Haverá futuro para os diamantes de aluvião no NE de Angola?

Abstract

Since the beginning of this century that diamond exploitations exists in the North-Eastern Angola with economic success. In the last years the civil war and the generalised explosion of smuggling are the cause of serious problems for mining activities. In face of this situation a question arises: will the alluvial mining activities be possible in the future? In our opinion the answer is positive and justified by the geological characteristics of an alluvial diamondiferous unit: the Calonda Formation. This unit is the first sedimentary collector of diamonds after the supergenic destruction of Kimberlites. The scantiness of outcrops and the generally high overburden thickness are serious problems for exploration of Calonda gravels, specifically for the establishment of geological models for sedimentation and diamond concentration. But the overburden thickness is also the reason why this unit is untouchable by the illicit diamond searchers. The use of sedimentological parameters to develop geological models of ore concentration is difficult to use because of the lack of outcrops as well as because of destructive drilling. However drilling data provide several parameters fundamental in the evaluation of the economical potential, that could be used to establish those models. Based on multivariated statistical analysis, relations between different variables are established. With geostatistic methods (Kriging) several geological levels are defined, trying to integrate the results with geological models of sedimentation and ore concentration. This work contains several ideas included in short communications presented in the 31 th International Geological Congress