exhumation; deformation; fluid-rock interaction; Helvetic nappes; European Alps; Helvetic Alps; folding; faulting; extension
Campani M, Herman F, Mancktelow N (2010), Two- and three-dimensional thermal modeling of a low-angle detachment: Exhumation history of the Simplon Fault Zone, central Alps, in JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
Campani M, Mancktelow N, Seward D, Rolland Y, Muller W, Guerra I (2010), Geochronological evidence for continuous exhumation through the ductile-brittle transition along a crustal-scale low-angle normal fault: Simplon Fault Zone, central Alps, in TECTONICS
The Simplon Fault Zone is the major Neogene tectonic structure controlling exhumation in the Central Alps. This project is the continuation of a study that until now has focused on the Simplon Fault Zone in the region where it is best defined, from the Val d’Ossola over Simplon Pass and into the Rhone Valley. The proposed continuation project will extend these field and laboratory studies to the west along the Rhone Valley and consider the deformation structures associated with Neogene orogen-parallel extension in the Helvetic nappes and underlying Aar massif (i.e. within the footwall of the Rhone-Simplon Fault Zone). Because of the smaller amount of exhumation, metamorphic conditions in this footwall segment did not exceed lower to middle greenschist facies and much deformation occurs around the brittle-ductile transition, continuing with increased exhumation into fully brittle conditions. Brittle fracture is strongly influenced by pore-fluid pressure and is now marked in the field by fibrous pressure shadows, veins and cataclasites sealed by newly precipitated quartz and calcite. These structures provide a chance to study fluid-rock interaction during deformation and exhumation and allow an assessment of the source of these fluids (e.g. metamorphic fluids from below or meteoric water from above). Fluids in small-scale structures, such as pressure shadows and veins, are likely to be effectively rock-buffered, but an isotopic signature of the infiltrating fluids may still be preserved in major faults and particularly within the immediate footwall of the Rhone-Simplon Fault Zone itself. The geometry and kinematics of the study region is fully 3-D, involving interacting folding and thrusting related to convergence, together with coeval and subsequent faulting and vein formation related to extension and exhumation. Ar-Ar and Rb-Sr dating of synkinematic mineral growth (especially white mica) can provide the important 4th dimension of absolute time, determined for specific points on the relative history, obtained from overprinting relationships in the field. The overall aim is to develop a 4D model of the progressive transition from folding, thrusting and crustal thickening to extension, faulting and exhumation in the Helvetic nappes and external massifs within the footwall of the Rhone-Simplon Fault Zone.