Geosystems and Geoenvironment最新文献

Recent technological advancement has revolutionized the field of non-traditional stable metal and metalloid isotopes for their wide range of applications, from the study of earth surface and interior processes, reconstructing past oceanic environments, tracing contaminants to biomedical investigations. Beyond the conventional stable isotopes (e.g., H, C, O, N, S), this field now explores a diverse array of stable isotopes (e.g., Li, B, Mg, Si, Ca, K, V, Cr, Ni, Fe, Cu, Zn, Sr, Mo, Cd, Ba, Hg, U) and their potential applications. This review delves into the applications of stable metal and metalloid isotopes as an important tool for tracing sources and elucidating various processes within the realm of earth, ocean, and environmental studies. The fundamental concept of mass-dependent and -independent isotope fractionations are introduced first in this article, followed by a discussion on the selected "emerging" stable isotopes like Li isotopes (δ⁷Li), B isotopes (δ¹¹B), and Mo isotopes (δ⁹⁸Mo) and highlighted their applications as a proxy for earth surface processes, paleo-pH, and paleo-redox conditions in oceans respectively ; various measurement techniques and their advantages/disadvantages including chemical extractions of elements of interest and their isotope measurements using a Multi-Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS). Finally, this article highlights the caveats and limitations, challenges, and scopes for future research in the field of non-traditional stable isotopes.

Microplastics (MP) are prevalent and virtually present in all environmental domains. Though microplastics are reported worldwide, only limited studies have been carried out in freshwater ecosystems. Therefore, this study was initiated to evaluate the presence of microplastics in a freshwater lake (Vellayani Lake), located in Thiruvananthapuram, Kerala, Southern India. The water quality of this lake assumes significance as it serves as a primary drinking water source for thousands of people in Thiruvananthapuram. This study analyzed the seasonal distribution of microplastics in water samples from three locations within Vellayani Lake under two distinct climatic conditions, identifying microplastics in all sampled locations. During the monsoon sampling, the abundance of MP ranged from 20 to 100 particles/m³, with an average abundance of 65 particles/m³ and a total abundance of 194 particles/m³. However, during the summer, microplastic concentrations ranged from 34 to 67 particles/m³, with an average abundance of 49 particles/m³ and a total abundance of 147 particles/m³. Four varieties of polymers, High-Density Polyethylene (HDPE), Low-Density Polyethylene (LDPE), Polypropylene (PP), and Polyethylene Terephthalate (PET), have been detected. HDPE is the most abundant polymer in the water, along with PP, PET, and LDPE. The dominance of Polyethylene and Polypropylene polymers in the lake water samples highlights the rapid disintegration of single-use disposable plastics. The consumption of microplastics has been proven to be harmful, and their long residence time and widespread presence in the water make it necessary to develop new purification techniques to specifically target plastic contaminants.

Floods are frequent natural hazards that cause widespread destruction, particularly in low-elevated areas. This study focuses on identifying flood susceptible zones in the Kashmir Valley, known for historical flooding attributed to the overflow of the Jhelum River. Various Multi-Criteria Decision Making (MCDM) techniques, including Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), Vise Kriterijumska Optimizacijai Compromission Resenje (VIKOR), and Evaluation Based on Distance from Average Solution (EDAS), were employed in this research. A total of 17 multidimensional factors were considered, and multicollinearity tests revealed no correlation among these factors. The results of the MCDM models indicate that areas along the Jhelum River are classified under very high flood susceptible zone. Specifically, Srinagar city is consistently classified under very high flood susceptible zone by all three models. Approximately 4.27 %, 9.67 %, and 5.39 % of the total area were identified as very high susceptible areas by TOPSIS, VIKOR, and EDAS, respectively. The models exhibited robust performance, as evidenced by the Area Under the Curve of the Receiver Operating Characteristics curve (AUC-ROC). Notably, VIKOR demonstrated excellent performance among the three models in generating flood susceptible maps. The favorable outcomes of these models underscore their potential application in similar regions facing comparable challenges. This study carries significant implications for policymakers, administrators, and local authorities involved in flood management within the Kashmir Valley. The insights provided can inform proactive measures and strategies to mitigate the impact of floods and enhance the overall resilience of the region.

Geophysical investigations are mostly used for hydrogeological studies, mining, geotechnical investigation and environmental surveys. Geophysical investigation of groundwater within the dumpsite is highly critical because the extent of interaction between leachate plume/contaminated zone and aquifer zones could significantly reduce groundwater quality. The textural complexity and clay content of soils could change their electrical properties, thus reflecting inconsistent resistivity values using the resistivity method. This research investigates the extent of leachate infiltration from waste dumpsite into groundwater at Gyadi-Gyadi Kano State, using natural Electromagnetic (EM) field and Vertical Electrical Sounding (VES) methods. Six natural EM profiles were obtained in various locations within the study area using PQWT-TC 150 model. Six VES data points were occupied along the EM profile lines using SAS 1000 ABEM resistivity meter. The two techniques employed revealed some intercalations of low resistivity (conductive) as well as very low electrical potential differences in the study area. The low resistivity media are mixtures of leachates into groundwater units, thereby creating formations from the surface to a depth of about 40 m. The first and second layers have experience leachate-aquifer interaction in the northern, southern and eastern parts of the study area to about 40 m depth, and the leachate-aquifer interaction has extended to the deep aquifer of about 70 m depth at the western part. Shallow aquifer has not been infiltrated by leachate at about >100 m away from the waste dumpsite. Therefore, for potable groundwater exploitation in this area, it is advised that boreholes should be sited >100 m away from the dumpsite, where leachate-aquifer interaction has attenuated. The natural EM field detector is evidently constrained by issues of over-generalization and summation of potential values, probably due to its relatively low resolution. Hence it might not be capable of precisely delineating varying geological units. In contrast, the resistivity method is able to delineate and discretize the subsurface into sub-units of different resistive zones. This implies that VES is better suited for accurately defining the true subsurface geology, while the NEF detector is effective for determining the extent of a leachate plume.

Shiriya River Basin (SRB) of Kasaragod district, Kerala, is one of the minor river basins that faces acute water shortage soon after the rainy season. Increasing the aquifer productivity of the SRB is the need of the hour. The present study is performed to determine the groundwater potential zones (GWPZ) of the SRB through Weighted Overlay Analysis. Different thematic layers (Geomorphology, Geology, Lineament density, Slope, Drainage density, LULC, and Soil) were prepared. Based on Saaty's scale, the rank and weightage assigned to each thematic layer and their respective features were standardized through the AHP techniques. Subsequently, GIS-based Weighted Overlay Analysis generated the ultimate GWPZ map, dividing SRB into 3 potential zones (poor, moderate, and good). To validate the GWPZ and understand the geoelectric characteristics of the SRB, 50 Schlumberger VES were performed and analyzed. Depth to water level data is also used to validate the GWPZ. The VES data indicated three distinct geoelectric layers, the topsoil, laterite, and weathered/fractured basement, overlying the resistive basement. In the SRB second layer (laterite) and, in some regions, the third layer (fractured charnockite) functions as an aquifer. The presence of groundwater potential region is indicated by resistivity values ranging from 50 to 200 ohm-m. The combination of surface and subsurface indicators of GWPZ will be much more reliable in locating the site for sustainable groundwater exploration and management of SRB groundwater resources.

The magma source for mafic dykes from South Rewa Basin (SRB) in central India is invariably linked to Rajmahal volcanism (117 Ma) for Damodar, Raniganj-Jharia, and Bengal basin (Permian - Quaternary) to the east, and Deccan volcanism (66 Ma) for Satpura Basin to the west of SRB. However, the magmatic events linked to the SRB are not explicit. To ascertain the dyke association with these volcanic events, we performed a comprehensive paleomagnetic study on the exposed dykes and basalts from Shahdol region in SRB. Rock magnetism indicate that magnetite or titano-magnetite is the main remanence carrier mineral in these dykes. The measured directions produce a mean declination (Dm) of 338° and mean inclination (Im) of - 35° (α₉₅= 8.4°, k = 25.3, N = 13), is close to Deccan normal directions. The calculated Pole position (λ_p) is at 42.02°N, and (Lp) is at 289.33°E, suggesting that the studied dykes are emplaced simultaneously along with Deccan Traps (36.96°N/78.70°W) and not of Rajmahal Traps (11.37°N/297.58°E). These dykes can be the result of multiple Deccan magma intrusions along the Narmada-Tapti lineament and intra-basinal faults in the SRB of central India.

The Babouri-Figuil and Mayo Oulo-Lere basins located in Northern Cameroon are small elongated sedimentary asymmetric half-grabens associated with the development of the West and Central African Rift System (WCARS). The evolution of these basins began during the Precambrian pre-rift period and continued through the Late Jurassic - Early Cretaceous periods, although details of their development remain unclear. The aim of this study is to understand the evolution and development of the border faults and their control on syn-rift geometry, accommodation space, and the resulting stratigraphic architecture. Using a combination of multiples surface and subsurface well logs data, we demonstrate the relationship and evolution of various stages of rifting and the associated sedimentary architecture. The basin is composed of an alluvial to lacustrine succession that developed during its tectonic evolution. A 3-stage tectonic model is proposed for the evolution of the basin that uses fault propagation analysis to describe the sedimentary architecture and evolution of basin geometry. The three stages of the model are the early rift, rift climax, and late rift; here, the early rifting phase is marked by the reactivation of faults in the Lower Cretaceous. The rift climax phase resulted in the interconnection of small segmented border faults leading to the high rate of activation of major border faults and to the development of the half graben structure of the basins. The late rift stage is marked by a decrease in border fault activity and accommodation. Sediment distribution and the facies architecture are controlled by tectonic subsidence created throughout the rifting phases. The stratigraphic signature of the Babouri-Figuil and Mayo Oulo-Lere basins are punctuated by the lacustrine water transgression-regression cycles, and controlled by the balance between the rate of sediment supply and tectonic accommodation. The progressive change between overfilled to starved sedimentary architecture is illustrated by this stratigraphic succession. Additional age assessment and sub-surface data in future work could help confirm the structures identified on the surface.

The growing need of rare earth elements in different sectors of the modern-day world has led to their increasing demand, which is in accordance with their limited supply. In such a scenario, investigations related to search for potential zones of rare earths have become the need of the hour. In one such investigation, undertaken by Geological Survey of India, the authors report profuse intrusion of the apatite veins into the syenite-pyroxenite suite in the eastern part of the Eastern Ghats Mobile Belt (EGMB) in Nayagarh area of eastern Odisha. These apatite veins are anomalously rich in REEs, particularly LREEs, which on average ranges between 37,000 to 53,000 ppm. Rare earths and apatite are generally directly proportional, where apatites tend to carry sufficient REE budget, depending on the phosphorous fugacity and other ambient conditions inducing their genesis. The major-oxide chemistry of apatite veins indicates that apatites in the study area can be divided into two types based on SiO₂ wt.% and their inverse relationship with P₂O₅ and CaO wt.%. Mineral chemistry data shows overall SiO₂ depletion, with dominance of CaO, followed by P₂O₅. Apatite veins, as per mineral chemistry, contain numerous veinlets (identified microscopically), where one type is REE-bearing and another type is REE-free. The REE-bearing phases are rich in Ce, Nd, La and Pr and are represented by allanite, monazite, and bastnaesite. Thorite and zircon are prevalent. Earlier instances of apatite intrusions into granulite have been reported from parts of south India. On the contrary, in this area, the intrusion is typically restricted to the younger intrusive units of the EGMB, represented by syenite-pyroxenite suite. The intrusives also show moderately high values of REEs. In this paper, an attempt has been made to characterize the apatite veins and the syenite-pyroxenite suite, they have intruded, in respect to their mineralogy and tectonics and to elucidate the potentiality of the area in terms of future REE exploration.

Accessible silicate reservoirs on Earth (i.e., the depleted mantle and continental crust) are depleted in Nb relative to chondrites, as expressed by their subchondritic Nb/Ta ratios. Mixtures of continental crust and depleted mantle cannot produce chondritic Nb/Ta ratios; therefore, another geochemical reservoir with a superchondritic Nb/Ta ratio is necessary to balance the low Nb contents of the continental crust. We investigated alkaline igneous rocks with superchondritic Nb/Ta ratios (20.4–24.8). Their high Nb/Ta ratios were inherited from their lithospheric mantle source rather than being produced by magmatic differentiation. Geochemical data show that an enriched mantle domain with superchondritic Nb/Ta ratios can be produced by the interaction of subducted carbonate-rich sediment-derived melts with the lithospheric mantle, and the enriched lithospheric mantle is a potential superchondritic reservoir.

The Bundelkhand Craton (BuC) represents a significant Archean terrane within the northern Indian Craton and yet its tectono-metamorphic evolutionary history remains relatively understudied. Our investigation involves detailed petrography, geochemistry, and bulk composition modeling of both garnet-bearing and garnet-absent amphibolites with a two-fold objective: (i) to constrain the protolithic nature and tectonic settings involved in the genesis of these rocks, and (ii) to propose a tectono-metamorphic evolutionary history for the BuC. The BuC amphibolites originate from basalt and andesitic-basalt protoliths. Their trace element compositions reveal negative anomalies in Nb, Ta, and Ti, while their rare earth element (REE) normalized patterns indicate enrichment in light REEs over heavy REEs. The basaltic protolith is interpreted to have formed during orogeny in a compressional tectonic regime at the active margins of island arcs in a subduction-related setting. This interpretation is supported by various discrimination plots for amphibolites, such as Nb/Th vs Zr/Nb, Zr vs Zr/Y, and Th/Nb vs Ce/Nb, as well as high Th/Yb and low Nb/Yb contents— all of which suggest an island arc setting influenced by subduction. These amphibolites have undergone three distinct phases of metamorphism, as evidenced by petrography, mineral chemistry, and bulk composition modeling. This interpretation is further supported by geochemical discrimination diagrams which indicate that a subduction tectonic setting was active during peak metamorphism. During the pre-peak phase, the garnet-bearing amphibolites experienced pressure and temperature conditions ranging from 6.25 to 6.5 kbar and 580 to 590ºC, while the garnet-absent amphibolites underwent conditions from 5.0 to 5.8 kbar and 400 to 450ºC. Peak metamorphism was observed at pressures ranging from 6.8 to 7.4 kbar and temperatures from 760 to 805ºC for the garnet-bearing amphibolites, and at pressures from 7.0 to 7.4 kbar and temperatures from 785 to 810ºC for the garnet-absent amphibolites. The metamorphic retrograde conditions for the garnet-bearing amphibolites are defined by P-T conditions ranging from 4.45 to 4.75 kbar and 585 to 615ºC, while for the garnet-absent amphibolites, it ranges from 3.1 to 4.0 kbar and 620 to 710ºC. The mineral assemblages and P-T conditions delineate a clockwise P-T path for both, garnet-bearing and garnet-absent amphibolites from the Babina and Mauranipur regions. This suggests that the rocks underwent a burial process amid subduction tectonic settings in an arc-related environment, followed by a decompression stage that brought them to the surface.