Computational study of deformation mechanisms and grain size evolution in granulites – Implications for the rheology of the lower crust

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00025798%3A_____%2F17%3A00000072" target="_blank" >RIV/00025798:_____/17:00000072 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/00216208:11310/17:10363693

Výsledek na webu

<a href="http://www.sciencedirect.com/science/article/pii/S0012821X17301401" target="_blank" >http://www.sciencedirect.com/science/article/pii/S0012821X17301401</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.epsl.2017.03.010" target="_blank" >10.1016/j.epsl.2017.03.010</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Computational study of deformation mechanisms and grain size evolution in granulites – Implications for the rheology of the lower crust

Popis výsledku v původním jazyce

Recrystallization of original coarse-grained ternary feldspar in the Bohemian Massif led to formation of a fine-grained (∼100μm) mixed matrix dominated by plagioclase and K-feldspar. This change occurred at temperatures of ∼850◦C and was probably caused by chemically induced decomposition related to slight cooling and enhanced by deformation during continental collision. The resulting microstructure shows indications of diffusion creep assisted by melt-enhanced grain-boundary sliding. Further on, minor coarsening occurred associated with deformation by dislocation creep and aggregation of mineral phases. Using a thermodynamics-based model of grain size evolution we show that stability of the fine-grained microstructure crucially depends on Zener pinning in the two-phase mineral matrix. Pinning efficiently hinders grain growth, and the small grain size that resulted from the ternary feldspar decomposition can be stable even at high temperatures. The late switch from the grain-size-sensitive creep to dislocation creep is rather difficult to explain by temperature and strain rate (or stress) changes only. However, a simple incorporation of melt solidification can successfully simulate this behavior. Alternatively, the switch and the associated grain size growth can be related to mineral phase aggregation at lower pressure–temperature conditions resulting into a decrease of pinning efficiency. This study suggests that the fine grain size of the Bohemian granulites, in contrast to the common coarse-grained type, stems from abrupt recrystallization during the high-pressure high-temperature conditions, and pinning in the fine-grained matrix. Such a process may in some cases significantly and suddenly reduce the strength of the lower continental crust and allow for its efficient redistribution.

Název v anglickém jazyce

Computational study of deformation mechanisms and grain size evolution in granulites – Implications for the rheology of the lower crust

Popis výsledku anglicky

Recrystallization of original coarse-grained ternary feldspar in the Bohemian Massif led to formation of a fine-grained (∼100μm) mixed matrix dominated by plagioclase and K-feldspar. This change occurred at temperatures of ∼850◦C and was probably caused by chemically induced decomposition related to slight cooling and enhanced by deformation during continental collision. The resulting microstructure shows indications of diffusion creep assisted by melt-enhanced grain-boundary sliding. Further on, minor coarsening occurred associated with deformation by dislocation creep and aggregation of mineral phases. Using a thermodynamics-based model of grain size evolution we show that stability of the fine-grained microstructure crucially depends on Zener pinning in the two-phase mineral matrix. Pinning efficiently hinders grain growth, and the small grain size that resulted from the ternary feldspar decomposition can be stable even at high temperatures. The late switch from the grain-size-sensitive creep to dislocation creep is rather difficult to explain by temperature and strain rate (or stress) changes only. However, a simple incorporation of melt solidification can successfully simulate this behavior. Alternatively, the switch and the associated grain size growth can be related to mineral phase aggregation at lower pressure–temperature conditions resulting into a decrease of pinning efficiency. This study suggests that the fine grain size of the Bohemian granulites, in contrast to the common coarse-grained type, stems from abrupt recrystallization during the high-pressure high-temperature conditions, and pinning in the fine-grained matrix. Such a process may in some cases significantly and suddenly reduce the strength of the lower continental crust and allow for its efficient redistribution.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10505 - Geology

Projekt

Výsledek vznikl pri realizaci vícero projektů. Více informací v záložce Projekty.

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2017

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Earth and Planetary Science Letters

ISSN

0012-821X

e-ISSN

—

Svazek periodika

466

Číslo periodika v rámci svazku

March

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

12

Strana od-do

91–102

Kód UT WoS článku

000400225800010

EID výsledku v databázi Scopus

2-s2.0-85015873962