Provenance and Weathering History of Clays from Share-Tshonga Area, Northern Bida Basin, Nigeria
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Date
2021
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Abstract
The claystone member of Enagi Formation exposed around Share-Tshonga, northern Bida Basin, central Nigeria was
studied to unravel the provenance, paleoweathering and paleoenvironmental conditions using XRF and ICP-MS.
Major oxides show enrichment in SiO (60.27-79.87%), relative to Al O (3.10-27.38 %), Fe O (0.98-22.85%), CaO 2 2 3 2 3
(0.01-0.03%), Na O (0.01-0.03%), K O (0.05-0.84%), MnO (0.01-0.15%), TiO (0.21-2.09%) and P O (0.05-0.84%). 2 2 2 2 5
The high SiO /Al O (2.20 to 22.76) with mean of 8.73 suggests higher detritus input in continental environment. 2 2 3
Certain proxy trace elements such as Cr (64.80ppm), Th (17.42ppm) and Zr (528.80ppm) are enriched in the
claystone compared to published PAAS (38.20ppm, 14.62ppm and 210.00ppm respectively) and UCC (31.00ppm,
10.70ppm and 190.00ppm respectively) data but depleted in Cu (7.03ppm), Zn (8.00ppm), Rb (12.05ppm), Sr
(38.63ppm) and Ba (132.40ppm) compared to published PAAS (50.00, 85.00, 160.00, 200.00 and 650.00
respectively)ppm and UCC (25.00, 71.00, 112.00, 350.00 and 550.00 respectively)ppm. The LREE (250.15ppm)
enrichment relative to HREE (23.49ppm) with (La/Yb) of 9.67 to 11.98, negative Europium (Eu/Eu*) anomaly N
(0.54-0.63) and (Ce/Ce*) anomaly (0.83-1.49) suggest felsic provenance. The mean values of Al O /TiO (13.17), 2 3 2
K O/Al O (0.02), LREE/HREE (10.65) coupled with discriminant plots of logK O/Na O versus SiO , TiO versus Zr, 2 2 3 2 2 2 2
La/Th versus Hf support dominant felsic source within passive margin tectonic settings. The ranges and mean ratio
values of Cu/Zn, V/Cr and U/Th indicate oxic, semi-humid to humid climatic settings. The values of chemical
indices; chemical index of alteration (CIA=96.44-99.13), chemical index of weathering (CIW=98.73-99.89),
plagioclase index of alteration (PIA=98.71-99.89) compared with the values of PAAS and UCC supported by various
plotting including CIW versus CIA and ICV versus CIA show that the claystone clearly depicted extremely high
weathering. Relatively higher mean of index of compositional variability (ICV) values (2.03) compared to PAAS
(0.74) and UCC (1.18) also indicate compositional maturity.