African
Journals Online
Global
Journal of Geological Sciences
Volume 1 No. 2, 2003
ABSTRACTS
Factor analysis in
hydrochemical survey
Bassey Edem Ephraim
Department of Geology,
University of Calabar, Calabar.
Abstract
When subjected to factor analysis, the
analytical data of water samples of the Calabar Flank area was transformed into
factor score sets that are considered most consistent with known geological and
environmental processes, and appropriate to the limits of analytical precision.
Factor I reflects geochemical interactions of transported foreign materials
with those occurring within the study area. Factor 2 reflects weathering &
decompositions of rock materials occurring within the study area. Factor 3
reflects the oxidation of sulphide minerals occurring within the study area,
and Factor 4 clearly indicates contributions from atmospherical precipitation.
The present contribution demonstrates that factor analysis statistical
reduction technique compresses bulk geochemical data into factor score groups
that correspond to distinguishable controlling environmental factors.
KEY WORDS: Environmental
Factors, Hydrochemistry, Multivariate Statistics, Factor Analysis, Calabar
Flank
Geochemistry of semipelitic schist of Isanlu area,
south west Nigeria: implication for the geodynamic evolution of the Egbe-Isanlu
schist belt
Samuel
B. Olobaniyi *
Department
of Geology, Federal University of Technology, P.M.B. 65, Minna, Nigeria.
*
Present Address: Department of Geology, Delta State University, P.M.B. 1,
Abraka, Delta State, Nigeria.
Abstract
Field and geochemical studies carried out on
the semipelitic quartz-mica schist of Isanlu area, SW Nigeria have been used to
speculate on the geodynamic activity prevalent in the Egbe-Isanlu palaeobasin
at the time its sediment was deposited. Basement rock exposures in the
Egbe-Isanlu schist belt are dominated by metasedimentary rocks, chiefly,
quartz-mica schist with small occurrences of quartzite, marble and silicate
facies iron-formation. These metasedimentary rocks are interbanded with
metaigneous rocks such as talc schist and amphibolite, all of which are
intruded in places by granitoids. Chemical data on major and trace elements of
the sheared and unsheared varieties of quartz – mica schist from the Isanlu
area, reveal a composition comparable to that of semipelitic metasediment.
However, the sheared variety shows elevated values of Na2O, MnO and
Nb, and depleted mean values of FeO and MgO relative to the composition of
normal metasediments. This enrichment – depletion signature is probably a
consequence of the movement of metamorphic remobilised fluids along these shear
zones during the Pan-African or earlier events. A further geochemical
characterisation of the rock indicates that its protolith was an immature
sub-greywacke to greywacke-type sediment derived from a predominantly granitic
provenance. This immature nature of the protolith sediment suggests rapid
subsidence of the basin during its genesis, and/or tectonic instability in the
surrounding environment from which the sediment was derived. Nonetheless, field
observations indicate the absence of typical deep-water sediments and a lack of
regional proximal-distal facies variation suggesting a limited depth and width
for the basin. The presence of shallow, stable shelf-type sediments such as
carbonates and iron-formation (some of which contain carbonaceous material)
suggests a change in tectonic regime at some point in the evolution of the
basin from a rapidly sinking, to a stable shallow basin.
KEY
WORDS: Geochemical studies, Semipelitic
schist, Geodynamic activities, Rapidly sinking basin
Spectral analysis and Hilbert transform of aeromagnetic data over the
upper Benue trough, Nigeria.
A. Nur, C.. O. Ofoegbu and
K. M., Onuoha
Department of Geology,
Federal University of Technology. Yola, Nigeria.
Abstract
Two-dimensional spectral analysis and Hibert
transformation of aeromagnetic data over the Upper Benue trough were carried
out in order to estimate the depths to magnetic sources and also delineate the
major structural patterns in the study area. The analysis conducted indicates a
two-depth source model. The deeper magnetic sources depth of up to 3328m and
this represents the sedimentary cover in the study area. The highest depth to the
shallower magnetic source model is 830m and represents intrusive/extrusive
bodies within the tectonic evolution and the preliminary assessment of the
hydrocarbon generation and maturation prospects of the Upper Benue Trough.
Keywords: Upper Benue trough, Fourier Transform, Hilbert
Transform, sediment thickness and Crustal Structure
Geochemistry of
crystalline basement rocks SW Ugep, Nigeria
Barth
N. Ekwueme
Department of Geology,
University of Calabar P. O. Box 3651. Calabar, Nigeria.
Abstract
Geochemical data on low-grade metasedimentary
phyllites and schists of SW Ugep show that they were derived from predominantly
pelitic parent rocks. They form a supracrustal cover on an orthogneiss of
granitic composition. The metasediments are enriched in Si02, Al203
and Zr but improverished in Ni. Intrusion of pegmatite was accompanied by boron
metasomatism and tourmalinization. This, as well as, the unconformable contact
of the basement rocks with calcareous sandstone of Cretaceous age, may have
raised the Na20, Si02, Ca0 and Mg0 contents of some
outcrops. The Ti02, Al203 values (0.033 to
0.144) confirm that the metasediments were derived from a parent rock rich in
quartz and clay. A dark- coloured garnet-mica schist has a composition of
metagreywacke. The first episode of calc-alkaline magmatism in the area shows
the emplacement of the peraluminous orthogneiss whilst the last episode
indicates the intrusion of the granodiorite. Rocks in SW Ugep area correlate
well in both petrography and geochemistry with those of Uwet area in the south.
This confirms earlier studies, which indicated that metasedimentary schists
occur in the Oban massif of southeast Nigeria and that metamorphism in the area
increased in grade from upper greenschist facies in the west to upper amphibolite
and locally granulite facies in the east.
Key Words: Ugep,
metasediments, orthogneiss, metasomatism.
Petrology of
granulite facies rocks in Ukwortung area of Obudu Plateau, southeastern Nigeria
E.E. Ukwang, B. N. Ekwueme and R. J. Horsley
Department of Geology,
University of Calabar, Nigeria.
Abstract
Rocks of the Ukwortung
area of Obudu, southeastern Nigeria consist of pyroxene –biotite –,
garnet-biotite-gneisses and meta-utramafite. These rocks were intruded by
various granites and pegmatites during the pan-African thermotectonic event.
The presence of hypersthene, plagioclase (An38-46), hornblende and
antiperthitic intergrowths in the rocks of Ukwortung indicate uppermost
amphibolite to granulite facies metamorphic conditions were attained. This high
–grade metamorphism was followed by retrogression to amphibolite facies grade.
Ceramic qualities of industrial clay deposits
at Vimtim in Mubi, northeastern Nigeria
E. E. Ntekim
Department of
Geology, Federal University of Technology, Yola.
Abstract
The possibility of using the extensive clay
deposit at Vimtim in Mubi area, northeastern Nigeria for coarse ceramic
manufacture was investigated. Relevant ceramic properties of the clays have
been determined and their suitability is satisfactory. Results of the
assessment reveal clays that are fine-grained (85.6-96% < 2μm), plastic
(36-53% PI), and moderately dense (1200-1720 g/m3). Mean values of
other industrial properties include 6.9% shrinkage, 6.8% porosity, 34.5N/m3
mechanical strength, 7.7% LOI, reddish yellow firing colours. Their average
chemical composition includes 70.5% SiO2, 17.04% Al2O3,
2.58% Total Fe oxides, 0.26% Na2O, 0.92% K2O, 0.89% MgO
and appreciable kaolinite content. These parameters suggest good clay raw
materials for the manufacture of coarse ceramic products like earthenware,
kitchenware, ornamental wares and scientific wares.
Key words: Clay deposit,
Vimtim - Mubi, Nigeria, Ceramic qualities.
Seismic characterisation of subsurface
structural features of parts of “Richy” field, offshore Niger Delta, Nigeria
P. A. Enikanselu and G. O.
Omosuyi
Department of Apply
Geophysics, Federal University of Technology Akure
Abstract
A total of thirty-four migrated 2D seismic
reflection lines and two composite well logs have been interpreted with a view
to unravel the subsurface geological structural setting aimed at delineating
probable hydrocarbon potentials around “Richy” field, east of Niger delta
basin, Nigeria. The interpretation procedure includes horizon identification,
fault mapping, timing of horizons at selected shot points, posting of times,
time-depth conversion and contouring. Both the isochron and isodepth (isobath)
maps revealed an elongated fault-assisted anticlinal structure trending NE-SW
direction with a growth fault in the southwestern part. This suggests that the
features can form good hydrocarbon traps. Locations M1 and M2 situated around
the crest of the anticlines are recommended drilling points. The study has
demonstrated the relevance of structural control studies in the location of
wells for hydrocarbon exploitation.
Key words: structure, horizon, anticline, isobath and isochron
Hydrogeological and geotechnical study of
Bauchi and environs, Northeast Nigeria
G. I. Obiefuna and A. Nur
Department of Geology,
Federal University of Technology, Yola, Nigeria.
Abstract
Hydrogeological and geotechnical investigations
around Bauchi area have been carried out. The results of the investigations
indicate the occurrence of two aquifer units namely; the unconsolidated weathered
overburden aquifer unit and the fractured basement aquifer unit. The hydraulic
parameters of the aquifer units indicate a hydraulic conductivity value that
ranging between 0.93 x 10-3 m/s to 8.93 x 10-3 m/s and a
mean value of 3.47 x 10-3 m/s. An average linear groundwater
velocity of 3.80 m/yr and a specific discharge of about 1.71 m/yr were
recorded. The geotechnical investigation indicates a mean plasticity index of
17.2%; mean optimum moisture content of 9.30% and a mean maximum dry density of
2.5 g/cm3. The shear strength test indicated a mean cohesion value
of 0.25 kg/m2 in a mean angle of internal friction of 30.1o.
From the results of this study recommendations that will serve as useful guide
in erosion control and groundwater prospecting in the area were made.
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