Japan Geoscience Union Meeting 2015

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Symbol S (Solid Earth Sciences) » S-CG Complex & General

[S-CG64] Ocean Floor Geoscience

Wed. May 27, 2015 6:15 PM - 7:30 PM Convention Hall (2F)

Convener:*Kyoko Okino(Ocean Research Institute, University of Tokyo), Keiichi Tadokoro(Research Center for Seismology, Volcanology and Earthquake and Volcano Research Center, Nagoya University), Osamu Ishizuka(Geological Survey of Japan, AIST), Tomohiro Toki(Faculty of Science, University of the Ryukyus), Narumi Takahashi(Research and Development Center for Earthquake and Tsunami, Japan Agency for Marine-Earth Science and Technology)

6:15 PM - 7:30 PM

[SCG64-P06] Petrological study on Marcus Island

*Takaomi KAWANO1, Naoto HIRANO2, Taisei MORISHITA3 (1.Graduate School of Science and Faculty of Science, Tohoku University, 2.Center for Northeast Asian Studies, Tohoku University, 3.Hydrographic and Oceanographic Department, Japan Coast Guard)

Keywords:Marcus-Wake seamount trails, seamount, WPSP, HFSE, superplume, alkali-basalt

Marcus-Wake seamount trail is located in West Pacific Seamount Province (WPSP), where the oceanic plate is oldest in the world, around 160 Ma Pacific plate. WPSP had occurred during Cretaceous and was reconciled with current active hotspots of French Polynesia in South Pacific. Marcus (Minami-tori) Island is located 50 km away from Marcus-Wake seamount trail to the north. Most of seamounts, particularly well-studied seamounts, are more voluminous than the edifice of Marcus Island, whereas no islands and atolls are found around the island within 500 km. In this study, mineralogical and whole rock analysis of lava samples, obtained in submarine survey of northwest flank of Marcus Island, are adopted in order to compare with volcanic samples from WPSP and South Pacific islands of active hotspot volcanism. High TiO2 in relic of chrome spinel indicates the typical intra-plate volcanism to be similar characteristics with those of WPSP. Major element compositions reveal normal-alkali basalts. Nb/Zr and Nb/Y ratios can classify the origins of shallow mantle plume, not in superplume as old Polynesian hotspots, like the Marcus-Wake seamounts of WPSP. Therefore, Marcus Island was produced from intraplate volcanism which differs from hotspot activities forming the Marcus-Wake seamounts.