Geology and Hydrogeology of the Gu-Line Volcanic Spring, Jos Plateau Nigeria

Author(s)

Abstract
Gu Volcanic line lies at the piedmont of the southeastern flank of the Jos Plateau and is inundated by volcanic springs with their out flows constituting 30-40% of the base flows of the upper River Shemankar which is the main water supply source of the River Shemankar Irrigation Scheme and the proposed Shemankar Valley Hydroelectric Power Project. This study is focused on the geology hydrogeology, hydrogeochemstry and origin of the volcanic springs and their suitability for domestic and agricultural usage. The study was into two phase of –(1)geological/hydrogeological mapping/ sampling and (2) laboratory analyses. Rock and spring waters were sampled for mineral and hydrogeochemical composition. The rocks elements and mineral composition was determined by petrographic analysis using cross polarized microscope and XRF methods The hydrochemical parameters of PH, EC, TDS and Temperature was determined using a combined Combo Hanna pH/ Temperature/ EC/ TDS meter in the field while the cations and anions concentrations was determined in the laboratory using AOAC method/techniques. The stable isotope composition of the springs was analyzed by Isotope Ratio Mass Spectrometer. The spring flow- discharge measurement carried out using velocity-area method.
The Gu Volcanic line is underlain by 3 major rock types and stratified in the order of : (1) Basement, (2) Sub-basalt, (3) Basalt. The 4 volcanic cones are generally stratified and composed of basalts, pyroclastic and ash. All the spring flows out from fractured basalts and or sub-basalts layers in seepage or gushing form. The springs minimum and maximum base flow range between 0.0004906 and 0.04787104m³/s. Hydrogeochemical analysis shows that GVL springs physical parameter of (T), pH, EC, and TDS values ranges from 24-27.8oc, 7.52-8.43, 219-311µS and 106-150ppm respectively. The cations of Mg2+, Ca2+, Na+ and K+ concentration range from 19.67-20.25mg/l, 0.14-0.31/Mg/l, 12.5-22.5mg/l, 4-6.5mg/l respectively. The anions concentration of Cl, HCO3 and NO3 are 10.175—31.89mg/l, 9.24-16.31mg/l, 13.73-18755mg/l and 9.12-25.14mg/l respectively. The Piper Trilinear diagram shows that the major water facie for the volcanic springs is Mg-Na-HCo3 type. However, the exception is that of Kwak spring with Mg-Na-(SO4-Cl) type. From Gibbs plot, the spring water elements sources are from water- rock interaction from hydrolytic and weathering processes. Isotopic analysis of oxygen-18 and deuterium(2H) and their plots on the Global Meteoric Water Line shows that there of meteoric origin. Comparative hydrogeochemical characteristics of the spring with WHO and FAO standards shows that they all fall within the permissible levels for usage.

Keywords
Geology, Gu Volcanic line, Hydrogeology, Hydro geochemistry, Water Quality

Cite this paper
Longpia, C. B., Dami, S.P., Geology and Hydrogeology of the Gu-Line Volcanic Spring, Jos Plateau Nigeria , SCIREA Journal of Geosciences. Volume 9, Issue 1, February 2025 | PP. 1-23. 10.54647/geosciences170349

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