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Journal of Sedimentary Research

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Powder X-Ray Diffraction Analysis of Homogeneous and Heterogeneous Sedimentary Dolostones

¹ Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, T6G 2E3, Canada
² Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, T6G 2E3, Canada
³ Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, T6G 2E3, Canada

The %Ca (molar Ca/(Ca + Mg) x 100) in sedimentary dolomite, which ranges from 48 %Ca to 62.5 %Ca, can be determined by atomic absorption spectrometry, electron microprobe analysis, or powder X-ray diffraction analysis. The latter procedure, which relies on the fact that the position of the d₁₀₄ reflection depends linearly on the Ca content, offers an easy and relatively inexpensive method of determining %Ca in dolomite. To date, such analyses have assumed that the dolostone is homogeneous with respect to the %Ca content of its constituent dolomite crystals. Herein, the XRD technique is extended to compositionally heterogeneous dolostones.

A considerable amount of important information can be derived from X-ray diffractograms of dolostones if they are analyzed with peak-fitting techniques (PF-XRD). Specifically, this technique allows (1) determination of the %Ca with an accuracy of ± 0.5 %Ca, (2) identification of heterogeneous dolostone samples formed of more than one population of dolomite crystals as defined by their %Ca content, and (3) derivation of the proportion of each population of dolomite crystals with an accuracy of ± 10%. The PF-XRD technique is a powerful analytical tool that provides valuable information on the major-element composition of low-Fe dolomite. Compared to other techniques, the PF-XRD technique is accurate, rapid, relatively inexpensive, and easy to use.

This article has been cited by other articles:

				D. K. McCARTY, V. A. DRITS, and B. SAKHAROV Relationship between composition and lattice parameters of some sedimentary dolomite varieties European Journal of Mineralogy, October 1, 2006; 18(5): 611 - 627. [Abstract] [Full Text] [PDF]