THE KIGOM PERALKALINE GRANITE PLUTON OF THE NIGERIAN YOUNGER GRANITE SUITE

J. I. OMADA- Kogi State Polytechnic, Lokoja

R. F. MARTINS - Kogi State Polytechnic, Lokoja and

S. I. ABAA - Kogi State Polytechnic, Lokoja, Nigeria.

ABSTRACT

The kigom granites in central Nigeria are alkali amphibole bearing and peralkaline in nature. They are hypersolvus in character and contain mesoperthite in which the albite (Or_1-2) and microcline are present in approximately equal proportions. The albite is fully ordered while K-rich feldspar is dominantly microcline. The extreme compositions of these feldspars suggests effective crystallization and ordering by hydrothermal fluids at lower than 300⁰C. Geochemical data suggest that the fluid involved in the metasomatism was peralkaline in composition and resulted in the enrichment of Nb, Y, and Th, in microgranite, and of Rb, Zn, Li, Sn, and F in the amphibole-bearing units suggesting that the granites underwent long duration of rock-fluid interaction in a peralkaline environment.

Keywords: Kigom, Peralkaline granite, Mesoperthite, Arfvedsonite, Riebeckite,

 

CHARACTERISTICS OF PYROXENES IN THE MAFIC-ULTRAMAFIC ROCKS OF THE UBO MARBLE AREA

F.U. ASHIDI

Department of Applied Geology,  The Federal University of Technology, Akure, Nigeria

ABSTRACT

Pyroxene crystals of a dolerite, gabbro and pyroxenite that intruded in the Ubo marble area have been analysed on the basis of 4 cations and 6 oxygen anions using conventional electron microprobe coupled with a scanning electron microscope. The results show that SiO₂ in the pyroxenite (51.43–52.52%) was slightly higher than that of the gabbro (48.32-50.83%) and that of the dolerite (47.83-48.95%) due to disilication of dolerite and gabbro liquids. The magnesium content of the pyroxenite (12.29-12.95%) is relatively higher than that of the gabbro (9.95.12.31) and dolerite (4.72-6.33%)because of the more primitive nature of the pyroxenite. ‘Others’ in the pyroxenites (Cr. Ni Ba, Zr, Ti, Al) were more abundant in the gabbro (8.38-13.92) and dolerite (5.96-6.98) than that of the pyroxenite (2.45-4.51) which was probably due to crystallization modes of the different rocks.

The CaO content of all pyroxenes was (21.99-24.43) which appears to be on the high side when compared to calcic pyroxenes from several diverse bulk compositions. The high abundant CaO enhanced a Wo-content of    (41.43-49.36) and Xca=Ca/(Ca+Mg) (0.57-0.78) suggesting an excess of Xca = (0.02-0.23).

The intergrowth of amphiboles with the pyroxenes is thought either due to exsolution-hydration process of genetic solid solution or due to both. When cation exchange and site occupation characteristics of the pyroxenes are investigated, high concentration of Al^vi,. AI/Si, and Ti/AL implied high pressure/temperature crystallization conditions under bimodal or tholeiitic-alkaline transition magmatism in an island arc environment.

Key words: Pyroxenite Ultramafic amphibole Island arcs.

 

PETROGENESIS OF SCHISTS IN SOUTHEAST LOKOJA, CENTRAL NIGERIA

BARTH N. EKWUEME

Department of Geology, University of Calabar, Calabar.

ABSTRACT

Schists in southeast Lokoja, central Nigeria are enriched in Si0₂ and AI₂0₃. Cr, Ni and Tio₂ are also relatively high in these rocks. The chemical compositions of the schists indicate that they were derived from a shale-greywacke sequence of sedimentary rocks. As a result, they have high Ti0₂/Al₂0₃ and variable K₂0/ Na₂0 ratios. The grey wackes had a granodioritic provenance. The high Ti0₂ and Ni content of these metasediments suggest that mafic debris were possibly mixed in their source- rocks. The schists are products of metamorphism of immature sediments which were deposited in an intracratonic extensional basin. Available geochronological data indicate that most intensive reworking of these sedimentary rocks occurred ca. 687±13 Ma ago during the Pan African orogency. Earlier metamorphism of the sediments could have occurred ca. 1315 Ma ago during the Kibaran orogeny.

Keywords:  Lokoja, shale-greywacke, immature-sediments, Pan-African, Kibaran

 

SEISMIC REFRACTION INVESTIGATION OF GROUNDWATER POTENTIAL IN PARTS OF THE OBAN MASSIF, SOUTH-EASTERN NIGERIA

BY

A. M. GEORGE and E. E. OKWUEZE

Department of  Physics, University of Calabar, Calabar.

ABSTRACT

A seismic refraction survey was conducted in parts of the Akampka Basement Region of the Oban Massif, South-Eastern Nigeria, using a portable MOD. S79 3- channel digital type signal enhancement seismograph. The objectives were to determine the depth to the water table, the thickness of the saturated overburden, and the depth to basement, for purposes of groundwater development.

The result showed that for the three selected areas, the average depth to the basement was 16.4m, the average aquifer thickness was 10.6m, and the average velocities of 492m/s, 969m/s, 1811m/s and 3759m/s for the first, second, saturated aquifer and bedrock respectively were obtained. The mean depth to the water table was determined to be 8.7m at Aiyebam 10.1m at Awi and 1.7m at Mbarakom. There was a good correlation between seismic interpretation and borehole lithologic section within the study area. With a considerable saturated thickness, areas of good potential aquifers for groundwater development abound in the study area.

KeyWords: Seismic refraction, groundwater development, basement, Oban Massif, South-eastern Nigeria.

 

GEOPHYSICAL INVESTIGATION OF MARBLE OCCURRENCE IN TAKALAFIA AREA, AROUND ABUJA, CENTRAL NIGERIA

BY

Ojo, J.S.^*, Olorunfemi,M.O.^**, Folami,S.L.^*, Omosuyi,G.O.^*,

Abiola,F.J.^*** and Enikanselu,P.I.^*

^* Department of Applied Geophysics, Federal University of         Technology, Akure.

^** Department of Geology, Obafemi Awolowo University, Ile-Ife.

^*** Department of Applied Geology, Federal University Of Technology, Akure.

ABSTRACT

Outcrops of marble occur in Takalafia environs, south of  Abuja, Central Nigeria. In an attempt to determine the lateral and depth extent of the marble deposit, a geophysical investigation involving electrical resistivity and magnetic methods was carried out. The horizontal profiling and vertical depth sounding techniques were employed.

The marble deposit is characterised by both local resistivity highs (in the range of 20-61 ohm-m within an immediate background of less than 10 ohm-m and low magnetic effect of less than 800 gammas. The outline of the marble deposit based on the above characteristic has an approximately NE-SW trend with a lateral and width extent of about 400m and 40m, respectively. The deposit has a southwesterly plunge. The outline of the deposit and its plunge direction were confirmed by drilling from which borehole logs show marble thicknesses of 1.3-2.7m at the edges and 16.0 and 19.6m within the marble outlined zone.

KeyWords:  Marble, Abuja, geophysical investigation, Plunge.

 

COMPOSITION FEATURES AND INDUSTRIAL APPRALSAL OF THE BABA ODE TALC OCCURRENCE, SOUTH WESTERN NIGERIA

BY

Olubenga A. Okunlola. Olufemi Ogedengbe and Akin Ojutalayo

Geological Survey of Nigeria P.M.B 5008, Ibadan.

ABSTRACT

The Baba Ode talc with a preliminary quantitative estimation of 3 million tons, occurs in close association with a mafic complex. This complex is surrounded by a series of compositionally variable gneisses, syenites, phillytes and mica schists, granites and coarse pegmatites all of the Iseyin-Oyan schist belt.

This study aims at assessing the petrographic, chemical and physical composition of the talc body in order to appraise its industrial suitability.

Two petrographic varieties, a white talcose, and a fibrous light grayish tremolitic variety characterize the body. X- ray and petrographic studies show that mineralogically they comprise mainly of talc, tremolite and chlorite with subordinate quartz and muscovite. Chemical analysis of representative samples using Atomic Absorption Spectrometer (AAS) instrumentation methods show that the tremolitic variety is higher in Si₂0 (53.97%) and Al₂0₃. (1.9%) than in the talcose. Fe (t) as Fe₂0₃ (4.35%) and Ca0 (1.7%) content in the two varieties are non-variable. While Mg0 values in the talcose (33.25%) is higher than in the tremolitic type (31.39%). Concentration of Ti0₂, Mn0₂, Na0 and P₂0₅ for both varieties do not exceed 0.25%.

Firing characteristics reveal an average loss on ignition (L.O.I) of 4.21% for the two types. Linear shrinkage (L.S.V) average 1.35% while average water absorption capacity is 4.1%. A flat to gently undulating topographic configuration and easy accessibility enhance the mineability of body. The talc body therefore with some beneficiation will be useful in paper, paint, roofing and ceramic manufacturing.

Key words: Talc occurrence, petrographic, chemical, industrial.

 

THE STRUCTURAL FRAMEWORK UNDERLYING THE METAMORPHIC EVOLUTION OF THE KAZAURE SCHIST BELT, NW NIGERIA

U. A. DANBATTA

Department of Geology, Ahmadu Bello University, Zaria, Nigeria.

ABSTRACT

The structural framework underlying the metamorphic aspect of the various rocks in Kazaure schist belt (KZSB) was studied. The KZSB consists of metasediments and metavolcanics that are bounded by Older Granites and gneisses. Detailed structural analysis of the Kazaure schist belt revealed the occurrence of structures that resulted from ductile as well as brittle failure.

On outcrop scale, isoclinal, open to tight, overturned and upright folds are observed in the study area. The rocks of the Kazaure schist belt have experienced a minimum of two major ductile deformational events. The first of which involved the development of a NNE-SSW trending S₁ schistosity and recumbent isoclinal folds (F₁). The second event formed nearly upright isoclinal folds with gently to moderately North plunging fold hinges. Evidence for brittle deformation is also recognized within the Kazaure rocks, throughout the area there are numerous fractures, joints and faults characterised by steepply dipping NE-SW and NW- SE trends. The study of microscopic texture domains of the rocks has allowed the identification of two periods of apparently prograde metamorphic recrystallisation (M₁ and M₂) and one retrograde period (M₃). The metamorphic mineral assemblages show evidence of being either syn-D₁, and syn or post-D₂ related to some plastic style of folding.

Keywords: Schist belt, deformation, metamorphism, texture,  recrystallisation

METAL CONTAMINATION AT DUMP SITES IN MAKURDI, NIGERIA

A. I. CHRISTOPHER- Department of Geology, College of Advanced and Professional Studies, Makurdi, Nigeria.

ANGITSO I. JULIUS -  Department of Geology, College of Advanced and Professional Studies, Makurdi, Nigeria. and TERNA NYIATAGHER - Department of Chemistry, College of Advanced and Professional Studies, Makurdi, Nigeria.

ABSTRACT

This study has focused on the investigation of metal contamination by refuse dumps in Makurdi, Nigeria. Soil samples were collected from 17 dump sites and also from a forest to serve as control. Samples were pretreated, digested by aqua regia and the resulting solution analyzed for Fe, Zn, Cu, Pb and Cd using atomic absorption spectrophotometer (AAS). Result shows that the range of iron was 120 –440ppm, zinc 100-260ppm; copper16-201ppm; lead 10-115ppm and cadmium 2-30ppm; in soil from refuse dump sites while forest soil has a range of 120-300ppm for iron, 25 –150ppm for zinc, 20-50ppm for copper, 7-31ppm for lead and 0.5-3.5ppm for cadmium. The significant difference between result obtained for refuse dump sites and the forest soil indicates that refuse dump sites most probably represent point sources of metal contamination to nearby environment. This study also examined metal mobility with 0.1M HCI solution. Result shows that extraction rates (mobility) were in the order Zn>Cd>Cu>Pd> Fe which may be due to differences in geochemical behaviour of metals in the soil. Finally the concept of pollution index (Pl) of soils was applied to determine the extent of multi-element contamination caused by refuse dumps.

Keywords: Extraction rate, Makurdi, metal contamination, pollution index, refuse dumps.                   

 

PROCESS TEST WORK FOR THE RECOVERY OF TANTALITE – COLUMBITE CONCENTRATES FROM RARE METAL BEARING PEGMATITES OF NASSARAWA AREA, CENTRAL NIGERIA

Olugbenga A. Okunlola

Department of Geology,  University of Ibadan,  Ibadan, Nigeria

P.A. King

CSMA Redruth,  TR15 3SE   United Kingdom

ABSTRACT

The Nassarawa Pegmatoids which intrude gneisses, schists and metabasites occur in the northeastern part of half – degree sheet 209. The study aims at elevating the knowledge of economic potentials of Ta – Nb mineralization in the area and enhancing the recovery and extraction percentage of the Ta – Nb concentrates in the weathered (eluvial) and whole rock occurrences.

Ten samples of both the alluvial and whole rock pegmatoids were studied. 10kg of the weathered eluvial samples were prepared and subjected to gravity concentration by panning, wilfy laboratory shaking table and a Mozley laboratory separator before being analysed.

Result show that the recovery of Ta and Nb in the – 2.0mm fractions for eluvial samples was 33. 4% and 28.3% at the combined concentrate grade of 12.2% Ta₂0₅ and 5.89% of Nb₂0₅.

A further 13.2% of Nb₂0₅ and 11.3% of Ta₂0₅ reported to + 2.0mm panned concentrate grade of 2,400 pmm Nb and 5000 ppmm Ta. Back calculated grades of Nb₂0₅ and Ta₂0₅ were 77pmm and 190ppm respectively. The whole rock gave combined concentrate at 23.5% Nb₂0₅ and 31.5% Ta₂0₅ with recoveries, at 70.6% and 70.5% respectively. The back calculated head grade subjected to gravity processing was 128 ppm Nb₂0₅ and 172ppm Ta₂0₅. This test work results show that the two types of ores can be processed to produce Ta –Nb concentrates at economic grade.

Key words: Pegmatoids, concentrates, elluvial, whole rock, recovery.