Caledonian subduction, repeated activation, and multiple episodes of mineralization of the Bayan Obo REE-Fe-Nb ore deposit, Inner Mongolia, China
Chao, E. C. T.; Tatsumoto, M.; McKee, E. H.
published: Nov 27, 1995
ArtNo. ESP136000501007, Price: 19.00 €
The world's largest known rare earth element (REE) ore deposit is Bayan Obo, in Inner Mongolia, China. It is a stratabound, wall-rock-controlled, hydrothermal, epigenetic deposit in marble host rocks of the Bayan Obo Group. The ore deposit has an extremely complex mineral paragenetic sequence and complicated metasomatic and regional metamorphic history. The mine region, 16 km long and 2-3 km wide, consists of a complex syncline with the ore-bearing marble unit on both limbs of the syncline and a shale, slate, and schist caprock unit in the middle. The ore deposit is on the northern flank of the North China (Sino-Korean) Archean-Proterozoic craton. The marble and pelitic caprocks of the Bayan Obo Group represent a shelf facies that unconformably overlies the marginal platform of the craton. The host marble unit in the upper part of the Bayan Obo Group is of Middle Proterozoic age, according to algal and fungal fossils. The minimum age for the Bayan Obo Group of about 1.26 Ga is based on a 40Ar/39Ar minimum mineral age of magnesio-riebeckite (taking into account possible partial resetting due to later metamorphic effect) from a vein crosscutting a quartzite unit of the Bayan Obo Group.