Field mapping report 2015 group one
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Contents
ACKNOWLEDGEMENT...............................................................
Field mapping report 2015 group one
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ACKNOWLEDGEMENT
We first thank the Almighty God for his guidance and protection duri...
Field mapping report 2015 group one
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ABSTRACT:
Geological field mapping is the process of obtaining surface and sub-surfa...
Field mapping report 2015 group one
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INTRODUCTION:
In June 2014, mapping was done around the northern part of Kumasi in t...
Field mapping report 2015 group one
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CHAPTER 1. BACKGROUND OF STUDY AREA
1.1 LOCATION:
Located in the northern part of Ku...
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CHAPTER 2. MAPPING EQUIPMENT AND PROCEDURE
2.1 EQUIPMENT AND TOOLS USED
The equipmen...
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2.2 MAPPING PROCEDURE
The following procedure was used during the field mapping exer...
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CHAPTER 3. MAPS AND SECTION
3.1 BASE MAP
A base map of the area was provided for the...
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Fig 3 Outcrop map
3.5 STRUCTURAL MAP
A map showing the structural measurements recor...
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3.6 GEOLOGICAL MAP
The primary aim of the mapping exercise is to produce a geologic...
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3.7 CROSS SECTION
We took a cross section along 6 ̊ 47’ from “A” to “B” as shown on...
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CHAPTER 4. GEOLOGICAL SETTING
4.1 REGIONAL GEOLOGY
Regionally, the area is in the A...
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4.4 STRUCTURES:
The major geological structures encountered were joints. Some of th...
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Rose diagram showing general strike direction of quartz veins (NE-SW)
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Rose diagram showing general strike of pegmatite veins (almost N-S).
4.5 IGNEOUS AC...
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4.6 METAMORPHISM:
The presence of phyllite in and around Dabaa, Kapro and Kumi is a...
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CONCLUSION
The area is underlain by three major rock types, thus, fine grain granit...
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APPENDICES
APPENDIX ONE: SAMPLE IDENTIFICATION
SPECIMEN PICTURE COLOUR TEXTURE MINE...
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TA
099/14
Grey, Fine
grained and
Foliated
Mica and Chlorite Phyllite
TA
032/14
Ligh...
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APPENDIX TWO: ATTITUDES OF STRUCTURES FOR ROSE PLOTS
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The geology of aframtwo, dabaa, wioso and their environs in the ashanti region of ghana

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by KNUST geological eng. students, 2014, G1, led by Anyintuo Thomas Becket

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The geology of aframtwo, dabaa, wioso and their environs in the ashanti region of ghana

  1. 1. Field mapping report 2015 group one 1 Contents ACKNOWLEDGEMENT..........................................................................................................................................2 ABSTRACT:............................................................................................................................................................3 INTRODUCTION:...................................................................................................................................................4 CHAPTER 1. BACKGROUND OF STUDY AREA.......................................................................................................5 1.1 LOCATION:..................................................................................................................................................5 1.2 TOPOGRAPHY:............................................................................................................................................5 1.3 CLIMATE:.....................................................................................................................................................5 1.4 VEGETATION:..............................................................................................................................................5 1.5 DRAINAGE...................................................................................................................................................5 1.6 LAND USE....................................................................................................................................................5 CHAPTER 2. MAPPING EQUIPMENT AND PROCEDURE.......................................................................................6 2.1 EQUIPMENT AND TOOLS USED..................................................................................................................6 2.2 MAPPING PROCEDURE...............................................................................................................................7 CHAPTER 3. MAPS AND SECTION.........................................................................................................................8 3.1 BASE MAP...................................................................................................................................................8 3.2 TRAVERSE MAP ..........................................................................................................................................8 3.4 OUTCROP MAP...........................................................................................................................................8 3.5 STRUCTURAL MAP......................................................................................................................................9 3.6 GEOLOGICAL MAP....................................................................................................................................10 3.7 CROSS SECTION ........................................................................................................................................11 CHAPTER 4. GEOLOGICAL SETTING....................................................................................................................12 4.1 REGIONAL GEOLOGY................................................................................................................................12 4.2 ECONOMIC GEOLOGY: .............................................................................................................................12 4.3 STRATIGRAPHY:........................................................................................................................................12 4.4 STRUCTURES:............................................................................................................................................13 4.5 IGNEOUS ACTIVITY:..................................................................................................................................15 4.6 METAMORPHISM:....................................................................................................................................16 CONCLUSION ......................................................................................................................................................17 RECCOMMENDATION ........................................................................................................................................17 REFERENCES........................................................................................................................................................17 APPENDICES........................................................................................................................................................18 APPENDIX ONE: SAMPLE IDENTIFICATION....................................................................................................18 APPENDIX TWO: ATTITUDES OF STRUCTURES FOR ROSE PLOTS .................................................................20
  2. 2. Field mapping report 2015 group one 2 ACKNOWLEDGEMENT We first thank the Almighty God for his guidance and protection during the course of the field mapping. Our sincere gratitude also goes to the lecturers who were with us on the field during the mapping process. We also thank Dr S. K. Y Gawu, and Madam Lydia for providing necessary guidance during the preparation of our maps and report. This field mapping exercise would not have been the same without your selfless commitment. We also wish to express our sincere appreciation to the teaching assistants for their help and solid illustrations on rock analysis.
  3. 3. Field mapping report 2015 group one 3 ABSTRACT: Geological field mapping is the process of obtaining surface and sub-surface information on rock types underlying the different parts of a terrain as well as significant features such as faults, fold structures, mineralization zones, etc. Our geological field mapping exercise was carried out at Adankwame, Afrantwo and their environs covering 1 ̊37 ̍40’’ - 1 ̊45 ̍W and 6 ̊45 ̍ - 6 ̊48’38’’N on the base map. Samples from outcrops encountered on the field were taken to the laboratory for further analysis. Information obtained from the field and laboratory was used to produce a geological map of the area. From the analysis made it can be inferred that the area mapped is generally underlain by granitoids, as lithological materials encountered were mainly intrusive igneous rocks.
  4. 4. Field mapping report 2015 group one 4 INTRODUCTION: In June 2014, mapping was done around the northern part of Kumasi in the Ashanti Region of Ghana covering 1 ̊37’40’’ - 1 ̊45 ̍W and 6 ̊45 ̍ - 6 ̊48’38’’N. The area assigned to our group was traversed using the roads and footpaths on the base map. During traversing, detailed description and attitude measurement of geological structures, outcrops and exposures were recorded in field notebooks. Samples of outcrops were taken to the laboratory for further analysis. The aim of this field mapping exercise is to enable students to obtain the necessary practical knowledge needed for the job world in the identification of geological structures, outcrops and exposures, the measurement of the attitudes of structures in these outcrops and exposures and using acquired field information and their theoretical knowledge to produce a geological map. This report gives a detailed overview, of all activities and information gathered over the two week period spent studying the geological features present at Afrantwo, Adankwame, Dabaa, Wioso and their environs. It also encompasses results from the laboratory analysis of the samples taken from this area. It should however be noted that laboratory analysis as mentioned throughout this report refers to only the physical analysis of rock samples, as Petrographic and Chemical analysis could not be made due to lack of necessary instrumentation.
  5. 5. Field mapping report 2015 group one 5 CHAPTER 1. BACKGROUND OF STUDY AREA 1.1 LOCATION: Located in the northern part of Kumasi in the Ashanti Region of Ghana covering 1 ̊37 ̍40’’ - 1 ̊45 ̍W and 6 ̊45 ̍ - 6 ̊48’38’’ ̍N. 1.2 TOPOGRAPHY: The area has alternating highlands and lowlands. The highlands are mostly to the east of the mapped area. 1.3 CLIMATE: The climate is that of the semi-equatorial belt characterised by double rainfall maxima occurring in July and November. The dry season occurs between December and April and is associated with drought conditions. Temperature is found to be uniformly high all year round with a mean annual temperature of 26 ̊c. (www.ghanadistricts.gov.gh) 1.4 VEGETATION: Mostly semi-deciduous forest comprising open forests and closed forests. However most of the original forest has degenerated into secondary forest and grassland due to indiscriminate felling of trees and poor farming practices. (www.ghanadistricts.gov.gh) 1.5 DRAINAGE The area is well drained. The drainage patterns are mostly sub-dendritic. 1.6 LAND USE The most common use of land in the area is for agricultural purposes. Common crops include maize, cassava and plantain. Also, the exposed granitoids are being quarried for aggregates.
  6. 6. Field mapping report 2015 group one 6 CHAPTER 2. MAPPING EQUIPMENT AND PROCEDURE 2.1 EQUIPMENT AND TOOLS USED The equipment and tools used during the field mapping exercise include; base map for the mapping exercise. This had prominent features such as roads, footpaths, schools, churches, etc. which aided in the determining of our positions on the field. The traverse, structural, outcrop and geological maps were all drawn on the base map. Compass and clinometer for measuring attitudes (dip and strike) of structures on the field. hammer for breaking the rocks as samples and also to expose fresh surfaces. Hand lens to examine the mineral grains of the rocks more closely. Field notebook for recording information and observations, such as, strike and dip values, outcrop description, sample names, etc. Markers for the marking and naming of the samples. Field bag for holding samples. Camera for taking photographs of the outcrops and other significant features. Fig. 1. Some of the equipment used during the mapping exercise.(measuring tape, compass, hand lens, geological hammer, cutlass, field notebook, from left)
  7. 7. Field mapping report 2015 group one 7 2.2 MAPPING PROCEDURE The following procedure was used during the field mapping exercise; along roads and footpaths to find outcrops and/or exposures. We would traverse the nearby bushes if outcrop or exposures are rare to find along the roads. etermine the location coordinates of the outcrop or other feature using the GPS. easily recognisable minerals, and suggest a field name for the outcrop in our field notebooks. attitude measurements of the structures in the outcrop, noting which structures they are. ure to aid future analysis. We took fresh samples of the outcrop or exposure for further analysis to confirm the field name or otherwise.
  8. 8. Field mapping report 2015 group one 8 CHAPTER 3. MAPS AND SECTION 3.1 BASE MAP A base map of the area was provided for the exercise. It simply shows geographic features of interest and relief of areas, using contours. It is the base on which the other maps were developed. 3.2 TRAVERSE MAP This map was developed to show the route of traverse in the field. The paths of each day were differentiated using different colours. Fig 2 Traverse map 3.4 OUTCROP MAP It shows the locations of outcrops seen in the field. The different types of outcrops were also differentiated using colours. (Yellow for metasediments, pink for fine grain granitoids and purple for coarse grain granitoids)
  9. 9. Field mapping report 2015 group one 9 Fig 3 Outcrop map 3.5 STRUCTURAL MAP A map showing the structural measurements recorded on the field. Since these structures are usually taken on outcrops, their locations should coincide with the locations of outcrops on the outcrop map. Fig 4 Structural map
  10. 10. Field mapping report 2015 group one 10 3.6 GEOLOGICAL MAP The primary aim of the mapping exercise is to produce a geological map of the area and write a report. The geological map shows the rock units underlying the area. It is essentially a combination of the outcrop map and the structural map. The similar rock outcrops are connected and boundaries of different rock units are shown or inferred where they were not seen on the field. Fig 5 Geological map
  11. 11. Field mapping report 2015 group one 11 3.7 CROSS SECTION We took a cross section along 6 ̊ 47’ from “A” to “B” as shown on the geological map. The cross section shows the progression of rock units in moving from “A” to “B”. Fig 6 Cross section at 6047'
  12. 12. Field mapping report 2015 group one 12 CHAPTER 4. GEOLOGICAL SETTING 4.1 REGIONAL GEOLOGY Regionally, the area is in the Ashanti uplands. The geology is that of the lower Birimian series. The lower Birimian forms part of the Birimian system. The Birimian system is one of the units forming the West African cratonic region. The Birimian terrains in the West African craton are a mixture of highly metamorphosed volcanic and plutonic rocks with low grade metavolcanic and metasediments. The Birimian is divided into the older “lower Birimian”, consisting of predominantly metasedimentary rocks, and a younger “upper Birimian”, consisting chiefly of metavolcanic rocks. Our area falls within the Lower series which consist of metasedimentary rocks mainly phyllites, greywackes. Also associated are intrusives of felsic (granitic and granodiorite) and mafic (dolerite) compositions. 4.2 ECONOMIC GEOLOGY: The granitoids of the area are suitable for use as aggregates for construction. There is a quarry, operating on the Achinsi classification range. The phyllite can also be used for decoration purposes. 4.3 STRATIGRAPHY: The major rock units encountered were the birimian granitoids and metasediments. From the principle of original horizontality, sediments would be laid horizontally or almost horizontally. The fact that the sedimentary rocks have been metamorphosed and also inclined provide evidence of deformation. The metamorphism was most likely due to heat from a magmatic intrusion. The intrusion could also be the cause of the dipping nature of the metasediments. Combining these, we can infer that sedimentary rocks were laid, they got intruded by the granitoids. The force of the intrusion disturbed the sedimentary beds, causing them to incline. The heat from the magma metamorphosed the sedimentary rocks. There are two types of granitoids, differentiated on the basis of grain size into coarse grain and fine grain types.
  13. 13. Field mapping report 2015 group one 13 4.4 STRUCTURES: The major geological structures encountered were joints. Some of the joints have provided space for vein intrusions. Some of the veins were quartz and others were pegmatite veins. The joints strike in the North – East direction, generally. The foliations of the metasediments strike in the North – East direction and dip generally in the North – West. Stereo plot of foliation strike showing a general direction of NE-SW.
  14. 14. Field mapping report 2015 group one 14 Rose diagram showing general strike direction of quartz veins (NE-SW)
  15. 15. Field mapping report 2015 group one 15 Rose diagram showing general strike of pegmatite veins (almost N-S). 4.5 IGNEOUS ACTIVITY: The most prominent igneous bodies are the granitoids. There were quartz and pegmatitic vein and veinlet intrusions in both the fine and coarse grained granitoids. Fig.2. Granitoid with quartz and pegmatite intrusions at Asuofua.
  16. 16. Field mapping report 2015 group one 16 4.6 METAMORPHISM: The presence of phyllite in and around Dabaa, Kapro and Kumi is an evidence of a medium grade metamorphism. Again there were areas in Ntiribuoho and Nkukua where the minerals in the granitoids have started aligning themselves. Thus, the area is moderately metamorphosed. Fig.2. Outcrop of phyllite seen near Dabaa.
  17. 17. Field mapping report 2015 group one 17 CONCLUSION The area is underlain by three major rock types, thus, fine grain granitoids, coarse grain granitoids, and metasedimentary rocks (phyllite). The granitoids intruded original sedimentary rocks, metamorphosing them. Therefore, even though the area appears dormant and stable at present, it must have undergone remarkable igneous activity in the past. RECCOMMENDATION 1. The pre-mapping training should done over a longer duration to allow students to really grasp the concepts of mapping, especially determining attitudes of structures. REFERENCES 1. GEOLOGY AND MINERAL DEPOSITS. Ghana Ministry of lands forestry and lands (Mines section). Retrieved 2009-03-17. 2. “Geological evolution and metallogeny through the Birimian”. (PDF). Prospectors and Developers Association Canada.2009. Retrieved 2009-03-17. 3. J.P. Miles, P. Ledru, P. Ankrah, V. Johan, E. Marcoux and Ch. Vinchon. “The metallogenic relationship between Birimian and Tarkwaian gold deposits in Ghana”. SpringerLink. Retrieved 2009-03-16. 4. www.ghanadistricts.gov.gh (website), accessed on 8th April, 2015.
  18. 18. Field mapping report 2015 group one 18 APPENDICES APPENDIX ONE: SAMPLE IDENTIFICATION SPECIMEN PICTURE COLOUR TEXTURE MINERAL COMPOSITION ROCK NAME TA 050/14 Black, white Fine to medium interlockin g grains Quartz, Biotite and Feldspar Basin type granitoid (felsic) TA 140/14 Black, white Medium to coarse interlockin g grains Biotite, Feldspar and Quartz Basin type granitoid (felsic) TA 136/14 White, black Medium to coarse interlockin g grains Biotite, feldspar Quartz and muscovite Basin type granitoid (felsic)
  19. 19. Field mapping report 2015 group one 19 TA 099/14 Grey, Fine grained and Foliated Mica and Chlorite Phyllite TA 032/14 Light grey with dark specks Fine interlockin g grains Biotite, muscovite, feldspar and Quartz Basin type granitoid (felsic) TA086/ 14 Milky white glassy Quartz quartz
  20. 20. Field mapping report 2015 group one 20 APPENDIX TWO: ATTITUDES OF STRUCTURES FOR ROSE PLOTS
  21. 21. Field mapping report 2015 group one 21

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