The study of the geologic history of
Central Nigeria reveals that much of the area is underlain by the rock of
basement complex (Precambrian rock) which lies in the mobile zone between the
West Africa and Congo
craton.
These
rocks consist of migmatite, gneiss, schist belt and meta-sedimentary rock
intruded by series of granite rock of later Precambrian – paleozoic age
(McCurry, 1976).
The
oldest to be recognized include granitite gneiss, which is widely scattered
outcrops and few small bodies of diorites rocks while the rest of the basement
complexes contain – migmatite, granite gneiss and granite all are members of
single orogenic cycle.
Migmatite
and granite are considered to have been formed largely from pre-existing gneiss
by processes of granitization.
The
older granite include varieties of transitionals into granite gneiss thought to
be a replacement origin and intrusive granite which ranges from the
characteristics coarse grained porphyritic types, containing biotite and
horneblend to fine grained muscovite biotite granite.
However,
the dominant foliation trend in the basement and the direction of elongation of
many granite masses is N-S, parallel to the trend in basement areas and further
to west.
Radioactive
age determinations have suggested a lower Paleozoic /pan-African for the older
granite orogeny.
Geologically,
the area is dominated by the younger granite a series of non-orogenic intrusive
and associated acid volcanoes.
The
younger granite has recently been shown to be Jurassic in age.
A
period of erosion followed by emplacement of the younger granite resulting in
the formation of the major morphological units of the area – Nassarawa and
surrounding Benue – Abuja – Jos Plateau plains.
Finally
metamorphism occurs during Eburean and pan-African event (Ogezi 1982).
RELATED INFORMATIONS
RELATED INFORMATIONS