Crustal evolution and terrane correlation in the eastern Arabian Shield, Yemen: geochronological constraints

Ion-microprobe U–Pb zircon and 40 Ar– 39 Ar geochronology is presented for two gneiss terranes and an island arc terrane in the Arabian Shield of Yemen. These data confirm the presence of late Archaean ( c. 2.95–2.55 Ga) crust in the Al-Mahfid (eastern) terrane, previously inferred from Nd model age determinations; a minor late Archaean component in the Abas (western) terrane is revealed by a single c. 2.6 Ga zircon core. No ages have been obtained corresponding to documented c. 1.8–1.4 Ga events in neighbouring Somalia and Saudi Arabia, but both gneiss terranes are strongly affected by c. 760 Ma Pan-African reworking which is recorded by Pb loss in zircons of the Al-Mahfid terrane and zircon crystallization ages of granitic gneisses and sheets in both the Al-Mahfid and Abas gneiss terranes. 40 Ar– 39 Ar ages obtained from intrusive rocks in the intervening Al-Bayda arc terrane provide a lower age limit of 615 Ma upon terrane assembly. Correlation of pre-Pan-African events within the Arabian–Nubian Shield remains problematic because of the still limited sampling and available geochronology.