Academia.eduAcademia.edu

Figure 3 – uploaded by sciepub.com SciEP

See full PDFdownloadDownload figure
Table 5. List of rock samples used for petrographic investigation Laboratory microstructural investigation of thin sections of rock units of the study area are complementary to the study of the surface structure. The following are brief descriptions of the microscopic investigation of the dominant rock units.

Table 5 List of rock samples used for petrographic investigation Laboratory microstructural investigation of thin sections of rock units of the study area are complementary to the study of the surface structure. The following are brief descriptions of the microscopic investigation of the dominant rock units.

Related Figures (10)

Two study areas located in the Greater Accra Region of Ghana, between latitudes 5° 30! 0'! N and 52 49! 011, and The study area is underlain by metamorphic rocks of the Togo structural unit (TSU) and Dahomeyan gneissic complex (DGC). The main rock units of the TSU are the quartzites, phyllites and schist, where groundwater occurrence depends on secondary porosity resulting from fracturing and weathering [17]. The DGC rocks, consist of acidic and basic gneisses [17], that are generally massive with only few discontinuities, low transmissivity and permeability when compared to the TSU [18].
Two study areas located in the Greater Accra Region of Ghana, between latitudes 5° 30! 0'! N and 52 49! 011, and The study area is underlain by metamorphic rocks of the Togo structural unit (TSU) and Dahomeyan gneissic complex (DGC). The main rock units of the TSU are the quartzites, phyllites and schist, where groundwater occurrence depends on secondary porosity resulting from fracturing and weathering [17]. The DGC rocks, consist of acidic and basic gneisses [17], that are generally massive with only few discontinuities, low transmissivity and permeability when compared to the TSU [18].
Table 1. Summary of sampling methods, governing equations of fracture properties and the expected minimum measurements (M odified afte! [25]) N is the total number of sampled fractures, L is the scanline length, A is the sampling area, r is the radius of the circular scanline, | is the fracture length, n and m are the number of intersections with a circular scanline and the number of endpoints in a circular window enclosed by the circular scanline.. c Number of fractures contained in a sampling area.
Table 1. Summary of sampling methods, governing equations of fracture properties and the expected minimum measurements (M odified afte! [25]) N is the total number of sampled fractures, L is the scanline length, A is the sampling area, r is the radius of the circular scanline, | is the fracture length, n and m are the number of intersections with a circular scanline and the number of endpoints in a circular window enclosed by the circular scanline.. c Number of fractures contained in a sampling area.
Figure 2. Equal Area Stereographic Projections of Structural Features Identified from Site 1, within the TSU. (A) Rose diagram joint and openec foliation planes, (B) Foliation sets within Quartzites, (C) Joints within the Quartzites (D) Fault sets within Quartzites at Site 1, (E) Foliation sets withir the phyllite/Quartzite, (F) Joint sets within the phyllite/Quartzite Table 2. Scanline mapping
Figure 2. Equal Area Stereographic Projections of Structural Features Identified from Site 1, within the TSU. (A) Rose diagram joint and openec foliation planes, (B) Foliation sets within Quartzites, (C) Joints within the Quartzites (D) Fault sets within Quartzites at Site 1, (E) Foliation sets withir the phyllite/Quartzite, (F) Joint sets within the phyllite/Quartzite Table 2. Scanline mapping
—— 3. Equal Area Stereographic Projections of Structural Features Identified from Site 2, within the DGC. (A q poration sets within Acid gneisse site 2 (B) Joints sets within Acid gneisses site 2 [1 set], (C) , Foliation sets within basic gneisses at site 2 [2 sets], (D) Joints sets within basic gneisse site 2 : sets], (E) Rose diagram of fracture dip direction, indicating a very variable dip directions of joint system Fractures are assumed to be planar [23] and so, the dip angle (the angle the plane makes with the horizontal surface), strike (the compass bearing a structural surface makes as it intersects the horizontal), and the dip direction Plots of .poles provided a visual depiction of pole concentrations. By contouring the pole plots, the most highly concentrated areas of poles, representing the dominant fracture sets were identified. The stereo-nets of the poles to planes of fracture orientations measured for outcrops at Site 1 and Site 2 are shown in Figure 2 and Figure 3 respectively.
—— 3. Equal Area Stereographic Projections of Structural Features Identified from Site 2, within the DGC. (A q poration sets within Acid gneisse site 2 (B) Joints sets within Acid gneisses site 2 [1 set], (C) , Foliation sets within basic gneisses at site 2 [2 sets], (D) Joints sets within basic gneisse site 2 : sets], (E) Rose diagram of fracture dip direction, indicating a very variable dip directions of joint system Fractures are assumed to be planar [23] and so, the dip angle (the angle the plane makes with the horizontal surface), strike (the compass bearing a structural surface makes as it intersects the horizontal), and the dip direction Plots of .poles provided a visual depiction of pole concentrations. By contouring the pole plots, the most highly concentrated areas of poles, representing the dominant fracture sets were identified. The stereo-nets of the poles to planes of fracture orientations measured for outcrops at Site 1 and Site 2 are shown in Figure 2 and Figure 3 respectively.
Figure 4. Histogram and total fracture distribution for A blekuma linear scanline mapping: (a) Possible distribution models, (b) Best fit mode
Figure 4. Histogram and total fracture distribution for A blekuma linear scanline mapping: (a) Possible distribution models, (b) Best fit mode
Figure 5. Histogram and total fracture distribution for Danfa linear scanline mapping: (a) Possible distribution models, (b) Best fit mode
Figure 5. Histogram and total fracture distribution for Danfa linear scanline mapping: (a) Possible distribution models, (b) Best fit mode
‘r’ is the radius of the circular scanline, | is fracture trace length, n and m are the number of intersections with a circular scanline and the number of endpoints in a circular window enclosed by the circular scanline. Table 4. Summary statistics of circular scanlines and mean trace lengths from Sites
‘r’ is the radius of the circular scanline, | is fracture trace length, n and m are the number of intersections with a circular scanline and the number of endpoints in a circular window enclosed by the circular scanline. Table 4. Summary statistics of circular scanlines and mean trace lengths from Sites
Figure 6. Photomicrograph of Sample TSU 1004 (A) Strongly Deformed Rock Showing Preferred Oriented Mineral Grains, and Alteration Features. (B) Micro-texture Showing Coarse and Micro-perthites and Deformed Fine Grained Quartz (Crossed Polars) The linear fracture frequency, mean fracture spacing, fracture density and intensity measured linearly along the scanline is presented in Table 6. The mean linear density indicates a close level of fracturing (>4 fractures/m) for the two study sites, albeit maximum spacing was 1.0m at Site 2.
Figure 6. Photomicrograph of Sample TSU 1004 (A) Strongly Deformed Rock Showing Preferred Oriented Mineral Grains, and Alteration Features. (B) Micro-texture Showing Coarse and Micro-perthites and Deformed Fine Grained Quartz (Crossed Polars) The linear fracture frequency, mean fracture spacing, fracture density and intensity measured linearly along the scanline is presented in Table 6. The mean linear density indicates a close level of fracturing (>4 fractures/m) for the two study sites, albeit maximum spacing was 1.0m at Site 2.
Table 6. Comparison of fracture characteristics from Site 1 and Site 2 Comparing the means of fracture spacing for both Site 1 (TSU) and Site 2 (Dahomeyan formation) with ISRM (1978) (Table 7), fractures in both sites can be said to have close to moderate fracture spacing. This has important implication on fluid flow and geotechnical properties of the rock masses. 4,7. Areal Intensity, Density and Trace Length
Table 6. Comparison of fracture characteristics from Site 1 and Site 2 Comparing the means of fracture spacing for both Site 1 (TSU) and Site 2 (Dahomeyan formation) with ISRM (1978) (Table 7), fractures in both sites can be said to have close to moderate fracture spacing. This has important implication on fluid flow and geotechnical properties of the rock masses. 4,7. Areal Intensity, Density and Trace Length
Table 7. Classification of fracture spacing [36] The form of the raw fracture spacing values at Site 1, were such that, they could best be fitted with negative 2-parameter exponential density function model (Figure 4). The 2-parameter exponential probability density function (pdf) is given by:
Table 7. Classification of fracture spacing [36] The form of the raw fracture spacing values at Site 1, were such that, they could best be fitted with negative 2-parameter exponential density function model (Figure 4). The 2-parameter exponential probability density function (pdf) is given by:
580 California St., Suite 400
San Francisco, CA, 94104
© 2025 Academia. All rights reserved