Aspects of ultrabasic and basic alkaline intrusive rocks from Bitterfontein, South Africa

Magmatism and continental breakup at the west margin of southern Africa: A geochemical comparison of dolerite dikes from northwestern Namibia and the Western Cape

“…intrusive center (Figure 4) of Early Cretaceous age (de Beer et al, 2002). Still younger (Tertiary), minor intrusions in this area consist of numerous plugs and discontinuous dikes of alkaline mafic to intermediate compositions (McIver, 1981;Moore and Verwoerd, 1985;de Beer et al, 2002). Farther inland in the western Cape, dolerite dikes are more numerous than at the coast and they follow a fairly consistent northwest to southeast trend ( Figure 4).…”

“…Many of these younger intrusions formed along the margins of the Paraná basin in Brazil and northern Uruguay (Morbidelli et al, 1995;Gibson et al, 1997). On the African margin, Late Cretaceous and Tertiary intrusions are known from Angola (Marzoli et al, 1999), central and southern Namibia (Kurszlaukis et al, 1998;Reid et al, 1990) and in the Cape Province (Moore, 1976;Duncan et al, 1978;McIver, 1981;Janney et al, 2002). There are reasonable arguments relating the Late Cretaceous alkalic magmatism in Brazil with the Trinidade-Martin Vaz hotspot track (Gibson et al, 1997;Siebel et al, 2000) but post-breakup magmatism on the South African margin is not satisfactorally explained by hotspot models.…”

Geochemistry of the Early Cretaceous Koegel Fontein Anorogenic Igneous Complex, South Africa

“…Well after continental separation in the late Cretaceous and Palaeogene, a second episode of magmatism affected the Cape Peninsula, forming scattered dykes and plugs of alkaline to ultrabasic composition (Janney et al, 2002;2010). Associated with this late event are small olivine melilitite and nephelinite dykes and plugs in the northern part of the study area, which were described by McIver (1981).…”