Modelling clay diagenesis using a combined crystalchemistry and thermochemistry approach: a case study on smectite illitization

A general procedure that integrates laboratory mineral analysis and numerical tools is proposed to investigate the main diagenetic processes occurring in clayey and arenaceous sediments. The methodology relies on the use of experimental data from natural samples as input, on the use of numerical algorithms to estimate the thermodynamic parameters of site-specific dehydrated phyllosilicates, and produce an internally consistent thermodynamic database in a ready-to-use format for the Geochemist's Workbench, PHREEQC, and TOUGHREACT simulators. A set of non-isothermal 0D and 1D numerical models is set-up to explore the efficiency of smectite-illite transformation under variable geochemical conditions.