Structure of late Variscan Millevaches leucogranite massif in the French Massif Central: AMS and gravity modelling results

Abstract

In the Limousin area, Variscan leucogranitic plutons are spatially associated with normal faults and major strike-slip shear zones that are a continuation of the South Armorican shear zone. Our study focuses on the large N-S-trending Millevaches granitic massif (Massif Central, France), and intends to highlight, through gravity modelling, structural and anisotropy of magnetic susceptibility (AMS), the massif structure at depth and to discuss the mode of emplacement of granites within a strike-slip tectonic context. The mica subfabric suggests that the magnetic foliations display a general NW-SE sub-horizontal pattern on both sides of the N-S Pradines dextral wrench fault zone that deforms the core of the massif on 5 km width. The magnetic lineation trend exhibits a sigmoïdal pattern, N-S in the Pradines fault zone and NW-SE on both sides of it, which are consistent with a dextral wrench component. The horizontal magnetic foliations and lineations are consistent with the thin granite laccolith model. There is no significant imprint of the extensional Variscan belt collapse on the internal fabric of Millevaches granites than the tectonic dextral transcurrent movement prevailing in this area.

Late-Variscan emplacement and genesis of the Vieira do Minho composite pluton, Central Iberian Zone: Constraints from U–Pb zircon geochronology, AMS data and Sr–Nd–O isotope geochemistry

“…Quartz grains also present a chessboard-like texture indicating both ‹a› and ‹c› dislocation slip occurring during high temperature deformation (e.g. Gébelin et al, 2006).…”

Transpressional tectonics and Carboniferous magmatism in the Limousin, Massif Central, France: Structural and40Ar/39Ar investigations

“…The granite has subhorizontal NW‐SE magnetic foliations and magnetic lineations [ Jover , 1986]. A recent gravity study has modeled the Guéret granite as a laccolith, less than a few hundred meters in thickness [ Gébelin et al , 2006]. These gravity results did not identify the feeder zones nor the chamber from which the granitic magmas originated.…”

Regional stress field around the Taigu fault zone in Shanxi Province, China

“…Since Graham (1954) initially proposed this method, it has been widely used to constrain strain in many studies (Tarling and Hrouda 1993;Parésand van der Pluijm 2002;Gébelin et al 2006;Mamtani et al 2011;Gentoso et al 2012;Fleming et al 2013). Numerous studies based on mathematic modeling (e.g., Owens and Rutter 1978;Hrouda 1993), laboratory experiments (e.g., Alford 1987, 1988;Till et al 2010) and field rock deformation surveys (e.g., Kissel et al 1986;Parés et al 1999) indicate that the AMS can be idealized as a symmetric second rank tensor and represented as an ellipsoid with three perpendicular principal axes, K 1 , K 2 , and K 3 (maximum, intermediate and minimum principal axes, with…”