Multi-element Content Analysis of Rare Earth Fluorocarbonates from Bayan Obo Deposit by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry

Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry(LA-ICP-MS) can provide a new and simple technique to analyze the chemical compositions of fluorocarbonates for understanding the genesis of rare earth deposits. Bastn site and huanghoite from Bayan Obo in polished thin sections are directly examined. According to the lattice coordination mode and the characteristics of light rare earth-rich in Bayan Obo fluorocarbonates, the major element Ba, Ca in forms of(Ba, Ca)CO₃ and light rare earth in forms of REECO₃F are calculated in the matrix-normalization methods. These results agree with the data of electron microprobe and internal standard method analyses. This improved method solves the problem of quantitative analysis by matrix-normalization when carbon and fluorine elements cannot be measured accurately in ICP-MS and simplifies the test process. The composition comparison results of bastnäsite under multi-beam spot size conditions show large data errors in 5 microns. However, more consistent data are obtained in 10 microns with larger spot size conditions, which satisfy the analysis requirements of small fluorocarbonate grains.