REE Geochemical Characteristic of Apatite: Implications for Ore Genesis of the Zhijin Phosphorite

Abstract

Phosphorite-type rare earth deposits, which are one of the important types of rare earth elements (REE) ore deposits, have attracted increasing attention because of the extreme enrichments in heavy rare earth elements (HREE), including Yttrium (Y). In this study, in situ geochemical analyses of apatite grains from Zhijin phosphorites were conducted using electron probe microanalysis (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Based on EPMA mapping analysis, we show that rare earth elements and Yttrium (REY) entering into the crystal lattice by isomorphism rather than by inclusions of REY-bearing accessory minerals. The post-Archean Australian Shales (PAAS)-normalized REY patterns of the apatite grains are characterized by hat-shaped MREE-enriched patterns. We interpret that this pattern may reflect the REE distribution of seawater at that time. We propose that in a local, reducing environment, dramatically increased the concentration of REY in seawater, and resulted in the MREE-enriched patterns in the ancient ocean. The main mechanism for the genesis of the Zhijin phosphorite deposit is the apatite crystallizes during the mixing process of REY- and P-rich fluid and oxidizing seawater.

Bioleaching of rare-earth elements from phosphate rock using Acidithiobacillus ferrooxidans

“…It was also found that the REEs in phosphate rock mainly occur in dolomite and apatite, and exist in the form of the isomorphism phase (Xiqiang et al . 2020). Compared with the primary phosphate rock, the diffraction peak intensity of dolomite and apatite in the abiotic control group did not significantly decrease, indicating that dolomite and apatite still exist in the tailings.…”

“…Figure 4(a) shows that the mineral composition of primary phosphate rock is relatively simple, and mainly composed of dolomite and apatite, and no independent rare-earth minerals have been found. It was also found that the REEs in phosphate rock mainly occur in dolomite and apatite, and exist in the form of the isomorphism phase (Xiqiang et al 2020). Compared with the primary phosphate rock, the diffraction peak intensity of dolomite and apatite in the abiotic control group did not significantly decrease, indicating that dolomite and apatite still exist in the tailings.…”

Selective removal of dolomite from rare earth element‐bearing phosphorite by flotation and leaching and the adsorption mechanism of agents on mineral surfaces

“…By comparing the contents of major elements and REEs in natural phosphorite, flotation concentrate, and leaching concentrate, the separation effect can be judged. Studies have shown that the contents of REEs increased with the increase of Fap content, 9,29 but there was no evidence to suggest that it increased with the increase of Dolo content 30 . It was currently recognized that REEs mainly replace calcium atoms in Fap in the form of isomorphism, 31,32 and the content of REEs was often positively correlated with the content of Fap.…”

Substitution mechanism of rare earths at fluorapatite characteristic sites: experimental and computational calculations

“…It was urgent to find a RE reserve resource to meet the needs of industrial production (Batapola et al, 2020;Ji and Zhang, 2021). Phosphate contained all Lanthanides except Pm, in which the content of ΣRE (the total RE) was 1098~1688 ppm (Xiqiang et al, 2020). From this perspective, phosphate was a reserved RE resource and had great development value.…”