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1. Temperature gradients in high pressure multi-anvil cell.

Author

Moriguti, Takuya, Yoneda, Akira, and Ito, Eiji

Subjects
*HIGH temperatures, *FURNACES, *SEMICONDUCTORS, *TEMPERATURE
Abstract

Temperature gradient through cylindrical Re furnace set in an octahedral assembly for Kawai-type of the multi-anvil high pressure apparatus was examined at a central temperature of 2500°C and pressures of 10.4-12.4 GPa, based on coesite-stishovite phase boundary in SiO2. The axial temperature showed a parabolic curve, which is approximated by a quadratic function between the temperature differences from the temperature at the hotspot and the distance from the sample center, equivalent to the hotspot, ΔT = −258.7L2 −16.8L (r2 = 0.99), where ΔT (°C) is the temperature difference between the center and at a point, and L (mm) is the distance of the point from the center. The estimated temperature gradient is around 260°C/mm at 2500°C. Here, the factors that influence the temperature gradient, such as the sample temperature, the shape and the material of the furnace, and the design of the cell assembly, are also discussed. [ABSTRACT FROM AUTHOR]

Published
2024
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10. Melting phase equilibrium relations in the MgSiO3-SiO2 system under high pressures.

Author

Moriguti, Takuya, Yachi, Yusuke, Yoneda, Akira, and Ito, Eiji

Subjects
*PHASE equilibrium, *IRON alloys, *MELTING points, *DISPLAY systems, *EUTECTIC reactions
Abstract

Melting relations in the MgSiO3-SiO2 system have been investigated at 13.5 GPa using a Kawai-type multi-anvil apparatus. The system displays eutectic melting with the eutectic point located at SiO2/(SiO2+MgO) = 0.61 (in mol; which is denoted by XSi hereafter) and at 2350 ± 50 °C. Taking into account the eutectic compositions at lower pressures reported in previous studies, i.e., 0.556 at 1 GPa (Hudon et al. 2005) and 0.60 at 5 GPa (Dalton and Presnall 1997), the eutectic composition is slightly enriched in SiO2 with increasing pressure. The silica-rich eutectic composition is not consistent with the present peridotitic mantle composition (XSi = 0.43). Considering Si incorporation into iron alloys in a magma ocean, however, mass-balance calculations based on an E-chondrite model demonstrate that the silicate magma ocean could have XSi consistent with the present peridotitic mantle. [ABSTRACT FROM AUTHOR]

Published
2022
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12. Slab decarbonation and CO2 recycling in the Southwestern Colombian volcanic arc

Author

Universidad EAFIT. Departamento de Ciencias, Geología Ambiental y Tectónica, Marin-Ceron, Maria I., Moriguti, Takuya, Makishima, Akio, Nakamura, Eizo, Universidad EAFIT. Departamento de Ciencias, Geología Ambiental y Tectónica, Marin-Ceron, Maria I., Moriguti, Takuya, Makishima, Akio, and Nakamura, Eizo

Abstract

The contribution of subducted carbonate sediments to the genesis of the Southwestern Colombian arc magmas was investigated using a comprehensive petrography and geochemical analysis, including determination of major and trace element contents and Sr, Nd, Hf and Pb isotope compositions. These data have been used to constrain the depth of decarbonation in the subducted slab, indicating that the decarbonation process continues into the sub-arc region, and ultimately becomes negligible in the rear arc. We propose on the basis of multi-isotope approach and mass balance calculations, that the most important mechanism to induce the slab decarbonation is the infiltration of chemically reactive aqueous fluids from the altered oceanic crust, which decreasingly metasomatize the mantle wedge, triggering the formation of isotopically different primary magmas from the volcanic front (VF) with relatively high Hf-176/Hf-177, high Sr-87/Sr-86, negative values of epsilon Nd and lower Pb isotopes compared to the rear arc (RA). The presence of more aqueous fluids at the volcanic front may increase the degree of decarbonation into carbonate-bearing lithologies. Moreover, with increasing pressure and temperature in the subduction system, the decrease in dehydration of the slab, leads to cessation of fluid-induced decarbonation reactions at the rear arc. This development allows the remaining carbonate materials to be recycled into the deep mantle. (C) 2009 Elsevier Ltd. All rights reserved.

Published
2021

15. Melting phase equilibrium relations in the MgSiO3-SiO2system under high pressures

Author

Moriguti, Takuya, Yachi, Yusuke, Yoneda, Akira, and Ito, Eiji

Abstract

Melting relations in the MgSiO3-SiO2system have been investigated at 13.5 GPa using a Kawai-type multi-anvil apparatus. The system displays eutectic melting with the eutectic point located at SiO2/(SiO2+MgO) = 0.61 (in mol; which is denoted by XSihereafter) and at 2350 ± 50 °C. Taking into account the eutectic compositions at lower pressures reported in previous studies, i.e., 0.556 at 1 GPa (Hudon et al. 2005) and 0.60 at 5 GPa (Dalton and Presnall 1997), the eutectic composition is slightly enriched in SiO2with increasing pressure. The silica-rich eutectic composition is not consistent with the present peridotitic mantle composition (XSi= 0.43). Considering Si incorporation into iron alloys in a magma ocean, however, mass-balance calculations based on an E-chondrite model demonstrate that the silicate magma ocean could have XSiconsistent with the present peridotitic mantle.

Published
2022
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18. Comprehensive geochemical analyses of small amounts (< 100 mg) of extraterrestrial samples for the analytical competition related to the sample return mission MUSES-C

Author

Nakamura, Eizo, Makishima, Akio, Moriguti, Takuya, Kobayashi, Katsura, Sakaguchi, Chie, Yokoyama, Tetsuya, Tanaka, Ryoji, Kuritani, Takeshi, and Takei, Hiroyuki

Abstract

We have participated in the analytical competition related to the sample-return mission, MUSES-C of the ISAS, to be launched in May 2003 and returned in summer 2007. In this competition, we have determined major and trace element abundances and isotopes (as many as possible), both for two powdered samples provided by the ISAS and for chondrules separated from Allende meteorite as an additional demonstration of our high-spatial resolution analytical capabilities for fragment samples. 100 mg of each of the competition samples, 1C and 2C, were split into two fractions of approximately 30 and 70 mg for the determinations of elemental abundances and the isotope analyses, respectively. The bulk concentrations of 55 elements in each 30 mg sample were analyzed by quadruple-type ICP-MS and sector-type ICP-MS with analytical uncertainties better than 10 percent (1 sigma). B, Pb, Li, Rb, Sr, Sm and Nd were successively separated from the remaining 70 mg of each of the samples, using a novel integrated, multi-ion exchange column chemistry approach, and then the isotopes of these elements were successfully determined by TIMS with analytical errors similar to those for analyses of terrestrial samples. The Sr, Nd, Re and Os isotopic compositions were also analyzed using the remaining aliquots of the sample solutions for trace element analyses by ICP-MS. The results obtained in this study indicate that 1C and 2C samples are probably ordinary chondrite and the Allende meteorite, respectively. However, extreme W, Ta and Nb enrichments in the 1C were probably caused by contamination during sample preparation. Furthermore, both of the samples were extensively contaminated by B from the borosilicate glass container in which the samples were delivered. Five chondrules were separated from Allende meteorite and then sliced into three pieces using a dicing saw. The center slices were used to petrographically determine the mineral phases, compositionally map these phases by SEM-EDX, and obtain quantitative major and trace element compositions (30 elements) by SEM-EDX and ion microprobe. The two outer slices, for which sample masses were less than 1 mg, were chemically treated to obtain the bulk trace elements and isotope compositions of the chondrules. For the chondrule slices, 24 trace elements and Sr and Nd isotopic compositions were determined with extremely small analytical uncertainties by ICP-MS and TIMS (for Sr and Nd, respectively). Based on the analytical experience, including this competition, we believe that all of the analyses carried out could have been completed within 50 days if we could have concentrated on this project alone during that 50-day period. In this report, we describe the analytical techniques employed for the powdered samples and the chondrules, and we present all of the results obtained during the approximately 3-month period of the analytical competition., 資料番号: SA0200006000

Published
2003

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