Petrogenesis of Mesozoic granitoids and volcanic rocks in South China: A response to tectonic evolution

Abstract

This paper summarizes the new results on the petrogenesis of Mesozoic granitoids and volcanic rocks in South China. The authors propose that these rocks were formed in time and space as a response to regional tectonic regime change from the continent-continent collision of the Indosinian orogeny within the broad Tethyan orogenic domain in the Early Mesozoic (T1-T3) (Period I) to the largely extensional setting as a result of the Yanshanian orogeny genetically associated with the NW-WNW-ward subduction of the paleo-Pacific oceanic lithosphere in the Late Mesozoic (J2-K2) (Period II). Of the Period I Indosinian granitoids, the early (T1-T21) ones are syn-collisional, and formed in a compressional setting; the late (T22-T3) ones are late-collisional, and formed in a locally extensional environment. During the Period II Yanshanian magmatism, the Early Yanshanian (J2-J3) granitoid-volcanic rocks, which are distributed mainly in the Nanling Range and in the interior of the South China tectonic block (SCB), are characteristic of rift-type intraplate magmatism, whereas the Late Yanshanian K1 granitoid-volcanic rocks are interpreted as genetically representing active continental margin magmatism. The K2 tholeiitic basalts interlayered with red beds are interpreted as genetically associated with the development of back-arc extensional basins in the interior of the SCB. The Yanshanian granitoid-volcanic rocks are distributed widely in South China, reflecting extensional tectonics within much of the SCB. The extension-induced deep crustal melting and underplating of mantle-derived basaltic melts are suggested as the two principal driving mechanisms for the Yanshanian granitic magmatism in South China.