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Hydrogeophysical investigation of groundwater potential and aquifer vulnerability prediction in basement complex terrain – A case study from Akure, Southwestern Nigeria

Abstract

This study provides a model for the prediction of groundwater potential and vulnerability of basement aquifers in parts of Akure, Southwestern Nigeria. Hydrogeophysical surveys involving very-low-frequency electromagnetic (VLF-EM) profiling and electrical resistivity (ER) sounding, as well as evaluation of hydraulic gradient using three-point method, were carried out. Ten VLF-EM reconnaissance survey traverses, with lengths ranging from 55 m to 75 m, at 10 m station separation, and 12 vertical electrical sounding (VES) stations were occupied. Two-dimensional map of the filtered real component reveals areas of high conductivity, indicative of linear features that can serve as a reservoir or conduit for fluid flow. Interpretation of the VES results delineates three to four geoelectric units. Two aquifer zones were identified, with resistivity values in the ranges of 20 Ωm to 310 Ωm and 100 Ωm to 3,000 Ω m, respectively. Transverse resistance, longitudinal conductance, coefficient of anisotropy and hydraulic gradient have values ranging from 318.2 Ωm2 to 1,041.8 Ωm2, 0.11 mhos to 0.39 mhos, 1.04 to 1.74 and 0.017 to 0.05, respectively. The results of this study identified two prospective borehole locations and the optimum position to site the proposed septic system, based on the aquifer’s protective capacity and groundwater flow properties.

Open access
Molecular dynamics simulation of aluminium melting

Abstract

Solid–liquid phase transition has been simulated by the molecular dynamics method, using isobaric–isoenthalpic ensemble. For interatomic potential, glue potential has been selected. The original algorithm for bookkeeping of the information on neighbouring relationships of the atoms has been developed and used in this research. Time consumption for calculation of interatomic forces has been reduced from o(N 2 ) to o(N) by the use of this algorithm.

Calculations show that phase transition from solid to liquid occurs between 1,000 K and 1,300 K. The simulated temperature of phase transition is higher than the experimental value due to the absence of crystal defects. If constant heat flux is supplied, temperature decreases during melting because the superheated state becomes unstable. During the cooling process, no significant changes of the observed variables were detected due to the high cooling rate, which prevents crystallisation.

Open access
Reconstruction and appraisal of Akunu–Akoko area iron ore deposits using geological and magnetic approaches

Abstract

Geological mapping and magnetic methods were applied for the exploration of iron ore deposits in the Akunu–Akoko area of Southwestern Nigeria for the purpose of evaluating their geological characteristics and resource potentials. A proton magnetometer measures the vertical, horizontal and total magnetic intensities in gammas. The subsurface geology was interpreted qualitatively and quantitatively. The downward continuations and second vertical derivatives, the small-sized mineralised bodies and shallow features in the study area were mapped. The faults are trending in the following directions: NE–SW, NW–SE, N–S and E–W groups, while the iron ore mineralisation is structurally controlled by two major groups of fault trends, namely, the NE–SW and NW–SE; the N–S and E–W groups are mere occurrences that do not contribute to the structural control of the iron ore mineralisation in Akunu.

The upward continuation has a linear feature similar to the principal orientation of the regional faults, while Locations 2 and 3 have relatively high magnetic susceptibility zones; suspected to be iron ore deposits. The depths to the magnetic sources ranged from 25 m to about 250 m.

Open access
Regional turbidites and turbiditic environments developed during Neogene and Quaternary in Croatia

Abstract

The Croatian Neogene and Quaternary depositional sequences preserve a record of several different depositional environments with turbidite successions. These are turbiditic systems developed during the Late Miocene in the Croatian part of the Pannonian Basin System and during the Pliocene and Pleistocene in the northern Adriatic Sea. The shape, salinity and depths of depositional areas were significantly different in these two depressional areas, but both were fed mostly with Alpine detritus. Neogene turbidites with lacustrine pelitic sedimentation formed thick heterogeneous sequences of sandstones and marls (totalling several hundreds to some thousands of metres in thickness in different depressional parts) of Upper Miocene age in Northern Croatia. By contrast, Pliocene and especially Pleistocene turbidites of the northern Adriatic were deposited in a marine environment where the total thickness of sand and clay sequences can reach up to several thousand metres. In both cases, individual sandy or sandstone turbiditic sequences (events) can reach several tens of metres in thickness. These turbidite clastic sediments are important hydrocarbon reservoirs.

Open access