Late Carboniferous syn-tectonic magmatic flow at the northern margin of the North China Craton—Evidence for the reactivation of cratonic basement

Abstract

Syn-tectonic magmatic flow, which typically occurs along continental margins or in orogenic belts deformed by tectonic stresses, may indicate the re-melting of middle–lower crust, tectonic setting of the magmatic plutons or the reactivation of cratonic basement. The northern margin of the North China Craton hosts Late Carboniferous plutons that show evidence of magmatic flow. The plutons were emplaced at 320–300Ma, as indicated by zircon U–Pb SHRIMP and LA–ICP–MS dating, rather than high-grade metamorphic rocks such as Archean or Paleoproterozoic gneiss, as previously thought. These granitic plutons, composed of granite and granodiorite, contain a south-vergent shallow-dipping transposition foliation and recumbent folds. Features of magmatic flow are overprinted by a north-dipping foliation and solid-state thrusting and shearing deformation. Aluminum-in-hornblende geobarometry shows that magmatic flow occurred in the middle to lower crust at a depth of approximately 19±5km. The occurrence of southward magmatic flow at 320–300Ma at the northern margin of the North China Craton indicates the reactivation of cratonic basement.