Solid Earth Sciences最新文献

Groundwater, a primary freshwater source for potable and agricultural uses, is increasingly threatened in southern coastal areas of Bangladesh because of rapid urbanization, industrialization, and climate change. Bagerhat, one of the coastal districts, faces not only frequent tropical cyclones, inundation of low-lying areas, and saline water intrusion but also rapid urbanization, population growth, and pollution from prawn culture and seafood processing industries. The study aims to assess the hydrogeochemistry and the suitability of groundwater based on its significance for potable and irrigation purposes in Bagerhat District. This research includes an integrated approach of hydrogeochemical, geospatial, and multivariate statistical methods to investigate the hydrogeochemical processes and groundwater quality using ninety groundwater samples from existing deep tube wells (around 350 m depth). The hydrogeochemical analysis determined the concentrations of major cations and anions were Na⁺>Mg²⁺> Ca²⁺> K⁺ and Cl⁻ > HCO₃^- > SO₄²⁻ > NO₃^-, correspondingly. Electrical Conductivity (EC) values ranged from 16,260 μS/cm in the southern Mongla Upazila to a minimum of 560 μS/cm in Chitalmari Upazila. The evaporation–crystallization processes were found to be the primary mechanism influencing groundwater chemistry in the study area. Multivariate statistics, including Pearson correlation matrix, principal component analysis (PCA), and cluster analysis, indicated that geogenic processes govern groundwater chemistry. The spatial distribution of the water quality index (WQI) map demonstrated that only 15% of groundwater samples are suitable for drinking in the central and eastern parts, while 85% are unsuitable in the study area. Furthermore, evaluation of irrigation water quality parameters, such as sodium percentage (Na%), sodium adsorption ratio (SAR), Kelly ratio (KR), permeability index (PI), magnesium hazard (MH), and salinity hazard, indicated that most wells are unsuitable for irrigation. The results provide insights into aquifer hydrogeochemistry, groundwater quality status, vulnerable areas of pollution, and sustainable, safe water options for groundwater management in the Bagerhat district.

The composition of Nb, Sn, Ta, and W in rutile can serve as a highly sensitive indicator for the mineralization of these elements. This information could also be utilized to discriminate different stages of ore deposition or distinct types of deposits. Precise and accurate measurement of trace-level concentrations of these elements in rutile is imperative for such investigations, and can be effectively achieved using electron probe microanalysis (EPMA). In this study, we employed a CAMECA SX5 field emission EPMA to develop an optimal approach for precise and accurate analysis of trace-level Nb, Sn, Ta, and W in rutile. The analytical conditions include an accelerating voltage of 25 kV, a beam current of 200 nA, a beam diameter of 1 μm, optimized background positions for Nb Lα, Sn Lα, Ta Lα, and W Lα, and aggregate intensity counting with a peak counting time of 240 s for each element per spectrometer. The detection limits (3σ) for Nb, Sn, Ta, and W ranged from 22 to 53 ppm. The highest achievable spatial resolution was approximately 4.3 μm. Analytical results obtained from potential rutile standards R10 and R632 were consistent with previous studies within the errors. The precision of these results varied from 1% to 10% (1σ), excluding W in R10 and Nb and Ta in R632, which exceeds the precision achieved in previous EPMA studies. We recommend using R10 as a reference standard for analyses of trace-level Nb, Sn, and Ta, and R632 as an appropriate reference standard for Sn and W when quantifying rutile using EPMA.

In this study, we report for the first time a new gabbro diorite, forming in an intraplate extensional environment during the Early Devonian, in the Shimian of the western margin of the Yangtze Block. Zircon SIMS U–Pb dating indicates that the gabbro diorite formed at ca. 406 Ma. This gabbro diorite belongs to low-K tholeiite and has enriched in Rb, Ba, K, Pb, negative anomalies of Nb, Ta, depletion of flat LREE patterns, negative ε_Hf(t) (−1.1 to −11.7), and high δ¹⁸O (8.83 ± 0.21‰) ratios, showing that the magma formed by partial melting of N-MROB-type mantle and indicating that the magma underwent crustal contamination during emplacement. The magma is formed in the extensional environment, which provides evidence for the extensional environment in the western margin of the Yangtze. The geochemical characteristics and emplacement time of the rocks are similar to those in the early Paleozoic post-orogenic mafic rocks in South China, suggesting that the gabbro diorite may be influenced by the early Paleozoic orogeny in South China.

The geochemical and tectonic characteristics of volcanic formations in Central Java, specifically the Sumbing-Slamet volcanics, were investigated to understand the processes associated with slab failure in the region. Through comprehensive geochemical analysis and comparison with other volcanic formations, insights into the magmatic evolution and tectonic settings of the Sumbing-Slamet volcanics were gained. The findings support the hypothesis of slab tearing beneath Central Java, as evidenced by distinct geochemical signatures and magmatic interactions observed in the Sumbing-Slamet volcanics. Geochemical data reveal medium to high potassium content (K₂O = 0.77–2.32%), low Nb/Y (<0.6561), low TiO₂ relative to Al₂O₃ [TiO₂ < (−1.1610 + 0.1935 × Al₂O₃)], Th/La >0.2, as well as a wide range of Nb/La and Nb/Zr (0.14–0.89 and 0.0304–0.0744, respectively), notable depletions in high-field strength elements (HFSE; such as Nb, Ti), low to high Ta-anomaly (δTa = 0.21–1.03), and whole-rock isotopes of ⁸⁷Sr/⁸⁶Sr (0.704458–0.705800) and ¹⁴³Nd/¹⁴⁴Nd (0.513059–0.512766) demonstrate that they were formed from active continental margin (ACM) tectonics involving subducted sediment input. These magmatic processes likely resulted from the mixing of lithospheric and asthenospheric mantle sources due to slab failure in the northern part of Central Java. The research contributes to strengthening the geophysical view regarding the existence of slab tearing in Central Java, understanding the dynamic geological processes occurring in subduction zones, and emphasizing the importance of interdisciplinary approaches in studying such phenomena.

Water utilization for different human activities is universally crucial, but it is not readily available for consumption in some areas, such as the central parts of Lagos State, Nigeria. Moreover, there are many groundwater controlling factors (GWCFs) spanning geological, geophysical, and hydrological factors that contribute to this scenario, coupled with uncertainties that necessitate their careful selection using appropriate modelling techniques. In this study, the Dempster–Shafer Theory of Evidential Belief Function (DST-EBF) model (a coupling approach) was deployed to produce a groundwater prospectivity zonation (GWPZ) map for the study areas. The choice of the selected locations was informed by the continued dearth of water supplies, necessitating the need to discover new locations or re-appraise the existing ones for groundwater resource development. Furthermore, remote sensing, geological, field geophysical, and hydrological datasets that constituted GWCFs were integrated into a Geographic Information System (GIS) environment. Next, the computed values for the evidence of the mass functions (i.e., belief, disbelief, uncertainty, and plausibility) were combined using the Dempster–Shafer combination rule and then interpolated using the Inverse Distance Weighted (IDW) method. Subsequently, the GWPZ map was generated and classified into five zones, ranging from very low to high prospectivity zones. The GWPZ map was validated using cross-validation to estimate statistical errors, the receiver operating characteristic (ROC) curve, and the use of inverted resistivity models from the 2D electrical resistivity imaging surveys. All the metrics used for the validation provided good account for the classified GWPZ map. The north-eastern and the south-central parts are the most promising regions for groundwater, which could be harnessed for sustainable development through borehole drilling. Thus, the integration of the DST-EBF model and GIS for effective groundwater resources and uncertainty mapping was quite successful and impressively reliable.

The polyphase deformation features and detachment faults on the northern (Gumusler) and southern (Camardı) borders of the Nigde Massif rocks, as well as the structures developed as a result of these faults, are investigated in this paper. The Nigde Massif in the studied areas is basement Palaeozoic–Mesozoic metamorphic units. The Late Cretaceous Uckapılı granodiorite and Sineksizyayla meta-gabbro introduced the Nigde massif. These units are overlain unconformably by Late Cretaceous-Quaternary rocks. The metamorphic rocks on the massif's southern edge underwent 5-phase ductile deformation, whereas the metamorphic rocks on the northern margin underwent 3-phase folding. Both the northern and southern edges include post-Middle Eocene extensional detachment features. These are most likely extensional detachment faults related to the massif's uplift. Central Anatolia is still under an extensional tectonic regime today. Therefore, detachment fault activity and occurrence continue. A large portion of the low-angle normal faults shows an extensional detachment feature. The detachment faults identified north and south of the study area are also active today.

In the southern part of the Siberian platform, a new genetic type of lithium mineralization was discovered in the Lower Cambrian halogen-carbonate formation of the Angara-Lena marginal trough, which arose as a result of the introduction of a fluid-saturated solution into the sedimentary cover of the platform. Focal hydrothermal development of halogen-carbonate deposits along deep faults led to the formation of lithium-bearing mineralization. A gradual reduction in tectonic activity within the Angara-Lena marginal trough was accompanied by the subsidence of hydrothermal-sedimentary deposits. In this case, the precipitated substance was dispersed and later transformed into layers. It has been established that the main lithium minerals are hectorite and lithiophorite. The results of a study of lithological and geochemical associations of rare earth elements in sections of Early Cambrian deposits of the studied lithium mineralization are presented.

The scarcity of the early Precambrian geological record limits our comprehension of crucial information concerning interactions between the crust and mantle, mechanisms involved in subduction zone arc-continental collisions, as well as patterns of mantle enrichment and crustal growth during this epoch. The Dengfeng terrane in the North China Craton provides significant data on Precambrian crustal evolution, particularly within the Neoarchean magmatic suites. Our study focuses on a variety of basic rocks across several locations in this region. Basic rocks from Huishansi and Sanhuangzhai (2558–2525 Ma) exhibit characteristics such as low SiO₂ (45.44–56.54 wt%), K₂O (0.77–2.7 wt%), Na₂O (1.66–4.51 wt%), and high MgO (4.66–11.22 wt%) and FeO_T (8.17–13.77 wt%). Similarly, basic rocks from Shipaihe and Guojiayao (2480 Ma) also display low SiO₂ (46.16–52.48 wt%), K₂O (0.24–1.28 wt%), and Na₂O (1.87–3.75 wt%), with FeO_T (1.07–2.31 wt%), but feature higher content of MgO (5.33–8.83 wt%) and Mg^# (44–62, averaging 53). Both sets exhibit relatively flat REE patterns and weak negative anomalies in Nb, Ta, and Ti, corresponding to a tholeiitic basalt composition for the protoliths. Analyzing low (Hf/Sm)_N, (Nb/La)_N, and Th/Yb ratios, coupled with depleted HFSE, suggests potential crustal contamination in the rocks from Huishansi and Sanhuangzhai. Further, based on low V/Sc ratios (5.38–10.27, average 7.02) and depleted zircon Ɛ_Hf(t) values, our proposition is that the magma was sourced through partial melting of a depleted and relatively reduced mantle source. These findings offer valuable insights into the tectonic evolution of the Dengfeng terrane, spanning from subduction to post-collisional extension.

Litho-stratigraphic characterization within hydrogeological units of a major aquifer system in Southern Nigeria was carried out using Electrical Resistivity (ER), Stratigraphic Modified Lorenz Plots (SMLP), and Flow Zone Indicator (FZI) algorithms. The aim of integrating these technologies was to generate hydraulic flow units (HFU) that would describe the speed of flow and efficiency within the aquifer's stratigraphic units. Electrical Resistivity technology delineated four geoelectric layers within the study area: motley topsoil, coarse sand, fine sand, and sandy clay, with the aquiferous formation being the third layer. Via measures obtained from geo-electrical data, major geo-hydraulic parameters were estimated. The hydraulic conductivity ranged from 3.1 x 10⁻⁵ to 9.3 x 10⁻⁵ m/s, effective porosity ranged from 0.33 to 0.54, permeability ranged from 4362.9 to 13143.4 mD, tortuosity ranged from 0.85 to 0.97, Aquifer Quality Index (AQI) values ranged from 3.57 to 4.88 and Flow Zone Indicator values ranged from 4.11 to 7.00. The Stratigraphic Modified Lorenz Plots delineated the presence of three hydraulic flow units within the region. The first hydraulic flow zone was a superconductor with good efficiency ranking; the second and third flow zones were conductors having fair efficiency rankings. Results obtained from measures of Aquifer Quality Index (AQI) were employed to generate Discrete Rock Typing (DRT) results which indicated the presence of two distinct aquifer rock matrix types. The Dykstra-Parson co-efficient, employed in evaluation of aquifer heterogeneity, gave a value of unity, indicating perfect heterogeneity of the aquifer.

Provenance and stratigraphic correlations across the exposed Eocene-Miocene sedimentary sequences of southern Nigeria that exhibit similar lithologies and are biostratigraphically-barren have been carried out. Heavy mineral assemblages in the 63–250 μm sand fractions of 43 sediment samples across the sedimentary sequences were assessed via wet-sieving, centrifugation, and polarizing petrologic microscopic analyses. Opaque, apatite, garnet, kyanite, zircon, rutile, staurolite, tourmaline, and epidote heavy mineral species were identified and point-counted. Electron microprobe analysis was carried out on the garnet-heavy mineral species using a CAMEBAX Cameca electron microprobe with a link four-wavelength energy-dispersive mode spectrometer analyser. This study revealed the existence of three heavy mineral associations and three lithostratigraphic formations. Heavy mineral association A is characterized by assemblages of kyanite, zircon, and rutile grains. The occurrence of kyanite in this association indicates derivation from schist and gneissic rocks. Zircon grains indicate sialic to intermediate igneous rocks derivatives that has sustained several periods of recycling, and redeposition. The occurrence of rutile indicates metamafic and metapelitic rocks with other sources being minor. Heavy mineral association B is characterized by assemblages of staurolite, opaque materials, garnet, and epidote. The presence of opaque grains indicates a shorter distance of transport possibly from proximity. The occurrence of staurolite grains indicates metamorphic and magmatic rock derivatives from schists, slates, and gneisses. Garnets are predominantly derived from high-grade metamorphic rock (granulite-facies) metasediments and charnockites and lower grade (amphibolite-facies) metasedimentary rocks and granitoids. An epidote is a metamorphosed igneous rock derived from the adjoining radix. Heavy mineral association C is characterized by assemblages of tourmaline and apatite. Tourmaline grains indicate pneumatolytic rocks, pegmatite, schist, gneisses, and marble source rocks. Apatite indicates derivation from local outcrops exposed during the Benue Trough uplift. The occurrence of apatite and its assemblages with tourmaline indicate felsic igneous rocks with ultramafic compositions, metamorphic rocks with low to high grades and derivatives of diverse protolith compositions. The exposed Eocene-Miocene sedimentary deposits that exhibit similar lithologies and biodata are relatively lacking. They were differentiated into three different lithostratigraphic formations and correlated. These analyses were performed using heavy mineral characterization, optical property, garnet geochemical composition, and inference supported by multivariate statistical analyses. Variations in the numerical values of unstable heavy minerals reveal dissolution and overgrowth through acidic groundwater, changes in climatic conditions, and relative eustatic sea-level changes. Th