Vol 2 - Cont. J. Earth Sci 2

8/9/2019 Vol 2 - Cont. J. Earth Sci 2

1/24

1

Continental J. Earth Sciences 2: 1 - 6, 2007Wilolud Online Journals, 2007.

ECONOMIC POTENTIALS OF THE PEGMATITES OF ERUKU AREA, SOUTHWESTERNNIGERIA.

Adekeye, J. I. D. and Adedoyin, A. D.Department of Geology and Mineral Sciences, University of Ilorin, Nigeria.

ABSTRACTThe close proximity of the pegmatites of Eruku area to the strongly mineralized pegmatitesof Egbe area and lack of published work on those from the former formed the basis of thisresearch. Sub-parallel, steeply-dipping, lenticular/podlike pegmatite bodies occur in theEruku area, southwestern Nigeria. They are emplaced within the late Proterozoic to earlyPaleozoic crystalline basement complex rocks. Some of these pegmatites are mineralizedwhile others are barren. The barren pegmatites are sources of industrial minerals like

feldspar and quartz. The mineralized pegmatites are also sources of feldspar and quartzand, in addition, columbite tantalite, cassiterite, garnet and coloured varieties of tourmaline. Structural features present in the pegmatites include their linear disposition,crude zoning within the rocks and occurrence of some minerals across the contact zone.Available geochemical data indicate that the mineralized pegmatites classify as Li-Be+Tapegmatites. They are genetically related to differentiation and progressive crystallizationof a fertile granitic magma under non-equilibrium conditions during the cooling period,while the barren ones may be products of metamorphism in a high grade metamorphicterrain.

KEYWORDS: Pegmatites, potential, mineralized differentiation, crystallization, petrogenesis.

INTRODUCTIONThe Eruku area, about 140km east of Ilorin, is located west of the Egbe area, which was studied by Jacobsonand Webb (1946) and east of the Osi area, which was also studied by King and de Swardt (1949). The area fallswithin longitudes 5 0 19'E - 5 0 33 'E and 8 0 04 'N - 8 0 12 'N (Fig.1).

There is no published work on the area, yet it shares a common boundary with the well studied Egbe area, whichis known for rare-metal bearing pegmatites. Also, there is an upsurge in demand for precious and semi-preciousminerals due to new trends in technology and fashion. This calls for discovery of more sources to cope with thedemand. These factors formed the basis for carrying out geological and geochemical studies in the area with aview to possibly identifying more mineralized pegmatites. Geological mapping was carried out onscale1:25,000.

The pegmatites were carefully observed, during the course of mapping for their field and mineralogicalcharacteristics with a view to identifying those with high mineralization potentials. Whole rock and mineralsampling was done during the mapping exercise. Thin-section slides were also prepared for petrographicstudies. Carefully selected biotite, muscovite and feldspar samples were pulverized at the workshop of GeologyDepartment, Obafemi Awolowo University, Ile-Ife, Nigeria. The samples were milled to 40. Major oxidesand minor elements were analyzed for through ICP-MS method using LiBO 2 /L 12B4O7 fusion and HCl-HNO 3-HClO 4-HP digestion respectively. The rare earth elements were analyzed for using ICP-ES. All analyses weredone at ACTLABS, Ontario. Canada, through Petroc Services Ltd, No. 10 Alfonso St., Shasha, Ibadan, Nigeria.


2/24

2

Adekeye, J. I. D. and Adedoyin, A. D: Continental J. Earth Sciences 2: 1 - 6, 2007

Although gh detailed petrographic and structural analyses are beyond the scope of this preliminary report, yet abrief petrogenesis of the pegmatites has been proposed based on the available petrographic and structural data.

It is hoped that this report will prove useful in further search for materials in the ceramic, chemical andtechnological industries.

The pegmatitesThe pegmatite bodies in the study area are variable in character: simple, complex, crudely zoned, unzoned,tabular, lenticular, feebly albitized or graphic. Some of them are deeply weathered and their presence onlyregistered by relics of feldspar, rock quartz, muscovite and schorl, lying on the ground while the others are stillemplaced. They cross-cut all rock types in a generally NW-SE direction. Some of them are deformed while theothers are massive. An impressive, relatively undeformed body occurs in the north central part of the study areaand constitutes about 60% of the small hill. Many others are low-lying. The pegmatites vary in sizes betweenless than 1m to 30m in width and 5m to 205m in length. They are either vertical in orientation or dip at highangles.

The bodies exhibit sharp textural and mineralogical changes. They also occur in sub-parallel swarms withoccasional pinch-and-swell structures along their strikes. The swells are known to be loci of mineralization incertain complex rare-metal pegmatites from southwestern Nigeria (Adedoyin, 2005; Adedoyin et al . 2006). Inthe larger bodies, crude border, wall, intermediate, and core zones could be identified. The contact zone is fine-grained while the core is coarse-grained being composed essentially of large crystals of (up to 12cm across)quartz. Many of the pegmatites are dilational. Around their border, xenoliths of the gneisses were found withinthe pegmatites while slender prismatic schorl and muscovite are oriented in oblique manner. The basicmineralogy of the pegmatites appears to be microcline + albite + quartz + muscovite + biotite +garnet.Microcline is the most prominent feldspar. It is pink in colour and measures between


3/24

3


cassiterite occur as disseminated grains between 0.1 1.6 mm in size while tiny, cloudy crystals of beryl werepicked in the north central part of the area.

GeochemistryMajor, trace, and rare earth elements were analyzed for in micas and feldspar. Results of the analyzed samples

and some geochemical ratios are presented in Table 1. Concentration of some major, minor and trace elementsin muscovite and, to some extent feldspar and biotite have proved useful in discriminating the pegmatitedeposits. This is a preliminary result and therefore, our conclusions are regarded as tentative in the light of limited analytical results. A sharp contrast exists between elemental conntrations in the samples, whether traceor rare earth elements. Rb and Nb are fairly enriched in the micas while the Sn content is only fairly enriched inmuscovite. A close relationship exists between Nb and Ta. About 9% of Ta occurs in every columbite tantaliteassociation. Although tiny impure crystals of beryl were picked, yet beryllium content is unimpressive. TheK/Rb ratios are low while the K/Ba and K/Sr ratios are generally higher in the micas (Table 1).

DISCUSSIONIn the past, efforts in the search for mineralized pegmatites were concentrated within the NE- SW pegmatitebelt, but in recent times, efforts are now directed at places outside the belt. This has yielded results as newdeposits have been discovered away from the belt (e.g. Ekwueme and Matheis, 1995; Garba, 2003). However,Eruku area is sandwiched between Jacobson and Webbs (1946) Egbe area and King and de Swardts (1949) Osiarea. Jacobson and Webb (1946) reported occurrence of mineralized pegmatites but


4/24

4


King and de Swardt(1949) observed none. The present study concentrates on this horizon that lies betweenmineralized and barren zones.

This investigation shows that the pegmatites in the Eruku area could be classified into two: The first classcomprises the microcline + quartz + muscovite + biotite bearing bodies. These are barren. Some of them

are only sources of large crystals of microcline and quartz. The second class is comprised of microcline + quartz+ muscovite + schorl + garnet + cassiterite bearing pegmatites. They are mineralized. The barren pegmatitesare more abundant than the mineralized types.

The pegmatites cut various rock types in the area. Their linear and dilational dispositions indicate forcefulemplacement into pre-existing zones of weakness within Older Basement units under active tensional strainconditions. Field evidences e.g. occurrence of xenoliths of country rocks in them point to their magmatic origin.

They have possibly been formed from differentiation of magma of a fertile granite. The zoning as well as themineralogical and textural variations between adjacent zones within the pegmatite deposits is related toprogressive crystallization from the border to the core. These differences are due to fractionation andprogressive reactions between remnant crystals and incoming fluids. According to Cameron et al (1949), thesereactions are best attained under non-equilibrium conditions. The fractionation is supported by the low K/Rb buthigh K/Ba and R/Sr ratios

Differences in thermal states between the host rocks and the pegmatites are indicated by the fine-grained natureof the contact zone. This phenomenon develops when a magma forced into relatively cold country rocks ischilled by the lower temperature of the country rocks. Existence of black tourmaline in oblique orientationacross the borders indicates that the emplacement was accompanied by mobility from a


5/24

5


generation of ascending fluids. The barren pegmatites are older than the mineralized types, being cut by thelatter. Kinnard (1984) ascribed upper Proterozoic and Palaeozoic times to barren and mineralized pegmatites,respectively. He also related the earliest pegmatites to shallow-depth plate collision granitoids and the latter

ones to orogenic/anorogenic Older Granites. The mineralized pegmatites in the Eruku area thus appear to begenetically related to the late stage emplacement of the granites. The high K/Ba and Rb/Sr but low K/Rb ratiosin the muscovite species also point to a granitic origin (Garba, 2003).

Concentrations of trace elements in white micas have on many cases proved useful in appraising the economicpotentials of mineralized pegmantites (Gordiyenko, 1971; Garliski, et al , 1977; Kuster, 1990). Results of geochemical analysis have been applied to discriminate barren and mineralized pegmatites (e.g Matheis andCaen-VAchette, 1983; Kuster, 1990; Oyarzabal, 2004). K/Cs vs Rb and K/Rb vs Rb/Sr discriminating diagrams(Fig.2 and 3) show that the mineralized pegmatites are Li-Be+Ta pegmatites. Also compared to somemineralized pegmatites e.g. Kushaka and Magami areas (Garba, 2003), the mineralized pegmatites are moreenriched in columbite tantalite mineral as observed from the results of geochemical analyses. Adedoyin et al (2006) are of the opinion that presence of schorls on the surface of a pegmatitic deposit is an indication of itshigh potential for mineralization.

CONCLUSIONMineralized and barren pegmatites occur in the Eruku area. The barren ones are simple in mineralogy andcharacter and are sources of only ceramic and industrial minerals. The mineralized pegmatites are complex andcontain some minerals such as columbite tantalite, beryl, tourmaline, cassiterite and garnet. Massive, cleanquartz veins occur in the northwestern part of the area and are being worked by artisan miners. The purity of thequartz veins makes them favourable sources of raw materials for glass, soap and scouring powder industries.

ACKNOWLEDGEMENTSThe authors thank Mr. Sunday Abiola of Ekiti Local Government Secretariat, Araromi-Opin, Kwara State,Nigeria, for providing free accommodation during the fieldwork. Mrs. Felicia Omidiran of The Lord is goodComputer Centre, Offa Rd/Lajorin, Ilorin, Nigeria, is also thanked for carefully typing the manuscript.

REFERENCESAdedoyin, A. D. (2005): Aspects of the Geochemistry of Pegmatites from selected localities from southwesternNigeria. Unpubl. M. Sc. Thesis, Univ. Ilorin.

Adedoyin, A. D., Adekeye, J.I.D. and Alao, D. A. (2006): Trace element geochemistry of selected pegmatitesfrom southwestern Nigeria. Nigerian Journal of Pure & Applied Sciences, University of Ilorin. 1:2023-2035.

Cameron, E. N., Jahns, R. H., McNair, A., and Page, L. R. (1949): Internal structure of granitic pegmatites.Econ. Geol. Monogr. 2: 115pp.

Ekwueme, B. N. and Matheis, G. (1995): Geochemistry and Economic value of pegmatites in the PrecambrianBasement Complex of southeastern Nigeria: Magmatism in relation to diverse tectonic settings (R.K. Srivastavaand R. Chandra, Eds., New Delhi, IBH publishing Co. 1:375-392).

Garba, I. (2003): Geochemistry discrimination of newly discovered Rare-metal bearing and Barren Pegmatitesin the Pan-African (600+ 150Ma). B112: B287 B292.

Garliski, M., Perino, E., Gasquez, J., Marquez Zavalia M., and R. Olsina (1977):Geoquimica de feldspatospotasicos y muscovitas como guia de exploracion de pegmatitas graniticas de algunos distritos de la provincialpegmatitica pampeana. Rev. Asoc Geol. Arg. 52:24-32.


6/24

6


Gordiyenko, V. V. (1971): Concentration of Li, Rb and Cs in potash feldspar and muscovite as criteria forassessing the rare metal mineralization in granite pegmatites. Internation Geo Review, 13: 134-142.

Jacobson, R. and Webb, S. (1946): The Pegmatites of Central Nigeria. Geological Survey Bulletin. 17:1-73.

King, B. C. and de Swardt, A.M.J. (1949): The Geology of the Osi Area, Ilorin province. Geological Survey of Nigeria. Bull No. 20.

Kinnaird, J.A. (1984): Contrsating styles of Sn-Nb-Ta-Zn Mineralization in Nigeria. Journal of African EarthSciences, 2: No.2:81-90.

Kuster, D. (1990): Rare-metal pegmatites of Wamba, Central Nigeria Their formation in relation to Late Pan-African granite. Mineralium Deposita 25: 25-33.

Matheis, G. and Caen-Vachette, M. (1983): Rb Sr Isotopic metal-bearing and barren pegmatites in the Pan-African reactivation zone of Nigeria. J. Afri. Earth Sci 1: 35-40

Oyarzabal, J. (2004): Geologica, meneralogia, geoquimica y Petrogenesis de yacimientos pegmatiticas de!Distrito Totoral, Sierra de San Luis, Argentina. Tesis Doctoral UNC. Cordoba, Argentina.

Received for Publication: 01/05/2007Accepted for Publication:

Corresponding Author:Dr. J.I.D. ADEKEYEDepartment of Geology and Mineral Sciences, University of Ilorin, Ilorin, Nigeria.E- mail: [email protected]


7/24

7

Continental J. Earth Sciences 2: 7 - 13, 2007. Wilolud Online Journals, 2007.

GEOCHEMICAL CHARACTERISTICS OF GABBROIC INTRUSIVE BODIES IN THE SHA-KALERI

YOUNGER GRANITE COMPLEX, CENTRAL NIGERIA.

Daspan, R.I, Yakubu, J.A., and Lar, U.A.Department of Geology and Mining, University of Jos, Jos-NIGERIA.

ABSTRACTLarge discrete gabbroic intrusive bodies outcrop within the Tof sub-unit of the Sha-KaleriJurassic Younger Granite Complex, situated at the southwestern end of the JosPlateau.They were sampled and analysed for their major and trace element compositionswith a view to determining their geochemical characteristics and tectonic setting The

gabbroic rocks co-exist with hybrid rocks of composition in-between the gabbros and thegranite porphyry and the extrusive equivalent basaltic rocks. The rocks are composedessentially of plagioclase and hornblende with minor pyroxene (titaniferous augite) andolivine similar to the composition of the co existing basalts of presumably Cenozoic age.The gabbros display enrichment in incompatible elements (Rb, Th, U, K, Nb, and Sr)compared to the Mid Ocean Ridge Basalt (MORB). The relatively wide variation inCaO/TiO 2 ratios (3.35 7.95) of these gabbros is in good agreement with their formationby fractional crystallization process. This is further attested to by their wide variations inincompatible element ratios (Rb/Sr= 0.03-0.32); Zr/Nb=1.03-8.48); Th/U=0.97-1.25) andU/Pb=0.19-0.47). They also present trace element compositions similar to that of theOcean Floor Basalt (OFB) and Jos Plateau Basalts suggesting that they must have beenderived from the same parent mantellic magma.

KEYWORDS : Gabbro,Younger Granites,Basalts,mid-oceanic ridge basalts, Incompatibleelements, ocean ridge basalts.

INTRODUCTIONGabbroic rocks outcrop in a few Jurassic Younger Granite ring complexes in Nigeria (Macleod et al., 1971).They make up a minor part (about 1%) of the complex in which they occur. Occurrences of these gabbroicintrusions have been reported at Kofayi ring complex, northeast of Jos Plateau, at Sara-fier complex, southeastof Jos Plateau and at Sha-Kaleri complex southwest of the Jos Plateau to mention but a few. The Mama gabbros,which form the subject of this investigation, outcrop within the Sha-Kaleri complex where the largest volume of mafic intrusive bodies has been observed. They occur as intrusive or as veined sill-like bodies within the hostgranitic rocks. Hybrid rocks of compositions in-between these two rock types do occur. It is however neitherclear if the gabbros predate other granitic rock units nor it is clear as to their origin vis--vis the overlyingvolcanic equivalent rocks, the Cenozoic basalts. Thus, it is difficult to fix these gabbros in their rightful place asit relates to the evolution of the Jurassic Younger Granite complexes. This paper therefore attempts to determinethe geochemical characteristics and the origin of these gabbros in comparison with their volcanic equivalentbasaltic rocks in the Sha-Kaleri Younger granite complex.

Geology and PetrographySha-Kaleri Younger Granite complex is situated southwest of the Jos Plateau and marks the southern boundaryof the Plateau with the low-lying Paleozoic-Precambrian Basement into which the granites intruded. Thecomplex is the third largest of all the Younger Granite complexes in Nigeria and occupies a superficial area of nearly 400 km 2. It is sub-divided into three distinct minor complexes, which include from north to the south theKaleri, Monguna and Tof sub-complexes ( Figure 1)

The Mama gabbros outcrop within the Tof sub-complex(Figure 1) as several phases of intrusive bodies withinthe granite porphyry. At the contact between these gabbros and granite porphyry, the gabbros are net-veined bythe porphyry parallel to the contact. Hybrid rocks probably formed by the assimilation of the gabbroic xenolithin he granite porphyry magma co-exist.


8/24

8

Daspan, R.I et al : Continental J. Earth Sciences 2: 7 - 13, 2007.

They have poikilitic to subophitic texture but they present similar mineralogical compositions. The onlyvariation is in the proportion of hornblende and plagioclase the principal visible constituent minerals. Otherminerals such as titaniferous augite occur as accessories together with biotite, olivine and iron oxide in thehornblende.

ANALYTICAL TECHNIQUESNine rock samples were crushed and milled to less than 125m powder for geochemical analysis. Only thefollowing major elements (K 2O, MnO, Fe 2O3, CaO, TiO 2) and trace elements (V, Cr, Ni, Co, Cu, Zn, As, Pb, Br,Rb, Sr, Y, Zr, Nb, Mo, Th, U) were analyzed. Other major elements especially SiO 2 were not analyzed for lack of facility. The analysis was carried out using the Energy Dispersive X-Ray Flourescence (ED-XRF) techniqueat the Centre for Energy, Research and Training (CERT), Zaria. For both major and trace element analyses, therock powder was pressed into pellets. The instrument was calibrated using recommended international standardsat each time necessary. The precision and accuracy of the data were lower than 1% for major elements and0.05% for trace elements.

Geochemical ResultsThe major and trace element compositions of the gabbros from the study area are presented in Table 1.

Major elements

In general, the rocks present relatively lower concentrations in CaO, Fe 2O3, K 2O and higher TiO 2 compared totheir equivalent volcanic basaltic rocks of the Jos Plateau. For all the rocks put together, the percentages of K 2Ovary narrowly (0.72-0.99Wt%) as oppose to the relatively wide variations in the other major elements analysed(for example, TiO 2=0.76-2.30Wt%; CaO=5.72 7.61Wt%; Fe 2O3=6.01-7.55 Wt%). On the variation plots of TiO 2 Wt%, MnO Wt% and CaO Wt% versus Fe 2O3 Wt% (Figures 2-4), the rocks define positive correlations.Contrarily in K 2O Wt% and Fe 2O3 Wt% variation diagram (Figure 5 ), the proportions of K 2O Wt % do notseem vary significantly with the increase in that of Fe 2O3Wt%. There is however a wide range of variation intheir CaO/TiO 2 ratios (3.35-7.95).

Trace elementsThe trace element data were displayed in MORB normalized spidergraphs and tectonic discrimination diagrams

of Pearce and Cann, (1973); Winchester and Floyd, (1977); Meschede, (1986) and Pearce, (1975).

In the MORB-normalized spidergraphs, all the rocks display consistent variations in the trace elements, thusexhibiting similar distribution patterns. Generally, the rocks are enriched in incompatible elements (K, Rb, Th,U, Nb, Sr and are slightly depleted in High field Strength elements (Zr, Ti and Y) relative to the Mid OceanicRidge Basalts (MORB). Of note are the significant positive anomalies in Th (100-150 x MORB) and U (200-400 x MORB). In contrast however, samples SG4 and 9 are relatively depleted in Sr as oppose to Y enrichmentin sample SG2 relative to MORB (Figures 6-7).

The gabbros when plotted in the discrimination diagram of Winchester and Floyd, (1977) (Figure 8) fall withinthe domain of sub-alkaline to alkaline fields. They plot in the PMORB field in the tectonic discriminationdiagram of Meschede, (1986) (Figure 9). This is further attested to by exhibiting similar characteristics as OceanFloor Basalts (OFB) in the log Ti (ppm) versus log Cr (ppm) of Pearce, (1975) (Figure 10) and in the Ti (ppm)versus Zr (ppm) diagram of Pearce and Cann, (1973) (Figure 11).

DISCUSSIONThe variations in the content of CaO, TiO 2 and Fe 2O3 will here be used since they control the crystallization of pyroxene and plagioclase, which are the principal constituent minerals in these gabbros. The systematicprogressive increases in the Fe 2O3 either with CaO or TiO 2 and the relatively wide variations of CaO/TiO 2 ratios(3.35 7.95) for all the rocks suggest their formation by fractional crystallization process from the same magmasource. Their relatively significant ranges in the variations of incompatible element ratios (e.g. Rb/Sr=0.03 0.32; Zr/Nb=1.03 8.48; Th/U=0.97 1.25; and U/Pb=0.19 0.47) further support this assertion.

By their characteristic enrichment in incompatible elements relative to compatible elements they are comparableto the co-existing extrusive equivalent basaltic rocks of the Jos Plateau (Lar and Tsalha, 2005). They howeverdiffer from the Jos Plateau basalts by their relatively lower percentages in Fe 2O3 and CaO, and higher tenors inTiO 2. This is understandable only if these gabbros are the products of the differentiation of the same magmafrom which these basalts were also derived ab-initio. Compared to the Mid Oceanic Ridge Basalts (MORB),


9/24

9


they differ by their relative enrichment in the incompatible elements (K, Rb, Th, U, Nb, Sr). The composition of the gabbros in Zr, Nb, Y and TiO 2 is indicative of their alkaline nature (Winchester and Floyd, 1977), which isfurther attested to by their strong positive anomalies in Nb, Th and U. While most of these gabbros display

Zr/Nb ratios between 1.07 and 5.48 suggesting their derivation from sources akin to those of the Ocean Flooralkaline Basalts (OFB), few of them display relatively higher ratios (6.89 8.48) also suggesting an originsimilar to that of the enriched mantle Oceanic Island Basalts (EM OIB). However, these higher Zr/Nb ratios canbe explained either by fractionation of these elements or by the interaction of the slow cooling gabbroic magmawithin the continent.

CONCLUSIONFrom the data presented and the discussions that followed, the following conclusions can be reached;The gabbros display geochemical characteristics identical to that of the extrusive alkaline basalts of Jos Plateausuggesting a derivation from the similar parent magma. They however differ by their relatively lowerconcentrations in Fe 2O3 and CaO, and higher concentrations in TiO 2.

They represent essentially the product of the fractional crystallization of the same parent mantle magma from

where the Basalts of the Jos Plateau were derived.Compared to Mid Oceanic Ridge Basalts (MORB), the gabbros display relative enrichment in incompatible

elements (K, Rb, Th, U, Nb, Sr).

ACKNOWLEDGEMENTWe wish to acknowledge Mr Anzaku Charles Ovyeh and Mr Bulus Azi who helped during the field mappingand sample collection. The centre for energy research and training, Zaria is duly acknowledged for geochemicalanalysis of the samples. Goki Nathan is acknowledged for preparation of maps and figures.

We acknowledged anonymous reviewers for their comments which greatly improved the original quality of thework.

REFERENCESLar, U.A. and Tsalha, M.S. (2005) Geochemical characteristics of the Jos Plateau Basalts, North central Nigeria.Global Journal of Geological Sciences. 3 (2): 187-193.

Macleod, W. N. Turner, D.C. and Wright, E. P. (1971): The Geology of Jos-Plateau, Vo.1 General Geology.Geol. Surv. Of Nigeria. Bull N0. 32.

Meschede, M., (1986): A method of discriminating between different types of Mid-Ocean Ridge Basalts andcontinental tholeiites with the Nb-Zr-Y diagram. Chemical Geology.56:207-217.

Pearce, J. A., (1975): Basalt geochemistry used to investigate past tectonic environments in Cyprus.Tectonophysics. 25:41-67.

Pearce, J. A. and Cann, J.R (1973): Tectonic setting of basic volcanic rocks determined using trace elementsanalyses. Earth Planet. Sci. Lett. 19:290-300.

Winchester, J.A and Floyd, P.A (1977).Geochemical discrimination of different magma series and theirdifferentiation products using immobile elements.Chemical Geology. 20:325-43.

Received for Publication: 12/07/2007Accepted for Publication: 07/09/2007

Corresponding Author:Daspan, R.I.Department of Geology and Mining, University of Jos, Jos-NIGERIA.


10/24

10


#

MONGUNA

TOF

SHA-KALERI

SHARWAI

N

Study area

Rock types

Tertiary & Quaternary Basalts

Arfvedsonite Granite

Rieb-Biotite Granite/Porphyry

Biotite Microgranite

Biotite Granite Rayfield-G typ

Biotite Granite Ngel type

Biotite Granite Jos type

Horn.-Pyrox- Fayalite Granite

Horn. Biotite Granite Porphyry

Late Rhyolite

Early Rhyolite Tuff & Agglom.

Mama Gabbro Dolerite

Undifferentited Basement

LEGENDBOKKOS

Fig. 1 Geological Map of Shakaleri Younger Granite Complex Showing Study Area (After Macleod et al 1971)


11/24

11



12/24

12



13/24

13

Daspan, R.I et al : Continental J. Earth Scieces 2: 7 - 13, 2007.

Table 1:Major (wt.%) and Trace element (ppm) compositions of Mama Gabbros.

Major Elements(wt.%) Trace Elements (ppm)

K2O CaO TiO 2 MnO Fe 2O 3 V Cr Co Ni Cu Zn As Pb Br Rb Sr Y Zr Nb Mo TSG- 1 0.84 6.04 0.76 0.15 6.01 910 589 258 200 120 772 56.3 82 18 31 180 12 60 13.3 7.30 26 22.4 7SG -2 0.99 4.72 1.48 0.10 7.55 802 563 439 145 108 13.6 49.1 70.7 23.1 26 299 40 30 28 9.27 23 18.4 3.

SG -3 0.91 6.30 1.10 0.12 7.21 881 572 370 190 120 73 62.3 88.4 20.1 15 230 13 59 7.00 7.20 21 17 5SG -4 0.72 7.73 2.31 0.08 5.10 987 565 238 201 105 64.7 44.7 63.9 16.2 13 57 13 38 6.96 6.85 26 26.6 3.

SG 5 0.91 6.29 1.05 0.21 7.21 881 572 368 190 119 72.8 62.3 88.4 20.1 15 228 13 59 6.96 8.27 21 16.9 5.9SG -6 0.99 5.72 1.28 0.10 7.00 802 563 542 246 103 186 49.1 70.7 23.1 26 300 30 60 58 8.27 23 30.2 4.SG -7 0.83 7.51 2.00 0.08 6.08 987 565 238 201 225 64.7 44.7 63.9 16.2 13 57 13 48 6.96 7.85 27 26.6 3.SG -8 0.98 7.61 1.19 0.08 7.25 945 684 480 144 115 122 49 71.7 30 54 167 19 41 13.5 6.42 22 17.3 6SG -9 0.84 6.04 0.76 0.15 6.01 945 684 480 144 115 122 49 69.1 16.4 54 167 19 41 13.5 6.40 22 17.3 7.


14/24

14

Continental J. Earth Sciences 2: 14 - 24, 2007. Wilolud Online Journals, 2007.

MATURITY AND PROVENANCE OF THE ALBIAN BIMA SANDSTONE IN WURO-DOLE ANDENVIRONS, YOLA ARM, NIGERIA.

Etobro, A. A. I. and Ejeh, O. I.Department of Geology, Delta State University, P.M.B. 1, Abraka, Nigeria.

ABSTRACTBima Sandstone at Wuro-Dole and environs was studied for its level of maturity andsource area (provenance). In evaluating its textual maturity and provenance, fieldmapping was carried out and representative samples were subjected to physico-chemical and mineralogical analyses. The sandstone consists of some primarysedimentary structures:cross-beddings and ripple marks. Strike measurements of theseprimary structures plotted on current rose diagrams indicated SSE-NNW and NE-SW/NW-SE directions. The Bima Sandstone is averagely made up of mediumgrained, poorly-sorted, fine skewed and very leptokurtic, angular sandy sediments.Petrographic study revealed about 57.3% quartz, 18.8% feldspar, 3.5% mica, 10.5%rock fragment, 5.1% cement, 2.4% heavy minerals, and 2.5% matrix. On the basis of framework composition of quartz, feldspar and mica + rock fragment, the sandstonesof Wuro-Dole were grouped as lithic subarkose with a few of lithic arkose variety.They are generally immature. Concentrations of major oxides include SiO2 (75.9%),Al2O3 (14.2%), Fe2O3 (4.6%), Cao (0.6%), MgO (0.16%), Na2O (1.2%), MnO(0.12%), TiO2 (0.14%), and K2O (2.6%). These geochemical results further validatethat of mineralogical analysis in that the sandstone consists mainly of SiO2, Al2O3,Na2O and K2O which is reflection of the presence of quartz and feldspar. Heavymineral separation showed that the Bima Sandstone is made up of rutile, zircon,tourmaline, sphene, staurolite, sillimanite, and apatite; these heavy mineralassemblages are indicative of mainly felsic igneous and high grade metamorphicrocks. Granite and gneiss suites of both Southeastern and North Central BasementComplexes of Nigeria have been suggested as the probable source areas of the BimaSandstone.

KEYWORDS: Maturity, Provenance, Bima Sandstone, Yola Arm, Nigeria.

INTRODUCTIONSedimentary rocks possess three basic properties- mineral composition, texture, and structures that aretraceable to their source area(s) and environment(s) of deposition. The main objective of provenance study

is to deduce the characteristics of the source area(s) from measurements of compositional and texturalproperties of sediments supplemented by information from other lines of evidence such as directionalsedimentary structures. Textural maturity is an important key to the physical nature of the environment of deposition (Palaeogeography), since it provides a descriptive scale that indicates the effectiveness of theenvironment in winnowing, sorting and abrading the detritus furnished to it (Folk, 1968).

The Bima Sandstone has been widely studied by many workers such as Falconer (1911), Raeburn andBrynmor (1934), Barber et al (1954), Jones (1962), Carter et al (1963), Reyment (1965), Offodile (1989),Ojo (1999), Braide (1992a and 1992b). Most of these works are based on the Chad Basin, Upper BenueTrough, and Middle Benue Trough where the Bima Sandstone outcrops, but not much has been done on itsprovenance. The intent of this sedimentary provenance and maturity study is to reconstruct and interpret thehistory of the sediments from the initial erosion of the parent rocks to the final burial of the detritus of theAlbian Bima Sandstone in Wuro-Dole and Environs using both field evidences and laboratory analyses-


15/24

15

Etobro, A. A. I. and Ejeh, O. I: Continental J. Earth Sciences 2: 14 - 24, 2007.

particularly the heavy minerals separation method. The study area is located in the vicinity of latitudes 9017 45 to 90 23 00N and Longitudes 120 35 30 to 120 4100E (Fig. 1). This covers a surface area of about 102 square kilometres.

REGIONAL GEOLOGY OF THE YOLA ARMThe Yola Arm is the east-west extension of the Upper Benue Trough that connects the Nigerian basins toother rifts in Africa to form a network of West Africa rift systems (Benkhelli, 1989). Sedimentationgenerally started in the Upper Benue Trough during the 4 Albian when a great thickness of continentalsands and clays-the Bima Sandstone- was deposited unconformable on the Precambrian crystallinebasement rocks (Carter et al 1963; Offodile, 1989; Ojo, 1999). This was followed by a marine transgressionthat occurred during the Cenomanian leading to the deposition of transitional beds of sandstones andalternating mudstones and shelly limestones of the Yolde Formation. These passed upwards into apredominantly marine sequence of Turonian-Senonian age. This marine sequence is made up of JessuFormation, Sekule Formation and Numanha Shale in the Yola Arm; while their lateral equivalents of Gongila and Pindiga Formations were deposited in the Gongola Basin.Continental conditions resumed inthe Maastrichtian and resulted in the deposition of the Lamja Sandstone in the Yola Basin while GombeSandstone was deposited in the Gongola Basin (Table 1).

The Bima Sandstone was named by Falconer (1911) as the oldest formation occurring at the base of thesedimentary successions in the Upper Benue Trough. Guiraud (1990) described it as the basal unitreflecting the syn-tectonic deposition of sediments as the basin evolved. It is generally extensive and formsridges and sometimes flat-lying. It stretches to other bounding basins- the Middle Benue Trough to thesouth-west and the Chad Basin to the north east. Its thickness ranges from 100-3,000m (Offodile, 1989). Itis subdivided into 3 parts namely: the Lower Bima Sandstone (B1), the Middle Bima Sandstone (B2) andthe Upper Bima Sandstone (B3) (Carter et al 1963: Offodile, 1989). The Lower Bima Sandstone (B1) ismade up of about 400m thick of sandstones and argillaceous rocks. It is the basal unit of the BimaSandstone sequence and is not exposed in any part of the entire Upper Benue Trough. The Middle BimaSandstone (B2) comprises about 800m thick of coarse-grained sandstone with clays and shales, while theUpper Bima Sandstone (B3) is generally the thickest, consisting of about 1,700m of coarse sandstones.Carter et al (1963) assigned Upper Albian to Lower Turonian age to the Bima Sandstone. The Upper BimaSandstone that outcrops in the study area is the main subject of this present study. It is overlain by theYolde Formation.

The Yolde Formation is made up of a variable sequence of sandstones and shales that marks the transitionfrom continental to marine sedimentation. The sandstone occurrence is suggestive of a beach environment(Opeloye and Obaje, 2005). It is dated as Lower Turonian (Carter et al 1963). The Dukul Formationoverlies the Yolde Formation and it is composed of a sequence of shales and thin limestones. The limestoneis highly fossiliferous- containing mainly ammonites (vascoceratids) that have been used to date it as lowerTuronian (Carter et al 1963; Ehinola et al 2005). The Jessu Formation consists of alternating sequence of grey, white and brown shales and light brown, sandy mudstones with subordinate sandstones. An Upper

Turonian age is assigned to it from its fossil evidence (Carter et al 1963). A sequence of shales andlimestones succeeds the Jessu Formation, and this sequence is termed as Sekule Formation. It is similar tothe Dukul Formation and it is also fossiliferous. An Upper Turonian to Santonian age has been assigned toit. The Numanha Formation marks the end of the marine conditions and it is made up of black shales withoccasional bands of sandstone, nodular mudstone and limestone. The stratigraphic succession of the YolaArm terminates with the deposit of clastic Lamja Sandstone. It consists of parallel laminated sandstonewith interbeds of thin limestone, coal seams and fossiliferous shale. A Campanian age is assigned to it. Thecentral axis of the rifted basin is lined with Tertiary magmatism such as the Biliri phonolites, Longudabasalts, and Ngurore columnar joints that extruded the Cretaceoussediments (Cater et al 1963).

MATERIALS AND METHODSA dual phase data acquisition methodology was adopted- field mapping exercise and laboratory techniques.


16/24

16


Field practice/study: This is a practice in geologic research work targeted at describing the rock types andstructural features. Both systematic and random sampling methods were used in this study. The field studyinvolved a detailed field mapping on a scale 1:10,000 and the observed rock types were described in termsof colour, grain size, grain shape, mineralogical composition, etc. A Global Positioning system (G.P.S.)was used for accurate sample location. Orientations of structural features such as beddings (cross-beddingsand ripple marks) were systematically measured and mapped. Good exposures were logged (6 lithologicprofiles) and drawn to scale (Fig. 2a and b). Well-labeled representative rock samples were obtained forlaboratory analyses. Readings of azimuths of planar structures were fed into stereostat software(www.rockware.com) that generated rose diagrams.

Laboratory Techniques: The representative samples obtained were subjected to granulometric, thin section(Petrographic), heavy minerals separation and geochemical analyses. Extraction of provenance relatedinformation from sediment grain size distributions as discussed by Weltje and Prins (2003) was adopted inthis study.

Granulometric Analysis: Fifteen (15) sandstone samples were air dried and carefully disaggregated in amortar by a rubber-padded pestle to obtain about 100grams of the disaggregated sample. The 100grams of each disaggregated sample was weighed out using the Harvard Trip digital balance and sieved by means of a set of U.S. standard sieves using the Ro-tap electro-mechanical sieve shaker ( M-Tyler) for 15 minutes.Samples retained in each sieve were weighed and their corresponding frequencies and cumulativefrequencies obtained. Cumulative frequency curves were plotted. Statistical parameters (graphic mean,standard deviation, inclusive graphic skewness, and kurtosis) were computed (Table 2) using formulaeproposed by Folk and Ward (1957).

Thin section (Petrographic) Analysis: Twenty (20) samples were selected for thinsection analysis. The thin-section preparation was based on methods described by Ireland (1971). Both friable and consolidatedsamples were used; the friable samples were initially impregnated prior to cutting, in order to harden thesamples. The samples were each mounted with polished side on a glass slide using Canada balsam. Themounted sample was ground initially with a coarse abrasive and later with sludge of fine abrasive on aglass until the slide was fine or thin enough for individual mineral identification. The prepared thin sectionswere examined under a flat stage Petrographic microscope for minerals identification and their modalcomposition determined by point-counting. Mineral identification was based on its optical propertiesoutlined in basic optical mineralogical texts.

Heavy Minerals Separation Analysis: This involved the selective analysis of specific minerals- the heavyminerals that are resistant to the physico-chemical alteration resulting from weathering, transportation,deposition and diagenesis. Each air-dried samples was passed through a forty-mesh (U.S standard sieve,420 microns or 0.42mm) brass screens onto clean weighing paper. The fraction of each sample smaller than420 microns (medium sand and smaller on the Wentworth scale) was then washed in distilled water toremove the fine fractions. About 15g of each sample were separated using standard bromoform heavy

liquid techniques. The heavy mineral grains were washed, dried, and mounted on glass slides using Canadabalsam. Mineral grains in the heavies were identified by standard petrographic techniques (Tickel, 1965)using a polarizing light microscope (M-Meiji). The percentage of the heavy minerals in each sample wasdetermined by counting 150 to 250 grains per samples using a gridded microscope slide.

Geochemical Analysis: Selected representative samples were subjected to a geochemical analysis of sediment whole-rock composition using Atomic Absorption Spectrometric (AAS) method. This involvedsample crushing (pulverizing), powdering and disintegration using acids (concentrated Hydrogen Fluorideand Boric acids). This was followed by measurement of major elemental composition using AAS machine.

INTERPRETATION OF RESULTSTextual Properties of the Bima Sandstone


17/24

17


Results and interpretations of the grain size analysis are presented in Table 2. The calculated graphic meansize of the sandstones varies from 0.16 to 2.21 (coarse- to fine-grained) with an average mean size of 1.24 (medium grained). Standard deviation is a measure of sorting. The standard deviation ranges from0.98 to 1.77 (moderately to poorly- sorted) with an average of 1.39 , poorly sorted sandstones.Inclusive graphic skewness of the sandstones varies from -0.16 to 0.58 (coarse skewed to strongly fineskewed) with an average of 0.07 indicating fine skewed. Kurtosis ranges from 0.6 to 3.4 with an average of 1.61; these imply that they are very platykurtic to extremely leptokurtic and on the average very leptokurticrespectively. Results of the grain size analysis (Table 2) show that these sandstones are about 53% mediumgrained and 33% coarse grained, suggesting deposition under a high-energy environment. About 93% of the sediments are poorly sorted, an indication of fluctuating depositional currents (Tucker, 1988). Thispoorly- sorting may also be as a result variable current velocity and sediments deposition close to theirsource area.

Mineralogical Composition of the Bima SandstoneThe results of petrographic study carried out on 20 sandstone samples of the Bima Sandstone are presentedin Table 3. This study revealed that the sandstones are averagely made up of about 57.3% quartz, 18.8%feldspar, 3.5% mica, 10.5% rock fragments, 2.4% heavy minerals, 5.1% cement, and 2.5% matrix. Therelatively high SiO2 (average 75.9%), Al2O3 (average 14.2%), K2O (2.6%), and Na2O (1.2%) indicatedby the geochemical analysis (Table 4) confirms the presence of quartz and feldspar as the main mineralcomponent, while the occurrence of Fe2O3 (average 4.6%) is suggestive of the ferroginized nature of someof the sandstones. The cementing material is mainly siliceous (quartz) and occasionally iron oxide mineral.The grains are mainly sub-angular to angular, medium to coarse grained, and moderately to poorly- sorted.On the basis of classification of sandstones using framework composition of quartz (Q), feldspar (F), androck fragment + mica (L) on a ternary diagram (Fig 3a); the Bima Sandstone is grouped as lithic sub-arkosewith a few samples indicating lithic arkose (McBride, 1963).

DISCUSSIONMaturity of the Bima SandstoneWeltje and Von Eynatten (2004) reported that chemical alteration and mechanical break down of sourcerocks followed by sorting of particles during transport and deposition, lead to preferential enrichment of specific materials in certain grain-size fractions and hence sediments composition tends to be a function of grain size. Therefore, suitable analytical approaches to sediment provenance also depend on grain size. Thegrain sizes of the Bima sandstone range from medium to coarse (Table 2) is indicative of deposition undera relatively high energy of flow and a probable short distance of transportation as evidenced from arelatively abundance of feldspar a less stable mineral in the Bima Sandstone. The angular to sub-angular shape of the Bima Sandstone is an indication of a short distance of transportation or closeness tothe source area. The mineralogical and textual properties are the diagnostic parameters used in thedetermination of sediment maturity (Pettijohn, 1984). The appreciable concentration of feldspar (Table 3),the dominance of sub-angular to angular shape (Fig. 4), and the poorly sorted nature of the sandstones of the study area, all suggest that they are both texturally and mineralogically immature. The ternary diagram

(Fig. 3a) clearly depicts that over 80% of the sandstone facies in the study area are lithic sub-arkose whileothers are sub-arkose and lithic arkose. A formula adopted by Hubbert (1962) as a measure of maturityindex (i.e. Z.T.R. Index) was applied to these sandstones, giving an average mode of 54% (Table 5);corresponding to immature sediments.

Provenance: Measurement of palaeocurrent is a vital part of the study of sedimentary provenance,current/wind direction(s) and palaeogeography. Sedimentary structures prominent in the Bima Sandstone inWuro Dole and environs include imbricate structures and beddings (cross-beddings, planar cross-beddings,trough cross-beddings, ripple marks, etc) (Fig. 2a and b). The planar cross-bedding was used in thedetermination of palaeocurrent direction for the Bima Sandstone and it corresponds to the direction of maximum angle of dip, while the asymmetry of the ripples gives the palaeocurrent direction. Strikemeasurements imputed into the package stereostat generated current rose diagrams (Fig. 5) showing thatthe ancient current directions were mainly SSE-NNW for the cross-bedding and NE-SW/NW-SE for the


18/24

18


ripple marks respectively. These current rose diagrams showed a strong preferred orientation, with most of the azimuths falling in quadrants with clearly defined modes. The rose diagrams indicate a unimodal tobimodal pattern, that is, the sediments were probably supplied from one or two source areas respectively.The palaeocurrent pattern exhibited by the sandstones of Wuro-Dole and environs shows that the sedimentswere sourced mainly from the south eastern part and partly from the southwestern part of the study area.

Microscopic examination of the heavy minerals contained in the sandstones of the study area revealed bothopaque and non-opaque minerals (Table 5) and (Fig. 4C and D). The opaque mineral is made up of about19.6% while the non-opaque minerals consist of about 20.6% zircon, 11.6% rutile, 13.0% tourmaline,10.4% apatite, 8.6% sillimanite, 4.9% staurolite and 11.4% sphene. According to Friedman and Sanders(1978), and Pettijohn (1984), these heavy mineral assemblages in any sandstone suggest a probable igneousand metamorphic parent rocks. They have shown that the occurrences of zircon, tourmaline, apatite, andsphene suggest a felsic igneous source while rutile is indicative of mafic igneous origin. The kyanite,sillimanite, and staurolite are evidence of high grade metamorphic source. The sandstones consist of bothmonocrystalline and polycrystalline quartz aggregates, but the monocrystalline is dominant; this issuggestive of a probable granitic origin. The results of the geochemical analysis (Table 4) revealed that theBima Sandstones consist of relatively high SiO2, Al2O3, Na2O, K2O, and CaO; these suggest a quartz andfeldspar-rich source area.

A comparative overview of the framework composition of the sandstone with the work of Dickinson et al (1983) on QFL ternary diagrams (Fig. 3b) showed that some of the sandstones are of a recycled origen(provenance). Considering the regional geology of the study area, the Older Granites and the Migmatite-gneiss complex of the South Eastern Basement (Umeji, 1988) as well as those of the North centralBasement Complexes (Oyawoye, 1972) are probable source areas of the Bima Sandstone at Wuro Dole andenvirons.

CONCLUSIONSBima Sandstone outcropping at Wuro-Dole and environs was mapped and studied for its texturalcharacteristics and mineralogical compositions in order to establish maturity and provenance for it. Thegeological mapping exercise revealed that the study area is made up of medium grained, poorly-sorted,cross-bedded and ripple-marked sandstones. The sandstones, which are generally immature, have colourrange from white to reddish-brown; the reddish brown is evidenced from the relatively high iron oxidecontent in some sandstones.

Mineralogically, it is composed of mainly quartz, feldspar, mica, rock fragments and heavy mineralassemblages rutile, zircon, tourmaline, sphene, apatite, sillimanite, and staurolite. The sandstones havebeen classified as lithic sub-arkose and a few lithic arkose. They are characterized by a relatively highconcentration of SiO2, Al2O3, K2O, and Fe2O3, while other oxides (MgO, MnO, and TiO2) are relativelylow. Palaeocurrent plots based on the strike measurements of the associated cross-beddings and ripplemarks showed NNW SSE and NE SW/NW SE directions respectively. A combination of the texture,

geochemical analysis, mineralogical composition, palaeocurrent pattern and the heavy mineralassemblages; was used to suggest the Older Granite and Gneiss suites of Southeastern and North CentralBasement Complexes as the provenance for the Bima Sandstone at Wuro Dole and environs.

REFERENCESBARBER, W., TAIT, E.A. and THOMPSON, J.H. 1954: The Geology of the Lower Gongola. Ann. Rept.

Geol. Surv. Nigeria. Pp. 5 20.BENKHELIL, J. 1989: The origin and evolution of the Cretaceous Benue Trough, Nigeria. Jour. African

Earth Sciences. Vol. 8. pp. 251-282.BRAIDE, S. P. 1992a: Studies on the Sedimentation and Tectonics of the Yola arm of the Benue Trough:

Facies Architecture and their Tectonic significance. Jour. Mining and Geology. Vol. 28, No. 1,pp. 23 31.


19/24

19


BRAIDE, S. P. 1992b: Morphology and Depositional history of An Aptian Albian Crevasse splay in theBima Sandstone, Yola Basin Benue Basin. Bull. Nig. Assoc. Petroleum Expl, Vol. 7, No. 1 pp46 50.

CARTER, J.D., BARBER, W., TAIT, E.A. and JONES, J.P. 1963: The Geology of parts of Adamawa,Bauchi and Bornu Provinces in North-eastern Nigeria. Geol. Surv. Nig. Bull. 30.109p

DICKINSON, W.R. Beard, L.S; Brakenridge, G.R. Erjavee, J.L: Ferguson, F.C. Imman, K.F; Knepp, R.A;Lindberg, F.A; and Ryberg P.T. 1983: Provenance of North American Phanerozoic sandstonesin relation to tectonic setting. Geol. Soc. Amer. Bull. 94. pp.

EHINOLA, O.A., Joshua, E. O. Opeloye, S.A. and Ademola, J.A., 2005: Radiogenic Heat Production of the Cretaceous sediments of Yola Arm of Nigeria Benue Trough: Implications for ThermalHistory and Hydrocarbon Generation. Jour. Applied Sciences, Vol. 5, No. 4, pp. 696 701.

FALCONER, J.D. 1911: The Geology and Geography of Northern Nigeria, London.FOLK, R.L 1968: Petrology of Sedimentary Rocks, Hemphills, Austin Texas, 172p.FOLK, R. L. and WARD, W. 1957: Brazos River Bar. A study of significance of Grain-size Parameters.

Jour. Sed. Pet. Vol. 27, pp. 3 26.FRIEDMAN, G.M. and Sanders, J.E. 1978. Principles of Sedimentology. John Willey and Sons. New

York. 792p.GUIRAUD, M. 1990: Tectono Sedimentary framework of Early Cretaceous continental Bima Formation,

Upper Benue Trough, N.E. Nigeria. Jour. African Earth Science. Vol. 10. pp. 341 353.HUBERT, J. F. 1962: A Zircon Tourmaline Rutile Maturity Index and Interdependence of the

composition of Heavy Mineral Assemblages with the cross composition and Texture of Sandstones. Jour. Sed. Pet. Vo. 32 No. 3 pp. 440 450.

IRELAND, H. A., 1971: Preparation of Thin-sections. In: Carvier, R.E. (Ed.): Procedures in SedimentaryPetrology. John Willey & Sons, New York. Pp. 369-383.

JONES, G.P. 1962: Deformed Cross-Stratification in Cretaceous Bima Sandstone, Nigeria. Jour. Sed. Pet.Vol. 32. pp. 231-239.

McBRIDE, E.F., 1963: Classification of common Sandstones. Jour of Sedimentary Petrology . Soc Econ.Pal. Min. Tulsa Oklahoma. Vol. 33. pp. 664-669.

OFFODILE, M.E., 1989: A Review of the Geology of the Cretaceous of the Benue Valley. In: KOGBE,C.A. (Ed.) Geology of Nigeria. Rock View Nigeria Ltd. Jos. Pp. 365- 376.

OJO, O.J. 1999: Depositional Environments, Palynological and organic Geochemical studies of Gongolaand Yola Basins, Nigeria: Implications for Hydrocarbon Potential. Unpubl. Ph.D. These,University of Ilorin, Ilorin.

OPELOYE, S.A. and Obaje, N.G. 2005: Ostracods from the Yola Arm, Upper Benue Trough, Nigeria.Global Jour. Geol. Sc. Vol. 3, No. 2. pp. 179 185.

OYAWOYE, M.O. 1972: The Basement Complex of Nigeria. In: Dessauvagie, T.F.J. and Whiteman A.J.(Eds.), African Geology. University of Ibadan, Nigeria. Pp. 67-99.

PETTIJOHN, F.J., 1984: Sedimentary Rocks. 3rd Ed., CBS Pub. & Distr., Delhi. 628p.RAEBURN, C. and Brynmor, J., 1934: The Chad Basin; Geology and Water Supply. Bull. Geol. Surv.

Nigeria. No. 15.

REYMENT, R. A. 1965: Aspects of Geology of Nigeria. Univ. Ibadan Press, Ibadan. 145p.TICKEL, F.G. 1965: The Techniques of Sedimentary Mineralogy. Elsevier Publishing Company, New

York. 220p.TUCKER, M.E., 1988: Sedimentary Petrology: An Introduction. ELBS ed. Blackwell Scientific Publ.

252p.UMEJI, A. C. 1988: The Precambrian of south eastern Nigeria, a Magmatic and Tectonic Study. In:

Oluyide, P.O., Mbonu, W.C., Ogezi, A.E., Egbuniwe I.G., Ajibade A.C. and Umeji, A.C (Eds.);Precambrian Geology of Nigeria. A publication of the Geological Survey of Nigeria. Pp. 69-75.

WELTJE, G.J. and Prins, M.A., 2003: Muddled or Mixed? Inferring Palaeoclimate from size distributionsof deep-sea clastics. Sed. Geol. Vol. 162, pp. 39-62.

WELTJE, G.J., and Von Eynatten, H., 2004: Quantitative Provenance Analysis of Sediment: Review andOutlook. Sed. Geol. Vol. 171, pp. 1-11.


20/24

20


9 0 1745N

12 0 35 30E9 0 23N

12 0 41E

1 0 1 2km

WuroDole

GarinBuba 700

DiginoNgar awo

1500

1500

15001000 Lugga

Nassarawo

Jambutu

WuroAbba

R. Benue

600

Girei

Pariya

WuroJuba

Fig. 1: Location Map showing WuroDole and Environs (inset: Map of Nigeria indicating study area)

0 200km

Yola

5 0 N

10 0 N

13 0 N

14 0 E10 0 E5 0 E

19

2118

20 ORIE

3031

28

26

35

38

2440

44

46OVE

47

16 OVE

8

48

50OVE

49

51

52

53

55

56

7

13

4

5OBA

16OBA

54

57

58

WuroMallum

Key

Footpath

Minor road

CotourLine100

River

Settlement

Sample location5

12 0 35 30E

Key

12 0 35 30E12 0 4100E

9 0 1745N

9 0 23 00N

N

Fig. 2A: Lithologic section of the Bima Sandstone showing its characteristic beddings observed at location16 OVE of study area.

AGE FORMATION LITHOLOGY DESCRIPTION

A

L

B

I

A

N

BI

MA

-

SANDSTONE

Medium-coarse grained, yellowish, poorly-sorted sandstone

Coarse grained, flat-bedded, yellowish, poorly-sorted Sandstonewith some clayey intercalations

Medium grained, cross-bedded reddish brown moderately wellsorted sandstone

Coarse grained, cross-bedded reddish-brown moderately sortedSandstone

Fine-medium grained, whitish, poorly sorted sandstone

Medium grained, white to brown, moderately sorted sandstone

Coarse grained, brownish, poorly sorted sandstone

1m

0f m c

Fine-medium grained, whitish brown, moderately well-sorted Sandstone contain someclay, inclusions


21/24

21


16OBA

5OBA

16OVE

46OVE

50OVE

20ORIE

KEY

Fine grained Ripple markedSandstone

Cross-bedded, medium-coarse grained Sandstone

Flat-bedded, -coarsegrained Sandstone

Fine grained Sandstone

Medium-Coarse grainedSandstone1m

f m c0Fig. 2B: Lithostratigraphic Sections of the Bima Sandstone Outcropping at Wuro Dole and Environ (Locations,

160BA, 5OBA, 16OVE, 50OVE, 46OVE, and 20ORIE)

Q3

1 8

4 5

1 3

F 15 50 L

37

25Transitional

Arc

*

UndissectedArc

BasementUplift

Decreasing maturity or stability

Transitional/Contine ntal

Cratoninterior

RecycledOrogenic

DissectedArc

Continental BlockMagmatic arc

Recycled orogen

Provenance Categories

Fig. 3b: QFL diagram showing fields of the threemain provenance types and selected subfields

(Dickinson et al 1983)

L

Q

F

55

25 25

50 50

10 105025 25

A r k o

s e

S u b - A

r k o s e

Quartz arenite

S u b - l i t h i c a r e n i t e

Lithic sub-arkose

L i t h i c A r e n i t e

LithicArkose Feldspathic Lith arenite

Fig. 3a: Framework Composition of Sandstone within theStudy Area on a Ternary Diagram


22/24

22



23/24

23


Table 3: Mineralogical Composition of some selected sandstones of Wuro Dole and Environs

SampleNumber

Quartz(%)

Feldspar(%)

Mica(%)

HeavyMinerals

(%)

Rock Fragment

(%)

Cement(%)

Matrix(%)

L13aL40L31L50L18bL21L8L28cL30

L38L13L16L24L33L45L49L5L52L16L38Average

606050456055606060

606045526260606260546057.3

151717221717191922

151624201624221816182218.8

214417444

426424-34823.5

5-2-65523

242-31211222.4

101613151035710

121216161261210105910.5

551010510552

5356342231025.1

314413212

232221246322.5


24/24

24


Received for Publication: 18/11/2007

Accepted for Publication: 15/12/2007

Corresponding Author:Etobro, A. A. I.Department of Geology, Delta State University, P.M.B. 1, Abraka, Nigeria.E-mail: [email protected]

Vol 2 - Cont. J. Earth Sci 2

Documents