New SIMS U-Pb age on zircon from the Epembe carbonatite dyke, NW Namibia: Implications for Mesoproterozoic evolution of carbonatites at the southern margin of the Congo Craton

Abstract The Epembe carbonatite dyke is situated approximately 80 km north of Opuwo, NW Namibia. The 10 km long dyke is dominated by massive and banded sovitic carbonatite intrusions. Two types of sovite have been recognized: (1) coarse-grained light grey Sovite I which occurs in highly brecciated and fractured zones and (2) medium to fine-grained Sovite II which hosts significant concentrations of pyrochlore and apatite. The contact zone between the carbonatite and basement gneisses is marked by K-feldspar fenite. Zircons from Sovite II were dated with Secondary Ion Mass Spectroscopy (SIMS) yielding a concordia intercept age of 1184 ± 10 Ma (MSWD = 0.65, Pof = 0.42) corresponding with the weighted mean 207 Pb/ 206 Pb age of 1173 ± 12 Ma (N = 20, MSWD = 1.2) as the crystallization age for the Epembe carbonatite. Our result presents a slightly older age than previously published data for the Swartbooisdrif ferrocarbonatites about 35 km to the east of Epembe. As calcitic carbonatites usually represent the early magmatic phase during the evolution of carbonatite magmas, the calcitic and ferrocarbonatite veins linking the two carbonatite suites at the southern margin of the Kunene Intrusive Complex (KIC), suggests that the spatially associated sovitic and ferrocarbonatite dykes are genetically related and form part of carbonatite melts emplaced about 180 Ma after the KIC magmatic event.