Trace-element characteristics of east–west mantle geochemical hemispheres - 09/05/19

Doi : 10.1016/j.crte.2018.09.007

Hikaru Iwamori ^a,^b,^c,^⁎ , Hitomi Nakamura ^b,^c,^d,^e, Masaki Yoshida ^f, Takashi Nakagawa ^g, Kenta Ueki ^b, Atsushi Nakao ^a, Tatsuji Nishizawa ^b,^c, Satoru Haraguchi ^b
^a Earthquake Research Institute, The University of Tokyo, 1-1-1 Yoyoi, 113-0032 Bunkyo, Japan
^b Department of Solid Earth Geochemistry, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, 237-0061 Yokosuka, Japan
^c Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, 152-8550 Meguro, Japan
^d Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, 305-8568 Tsukuba, Japan
^e Chiba Institute of Technology, ORCeNG, 2-17-1 Tsudanuma, 275-0016 Narashino, Chiba, Japan
^f Department of Deep Earth Structure and Dynamics Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, 237-0061 Yokosuka, Japan
^g Department of Earth Sciences, The University of Hong Kong, Pokfulam, Hong Kong

^⁎Corresponding author at: Earthquake Research Institute, The University of Tokyo, 1-1-1 Yoyoi, 113-0032 Bunkyo, Japan.The University of Tokyo, Earthquake Research Institute1-1-1 YoyoiBunkyo113-0032Japan

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Abstract

Recent statistical analyses on the isotopic compositions of oceanic, arc, and continental basalts have revealed that the Earth's mantle is broadly divided into eastern and western hemispheres. The present study aimed to characterize the isotopically defined east–west geochemical hemispheres using trace-element concentrations. Basalt data with Rb, Sr, Nd, Sm, Pb, Th, and U in addition to the isotopic ratios ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb were selected mostly from the GEOROC and PetDB databases. A total of 4787 samples were used to investigate the global geochemical variations. The results show that the wide trace-element variations are broadly explained by the melting of melt-metasomatized and fluid-metasomatized mantle sources. The larger amount of the fluid component derived from subducted plates in the eastern hemisphere than that in the western hemisphere is inferred from the basalts. These characteristics support the hypothesis that focused subduction towards the supercontinent created the mantle geochemical hemispheres.

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Keywords : Mantle, Hemisphere, Isotope, Trace element, Fluid

Plan

Introduction

Data and methods

Results

Trace element variations

Relationships between trace elements, isotopic ratios and ICs

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Vol 351 - N° 2-3

P. 209-220 - février 2019 Retour au numéro

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On the implications of the coupled evolution of the deep planetary interior and the presence of surface ocean water in hydrous mantle convection
Takashi Nakagawa, Hikaru Iwamori

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Trace-element characteristics of east–west mantle geochemical hemispheres - 09/05/19

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