Arabian Journal of Geosciences最新文献

Groundwater occurrence in basement areas is very erratic, and mapping out suitable zones for groundwater exploitation in such terrain largely depends on the choice of the geophysical technique adopted. Groundwater potential zones (GWPZ) within the Jericho area of Ibadan, Southwestern Nigeria, were investigated using an integrated geophysical (electromagnetic profiling and electrical resistivity) approach. Vertical dipole (VD) and horizontal dipole (HD) surveys for the electromagnetic profiling (EMP) were executed along eleven (11) E-W profile lines 250–400 m long. The electrical resistivity methods included horizontal electrical resistivity profiling (HRP) using a current electrode (AB) spacing of 45 m at a 15 m measurement distance and 2D-multichannel resistivity tomography (MRT) with a minimum 5–7 m dipole length depending on the extent of each traverse line. Sixty-two (62) vertical electrical sounding (VES) were carried out at selected ground points with maximum AB/2 = 100 m. The EMP results reveal conductivity values for VD ranging between − 214 and 336 mS/m (average = 21 mS/m) and HD between − 24 and 56 mS/m (average = 14 mS/m). Furthermore, apparent resistivity values for HRP range between 575 and 14 Ωm (average = 134 Ωm), reflecting a moderately conductive subsurface lithology. The 2D MRT section revealed three to five subsurface layers, with aquifer thickness of 1–30 m. VES results reveal H, AK, HK, HA, QH, and HKH curve types revealing multiple layering systems (3–5 geoelectric subsurface layers) with varying resistivities and thicknesses (topsoil = 14–599 Ωm, 1–2 m; lateritic clay = 13–72 Ωm, 0.44–19 m; quartzitic/pegmatite unit = 288–1070 Ωm, 1–37 m; weathered saprolite = 10–2950 Ωm, 4–18 m; and fractured/fresh basement rock = 472–16,908 Ωm, 1–43 m). About 66.2% of investigated VES points represent potential drill points with apparently thick weathered overburden units and fractured underlying bedrocks. Conclusively, the eastern, western, and northeastern parts of the study area are classified as good GWPZs. This study has revealed the effectiveness of the combination of geophysical techniques for groundwater investigation in difficult geological terrains.

The CMIP6 model incorporates various socio-economic and technological development scenarios and provides a comprehensive assessment of climate change. It differs from earlier versions of climate models in terms of the number of modeling groups, future scenarios evaluated, and experiments performed. Selecting a suitable subset of CMIP6 models poses a significant challenge for climate change projections. Hence, this study aims to evaluate how well CMIP6 models simulate rainfall over the Didessa, Southwest of Ethiopia. The performance of the model was tested using observed data from 29 years (1985 to 2014). The statistical and Taylor diagram approaches are used to check the model’s performance. The results showed that the model’s performance was affected by the seasons. The GFDL-ESM4, GFDL-CM4, and CMCC-ESM2 models and their ensembles of them performed better on an annual basis. The GFDL-ESM4, GFDL-CM4, and MRI-ESM2-0 models were best performed in the summer season (June, July, and August). GFDL-CM4 and GFDL-ESM4 performed admirably during the spring season (September, October, and November). GFDL-ESM4, GFDL-ESM4, MPI-ESM1-2-HR, and MRI-ESM2-0 fit well with the observed data in the Autumn season (March, April, and May). In the dry season (December, January, and February), the CESM2-WACCM model outperformed in modeling rainfall. The MIROC6 overestimated the rainfall in all months. All models were overestimated in wet months and underestimated in dry months. The spatial distribution of the rainfall shows that all models simulated peak rainfall in central parts of the watershed and low rainfall values downstream of the sub-basin.

The Mannar Basin, located offshore of Sri Lanka, contains a sedimentary record spanning from the Cretaceous to the present, with a well-preserved sequence from the Middle Paleocene to Early Eocene. This study focuses on the Middle Paleocene to Early Eocene sedimentary section, using comprehensive whole rock major and trace element geochemical analyses to investigate paleo-oceanic conditions in the Northern Indian Ocean during this critical interval. Examination of redox-sensitive trace elements revealed temporal shifts in paleoclimatic conditions, indicative of warmer climates during the mid-late Paleogene period. Variations in elemental ratios, such as Rb/Sr and Sr/Cu, reflect changes in weathering intensity and terrestrial input, mirroring shifts in precipitation and climatic regimes. Insights from Zr/Rb ratios highlight past hydrodynamic conditions, suggesting deeper water and lower hydro energy environments. Fluctuations in Zr/Rb values, notably in the P/E samples, suggest relatively heightened wave energy during warmer climatic conditions in the tropical northern Indian Ocean. Diverse Paleogene depositional geomorphologies and seismic data point to increased total rare earth element (ΣREE) concentrations at the P/E boundary, attributed to amplified terrestrial input. Shale-normalized REE patterns and positive interelemental relationships further underscore the influence of terrigenous sources on sedimentary REE distributions. Negative Ce anomalies within studied sections suggest oxygenated environments during deposition, with minimal fluctuations in the bottom water oxygen content. Positive correlations between Ce/Ce* ratios and terrigenous materials emphasize the impact of detrital siliciclastic materials on sedimentary redox conditions. Overall, these geochemical findings provide critical evidence for significant shifts in paleoceanic conditions during the Paleocene–Eocene transition. The integration of multiple geochemical proxies elucidates the interplay between climatic fluctuations, hydrodynamic regimes, and terrestrial input, underscoring the Mannar Basin’s role as a valuable archive of past environmental change.

Accurate built-up extraction is important to land use planning. However, in semi-arid and arid environments, the accurate discrimination between bare soil and built-up area is challenging, due to their high spectral similarity. For that reason, the combination method of spectral indices was adopted from Sentinel-2 data to enhance built-up mapping of Ras El-Oued city (North-East Algeria). The spectral indices selected to be combined are mainly: the Normalized Difference Tillage Index (NDTI) and the Built-up Area Index (BAI) for built-up detection, and additionally, the Modified Bare Soil Index (MBI) for bare land extraction. Therefore, four combinations were developed and binarized via the Otsu algorithm to provide an automatic built-up mapping. The findings showed that the BAI index works better than the NDTI index in dry climates, since their overall accuracy (Oa) is about 92.00% and 86.33%, respectively. In contrast, the built-up mapping accuracy enhancement is noticed, when using the four combinations compared to the indices (NDTI and BAI); Com₁ (NDTI + MBI) and Com₂ (NDTI – BAI) have an identical (Oa) which is 93.00%. As for both Com₃ (MBI – BAI) and Com₄ (NDTI + MBI) – BAI), they produced approximately the same result, since they achieved an (Oa) which is 94.00% and 94.33%, respectively. Therefore, the four datasets created have revealed their positive behavior toward built-up detection in this area of semi-arid land, where both Com₃ and Com₄ were the best. The research results could, therefore, be suitable for mapping the cities in dry climates for better development in the future.

Abandoned roadways have long-term creep behaviors in the high geostress environment. Under the dual effects of creep and reconstruction-induced dynamic disturbance, surrounding rocks exhibit poor stability. Under the engineering background of a roadway in a coal mine in Liaoning Province, China, the surrounding rock stability in the initial roadway excavation process and the long-term creep process of the abandoned roadway was evaluated based on numerical simulation. Results show that the displacement and deformation of surrounding rocks after the initial excavation of the abandoned roadway are dominated by vault subsidence. The mechanical properties of roadway surrounding rocks are gradually deteriorated in the abandonment time of four years. The deformation of surrounding rocks linearly enlarges with prolonging creep time, and the surrounding rocks are in the steady-state creep process on the whole. The better the lithology of surrounding rocks is, the smaller the damage zone with failure tendency in surrounding rocks after reconstruction of the abandoned roadway. With the increments of burial depth and creep time of the abandoned roadway, the area with failure tendency in surrounding rocks enlarges after reconstruction. Enlarging the expansion size appropriately in the range of the initial damage zone formed due to the long-term creep effect can effectively improve the quality and stability of surrounding rocks. The surrounding rock stability of abandoned roadways with circular, straight-wall-top-arch, and rectangular cross-sections decreases successively after reconstruction. The research results provide theoretical reference for the reconstruction of abandoned roadways and the stability analysis and evaluation of surrounding rocks in mines.

The foundational rocking mechanism dissipates the transmitted earthquake energy to superstructure because of plastic hinges formation within the soil bed. However, there are some concerns using this design approach, such as undesired residual rotations or settlements that may cause the serviceability of the structure at risk. Nevertheless, there are several methods to control the weak points of rocking behavior of footings, namely, reinforcing the bed soils by geo synthetics or geo-grids, densifying it, or using piled foundations. Piled foundations’ rocking behavior can be studied experimentally using centrifuge and small-scale physical mode in the laboratory or large-scale testing in the field. In the present study, a developed small-scale physical model for studying rocking behavior of piled foundations is introduced. The soil bed preparation is done using the raining technique and then some typical results of the experiments, such as moment-rotation and settlement-rotation curves, are also presented. The model possesses the ability of performing a parametric study with various pile lengths, soil densities, and factor of safeties. Moreover, different types of superstructure-pile connections can be modeled and investigated through the device.

The Jita River volcanic series is situated in the northeastern Ethiopian volcanic province; the area provides a well-preserved stratigraphic sequence from lower basalt formation to upper lava flow termination. The main objective of the study is to establish the petrostratigraphy of the area and use these observations for the reconstruction of magmatic conditions along a well-exposed volcanic section. The major volcanic units of the Jita section from bottom to top are aphyric-intergranular basalt, aphyric-trachy basalt flow, augite cumulophyric basalt, olivine-augite phyric basalt, kfs vitrophyric rhyolite, augite phyric basalt, aphyric columnar basalt, moderately welded tuff, kfs phyric rhyolitic-ignimbrite, kfs phyric rhyolite, columnar-aphyric basalt, and slightly vesicular aphyric basalt. Petrographically, these volcanic rocks have different modal mineralogy and textures, revealing that there is a variation in the depth of mineral fractionation and magma flux in the stratigraphy. The flows clearly showed a broad change in modal mineralogy and eruptive cyclicity, and these constraints were that they were pulsed with a fluctuating magmatic influx along the complex plumbing systems and over time fed by shallower magmatic plumbing reservoirs. Overall, this stratigraphic study provides a new insight into the magmatic evolution of the northeastern Ethiopian volcanic provinces. 

The Rayen Fe deposit is located in the Urumieh-Dokhtar magmatic arc, a major metallogenic belt in Iran. The deposit consists of several hypogene orebodies that occur as high-grade lenticular massive magnetite bodies (up to 50 m long and 3 m wide). Magnetite geochemical compositions, microthermometric analysis of fluid inclusions, and magnetite oxygen isotope data were analyzed to constrain mineralization conditions and the genesis. The Fe mineralization is associated with the intrusion of an Eocene dioritic pluton into Cretaceous carbonate rocks. Magnetite is the most abundant ore mineral, accompanied by minor amounts of pyrite, chalcopyrite, hematite, and goethite. Pyroxene, garnet, quartz, amphibole, epidote, chlorite, and calcite are gangue minerals. The δ¹⁸O values of magnetite, ranging from + 0.15 to + 3.8‰, are consistent with precipitation from magmatic-hydrothermal fluids. The chemical signature of magnetite, including low mean concentrations of Al (0.268 wt.%), Ti (81.85 ppm), V (58.69 ppm), Cr (18.45 ppm), and Ni/Cr (mean = 3), LREE/HREE ratios (mean = 2.41), negative Ce (Ce/Ce* < 1, 0.25–0.65), and positive Eu (Eu/Eu* = 1.08–4.08) anomalies, are consistent with a magmatic-hydrothermal source for the mineralization. Results from microthermometric analyses of fluid inclusions indicate that a magmatic-meteoric mixed fluid was responsible for ore mineralization at the Rayen deposit. The tectonic setting (magmatic arc; Urumieh-Dokhtar magmatic belt), the epigenetic nature of the mineralization, textural evidence, mineral assemblages, adjacent to the dioritic pluton, microthermometric data, oxygen isotope analyses, and geochemical characteristics of magnetite indicate that the mineralization process at the Rayen Fe deposit is similar to that of skarn-type Fe deposits.

The lateritic soils in the Eastern region of Cameroon were subject to geochemical investigation in order to unveil their source rock composition, tectonic setting, past weathering intensity, climate type, and metallogenic properties. Source rock binary plots of Al₂O₃ vs. TiO₂, Th/Sc, La/Co, and Cr/Th indicates a felsic composition origin for the studied lateritic soils. The lateritic soils reflect a tectonic background of passive origin revealed by plots of Log (SiO₂ vs. K₂O/Na₂O), DF (A-P)MT, DF1 vs. DF2, and DF (A-P)M. The high plagioclase lixiviation and weathering displayed by the studied laterites are signpost by the plagioclase index of alteration (PIA) and chemical index of alteration (CIA) within a hot humid climatic condition. The hot humid conditions that existed during the laterites’ formation revealed by the PIA and CIA is also supported by trace element ratios f Rb/Sr Al₂O₃/MgO, Sr/Cu, Sr/Ba, and Fe₂O₃/MnO. The ternary plot of SiO₂-Al₂O₃-Fe₂O₃ coupled with the ternary plot of Al₂O₃-Fe2O3-MnO indicates that the studied lateritic soil is classified as metalliferous to terrigenous bauxitic clay with evidence of weak lateritization.