The zonation and genetic mechanism of Zunyi high-and low-ferrous bauxites

Early Carbonaceous sedimentary bauxite and its aluminum-bearing rock series in the Zunyi bauxite belt have totally undergone sedimentation-accumulation on the slightly southward inclined plantation formed during the late Devonian and Early Carbonaceous Ziyun movement,and the high-and low-ferrous bauxites apparently assume zonation.Original materials of bauxites and the ore-bearing rock series consist dominantly of gibbsite laterite crust formed by illite shale of the Lower Ordovician Meitan Formation.The zonation of bauxite is related to the material-transport distance of the laterite crust,i.e.,the high-ferrous bauxites occur in nearby and high places,and the low-ferrous bauxites appear in distant and low places.Generally speaking,the transport distance is relatively short? and the bauxites were formed by the near-source transport,sedimentation and accumulation.