Figure 18. K-Ar evolution diagram.
Most samples approach the reference 370 Ma isochrone crossing atmospheric
40Ar/36Ar ratio. However several samples from the Kovdor and Vuoriyarvi
Complexes are well above the isochrone implying trapped Ar with initial
40Ar/36Ar
~4,000. Samples having low K/
36Ar ratios (inset) also show occurrence of excess
trapped Ar with
40Ar/36Ar
3,000. Host rocks of the dyke Complex are not
considered because of their older age.