The charge of component layers of illite-smectite in bentonites and the nature of end-member illite

The nature of component layers of mixed-layer illite-smectite and their possible evolution in the Course of illitization have been debated since the 1960s. The present Study is a new attempt to solve these problems, using samples collected from diverse geological formations around the world. Twenty three purified illite-smectites from bentonites and hydrothermal rocks, covering the complete range of expandability, were analyzed chemically, including NH4+ determination, and their structural formulae Were calculated. The exchangeable cations (EXCH) were plotted vs. the fixed cations (FIX) yielding the following experimental regression:status: publishe