, Xiaojun Wang1, Lihui Chen1, Xiaoyu Zhang1, Jinhua Shi1
1. State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China 2. Institute of Marine Geology, College of Oceanography, Hohai University, Nanjing 210098, China Zhuliang Lei: https://orcid.org/0000-0002-8739-8060; Gang Zeng: https://orcid.org/0000-0002-2198-3646; Jianqiang Liu: https://orcid.org/0000-0002-3828-0189 ABSTRACT: Late Mesozoic magmatism in southeastern China has been widely considered to be related to the subduction of the Paleo-Pacific Plate. However, it remains controversial whether mafic rocks are derived from the lithosphere or the asthenosphere. Here we present a comprehensive study on mafic dikes from Fujian Province in southeastern China, aiming to understand their source. Two types of mafic rocks have been recognized based on their trace-element features. Type-I rocks show arc-like trace-elemental characteristics, while type-II rocks are distinguished by their relatively flat patterns in primitive-mantle-normalized trace-element diagram. Despite such differences between two types of rocks, these mafic dikes show two trends in the plots of 87Sr/86Sr(i) versus La/Nb, which can be explained by the influences of crustal contamination and melt-lithospheric mantle interaction, respectively. 87Sr/86Sr(i), La/Nb, Sr/Y and Zr/Y ratios of type-I rocks are significantly correlated to the thickness of the underlying lithosphere, and the signals of lithosphere are clearer with increasing lithospheric thickness. This highlights the important influences of melt-lithosphere interaction during their formation. Such observations also indicate that these mafic rocks are more likely to have been originated from the asthenosphere rather than the lithospheric mantle. KEY WORDS: mafic dike, lithospheric mantle, asthenosphere, melt-lithosphere interaction, southeastern China. 0
INTRODUCTION Widespread Late Mesozoic magmatism in southeastern China is generally related to the subduction of the Paleo-Pacific Plate (Wang et al., 2018; He and Xu, 2012; Li and Li, 2007; Zhou et al., 2006; Zhou and Li, 2000; Jahn et al., 1990; Jahn, 1974). As the products of subduction, most of the Mesozoic mafic rocks in southeastern China exhibit arc-like features, especially marked by the enriched large ion lithophile elements (LILEs) and light rare earth elements (LREEs) and relative depleted high field strength elements (HFSEs). However, the magma source of these mafic rocks (including basalts and diabases) is still controversial. In the past few decades, these mafic magmas are generally suggested to have been originated from a fluid/melt-metasomatized lithospheric mantle, and their source lithology is suggested to be peridotite, the most common *Corresponding authors: [email protected]; [email protected] © China University of
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