Arabian Journal of Geosciences最新文献

The source of the gold (Au) in the Au-bearing stream sediments within the central parts of Tanzania is poorly constrained. Hence, this study aims to elucidate the sources of these Au-bearing sediments and gold using whole-rock geochemistry of stream sediments and multivariate statistics. From the CIA values, the sediments are weakly weathered and compositionally immature, considering the ICV and Fe/K values, under humid climatic conditions. The source ratio proxies: Th/Sc, Th/U, Cr/Th, La/Sc, and Th/Cr, indicate a felsic igneous rock source. The discriminant plots show intermediate and mafic rocks, while the multivariate indicates a dominant mafic source rock with 40.35% relative to 18.70% extraction variance for felsic rocks. The Au, however, does not associate with mafic rocks (Ni, Co, V, and Cr) or felsic rocks (Th, Sr, Rb, and K), with all these independent parameters revealing a > 0.05 p-value from the multilinear regression model (MLM). The study will recommend the use of a multi-method approach in the search for Au within the central parts of Tanzania, where soil/rock geochemistry is combined with stream sediment geochemistry and the data processed using multivariate statistics together with machine learning methods, e.g., artificial neural network.

Lime treatment has long been used in construction for its cost-effectiveness and simplicity. In clay soils, lime induces chemical reactions that enhance workability and reduce plasticity, followed by gradual strength development. Despite extensive research on clay–lime interactions, the mechanisms behind these transformations remain partly unclear. This study focuses on the fundamental process driving strength gain. Bentonite samples were treated with lime and with other reagents, calcium chloride, barium chloride, and sodium hydroxide, chosen for their potentially similar behavior (electrolyte concentration and pH increase). Changes in plasticity, grain size distribution (GSD), and strength were assessed and compared to gain insight into the lime–clay mechanisms of reaction. A dispersing agent was also used to test the durability of lime-induced effects. Results revealed all additives reduced liquid limit, indicating increased floc size with additive content. However, only lime significantly raised the plastic limit, confirming persistence of the flocs that formed. GSD analyses showed lime caused fine clay particles to cluster, with cluster size growing with curing time. These lime-induced clusters remained intact, unlike those formed by other reagents, which broke down under manipulation or dispersant exposure. Crucially, only lime led to measurable strength development. Findings suggest clay–lime reactions begin with a resilient flocculation, followed by a slow chemical process that produces cementitious bonds within clusters. Other reagents appear to act through reversible electrostatic effects. The study also shows that low lime content fails to trigger the reaction, as the conditions of the pore water chemistry favor dispersion over flocculation. The short-term stability of lime–clay formed flocs observed in this study is attributed to an early clay–lime chemical reaction whose nature is inconclusively explained until today.

This study investigates shear deformation of the casing during shale gas well fracturing through mechanical analysis and deformation calculations. We evaluated casing deformation induced by natural fracture shear slip, critical slip activation conditions, and key factors governing casing shear stress and deformation. The results demonstrate that elevated fluid pressure within natural fractures increases both the shear stress on the casing and the range of fracture approach angles favorable for shear activation. Consequently, this elevates the likelihood of shear-activated fractures and the associated risk of casing shear deformation. And maximum shear stress occurs within fracture approach angles of 30–45° and their supplementary range. For wellbores intersecting well-developed natural fractures, maintaining fluid pressure below the critical shear strength threshold during hydraulic fracturing operations mitigates casing deformation risks by preventing induced shear slip. Shear stress of the casing is positively correlated with horizontal in situ stress difference, natural fracture length, and the Young’s modulus and Poisson’s ratio of the cement sheath and casing. Conversely, it is negatively correlated with the Young's modulus and Poisson's ratio of the formation rock, the friction coefficient, and casing wall thickness. Variations in the Young's modulus and Poisson's ratio of the casing material itself exhibit minimal impact on casing shear stress. Using cement possessing a low Young’s modulus and a low Poisson’s ratio for well cementation effectively mitigates casing shear failure. Higher Young’s modulus and Poisson’s ratio values in the formation rock result in reduced casing deformation displacement. Conversely, greater horizontal in situ stress differences and longer natural fracture lengths increase deformation displacement. Within the fracture approach angle range of 0–180°, casing shear deformation exhibits a bimodal distribution, with maxima occurring within the 30–60° range and its supplementary angular interval. Geo-mechanical instability induced by in situ stresses within naturally fractured shale reservoirs constitutes the primary cause of casing deformation. At direct intersections between well trajectories and natural fractures, maintaining a distance from the fracture central zone is advised to minimize induced shear displacement. These findings provide a theoretical foundation for understanding casing shear failure stress-deformation characteristics, elucidating governing mechanisms, and guiding deformation prevention and control strategies.

The Sunai River, a right-bank tributary of the Budhabalanga River in Odisha, originates near Siriapal village in Mayurbhanj district and confluences with the Budhabalanga near Dolagohira village in Baleshwar district, Odisha. The basin, categorized as a 7th order system, covers an area of 1,432.26 km² and a basin length of 63.63 km. The mean stream length ratio (14.06) reflects an advanced stage of erosion and high runoff conditions, indicating active fluvial processes. A bifurcation ratio of 3.85 suggests a stable tectonic setting, while a drainage density of 2.27 km/km² indicates moderate to long overland flow. The drainage texture (6.47) and stream frequency (2.85) point to low infiltration and high surface runoff, increasing susceptibility to erosion. Moreover, the low drainage intensity value (1.25) shows a higher vulnerability to soil erosion, likely exacerbated by sparse vegetation or unconsolidated surface material. Morphometric shape indices form factor (0.35), elongation ratio (0.67), and circulatory ratio (0.35) reveal the basin’s elongated form, which can influence flow concentration and flood risk. The low RHO coefficient (0.15) suggests limited water storage during heavy discharge periods, contributing to flash flood vulnerability. The region exhibits steep slopes and significant elevation variation on the basis of basin relief (1,151 m) and a high relief ratio (18.09). Despite this, the ruggedness number (2.61) reflects a relatively smooth and moderately dissected terrain. The analysis highlights the basin’s dynamic runoff and stream flow behavior, emphasizing the urgent need for integrated and sustainable watershed management strategies to counteract environmental degradation and hydro-geomorphological challenges.

The Buah Formation, a key carbonate unit within the Huqf Supergroup of Oman, was deposited during the latest Ediacaran to early Cambrian (~ 541–530 Ma) and is well-exposed in the Jabal Akhdar (JA) and Huqf regions. These carbonates offer critical insights into early Cambrian diagenetic processes and serve as valuable records for geochemical and isotopic investigations. Samples from both regions were analyzed for carbon, oxygen, and strontium isotopes, along with elemental ratios using multiple mass spectrometry techniques. JA samples exhibit a broader and more variable range of δ¹³C and δ¹⁸O values compared to the more constrained values in Huqf, reflecting more extensive diagenetic overprinting. Positive δ¹³C–δ¹⁸O correlations in both regions indicate diagenetic alteration by meteoric and/or burial fluids. In the JA section, δ¹³C values as low as − 8‰ at lower stratigraphic levels likely result from the oxidation of Neoproterozoic organic carbon, releasing ¹²C-enriched DIC, a signature consistent with the Ediacaran Shuram excursion in the underlying Shuram Formation. Mn/Sr ratios distinguish diagenetic systems, with burial diagenesis and/or organic carbon oxidation dominating in JA, and meteoric diagenesis prevailing in Huqf. Strontium concentrations in Huqf samples range from 20 to 2600 ppm, with most exhibiting uniform ⁸⁷Sr/⁸⁶Sr ratios (~ 0.7088), outside typical marine dolomite values. A subset aligns with marine signatures, suggesting mixed Sr sources including terrigenous, hydrothermal, and weathering-derived inputs. Two δ¹³C-based sample populations (< 0.5‰ and ≥ 0.5‰) in Huqf highlight diagenetic variability with implications for reservoir quality, fluid migration, and source preservation in early Cambrian petroleum systems in Oman.