METHODOLOGY FOR OPTIMAL DETERMINATION OF NEW DRILLING PROGRAM IN AN ACTIVE OPEN PIT: EXAMPLE FROM AN ACTIVE SULFATE OPEN PIT IN ALTSI, LASITHI PREFECTURE, EASTERN CRETE

Résumé

For the cement industry the minerals gypsum and anhydrite, due to their similar chemical composition, are of the same importance. In cement production line, the energy requirements for grinding anhydrite are different from that of gypsum. Occasionally, the difference in mechanical properties of the extreme members (anhydride / stiff - gypsum / brittle) can cause problems during grinding procedure. For these reasons it is necessary to be aware of the spatial distribution of these rocks in an active open pit. This knowledge, because of its strict connection with the calculation of the reserves (geological and recoverable), contributes to the direct production planning of the open pit and to the medium and long term planning as well. In order to approach the spatial distribution of sulphate rocks in the active gypsum open pit of INTERBETON S.A. in Altsi (Sitia region, Εastern Crete), new exploration boreholes were drilled. The proposed methodology concerning the determination of the new borehole locations consists of two steps. In the first step detailed geological mapping of the surface sulphate rocks is conducted and in the second step a three dimensional geological model is constructed. The model’s construction is based on data derived from a past drilling program. Those data were enriched with the results of geochemical analysis of 100 new surface samples. The surface samples were taken by means of Wagon Drill accordingly to a predefined grid. Five different drilling scenarios were proposed, contributing to the determination of the optimal drilling program.