Japan Geoscience Union Meeting 2024

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[J] Oral

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

[S-CG45] Petrology, Mineralogy & Resource Geology

Thu. May 30, 2024 3:30 PM - 4:45 PM 302 (International Conference Hall, Makuhari Messe)

convener:Keisuke Fukushi(Institute of Nature & Environmental Technology, Kanazawa University), Tatsuo Nozaki(Submarine Resources Research Center, Research Institute for Marine Resources Utilization, Japan Agency for Marine-Earth Science and Technology), Yui Kouketsu(Department of Earth & Planetary Sciences, Graduate School of Environmental Studies, Nagoya University), Yu Nishihara(Geodynamics Research Center Ehime University), Chairperson:Keisuke Fukushi(Institute of Nature & Environmental Technology, Kanazawa University), Yu Nishihara(Geodynamics Research Center Ehime University), Yui Kouketsu(Department of Earth & Planetary Sciences, Graduate School of Environmental Studies, Nagoya University)

3:30 PM - 3:45 PM

[SCG45-06] Electrical conductivity of siderite and the effect of the spin transition of iron

*Izumi Mashino1, Takashi Yoshino1, Takaya Mitsui2, Kosuke Fujiwara2, Máté Garai3, Shigeru Yamashita1 (1.Institute for Planetary Materials, Okayama University, 2.National Institutes for Quantum Science and Technology, 3.The University of the South)

Keywords:Siderite, The lower mantle, Electrical conductivity, Spin transition

Carbonates can be transported into the Earth’s deep interior through subducting slabs, and thus have been proposed as host minerals for carbon in the Earth’s mantle. Therefore, revealing the behavior of carbonates at extreme conditions is a key to understanding the deep carbon cycle. In this study, we have conducted electrical conductivity measurements of FeCO3 siderite under high pressure up to 62 GPa using diamond anvil cells in order to understand the nature and effect of iron spin transition and its influence on the geophysical properties of siderite, which is an end-member of major carbonate minerals. The results from Raman and Mössbauer spectroscopic measurements show that the high- to low-spin transition of iron occurs at around 50 GPa. A sharp decrease of the electrical conductivity was also observed at around 50 GP, which is associated with the iron spin transition. Although the stability of FeCO3 siderite may be limited under high-temperature conditions along with the mantle geotherm, solid solutions in the MgCO3-FeCO3 system, Mg1-xFexCO3, could be stable up to the pressure-temperature condition of the lowermost mantle. The pressure-temperature range of the iron spin transition of Mg1-xFexCO3 would be narrower than those of the major lower mantle minerals of ferropericlase and bridgmanite, and thus the drop of the electrical conductivity induced by the spin transition could be clearer under the lower mantle conditions. Therefore, the existence of Mg1-xFexCO3 may affect the observed heterogeneity of electrical conductivity in the mid-lower mantle.