Magnetic fabric and modeled strain distribution in the head of a nested granite diapir, the Melechov pluton, Bohemian Massif

0439554 - GLÚ 2015 RIV GB eng J - Journal Article
Trubač, Jakub - Žák, J. - Chlupáčová, M. - Janoušek, V.
Magnetic fabric and modeled strain distribution in the head of a nested granite diapir, the Melechov pluton, Bohemian Massif.
Journal of Structural Geology. Roč. 66, September (2014), s. 271-283. ISSN 0191-8141. E-ISSN 1873-1201
Institutional support: RVO:67985831
Keywords : anisotropy of magnetic susceptibility (AMS) * diapir * emplecement * fabric * granite * strain
Subject RIV: DE - Earth Magnetism, Geodesy, Geography
Impact factor: 2.884, year: 2014

The Melechov pluton, Bohemian Massif, is interpreted as a mid-crustal nested granitic diapir with an apical part exposed at the present-day erosion level. The diapir head exhibits a concentric structure defined by lithologic zoning and by the anisotropy of magnetic susceptibility (AMS). In concert with theoretical models, outward-dipping margin-parallel magnetic foliations are associated with oblate shapes of the susceptibility ellipsoids and higher degree of anisotropy, passing inward into weaker triaxial to prolate fabric. By contrast, magnetic fabric in an inner granite unit is in places oriented at a high angle to internal contacts and is interpreted as recording an internal diapir circulation. We use inverse modeling to calculate strain variations across the diapir from the AMS data. The magnetic fabric parameters and calculated strains are in agreement with strain distribution in heads of model Newtonian diapirs traveling a distance of two body radii and suggest granitic magma ascent as a crystal-poor suspension followed by crystallization of fabric markers and their response to strain near the final emplacement level. The intrusive fabric thus formed late but, though generally weak, was still capable of recording incremental strain gradient in the granite diapir.
Permanent Link: http://hdl.handle.net/11104/0242819