Illite crystals in siliciclastic sediments are heterogeneous assemblages of detrital material coming from various source rocks, and, at paleotemperatures >70 °C, of superimposed diagenetic modifications of this sediment (MERRIMAN & KEMP, 1996). Only diagenetic rather than detrital phases should be used to estimate paleotemperatures and to constrain the burial history of folded and thrust sedimentary successions that range in alteration intensity from diagenesis to low-grade metamorphism. In fact, detrital illite only records environments inherited from the past, generally of higher temperature, not directly related to the burial history of the sedimentary successions. A way to distinguish diagenetic and detrital illite is a combined analysis of crystal-size distributions and illite polytypes quantification. The present paper describes a new method for calculating the proportion of detrital and diagenetic illite from crystallite thickness measurements using the MudMaster computer program of EBERL et al. (1996) based on the X-ray diffraction technique of Bertaut-Warren-Averbach (BWA; DRITS et al., 1998).
Aldega, L., Eberl, D.D. (2005). A method for quantifying detrital illite from crystallite thickness measurements, serie speciale, 10, 57-60.