Geochemistry and age of seamounts in the West Pacific: mantle processes and petrogenetic implications
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Geochemistry and age of seamounts in the West Pacific: mantle processes and petrogenetic implications Limei Tang1, 2, Yanhui Dong1, 2*, Fengyou Chu1, 2, Ling Chen1, 2, Weilin Ma1, 2, Yonggang Liu3 1 Key Laboratory of Submarine Geosciences, Ministry of Natural Resources, Hangzhou 310012, China 2 Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China 3 Guangzhou Marine Geological Survey, Ministry of Natural Resources, Guangzhou 510760, China
Received 3 May 2017; accepted 20 October 2017 © Chinese Society for Oceanography and Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract
Research on seamounts provides some of the best constraints for understanding intraplate volcanism, and samples from seamounts reveal crucial evidence about the geochemical makeup of the oceanic mantle. There are still many seamounts in the West Pacific Seamount Province (WPSP) that have not been studied, meaning their ages and geochemistry remain unknown. A better understanding of these seamount trails and their evolutionary history, investigated with age and geochemistry data, will enable better understanding of the geological processes operating underneath the Pacific Ocean Plate. Here, new 40Ar/39Ar ages and trace element and Sr-Nd-Pb isotopic data for seven basalt rocks from four seamounts in the WPSP are provided. Chemically, these rocks are all Oceanic Island Alkali basalt (OIA type); analysis of olivine phenocrysts shows that the magmas experienced strong olivine fractionation and changed from olivine + plagioclase to olivine + plagioclase + clinopyroxene cotectic during their evolution. Rare earth element (REE) patterns and a spider diagram of the samples in this study show OIB (Ocean Island Basalt) like behavior. The range of 87Sr/86Sr values is from 0.704 60 to 0.706 24, the range of 206Pb/204Pb values is from 18.241 to 18.599, and the range of 143Nd/144Nd values is from 0.512 646 to 0.512 826; together, these values indicate magma sources ranging from EMI to EMII. Finally, new 40Ar/39Ar age data show that these seamounts formed at ~97 and ~106 Ma, indicating that some may have undergone the same formation processes as seamounts in the eastern part of the Magellan Seamount Trail, but other seamounts likely have different origins. Key words: 40Ar/39Ar ages, geochemistry, magmatic evolution, basalts, West Pacific Citation: Tang Limei, Dong Yanhui, Chu Fengyou, Chen Ling, Ma Weilin, Liu Yonggang. 2019. Geochemistry and age of seamounts in the West Pacific: mantle processes and petrogenetic implications. Acta Oceanologica Sinica, 38(1): 71–77, doi: 10.1007/s13131-019-1371-0
1 Introduction Since the publication of the deep-rooted mantle plume hypothesis (Morgan, 1971, 1972) and the elegant explanation of volcanic age progression of the Hawaii–Emperor seamount chain in the Pacific (Clague and Dalrymple, 1989), mantle plumes and hotspots have been widely used to explain mantle anomalies within the interior of a plate. However, over the past two decades, the hotspot hypothesis has been subje
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