APPLICATION OF SCANNING ELECTRON-MICROSCO PY AND CATHODOLUMINESCENCE TO GEOLOGICAL-MATERIALS (SULFATES, CARBONATES, SILICATES)

A scanning electron microscope, coupled with a cathodoluminescence spe ctrometer, allows the detection of chemical zonations that are often n ot detected by electron probe microanalysis: it is then possible to id entify different generations of minerals. In the drill core from Balaz uc, Ardeche, several generations of sulphates (anhydrite) and carbonat es (calcite, dolomite, siderite, magnesite and ankerite) were observed with this method; in most cases, their cathodoluminescence colour cou ld be correlated with the presence of trace elements. In order to assi gn with certainty the chemical composition to the different cathodolum inescence emission peaks and bands, it is preferable, if not required, to compare the observed spectra of natural samples with those obtaine d from synthetic minerals, doped with known activators: such a compari son has been made for synthetic zircons doped with rare earth elements .