Quantitative high resolution cathodoluminescence spectroscopy of diagenetic and hydrothermal dolomites

A combination of high resolution cathodeluminescence-spectroscopy (HRS-CL = high resolution spectroscopy of cathodoluminescence emission) with spatial resolving trace element analyses (PIXE = proton induced X-ray emission) is used to establish a method for the quantitative determination of the Mn-co ntent of diagenetic and hydrothermal dolomites using the measurements of pe ak areas of Mn-activated CL emission bands. This method takes into account the overlap of the CL broad bands of Mn2+ in the Mg- and the Ca-lattice-pos ition of dolomite. There is a linear correlation between the peak areas and Mn concentration up to approx. 1000-1500 ppm. Thus. CL spectroscopy allows a determination of Mn concentrations below the abilities of PIXE (10-15 pp m) to less than 1 ppm by extrapolation of this linear relation. Up to an Fe-content of approx. 2000 ppm, no quenching effect of Fe on this linear relationship occurs. However, Fe-contents above 2000 ppm result in a decrease of Mn-induced luminescence. Even at Fe-concentration > 25,000 ppm spectroscopy reveals that Mn-activated CL of dolomite is not entirely exti nguished. (C) 2001 Elsevier Science B.V. All rights reserved.