This study investigated the electrogeohydraulic characteristics of hydrogeologic units in parts of Nsukka, Enugu State, using Vertical Electrical Sounding (VES), the Improved Stratigraphic Modified Lorenz Plot (ISMLP), and Flow Zone Indicator (FZI) methods. Fifteen VES stations were interpreted, revealing four geoelectric layers and seven curve types, with H- and K-type curves dominating, indicating favorable groundwater conditions. The third geoelectric layer was identified as the principal aquifer unit, exhibiting resistivity values ranging from 33.7 to 21,987.8 Ωm, which reflect significant lithologic heterogeneity within the Ajali Sandstone Formation. Estimated hydrogeologic parameters showed porosity values of 0.268–0.330, hydraulic conductivity of 0.035–14.55 m/day, and permeability of 13.169–7596.737 μm2. Spatial analyses revealed considerable variability in porosity and permeability, indicating a heterogeneous aquifer system controlled by pore connectivity and lithologic variations. ISMLP analysis delineated seven hydraulic flow units (HFUs), grouped into five flow-efficiency classes. HFU2 was identified as the dominant fractured-flow unit, contributing 70.8% of the total aquifer flow capacity, while HFU1, HFU3, and HFU7 represented low-flow baffle zones. The FZI method identified six distinct HFUs, with HFU6 exhibiting the highest permeability and groundwater productivity. Aquifer heterogeneity assessment using the Dykstra–Parsons coefficient yielded a value of 0.833, indicating an extremely heterogeneous aquifer characterized by substantial permeability contrasts and complex groundwater flow behavior. The integrated application of geoelectrical, ISMLP, and FZI techniques successfully characterized aquifer flow units and hydraulic performance, providing valuable information for groundwater exploration, development, and sustainable management in the study area.
Sulawesi is characterized by complex interactions among major tectonic systems, producing strong spatial variations in seismicity and fault behavior. This study develops an integrated framework to characterize seismogenic depth, seismic coupling coefficient (SCC), and coupled thickness (CZ) across Sulawesi. A declustered earthquake catalog was grouped into 32 seismic clusters and analyzed to estimate cluster-specific magnitude of completeness, Gutenberg–Richter parameters, and frequency–magnitude distributions (FMD). Seismic moment rates were estimated by extrapolating the FMD toward alternative maximum-magnitude (Mmax) scenarios, whereas tectonic moment rates were evaluated using fault geometry, slip rate, rupture-width (W), and crustal-rigidity (μ) scenarios. The results reveal substantial spatial variability in seismogenic depth and SCC across different tectonic settings. Sensitivity and statistical analyses show that SCC estimates are systematically influenced by Mmax, rigidity, and rupture-width assumptions, demonstrating that representative coupling cannot be reliably defined from a single parameter combination. Representative SCC values were therefore identified using a rule-based framework integrating physical admissibility, sensitivity to rigidity, and stability across parameter ranges. Of the 32 seismic clusters, 22 yielded admissible SCC solutions and were subsequently used for SCC–CZ characterization. Combining the selected SCC with seismogenic depth yields CZ, enabling a classification that distinguishes tectonic zones according to relative coupling and coupled seismogenic thickness. Because the estimates remain conditional on catalog completeness, FMD extrapolation, fault geometry, rigidity, slip rate, and Mmax, SCC and CZ are interpreted as relative indicators rather than direct measures of fault locking or earthquake probability. The framework provides a reproducible basis for integrating seismic moment budgets and seismogenic structure into regional seismic-hazard characterization.
This study presents a preliminary evaluation of the aggregate potential of representative sedimentary rocks from the Voltaian Supergroup in northern Ghana. Fifteen rock samples were collected from Gambaga, Pigu and Tamale, representing the Bombouaka, Oti-Pendjari and Obosum Groups. They were analysed using petrography, SEM–EDX and standard physico-mechanical tests conducted in accordance with BS 812 and ASTM procedures. Petrographic and microanalytical results indicate that the Bombouaka and Obosum samples are quartz-rich sandstones, whereas the Oti-Pendjari sample is a fine-grained calcareous rock with a micritic carbonate matrix and subordinate siliciclastic constituents. The physico-mechanical results reveal clear lithological contrasts in engineering performance. The Oti-Pendjari rock records the lowest aggregate impact, crushing and Los Angeles abrasion values (16%, 18% and 25%, respectively), indicating superior resistance to impact, crushing and wear. The Obosum sandstone shows moderate performance, whereas the Bombouaka sandstone performs poorly despite its high quartz content. These results demonstrate that aggregate quality in the Voltaian Supergroup is governed not only by mineralogical maturity, but also by textural and diagenetic controls, including grain support, matrix content and cementation. The study provides the first integrated preliminary dataset linking petrographic characteristics with engineering behaviour for selected Voltaian sedimentary rocks, and highlights the need to evaluate sedimentary aggregate resources based on fabric and rock quality rather than quartz abundance alone.
The upper mantle part of the Bela Ophiolite Complex in western Pakistan comprises mainly depleted harzburgites and dunites with associated podiform chromitites. This study analyzes the mineral compositions and whole-rock chemistry of these rocks, including major, trace and platinum group elements as well as Re-Os isotopic data, to provide constraints on their mantle melt evolution and petrogenesis. Cr-spinels in the harzburgites have lower Cr# values (42.7-44.6) than the Cr-spinels in the dunites (69.3-71.7) and chromitites (79.1-79.9). The harzburgites contain substantial Al2O3 (1.22 wt%), and CaO (1.63 wt%) but are depleted in ∑REE (0.521 ppm), which, together with their 187Os/188Os (0.11364 to 0.12582) and 187Re/188Os ratios (0.0139 to 0.2816), suggest a depleted residual mantle origin. Comparatively, the dunites have lower average Al2O3 (0.35 wt%) and CaO (0.38 wt%) as well as ∑REE (0.174 ppm) contents, although their 187Os/188Os (0.12979 to 0.14422) and 187Re/188Os ratios (0.0457 to 1.2179) are higher than those of the harzburgites. The chromitites also display higher 187Os/188Os (0.12611 to 0.13114) and 187Re/188Os ratios (0.0107 to 1.1102) than those of the harzburgites. These results indicate that the Bela dunites underwent modification due to interaction and/or equilibrium with melts. The mantle-normalized trace-element data of the harzburgites imply a lesser degree of partial melting (∼15.7 %) compared to that of the dunites (∼20.5 %). The data further demonstrate two distinct stages in the genesis of the Bela peridotites and chromitites. In the first stage, the harzburgites formed as a mantle residual product after low-degree partial melting in a mid-ocean ridge (MOR) environment. In the second stage, the dunites and chromitites formed after high-degree partial melting of the depleted mantle, and refertilization of dunites occurred in the forearc mantle in a supra-subduction zone (SSZ) environment. The dunites and chromitites crystallized as a result of interactions between boninitic melts and residual peridotites within the mantle wedge. This two-stage history highlights the transition from MOR to SSZ environments in the formation of the Bela Ophiolite Complex. The remarkable heterogeneity of Os isotopic compositions in this region of the Neo-Tethyan upper mantle reflects diverse processes of melt generation and extraction during its tectonic evolution.
The Yechangping Mo–W deposit in the East Qinling Orogen is a giant porphyry-skarn system, but the differences in genesis between its barren monzogranitic porphyry and mineralized granitic porphyry remain poorly defined. This study presents new zircon U–Pb ages, Hf isotopes, whole-rock geochemistry, Nd–Pb isotopes, and pyrite sulfur isotopes to elucidate the petrogenesis and key controls on Mo–W mineralization. Zircon U–Pb dating yields indistinguishable emplacement ages of 146.4 ± 2.3 Ma for the barren porphyry and 147.5 ± 2.0 Ma for the mineralized porphyry, indicating synchronous magmatism. Both intrusions are I-type granites, characterized by negative εHf(t) (−14.69 to −9.95) and εNd(t) (−15.22 to −12.33) values, Paleoproterozoic two-stage model ages (1.83–2.17 Ga), and Pb isotopic compositions similar to the Taihua Group basement, indicating a dominantly ancient crustal source from the Taihua Supergroup with a possible minor contribution from the North Qinling Accretionary Belt. The higher degree of fractional crystallization and moderately oxidized conditions (avg. logƒO2 = −13.11) of the mineralized porphyry are the key factors controlling Mo–W mineralization. Pyrite grains from both porphyry-type and skarn-type ore bodies yield δ34S values ranging from 3.16‰ to 5.35‰, indicating a common magmatic sulfur source. Furthermore, the restriction of scheelite to skarn orebodies highlights the fundamental role of carbonate wall–rock interaction in localizing tungsten mineralization.
