Petrochemistry and petrogenesis of the Precambrian Basement Complex rocks around Akungba-Akoko, southwestern Nigeria
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24 apr 2020
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Categoria dell'articolo: Original scientific paper
Pubblicato online: 24 apr 2020
Pagine: 173 - 183
Ricevuto: 14 nov 2019
Accettato: 09 dic 2019
DOI: https://doi.org/10.2478/rmzmag-2019-0036
Parole chiave
© 2019 Ogunyele A.C., Oluwajana O.A., Ehinola I.Q., Ameh B.E., Salaudeen T.A., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.
Figure 1
![(a) Regional geological map of Nigeria within the Pan-African mobile belt between the West African and Congo Cratons and (b) outline geological map of Nigeria showing Akungba-Akoko in the southwestern Nigerian Basement Complex (modified after [3]).](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/647369844e662f30ba53d1ee/j_rmzmag-2019-0036_fig_001.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6AP2G7AKOUXAVR44%2F20250915%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20250915T100551Z&X-Amz-Expires=3600&X-Amz-Signature=38e59485a595103c1fd84da321ba896bdc2820d2905aca8ae7a6b100c06ff37a&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Figure 2
Figure 3
Figure 4
![QAP diagrams for classifying (a) the gneisses and biotite granite (after [14]) and (b) charnockite (after [15]) of Akungba-Akoko.](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/647369844e662f30ba53d1ee/j_rmzmag-2019-0036_fig_004.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6AP2G7AKOUXAVR44%2F20250915%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20250915T100551Z&X-Amz-Expires=3600&X-Amz-Signature=127d027e5eed09a8febc31c0a4be62a5b0364fec305b5b100d874d13b3d2a538&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Figure 5
![Petrochemical diagrams for discriminating Akungba-Akoko granite gneiss, biotite gneiss, biotite granite and charnockite. (a) K2O + Na2O versus SiO2 plot (after [17]), (b) K2O versus SiO2 plot (after [18]), (c) Al2O3/(Na2O + K2O) versus Al2O3/(CaO + Na2O + K2O) molecular plot (after [19]), (d) Al2O3/(CaO + Na2O + K2O) versus SiO2 (after [20]), (e) FeOtotal/(FeOtotal + MgO) versus SiO2 (after [21]) and (f) K2O + Na2O– CaO versus SiO2 plot (after [21]).](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/647369844e662f30ba53d1ee/j_rmzmag-2019-0036_fig_005.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6AP2G7AKOUXAVR44%2F20250915%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20250915T100551Z&X-Amz-Expires=3600&X-Amz-Signature=1bf4edd32f203b267f219f129257d2d3a3cb53f767def20eed4063bfff962090&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Figure 6
![Petrochemical diagrams of (a) TiO2 versus SiO2 (after [22]) and (b) Rb versus Nb + Y (after [25]) for determining the petrogenesis and tectonic settings of Akungba-Akoko granite gneiss, biotite gneiss, biotite granite and charnockite.](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/647369844e662f30ba53d1ee/j_rmzmag-2019-0036_fig_006.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6AP2G7AKOUXAVR44%2F20250915%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20250915T100551Z&X-Amz-Expires=3600&X-Amz-Signature=fbc721a0bbd9e861502edd26845cb50acd831f22e7f064588727e5e468de0ec4&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Trace element compositions (in ppm) of the Basement Complex rocks of Akungba-Akoko_
| Trace | Granite gneiss | Biotite gneiss | Biotite granite | Charnockite | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| GGN | 1 GGN2 | GGN3 | BGN1 | BGN2 | BG1 | BG2 | Ch1 | Ch2 | Ch3 | |
| Ba | 300 | 470 | 310 | 510 | 240 | 580 | 684 | 815 | 722 | 814 |
| Co | 5 | 6 | 4.9 | 3 | 1 | 3 | 4 | 3.8 | 4 | 2 |
| Cr | 0.38 | 0.3 | 0.28 | 0.2 | 0.27 | 1 | 2 | 2 | 2 | 1 |
| Nb | 7 | 5 | 4 | 2 | 2 | 1 | 2 | 3 | 3 | 2 |
| Ni | 8 | 7 | 6 | 3 | 12 | 6 | 9 | 7 | 5 | 4 |
| Rb | 82 | 90 | 122 | 100 | 130 | 120 | 100 | 98 | 120 | 116 |
| Sc | 2 | 3 | 3 | 1 | 1 | 1 | 1 | 3 | 1 | - |
| Sr | 110 | 90 | 116 | 88 | 40 | 138 | 150 | 14 | 167 | 132 |
| Th | 18 | 12 | 22 | 16 | 24 | 12 | 13 | 12 | 14 | 10 |
| V | 1 | 12.5 | 17 | 2 | 3 | 13.7 | 13 | 10 | 12 | 16 |
| Y | 27 | 14 | 32 | 40 | 14 | 31 | 42 | 40 | 38 | 26 |
| Zr | 100 | 66 | 80 | 122 | 70 | 119 | 130 | 110 | 120 | 116 |
| K/Rb | 242.89 | 238.82 | 204.07 | 301.25 | 162.15 | 158.37 | 198.34 | 199.00 | 163.90 | 216.77 |
Major element compositions (in wt_%) of the Basement Complex rocks of Akungba-Akoko_
| Major | Granite gneiss | Biotite gneiss | Biotite granite | Charnockite | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| GGN1 | GGN2 | GGN3 | BGN1 | BGN2 | BG1 | BG2 | Ch1 | Ch2 | Ch3 | |
| SiO2 | 74.40 | 73.86 | 74.58 | 73.62 | 67.80 | 60.06 | 59.83 | 57.50 | 58.72 | 59.70 |
| TiO2 | 0.18 | 0.23 | 0.32 | 0.50 | 0.69 | 1.00 | 1.03 | 1.09 | 0.98 | 0.88 |
| Al2O3 | 13.40 | 13.84 | 13.52 | 12.60 | 14.63 | 16.77 | 17.04 | 17.90 | 16.78 | 15.20 |
| Fe2O3 | 3.26 | 3.83 | 3.68 | 3.58 | 5.33 | 6.66 | 6.68 | 6.70 | 6.68 | 6.73 |
| MnO | 0.03 | 0.06 | 0.04 | 0.05 | 0.04 | 0.13 | 0.15 | 0.25 | 0.26 | 0.13 |
| MgO | 0.27 | 0.32 | 0.21 | 0.76 | 1.00 | 3.02 | 2.92 | 2.41 | 3.02 | 3.11 |
| CaO | 3.00 | 2.89 | 2.04 | 3.01 | 4.18 | 5.54 | 6.05 | 7.11 | 6.93 | 7.02 |
| Na2O | 2.01 | 1.75 | 1.80 | 1.62 | 2.06 | 0.84 | 0.67 | 0.86 | 0.72 | 0.70 |
| K2O | 2.40 | 2.59 | 3.00 | 3.63 | 2.54 | 2.29 | 2.39 | 2.35 | 2.37 | 3.03 |
| P2O5 | ND | ND | ND | ND | ND | ND | ND | 0.01 | ND | 0.01 |
| LOI | 0.51 | 0.58 | 0.71 | 0.90 | 1.40 | 3.25 | 3.03 | 2.86 | 3.15 | 2.45 |
| TOTAL | 99.46 | 99.95 | 99.90 | 100.27 | 99.67 | 99.56 | 99.79 | 99.04 | 99.61 | 98.96 |
Average modal mineralogical compositions of Akungba-Akoko Basement Complex rocks_
| Minerals (vol.%) | GGN1b | GGN2b | BGN1b | BGN2b | BG1b | BG2b | Ch1b |
|---|---|---|---|---|---|---|---|
| Quartz | 29.40 | 26.60 | 26.40 | 26.40 | 25.30 | 21.40 | 22.30 |
| K-feldspar | 28.60 | 23.30 | 21.60 | 23.40 | 22.30 | 18.00 | 18.30 |
| Plagioclase feldspar | 34.50 | 35.20 | 31.00 | 33.20 | 32.00 | 28.30 | 32.30 |
| Biotite | 6.10 | 8.40 | 10.10 | 10.20 | 14.90 | 25.40 | 8.40 |
| Hornblende | - | 3.30 | 8.50 | 5.10 | 3.20 | 5.10 | 6.00 |
| Muscovite | 0.90 | 2.50 | 1.40 | 1.20 | 2.00 | 1.00 | 5.30 |
| Opaque | 0.60 | 0.70 | 0.90 | 0.60 | 0.80 | 0.90 | 0.40 |
| Pyroxene | - | - | - | - | - | - | 7.70 |
| Total | 100.10 | 100.00 | 99.90 | 100.10 | 100.50 | 100.10 | 100.70 |