Potassium-argon dating of illite components in an earth sample

A process for determining the age of diagenetic illite in an earth sample which contains both detrital and diagenetic illite, comprising the steps of:

• (a) separating the earth sample into a plurality of fractions by a separation means which separates the earth sample into discrete fractions having different sized particles so that each fraction will have a different mean age of illite;
• (b) determining through X-ray diffraction analysis the relative percentage of detrital illite in each fraction;
• (c) determining through potassium-argon age analysis the mean age of total illite in each fraction;
• (d) determining a linear relationship based on changes of the relative percentages determined in step (b) compared to changes in the mean ages determined in step (c);
• and
• (e) determining the age of diagenetic illite by linearly extrapolating said linear relationship to zero percent detrital illite.

A process for determining the age of detrital illite in an earth sample which contains both detrital and diagenetic illite, comprising the steps of:

• (a) separating the earth sample into a plurality of fractions by a separation means which separates the earth sample into discrete fractions having different sized particles, each fraction having particles of illite within a narrow size range;
• (b) determining through X-ray diffraction analysis the relative percentage of detrital illite in each fraction;
• (c) determining through potassium-argon age analysis the mean age of total illite in each fraction;
• (d) correlating said relative percentages and said mean ages to determine a linear relationship between said mean ages and said relative percentages in each fraction;
• and
• (e) determining the age of detrital illite by linearly extrapolating said linear relationship to one hundred percent detrital illite.