1 - UQAC

Coast.
ABSTRACT
This study focuses on the Issia columbite-tantalite deposit in Central-Western Ivory
Columbite-tantalite deposits in humid tropical areas are generally supergene deposits
associated with gravel. These deposits have been poorly studied and are mined only by
small developers. This is attributed, on one hand to the small scale and the short life of the
individual deposits and, on the other hand to the great thickness of the alteration
overburden in zones of high concentration.
This study has a triple objective: (1) establish a geodynamic model for the Issia
columbite-tantalite primary mineralization and associated minerals; (2) define the factors
controlling the secondary redistribution of the mineralization in detrital environments
through integrating pedo-geomorphologic and geostatistical studies; and (3) determine the
mineralogical species of niobium, tantalum and other associated ore minerals.
The study area includes three granitic massifs intruding sedimentary rocks: the
oriented two-mica granite (Lobo granite), the oriented muscovite granite (Bitapia granite)
and the non-oriented, porphyritic muscovite granite (Issia granite). Field observations and
whole rock analyses show that: (1) the three main granites of the region are produced by
deep seated processes which generated partial melting of the crust; (2) they were formed by
fractional crystallization during the syn to late-D2 period of the Ebumean orogenesis; and
(3) the Issia type granite was the last to be formed at 2106±78 My.
The pegmatites of the studied area were classified into 4 types (A to D) showing more
or less a zonal distribution around the Issia type granite: A- barren type, B- Be type,
C- zoned Be-Nb-Ta type, and D- zoned Be-Nb-Ta-Li type. The B, C and D type pegmatites
have been correlated to the rare-element class and the LCT family.
The mineralizing fluid is derived from crystallization of the Issia granite. After
substantial crystallization of this granite, residual liquid was initially saturated in water
IV