Nanograin formation and reaction-induced fracturing due to decarbonation: Implications for the microstructures of fault mirrors
Principal slip zones often contain highly reflective surfaces referred to as fault mirrors, shown to consist of a nanogranular coating. There is currently no consensus on how the nanograins form, or why they survive weathering on a geological time-scale. To simplify the complex system of a natural f...
Published in: | Earth and Planetary Science Letters |
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Online Access: | http://hdl.handle.net/10852/57824 http://urn.nb.no/URN:NBN:no-60522 https://doi.org/10.1016/j.epsl.2017.08.001 |
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ftoslouniv:oai:www.duo.uio.no:10852/57824 2023-05-15T16:52:10+02:00 Nanograin formation and reaction-induced fracturing due to decarbonation: Implications for the microstructures of fault mirrors Pluymakers, Anne Marie Henriette Røyne, Anja 2017-09-04T08:53:18Z http://hdl.handle.net/10852/57824 http://urn.nb.no/URN:NBN:no-60522 https://doi.org/10.1016/j.epsl.2017.08.001 EN eng Elsevier Science http://urn.nb.no/URN:NBN:no-60522 Pluymakers, Anne Marie Henriette Røyne, Anja . Nanograin formation and reaction-induced fracturing due to decarbonation: Implications for the microstructures of fault mirrors. Earth and Planetary Science Letters. 2017, 476, 59-68 http://hdl.handle.net/10852/57824 1490620 info:ofi/fmt:kev:mtx:ctx&ctx_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.jtitle=Earth and Planetary Science Letters&rft.volume=476&rft.spage=59&rft.date=2017 Earth and Planetary Science Letters 476 59 68 http://dx.doi.org/10.1016/j.epsl.2017.08.001 URN:NBN:no-60522 Fulltext https://www.duo.uio.no/bitstream/handle/10852/57824/1/Fault%2Bmirror%2Bpaper%2Bpostprint%2Bversion.pdf Attribution-NonCommercial-NoDerivs 3.0 Unported https://creativecommons.org/licenses/by-nc-nd/3.0/ CC-BY-NC-ND 0012-821X Journal article Tidsskriftartikkel Peer reviewed AcceptedVersion 2017 ftoslouniv https://doi.org/10.1016/j.epsl.2017.08.001 2020-06-21T08:51:01Z Principal slip zones often contain highly reflective surfaces referred to as fault mirrors, shown to consist of a nanogranular coating. There is currently no consensus on how the nanograins form, or why they survive weathering on a geological time-scale. To simplify the complex system of a natural fault zone, where slip and heat generation are inherently coupled, we investigated the effect of elevated temperatures on carbonate rock surfaces, as well as their resistance to water exposure. This allows us to isolate the role of the decarbonation process in the formation of nanograins. We used cleaved crystals of Iceland spar calcite, manually polished dolomite protolith, as well as natural dolomite fault mirror surfaces. The samples were heated to 200–800 °C in a ∼5 h heating cycle, followed by slow cooling (∼12 h) to room temperature. Subsequently, we imaged the samples using scanning electron microscopy and atomic force microscopy. Nanograin formation on all sample surfaces was pervasive at and above 600 °C. The Foiana fault mirror samples were initially coated with aligned naturally-formed nanograins, but display a non-directional nanogranular coating after heating. The nanograins that were formed by heating rapidly recrystallized to bladed hydroxides upon exposure to deionized water, whereas the nanograins on unheated fault mirror samples remained unchanged in water. This shows that the nanograins formed by heating alone are different from those formed in fault zones, and calls for a better characterization of nanograins and their formation mechanisms. Furthermore, we find a characteristic star-shaped crack pattern associated with reacted regions of the carbonate surfaces. The existence of this pattern implies that the mechanical stresses set up by the decarbonation reaction can be sufficiently large to drive fracturing in these systems. We propose that this mechanism may contribute to grain size reduction in fault zones. Article in Journal/Newspaper Iceland Universitet i Oslo: Digitale utgivelser ved UiO (DUO) Earth and Planetary Science Letters 476 59 68 |
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Open Polar |
collection |
Universitet i Oslo: Digitale utgivelser ved UiO (DUO) |
op_collection_id |
ftoslouniv |
language |
English |
description |
Principal slip zones often contain highly reflective surfaces referred to as fault mirrors, shown to consist of a nanogranular coating. There is currently no consensus on how the nanograins form, or why they survive weathering on a geological time-scale. To simplify the complex system of a natural fault zone, where slip and heat generation are inherently coupled, we investigated the effect of elevated temperatures on carbonate rock surfaces, as well as their resistance to water exposure. This allows us to isolate the role of the decarbonation process in the formation of nanograins. We used cleaved crystals of Iceland spar calcite, manually polished dolomite protolith, as well as natural dolomite fault mirror surfaces. The samples were heated to 200–800 °C in a ∼5 h heating cycle, followed by slow cooling (∼12 h) to room temperature. Subsequently, we imaged the samples using scanning electron microscopy and atomic force microscopy. Nanograin formation on all sample surfaces was pervasive at and above 600 °C. The Foiana fault mirror samples were initially coated with aligned naturally-formed nanograins, but display a non-directional nanogranular coating after heating. The nanograins that were formed by heating rapidly recrystallized to bladed hydroxides upon exposure to deionized water, whereas the nanograins on unheated fault mirror samples remained unchanged in water. This shows that the nanograins formed by heating alone are different from those formed in fault zones, and calls for a better characterization of nanograins and their formation mechanisms. Furthermore, we find a characteristic star-shaped crack pattern associated with reacted regions of the carbonate surfaces. The existence of this pattern implies that the mechanical stresses set up by the decarbonation reaction can be sufficiently large to drive fracturing in these systems. We propose that this mechanism may contribute to grain size reduction in fault zones. |
format |
Article in Journal/Newspaper |
author |
Pluymakers, Anne Marie Henriette Røyne, Anja |
spellingShingle |
Pluymakers, Anne Marie Henriette Røyne, Anja Nanograin formation and reaction-induced fracturing due to decarbonation: Implications for the microstructures of fault mirrors |
author_facet |
Pluymakers, Anne Marie Henriette Røyne, Anja |
author_sort |
Pluymakers, Anne Marie Henriette |
title |
Nanograin formation and reaction-induced fracturing due to decarbonation: Implications for the microstructures of fault mirrors |
title_short |
Nanograin formation and reaction-induced fracturing due to decarbonation: Implications for the microstructures of fault mirrors |
title_full |
Nanograin formation and reaction-induced fracturing due to decarbonation: Implications for the microstructures of fault mirrors |
title_fullStr |
Nanograin formation and reaction-induced fracturing due to decarbonation: Implications for the microstructures of fault mirrors |
title_full_unstemmed |
Nanograin formation and reaction-induced fracturing due to decarbonation: Implications for the microstructures of fault mirrors |
title_sort |
nanograin formation and reaction-induced fracturing due to decarbonation: implications for the microstructures of fault mirrors |
publisher |
Elsevier Science |
publishDate |
2017 |
url |
http://hdl.handle.net/10852/57824 http://urn.nb.no/URN:NBN:no-60522 https://doi.org/10.1016/j.epsl.2017.08.001 |
genre |
Iceland |
genre_facet |
Iceland |
op_source |
0012-821X |
op_relation |
http://urn.nb.no/URN:NBN:no-60522 Pluymakers, Anne Marie Henriette Røyne, Anja . Nanograin formation and reaction-induced fracturing due to decarbonation: Implications for the microstructures of fault mirrors. Earth and Planetary Science Letters. 2017, 476, 59-68 http://hdl.handle.net/10852/57824 1490620 info:ofi/fmt:kev:mtx:ctx&ctx_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.jtitle=Earth and Planetary Science Letters&rft.volume=476&rft.spage=59&rft.date=2017 Earth and Planetary Science Letters 476 59 68 http://dx.doi.org/10.1016/j.epsl.2017.08.001 URN:NBN:no-60522 Fulltext https://www.duo.uio.no/bitstream/handle/10852/57824/1/Fault%2Bmirror%2Bpaper%2Bpostprint%2Bversion.pdf |
op_rights |
Attribution-NonCommercial-NoDerivs 3.0 Unported https://creativecommons.org/licenses/by-nc-nd/3.0/ |
op_rightsnorm |
CC-BY-NC-ND |
op_doi |
https://doi.org/10.1016/j.epsl.2017.08.001 |
container_title |
Earth and Planetary Science Letters |
container_volume |
476 |
container_start_page |
59 |
op_container_end_page |
68 |
_version_ |
1766042328513904640 |