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

Result code in 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>

Result on the web

<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>

Result language

angličtina

Original language name

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

Original language description

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.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

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OECD FORD branch

10505 - Geology

Project

—

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2025

Confidentiality

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

Name of the periodical

Journal of Structural Geology

ISSN

0191-8141

e-ISSN

1873-1201

Volume of the periodical

191

Issue of the periodical within the volume

February

Country of publishing house

GB - UNITED KINGDOM

Number of pages

17

Pages from-to

105339

UT code for WoS article

001411019700001

EID of the result in the Scopus database

2-s2.0-85214346602