Magnetization of Isotropic Substance M1 = k H1 M2 = k H2 M3 = k H3 Magnetization of Anisotropic, Linearly Magnetic Substance M1 = k11 H1 + k12 H2 + k13 H3 M2 = k21 H1 + k22 H2 + k23 H3 M3 = k31 H1 + k32 H2 + k33 H3 In Matrix Notation M1 = k11 k12 k13 H1 M2 = k21 k22 k23 H2 M3 = k31 k32 k33 H3 Magnetization Vector, Susceptibility Tensor, Field Intensity Vector ANISOTROPY OF MAGNETIC SUSCEPTIBILITY M1 = k11 H1 + k12 H2 + k13 H3 M2 = k21 H1 + k22 H2 + k23 H3 M3 = k31 H1 + k32 H2 + k33 H3 For each tensor such a coordinate system exists where M1 = k11 H1 M2 = k22 H2 M3 = k33 H3 Axes of this system are parallel to the susceptibility ellipsoid axes, in which magnetization is parallel to the field. Susceptibilities along ellipsoid axes are Principal Susceptibilities Directions of ellipsoid axes are Principal Directions Principal Susceptibilities, Principal Directions AMS Parameters and Plots Flinn Type Plot Jelinek Type Plot P = k1/k3 degree of AMS k1>k2>k3 L = k1/k2 magnetic lineation F = k2/k3 magnetic foliation n1= lnk1, n2= lnk2, T = (2n2-n1-n3)/(n1-n3) shape parameter n3 = lnk3 equal-area projection on lower hemisphere ORIENTATIONS OF MAGNETIC FABRIC ELEMENTS Hematite k1 = k2 >> k3 P > 100 Pyrrhotite k1 = k2 >> k3 P > 300 Grain AMS is due to the crystal lattice (magnetocrystalline AMS) AMS of Minerals 1 Biotite k1 = k2 > k3 P = 1.2-1.6 Muscovite k1 = k2 > k3 P = 1.3-1.4 Chlorite k1 = k2 > k3 P = 1.2-1.8 Grain AMS is due to the crystal lattice (magnetocrystalline AMS) AMS of Minerals 2 Magnetite is internally isotropic in weak field. P = (1+κNc)/(1+κNa) κ – intrinsic susceptibility N – demagnetizing factor P = 1.1 – 3.0 (controlled by grain shape) Grain AMS is due to the grain shape (shape AMS) AMS of Minerals 4 Rock degree of AMS, Grain degree of AMS, Concentration Parameter Effects of Grain AMS and Preferred Orientation: a model AMS OF SEDIMENTARY ROCKS Flume Depositions Experiments 13,15 density current, flat bed N/A density current, flat bed AMS in Turbidites Flysch Belt of West Carpathians – geol. scheme Flysch Belt of West Carpathians - orientations current direction MF pole ML bedding corrected for tilt ML parallel to current direction ML perpendicular to current direction Magnetic vs. Sedimentary Lineations Ždánice Formation Magura Flysch relatively good correlation in both cases Palaeography of Ždánice – Hustopeče Formation Supply flow Transport along basin Geol map of Slovakia Zázrivá Depression Skorušinské vrchy Hill Liptov Depression P, T and f Parameters Liptovská kotlina - Pa Skorušinské vrchy - Pa Zázrivská deprese - Pa VOLCANICS AND DIKES Degree of AMS is extremely low, typically P<1.05, indicating very weak preferred orientation not detectable clasically Magnetic foliations and lineations are related to lava flow directions LAVA FLOWS (Chřibský les L.F.) Quartenary in age, flew in ancient valley of the Moravice river, flow direction is therefore very well known Orientations K1 || flow direction random orientation DIKES Focus is on the relationship of the MF and ML to dike shape (after Raposo & Ernesto, PEPI 1995) AMS Types Type I: K3 | dike plane a) K1 horizontal b) K1 vertical free flow Type II: K3, K1 || dike plane a) K1 horizontal b) K1 vertical Type III: K3||, K1 | dike plane static compaction Type IV: random orientation in K1, K3 partially solidified lava SILL vs. RING DIKE Bastian a Ronnbeck Islands create an elliptic formation Two hypotheses for its origin: 1. islands are remanants of an irregularly sunken sill 2. islands are remnants of a Ring Dike (after Halvorsen, EPSL, 1974) Expectations: horizontal MF in case 1 steep MF in case 2 Method: AMS of the islands plus AMS of a doubtless sill Geol. Scheme Sill Islands Lomfjorden Sill Bastian and Ronnbeck islands Principal Directions Bastian and Ronnbeck Islands are remnants of an irregularly sunken sill rather than remnants of a ring dike. DIKES ABOVE MANTLE PLUMES sampling at several distances from swarm center, at 400,500,600, 800, 1000, 2000 km. McKenzie Radiating Dike Swarm Magnetic Foliations and Lineations Vertical flow at distances <= 600 km. Horizontal flow at distances > 600 km Complex AMS patterns at very large distances. Conclusions: Assuming that lava flows vertically above the mantle plume, then mantle plume under the MacKenzie dike swarm is much smaller in diameter than is the plume diameter. The lava flows vertcally above the plume, but in upper levels its flow changes into horizontal. ČISTÁ-JESENICE PLUTON AMS Parameters Tis Granite: MF W body E body Tis Granite: ML W body E body Čistá stock: AMS Orientation AMS AND CLEAVAGE Nízký Jeseník - geol. scheme Bedding only Spaced Cleavage Slaty Cleavage Metamorphic Schistosity AMS IN FOLDS Fold de-folding Buckle Fold NJ 12 Fold NJ 153-pd Cleavage Fold NJ 23