Abstract
All previous models of evolution of the Kazaure Schist Belt (KZSB) invoked a simple ensialic mechanism in the context of Pan-African deformation which led to the formation of a marginal back-arc basin floored by continental materials that accepted sediments. The closure of these basins in Pan-African times led to the deformation and metamorphism of the sediment and reactivation of older sediments. Taking into account the presence of Banded Iron Formations (BIFs), metavolcanics and the Kalangai-Zungeru-Ifewara (KZI) fault in the belt, a new model of its evolution is proposed. The new model of evolution of the KZSB considers the evolution of the belt by invoking a simple ensialic mechanism under extensional and compressional regimes, in the context of both Eburnean and Pan-African deformations, as well as Pan-African intrusion of calc-alkaline granites and volcanics. It is effective in explaining the occurrence of BIF, quartzites, conglomerates, and Pan-African granitoids in the belt; and emphasizes the presence of the KZI fault in the evolution of the Kazaure belt. The study led to the conclusion that the belt has formed through ensialic processes, and an evaluation of previous data suggested in previous works is consistent with the new view that the KZSB may represent remnants of Paleoproterozoic cover rocks infolded within an Archaean migmatite-gneiss complex during an Eburnean event, and become reactivated during the Neoproterozoic Pan-African event. KEY WORDS : Evolution, Ensialic, Back-arc basin, Pan-African, Eburnean.
Highlights
The polycyclic Nigerian basement terrain consists of Archaean, Eburnean as well as Pan-African granitic and metamorphic rocks into which are folded discontinuous N-S schist belts (Ajibade, 1976; Ekwueme and Kroner, 1994; Dada, 1998; Dada et al, 1993; Danbatta, 1991)
This paper reviews some of these earlier arguments published to date concerning the evolution of the Kazaure Schist Belt (KZSB), bearing in mind the recent work by Danbatta (1999;2003b) and Aliyu (2006) which clearly demonstrated the occurrence of Banded Iron Formations (BIFs) in the belt, as well as the models of evolution earlier proposed for belts with similar BIFs occurrence
All the previous models of evolution of the KZSB argued that its evolution is probably related to ensialic graben-like structures formed during the Pan-African late-Proterozoic event (McCurry, 1971; Turner, 1983; Ajibade et al, 1987; Danbatta, 2003a)
Summary
The polycyclic Nigerian basement terrain consists of Archaean, Eburnean as well as Pan-African granitic and metamorphic rocks into which are folded discontinuous N-S schist belts (Ajibade, 1976; Ekwueme and Kroner, 1994; Dada, 1998; Dada et al, 1993; Danbatta, 1991). Ajibade et al (1987) reviewed the nature of the early Proterozoic Eburnean event in Nigeria which clearly indicates the importance and involvement of the Eburnean event in the evolution of the Nigerian Basement According to these authors, the Eburnean event was accompanied by sedimentation, deformation, as well as metamorphism and syntectonic igneous activity. The geology, structures, metamorphic history and mineralization of the KZSB have been summarized in a number of reports and papers, such as those of Morton (1967), Turner and Web (1974), Aderotoye (1977), Turner (1983), Ajibade et al (1987), Danbatta (1999; 2001; 2002; 2003a) and Ibrahim (2002) These workers have shown that the belt consists of metasediments, metavolcanics and banded ironformations that are intruded by Pan-African Older Granites. This paper reviews some of these earlier arguments published to date concerning the evolution of the KZSB, bearing in mind the recent work by Danbatta (1999;2003b) and Aliyu (2006) which clearly demonstrated the occurrence of BIFs in the belt, as well as the models of evolution earlier proposed for belts with similar BIFs occurrence
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