Brownfields exploration using semi-airborne transient electromagnetic surveys at the giant Bayan Obo REE-Nb-Fe deposit, Inner Mongolia, China

Abstract

The Bayan Obo deposit is the largest polymetallic rare-earth and Nb deposit in the world. However, the formation of rare earth resources has been controversial for a long time due to the fact that there is still no consensus on the enrichment mechanism of the metal elements and shape of the ore body. In order to address this controversy, we conducted a semi-airborne transient electromagnetic survey covering the Bayan Obo Main- and East-pit areas and thus revealing the shape of the concealed mineralization. A significant induced polarization anomaly was identified forming a narrow band that extends from northwest to the southeast and it is consistent with previous geological interpretations and the shallow nature of the known rare-earth mineralization. By integrating the geological survey data and the inversion results, we further investigated the shape of the orebodies. Using “low resistivity and high chargeability” as the criterion for identifying potential ore-bearing rock, we documented three possible concealed ore bodies, two of which have been intersected by recent drilling data. These findings provide new research materials for studies on the mineralization mechanism of the Bayan Obo deposit and the estimation of its resources.