| dc.description.abstract | The Konkiep Terrane in Namibia is a major tectonic element within the 1.4-1.0 Ga Namaqua-Natal orogenic belt (NNOB) that extends along the southern edge of the Kalahari craton in southern Africa and represents one of the main convergent margins active during assembly of the Rodinia supercontinent. The oldest unit sampled in the terrane in this study is the bimodal, 1.36 Ga Nagatis Formation, showing partly tholeiitic affinities. Basalts have nearly flat REE patterns and small Nb-Ta anomalies, suggesting a subduction-influenced source either in an intraplate rift setting or a back-arc basin. The 1.33 Ga tholeiitic to transitional, bimodal Welverdiend Formation displays higher concentrations of Ti and Y than the Nagatis, but still shows a negative Nb-Ta anomaly. The Welverdiend magmatism is similar to continental flood basalts. This may indicate that it formed as a result of a heat anomaly melting subcontinetal lithosphere mantle. The calc-alkaline to shoshonitic, 1.2 Ga Barby Formation, which is the most extensive volcanic unit within the terrane, is LREE enriched. The unit has continental arc characteristics; regional relations and facies patterns suggest shoshonitic volcanism occurred in an extensional part of the arc undergoing oblique subduction. The youngest volcanic unit in the terrane, the bimodal, 1.1 Ga Guperas Formation, shows within-plate geochemical signatures, consistent with recent paleomagnetic and geochronological evidence that the unit represents part of the Umkondo LIP that was emplaced across the Kalahari craton after cessation of arc magmatism in the Konkiep terrane. | |
