Genesis and development processes of fractures in granite: Petrographic indicators of hydrothermal alteration.

Genesis and development processes of fractures in granite: Petrographic indicators of hydrothermal alteration.

Biotites occur with varying degrees of alteration within a granite. This study analyzes the relationships among alteration indicators, areal microvoid fractions in chloritized biotite, and macroscopic fracture frequencies in the Toki granite, central Japan, to establish the genesis and development p...

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Autores principales: Takashi Yuguchi, Yuya Izumino, Eiji Sasao
Formato: article
Lenguaje:EN
Publicado: Public Library of Science (PLoS) 2021
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Acceso en línea:https://doaj.org/article/ba058596542c4e51b49b31ef4f2425bb
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spelling oai:doaj.org-article:ba058596542c4e51b49b31ef4f2425bb2021-11-25T06:19:20ZGenesis and development processes of fractures in granite: Petrographic indicators of hydrothermal alteration.1932-620310.1371/journal.pone.0251198https://doaj.org/article/ba058596542c4e51b49b31ef4f2425bb2021-01-01T00:00:00Zhttps://doi.org/10.1371/journal.pone.0251198https://doaj.org/toc/1932-6203Biotites occur with varying degrees of alteration within a granite. This study analyzes the relationships among alteration indicators, areal microvoid fractions in chloritized biotite, and macroscopic fracture frequencies in the Toki granite, central Japan, to establish the genesis and development processes of fractures in granite. Appropriate characterizations for the frequency distribution of macroscopic fractures in granite can assist in understanding potential hydrogeological applications, which contributes to safety evaluations for geological disposal and storage. Borehole 06MI03, drilled to a depth of 191 m, was used to obtain samples for the analysis. In total, 24 samples that depicted variations in the macroscopic fracture frequency were selected. Petrographic alteration indicators using biotite chloritization as innovative methods are proposed to evaluate the extent of hydrothermal alteration and fracture frequency within granites. The alteration indicators are defined as the ratio between the alteration product area and the original mineral area. Furthermore, the volume of microscopic fractures and micropores in the mineral was quantitatively characterized by the areal fraction of microvoids in minerals through image analysis. Samples with high macroscopic fracture frequencies correspond to a high number of areal microvoid fractions and large alteration indicators. Microvoids, which are the source of macroscopic fractures, occurred at temperatures between 350 and 780°C and can be evaluated by intrinsic factors, such as alteration indicators. Subsequent faulting and unloading (extrinsic factors) developed microvoids into macroscopic fractures. Intrinsic factors are used to evaluate the source of macroscopic fractures, and therefore contribute to the characterization of present and future distributions of macroscopic fracture frequencies.Takashi YuguchiYuya IzuminoEiji SasaoPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 16, Iss 5, p e0251198 (2021)
institution DOAJ
collection DOAJ
language EN
topic Medicine
R
Science
Q
spellingShingle Medicine
R
Science
Q
Takashi Yuguchi
Yuya Izumino
Eiji Sasao
Genesis and development processes of fractures in granite: Petrographic indicators of hydrothermal alteration.
description Biotites occur with varying degrees of alteration within a granite. This study analyzes the relationships among alteration indicators, areal microvoid fractions in chloritized biotite, and macroscopic fracture frequencies in the Toki granite, central Japan, to establish the genesis and development processes of fractures in granite. Appropriate characterizations for the frequency distribution of macroscopic fractures in granite can assist in understanding potential hydrogeological applications, which contributes to safety evaluations for geological disposal and storage. Borehole 06MI03, drilled to a depth of 191 m, was used to obtain samples for the analysis. In total, 24 samples that depicted variations in the macroscopic fracture frequency were selected. Petrographic alteration indicators using biotite chloritization as innovative methods are proposed to evaluate the extent of hydrothermal alteration and fracture frequency within granites. The alteration indicators are defined as the ratio between the alteration product area and the original mineral area. Furthermore, the volume of microscopic fractures and micropores in the mineral was quantitatively characterized by the areal fraction of microvoids in minerals through image analysis. Samples with high macroscopic fracture frequencies correspond to a high number of areal microvoid fractions and large alteration indicators. Microvoids, which are the source of macroscopic fractures, occurred at temperatures between 350 and 780°C and can be evaluated by intrinsic factors, such as alteration indicators. Subsequent faulting and unloading (extrinsic factors) developed microvoids into macroscopic fractures. Intrinsic factors are used to evaluate the source of macroscopic fractures, and therefore contribute to the characterization of present and future distributions of macroscopic fracture frequencies.
format article
author Takashi Yuguchi
Yuya Izumino
Eiji Sasao
author_facet Takashi Yuguchi
Yuya Izumino
Eiji Sasao
author_sort Takashi Yuguchi
title Genesis and development processes of fractures in granite: Petrographic indicators of hydrothermal alteration.
title_short Genesis and development processes of fractures in granite: Petrographic indicators of hydrothermal alteration.
title_full Genesis and development processes of fractures in granite: Petrographic indicators of hydrothermal alteration.
title_fullStr Genesis and development processes of fractures in granite: Petrographic indicators of hydrothermal alteration.
title_full_unstemmed Genesis and development processes of fractures in granite: Petrographic indicators of hydrothermal alteration.
title_sort genesis and development processes of fractures in granite: petrographic indicators of hydrothermal alteration.
publisher Public Library of Science (PLoS)
publishDate 2021
url https://doaj.org/article/ba058596542c4e51b49b31ef4f2425bb
work_keys_str_mv AT takashiyuguchi genesisanddevelopmentprocessesoffracturesingranitepetrographicindicatorsofhydrothermalalteration
AT yuyaizumino genesisanddevelopmentprocessesoffracturesingranitepetrographicindicatorsofhydrothermalalteration
AT eijisasao genesisanddevelopmentprocessesoffracturesingranitepetrographicindicatorsofhydrothermalalteration
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