FLOW OF PARTIALLY MOLTEN CRUST RECORDED BY THE ANISOTROPY OF MAGNETIC SUSCEPTIBILITY IN LEUCOGRANITES
All the leucogranites display a low magnetic susceptibility (K) and three main types are distinguished: (1) diamagnetic garnet-bearing leucogranites with K < 10 -6 SI; (2) paramagnetic biotite-muscovite-bearing granites ± magmatic andalusite with K = 10 to 30.10 -6 SI; (3) ferromagnetic pyrrhotite-biotite-bearing granites with K = 30 to 100.10 -6 SI. The degree of anisotropy (P) ranges from 1.02 to 1.10 and increases slightly with K. Most stations comprise one only of the above magnetic types.
The diamagnetic types (10% of stations) have a small within-station AMS fabric consistency due to the low intrinsic anisotropy of quartz and feldspars. The ferromagnetic types (40%) have a large variability due to presence of a ferrimagnetic carrier in trace amounts only. The paramagnetic types (50%) display consistent AMS fabrics, and are concordant with foliations and lineations measured in the field. Therefore, leucogranites in which the magnetic carriers are paramagnetic can be used to characterize regional fabrics in metamorphic core complexes. These data can provide important kinematic information for the deformation of partially molten crust.