U-Pb zircon and rutile metamorphic ages of Dahomeyan garnet-hornblende gneiss in southeastern Ghana, West Africa

U-Pb dating of zircon and rutile from a Dahomeyan garnet-hornblende gneiss in Ghana/West Africa shows exclusively Neo-proterozoic-age components. Zircon data define a short mixing line with concordia intercept ages of 600+9/-73 Ma and 689+127/-61 Ma. Rutile defines a Pb-216/U-238 age of 576 2 Ma. Morphology and zoning patterns in the zircon suggest that it formed during high grade metamorphism. Peak regional granulite facies metamorphism likely occurred close to the age of the youngest zircon (603 5 Ma). A rutile age of 576 2 Ma can be taken as the time when the cooling isograd passed through approximately 400 degreesC. The older component in the zircon may represent igneous inheritance or early growth during prograde eclogite facies metamorphism no later than 621 3 Ma. (C) 2002 Elsevier Science Ltd. All rights reserved.