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Published online by Cambridge University Press: 01 May 2009
Previous radiometric age determinations for the Criffell–Dalbeattie and Cairnsmore of Fleet Newer Granite intrusions are briefly reviewed. Thirteen fission-track dating results are presented for the co-existing accessory minerals sphene, zircon and apatite separated from the two granites. The mean sphene apparent age of 401±10 Ma and single zircon apparent age of 389±26 Ma are interpreted as the age of initial post-intrusion cooling of the granites. Results from apatite are discordant with those of sphene and zircon. Four determinations give a mean Upper Cretaceous apparent age of ∼ 80 Ma which is not readily interpreted. A single apatite determination upon a sample located adjacent to a basaltic dyke yielded a Tertiary age.