GEOLOGICAL FEATURES AND GOLD MINERALIZATION OF INTRACONTINENTAL SUBDUCTION OROGENIC RELT IN SOUTHWESTERN SICHUAN

As a way of plate tectonic orogeny,intracontinental subduction orogeny can be classified into 2 types:inherited type and induced type.A more than 800 km long Yanshanian-Himalayan intracontinental orogeny belt is determinated in southwestern Sichuan Provice.Its middle part is a megadeep nappe structure,which consists of some inherited steeply-dipping deep-fracture zones and super-crust gently-dipping fault and/or local melten mass,with a series of shallow inhented nappe structures occured between deep structures.Rocks in this structure belt(generally mylonite)offen suffered greenschist-amphibolite face metamophism controlled by structural movement.In obduotion plate,pre-subduction epoch sedimentary rocks in marginal sea basin were folded,and formed mountain chain.Syntecyonic and post tectonic magmatites show obvoious zonation.Accompaning the strong tectogenesis and magmatic activity,some small and isolated intramontane basins were distributed in the obduction plate,with red bed sediments of intramontane molasse formation.In the leading edge of subduction slab are foreland basin.The basin sediment are typical red molasse formation,without magmatic activity.