GEOLOGY AND GEOCHEMISTRY OF URANIUM MINERALIZATION IN MIKA N. E. NIGERIA
GEOLOGY AND GEOCHEMISTRY OF URANIUM MINERALIZATION IN MIKA N. E. NIGERIA
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Date
1992-09
Authors
IDRIS, ISA FUNTUA
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Abstract
The Mika uranium mineralization is located near Zing in
Taraba State, N.E. Nigeria.
The host rock consists of a sheared Pan-African medium
grained biotite granite which is in places intruded by
rhyolites and siliceous veins. These are criss-cut by
numerous joints, faults and fractures which are filled by
hematized silica.
The ore occurs in two parallel N-S trending shear zones
with the western limb hosting a rhyolite body. Drill
section reveal a subsurface extension of the above. In the
upper limb mineralization consisting of meta-autinite
occurs associated with the rhyolite body. In the lower ore
limb pitchblende and coffinite occur along a set of two
parallel shear surfaces. The pitchblende occurs massive and
as veinlets in hematized rocks in association with
sulphides. The ore body is marked by distinct hydrothermal
alteration zones which feature serlcitization,
si1icification, K-feldspathization, hematization and
kaolinization.
Three hundred rock samples consisting of host rocks and
ores from surface and drill cores each of which was
analysed for 25 elements using Neutron Activation Analysis,
Natural activity counting and Radioisotope X-ray
fluorescence techniques. The elements includes Si, Tl, Al,
Fe, Mn, Mg, Ca, Na, K, P, Sc, V, Cr, Ni , Cu, Zn, As,Se
Rb, Sr, Y, Zr, Mo, Pb and U. The resulting data were
evaluated using multivariate statistical techniques
including principal component analysis.
U, Fe, P, Cu, Zn, Mo and Pb have higher values than the
background values. These elements form distinct dispersion
aureoles around the uranium occurrence which appeared to be
most pronounced on the surface, perhaps owing to weathering
and remobi1ization. Some elements like Na and K are
depleted in the mineralized zone in relation to the
intensity of hydrothermal alteration.
There are two distinct element associations in the ore zone
and host rocks; the Ti20-Mg0-Ca0-K20-Co-Sr -Rb-Zr and
Fe203-P20s-Cu-Zn-Mo-Pb-U. The first which reflects
mineralogy of the host rock forms a large cluster that
includes Fe20a, PzOs, Cu, Zn, Mo, Pb and U in the altered
granites and rhyolites. This is fragmented into the two
associations above in the mineralized rocks. The latter
group, Fe203-P205-Cu-Zn-Mo-Pb-U is a product of
remobi1ization of the former and reflects the mineralogy of
the ores.
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Structures played an important role in the formation of the
Milka mineralization, as channel and or mechanical barrier.
These structures are reactivated lineaments that are
related to regional structures, which have undergone a
prolonged history of geological development and several
periods of activity.
The bimodal magmatism of the Burashika group is postulated
to be related to the uranium mineralization, from the
consistent presence of rhyolite bodies to the
mineralization. The role of the magmatic is most likely
the source of heat and the driving force of the
mineralization fluid and sometimes as well as mechanical
barrier for the fluids leading to the formation of the
mineralization
Description
A thesis submitted to the Postgraduate School, Ahmadu Bello
University, in partial fulfillment of the requirements for
the degree of Ph. D. (Geology).
Department of Geology
Faculty of Science
Ahmadu Bello University
Zaria
September, 1992
Keywords
GEOLOGY,, GEOCHEMISTRY,, MINERALIZATION,, MIKA,,, NIGERIA