Preprints
https://doi.org/10.5194/egusphere-2022-1487
https://doi.org/10.5194/egusphere-2022-1487
 
02 Jan 2023
02 Jan 2023
Status: this preprint is open for discussion.

Water release and homogenization by dynamic recrystallization of quartz

Junichi Fukuda1, Takamoto Okudaira1, and Yukiko Ohtomo2 Junichi Fukuda et al.
  • 1Department of Geosciences, Osaka Metropolitan University, Osaka, 558-8585, Japan
  • 2Department of Education, Art and Science, Yamagata University, Yamagata, 990-8560, Japan

Abstract. To evaluate changes in water distribution generated by dynamic recrystallization of quartz, we performed infrared (IR) spectroscopy mapping of quartz in deformed granite from the Wariyama uplift zone in NE Japan. We analyzed three granite samples with different degrees of deformation: almost undeformed, weakly deformed, and strongly deformed. Dynamically recrystallized quartz grains with a grain size of ~10 µm are found in these three samples, but the percentages of recrystallized grains and recrystallization processes are different. Quartz in the almost undeformed sample shows wavy grain boundaries with a few bulged quartz grains. In the weakly deformed sample, bulging of quartz is developed in regions a few hundred micrometers from adjacent host quartz grains. In the strongly deformed sample, almost all quartz grains are recrystallized by subgrain rotation. IR spectra of quartz in the three samples commonly show a broad water band owing to H2O fluid at 2800–3750 cm−1 with no structural OH bands. Water contents in host quartz grains in the almost undeformed sample are in the range of 40–1750 wt. ppm, with a mean of 500 ± 280 wt. ppm H2O. On the other hand, water contents in regions of recrystallized grains, regardless of the recrystallization processes involved, are in the range of 100–510 wt. ppm, with a mean of 220 ± 70 wt. ppm, which are low and homogeneous compared with contents in host quartz grains. Water contents in regions of subgrains are intermediate between those in host and recrystallized grains. These results for water distribution in quartz imply that water is released by dynamic recrystallization.

Junichi Fukuda et al.

Status: open (until 14 Feb 2023)

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Junichi Fukuda et al.

Junichi Fukuda et al.

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Short summary
We measured water distributions in deformed quartz by infrared spectroscopy mapping and used the results to discuss changes in water distribution resulting from textural development. Because of the grain size reduction process (dynamic recrystallization), water contents decrease from 40–1750 wt. ppm in host grains of ~500 µm to 100–510 wt. ppm in recrystallized regions composed of fine grains of ~10 µm. Our results indicate that water is released and homogenized by dynamic recrystallization.