Magmatic to carbothermal evolution of carbonatites and metasomatism of Damara calcite marble: Osongombo Carbonatite Complex, NW Namibia

The Osongombo Carbonatite Complex in NW Namibia records magmatic differentiation from calcite carbonatite to ferroan dolomite-and ankerite carbonatite dykes and veins marked by a continuous enrichment of Fe and Mg accompanied by increasing abundance of sulfides and the first appearance of REE-bearing burbankite.This magmatic stage is followed by a carbothermal stage characterised by a distinct mineral assemblage found as vein networks and small patches, which consist of apatite II, baryte, synchysite, parisite and quartz.The emplacement of these carbonatite dykes/veins produced Fe-rich metasomatic reaction zones of variable thickness (mm-to cm) along the contact to Damara marble.While calcite carbonatite exhibits little reaction evidence (besides a change in grain size), ferroan dolomite-and ankerite carbonatites show clear compositional and textural changes.