Research Journal of Environmental and Earth Sciences 4(5): 534-545, 2012
ISSN: 2041-0492
© Maxwell Scientific Organization, 2012
Submitted: March 02, 2012 Accepted: April 20, 2012 Published: May 15, 2012
Abstract: Selected rock samples were collected from outcrops from the eastern part of the Upper East Region with the aim of determining their chemical composition and classification. Samples were obtained from granitoids and the Birrimian formation located in Bongo, Talensi-Nabdam, Bawku West and Garu-Tempane
Districts. Rocks were identified mineralogically using hand lenses. The composition of the samples was determined using X-Ray Fluorescence (XRF) after which several quantitative and qualitative techniques were employed to analyse the data. Some of these techniques included physical examination, Chemical Alteration
Index (CIA), scatter plots, discrimination diagrams and Aluminium Saturation Index (ASI). The mineralogical analysis showed that the rocks generally contained K-feldspar, plagioclase, muscovite, hornblende, quartz and biotite as major minerals. Physical examination revealed that samples had undergone some alteration that was not evident at the time of sampling and this was confirmed by calculations using the Chemical Index of
Alteration (CIA). The CIA values of the fresh rocks ranged from 70 to 125 suggesting that the samples had undergone intensive alteration. Scatter plots and discrimination diagrams suggested that the samples were not of basaltic origin but were thoeleiitic in character. The Aluminium Saturation Index (ASI) revealed that most samples were metaluminus and that the majority of samples were sub-alkaline and therefore basic in character.
Keywords: Basalt, diorites, granitoids, granodiorites, metaluminus, thoeleiite, upper east region
INTRODUCTION
Rocks are aggregates of one or more minerals (Hatch et al ., 1979) formed from either cooling of molten lava, consolidation of sediments or alteration of already formed rock materials under high pressures and temperatures.
Minerals may be either amorphous or crystalline and vary in grain size and morphology. It is difficult to trace the mineralogical origin of many rocks to the original magma since the original composition may have changed as a result of the lost of volatile substances during exposure leaving behind residual materials, (Hatch et al ., 1979).
The type of rock formed and its mineralogical composition however, depends on the mode of formation and the host environment. Therefore the chemical composition of rocks depends not only on the original chemical composition of the magma but also the processes occurring during or after the cooling, duration and the geochemical environments, in which the rock was initially deposited. It is therefore not surprising that in a geological environment various rocks types are found with varying compositions ranging from minimal chemical differences to very different rock types.
In Ghana, there are many different rock types with varying mineralogical and chemical compositions. The composition of rocks defines the various uses by man.
Rock materials are in road and building construction, utilizing properties such as hardness, durability, quality and colour of grains among others. Rocks also host precious metals which are extracted for various uses by man. Since the quality and use of a rock is determined by its chemical composition and origin, it is important to examine these properties carefully to determine the type of uses they can be put into since the Upper East Region has abundance of rock outcrops with little known about them. The main objective was to analyse and assess the chemical composition of the samples to enable the determination of the origin of the rock located in this area.
It was in this light that during the University for
Development Studies Third Trimester Field Practical
Programme (TTFPP), a collection of rock samples was made from June to July 2010 for this study.
MATERIALS AND METHODS
Geological setting of the study area: The area of study encompasses four districts of the Upper East Region.
These include Bawku West, Bongo, Garu-Tempane and the Talensi-Nabdam districts which are located at the eastern part of the Upper East Region. The area is located between latitudes 10º 30
"
and 10º 45
"
N and longitudes 0º
15
"
and 0º 50
"
W. These cut through the Upper Birrimian intruded with granites of varying compositions. The study area is boarded on the south by the West and East
534

Res. J. Environ. Earth. Sci., 4(5): 534-545, 2012
Fig. 1: Geological and location map of study area (number of samples are in parenthesis)
Mamprusi Districts of the Northern Region, east by the
Republic of Togo, west by the Bolgatanga Municipal
Assembly. It is located between latitudes 10.7º and 10.9º
N and longitudes 0.2º and 0.8º W. The area is drained mainly by two rivers the White and Red Volta Rivers that form part of the Greater Volta Basin. These rivers take their sources from Niger and Burkina Faso and on entry into Ghana the Red Volta finally drains into the White
Volta. Other smaller rivers present are the Tamne, Nahan,
Kulupielugu and Biankuri (Edmonds, 1956) which also drain into the White Volta. At the southeastern part of the area, the Morago River joins the White Volta and the two act as a boundary between the Northern and the Upper
East Regions. The geology of the study area (Fig. 1) is classified into the biotitic, hornblendic, Tarkwaian complexes and remnants of the crystalline rocks occupying the northern parts with the Upper Voltaian running along the southern base as an extension of the
Gambaga Scarp (Edmonds, 1956). The rocks in the area are grouped into volcanic and non-volcanic. Those around
Garu-Tampane area are non-volcanic while the rest are volcanic in origin. The biotitic complex comprises of biotite granite, biotite-granodiorite and a variation of gneisses of these two rock types which have contact with the Birrimian. The fine and course-grained varieties occur with some of the rocks foliated from very fine gneissic structure to coarse foliated and banded types. In many cases the biotite alters to chlorite and occasionally the potash feldspar is pink. The hornblende may be present as an original constituent or derived from assimilated
Birrimian material or by intermixing and veining due to later hornblendic intrusions. The biotitic complex is gneissic and the granitoid biotite-granodiorites consist mainly of albite-oliogoclase, quartz and biotite with some green hornblende. The biotite granites differ from these in the feldspar content of which the K-feldspars (orthoclase and microcline) are higher than albite. Dark biotite-rich granodiorites exist locally and occasionally, the complex is dominated by biotite-quartz rock with little or no feldspar or by felsic granite which is poor in biotite. The
535

rocks of the hornblendic complex include granodiorite, granite amphibololite, hornblendite and rocks of intermediate between hornblende-granodiorite and amphibololite. The granodiorites and granites are typically medium coarse-grained rocks containing green or greenish-black hornblende and frequently pink feldspar. Amphibole-rich rocks are widespread. It is generally coarse grained with large hornblende crystals.
The feldspar content is variable and sometimes negligible and quartz is also sometimes with biotite in small amounts
(Edmonds, 1956).
The Tarkwaian system rocks are found in the northmost part of the study area surrounding the Birrimian system. No sample was collected from this area. It strikes conformably with hornblende, hornblende-biotite and quartz-biotite and fine-grained massive greenstone. The rocks are impure carbonated granite with euhedral magnetite. The other crystalline rock remnants which are intrusive include quartz, quartz-feldspar veins, pegmatites and some aplites. There are also quartz-dolerites, which are dolerite-like intrusions and grade into the hornblendegranite, located near the hornblende complex close to
Zawse. These rocks are found along the confluence of the
White Volta-Nahu Rivers. Some of these rocks are medium grained and consist of andesine-labradorite, pyroxenes of the diopside-hedenbergite series and some amount of quartz with crystals of orthoclase, biotite and pyrite. Some of these rocks are basic with saussyritsed bytownite-anorthite and less quartz. Also at the eastern side of the White Volta-Nahu confluence there is an intrusion into greenstone which is a dyke of porphyrite. It is medium grained with well-developed andesine.
Diopside-hedenbergite series which sometimes appear altered to chlorite are observed with little biotite and quartz (Edmonds, 1956).
Sample collection and analyses:
Res. J. Environ. Earth. Sci., 4(5): 534-545, 2012
RESULTS AND DISCUSSION
About 29 rock samples were collected from outcrops within the study area.
Before a sample was collected, the rock was well cleaned and trimmed to ensure it was fresh. During trimming, if there were any symptoms of alteration inside, it was rejected. All samples were labelled according to the location and then numbered serially with dates of collection and sent to the laboratory for further examination. Samples were crushed with steel mortar and pestle and pulverized into powder for chemical analysis.
The powders were analyzed using X-Ray Fluorescence
(XRF) at the Ghana Geological Survey Laboratory for both major and trace elements. It was not possible to do thin-sectioning due to logistical constraints but were examined using hand specimens.
In the laboratory, the rock types were identified using mineralogy, colour and grain size with the aid of hand lens for which eight rock types were identified.
Mineralogical composition of the rocks: Generally eight rock types were mineralogically identified which included biotite-granodiorite, hornblende-granodiorite, granite, diorite basalt, granitoid, schist and a ferricate material
(Table 1). The minerals identified in the samples from the western part of the study area which included Bongo and
Talensi-Nabdam were mainly K-feldspar, plagioclase, muscovite, hornblende, quartz and biotite. These minerals were well developed in most samples. In the Bawku West and Garu-Tempane, the rocks contained K-feldspar, biotite, hornblende and muscovite and higher percentage of dark minerals and low quartz. The low quartz content was supported by the calculated Niggli values which ranged from 10.69 to 105 in the Bawku West and Garu-
Tempane area. In fact only very few samples had Niggli values above 90 hence many samples were deficient in free quartz. The samples from Talensi-Nabdam and
Bongo had Niggli values ranging from 8.07 to 152 and only one sample had-2.71. The Bawku West and Garu-
Tempane located in the volcanic rock area were observed to have less free quartz but more of darker minerals while the Bongo and Talensi-Nabdam in the Birrimian were more felsic and brightly coloured. The colour of the latter is an attraction for use in the tile industry. The grain size of all the rocks ranged from fine-to coarse-grained suggesting the differences in the rate of cooling during deposition.
Geochemistry of rocks:
Major element geochemistry: All the major oxides together with P
2
O
5
, SO
3
, Cl and Lost of Ignition (LOI) were analyzed (Table 2). The percentage totals ranged from 99.16 to 109 wt%. The SiO
2
content ranged from
45.69-66.4% while Al
2
O
3
content was 11.84-15.55 wt% and Fe
2
O
3
ranged from 1.32-13.25 wt% with means 56.54,
13.69 and 5.28 wt%, respectively.
The results showed that SiO
2
and Al
2
O
3
were highest in Bawku West while Garu-Tempane samples were the lowest. The highest mean composition of Fe
2
O
3
was 8.31
wt% in samples from Garu-Tempane while those from the other areas had less than 5 wt% as a mean value. The
Na
2
O content ranged from 2.18 to 4.48% while that of
K
2
O was 0.81 to 5.53% with means of 3.09 and 1.94%, respectively. The elements of these oxides are normally associated with feldspars and other major minerals such as muscovite, biotite, clay minerals and zeolites.
The samples from Bongo and Talensi-Nabdam were dominated by feldspars especially plagioclase and Kfeldspars as observed from hand specimens and this explains the high content of these oxides in those areas.
The K
2
O content as well as Na
2
O were low in the Garu-
536

Res. J. Environ. Earth. Sci., 4(5): 534-545, 2012
18
19
20
21
22
23
24
25
26
27
12B
13
14
15
16
17
6
7
8
9
10
11
12A
3
4
5
1
2
Table 1: Samples with their physical characteristics from the study area
ID. No Location District Sample type
Yal
Datoko
Nyogwari
Sekoti A
Sekoti B
Talensi-nabdam
Talensi-nabdam
Talensi-nabdam
Talensi-nabdam
Talensi-nabdam
Granitodi
Granite
Granite
Hornblende-granodiorite
Hornblend-granodiorite
Kongo
Bongo-beo A
Bongo-beo B
Bongo-beo C
Bongo-beo D
Bong central
Dua-nayire
Dua-nayire
Adaboya
Tamoka A
Tamoka B
Kusanaba A
Kusanaba B
Talensi-nabdam
Bongo
Bongo
Bongo
Bongo
Bongo
Bongo
Bongo
Bongo
Bawku-west
Bawku-west
Bawku-west
Bawku-west
Basaltic
Biotite-granodiorite
Biotite-granodiorite
Granite
Granite
Hornblende-granodiorite
Hornblende-granodiorite
Hornblende-granodiorite
Hornblende-granodiorite
Schist
Granitoid
Granitoid
Granitoid
Kusanaba C
Kusanaba D
Kugri hill
Nate A
Nate B
Nate C
Kugri A
Kugri B
Red volta A
Red volta B
Bawku-west
Bawku-west
Garu-tempane
Garu-tempane
Garu-tempane
Garu-tempane
Garu-tempane
Garu-tempane
Talensi-nabdam
Talensi-nabdam
Granitoid
Laterite
Biotite-granodiorite
Biotite-granodiorite
Biotite-hornblende
Diorite
Diorite
Diorite
Schist
Schist
Physical characteristics
K-feldspar, hornblende, quartz, slightly weathered
K-feldspar, hornblende, quartz, medium grained
K-feldspar, hornblende, quartz
Dark minerals with little quartz
Biotite, hornblende, quartz
Biotite, hornblende, feldspar, quartz. coarse-grained
K-feldspar, hornblende, quartz. coarse-grained
K-feldspar, hornblende, quartz. coarse-grained
K-feldspar, hornblende, quartz. medium-grained
K-feldspar, hornblende, quartz. medium-grained
K-feldspar, hornblende, quartz. medium-grained
K-feldspar, hornblende, quartz. coarse-grained
K-feldspar, dark minerals dominant, little quartz.
Dark minerals dominant, K-feldspar, quartz
Dark minerals dominant, K-feldspar, quartz
K-feldspar, dark minerals dominant, quartz
Weathered iron-rich lateritic rock possibly from granitoid
Biotite, hornblende, plagioclase, quartz coarse-grained
Biotite, hornblende, plagioclase, quartz coarse-grained
Biotite, hornblende, plagioclase, quartz medium grained
Dark minerals quartz with yellowish-green stains
Dark minerals with quartz. reddish-brown
Fine grained but undergone alteration
Fine grained but undergone alteration
22
23
24
25
26
27
5
6
7A
7B
8
9
Table 2: Chemical composition of samples (in wt %) from study area. (Statistics do not include sample 19)
ID. No Location
3
4
1
2
Yal
Datoku
Nyogwari
Sekoti A
SiO
2
Al
2
O
3
Fe
2
O
3
CaO
63.14
13.90
2.51
2.33
58.56
14.22
3.25
3.91
66.74
11.94
1.32
0.74
63.86
13.83
2.86
1.96
MgO
2.34
2.20
1.27
2.46
Na
2
O K
2
O TiO
2
MnO P
2
O
5
SO
4
Cl LOI Total
4.48
2.56
0.32
0.03
0.16
0.23
0.02
7.90
99.92
4.44
0.93
0.42
0.05
0.26
0.21
0.02
21.50
109.97
4.28
3.23
0.30
0.03
0.08
0.23
0.02
9.40
99.58
4.31
3.54
0.50
0.06
0.22
0.24
0.02
6.70
100.56
Sekoti B
Kongo
56.05
62.37
14.72
13.07
7.55
2.44
5.19
2.15
Bongo-beo A 46.37
14.37
6.94
4.80
Bongo-beo 48.57
13.92
8.02
5.81
Bongo-beo B 57.47
13.48
4.90
2.79
Bongo-beo C 61.56
13.59
4.61
3.33
3.88
2.08
4.18
4.83
2.38
2.72
3.52
4.18
3.35
1.82
3.10
2.57
0.56
0.32
2.11
0.13
0.05
0.09
0.31
0.20
1.00
2.49
0.23
0.23
0.01
0.02
0.02
3.60
9.40
13.50
99.93
99.61
99.53
3.00
2.11
0.99
0.13
0.44
0.22
0.02
11.10
99.16
3.11
5.14
1.52
0.12
0.63
0.23
0.02
8.70
100.49
3.55
5.35
1.18
0.08
0.56
0.23
0.02
3.50
100.29
15
16
17
18
19
20
21
10
11
Bongo-beo D
Bongo central
12A Dua nayire
55.60
62.01
59.60
12.28
13.47
13.99
5.83
1.35
3.17
3.60
1.04
1.90
12B Dua nayire
13 Adaboya
14 Tamoka A
62.98
57.51
54.84
13.31
12.05
13.65
3.51
5.02
7.12
2.34
3.60
6.08
Tamoka B
Kusanaba A
Kusanaba B
Kusanaba C
*Kusanaba D
Kugri west
Nate A
61.46
63.79
62.25
61.95
28.83
56.46
63.18
15.26
14.83
15.55
14.97
14.99
13.74
14.65
3.35
3.55
5.59
3.86
32.90
4.72
2.54
1.95
2.32
2.81
2.39
0.33
4.17
2.96
Nate B
Nate C
Kugri A
Kugri B
Red volta A
Red volta B
Mean
Minimum
Maximum
46.03
11.84
13.25
9.87
55.26
14.23
7.22
5.98
48.97
10.97
9.00
45.69
12.13
11.18
9.86
54.79
14.24
7.10
4.68
53.88
57.53
45.69
66.74
12.20
13.84
13.69
11.84
15.55
6.99
5.38
1.32
13.25
4.60
4.01
0.74
9.87
3.23
1.22
2.55
3.28
4.77
1.87
0.11
0.72
0.23
0.02
8.40
99.94
3.52
4.41
0.31
0.04
0.08
0.22
0.02
12.50
100.19
3.61
3.46
0.85
0.07
0.41
0.23
0.01
10.70
100.55
2.71
4.06
3.64
2.95
4.18
4.03
0.64
0.68
0.06
0.09
0.38
0.55
0.24
0.20
0.02
0.02
6.40
9.40
100.41
100.28
10.42
2.33
1.99
0.50
0.13
0.15
0.20
0.02
2.50
99.99
2.39
2.48
3.34
2.59
0.86
3.01
1.82
5.16
3.66
3.01
3.49
0.45
3.82
4.42
3.10
2.91
3.19
3.11
0.36
1.22
1.35
0.43
0.35
0.49
0.43
0.68
0.58
0.35
0.06
0.06
0.09
0.07
0.06
0.06
0.03
0.11
0.11
0.14
0.16
0.14
0.31
0.17
0.22
0.22
0.16
0.25
0.31
0.21
0.21
0.01
0.02
0.02
0.01
0.01
0.00
0.00
8.60
5.70
4.10
7.10
20.20
11.70
9.10
100.10
99.94
100.83
101.44
100.02
100.00
100.80
6.85
2.86
0.81
1.03
0.20
0.13
0.23
0.00
6.70
99.79
11.13
2.18
2.01
0.46
0.12
0.14
0.22
0.02
1.80
100.77
6.60
4.36
1.22
2.57
0.81
0.63
0.17
0.07
0.21
0.02
7.50
99.72
8.51
2.45
0.86
0.67
0.21
0.08
0.22
0.02
8.40
100.28
10.34
2.71
1.73
0.45
0.11
0.14
0.22
0.01
4.10
100.02
10.48
2.64
1.63
0.44
0.11
0.13
0.21
0.01
5.10
100.06
3.38
2.18
2.72
0.51
0.69
0.30
0.09
0.03
0.28
0.07
0.31
0.16
0.02
0.00
8.04
1.80
10049
99.16
11.13
4.48
5.35
2.11
0.21
1.00
2.49
0.02
21.50
109.97
537

Res. J. Environ. Earth. Sci., 4(5): 534-545, 2012
Tempane samples as these were dominated by ferromagnesian minerals. Late tectonic granitoids normally form biotite and hornblende bearing plutons ranging from tonalite to granodiorite which are metaluminous in character and have low K content less than 3% K
2
O while post-tectonic granitoids are characterized by K
2
O ranging from 4 to 6% and variable peraluminous or metaluminous character with biotite and muscovite being the dominant mafic minerals. Most samples contained K
2
O<4 wt% except those from Bongo area suggesting that they could be late forming granitoids.
The Bongo granitoids with K
2
O>4 wt% could have been caused by mesomatism or metamorphosis. However, earlier works have differentiated various granite rock types in Ghana into the Cape Coast and Winneba (G1),
Dixcove (G2) and Bongo (G3) granite types (Kesse,
1985). This differentiation was based on the K
2
O content of the rocks in the area. The Bongo Granites were found to have high K
2
O ranging from 0.36 to 5.36% with majority exceeding 4 wt% which was in line with the earlier work. The laterite sample from Kusanaba in the
Bawku West had its alkaline and alkaline-earth metals almost leached out.
The composition of the alkali-earth oxides CaO and
MgO ranged from 0.74 to 9.87 wt% and 1.22 to 11.13
wt%, respectively except a lateritic sample which had
0.33 and 0.86% for CaO and MgO, respectively. The mean CaO content of each the areas was 3.11 (Bawku
West) 3.20 (Talensi-Nabdam) 3.25 (Bongo) and 6.97 wt%
(Garu-Tempane) and that for MgO included 3.1 (Bongo),
4.24 (Bawku West) 4.38 (Talensi-Nabdam) and 6.32 wt%
(Garu-Tempane). The samples from Bongo had the lowest
MgO content suggesting that these rocks contained low
Mg-rich minerals. The Garu-Tempane rocks had higher
CaO and MgO contents up to 9.9 and 11.1 wt%, respectively suggested the availability of mafic minerals.
Also the geology suggested that some of the rocks are carbonated and this may contribute to relatively higher
CaO and MgO contents in this particular area.
The TiO
2 content was low in all samples generally
<1.0 wt%. But some samples from Bongo Beo, being biotite-granodiorites, were relatively richer in TiO
2
with levels up to 2 wt%. Titanium is associated with mica and feldspar groups of minerals and its level could be attributed to the presence of these minerals in the rocks.
It is known that iron-rich K-feldspar also contain up to 10 wt% TiO
2
. Other sources of Ti are from minerals where it can substitute for Al, Mg or Fe (Deer et al ., 1996). The relative level of TiO
2
in the Bongo Beo samples correlates well with K
2
O content indicating that the K-feldspar may be iron-rich. Scatter plot of TiO
2
against CaO showed a significant correlation in samples from the Bawku West and the Talensi-Nabdam areas suggesting the presence of feldspar minerals may have a bearing on the level of TiO
2
.
However, it is known that Ti is associated with Ca in minerals such as sphene, pyroxenes and the spinel minerals (Deer et al ., 1996) indicating the availability of these minerals in the samples could explain the presence of TiO
2
.
Levels of P
2
O
5
, SO
3
and Cl were generally very low.
P
2
O
5 is usually associated with Ca in apatite or monazite while S is derived from minerals such as anhydrite; barite and gypsum. Minerals containing Cl include halide, chloroapatite and some derivatives of amphiboles where it replaces either F or OH ions in the rock minerals (Deer et al ., 1996). However, SO
3
and Cl can also be derived from either inclusions from the main rock matrix or anthropogenic sources. Phosphorous content was generally low rarely above 0.70 wt% except in Bongo-
Beo granodorite where 1.0 wt% was obtained. Generally the samples from the Bongo area are relatively richer in
P
2
O
5
than the others.
Comparison of chemical composition of rocks: The composition of the rocks was compared using the molar ratios and some variation diagrams. The K
2
O/Na
2
O and
CaO/Na
2
O molar ratios were calculated to show whether the relative levels of the oxides. Earlier workers used these ratios together with trace elements to categorize rock types (Kesse, 1985). From the results, K
2
O/Na
2
O ratio was lowest in Garu-Tempane with a range from 0.19
to 0.61 and mean of 0.28 while in Bongo the mean ratio was 0.79 and a range from 0.4 to 1.09 thus suggesting a relatively higher K.
In the case of CaO/Na
2
O ratio, the highest ratio was observed in Garu-Tempane samples (1.15 to 6.93) while the others had ratios ranging from 0.3 to 4.49. These rock types from Garu-Tempane were more of ferromagnesian character as suggested by high content of Ca and Mg relative to Na. The chlorite schist samples from the Red
Volta had a ratio of 1.73 indicating higher Ca relative to
Na (Table 1). In all the values of SiO
2 especially K
2
, Na
2
O, CaO and
O were variable to different degrees especially K
2
O. The variation of K
2
O may not come from any inherited source but as a result of chemical modification during metamorphism which is consistent with the earlier suggestion of the source of K in the samples. Scatter plots (Fig. 2) showed inverse relationship between SiO
Plots of Fe
2
O
2
and with correlation coefficients Table 3.
3
with CaO, MgO, MnO and Na
2
O (Fig. 2) showed good relationship with all except Na
2
O. Linear trends on variation diagrams are considered to form consanguineous suites and trends that reflect more or less orderly chemical evolution of magma. Many samples appeared to have suffered from various degrees of alteration and would have been a result of the effects of metamorphism, deformation, element mobility as observed from variation diagrams of SiO
2
against selected major and trace elements.
538

5.00
4.00
3.00
2.00
1.00
0.00
2g 0.00
12.00
10.00
8.00
6.00
4.00
2.00
0.00
2e 0.00
5.00
5.00
0.25
0.20
0.15
0.10
0.05
0.00
2d 0.00
14.00
12.00
10.00
8.00
6.00
4.00
2.00
0.00
2a 40.00
20.00
50.00
SiO (%)
2
60.00
40.00
60.00
Res. J. Environ. Earth. Sci., 4(5): 534-545, 2012
10.00
15.00
12.00
10.00
8.00
6.00
4.00
2.00
0.00
2c 40.00
45.00
50.00
55.00
60.00
65.00
70.00
10.00
15.00
70.00
80.00
0.25
0.20
0.15
0.10
0.05
0.00
2h 0.00
12.00
10.00
8.00
6.00
4.00
2.00
2f
0.00
0.00
12.00
10.00
8.00
6.00
4.00
2.00
0.00
2b 40.00
5.00
5.00
50.00
10.00
10.00
60.00
15.00
15.00
70.00
Fig. 2: Harker variation diagrams, SiO
2
and Fe
2
O
3
plotted against selected major oxides
Plots in Fig. 2 showed that compatible major oxides such as MgO, TiO
2
, Fe
2
O
3
, MnO, CaO and Al
2
O
3
have normal, correlated and continuous differentiation trends as they decrease with increasing SiO
2
composition. It also suggested that certain minerals like olivine, pyroxene, magnetite and calcium plagioclase could be the major
539

Res. J. Environ. Earth. Sci., 4(5): 534-545, 2012
Table 3: Correlation coefficients of selected major elements
SiO
Fe
2
2
O
3
SiO
2
Fe
2
O
3
CaO
1 -0.90
-0.88
-0.58
-0.90
1 0.96
0.61-
0.66
0.74
CaO -0.88
0.96
1
MgO Na
2
O K
2
O
0.69 0.65
MgO -0.62
0.70
0.69
1
Na
2
O 0.80
-0.74
-0.65
-0.8
K
2
O 0.52
-0.54
-0.66
-0.50
MnO -0.85
0.96
0.91
0.68
-0.81
1
0.19
-0.78
0.52
-0.54
-0.66
-0.40
MnO
-0.85
0.96
0.91
0.68
10.19
-0.78
1 -0.39
-0.78
1 rocks but it may be comparable with those of basic igneous rocks (Kamp and Van De,1970). The Rb/Sr average ratio was 0.15 and the range was 0.03 to 0.66.
The mean ratio is below that for pelitic rocks but within those of basic rocks (Faure and Hurley, 1963). The ranges for Ba (214.2 to 2669.0) and Ce (9.0 to386.4) suggested basic rock characteristics for most of the samples since pelites normally have Ce values greater 60 ppm. Within the range of the Ce values, samples from Bongo Beo, Dua
Nayire, Adaboya, Sekoti and Kongo, had high Ce values suggesting these could be abnormal cases. fractionation phases during the magma evolution and did not alter very much during any metamorphism, (Lissan and Bakheit, 2010). Samples from the Kugri in the Garu-
Tempane were generally biotite-granodiorite and diorites of which K is a major element in mica and K-feldspar minerals. The plots of Fe
2
O
3
with CaO, MgO, Na
2
O and
MnO are presented in Fig. 2 and the correlation coefficients are given in Table 3 with many showing relatively high associations with each other.
Trace element geochemistry:
Main group trace elements: The main group trace metals were Rb belonging to the alkaline group while the alkaline-earths were Sr and Ba. The level of Rb ranged from 5.4 to 171.4 ppm while the other elements Sr and Ba ranged from 53.0-1752 and 206.0-2669.0 ppm, respectively (Table 4). The mean levels were 73.4, 690.0
and 999.3 ppm for Rb, Sr and Ba, respectively. The ratios of compositions of the trace elements of the samples with the corresponding mean values in the earth crust
(Krauskopf and Bird, 1995) were obtained to determine the level of enrichment. The mean ratio of Rb for all the samples was 0.82 which was less than unity suggesting less enriched. The range of the ratios was from 0.06-1.90
for Rb, 0.14-4.67 for Sr and 0.49-6.28 for Ba, respectively. The mean ratios for Sr and Ba were 1.84 and
2.35, respectively generally greater than 1.0. However, careful observation shows that most samples from Garu-
Tempane had ratio <1.0 for the elements in some cases.
Samples from the Bongo Granite were the most enriched in these elements. The ranges for Bongo were 0.65-1.90
for Rb, 1.21-6.28 for Ba and 1.41-4.67 for Sr. Sample 13 from Adaboya in Bongo was the most enriched sample in
Sr and Ba than the others. This is a granodiorite dominated mineralogically by K-feldspar, hornblende and quartz. The variation of these ratios could be attributed to
C
The type of minerals contained in the samples or suite,
C
The extent of deformation,
C Conditions of the geochemical environmental in which the samples were collected.
The contents Rb, Sr and Ba were generally less than
100 ppm with only few samples having Rb values above this 100 ppm. This is well below the range for pelitic
Transition elements: The main transition elements were
V, Cr, Co, Ni, Cu, Zn, Pb and Mo while the rare-earths or inner transition elements included Cs, La, Ce, Hf, Ta, Bi,
Th, U, Ga, Y, Zr and Nb. The compositions were compared with mean values of the earth crust (Krauskopf and Bird, 1995) by calculating their ratios. The ratios of
Co, Cr, Mo, Ni, Pb and Zn were higher while V, Ni and
Cu were lower than the earth crust. The levels of Cr, Co,
Ni and Zn were generally high with some showing high variations. In the rare-earth elements, depletions also occurred in Cs, La, Ce, Y, Zr and Nb while Hf, Ta, U and
Ga had ratios generally >1.0. However, in terms of relative enrichment, samples from the Bongo area were most enriched in the trace elements than other areas. All samples except those from Bongo Central and Bongo Beo
A were also relatively enriched in all the trace elements relative to the earth crust. The relative loss of the less mobile elements such as Nb and Y suggested that samples had undergone some early metamorphism or deformation of some extent. However, other trace elements including
Co, Cu and V are strongly correlated with SiO
2
content and was explained that these can replace some of the major elements during fractionation and deformation due to similarity in ionic radii. However, these elements as transition elements have similar ionic radius with Fe and therefore can replace it in some minerals of Fe.
Geochemical alteration of samples: The rock samples were physically observed showed signs of alteration as both colour and physical state were changed. In view of this, they were subjected to various analyses.
Lateritic sample: A decomposed rock purposefully collected from a hill near Kusanaba had SiO
2
and Al
2
O
3 as 28.83 and 14.99 wt%, respectively while the Fe
2
O
3
was
32.90 wt%. Compared with three other fresh rock samples collected from the same location had SiO
2
content ranging from 61.95 to 63.78 and Al
2
O
3
. 14.83 to 15.55 wt%; and
Fe
2
O
3
3.55 to 5.86 wt% and TiO
2
0.32 to 2.11 wt% with means of 62.66, 15.12, 4.33 and 0.42 wt%, respectively.
The SiO
2
content reduced from 62.66 wt% as a mean of three samples to 28.83 wt%, Fe
2
O
3
and TiO
2
contents
540

Res. J. Environ. Earth. Sci., 4(5): 534-545, 2012
Table 4: Trace element composition from rock samples from the study area
ID.
No Location V Cr Co Ni Cu Zn Ba Rb Sr Pb Mo Cs La Ce Hf Ta Bi Th U Ga Y Zr Nb
1 Yal
2 Datoku
3 Nyogwari
4 Sekoti A
42.3 75.3
19.0 10.0 33.3 142.7
678.7
72.1 569.4
9.4
1.0 2.6
11.5 17.5 3.6 4.4 0.4 2.3
2.0 17.8 3.9
140.7
51.3 66.7
18.3 10.6 19.8 83.3
501.6
21.5 784.8
6.7
1.0 1.4
14.4 28.0 5.3 3.8 0.4 2.0
2.0 18.3 9.1
216.9
2.5
3.5
22.3 675.8
6.2
5.3
13.9 76.2
219.1
141.0 2144.0 24.3 1.0 2.4
11.6 35.9 5.1 3.3 0.6 26.8 8.9 22.6 7.5
97.6
12.8
60.1 505.7
18.6 11.1 27.8 105.3
1016 120.5 751.2
17.9 1.0 4.4
48.1 129.9 6.7 4.3 0.6 9.6
5.6 21.4 10.8 206.9
5.9
5 Sekoti B
6 Kongo
143.9 300.7
24.4 9.5
43.8 237.9
670.5
45.3 567.2
8.1
2.6 1.5
24.4 47.9 4.0 5.5 0.7 4.7
2.0 18.6 15.
3107.7
4.9
42.7 114.1
21.6 7.8
21.8 104.1
1085.0 97.1 795.6
16.9 1.0 3.8
42.0 85.8 5.7 4.0 0.6 7.9
4.8 20.1 9.3
167.6
5.4
7A Bongo-beoA 118.3 449.7
30.2 26.1 34.3 114.2
808.6
99.3 667.4
9.5
2.7 1.2
31.4 91.7 4.6 4.7 0.8 6.3
3.0 19.4 18.9 215.8
17.3
7B Bongo-beo 163.7 434.9
37.8 41.1 12.3 154.3
515.9
58.8 714.3
8.6
0.9 1.5
15.7 43.2 5.2 4.1 0.9 1.6
2.0 19.4 16.9 177.8
6.5
8 Bongo-beo B 84.4 411.9
31.4 21.3 31.3 130.5
2387.0 171.4 1486.0 40.9 0.7 3.4
1078 320.2 15.7 5.3 0.8 23.4 6.6 19.4 28.5 566.6
9 Bongo-beo C 70.8 368.7
27.5 21.5 31.6 133.3
2448.0 170.6 1499.0 39.4 1.0 3.7
153.4 289.0 15.3 4.5 0.9 18.5 6.0 20.1 37.0 554.4
10 Bongo-beo D 94.6 64.1
38.2 27.8 41.0 186.4
2190.0 157.1 1372.0 40.9 0.7 2.1
159.0 386.0 17.3 4.9 0.5 41.2 9.5 20.3 49.6 664.0
11 Bongo cent 11.9 44.7
11.2 0.6
9.7
71.5
851.9
170.0 528.9
58.1 1.0 5.4
21.6 48.9 5.1 3.1 0.6 10.0 12.1 21.4 5.8
109.8
12A Dua nayire 69.7 500.3
25.5 9.5
19.4 126.7
2121.0 73.0 1720.0 28.9 0.6 3.2
109.7 268. 9.3 4.2 1.3 7.6
2.0 18.0 14.3 313.0
7.2
12B Dua nayire 62.8 342.6
25.6 12.6 21.2 172.4
2369 79.2 1688.0 31.9 1.0 2.2
101.7 183.4 7.5 4.4 0.7 7.2
2.0 17.8 21.8 290.9
7.7
13 Adaboya 83.0 729.0
32.6 27.6 17.0 149.0
2669.0 80.0 1752.0 18.5 0.8 2.6
124.0 266.3 9.6 6.3 0.7 12.2 2.1 17.5 19.9 383.8
7.5
14 Tamoka A 107.9 1001.0 46.5 315.3 36.1 126.8
655.7
47.2 435.1
8.2
0.4 1.5
18.2 34.6 3.9 6.2 0.4 5.2
3.7 17.4 17.7 132.8
8.3
15 Tamoka B 48.5 689.5
19.2 11.0 19.8 120.8
1147.0 67.4 289.8
7.1
0.5 1.5
33.9 64.2 5.1 3.8 0.6 11.3 2.0 15.6 12.1 182.2
6.9
18.0
15.9
19.7
6.4
16 Kusanaba 45.2 63.7
21.9 11.3 16.6 141.5
854.6
66.3 25.5
7.0
1.0 1.5
31.5 44.5 5.1 3.6 0.61 0.7
2.0 15.3 13.3 170.4
7.4
17 Kusanaba B 75.9 670 20.1 24.4 14.4 151.3
752.9
76.6 306.1
6.5
9.0 1.3
20.9 33.5 5.6 3.2 0.6 8.6
2.0 17.8 19.9 152.2
8.6
18 Kusanaba 46.9 154.7
26.1 6.5
30.2 128.8
1122.0 71.7 378.1
7.5
1.0 1.5
34.5 58.1 6.4 4.4 0.6 9.2
2.0 17.4 23.5 194.6
10.3
19 *Kusanaba 609.6 577.7
56.0 42.6 4.5
170.0
206.2
29.3 53.0
20.8 6.7 1.5
13.2 32.5 6.9 9.6 1.41 0.7
4.7 20.4 9.7
372.2
14.7
20 hill
Kugri west 80.9 76.1
28.9 19.1 34.2 146.9
562.5
21.5 736.0
4.7
1.0 1.5
22.5 40.2 6.8 4.8 0.6 2.0
2.0 19.2 8.2
259.9
21 Kugri west 33.4 92.7
18.0 3.7
9.7
77.3
837.1
35.9 906.0
7.6
1.0 1.7
20.2 36.4 5.1 3.3 0.6 2.0
2.0 18.0 4.2
132.7
22
23
Kugri west
Kugri hill
307.5 535.5
62.0 140.9 82.1 174.6
214.2
6.1
188.2
3.8
4.2 1.5
10.4 16.7 3.9 8.0 1.9 2.3
2.0 15.4 29.2 55.7
3.0
3.0
4.4
114.4 796.2
52.8 326.5 38.5 116.2
606.0
50.9 444.5
7.9
0.4 1.5
21.5 25.6 4.8 6.2 0.6 5.2
1.8 17.4 17.0 131.8
6.9
24 Nati
25 Nati
229.0 745.8
255.4 617.1
56.6 128.4 83.9 190.6
56.6 136.7 172.7 141.3
266.9
236.2
5.6
5.4
171.0
123.8
4.3
3.4
1.2 1.5
1.0 1.5
9.1
5.1
18.9 3.6 7.7 1.2 2.4
9.0
4.9 10.0 1.2 3.1
2.0 13.5 17.1 44.0
2.0 12.6 16.6 43.4
3.3
3.2
26 Red volta A 112.0 725.5
46.6 300.8 40.8 100.1
515.3
46.8 318.6
6.8
1.0 1.5
20.6 47.2 4.2 6.5 0.7 6.6
2.1 16.4 16.8 139.4
7.5
27 Red volta B 113.6 714.7
46.8 298.3 39.4 92.7
472.8
42.7 310.5
6.1
1.0 1.5
18.5 41.0 4.7 6.0 0.4 6.5
2.0 16.1 16.4 136.0
7.2
Mean
Minimum
Maximum
96.2 427.3
4.94 4.7
31.1 69.9 35.6 132.0
6.2
0.6
9.7
71.5
307.5 1001.0 62.9 326.5 172.7 237.9
1027.6 75.0 712.5
214.2
5.4
123.8
16.1 1.4 2.2
3.4
0.4 1.2
2669.0 171.4 1752.0 58.1 9.0 5.4
44.4 96.9 6.58 5.02 0.7 39.2 3.5 18.0 17.2 213.9
5.1
9.0
3.6 3.1 0.4 1.6
159.0 386.4 17.3 17.3 1.94 1.2
1.8 12.6 3.9
43.4
12.1 22.6 49.6 664.0
7.9
2.5
19.7
increased from mean values of 4.33 and 0.42 to 32.90 and
0.68 wt% giving ratios of 2.2, 7.6 and 1.6, respectively.
Only Al
2
O
3
content remained unchanged. The reduction of SiO
2
by a factor of 2.2 therefore suggested intense weathering had occurred since it is one of the least mobile elements to be removed during any alteration process. On the other hand, the more mobile elements including Na
2
O,
K
2
O, CaO and MgO were leached out to less than 0.4
wt%.
indicating the level of weathering. Also level of reduction of the mobile elements (Na, K, Ca and Mg) provides further evidence of the extent of weathering. Most of the other rocks had CIA values ranging from 70 to 125% was indicative of weathering.
Chemical alteration index: Quantitative estimation of the extent of weathering of all the rocks was examined using the Chemical Index of Alteration (CIA) suggested by Nessbitt and Young (1982). The CIA is calculated using the molecular proportions as follows; CIA =
[Al
2
O
3
*100/Al
2
O
3
+CaO+Na
2
O+K
2
O]. The CaO content was assumed to be derived from silicate fraction since carbonate and apatite were negligible. Fresh rocks or minerals such as albite, anorthite or K-feldspars have CIA up to 50%, fresh basalts have between 30 and 45% while granite and granodiorites range from 45 to 55% and fresh muscovite having values up to 75%. Clay minerals which are weathered products of fresh rocks have higher values, illites and montmorillonites have a range from 75 to 85%, kaolinites have up to 100% (Nessbitt and Young, 1982).
These values suggest that the higher the CIA value the more weathered the rock. The CIA values obtained in this study ranged from 50.5 to 865. The ferricate sample from
Kusanaba in Bawku West had the highest CIA value
Evolutionary relationships:
Variation diagrams: The samples are derived from the
Birrimian metavolcanics and granite intrusions in which trace elements can be used to provide information of their origin. The composition of these samples was used to construct discrimination and variation diagrams in order to determine their origin. Alfred and Michael (1989) had showed that major element chemistry can be used with selected trace and rare-earth elements to show indicative characteristics despite their limited validity in classification schemes for altered and metamorphosed volcanics. From the range of values of the major element presented earlier the contents of SiO
2,
MgO, Fe
2
O
3
and
MnO vary widely suggesting diverse protoliths. The generic relationship of these samples with basalts was obtained using CaO and MgO compositions which were calculated according to Pearce (1976) since basalts composition normally fall within the range from 12 to 20 wt%. Most samples were found to be outside this range;
12%<CaO+MgO<20 wt% and therefore no relationship with basalts. However, only samples from Kugri, Tamoka and the two samples from Red Volta River at Nangodi n this range. Plots of MgO/CaO against P
2
O
5
/ TiO
2
541

1.20
1.00
0.80
0.60
0.40
0.20
0.00
0
70.00
65.00
60.00
55.00
50.00
45.00
40.00
35.00
0.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
0.00
1.80
1.60
1.40
1.20
1.00
0.80
0.60
0.40
0.20
0.00
0.00
0.50
1.00
200
(c)
2.00
Res. J. Environ. Earth. Sci., 4(5): 534-545, 2012
13
20
21
22
2
24
6
12B
9
5
8
7
7B
10
16
1
4
18
17
11 15
25
12A
3
14 23
0.50
2.00
1.00
1.50
MgO/CaO
(a)
26
27
2.50
1.00
Nb/Y
1.50
(b)
400
Zr (ppm)
3.00
600
2.00
2.50
4.00
800
(d)
Fig. 3: Variaation diagrams for samples in the study area
(Fig. 3a) and TiO
2 against Zr/P
2
O
5
(Fig. 3b) were also used and most samples plotted in tholeiilite field. The Zr verses P
2 plot also supported that the samples are not basalts.
O
5
(3c)
The samples also showed high alumina content falling in a range classified by Lissan and Bakheit (2010) as calcalkaline and according to Peacock alkali index, the samples were between alkali and calc-alkali with very few being calcic (SiO
2
>61 wt%). However, SiO
2
against Nb/Y
(Fig. 3d) showed that all but three samples plotted in the sub-alkaline field. The Fe
2
O
3
content seemed to be relatively high with most samples ranging between 3.17
and 13.25 wt% and only few samples having less than 3 wt%. The Fe
2
O
3
/MgO ratio was between 0.65 and 2.06
and many were less than 2.0 reflecting a high availability of opaque phases.
The plot of SiO
2
against Na
2
O+K
2
O (Fig. 4a) showed that all the samples fell within andesites, dacites and their derivatives. This plot also indicated that all the samples were sub-alkaline (Irvine and Barager, 1971) and is consistent with the order plots in Fig. 3. Furthermore the
K
2
O against SiO
2
plot (Fig. 4b) showed that all samples contained high K
2
O and between thoeleiitic and calcalkaline and therefore was in conformity with literature that the petrochemical composition of metavolcanic rocks fall within the calc-alkaline area as supported by
Na
2
O/K
2
O ratio. The Na
2
O/K
2
O ratios were between 1 and 3 except two samples which were slightly above 3.0.
These values are low according to typical values obtained by Jakes and White (1971) for calc-alkaline rocks hence the samples were more thoeleiitic. However, the low TiO
2
(<1) wt% supported that the samples are within the calcalkaline range. The CaO content on the hand was relatively high with most samples having a range above
3.0 to less than 10 wt% suggesting the availability Caderived minerals in some of them. This could partly due to the availability of carbonates and weathering as shown earlier (Edmonds, 1956). However, Jakes and White
(1971) suggested that a range above 4.55 wt% may indicate the presence of epidote and a non-intensive metamorphism. Hence the samples were found to be thoeleiitic in origin. There were few samples which were outside the sub-alkaline area (Fig. 4A) suggesting that they may contain high Na-and K-rich minerals. The alumina saturation was also calculated to provide further evidence on the type of minerals and the possible source of magma. The Alumina Saturation Index (ASI) =
Al
2
O
3
/CaO+Na
2
O+K
2
O, for all the samples had ratios less than 1 except four (16, 17, 18 and 21). The four samples were just marginally >1 which could be attributed to possible experimental error. The ratio Al of all the samples showed Al
2
O
3
>Na
2
2
O
3
O+K
2
/Na
2
O+K
2
O
O. The ASI values indicated that the Al abundance was generally lower and therefore Na
2
O+K
2
O+CaO was enough to form feldspars. However, the Al/Na
2 than Na
2
O+K
2
O+K
2
O ratios were generally >1 suggesting that the rocks had higher Al
2
O
3
O and therefore other aluminosilicates formation was possible. The samples were also classified according to the alumina content based on that of Keith et al . (1991) of which three samples were strongly
542

Res. J. Environ. Earth. Sci., 4(5): 534-545, 2012
(a)
6
5
4
High K
3
2 Medium K
1
0
45 50 55
(b)
SiO
2
60
Low K
65 70
Fig. 4: Chemical composition based on alkali composition of samples metaluminous with ASI<0.65 which were Kugri Hill
West and two from Nati. Two samples Tamoka B and
Kusanaba B had ASI>1.1 and were strongly peraluminous.
Majority of the samples were within the range
0.65<ASI<1.0 and thus metaluminous. It was also noted that 8 samples were outside the range of 0.65 to 1.0 but the values of Al
2
O
3
/Na
2
O+K
2
O indicated that these samples were metaluminous. However, five other samples were within the range of peraluminous. None of the samples had Al
2
O
3
/Na
2
O+K
2
O<1. It is known that samples containing high aluminous content where ASI>1 are likely to contain mica, corundum, hornblende, tourmaline, topaz, Fe-Mn garnet, cordierite and sillimanite as the major minerals while ASI<1 and
Al
2
O
3
/Na
2
O+K
2
O>1 also contain hornblende, aluminous augite, melilite, biotite or non-aluminous phase (Nelson,
2011). From the analysis, most samples are within 0.65 to
1.0. A few had ASI>1 may contain hornblende, mica, biotite, corundum, aluminous augite and possibly garnets, melilite and sillimanite as the dominant minerals.
Other discriminant diagrams were constructed for further classification using trace elements. Plots immobile element ratios were also used (Nb/Y against Zr/TiO
2
)
(Fig. 5a), (Winchester and Floyd, 1977) to further determine the sources of samples; some samples fell in the andesite and the basalt/andesite fields. The TiO
2
/P
2
O
5 ratio ranged from 1.24-9.00 was within the range from
4.52-10.45 as suggested by Sharker Ardakani et al . (2009) who showed that this range produces a transitional thoeleiitic nature. SiO
2
plot against TiO
2
(Winchester and
Max, 1984) (Fig. 5a) and P
2
O
5
/TiO
2
against MgO/CaO
543

1000.00
100.00
10.00
1.00
10.00
25.0
20.0
15.0
10.0
0.50
0.00
35.00
2.40
1.60
0.80
0.00
0.00
1.00
1.10
0.01
0.00
0.01
(a)
7
22
7B
25 24
45.00
10
8
9
5
23
12A
13
17
215
61
0.64
4
16
3
55.00
65.00
75.00
(b)
Res. J. Environ. Earth. Sci., 4(5): 534-545, 2012
100.00
Cr (ug)
1000.00
10000.00
(Fig. 3a) (Werner, 1987) were also used to identify the source of origin. In Fig. 3a and 5a four samples (7a, 8, 9 and 10) were outside the magmatic range while others plotted within the magmatic region. The four samples were located at Bongo Beo and 12A from Dua Nayire.
The sample 12b from Dua Nayire lies also just below the trend line. These two samples are classified as trachyandesite and trachydacite respectively. With the four samples, 7A is classified as trachybasalt, 8 and 10 are trachyandesites and 9 is trachydacite (Fig. 4a).
Furthermore Ni and Cr diagram (Fig. 5b) showed five samples plotted on the basalt field while majority were outside suggesting that they are not basaltic supporting the earlier finding. However, Cr/Ni ratios in the samples ranged for 2.31 to 127.51 which are comparatively higher than the accepted ratio (2.24) for rocks originating from basaltic origin. Trace elements such as Ba, Cr, Ni, Sr, Y and Zr showed no clear variation with SiO
2
. These appeared to remain unchanged suggesting that they were probably immobile during metamorphism and other alteration processes (Lissan and Bakheit, 2010). The ratios for Y/Nb fall with the range 0.57 to 6.64, a similar range found by Lissan and Bakheit (2010) in their study in northern Sudan (0.83-5.75). Most samples in this study had Nb/Y<1.
The study of Garcia (1978) and others showed that
La/Th ratio was 5-30.3 which implied an approach to calc alkaline and thoelitic affinities. From this study, La/Th ratios ranged from 0.3 to 7.29 suggesting that the samples can be classified as tholeiitic group.
CONCLUSION
0.50
0.10
evolutionary trends
1.00
Zr/P O
5
(c)
1.00
Nb/Y
(d)
1.50
10.00
2.00
The mineralogical and chemical compositions of the rocks differ from the granites in Bongo to hornblende amphibolites in the Bawku West/Garu-Tempane area. The
K
2
O/Na
2
O ratio discriminates the Bongo granites from the other rocks with a relatively higher ratio while the
CaO/Na
2
O ratios were higher in the samples from eastern corridor than those in Bongo and Tongo. Rocks from the
Garu-Tempane were richer in CaO and MgO derived from ferromagnesian minerals. Most samples were found to be weathered on the high CIA values obtained. The concentrations of most of the trace elements were found to be relatively higher than the levels in earth crust. The main group trace elements Sr and Ba were relatively higher while Rb mean concentration was lower than the earth crust. Most of the main transition elements Co, Cr,
Mo Pb and Zn were higher while V, Ni and Cu were lower than the earth crust. In the inner transition elements, only Cs, Y and Nb had concentrations lower than the earth crust while Bi, Ce, Ga, Hf, La, Ta, Th, U and Zr were relatively higher. Discriminant diagrams showed that the samples were of magmatic origin and that they were mainly andesites, dacites, trachytes, trachyandesites
544

Res. J. Environ. Earth. Sci., 4(5): 534-545, 2012 and trachydacites. Aluminium saturation index revealed that most samples were metaluminous with only a few being peraluminous and therefore basic in character. Most samples were found to be tholeiitic in character.
ACKNOWLEDGMENT
I wish thank Mr Mathias Akamba of the Faculty of
Mathematical Sciences for helping to produce some of the graphical work in this study. Also my appreciation goes to Mr Gregory Kpazou Pelig-Ba for producing the map.
My former driver, Mr Rahaman Sullemana was of tremendous help for assisting to collect the rock samples when we were in the field.
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