Epembe Niobium-Tantalum Deposit,NW Namibia:Ore Deposit Geology,U-Pb Age And Resource Estimation

The Epembe carbonatite study area is situated approximately 80 km north of Opuwo,NW Namibia hosts a potential niobium deposit.Following geological data collection including drilling data,laboratory analysis [using optical microscopy,scanning electron microscope(SEM),cathodoluminescence(CL),electron microprobe(EPMA),sensitive ion microprobe(SIMS)] and use of SURPAC modeling software,we studied the collected data in detail to determine the ore deposit geology,emplacement age and resource of Epembe carbonatite.The results are as follow.The basement gneisses of the area are intruded by anorthosites of the Kunene Complex which is later intruded by nephelinite-syenites suite.A major NW-SE trending fault developed within nepelinite-syenite stock along which Epembe carbonatite intrudes.This carbonatite form a fine to coarse-grained massive s?vite dyke(~10 Km long)which contains mostly calcite(~92%),apatite and pyrochlore co-genetic with minor zircons.Pyrochlore is interpreted as primary magmatic mineral that appear in early carbonatite phases at Epembe.Consequently pyrochlore chemistry indicates a compositional trend from early Ca-rich pyrochlore toward late hydrothermal fluid rich phase.This suggest that as the carbonatite evolve,the early pyrochlore were incorporated in the successive carbonatite intrusive phases leading to a remarkable shift in chemical composition and introduction of elements such as Si,U,Th and Fe especially around the rims of the contained pyrochlore.Enrichment in elements like U and Th lead to initiation of metamictization(metamitic process),alteration and A-site vacancy.The genesis of Epembe niobium deposit is affiliated to the carbonatite magmatism but the process that generated such niobium rich rocks remains unclear and might be formed as a result of crystal fraction and/or carbonate-silicate pair liquid immiscibility.The SIMS U-Pb dating revealed that the emplacement age is restricted between 1148 Ma to 1204 Ma.A best-fit line was determined at(MSW of=0.65,Pof=0.42)with a dominant concordia intercept age of 1184.4 ± 10 Ma as the emplacement age for this carbonatite.Our result presents a slightly older age than the Swartbooisdrif ferrocarbonatites about 35 km to the East of Epembe.As calcitic carbonatites usually represent the earlier phases during the evolution of carbonatite magmas and veins of calcitic and ferrocarbonatite link the two carbonatite suites at the southern margin of KIC,it is therefore suggested that the spatially associated s?vitic Epembe carbonatite and Swartbooisdrif ferrocarbonatite dykes are genetically related and form part of a single melt introduced during a post-KIC tectonic event.Sector B consists of a vein-shaped ore body which contain 3827600 t at 0.16 wt.%Nb2O5 and 4391800 t at 0.01 wt.% Ta2O5.