Margret C. Fuchs

Feldspar flotation as a quartz-purification method in cosmogenic nuclide dating: A case study of fluvial sediments from the Pamir

Graphical abstract

Emission spectroscopy for the identification of rare earth elements using laser-induced photoluminescence

We present rare earth element (REE) emission spectra stimulated by lasers with wavelength of 325 nm, 442 nm and 532 nm. Measured spectra represent REE standards in phosphates and fluorides, one set embedded in epoxy resin and one set in form of free-standing single grains. The comparison of emission features from the different specimen allows to evaluate, which emission peaks are robust and unequivocal for REE identification. Results showed that photoluminescence spectroscopy allows successful identification of characteristic emission peaks for Dy³⁺, Er³⁺, Eu³⁺, Gd³⁺, Nd³⁺, Sc³⁺, Sm³⁺, Tb³⁺, and Yb³⁺, when using laser stimulation at 325 nm. However, strong matrix emissions such as from epoxy resin may mask weaker luminescence emissions. In such cases, the adequate choice of longer stimulation wavelength is crucial to suppress the strong matrix emission without loosing the REE luminescence. Using laser stimulation at 442 nm and 532 nm shows promising results, but the optimal laser wavelength seems to be REE-specific and consequently, requires comprehensive analyses.

Tectonic and climatic forcing on the rivers in Pamir

The high mountains of Pamir provide a fascinating natural laboratory to study geodynamic processes and their surface feedbacks. The ongoing India–Asia convergence controls the topographic growth, while the transition from westerlies to Indian summer monsoon-driven climate sets the pace for erosion processes. The role of climatic and tectonic factors is especially well recorded by the Pamir Rivers that reflect considerable changes in discharge and base levels and corresponding reorganization of the drainage network. In particular at the Pamir Plateau, the intercalation of glacial and fluvial sediments and massive landslides witnesses the complex interaction of surface processes in high mountains. We present two figures of characteristic valleys at the Pamir Plateau to describe the complex interaction of surface processes and climatic versus tectonic control factors (Figs. 1, 2).