Atmospheric and Oceanic Sciences

Abstract The interaction between the Tethyan and Paleo‐Pacific subduction systems in Southeast Asia since the Paleozoic is still poorly understood. Hainan Island and Borneo, located near the junction of the Tethyan and Paleo‐Pacific domains, provide the critical regions for understanding the dynamic processes and interaction between the two tectonic domains. Using new and published zircon U‐Pb‐Hf isotopes, and the detrital zircon Eu/Eu* data, we evaluate crustal evolution and the relative crustal‐thickness variations in both regions. The data sets indicate broadly synchronous intervals of reduced apparent crustal thickness inferred from Eu/Eu* at 440–410 Ma, 370–350 Ma, 270–220 Ma and 160–140 Ma, together with largely negative ε Hf ( t ) values through the Paleozoic‐Triassic, which characterized by the mixed mantle‐derived material and older crustal components, probably associated with the Paleo‐Pacific subduction. Jurassic–Cretaceous zircons from Borneo shift to mainly positive ε Hf ( t ), supporting the mantle‐derived material addition and a Tethyan–Paleo‐Pacific double‐subduction system beneath Sundaland. However, the Hainan retains mostly negative ε Hf ( t ), consistent with continued Paleo‐Pacific subduction and older crustal components. These results clarify how the Tethyan and Paleo‐Pacific systems interacted in Southeast Asia.

ABSTRACT In the Ramagiri Schist Belt (RSB) of Eastern Dharwar Craton (EDC), the assemblages of cross-bedded quartzite-pelitic sediments, massive metabasalt/amphibolite, and differentiated volcanics of massive-pillowed-pyroclastic character with co-magmatic basic and acidic intrusives with thin volcaniclastic and nonclastic sediment intercalation are delineated as the discontinuous Western and continuous Eastern arms, respectively. The sediment accumulation in the Western arm is interpreted as bed-load lateral accretion on a gentle basin floor of shallow platform, and as the dump- vertical accretion deposits on the steep floor of a linear rifted trough with a subduction mechanism is interpreted. A linear continuous gravity high over the Eastern arm supports the existence of high-density materials in a linear rifted trough of eastern RSB. Thus, this study proposes an initial shallow platformal sedimentation and the conversion of the same depositional site as a linear rifted trough for the accumulation of thick high-density materials with an E-W convergence and subduction-abduction mechanisms in the overall RSB. The unusual occurrence of spinifex textured-pillowed ultramafic slices within the shallow platformal Western arm is interpreted as the allochthonous ophiolitic fragments with their derivation from the Eastern arm’s subduction zone, and transfer-accumulation of these towards the continental margin by abduction mechanism is envisaged. The syn-tectonic Ramagiri, Anantapur-Bukkapatnam alkali-feldspar granites along the margins of RSB’s rifted trough, in the zones of ductile shear mark the later stage of greenstone development in the RSB. Thus, the overall RSB evolution suggests a late Archaean plate tectonic setting analogous to Meso-Cenozoic processes.

ABSTRACT This study evaluates the mineralisation potential of Proterozoic adakitic plutons from the Elimala and Markanje regions within the Mangalur-Gundlupet Crustal Corridor (MGCC) of the Western Dharwar Craton (WDC). Both plutons exhibit high-pressure crystallisation (13–14.4 kbar in Elimala; upto 38.5 kbar in Markanje), elevated water contents (6.5–7 wt% in Elimala; 10.4–11.9 wt% in Markanje), and oxidising conditions—favourable indicators for porphyry copper fertility. The widespread occurrence of magmatic epidote, confirmed through textural and compositional criteria, further supports high-pressure, hydrous, and oxidised magmatic conditions. These features collectively suggest that both plutons represent fertile magmatic systems, with the Markanje pluton being particularly promising as a target for exploration. Future work should focus on sulphide phase characterisation, palaeo-depth constraints on hydrothermal systems, and structural-geophysical integration. Detailed magnetotelluric and gravity surveys combined with field-based structural mapping are recommended to identify potential fluid pathways and magmatic emplacement zones. These findings represent a significant step towards understanding the fertility of ancient adakitic intrusions in cratonic settings and highlight the potential of the MGCC for porphyry-style Cu ± Au mineralisation.

ABSTRACT This paper embodies the review of the research on Meghalaya coals. The coal deposits of Meghalaya are located within the Lakadong Sandstone Formation, which dates back to the Eocene epoch, and are primarily confined to platformal settings. These coal-bearing successions experienced multiple phases of marine transgressions and regressions during the Eocene epoch. The coalfields are spread across three hilly districts of Meghalaya: Garo, Khasi, and Jaintia Hills. The coals of Meghalaya are low in moisture (<4%), moderate ash yield (up to 28%), high volatile matter (40-60%), and fixed carbon content (>40%). They are rich in carbon content, averaging 75%, with significant hydrogen (more than 4%) and oxygen (<12% average). However, it has low nitrogen content (<1%). The coals are rich in sulphur content, reaching upto 12%, with most sulphur in organic forms, followed by pyritic forms. Petrographic analysis reveals that these coals are predominantly composed of vitrinite, accounting for ~ 70% of the maceral content, with low concentrations of inertinite and moderate liptinite content. Mineral matter is also present in an appreciable amount, reaching up to 21%. The vitrinite reflectance values, ranging from 0.40 to 0.68%, classify these coals as sub-bituminous C to high volatile bituminous type C. The occurrence of single, double, and multicelled teleutospores suggests that these coals have evolved from typical Tertiary flora. Based on maceral composition, the coals of the Garo Hills are interpreted to have originated predominantly in reed-dominated to open-water swamp environments under telmatic to limno-telmatic conditions. In contrast, the coals of the Khasi Hills were primarily formed in forest swamp settings, also influenced by telmatic to limno-telmatic depositional conditions. Additionally, the abundance of resinous material indicates a substantial contribution from coniferous vegetation within the swampy depositional environments. Geochemical analysis suggests that the Meghalaya coals are primarily gas-prone, with limited oil-prone potential, and contain type III kerogen, characterised by a mixed type II/III composition. These coals have a bright prospect due to their low moisture content, low ash, high volatile matter, and high carbon and hydrogen content.

ABSTRACT The present study focuses on the characterisation of quartzites of Alwar-Jaipur sub-basin, one of the three subbasins of Proterozoic North Delhi Fold Belt in NW India, besides Bayana-Lalsot and Khetri sub-basins. The study aims to identify the provenance of the Alwar and Ajabgarh Group quartzites and to decipher their tectonic environment of deposition, using major, trace, and REE geochemistry. The Chemical Index of Alteration (CIA) values of 65.63, 72.13, 67.12, and 75.11 for the Rajgarh, Kankwarhi, Pratapgarh (Alwar Group), and Bharkol (Ajabgarh Group) formations, respectively, suggest a moderately weathered source for them. High Th and La contents, and high Th/Sc, Th/Co, and La/Sc ratios indicate derivation from felsic rocks, wherein LREE enrichment and pronounced negative Eu anomalies point to a feldspar-bearing granite-granodiorite provenance. The poorly sorted Rajgarh, Kankwarhi, and Pratapgarh quartzites were sourced from the nearby Archaean-Palaeoproterozoic granitoids, while the well-sorted, texturally mature Bharkol quartzites were derived from a more distal felsic source region with minor mafic input. Geochemical proxies suggest an active continental margin setting for the Pratapgarh Formation. The Rajgarh Formation quartzites show minor interlayers of mafic flows; however, geochemical characteristics suggest a passive margin setting. Proximal granitic rocks occurring at Ajitgarh, Barodiya, Viratnagar (Bairath), Harsora and Dadikar are interpreted as the most probable sources for the sedimentary detritus.

ABSTRACT The Mesoproterozoic Kaladgi Basin, the northern part of the Dharwar Craton, represents an E-W trending intra-cratonic sedimentary basin that preserves a complex record of deformation within its sedimentary cover. This study examines the deformation patterns of the sedimentary cover in terms of structural geometry and kinematics to understand the tectonic processes that governed basin evolution. Detailed structural analysis reveals the coexistence of adjacent yet laterally overlapping compressional and extensional deformation domains within the cover sequence. The south-central part of the basin is characterised by folds, axial planar cleavage and faults defining a compressional regime with a dominant WNW-ESE to E-W structural grain. In contrast, the northern sector represents an extensional domain marked by homoclinal bedding, southerly dipping normal faults, conjugate tensile-hybrid joints and locally dismembered strata, sharing a broadly E-W structural orientation. A marked contrast exists between the deformation patterns of the sedimentary cover and the underlying basement. While the basement comprises largely undeformed granites in the north and poorly exposed Peninsular Gneissic Complex with a dominant NW-SE structural grain in the south, it shows little evidence of reactivation during cover deformation. This decoupling suggests that deformation of the sedimentary cover was predominantly thin-skinned in nature and likely driven by gravity gliding over a relatively rigid basement. The established structural framework provides tentative implications for mineral resource exploration. Fracture and joint networks in the extensional northern domain may have facilitated hydrocarbon migration, whereas fold culminations and antiforms in the south-central compressional domain could represent potential accumulation zones. Furthermore, the basement-cover unconformity emerges as a structurally favourable locale for unconformity-related uranium mineralisation, consistent with reported uranium anomalies from earlier studies.

Abstract Predicting the partial melting conditions that generate Li‐rich peraluminous melts is of major economic and societal importance. However, existing models disagree on the optimal conditions (e.g., pressure, temperature, protolith) and, consequently, on targets for exploration. A key source of divergence in model outcomes lies in the choices of partition coefficients used to describe lithium distribution between minerals and melt . Here, we use thermodynamic modeling to simulate isobaric stepwise partial melting of a global compilation of pelite compositions, at crustal pressures and considering variable water saturation and melt extraction thresholds, to calculate melt lithium enrichment predicted by four recently published sets. Our results quantify the conditions that maximize lithium enrichment. Depending on choices, the predicted optimal conditions range from high‐pressure, low‐temperature melting of wacke‐like compositions, to intermediate‐pressure, high‐temperature melting of both wacke‐ and shale‐like compositions, or in some cases show limited sensitivity to these parameters. Among these scenarios, the intermediate‐pressure, high‐temperature melting regimes (associated with biotite breakdown) are most consistent with existing geological and geochemical evidence from lithium‐rich granite and pegmatites. Such behavior is produced when lithium is treated as strongly compatible in biotite relative to other minerals, such as is thought to be the case in fluorinated biotite. Moving forward, pressure‐, temperature‐, and composition‐dependent lithium partitioning models—such as recently developed for biotite—will be crucial to accurately evaluate Li behavior in anatectic systems.

Portable gait analysis technology for assessing mobility and balance among older adults in community environments remains an underutilized resource, often due to lack of field validation. To address this gap, we used a mixed-validation approach to evaluate a commercially available portable pressure tile system in terms of measurement accuracy: is it true enough to be believed; and sensitivity: can it detect age-related changes in balance and mobility? Thirty healthy adults were recruited in two cohorts of fifteen: YA = 19-64 years of age, and OA = 65 + years of age, to perform a battery of standing and locomotor tasks (static stand = SS, five-times sit-to-stand = STS, step-up/step-down task = SUSD with dominant and non-dominant lead) using a dual elevation, two-tile, StepScan™ pressure tile system placed upon in-floor mounted AMTI™ force platforms for simultaneous data acquisition. Common parameters for balance and stepping analysis were extracted from centre-of-pressure (CoP) kinematics from both systems and analyzed in terms of absolute agreement between systems (paired t-tests and Intra-Class Correlation, ICC(2,k)) and ability to discriminate by age group (independent t-tests and Pearson R2). Agreement between systems was high (<5mm error, ICC > .9) for most measures, and a small but statistically significant decline in balance and mobility performance was detected in the OA cohort compared to the YA cohort (R2 = .2, p < .05). We conclude that portable, modular, pressure tile systems such as StepScan™ are sufficiently accurate and sensitive for quantifying age-related changes in balance and mobility. Larger scale studies are needed to determine the potential for integrating this technology into routine clinical workflow.

Abstract Comets are crucial objects of study for understanding the early solar system environment, including the origin of Earth's water. The Comet Interceptor (CI) mission is designed to perform a flyby of a long‐period comet, and the Hydrogen Imager (HI) onboard will optically measure the deuterium‐to‐hydrogen (D/H) ratio. Optical measurement of D/H ratios requires high spectral resolution, which has often been achieved by large spectrometers. However, HI achieves this using small glass cells filled with hydrogen or deuterium gas called absorption cells. One challenge is that multiple scattering of Lyman‐alpha (Ly‐) radiation in inner comae makes it difficult to accurately deduce hydrogen atom density from the observed Ly‐ radiance. To address this challenge, here, we combined performance evaluation experiments of the absorption cell with a radiative transfer model to evaluate the feasibility of determining cometary D/H ratios using small telescopes mounted on ultra‐small satellites. Through calculations of the signal‐to‐noise ratio for detecting deuterium Ly‐ radiation assuming a 30‐min observation in the CI's comet flyby, we verified that deuterium detection is feasible across a broad range of comets with the assumed parameter space. Furthermore, we confirmed that hydrogen atom density can be quantified with sufficient accuracy from Ly‐ radiance observations by employing a radiative transfer model. These findings demonstrate that, even under the severe constraints of ultra‐small satellites, optical measurement of cometary D/H ratios is feasible.

ABSTRACT The U-Pb method has become one of the most prominent approaches for dating geological events. A number of U-bearing minerals can be used, depending on the problem addressed and the type of geological material available, but zircon is the most useful and commonly analysed mineral. In many cases, this mineral provides high-precision dates for one or a sequence of stages in the evolution of a rock unit, including the timing of magmatic and metamorphic events. In detail, the information provided by the U-Pb method can be affected by a number of complicating factors, which can be difficult to detect for low-precision analyses, but become increasingly evident as the degree of precision increases. The most common effect observed is due to partial Pb loss that affects mostly old and U-rich domains of zircon due to alteration effects, diffusion or leaching. Loss of Pb also occurs when zircon undergoes metamorphic recrystallisation or resorption. Another type of complication arises when multiple growth generations are present in a population and/or in individual grains. Initial isotopic disequilibrium with excess 230Th or 231Pa, or loss of gaseous 222Rn, can all cause discordance. High precision geochronology can resolve multistage zircon growth during different stages of single magmatic cycles, with antecrysts first developed in magma chambers at depth and subsequent zircon domains or whole grains forming in the final stages of magma crystallisation, or just before eruption for volcanic rocks. One such example is reported for a volcanic rock from St. Mary’s Islands on the western coast of India, previously dated at 91.2 ± 0.2 Ma. Zircon grains from our new sample provide a classical U-Pb data array reflecting the presence of antecrysts besides zircon formed shortly before eruption. The array spans some 3 m.y., and the youngest date of 91.8 Ma is close to the published age.

ABSTRACT Meso-to-Neoproterozoic Chhattisgarh Supergroup unconformably overlies the Neoarchaean to Palaeoproterozoic granitoids and meta-sedimentary rocks of the Bastar Craton. The succession consists of two major unconformity-bounded sequences, the Chandarpur-Raipur and the Kharsiya. Striking differences in the thicknesses and sedimentation patterns of the two sequences have been observed from the eastern part of the basin transitions to the western part. The maximum thickness of these sequences in the east and west of the basin is ~ 2580 and 1800 m, respectively. The thickness of the Chandarpur Group is about 1100 m in the east and merely about 300 m in the west. The thick mudstone-dominated Gomarda Formation (630 m) of the east is completely missing in the west. Conglomerate and arkose occur widely in the east but not in the west. In contrast, carbonates and fine siliciclastics occur more extensively in the west, indicating variation in the depositional environment along an east-west direction. The petrographic study indicates that the major source in the eastern part is granite gneiss, whereas in the west, the source of sediments includes both granite gneiss and meta-sedimentary rocks. The REE patterns and Eu anomalies of the shale and sandstones from the Chhattisgarh Basin are similar and resemble the granite gneiss of the Bastar Craton. The provenance analysis using trace elements and Nd isotopic ratios corroborates that the spatially extensive ~2.5 Ga granite gneisses were the major contributors of the detritus. U-Pb SHRIMP ages of detrital zircons from Lohardih and Kansapathar formations, and Deodongar Member of the Chandi Formation yield unimod-al distributions (ca. 2470 and 2485 Ma), reflecting supply from the granitic basement. The successive N-S trending faults, poorly sorted conglomerate and sandstone along the basin margin, followed by matured quartz arenite and carbonate-shale deposit with variation in thicknesses of the different stratigraphic units of the eastern and the western parts of the basin, point to the half-graben model of the basin evolution.

ABSTRACT Gold mineralisation at Paramanahalli (Karnataka) is confined to altered metabasalt and Banded Iron Formation (BIF) of the Archean Hiriyur Formation. The addition and/ or depletion of major, trace elements, and the Rare Earth Element (REE) concentrations analysed in mineralised (altered) /non-mineralised (least altered) metabasalt and BIF. The rocks from the proximal alteration zone, such as altered metabasalt, display enrichment in SiO2 (attributed to silicification) and CaO (resulting from the formation of carbonate minerals), accompanied by a marked depletion in MgO due to alteration of mafic ferromagnesian minerals such as pyroxene and amphibole in the original metabasalt. The exchange between fluid and wall-rock contributes to mineral formation, such as chlorite (Fe-rich), quartz, rutile, ankerite, calcite, pyrite, and gold confirming the enrichment of CaO, FeO, K2O, TiO2, SiO2, S, and Au in altered rocks. The enrichment of gold (8-11 ppm) in metabasalt infers that it can be considered as a source and host rock. The study further explores alteration assemblage associated with chloritisation, sulphidation, and carbonatisation marked by the presence of chlorite, sulphides, and carbonate minerals, reflecting extensive fluid-rock interactions that contributed to gold mineralisation in the mineralised zones. The various types of alteration zones are spatially associated with major structural features, including shear zones and lithological contacts, which act as conduits for hydrothermal fluids. The geochemical signature of the Paramanahalli gold deposit, as reflected in the major, trace, and REEs from the mineralised zone, underscores the complex interplay of hydrothermal processes and fluid/rock reaction that led to gold mineralisation.

BACKGROUND: Diabetic kidney disease (DKD) represents a significant microvascular complication associated with type 2 diabetes mellitus (T2DM), markedly elevating the risk of kidney failure, cardiovascular events, and premature mortality. Despite advancements in therapeutic management, such as renin-angiotensin-aldosterone system (RAAS) blockade and sodium-glucose cotransporter 2 (SGLT2) inhibitors, residual risk remains significant. Finerenone, a novel nonsteroidal and selective mineralocorticoid receptor antagonist (MRA), has demonstrated substantial cardiorenal benefits in clinical trials; however, real-world data, especially from Saudi Arabia, remain limited. METHOD: This single-center, retrospective cohort study. All adult patients (≥18 years) who received finerenone as part of routine clinical care were eligible if they met either of the following criteria: (1) documented diabetic kidney disease (DKD) based on KDIGO-aligned clinical criteria, including diabetes mellitus with chronic kidney disease manifested by albuminuria/proteinuria and/or reduced eGFR; (2) and/or a urine protein-to-creatinine ratio (uPCR) >0.3 mg/mg. Longitudinal changes in uPCR, eGFR, and serum potassium were analyzed using linear mixed-effects models adjusted for relevant clinical covariates. RESULTS: A total of 75 patients prescribed finerenone were screened, of whom 67 met the inclusion criteria. The median age was 63 years, and 53.7% were female. Comorbidities were highly prevalent, including diabetes mellitus (89.6%), hypertension (97.0%), dyslipidemia (92.5%), heart failure (56.8%), and coronary artery disease (40.3%). A significant effect of time on uPCR was observed (F[3,193] = 3.457; P = 0.018), with a mean reduction of 0.464 mg/mg after six months (95% CI, -0.895 to -0.034; P = 0.027). The estimated eGFR slope after finerenone initiation was -1.08 mL/min/1.73 m² per month (95% CI -1.74 to -0.41; P = 0.002), corresponding to an annualized decline of approximately -12.9 mL/min/1.73 m² per year. Serum potassium increased modestly at early follow-up points (F[5,245] = 4.008; P = 0.002), rising by +0.209, + 0.256, and +0.286 mmol/L at the first three readings (P = 0.029, 0.005, and 0.006, respectively), then plateaued thereafter (P > 0.5). CONCLUSION: Finerenone use among DKD patients in Saudi Arabia was associated with significant reductions in proteinuria, an early decline in eGFR that requires cautious interpretation, and an overall favorable safety profile. These real-world findings align with results from pivotal clinical trials and support the incorporation of finerenone into standard DKD management. Future multicenter prospective studies are warranted to confirm these outcomes and evaluate long-term cardiorenal benefits.

Abstract The Lunar Trailblazer (LTB) spacecraft launched on 27 February 2025, toward a planned low‐lunar orbit. Eleven hours into its mission, contact with Trailblazer was lost, and recovery efforts began. Estimating the orientation and angular velocity state of Trailblazer was central for recovery to determine whether and when the vehicle could be contacted again. This work documents a method to estimate Trailblazer's attitude state using only ground‐based optical telescopes. This data is cheap to collect and scales favorably with distance compared to radar data. We rely on photometric light curves, time histories of Trailblazer's observed brightness. The process of estimating Trailblazer's orientation and angular velocity from this data is known as light curve inversion. Light curve attitude inversion, in addition to inherent ambiguities caused by symmetries in the observed object's geometry and the geometry of the observation, is sensitive to the object's assumed surface materials. In this paper, we study the impact of surface material accuracy using two light curves of Trailblazer acquired by the 4.2‐m aperture Lowell Discovery Telescope in Arizona on 10 March 2025 and the 8.1‐m aperture Gemini South observatory in Chile on 9 April 2025. We produce two sets of solutions for each light curve: one using material properties derived from a solar radiation pressure model of the LTB, and a second using materials fit to laboratory reflectometry of Trailblazer's materials. We qualitatively compare solutions for both cases and perform a sensitivity analysis to quantify the dependence between the attitude solutions and material property errors.