3D modelling of the Epembe (Namibia) Nb-Ta-P-(LREE) carbonatite deposit: new insights into geometry related to rare metal enrichment

Geological 3D modelling delivers essential information on distribution of enrichment zones and structures in (complex) mineral deposits and fosters a better guidance to subsequent exploration stages. The Paleoproterozoic Epembe carbonatite complex showcases the close relation between enrichment of specific elements (Nb, Ta, P, TREE+Y) and shear zones by structural modelling combined with geochemical interpolation. Three-dimensional fault surfaces based on structural field observations, geological maps, cross-sections and drill-hole data are visualised. The model shows a complex, dextral transpressive fault system. Three dimensional interpolation of geochemical data demonstrates enrichment of Nb, Ta, P and TREE+Y in small isolated, lens shaped high-grade zones in close spatial distance to faults. Based on various indicators (e.g., oscillating variograms, monazite rims around the apatite) and field evidence, we see rather evidence for enrichment during hydrothermal (re-)mobilisation than due to magmatic differentiation related to the formation of the alkaline system. This is further supported by geostatistical analysis of three-dimensional distribution of Nb, Ta, P and LREE with respect to discrete shear zones.