Rheological inversion in high-grade metamorphic rocks: Evidence from folds, inverse folds, mullions and boudins (Bohemian Massif)

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11310%2F25%3A10498703" target="_blank" >RIV/00216208:11310/25:10498703 - isvavai.cz</a>

Výsledek na webu

<a href="https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=CkfqxaBZyv" target="_blank" >https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=CkfqxaBZyv</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.jsg.2025.105339" target="_blank" >10.1016/j.jsg.2025.105339</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Rheological inversion in high-grade metamorphic rocks: Evidence from folds, inverse folds, mullions and boudins (Bohemian Massif)

Popis výsledku v původním jazyce

We investigated the effects of Variscan deformation on Cadomian metagranitoids and intercalated mafic sheets (amphibolite and mafic gneiss) in the Moldanubian and Moravo-Silesian units of the southeastern Bohemian Massif. Given the contrasting mechanical strength of felsic and mafic minerals, deformation is expected to be accommodated by folding and/or boudinage of the competent mafic sheets within the incompetent granitoid host. However, the studied examples show a competence inversion indicated by (1) a stronger foliation in the mafic sheets, (2) extension-parallel mullions at shortened contacts and inverse folds at extended contacts with the cusps pointing into the felsic rock, and (3) extension-parallel folding and boudinage of felsic veins within amphibolite matrix. The lobate phase boundaries in mafic and felsic rocks suggest that the competence inversion was related to a switch in the dominant deformation mechanism from dislocation to phase-boundary diffusion creep in the stability field of high-quartz (T &gt; 650 °C). As phase-boundary diffusion is enhanced by a decreasing grain size, the fine-grained mafic rocks behaved mechanically weaker than the coarser grained felsic rocks. This inversion in viscosity occurred at ca. 332 Ma (U-Pb on titanite) and might have been also supported by the basal slip of biotite within the mafic sheets.

Název v anglickém jazyce

Rheological inversion in high-grade metamorphic rocks: Evidence from folds, inverse folds, mullions and boudins (Bohemian Massif)

Popis výsledku anglicky

We investigated the effects of Variscan deformation on Cadomian metagranitoids and intercalated mafic sheets (amphibolite and mafic gneiss) in the Moldanubian and Moravo-Silesian units of the southeastern Bohemian Massif. Given the contrasting mechanical strength of felsic and mafic minerals, deformation is expected to be accommodated by folding and/or boudinage of the competent mafic sheets within the incompetent granitoid host. However, the studied examples show a competence inversion indicated by (1) a stronger foliation in the mafic sheets, (2) extension-parallel mullions at shortened contacts and inverse folds at extended contacts with the cusps pointing into the felsic rock, and (3) extension-parallel folding and boudinage of felsic veins within amphibolite matrix. The lobate phase boundaries in mafic and felsic rocks suggest that the competence inversion was related to a switch in the dominant deformation mechanism from dislocation to phase-boundary diffusion creep in the stability field of high-quartz (T &gt; 650 °C). As phase-boundary diffusion is enhanced by a decreasing grain size, the fine-grained mafic rocks behaved mechanically weaker than the coarser grained felsic rocks. This inversion in viscosity occurred at ca. 332 Ma (U-Pb on titanite) and might have been also supported by the basal slip of biotite within the mafic sheets.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10505 - Geology

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2025

Kód důvěrnosti údajů

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

Název periodika

Journal of Structural Geology

ISSN

0191-8141

e-ISSN

1873-1201

Svazek periodika

191

Číslo periodika v rámci svazku

February

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

17

Strana od-do

105339

Kód UT WoS článku

001411019700001

EID výsledku v databázi Scopus

2-s2.0-85214346602