1 ALUMINIUM CONCENTRATION I N A BAUXITE DERIVED OF GRANITE (IVORY COAST): RELATIVE AND ABSOLUTE ACCUMULATIONS

Two fundamental ways of iron and aluminium enrichment have been evidenced in Ivory Coast on a bauxitic profile derived from granite by pertrographical and mineralogical analysis:.- the in situ evolutians bounded to the weathering which pseudo-morphose the parent minerah and pnoduce an relative accumula-tion;- the transfer of material in solutizan or in particle which pro-duce albsiolute accumulatioa. The historical succession af these two process give way to a pro-gressive hardening of Ithe original isaltmite with!preserved granitic texture. A relative quantification of the weathering and transfer plasmas is proposed according t,o;the isovolumetric metho#d. So one can show:- the importance of the absolute accumulation which appears as the first weathering stages and which at the end represents more than half lof the indurated bauxitic material;- that the hardening of these bauxites is caused by the multipli-cacity of the transfers