The Chinese Phanerozoic gneiss domes: Subduction-related type, collision-related type and combination type of subduction-collision

Gneiss domes are ubiquitous domal structures in all exhumed orogens, and their formation is closely associated with the thermal-tectonic processes (magmatism and/or migmatization) in middle-lower crust. Their occurrence indicates that the middle-lower crust has been exhumed to shallow depth. In general, gneiss domes are primarily cored by granitoid plutons (with weak or no magmatic fabrics) and high-grade metamorphic rocks ( e. g. migmatite) that are immediately margined by granitic gneisses showing magmatic fabrics, and mantled by high-grade schists and gneisses. Most commonly in the whole evolutionary process, the formation of gneiss domes will be subject to the contraction regime triggering by the vertical ascent of crustal flow and subsequent extension regime at the top of the intrusions. Based on the rock assemblages, fabrics, formation mechanism and geological settings of gneiss domes and their relationship with the crustal flow, we analyzed typical gneiss domes in China and classified these Chinese Phanerozoic gneiss domes and gneiss dome systems into three types, namely the subduction-related type, the collision-related type and the combination type of subduction and collision. The subduction-related type is represented by the gneiss domes in the Qinling terrane, the collision-related type is the North Himalayan gneiss domes and the Yajiang ones in the Songpan-Ganze terrane, and the combination type of subductioncollision is the Kongur gneiss domes in the northeastern Pamir and the Linzhi gneiss domes in the eastern Gangdese magmatic belt.