Indosinian intensive exhumation: Evidence from geological mapping, geochronology and structural geology at the Taili Beach, North China

摘要

Crustal deformation can be closely associated with Earth surface process. A combined approach of geological mapping, petrology, geochronology and structural analysis of the Taili Beach, North China, reveals a detailed magmatic and deformation history associated with orogenesis and intensive exhumation. Three groups of rocks developed along the Taili beach, including gneisses, mylonites and massive granites. Gneisses recorded near E-W-trending rootless fold and subvertical gneissosity of lower structural level. Mylonites exposed along ENE-trending ductile shear zone, with porphyritic protomylonite permeated into gneiss of lower-middle structural level. Gneisses formed in Neo-Archean to Paleo-Proterozoic, were modified by similar to 230-220 Ma magmatic and deformation event. This tectonic event is related to the Indosinian orogenesis, leading to the re-melting of the lower crust Archean rocks and intense deformation forming subvertical gneissosity and sinistral mylonites zones within N-S direction compression. The structural analysis indicates that rootless fold Si formed at the depth of similar to 24-20 km, gneissosity formed at similar to 18-15 km, while mylonite foliation S-2 formed at similar to 12-10 km and felsic leptynite formed at similar to 8-7 km. Massive granites intruded into gneisses and mylonites at depth <3 km (not late than 159Ma). The deformation sequence indicates that the Tail crust uplifted nearly 20 km during the similar to 230-220 Ma to similar to 159 Ma. The intensive exhumation in orogenesis may be related to earth surface erosion process.