The occurrence characteristics and recovery potential of middle-heavy rare earth elements in the Bayan Obo deposit, Northern China

Abstract

The Bayan Obo deposit is a world-class Fe-REE-Nb deposit, and its reserves of rare earth element (REE) resources rank the first over the world. In the face of the current situation of insufficient utilization rate of rare earth resources and scarcity of middle-heavy rare earth elements (M−HREE) resources, the Bayan Obo deposit with such a huge amount of M−HREE cannot be underestimated. In this paper, the occurrence characteristics of M−HREE in different types of iron ore in the Bayan Obo main ore body are studied by using field emission scanning electron microscope (FESEM), energy dispersive spectrometer (EDS) and advanced mineral identification and characterisation system (AMICS), and the enrichment mechanism is also discussed. The results show that both Sm and Y are the most abundant M−HREE in each type of iron ore in the main ore body, and the content of M−HREE accounts for 1.41%–5.57% of total REE, among which the content of M−HREE in aegirine type Nb-REE-Fe ore (824.47 ppm) and fluorite type Nb-REE-Fe ore (794.82 ppm) are higher, and the content of M−HREE in massive type Nb-REE-Fe ore is lower (318.49 ppm). The main minerals containing M−HREE are bastnasite, parisite, Huanghoite, monazite, aeschynite and fergusonite, among which the content of M−HREE in fergusonite and aeschynite are the highest. According to the characteristics of mineral paragenetic association of REE in this ore district, it is believed that the REE migrates mainly in many different forms of complexes. Heavy rare earth elements (HREE) mainly experienced carbonatite magmatism stage, sodium-fluorine metasomatism stage and late vein mineralization stage, and finally got enrichment.