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Suites of heavy-mineral samples from the Upper Cretaceous sediments and Recent littoral sediments of the eastern Gulf coastal plain have been analyzed by X-ray diffraction techniques and conventional optical methods. Initial results indicate that X-ray diffraction can be used as a routine, rapid, and supplementary method of analysis for large numbers of heavy-mineral samples. Distinctive patterns for specific mineral suites are produced and meaningful associations are thereby determined, from which smaller numbers of samples are selected for detailed, conventional, optical analysis. Detailed identification and quantification of individual mineral elements in each of the irradiated samples are not the immediate purposes, but are possible.
Techniques have been developed to yield reproducible results and to overcome some of the problems inherent to the X-ray diffraction analysis of small, highly cleavable, and high iron content mineral samples. This technique requires uniform grinding of samples to less than 4 microns and the randomly oriented mounting of the particles in an X-ray transparent medium. Variables important to reproductibility and interpretation of data produced by this technique have been studied and their effects determined. These variables include mineral composition, texture of original sample, superimposition of peak positions, size of sample, grinding, orientation of mounted grains, mounting media, and irradiation variables.
Heavy-mineral samples from the Upper Cretaceous sediments in the eastern Gulf coastal region can be separated readily into several distinctive X-ray diffraction-pattern associations that are identical with associations determined by detailed and time-consuming optical analysis.
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