TY - JOUR
KW - AMS fabric
KW - Folding
KW - Mechanical anisotropy
KW - Melt-enhanced deformation
KW - Orogenic sill
KW - Transposition
AU - Prokop Závada
AU - Thibaud Calassou
AU - Karel Schulmann
AU - František Hrouda
AU - Pavla Štípská
AU - Pavlína Hasalová
AU - Jitka Míková
AU - Tomáš Magna
AU - Petr Mixa
AB - New approach involving evaluation of anisotropy of magnetic susceptibility (AMS) data in stereoplots and Jelínek’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.
BT - Journal of Structural Geology
DO - http://dx.doi.org/10.1016/j.jsg.2016.11.007
N2 - New approach involving evaluation of anisotropy of magnetic susceptibility (AMS) data in stereoplots and Jelínek’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.
PY - 2017
EP - 166–183
T2 - Journal of Structural Geology
TI - Magnetic fabric transposition in folded granite sills in Variscan orogenic wedge
UR - http://www.sciencedirect.com/science/article/pii/S019181411630195X
VL - 94
ER -