Laser-induced REE3Â + photoluminescence of selected accessory minerals - An “advantageous artefact” in Raman spectroscopy

- PL of trivalent REE3 + is a common analytical artefact in Raman spectroscopy of minerals.
- Spectra of various accessory minerals were compared with those of synthetic analogues.
- REE-PL of minerals may be used as fingerprint tool for mineral identification.
- The distribution of REE emission-intensities (PL mapping) visualises mineral textures.

Laser-induced photoluminescence of trivalent rare-earth elements (REEs), which is obtained as analytical artefacts in Raman spectra of selected accessory minerals, was studied. Spectra of natural titanite, monazite-(Ce), xenotime-(Y), and zircon samples from various geological environments were compared with emission spectra of synthetic, flux-grown analogues doped with REEs. The latter is of great importance to identify potentially mistakable bands as either Raman or PL signal, and to assign them to certain REE centres. In the samples investigated, various REE centres are excited selectively using 473, 514, 532, 633, and 785 nm laser excitation. Their assignment was verified by photoluminescence-excitation experiments. Luminescence spectral patterns of zircon and titanite vary in dependence of trace-REE concentrations, hence reflecting geochemical growth conditions. “REE artefacts” in Raman spectra of accessory minerals may be used as fingerprint tool for mineral phase-identification. The distribution of REE emission-intensities, revealed by hyperspectral mapping, opens up the opportunity to visualise mineral textures, complementary to cathodoluminescence imaging-techniques.