ASPECTS ON THE ILLITIZATION OF THE KINNEKULLE BENTONITES

Earlier interpretations of the conversion of the virgin smectite of th e Ordovician Kinnekulle K-bentonites into the present mixed-layer illi te/smectite imply that it took place through charge increase of the sm ectite with subsequent uptake and fixation of potassium. Recent analys es show that the layer charge of the smectite component of the I/S is in fact low and they suggest that neoformation of a separate illite ph ase took place. Pytte's kinetic model gives good agreement with the ac tual conversion rate for an activation energy of about 25-27 kcal/mole , depending on the adopted rate parameters, temperature history and as sumed potassium source. In the Kinnekulle case the rate-controlling fa ctor appears to have been the supply of potassium, which is concluded to have required large-scale, heat-induced groundwater convection.