Summary Mean values of available radiometric age determinations on micas from the Skiddaw, Shap and Eskdale granites are 399, 393 and 383 million years respectively. The possible significance of these ages is discussed with respect to the geological setting of the intrusions. Whole rock potassium-argon age determinations on the Ennerdale Granophyre and the Carrock Fell gabbro-granophyre complex show that there has been loss of argon but are indicative of a Caledonian age.
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Brown et al. (1964) studied this question.
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