Gravity Inversion, Ams and Geochronological Investigations of Syntectonic Granitic Plutons in the Southern Part of the Variscan French Massif Central

Magnetic fabric analyses, gravity inversion associated with chemical U-Th-Pb dating and structural observations are carried out to elucidate relationships between faulting and magmatic processes. This multidisciplinary study has been undertaken on Late Carboniferous plutons, situated in the southern part of the Variscan French Massif Central (FMC). The Glénat, Omps and Boisset plutons crop out on both sides of the crustal-scale Sillon Houiller Fault (SHF). The Anisotropy of Magnetic Susceptibility (AMS) measurements and structural observations show that (i) the plutons acquired their final structure during the magma crystallization and record a NW-SE maximum stretching trend; (ii) in the Boisset pluton, post magmatic fabrics predominate with a NNW-SSE trending lineation. The structural pattern deduced from the AMS study is thus consistent with the NW-SE late orogenic extensional tectonic regime that has been in su -0 03 52 86 8, v er si on 1 14 J an 2 00 9 Author manuscript, published in "Journal of Structural Geology 31, 4 (2009) 421-443"