Geodynamic setting of the Yanshanian (Jurassic-Cretaceous) metallogenesis in east China

摘要

The Yanshanian Jurassic-Cretaceous magmatic-tectonic-metallogenic belt in east China is a part of circum-Pacific domain (Fig.1) (Deng et al., 1999). The intrusive rocks are composed of gabbro-quartz monzodiorite-quartz monzonite (or granodiorite) -syenite-granite association with dominant granite. The volcanic rocks consist of basaltic andesite (or shoshonite), andesite (or latite) and trachyte (or dacite) and rhyolite association with dominant latite and andesite, This belt, on an orogenic belt scale, shows the characteristics of continental marginal arc similar to the Andes and West USA, except for the Hercyn-type-like biotite-two mica-muscovite granite belt in Nanling region (Fig.1). Three or four episodes of contractional deformation (folding and thrusting) associated with the molasse formation deposited in the fore-land basin during the Jurassic-Cretaceous time were developed (Deng et al. 2001, 2004). The metallogenesis is attributed to the syn-orogenic (J3) extensional and post-orogenic (Ki) extensional setting of the orogenic processes.