Thermal effects in "oil shales" - Naturally occurring kaolinite and metakaolinite organic associations

Hydrogen bonding between kaolinite and organic material in "oil shales" of the Campanian-Maastrichtian Ghareb Formation was inferred from perturbation of the hydroxyl stretching vibrations, and was confirmed by oxidation and pyrolysis experiments. The kaolinite is not detectable by X-ray diffraction analysis, due to poor crystallinity. Pyrite, although associated with bituminous samples, was probably not formed by reduction or extraction of kaolinite iron (Spiro and Rozenson, in prep.), hence the poor crystallinity of kaolinite is not caused by these processes. Geochemical indicators suggest that this hydrogen bonding occurred at elevated temperatures. This is supported by the geological setting and is related to the thermal "Mottled Zone" event in the area. At the border of the "Mottled Zone" organic associations with metakaolinite were identified in the thermally affected "oil shales". The preservation of kaolinite and metakaolinite may be due to a shielding effect of the enveloping organic material.