Pan-African granulite formation in the Kabye Massif of northern Togo (West Africa): Pb−Pb zircon ages

Abstract

Metamorphic zircons from seven granulite facies orthogneisses of tonalitic composition (enderbites), collected from four different nappes of the Kabye Massif in the Dahomeyide belt of northern Togo, were dated by the Pb±Pb evaporation method. They yielded consistent Neoproterozoic ages with a mean of 612.5 0.8 Ma, interpreted to reflect the peak of regional granulite facies metamorphism following Pan-African continental collision between the West African and Benin-Nigerian plates. These results support previous ages obtained by various chronometers on high-grade rocks from the same suture zone and from surrounding units in Togo, Benin and Ghana. They are also similar to zircon ages from granulites in the Mozambique belt of souteastern Africa. These Pan-African metamorphic ages reflect continental amalgamation resulting in the formation of the Gondwana supercontinent towards the end of the Neoproterozoic.

Petrological and Geochemical Characteristics of Mafic Granulites Associated with Alkaline Rocks in the Pan-African Dahomeyide Suture Zone, Southeastern Ghana

“…Also Hirdes and Davis (2002) reported U-Pb zircon ages of 603 ± 5 Ma from the mafic granulites from the Shai Hills area which confirm the timing of peak metamorphism in the suture zone. Similar age of 613 ± 1 Ma from zircon evaporation ( 207 Pb/ 206 Pb) was reported by Affaton et al (2000) for the suture zone rocks in northern Togo. Hornblende separates from the mafic granulites yielded 40 Ar/ 39 Ar ages between 587 and 567 Ma, interpreted as the time of exhumation of the nappes (Attoh et al, 1997).…”

Pan-African Paleostresses and Reactivation of the Eburnean Basement Complex in Southeast Ghana (West Africa)

“…The PanAfrican tectogenesis is also characterized by progressive eastward superposition of five-phase deformation, considered as Dn, Dn+1, Dn+2, Dn+3, and Dn+4 [1,13]. The Dn phase is coeval with the granularization resulted from the collision between the eastern margin of the West-African Craton and the Benino-Nigerian metacraton [41]. The tangential or nappe stacking phase (Dn+1 phase) corresponds to the formation of the main or regional foliation which is later involved in three postnappe (Dn+2 to Dn+4) folding phases associated with the final development stages of the PanAfrican Dahomeyide Orogeny.…”

P-T conditions of Pan-African orogeny in southeastern Nigeria

“…6. Although the P-T path for the Obudu area is not very certain; probably these rocks have experienced the same P-T evolution as granulite facies rocks from Kabye Massif of northern Togo during the Pan-African orogeny (Affaton et al 2000). A pressure of about 8 kbar (average of pressures calculated in this contribution, considering P estimation uncertainties) corresponds to a depth of 30 km (assuming an average crustal density of ~2700 kg/m 3 ).…”

“…6 P-T conditions of formation of the studied rocks. The schematic P-T path is modified after Affaton et al (2000) Aluminosilicates equilibria and granite melting curves are provided for comparison. Granulite facies metamorphic age (ca.…”