Petrographic and structural study of granitoids of the Taabo Dam site (Central Côte d'Ivoire): Contribution to the understanding of possible loss of water from the Lake

The analysis of two radar images permits the mapping of following petrographic units: the porphyritic granodiorite of Yamoussoukro, the biotite and hornblende rich granodiorite of Toumodi, the plutono-volcano-sedimentary complex of Fetekro-Divo, the biotite-hornblende metagranite, the biotite granitic orthogneiss. It also allows the mapping of four (4) major fractures. These are: NE to NNE-SSW (ZFET and ZFTaY) fractures, NE-SW (ZFTa and ZFOT) fractures, EW (ZFO and ZFT) fractures and finally NW-SE (ZFTaHO and ZFTY) fractures. On the ground, we have distinguished three petrographic facies: syenogranites, monzonitic granites and microgranites. Six main directions of fractures were identified: sinistral N020°-N030°, dextral N050°-N060°, dextral N080°-N090°, dextral or sinistral N100°-N110°, dextral or sinistral N120°-N140°, and sinistral N160°-N000°. Fractures of submeridional direction (N160° to NS) are the oldest. They are followed by those of N020°-N030° directions which cause foliation well marked and microfolds. N100° to N110° and N120° to N140° directions, which replayed several times, crosscut this foliation. Recent fractures are those of N080° to N100° directions. The relations between certain directions of fractures can promote not only horizontal infiltrations, but also vertical flows. This is for example the case of flow in preferential of North-East, West, Southeast and Southwest directions.