Preliminary Study on Geology and Mineralization of the Bayan Obo Ocean Plate

This paper proposed that the world's largest Bayan Obo rare earth elements (REE) deposit is controlled by the geological evolution of the oceanic plate which subducted from the Asian Ocean towards the northern margin of the North China Carton (NCC). And discussed the geological tectonic development of the Asian Ocean plate in the Bayan-Obo region,and the Neoproterozoic,Early and Late Paleozoic subduction-accretionary complex developed successively during the subduction of the Asian Ocean to the northern margin of the NCC. The origin of the Bayan Obo REE deposit is also discussed. It is believed that the REE-riched carbonatite magma is produced in the so-called special far backarc settings in the northern margin of NCC,which some people call it as far from the arc settings or deformed continental margins settings,instead of oceanic subduction settings (magma arc settings). Compared with the continental marginal arc,far backarc settings are located farther away from the carton or backarc,which is the key storage and transportation space that controls the migration and accumulation of deep ore-forming materials to shallow surface in Bayan Obo,and finally aggregates into large ore deposits and ore-concentrated area. The far backarc settings are far away from the oceanic subduction-convergence zone or subduction zone towards the carton or the carton edge behind the arc,that is,in the extension structure on the lithosphere boundary between the lithospheric boundary of the northern margin of the NCC and the Asian orogenic belt,it is controlled by a large-scale lithosphere discontinuous system or a deep-cut lithosphere fault zone system. The ore-forming carbonatite magma may come from the Asian oceanic crust sediments carrying a Large amount of Fe and REE. It subducted and subdued towards the SCLM deep circulation in the lower lithosphere of the NCC in the late Proterozoic-Early Paleozoic,then it dissolved to form magmatic carbonatites and the REE deposits in the discontinuous tectonic system which deep cutting the lithospheric edge of the NCC.