Porosity evolution at the brittle-ductile transition in the continental crust: Implications for deep hydro-geothermal circulation

Abstract Recently, projects have been proposed to engineer deep geothermal reservoirs in the ductile crust. To examine their feasibility, we performed high-temperature (up to 1000 °C), high-pressure (130 MPa) triaxial experiments on granite (initially-intact and shock-cooled samples) in which we mea...

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Autores principales:	M. Violay, M. J. Heap, M. Acosta, C. Madonna
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2017
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/3fc81aea733c4b2daa1b72140e721f0a
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spelling	oai:doaj.org-article:3fc81aea733c4b2daa1b72140e721f0a2021-12-02T11:53:13ZPorosity evolution at the brittle-ductile transition in the continental crust: Implications for deep hydro-geothermal circulation10.1038/s41598-017-08108-52045-2322https://doaj.org/article/3fc81aea733c4b2daa1b72140e721f0a2017-08-01T00:00:00Zhttps://doi.org/10.1038/s41598-017-08108-5https://doaj.org/toc/2045-2322Abstract Recently, projects have been proposed to engineer deep geothermal reservoirs in the ductile crust. To examine their feasibility, we performed high-temperature (up to 1000 °C), high-pressure (130 MPa) triaxial experiments on granite (initially-intact and shock-cooled samples) in which we measured the evolution of porosity during deformation. Mechanical data and post-mortem microstuctural characterisation (X-ray computed tomography and scanning electron microscopy) indicate that (1) the failure mode was brittle up to 900 °C (shear fracture formation) but ductile at 1000 °C (no strain localisation); (2) only deformation up to 800 °C was dilatant; (3) deformation at 900 °C was brittle but associated with net compaction due to an increase in the efficiency of crystal plastic processes; (4) ductile deformation at 1000 °C was compactant; (5) thermally-shocking the granite did not influence strength or failure mode. Our data show that, while brittle behaviour increases porosity, porosity loss is associated with both ductile behaviour and transitional behaviour as the failure mode evolves from brittle to ductile. Extrapolating our data to geological strain rates suggests that the brittle-ductile transition occurs at a temperature of 400 ± 100 °C, and is associated with the limit of fluid circulation in the deep continental crust.M. ViolayM. J. HeapM. AcostaC. MadonnaNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 7, Iss 1, Pp 1-10 (2017)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q M. Violay M. J. Heap M. Acosta C. Madonna Porosity evolution at the brittle-ductile transition in the continental crust: Implications for deep hydro-geothermal circulation
description	Abstract Recently, projects have been proposed to engineer deep geothermal reservoirs in the ductile crust. To examine their feasibility, we performed high-temperature (up to 1000 °C), high-pressure (130 MPa) triaxial experiments on granite (initially-intact and shock-cooled samples) in which we measured the evolution of porosity during deformation. Mechanical data and post-mortem microstuctural characterisation (X-ray computed tomography and scanning electron microscopy) indicate that (1) the failure mode was brittle up to 900 °C (shear fracture formation) but ductile at 1000 °C (no strain localisation); (2) only deformation up to 800 °C was dilatant; (3) deformation at 900 °C was brittle but associated with net compaction due to an increase in the efficiency of crystal plastic processes; (4) ductile deformation at 1000 °C was compactant; (5) thermally-shocking the granite did not influence strength or failure mode. Our data show that, while brittle behaviour increases porosity, porosity loss is associated with both ductile behaviour and transitional behaviour as the failure mode evolves from brittle to ductile. Extrapolating our data to geological strain rates suggests that the brittle-ductile transition occurs at a temperature of 400 ± 100 °C, and is associated with the limit of fluid circulation in the deep continental crust.
format	article
author	M. Violay M. J. Heap M. Acosta C. Madonna
author_facet	M. Violay M. J. Heap M. Acosta C. Madonna
author_sort	M. Violay
title	Porosity evolution at the brittle-ductile transition in the continental crust: Implications for deep hydro-geothermal circulation
title_short	Porosity evolution at the brittle-ductile transition in the continental crust: Implications for deep hydro-geothermal circulation
title_full	Porosity evolution at the brittle-ductile transition in the continental crust: Implications for deep hydro-geothermal circulation
title_fullStr	Porosity evolution at the brittle-ductile transition in the continental crust: Implications for deep hydro-geothermal circulation
title_full_unstemmed	Porosity evolution at the brittle-ductile transition in the continental crust: Implications for deep hydro-geothermal circulation
title_sort	porosity evolution at the brittle-ductile transition in the continental crust: implications for deep hydro-geothermal circulation
publisher	Nature Portfolio
publishDate	2017
url	https://doaj.org/article/3fc81aea733c4b2daa1b72140e721f0a
work_keys_str_mv	AT mviolay porosityevolutionatthebrittleductiletransitioninthecontinentalcrustimplicationsfordeephydrogeothermalcirculation AT mjheap porosityevolutionatthebrittleductiletransitioninthecontinentalcrustimplicationsfordeephydrogeothermalcirculation AT macosta porosityevolutionatthebrittleductiletransitioninthecontinentalcrustimplicationsfordeephydrogeothermalcirculation AT cmadonna porosityevolutionatthebrittleductiletransitioninthecontinentalcrustimplicationsfordeephydrogeothermalcirculation
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Porosity evolution at the brittle-ductile transition in the continental crust: Implications for deep hydro-geothermal circulation

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