Rare Earth Elements in a Speleothem Analyzed by ICP-MS, EDS, and Spectra Cathodoluminescence.

Abstract

Spectra cathodoluminescence (CL) emissions of a stalactite from Castañar cave (west-central Spain) exhibit spatially resolved spectra patterns of Mn2þ and rare earth elements (REE3þ). Although the REE3þ signal is smoothed in the speleothem background sample, the REE-enrichment in some growth layer derives from the presence of cerite, xenotime, monazite, and cerianite in the shale matrix. The spectra CL of both host rock and some calcite-aragonite layers show a wide range of spectral luminescence emissions attributed to REE3þ, mainly Sm3þ, Dy3þ, and Ce3þ. The high Mn2þ-REE3þ anomalies in the inner calcite-aragonite layer could indicate its growth during a phase with stronger weathering of host rock and a more active dynamic hydrology.