2 GENERATIONS OF BIRIMIAN (PALEOPROTEROZOIC) VOLCANIC BELTS IN NORTHEASTERN COTE-DIVOIRE (WEST-AFRICA) - CONSEQUENCES FOR THE BIRIMIAN CONTROVERSY

U-Pb ages have been measured on zircon, monazite and titanite from gne iss, granitoids and rhyolite of the Paleoproterozoic Birimian/Eburnean province in the northern Haute Comoe area, northeastern Cote d'Ivoire , West Africa. Dating reveals that two distinct generations of Birimia n volcanic belt terranes (Tehini belt in the east, Ouango Fitini belt in the west), separated in age by a 50 m.y. time span, occur proximal to each other in the Haute Comoe North area, at the Ouango Fitini shea r zone. This sinistral NNE-trending high-strain zone seemingly represe nts a regionally important, several hundred kilometers long lineament on the Man shield dividing the Paleoproterozoic Birimian/Ebumean provi nce, seen up to now as a single entity, into an eastern and a western subprovince. The eastern subprovince, which covers Ghana, eastern Cote d'Ivoire and probably many parts of Burkina Faso, typically displays similar to 2185-2150 Ma belt volcanism and coeval belt plutonism. Evid ence for 2100 Ma extrusive volcanism is absent. The western subprovinc e (e.g. central Cote d'Ivoire, western Mall, and probably Guinea) is c haracterized by younger, similar to 2105 Ma old volcanic belts and coe val belt plutons. Supracrustal and intrusive rocks of the 2185-2150 Ma time span are at least locally present as various gneisses which prev iously had been termed 'Dabakalian'. A granodioritic biotite gneiss in the western gneiss-granitoid terrane of the Haute Comoe area (=wester n subprovince), resembling 'Dabakalian' gneisses further south, gives a crystallization age of 2152 +/- 2 Ma, identical to the age of a belt pluton in the Tehini volcanic belt (2152 +/- 3 Ma). This suggests tha t those greenschist-facies supracrustal rocks originally termed 'Birim ian' in Ghana by Kitson (1918) are coeval with gneisses in Cote d'Ivoi re termed 'Dabakalian' by Lemoine (1988). Consequently, the invoked 'B urkinian' deformation event, which was assumed to separate Dabakalian basement and Birimian supracrustal rocks, cannot exist. Rather, Birimi an rocks of the eastern subprovince may be correlative with protoliths of the higher-metamorphic Dabakalian rocks present in the western sub province. The term 'Bandamian' is suggested to refer to the 2105 Ma ol d suite of supracrustal rocks of the western subprovince, the term 'Bi rimian' being restricted to the 2185-2150 Ma old volcanic/volcaniclast ic rock suite of the eastern subprovince (Ghana). If the Birimian/Ebum ean province on the Man shield consists of two different-aged subprovi nces, the relative scarcity of economic gold deposits in central Cote d'Ivoire, as compared to Ghana, could not only be a function of undere xploration of the area, but also of different geological processes hav ing formed the terranes of the (older) eastern and the (younger) weste rn subprovince.