Abstract
We propose a new modal analysis method using a scanning electron probe microanalyzer with an energy dispersive X-ray analytical system. The procedure is based on the multipoint analysis software of EDAX® Inc. The analysis points are selected as equal interval grids in the secondary electron image (SEI), which covers 3.2 × 2.45 mm2 area as the maximum. The mineral identification of each X-ray spectrum can be done by the combination of the assemblage and content of mineral forming elements. This method can identify most of rock-forming minerals easily, what is an advantage comparing with the conventional modal analysis method under the optical microscope. To obtain the reliable modal data, we can adjust grid intervals depending on the grain size of rock forming minerals and the numbers of the beam acquisition areas depending on the degree of heterogeneity of samples. This technique is available for the rock sample with average grain size between 0.2 and 2.0 mm by the restriction of the minimum enlargement size of the SEI. The new method gives the concordant modal data to those obtained by the conventional point-counting method by several beam acquisition areas for homogeneous samples and by a few tens beam acquisition areas for heterogeneous samples.
