A Middle Silurian-Early Devonian Magmatic Arc in the Qinling Mountains of Central China

Abstract

An early to middle Paleozoic magmatic arc was discovered in the Qinling orogenic belt of central China that marks the boundary between the North China craton and the South China craton. The arc was built on the deformed southern passive continental margin of the North China craton, which has been modified by the accretion of an oceanic island arc in early Paleozoic time. U/Pb analyses of zircons from granites indicate short-lived arc activity from Middle Silurian to Early Devonian time. Trace element analyses as well as REE analyses of I-type granites are consistent with the interpretation that the magmatic arc developed above a north-dipping subduction zone. Termination of magmatic activity was probably caused by the initiation of collision between the North China craton and the South China craton. This interpretation is consistent with faunal data and places new constraints on the Paleozoic tectonic evolution of the Qinling belt.