Granitic magma emplacement and deformation during early-orogenic syn-convergent transtension: The Stare Sedlo complex, Bohemian Massif

0448156 - GLÚ 2016 RIV GB eng J - Článek v odborném periodiku
Tomek, Filip - Žák, J. - Chadima, Martin
Granitic magma emplacement and deformation during early-orogenic syn-convergent transtension: The Stare Sedlo complex, Bohemian Massif.
Journal of Geodynamics. Roč. 87, JUL (2015), s. 50-66. ISSN 0264-3707
Institucionální podpora: RVO:67985831
Klíčová slova: anisotropy of magnetic susceptibility (AMS) * Bohemian Massif * pluton emplacement * granite * transtension * Variscan orogeny
Kód oboru RIV: DB - Geologie a mineralogie
Impakt faktor: 1.926, rok: 2015

The Late Devonian Staré Sedlo complex, Bohemian Massif, was emplaced as a subhorizontal sheeted sill pluton into a transtension zone. The transtensional setting is documented by strong constrictional fabric, corroborated by the anisotropy of magnetic susceptibility (AMS), with variably developed subhorizontal magmatic to solid-state foliation suggesting vertical shortening. Intrusive contacts of the granitoids with metapelitic screens and tapered sill tips indicate that magma wedging was the dominant process of sill propagation. The sills exhibit two intrusive styles, ranging from thin lit-par-lit injections to widely spaced meter-thick sills. These two styles are interpreted as reflecting variable viscosities of intruding magma where low-viscosity magma percolated along foliation planes whereas high-viscosity magma produced more localized thicker sills. We propose that the magma/host rock system in transtension must have evolved from initial crack tip propagation and vertical expansion due to new magma additions through conduit flow to ductile thinning after the magma input had ceased. The sill emplacement and their subsequent deformation are then interpreted as recording syn-convergent early-orogenic sinistral transtension along the rear side of an upper-crustal wedge, which was extruded both upward and laterally in response to subduction and continental underthrusting.
Trvalý link: http://hdl.handle.net/11104/0249878