Econ. Environ. Geol. 2023; 56(3): 259-275
Published online June 30, 2023
https://doi.org/10.9719/EEG.2023.56.3.259
© THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY
Correspondence to : *umaru.aliyu@paulesi.org.ng
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided original work is properly cited.
Pan African granitoids of Kaiama is comprised of K-feldspar rich granites, porphyritic granites, and granitic gneiss that are intruded by quartz veins and aplitic veins and dykes which trend NE-SW. In order to establish the geochemical signatures, petrogenesis, and tectonic settings of the lithological units, petrological, petrographical, and geochemical studies was carried out. Petrographic analysis reveals that the granitoids are dominantly composed of quartz, plagioclase feldspar, biotite, and k-feldspar with occasional muscovites, sericite, and opaque minerals that constitute very low proportion. Major, trace, and rare earth elements geochemical data reveal that the rocks have moderate to high silica (SiO2=63-79.7%) and alumina (Al2O3=11.85-16.15) contents that correlate with the abundance of quartz, feldspars, and biotite. The rocks are calc-alkaline, peraluminous (ASI=1.0-<1.2), and S-type granitoids sourced by melting of pre-existing metasedimentary or sedimentary rocks containing Al, Na, and K oxides. They plot dominantly in the WPG and VAG fields suggesting emplacement in a post-collisional tectonic setting. On a multi-element variation diagram, the granitoids show depletion in Ba, K, P, Rb, and Ti while enrichment was observed for Th, U, Nd, Pb and Sm. Their rare-earth elements pattern is characterized by moderate fractionation ((La/Yb)N=0.52-38.24) and pronounced negative Eu-anomaly (Eu/Eu*=0.02-1.22) that points to the preservation of plagioclase from the source magma. Generally, the geochemical features of the granitoids show that they were derived by the partial melting of crustal rocks with some input from greywacke and pelitic materials in a typical post-collisional tectonic setting.
Keywords granitoids, peraluminous, tectonic setting, petrography, partial melting
Econ. Environ. Geol. 2023; 56(3): 259-275
Published online June 30, 2023 https://doi.org/10.9719/EEG.2023.56.3.259
Copyright © THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY.
Aliyu Ohiani Umaru1,4,*, Olugbenga Okunlola2, Umaru Adamu Danbatta3, Olusegun G. Olisa5
1Pan African University of Life and Earth Science Institute including (Health and Agriculture), University of Ibadan, Oyo state, Nigeria
2Department of Geology, University of Ibadan, Oyo state, Nigeria
3Department of Geology, Ahmadu Bello University, Kaduna state, Nigeria
4Department of Geology, University of Maiduguri, Borno State, Nigeria
5Department of Earth Sciences, Olabisi Onabanjo University, Ago Iwoye, Ogun state, Nigeria
Correspondence to:*umaru.aliyu@paulesi.org.ng
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided original work is properly cited.
Pan African granitoids of Kaiama is comprised of K-feldspar rich granites, porphyritic granites, and granitic gneiss that are intruded by quartz veins and aplitic veins and dykes which trend NE-SW. In order to establish the geochemical signatures, petrogenesis, and tectonic settings of the lithological units, petrological, petrographical, and geochemical studies was carried out. Petrographic analysis reveals that the granitoids are dominantly composed of quartz, plagioclase feldspar, biotite, and k-feldspar with occasional muscovites, sericite, and opaque minerals that constitute very low proportion. Major, trace, and rare earth elements geochemical data reveal that the rocks have moderate to high silica (SiO2=63-79.7%) and alumina (Al2O3=11.85-16.15) contents that correlate with the abundance of quartz, feldspars, and biotite. The rocks are calc-alkaline, peraluminous (ASI=1.0-<1.2), and S-type granitoids sourced by melting of pre-existing metasedimentary or sedimentary rocks containing Al, Na, and K oxides. They plot dominantly in the WPG and VAG fields suggesting emplacement in a post-collisional tectonic setting. On a multi-element variation diagram, the granitoids show depletion in Ba, K, P, Rb, and Ti while enrichment was observed for Th, U, Nd, Pb and Sm. Their rare-earth elements pattern is characterized by moderate fractionation ((La/Yb)N=0.52-38.24) and pronounced negative Eu-anomaly (Eu/Eu*=0.02-1.22) that points to the preservation of plagioclase from the source magma. Generally, the geochemical features of the granitoids show that they were derived by the partial melting of crustal rocks with some input from greywacke and pelitic materials in a typical post-collisional tectonic setting.
Keywords granitoids, peraluminous, tectonic setting, petrography, partial melting
Table 1 . Major elements oxides (wt%), trace and rare earth elements (ppm) composition of granitoids in Kaiama area.
Sample No | K-feldspar rich granites | Porphyritic granites | Granite gneiss | |||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Oxides (%) | P1 | P2 | P3 | P4 | P5 | PG1 | PG2 | PG3 | PG4 | PG5 | PG6 | PG7 | G1 | G2 | G3 | G4 | G5 | G6 |
SiO2 | 78.8 | 76.6 | 79.7 | 77.3 | 76.8 | 72.4 | 73 | 73.1 | 71.9 | 72.2 | 72.5 | 73.8 | 68.2 | 69.2 | 67.4 | 69.2 | 63 | 64.7 |
Al2O3 | 12.25 | 13.3 | 11.85 | 12.4 | 12.35 | 13.15 | 13.7 | 13.8 | 13.3 | 14 | 13.1 | 13.8 | 15.4 | 14.2 | 14.75 | 15.15 | 16.1 | 16.15 |
Fe2O3 | 0.95 | 1.36 | 1.04 | 1.24 | 1.28 | 2.06 | 1.84 | 2.18 | 2.06 | 2 | 2.1 | 2.07 | 3.61 | 4.95 | 4.94 | 3.77 | 6.13 | 5.86 |
CaO | 0.14 | 0.18 | 0.51 | 0.5 | 0.15 | 1.16 | 1.24 | 0.95 | 1.24 | 1.11 | 1.3 | 0.83 | 2.38 | 2.13 | 2.02 | 2.42 | 2.96 | 3.2 |
MgO | 0.03 | 0.02 | 0.06 | 0.02 | 0.02 | 0.26 | 0.24 | 0.27 | 0.28 | 0.25 | 0.28 | 0.27 | 0.78 | 0.98 | 0.79 | 0.6 | 1.2 | 1.12 |
Na2O | 3.82 | 3.96 | 4.06 | 4.19 | 4.12 | 3.48 | 3.75 | 3.72 | 3.64 | 3.85 | 3.76 | 3.53 | 3.85 | 3.11 | 3.15 | 3.21 | 3.31 | 3.43 |
K2O | 4.99 | 5.15 | 3.74 | 4.43 | 4.54 | 4.49 | 4.5 | 4.5 | 4.31 | 4.54 | 4 | 4.53 | 3.39 | 4.28 | 4.85 | 4.77 | 4.54 | 3.93 |
TiO2 | 0.05 | 0.03 | 0.05 | 0.04 | 0.03 | 0.19 | 0.18 | 0.22 | 0.21 | 0.19 | 0.22 | 0.2 | 0.54 | 0.72 | 0.71 | 0.43 | 0.98 | 0.86 |
MnO | 0.04 | 0.05 | 0.02 | 0.02 | 0.02 | 0.03 | 0.03 | 0.04 | 0.04 | 0.04 | 0.04 | 0.04 | 0.05 | 0.06 | 0.07 | 0.05 | 0.08 | 0.08 |
P2O5 | BDL | 0.01 | BDL | BDL | BDL | 0.04 | 0.04 | 0.04 | 0.06 | 0.05 | 0.05 | 0.06 | 0.2 | 0.27 | 0.29 | 0.1 | 0.35 | 0.35 |
LOI | 0.51 | 0.51 | 0.48 | 0.46 | 0.44 | 0.81 | 0.83 | 0.54 | 0.93 | 0.38 | 1.11 | 0.82 | 1.06 | 0.5 | 0.32 | 0.44 | 0.47 | 0.55 |
Total | 101.5 | 101.1 | 101.5 | 100.6 | 99.7 | 98.16 | 99.44 | 99.47 | 98.07 | 98.71 | 98.55 | 100.06 | 99.55 | 100.51 | 99.42 | 100.23 | 99.29 | 100.38 |
K/N | 1.3 | 1.3 | 0.92 | 1.05 | 1.1 | 1.29 | 1.2 | 1.21 | 1.18 | 1.17 | 1.06 | 1.28 | 0.88 | 1.37 | 1.53 | 1.48 | 1.37 | 1.14 |
N+K | 8.81 | 9.11 | 7.8 | 8.62 | 8.66 | 7.97 | 8.25 | 8.22 | 7.95 | 8.39 | 7.76 | 8.06 | 7.24 | 7.39 | 8 | 7.98 | 7.85 | 7.36 |
A/CNK | 1.36 | 1.43 | 1.42 | 1.36 | 1.4 | 1.44 | 1.44 | 1.5 | 1.44 | 1.47 | 1.44 | 1.55 | 1.6 | 1.49 | 1.47 | 1.45 | 1.48 | 1.52 |
K | 0.41 | 0.43 | 0.31 | 0.37 | 0.38 | 0.37 | 0.37 | 0.37 | 0.36 | 0.38 | 0.33 | 0.38 | 0.28 | 0.36 | 0.4 | 0.4 | 0.38 | 0.33 |
K/Rb | 8.50 | 8.19 | 12.35 | 7.88 | 7.93 | 15.22 | 14.68 | 14.80 | 14.28 | 13.70 | 14.10 | 14.84 | 16.09 | 17.30 | 20.05 | 21.22 | 21.65 | 21.49 |
Ba/Rb | 0.26 | 0.08 | 0.67 | 0.09 | 0.06 | 2.59 | 2.62 | 3.24 | 2.86 | 2.46 | 2.53 | 3.14 | 3.41 | 3.34 | 4.60 | 3.40 | 6.92 | 7.13 |
Rb/Sr | 33.94 | 59.66 | 5.69 | 47.37 | 50.42 | 1.81 | 1.69 | 1.59 | 1.66 | 1.92 | 1.65 | 1.72 | 0.63 | 0.87 | 0.88 | 1.34 | 0.66 | 0.53 |
Trace element concentration (ppm) | ||||||||||||||||||
Au | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL | BDL |
Co | 45 | 63 | 39 | 78 | 71 | 51 | 68 | 44 | 40 | 47 | 51 | 38 | 55 | 59 | 93 | 69 | 63 | 72 |
Ni | 4 | 1 | 2 | 1 | 1 | 3 | 2 | 5 | 5 | 1 | 5 | 4 | 7 | 7 | 4 | 4 | 6 | 4 |
Cu | 4 | 50 | 3 | 23 | 1 | 19 | 2 | 13 | 2 | 8 | 2 | 7 | 7 | 13 | 7 | 8 | 7 | 15 |
Zn | 51 | 65 | 37 | 62 | 73 | 52 | 49 | 53 | 58 | 55 | 51 | 49 | 65 | 86 | 89 | 70 | 104 | 93 |
As | 5 | 9 | <5 | 5 | <5 | 5 | <5 | <5 | <5 | 9 | <5 | <5 | <5 | <5 | <5 | <5 | <5 | <5 |
Rb | 482 | 525 | 251 | 469 | 479 | 243 | 252 | 250 | 252 | 276 | 234 | 256 | 174 | 208 | 199.5 | 188.5 | 175.5 | 153.5 |
Sr | 14.2 | 8.8 | 44.1 | 9.9 | 9.5 | 134.5 | 149.5 | 157 | 151.5 | 144 | 141.5 | 149 | 275 | 240 | 227 | 140.5 | 267 | 287 |
Sn | 11.1 | 7.9 | 8 | 9.3 | 10.3 | 6.1 | 6.4 | 6.6 | 7.6 | 10.3 | 6.4 | 5.7 | 2.9 | 2.6 | 3.7 | 3.1 | 3.2 | 2.7 |
Ba | 123.5 | 42.5 | 167.5 | 40.7 | 30.8 | 630 | 661 | 810 | 720 | 680 | 592 | 805 | 594 | 694 | 917 | 641 | 1215 | 1095 |
Pb | 61 | 68 | 45 | 60 | 58 | 34 | 32 | 32 | 33 | 38 | 32 | 32 | 23 | 25 | 34 | 23 | 26 | 23 |
Ta | 7.3 | 6.2 | 7.6 | 6.5 | 7.2 | 3.3 | 4.1 | 4.2 | 3.3 | 4.5 | 4.1 | 3.4 | 1.1 | 1 | 1.6 | 1.6 | 2 | 1.9 |
Y | 122.5 | 144 | 74.8 | 114 | 118.5 | 40.4 | 40.4 | 62.3 | 39.1 | 49.3 | 48.6 | 78.3 | 23.4 | 33 | 26.8 | 24.2 | 27.2 | 25.3 |
Nb | 61.2 | 48 | 50.3 | 57.2 | 49.4 | 22.4 | 23 | 27.7 | 21.7 | 22.3 | 25.1 | 23.2 | 15.5 | 19.9 | 22.1 | 16.55 | 25.1 | 21.2 |
Hf | 5.99 | 6.24 | 4.7 | 5.98 | 5.91 | 5.75 | 5.47 | 6.12 | 5.54 | 5.53 | 7.21 | 5.61 | 7.67 | 10.5 | 9.51 | 7.47 | 8.4 | 9.93 |
Zr | 116 | 107 | 79 | 115 | 115 | 188 | 164 | 185 | 182 | 164 | 230 | 176 | 293 | 412 | 389 | 282 | 363 | 414 |
Th | 48.8 | 39.4 | 29.1 | 43.6 | 44.6 | 17.4 | 19.1 | 21.4 | 21.2 | 26.8 | 23 | 19.75 | 13.15 | 22.5 | 6.16 | 22.5 | 6.15 | 2.03 |
V | <5 | <5 | <5 | <5 | <5 | 10 | 10 | 13 | 14 | 12 | 13 | 11 | 40 | 52 | 41 | 34 | 62 | 60 |
Ga | 31.2 | 35.8 | 28.6 | 35.5 | 34 | 24.9 | 25.4 | 25.4 | 23.9 | 25.1 | 24.5 | 24.7 | 24.7 | 22.1 | 22.4 | 21 | 24.5 | 23.6 |
Mo | 2 | 7 | <1 | 1 | 4 | <1 | 1 | <1 | 1 | <1 | 1 | <1 | 1 | 1 | 1 | <1 | 1 | 1 |
Cs | 4.61 | 6.62 | 4.82 | 6.43 | 5.73 | 7.19 | 7.04 | 7.21 | 7.53 | 29.5 | 8.03 | 7.2 | 1.23 | 2.94 | 3.18 | 4.53 | 3.24 | 2.64 |
Rare earth elements concentration (ppm) | ||||||||||||||||||
La | 11.9 | 13.5 | 9.5 | 14.6 | 11.8 | 34.4 | 32.4 | 67.7 | 36.6 | 39.1 | 65.2 | 56.2 | 59 | 97.5 | 46.5 | 95.3 | 31.9 | 29.2 |
Ce | 46 | 38.2 | 22.4 | 40.7 | 33.2 | 70.5 | 63.9 | 121 | 75.9 | 80.7 | 130 | 97.9 | 122 | 204 | 99.8 | 197 | 68.9 | 62.7 |
Pr | 4.69 | 5.75 | 3.17 | 6 | 4.92 | 7.87 | 7.26 | 15 | 8.3 | 8.97 | 13.65 | 13.35 | 13.3 | 23 | 11.5 | 21.7 | 8.76 | 8.03 |
Nd | 21 | 27.4 | 14 | 27.6 | 23.7 | 30.6 | 25.6 | 55 | 32.5 | 34.5 | 48 | 50.9 | 45.7 | 78.5 | 42.6 | 74.8 | 34.7 | 32 |
Sm | 7.41 | 11.4 | 5.15 | 11.75 | 9.87 | 6.44 | 6.05 | 10.7 | 6.51 | 7.31 | 9.32 | 12.05 | 8.3 | 13.65 | 7.92 | 12.55 | 7.39 | 6.62 |
Eu | 0.13 | 0.08 | 0.27 | 0.09 | 0.1 | 0.72 | 0.79 | 1.15 | 0.73 | 0.76 | 0.84 | 1.29 | 1.72 | 1.63 | 1.98 | 1.38 | 2.35 | 2.6 |
Gd | 9.81 | 15.85 | 7.25 | 14.6 | 13.05 | 6.3 | 5.57 | 10.35 | 5.82 | 7.19 | 7.5 | 12.3 | 6.48 | 10.55 | 5.98 | 8.89 | 6.34 | 6.37 |
Tb | 1.99 | 2.84 | 1.69 | 2.8 | 2.39 | 0.98 | 0.96 | 1.79 | 0.99 | 1.26 | 1.28 | 2.13 | 0.99 | 1.38 | 1.04 | 1.13 | 1.02 | 0.92 |
Dy | 16.8 | 21.8 | 13.2 | 19.4 | 18.15 | 6.51 | 5.85 | 10.05 | 5.89 | 7.4 | 7.64 | 12.5 | 4.76 | 6.78 | 5.85 | 5.44 | 5.1 | 4.76 |
Ho | 3.52 | 4.58 | 2.67 | 3.6 | 3.69 | 1.27 | 1.33 | 2.11 | 1.26 | 1.59 | 1.74 | 2.62 | 0.86 | 1.25 | 0.99 | 0.96 | 1.06 | 1.02 |
Er | 12.15 | 14.85 | 8.56 | 11.55 | 12.25 | 4.23 | 4.01 | 6.01 | 3.83 | 4.98 | 4.84 | 7.93 | 2.49 | 3.37 | 2.54 | 2.33 | 2.83 | 2.54 |
Tm | 2.09 | 2.44 | 1.39 | 1.73 | 1.93 | 0.61 | 0.66 | 0.98 | 0.57 | 0.77 | 0.84 | 1.28 | 0.29 | 0.42 | 0.35 | 0.31 | 0.33 | 0.3 |
Yb | 14.9 | 17.4 | 9.4 | 11.5 | 13.5 | 4.23 | 4.12 | 6.42 | 3.78 | 5.22 | 5.28 | 7.78 | 1.76 | 2.43 | 2.1 | 1.68 | 2.03 | 1.95 |
Lu | 2.03 | 2.33 | 1.16 | 1.73 | 1.96 | 0.51 | 0.65 | 0.91 | 0.62 | 0.73 | 0.86 | 1.11 | 0.24 | 0.37 | 0.34 | 0.27 | 0.28 | 0.28 |
Rb/Sr | 33.94 | 59.66 | 5.69 | 47.37 | 50.42 | 1.81 | 1.69 | 1.59 | 1.66 | 1.92 | 1.65 | 1.72 | 0.63 | 0.87 | 0.88 | 1.34 | 0.66 | 0.53 |
Rb/Ba | 3.9 | 12.35 | 1.5 | 11.52 | 15.55 | 0.39 | 0.38 | 0.31 | 0.35 | 0.41 | 0.4 | 0.32 | 0.29 | 0.3 | 0.22 | 0.29 | 0.14 | 0.14 |
Y/Nb | 2 | 3 | 1.49 | 1.99 | 2.4 | 1.8 | 1.76 | 2.25 | 1.8 | 2.21 | 1.94 | 3.38 | 1.51 | 1.66 | 1.21 | 1.46 | 1.08 | 1.19 |
K/Rb | 0.001 | 0.001 | 0.001 | 0.001 | 0.001 | 0.002 | 0.001 | 0.001 | 0.001 | 0.001 | 0.001 | 0.001 | 0.002 | 0.002 | 0.002 | 0.002 | 0.002 | 0.002 |
(Ce/Yb) N | 0.8 | 0.57 | 0.62 | 0.92 | 0.64 | 4.31 | 4.01 | 4.88 | 5.19 | 4 | 6.37 | 3.25 | 17.93 | 21.17 | 12.29 | 30.33 | 8.78 | 8.32 |
(Ce/Sm) N | 1.5 | 0.81 | 1.05 | 0.84 | 0.81 | 2.64 | 2.55 | 2.73 | 2.81 | 2.66 | 3.37 | 1.96 | 3.55 | 3.61 | 3.04 | 3.79 | 2.25 | 2.29 |
(Gd/Yb) N | 0.53 | 0.74 | 0.62 | 1.02 | 0.78 | 1.2 | 1.09 | 1.3 | 1.24 | 1.11 | 1.15 | 1.28 | 2.97 | 3.5 | 2.3 | 4.27 | 2.52 | 2.64 |
(La/Yb) N | 0.54 | 0.52 | 0.68 | 0.86 | 0.59 | 5.48 | 5.3 | 7.11 | 6.53 | 5.05 | 8.33 | 4.87 | 22.6 | 27.05 | 14.93 | 38.24 | 10.59 | 10.1 |
(La/Sm) N | 1.01 | 0.74 | 1.16 | 0.78 | 0.75 | 3.36 | 3.37 | 3.98 | 3.54 | 3.36 | 4.4 | 3.93 | 4.47 | 4.49 | 3.69 | 4.78 | 2.72 | 2.77 |
Eu/Eu* | 0.05 | 0.02 | 0.14 | 0.02 | 0.03 | 0.35 | 0.42 | 0.33 | 0.36 | 0.32 | 0.31 | 0.32 | 0.72 | 0.42 | 0.88 | 0.4 | 1.05 | 1.22 |
⅀REE | 154.4 | 178.4 | 99.8 | 167.6 | 150.5 | 175.1 | 159.1 | 309.1 | 183.3 | 200.4 | 296.9 | 279.3 | 267.8 | 444.8 | 229.4 | 423.7 | 172.9 | 159.2 |
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