Bayan obo controversy: Carbonatites versus Iron Oxide-Cu-Au-(REE-U)

Abstract

The Bayan Obo Fe-REE-Nb deposit is the world's largest rare earth element (REE) resource and its genesis has been the subject of much debate for many years. The most popular are the carbonatite-related and hydrothermal Fe oxide-Cu-Au-(REE-U) genetic models. Comparisons of geologic setting, lithology, mineral assemblages, metal associations, geochemistry (particularly REE and light REE/heavy REE ratios), fluid chemistry and isotopics indicate that the Bayan Obo deposit shares features of both types, which are classified differently; that is, the carbonatites model is host-rock based, while the Fe oxide-Cu-Au-(REE-U) model is essentially mineral assemblage and metal association based. A speculative classification scheme is tentatively put forward to link the two models, but many questions remain for further studies. © 2008 The Authors Journal compilation © 2008 The Society of Resource Geology.