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New Methods of Dating the Hydrocarbon Generation Based on K-Ar of Diagenetic Illite

Marek Szczerba
Polish Academy of Sciences, Institute of Geological Sciences Kraków, Poland
[email protected]

Diagenetic illite can provide K-Ar dates that constrain the timing of hydrocarbon generation, because crystallization of illite occurs in the range of temperatures of the oil window. Unfortunately, this information can be very difficult to extract. The problem is that the diagenetic illite is most often contaminated with the detrital one, and it is impossible to separate them physically. Alternative approaches to this problem are possible and the aim of this project is to develop them and to test if these methods can be successfully applied to real basins.

The first of the developed methods is an improved version of the Illite Age Analysis. Using this approach it is possible to calculate the ages as well as the potassium ratio of diagenetic and detrital illites. It was found that if potassium amount is different in these end-member illites this approach gives more reliable results than the original Illite Age Analysis.

In the second approach the illite crystal thickness distribution is extracted from X-ray diffraction patterns to study proportions between diagenetic and detrital illite. For the purpose of this study a computer program has been written and is already being tested.

The third approach is based on chemical analyses of few grain size fractions with different proportions of diagenetic and detrital illite. This method employs chemical data for elements, which concentrate in illitic minerals (like K, B, Ar and Li). It was found that this approach can give important supplementary information which can constrain results of other methods.


AAPG Search and Discovery Article #90094 © 2009 AAPG Foundation Grants in Aid