Tectonic deformation and origin of tongue-like gneiss in the Jinping area, northern Jiangsu

Abstract：According to detailed mapping in the Jinping area on the southern edge of the Su-Lu orogen, it is affirmed that the boundary between the ultrahigh-pressure metamorphic belt and high-pressure metamorphic belt is a ductile shear zone. No regional folds occur in the area, but instead, as the Jushan granitic gneiss and metavolcanic rocks of the Yuntai Group-complex form a competent rock layer, an incompetent rock layer was formed by metasedimentary rocks of the Jinping Group-complex； they combine to form a “layer cake”-style rock assemblage. In the Indosinian period, dextral shear gave rise to heterogeneous shear deformation； as a result, a rootless tongue-like fold of the Jushan granitic gneiss was formed. It is about 10 km long from north to south and about 5 km wide. The material movement is south-vergent in the Jinping area.