The formation and its geologic significance of Late Triassic-Jurassic accretionary complexes and constraints on metallogenic and geological settings in Duolong porphyry copper gold ore concentration area, northern Bangong Co-Nujiang suture zone, Tibet

The outcropped Late Triassic-Jurassic accretionary complexes in Duolong porphyry copper gold ore concentration area of northern Bangong Co-Nujiang suture zone belong to Non-Smith Strata which are totally disordered but partially ordered while accretionary complexes consist of bases and blocks. The bases are Late Triassic-Jurassic sand-muddy flysch formation and blocks consist of basalt, andesite-basalt, limestone, sandstone, silicalite, gabbro and ultrabasic rocks. The accretionary complexes experienced strong tectonic replacement while the bases and blocks were separated by penetrative and unequal extrusion foliations or shearing foliations, suggesting accretionary complexes of a typical orogenic belt. Researches show that the accretionary complexes were derived from the lateral accretion of Late Triassic-Jurassic southern Qiangtang massif, which was related to the subduction from Meso-Tethys Bangong Co-Nujiang oceanic crust to Qiangtang massif. Porphyry ore in Duolong intruded into accretionary complexes or island arc volcanic rocks based on accretionary complexes. Duolong porphyry copper gold ore and its peripherals, such as Naruo,Sena, Nadun etc, occurred in Early Cretaceous granodiorite porphyry body and its contact zone with accretionary complexes, which constrained by E-W pressure faulted structure and N-E strike-slip fault .They have the same metallogenic environments and conditions and belong to uniform porphyry-epithermal system.This new understanding provides new clues for understanding the geological background of the Duobuza-Bolong superlarge porphyry copper-gold deposit and the evolution of the Bangong Co-Nujiang suture zone.