Shale particles, chemical reactions

It is generally agreed on the basis of TEM evidence (e.g., Rask et ai, 1997) and on the basis of chemical substitution in the several structural sites of illite (e.g., Lanson and Champion, 1991 Awwiller, 1993 Lynch et ai, 1997) that the illitization of smectite, like other replacement reactions in late diagenesis, proceeds through a dissolution/precipitation mechanism. Similar to other replacement minerals, illite also occurs as cements in sandstones as well as in shales, where it forms overgrowths on detrital illite particles and discrete crystals (cements) (e.g., Lanson and Champion, 1991 Rask et at, 1997). 

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