Presentation Information
[PPS04-P17]Effects of temperature on hydrothermal alteration of amorphous forsterite with liquid warter
*So Takai1, Hanoka Goto1, Tomoaki Watanabe1, Tomoko Fukazawa1 (1.Meiji University)
Keywords:
Amorphous forsterite,Water,Hydrothermal alteration
The presence of fluids containing liquid water and hydrated minerals has been found in the returned samples collected from the asteroid Ryugu [1]. This finding suggests that the minerals in the asteroid experienced a history of a hydrothermal alteration. Since forsterite (Mg2SiO4) in amorphous state is an abundant mineral in the solar system [2], it is essential to investigate the mechanisms of hydrothermal alteration of amorphous forsterite in order to understand mineral evolution in planetesimals.
Igami et al. [3] showed that the magnesium silicate hydrate (MSH) is formed from a hydration reaction of amorphous forsterite in liquid water at room temperature (RT). Kobayashi and Ikeda-Fukazawa [4] analyzed the processes of dissolution of amorphous forsterite in liquid water and the consequent structural changes of the residues from the MD calculations and showed that the Mg(OH)2 and Si(OHx)4 fragments can be a possible origin of MSH. The results suggest that the serpentinization and formation of MSH occurs by reaction with liquid water, while reactions with water vapor causes only the formation of MSH.
Previous studies suggest that the thermal condition of water is important to understand the mechanism of hydrothermal reaction of amorphous forsterite. To investigate the effects of temperature on the phase transition of amorphous forsterite in contact with liquid water, we analyzed the structural changes in amorphous forsterite during hydrothermal reactions. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) observations were employed for the analysis.
The nanoparticles of amorphous forsterite were synthesized using an induction-heated plasma method with Mg(OH)2 and SiO2 [5]. The synthesized nanoparticles and distilled water were put in a titanium cell, and a hydrothermal reaction was conducted within an autoclave. The samples were heated from RT to the reaction temperature (333-523 K) at 1.67 K min-1 and held for 0-96 hours. XRD and SEM measurements were performed after cooling the samples to RT and drying them in a vacuum desiccator at RT for two days. XRD measurements were conducted at RT.
From the XRD patterns, it was confirmed that several broad peaks, which are assigned to MSH [3], appeared after the hydrothermal reaction at £ 373 K. Furthermore, the peaks of brucite appeared after the hydrothermal reaction at 3 373 K and 48 h . The formation of MSH and brucite were confirmed from the SEM observations. The string-like structures of MSH and the hexagonal plate-like fragments were observed in the SEM images. The plate-like fragments were observed at 3 373 K and crystallinity increases as the reaction temperature and reaction time increases. The result indicates that brucite forms even at low temperatures, if magnesium dissolved in to the water phase [6]. For the cases of the reaction temperature of 3 523 K, MSH peaks shift toward the position of the serpentine peak with time and gradually disappeared. The results suggest that the dissolved magnesium is the origin of brucite, whereas MSH, which forms at the interface between amorphous forsterite and water phase, is the origin of serpentine.
We discuss the effects of temperature on the metamorphic process of amorphous forsterite with liquid water.
[1] T. Nakamura et al., Science 379, 8671 (2023).
[2] T. Henning, Annu. Rev. Astron. Astrophys. 48, 21-46 (2010).
[3] Y. Igami, A. Tsuchiyama, T. Yamazaki, M. Matsumoto, Y. Kimura, Geochimica et Cosmochimica Acta 293, 86-102 (2021).
[4] Y. Kobayashi, T. Ikeda-Fukazawa, ACS Earth. Space. Chem. 9, 1134-1141 (2025).
[5] D. Yamamoto, S. Tachibana, ACS Earth Space Chem. 2, 778-786 (2018).
[6] A. Kubo, J. Nishizawa, T. Ikeda-Fukazawa, Chem. Phys. Lett. 805, 139932 (2022).
Igami et al. [3] showed that the magnesium silicate hydrate (MSH) is formed from a hydration reaction of amorphous forsterite in liquid water at room temperature (RT). Kobayashi and Ikeda-Fukazawa [4] analyzed the processes of dissolution of amorphous forsterite in liquid water and the consequent structural changes of the residues from the MD calculations and showed that the Mg(OH)2 and Si(OHx)4 fragments can be a possible origin of MSH. The results suggest that the serpentinization and formation of MSH occurs by reaction with liquid water, while reactions with water vapor causes only the formation of MSH.
Previous studies suggest that the thermal condition of water is important to understand the mechanism of hydrothermal reaction of amorphous forsterite. To investigate the effects of temperature on the phase transition of amorphous forsterite in contact with liquid water, we analyzed the structural changes in amorphous forsterite during hydrothermal reactions. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) observations were employed for the analysis.
The nanoparticles of amorphous forsterite were synthesized using an induction-heated plasma method with Mg(OH)2 and SiO2 [5]. The synthesized nanoparticles and distilled water were put in a titanium cell, and a hydrothermal reaction was conducted within an autoclave. The samples were heated from RT to the reaction temperature (333-523 K) at 1.67 K min-1 and held for 0-96 hours. XRD and SEM measurements were performed after cooling the samples to RT and drying them in a vacuum desiccator at RT for two days. XRD measurements were conducted at RT.
From the XRD patterns, it was confirmed that several broad peaks, which are assigned to MSH [3], appeared after the hydrothermal reaction at £ 373 K. Furthermore, the peaks of brucite appeared after the hydrothermal reaction at 3 373 K and 48 h . The formation of MSH and brucite were confirmed from the SEM observations. The string-like structures of MSH and the hexagonal plate-like fragments were observed in the SEM images. The plate-like fragments were observed at 3 373 K and crystallinity increases as the reaction temperature and reaction time increases. The result indicates that brucite forms even at low temperatures, if magnesium dissolved in to the water phase [6]. For the cases of the reaction temperature of 3 523 K, MSH peaks shift toward the position of the serpentine peak with time and gradually disappeared. The results suggest that the dissolved magnesium is the origin of brucite, whereas MSH, which forms at the interface between amorphous forsterite and water phase, is the origin of serpentine.
We discuss the effects of temperature on the metamorphic process of amorphous forsterite with liquid water.
[1] T. Nakamura et al., Science 379, 8671 (2023).
[2] T. Henning, Annu. Rev. Astron. Astrophys. 48, 21-46 (2010).
[3] Y. Igami, A. Tsuchiyama, T. Yamazaki, M. Matsumoto, Y. Kimura, Geochimica et Cosmochimica Acta 293, 86-102 (2021).
[4] Y. Kobayashi, T. Ikeda-Fukazawa, ACS Earth. Space. Chem. 9, 1134-1141 (2025).
[5] D. Yamamoto, S. Tachibana, ACS Earth Space Chem. 2, 778-786 (2018).
[6] A. Kubo, J. Nishizawa, T. Ikeda-Fukazawa, Chem. Phys. Lett. 805, 139932 (2022).