The Nature of K‐feldspars of a Chernozemic Soil in the Canadian Prairies

Abstract The nature of the K‐feldspars of an Orthic Brown Chernozemic (Aridic Haploboroll) soil profile developed from glacial till deposits in Saskatchewan, Canada, was studied. The K‐feldspars from selected size fractions between 20 and 2,000µ were concentrated by heavy liquid separation at a specific gravity of 2.59. X‐ray powder diffraction analysis was used to identify orthoclase and microcline, to estimate their relative proportion, and to determine the obliquity, which is the degree of departure from the monoclinic symmetry of K‐feldspars. The concentration of K‐feldspars by heavy liquid separation greatly facilitated the subsequent X‐ray diffraction analysis. All the samples studied contained both orthoclase and microcline, and at least some of the K‐feldspar crystals appear to be perthitic in nature and have a high degree of exsolution. The diffractograms of the comparable size fractions from the major genetic horizons were similar and the proportions of orthoclase to microcline were comparable in the same size fractions. The proportions of orthoclase to microcline usually increased as the particle size decreased in all of the horizons, indicating that this differentiation occurred at the time of deposition of the soil parent material. The obliquity values of microcline of the various size fractions, ranging from 0.82 to 0.87, appeared to be uniform throughout the profile. The obliquity of K‐feldspars and proportions of orthoclase to microcline may have a potential use as a guide in establishing the geological origin of soil parent material and in confirming its uniformity.