Xenotime in the Lower Buntsandstein of Central Europe: Evidence from cathodoluminescence investigation

Xenotime and zircon in heavy mineral separates of siliciclastic sediments can easily be distinguished by means of cathodoluminescence (CL). All shades of bright blue, yellow and grey to white colours have been reported for zircon while only bottle green to greenish yellow colours have been found in xenotime in heavy mineral separates of Lower Buntsandstein samples as well as in two samples from crystalline rocks from Bahia (Brazil) and the Karpaty Mts. (Slovakia). The CL-spectra of both minerals are commonly dominated by narrow emission bands of rare earth elements, especially Dy3+. The two different crystal lattices induce differences in the intensity ratios of the emission lines that are thought to be the reason for the different CL-colours. Additionally, intrinsic broad bands that may occur in the CL-spectra of zircon are missing in the xenotime spectra. The possibility to distinguish minerals with similar optical properties underlines the large potential of cathodoluminescence in sedimentary petrology.