Devonian magmatism in the Eastern Sierras Pampeanas of Argentina is characterized by voluminous monzogranitic to granitic intrusions and associated mafic to intermediate rocks with sanukitoid affinity. These plutonic suites, emplaced in an intracontinental post-orogenic setting, define a coherent magmatic series. Geochemical data, supported by experimental petrology and fractional crystallization models, reveal a genetic link between mafic enclaves (sanukitoids) and the dominant felsic facies, depicting differentiation trends from sanukitoid parental melts. Trace-element systematics (e.g., Ba, Sr, Zr, REEs, F) and Sr-Nd isotopic compositions suggest that the primary magmas were derived from a lithospheric mantle source metasomatized by crust-derived components during earlier orogenic stages. The widespread occurrence and substantial volume of these granitoids, estimated at over 6000 km3, highlight their potential contribution to net continental crust growth. This study provides the first robust evidence of Phanerozoic post-collisional mantle-derived magmatism in South America. The Devonian batholiths of the Sierras Pampeanas thus represent a key example of juvenile crust generation far from active continental margins, involving partial melting of a lithospheric mantle source previously enriched during earlier orogenic stages. Melt generation and accumulation may have contributed to lithospheric weakening during regional post-orogenic extension.
The present study investigates the hydrogeochemical evolution of water resources in a complex mineral-rich landscape of central India. The region’s mine water and acid mine drainage (AMD), driven by the oxidation of sulfide-bearing minerals, contribute to highly acidic conditions that mobilize toxic metals. Groundwater shows exceedances of F⁻ (13%), NO3⁻ (16%), U (18%) and Mn (26%), while surface water records higher levels of F⁻ (30%), SO42⁻ (21%), K⁺ (17%), Ca2⁺ (4%) and NO3⁻ (4%); isotopic and statistical analyses (PCA, EPA-PMF model) indicate that groundwater chemistry is shaped by both geogenic and anthropogenic inputs. High uranium concentrations in groundwater, has been detected, analyzed, and interpreted, are attributed to the weathering of uranium-bearing minerals (uraninite, zircon, biotite), as confirmed by petrographic, XRD, and SEM–EDX analyses of granitic basement rocks. The saturation index and the positive correlation of U with bicarbonate and fluoride in groundwater suggests uranium mobility under alkaline, oxidizing conditions through the formation of stable uranyl–carbonate complexes. The relationship between δ18O, U, and F⁻ indicates differential mineral dissolution across varying lithologies driven by distinct geogenic processes. Groundwater exhibited acceptable carcinogenic risk (CR) (CR <10⁻4) for all age groups, whereas surface water exceeded the USEPA threshold (CR >10⁻4), indicating significant lifetime cancer risk. Pre-monsoon risks reached 39% for As and 4% for Cr (adult/child), while post-monsoon Cr (17–25%) and As (25%) predominated. These findings underscore the scope for uranium prospecting and improved water management to address public health concerns.
Integration of multidisciplinary geoscientific datasets is essential for delineating tectonic frameworks and understanding the evolutionary history of Precambrian shield regions. The Greater Indian Landmass represents a complex assembly of crustal blocks accreted and amalgamated during different stages of geological evolution. In this study, regional gravity data, integrated with geological and satellite magnetic constraints, are analysed to develop a revised tectonic framework, for the Peninsular Indian Shield and adjoining extra-peninsular shield regions.The results suggest that the conventional threefold subdivision of Peninsular India into North Indian Block, South Indian Block, and Marwar Block can be further refined by identification of two additional sub-blocks. The Bastar and Singhbhum cratons together with the western part of the Chhotanagpur Granite-Gneissic Complex, are interpreted as an Eastern Proto-Continent, distinct from the South Indian Block. Similarly, the western part of the North Indian Block beyond the Barmer–Cambay rift zone is identified as the Western Proto-Continent (Marwar Block). These crustal domains exhibit distinct gravity and magnetic anomaly signatures as revealed in the gravity-magnetic profiles across the Peninsular Indian Shield. Gravity modelling builds the variations in the crustal architecture across the Indian Shield. The crustal domains are separated by prominent gravity gradient zones. The marginal zones between these crustal blocks are interpreted as favourable loci for rift-related magmatism and associated mineralization.
Chemical evolution of seawater composition is thought to have exerted considerable influence on biological evolution throughout Earth’s history. However, the chemical structure and dynamics of the early ocean (>3.0 Ga) are poorly understood. Here, we experimentally studied trace metal (TM) scavenging by greenalite and Fe-(oxy)hydroxide minerals precipitated under simulated early Precambrian conditions, alongside in-situ TM compositions of magnetite and grunerite in 4.2 and 3.2 Ga banded iron formations (BIFs). Our geochemical experiments mimicking early Precambrian seawater conditions show that both primary greenalite and Fe-(oxy)hydroxide TM sinks influenced the overall concentrations of dissolved Ni, Co, and Zn in the early seawater column. Reconstructed TM values from BIF minerals using experimentally determined distribution coefficients indicate fluctuating Ni, Co and Zn levels in the ambient seawater. Our results suggest that processes like deep-water hydrothermalism, sequential greenalite and Fe-(oxy)hydroxides formation due to a vertical transportation delay of hydrothermal components to surface water, dilution of hydrothermal components, and a microbial physiological resuscitation lag likely regulated the abundance and distribution of TMs in the Hadean to early Archean seawater. Using the ratios of Ni/Zn or Co/Zn bound to greenalite and Fe-(oxy)hydroxides as a model, our data indicate quantitative removal of Zn—first by greenalite, followed by Fe-(oxy)hydroxide sinks. The resultant high Ni/Zn ratios in the Hadean to early Archean seawater column after each periodic Fe mineral formation cohere with the dependence of early marine biogenic methanogenesis on Ni enzymes and a low requirement for Zn enzymes by primordial life.
The eastern proto-Eurasian passive margin, currently around the southeastern Korean Peninsula, experienced complex tectonic episodes of paleo-Pacific plate subduction, mantle upwelling, plutonic intrusion, continental rifting, and rotational separation of continental fragments. These multi-stage processes imprint composite tectonic signatures in the crust and upper mantle. We construct a high-resolution, three-dimensional shear-wave velocity model extending into the upper mantle by integrating ambient-noise tomography and earthquake-based Eikonal tomography. The velocity structures reveal strong low-velocity anomalies in sediment-filled basins underlain by high-velocity plutonic bodies and substantial basement relief, indicating extensive arc-related magmatism and magma underplating in the Cretaceous. Low-velocity anomalies in the upper mantle along the western margin of the Gyeongsang basin suggest thermally modified lithosphere influenced by northwestward mantle-wedge flow linked to paleo-Pacific subduction. These characteristics together with subdued mountain topography near volcanic basins suggest lithospheric extension associated with slab retreat. Along the eastern and southern coasts, strong high-velocity anomalies in the lower crust reflect mantle uplift and lithospheric thinning related to continental rifting prior to the opening of the East Sea (Sea of Japan). Low velocity perturbations along the east coast at depths of ∼50–100 km suggest elevated thermal conditions produced by asthenospheric upwelling beneath the extensional margin. The spatially variable structures suggest continental rifting through multiple processes. Seismic anisotropy provides additional constraints on the deformation history, supporting clockwise rotational deformation around a pivot located near the southwestern East Sea.
