Exhumation processes of continental crustal metamorphic complexes

Abstract

Formation and exhumation processes of metamorphic core complexes are critical to understanding large-scale extension, which accommodate activity of mid- to lower-crustal levels. Structural observations, kinematic criteria, microstructural fabrics and metamorphic histories need to be examined in great detail. Generally, a metamorphic core complex has strongly deformed metamorphic gneiss core (footwall), detachment fault system and sedimentary cover (hanging wall) with lightly metamorphism and deformation. The footwall of gneiss dome presents a strongly ductile deformation domain, accompanied by different ages of granitic intrusions. The development of a metamorphic core complex is relative to the progression of different metamorphic and deformation stages during cooling and exhumation, producing a characteristic sequence of (overprinted) meso‑ and microstructures and textures within the low-angle extensional detachment along upper margins of the metamorphic core complex. The wide temporal range of retrogression within the metamorphic core complex coincides in age with retrogressive deformation. In many cases, upward motion along a detachment (ductile low-angle normal fault) and internal ductile thinning implies gradual exhumation with the youngest exhumation along a rolling hinge at the trailing edge of the metamorphic core complexes. The study aims to set up a scheme between several possible end-member type cases of exhumation mechanisms of metamorphic core complexes.