D.M. Moore Georg H. Grathoff 1996 <p>Illite polytype quantification allows the differentiation of diagenetic and detrital illite components. In Paleozoic shales from the Illinois Basin, we observe 3 polytypes: 1M_d, 1M and 2M₁. 1M_d and 1M are of diagenetic origin and 2M₁ is of detrital origin. In this paper, we compare experimental X-ray diffraction (XRD) traces with traces calculated using WILDFIRE&copy; and quantify mixtures of all 3 polytypes, adjusting the effects of preferred orientation and overlapping peaks. The broad intensity (&ldquo;illite hump&rdquo;) around the illite 003, which is very common in illite from shales, is caused by the presence of 1M_d illite and mixing of illite polytypes and is not an artifact of sample preparation or other impurities in the sample. Illite polytype quantification provides a tool to extrapolate the K/Ar age and chemistry of the detrital and diagenetic end-members by analysis of different size fractions containing different proportions of diagenetic and detrital illite polytypes.</p> application/pdf 10.1346/CCMN.1996.0440615 en The Clay Minerals Society Illite polytype quantification using Wildfire© calculated x-ray diffraction patterns article