1. THE GEOLOGY OF
AKOSOMBO AND ITS
ENVIRONS
Presented by
Group 3
ADUNGAH GIFTY
ADU-KUMI JAEL ABENA YEBOAH
YUSSUF OLAMIDELE
HOPE EDITH
UCHEGBU UCHENNA DANIEL
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2. CONTENT
 INTRODUCTION
 AIMS AND OBJECTIVES
 STUDY AREA AND PHYSIOGRAPHY
 GEOLOGICAL SETTING
 METHODOLOGY
 LITHOLOGIES
 STRUCTURES
 GEOCHEMICAL RESULTS AND DISCUSSION
 DISCUSSION
 CONCLUSION
 REFERENCES
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3. INTRODUCTION
 The mapping exercise was commenced on the 22nd of June
2015, and was concluded on the 1st of August 2015.
 Area of Land Mass: 36.805km²
 Geographical Coordinates: longitudes 000’0” to 004’53.48” and
latitudes 6015’ 14.59” to 6017’48.65”
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4. AIMS AND OBJECTIVES
 To identify and establish the relationship of the various
lithologies in the study area.
 To produce a detailed geological map of the study area.
 To infer the evolutionary history of the rocks
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5. STUDY AREA/PHYSIOGRAPHY
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6. GEOLOGICAL SETTING
 The Dahomeyide orogen exposed in south eastern Ghana is the
southern segment of the 2500km long Trans-Saharan belt which
defines the eastern margin of the West African Craton. (Attoh and
Nude, (2008). Cited therein)
 The study area falls within the Togo and Buem structural units of
the Dahomeyide.
 Lithologies of study area are Quartzite, Phyllite and Sandstone
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7. METHODOLOGY
 Pre-field
 Main Field.
 Post-field
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8. TRAVERSE MAP 8

9. LITHOLOGIES
 Light grey in colour
 Coarse grained
 Composed mainly of quartz.
 Thickly foliated.
9
NAME OF ROCK: QUARTZITE

10. A Photomicrograph of showing the mineralogic composition of
Quartzite. (XPL)
10

11. 11
MINERALS ABUNDANCE ( %)
Quartz 98
Lithic Fragments 2
Modal Abundance
A Photomicrograph Showing Micro vein in Quartzite. (XPL)

12. 12
 variegated colours.
 Very fine grained.
 Thinly foliated.
 Quartz, micas
NAME OF ROCK: PHYLLITE

13. 13
 Purple to brown in
colour.
 Medium grained.
 Dominated by quartz
 Cement present.
NAME OF ROCK: SANDSTONE

14. SUBLITHARENITE 14
A Photomicrograph of Sublitharenite under XPL

15. FELDSPATHIC SANDSTONE 15
A Photomicrograph Showing minerals in Feldspathic
Sandstone

16. MINERALS ABUNDANCES (%)
Quartz 67
Orthoclase 13
Sericite 9
Plagioclase 7
Lithic Fragments 4
Opaque minerals 1
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17. OUTCROP MAP 17

18. STRUCTURES
 Geological structures observed in the field have
been grouped into primary and secondary
structures.
PRIMARY STRUCTURES
 Ripple marks
 Bedding
 Lamination
SECONDARY STRUCTURES
 Foliations
 Folds
 Joints
 Quartz veins
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19. RIPPLE MARKS IN
QUARTZITE
BEDDING AND
LAMINATIONS IN
SANDSTONE
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20. QUARTZ VEINS IN
QUARTZITE.
JOINTS IN THE
QUARTZITE
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21. PHYLLITIC FOLIATION
21
FOLIATIONS IN THE
QUARTZITE

22. FOLD IN QUARTZITE.
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23. STEREOGRAPHIC PLOTS
OF BEDDING PLANE
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24. STEREOGRAPHIC PLOTS FOR
THE FOLIATIONS.
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25. JOINTS IN THE QUARTZITES
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26. STRUCTURAL MAP
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27. GEOCHEMICAL RESULTS
AND DISCUSSION
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28. 28
MAJOR ELEMENTS
CONCENTRATIONS (WT%)

29. 29TRACE ELEMENTS IN PPM

30. SEDIMENT CLASSIFICATION
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Classification Diagram after Herron,(1988).

31. PROVENANCE
31
Provenance discrimination diagram after Roser and Korsch ,
(1986).

32. TECTONIC SETTING
32
Discrimination function Diagram after Roser and
Korsch, (1986).

33. SOURCE AREA WEATHERING
33
The Al2O3-(CaO+Na2O)-K2O ternary diagram after
Nesbitt and Young,(1984).
Average CIW =88.31
Average PIA =49.27
Average CIA= 71.8

34. SOURCE AREA CLIMATE
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35. REES AND EUROPIUM ANOMALY
35
Normalized Chondrite Diagram after
Boynton, (1984)
Average Eu Anomaly: 0.501
Rb/Sr > 2

36. DISCUSSION CONT‘D
 Lithologies encountered in the study area are Quartzite, Phyllites and
Sandstones.
 Large scale deformation may be inferred from the distinctive trends
observed in the rocks.
 The Joints and Quartz veins may suggest brittle deformation and
Metamorphism.
 Folds in the rocks may have formed from compressional forces and
indicate ductile deformation.
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37.  Quartz exhibits undulose extinction which suggests that the rock
mat have undergone deformation.
 The suturing of grains indicate recrystallization and
metamorphism.
 The grain shape, sorting and composition of the sandstones
indicate that they haven‘t been transported far from their source.
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38. COMPOSITE GEOLOGICAL MAP
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39. CROSS SECTION 39

40. PROPOSED STRATIGRAPHY
DOMAIN ROCK TYPE
BUEM
THRUST FAULT
TOGO
SANDSTONE
QUARTZITE
PHYLLITE
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41. CONCLUSION
 The study area falls within the Togo and Buem units of the
Dahomeyide.
 Rock types observed are Quartzites, phyllites and sandstones.
 The phyllites are the oldest rocks, with the quartzites being of
intermediate age and the sandstones being the youngest.
 The general trend of the rocks is in the NE-SW.
 Sediments were sourced from a quartzose sedim
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42. REFERENCES
 Attoh, K., Nude, P. M. (2008). Tectonic significance of carbonatite and
ultrahigh-pressure rocks in the Pan-African Dahomeyide suture zone,
southeastern Ghana, From: ENNIH, N. & LIE´GEOIS, J.-P. (eds) The
Boundaries of the West African Craton. Geological Society,
London,Special Publications, 297, 217–231. DOI: 10.1144/SP297.10 0305-
8719/08/$15.00 # The Geological Society of London 2008.
 Herron, M., (1988). Classification of terrigenous sands and shales from
core or log data-Journal of sedimentary research.
 Nesbitt, H.W. and Young, G.M. (1982). Early Proterozoic climates and
plate motions inferred from major element chemistry of lutites. Nature
299, 715–717
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43. REFERENCES
 Roser, B. P. and Korsch, R. J. (1988). Provenance signatures
of sandstone-mudstone suits determined using
discriminant function analysis of major-element data.
Chem. Geol. 67, 119–139 ((
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44. THANK YOU!
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