Abstract
SUBSEQUENT to the publication of our earlier communication1 a few additional critical samples of basement rocks from north-eastern Greenland were obtained and analysed. These are given in Table 1. The rubidium–strontium determination on the potassium feldspar cogenetic with the biotite from the alkali granite (GAA–135) confirms the presence of an ancient basement in this region. Even this age of 2,290 ± 70 m.y. must be regarded as a minimum due to the possibility of earlier metamorphic events. Since the potassium–argon on the biotite from this rock gave an apparent isotopic age of 1,900 ± 50 m.y., it seems unlikely that the 87*Sr/87Rb ratio of the feldspar was affected by the Caledonian orogeny.
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