An investigation into the rare earth elements of two alkaline-carbonatite complexes, Namibia

Abstract

No abstract. The following is taken from the author's Introduction, and also from his Conclusion:

(1) Both Osongombo and Kalkfeld have experienced post crystallisation fenitisation. The major source of the K-CO2 bearing fluids was probably the crystallising ferrocarbonatitic magma. Fenitizing fluid temperatures were probably 230°C and migrated through the country rocks through structurally controlled routes. The fluids migrated under a maximum lithostatic pressure of 5Kb, corresponding to approximately 17Km depth (average crustal density of 2. 9gcm-1 assumed). The fluids have enriched the rocks surrounding the carbonatites in REE and have hence caused the REE to be distributed over the complex. This will have the effect of reducing the abundance of the REE in the carbonatites and giving them a lower economic potential

(2) Large variations occur in the REEabundances within each carbonatite, particularly the Kalkfeld carbonatite. This may be due to local differences in the degree of fenitization, local differences in the composition of the parent magma, or chemical weathering effects

(3) The ion-exchange technique appears to be useful in a achieving a degree REE separation from the rock matrix. However, 100 percent efficience is not seen. The technique does remove many spectral interferences created during the analysis by the trace element oxides in the rock matrix. Ba is not separated from the REE and spectral interference from barium oxides has occurred, as has interference within the REE themselves although these can be accounted for