Quantitative mineralogical analysis of carbonate sediments by X-ray diffraction: a new, automatic method for sediments with low carbonate content



    1. Laboratoire de Géologie Générale, Université Catholique de Louvain, Bâtiment Mercator, Place Louis Pasteur, 3, B-1348 Louvain-la-Neuve, Belgium
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A new X-ray diffraction method has been developed whereby the weight percentages of aragonite and low and high-magnesium calcite are determined from the integrated peak areas of samples. Peak areas are measured by a step scanning method. The weight percentages of MgCO3 in calcite are determined from the angular position of the calcite peak. This technique uses a direct calculation method which simplifies the preparation of the samples and the calibration processes and increases the quality of the results. The fully automatic method uses a desk-top computer to guide the diffractometer and to carry out the necessary calculations. Tests on precision and accuracy of the method indicate that results with less than ± 4% error (mineral %) and ± 0.6% error (MgCO3%) are obtainable for all samples even those with a low (10%) carbonate content.