Magnetic fabric transposition in folded granite sills in Variscan orogenic wedge

0473606 - GFÚ 2018 RIV GB eng J - Journal Article
Závada, Prokop - Calassou, T. - Schulmann, K. - Hrouda, F. - Štípská, P. - Hasalová, Pavlína - Míková, J. - Magna, T. - Mixa, P.
Magnetic fabric transposition in folded granite sills in Variscan orogenic wedge.
Journal of Structural Geology. Roč. 94, January (2017), s. 166-183. ISSN 0191-8141. E-ISSN 1873-1201
R&D Projects: GA ČR GA14-15632S
Institutional support: RVO:67985530
Keywords : orogenic sill * AMS fabric * folding
OECD category: Geology
Impact factor: 2.622, year: 2017

New approach involving evaluation of anisotropy of magnetic susceptibility (AMS) data in stereoplots and Jelinek's Pj-T space, Vollmer's eigenvalue and microstructural analyses is proposed to discriminate between homogeneous and superposed deformation in granites. This method is used to decipher the internal AMS fabric and microstructural evolution of a folded array of granitic sills. The studied major sill shows a fabric and microstructural zonality marked by submagmatic and high-temperature Type I planar-linear fabric developed at sill margins, and the transpositional Type II subsolidus fabrics that formed at high to medium temperature deformation in the sill core. While Type I fabric is associated with dip slip magnetic lineations, Type II subsolidus fabrics are marked by subhorizontal magnetic lineations striking parallel to the long axis of the sill. The structural reconstruction of the fabrics in the granite and the host rocks as well as new U-Pb zircon ages suggest coeval emplacement of horizontal and vertical sills accounting for significant weakening of the host rock magma multilayer. The model of folding of such multilayer and extrusion of residual magma parallel to axial planes is discussed with respect to structural record in other syn-contractional granite sill arrays forming sheeted plutons worldwide.
Permanent Link: http://hdl.handle.net/11104/0270742