Crustal evolution and stabilization of the Arabian-Nubian Shield: Constraints from whole-rock Sr Nd and zircon U-Pb-Hf-O isotopes of bimodal volcanics

Precambrian crustal evolution of the southern margin of the North China Craton: Evidence from the Paleo–Mesoproterozoic sedimentary rock

Potassium isotopic evidence for the petrogenesis of Precambrian granitoids and implications for early crustal evolution of the accretionary orogen

Biological soil crusts (BSCs) are critical ecological components in arid lands. Their formation and stability hinge on the assembly and interactive networks of cyanobacteria-led bacterial communities. Yet, how different functional cyanobacteria shape the underlying microbial structure and assembly rules is poorly understood. Here, we cultivated artificial algal crusts using two representative cyanobacteria: the nitrogen-fixing Leptolyngbya sp. and the non-nitrogen-fixing Microcoleus vaginatus (M. vaginatus CM01). A total of six treatments were established based on the presence or absence of spraying with in situ BSCs leachate: a control group without inoculation of algae or bacteria (soil, S); a treatment group sprayed only with bacterial suspension (soil + bacteria, SB); a treatment group sprayed only with M. vaginatus CM01 (soil + M. vaginatus CM01, SM); a treatment group co-inoculated with both BSCs leachate and M. vaginatus CM01 (soil + M. vaginatus CM01 + bacteria, SMB); a treatment group inoculated only with Leptolyngbya sp. CT01 (soil + Leptolyngbya sp. CT01, SL); and a treatment group co-inoculated with Leptolyngbya sp. CT01 and biocrust leachate (soil + Leptolyngbya sp. CT01 + bacteria, SLB). By integrating 16S rRNA gene sequencing, neutral community modeling (NCM), and structural equation modeling (SEM), we dissected differences in Cyano-BSCs development, bacterial community composition, co-occurrence networks, and assembly mechanisms. Inoculation with M. vaginatus CM01 (SM, SMB) superiorly promoted Cyano-BSCs development: the SM group achieved the highest coverage (23.33%), while the SMB group showed marked increases in organic matter (OM, 4.10 g·kg−1) and chlorophyll a (Chla, 13.40 μg·g−1), alongside a >5-fold rise in bacterial, cyanobacterial, and nitrogen-fixation gene abundances versus controls. The mechanism centers on extracellular polymeric substances (EPS) secreted by M. vaginatus, which homogenized the microenvironment, suppressed stochastic bacterial dispersal (NCM, SM: R2 = 0.698), and enhanced deterministic selection. This process forged a highly cooperative network (89.74% positive links, average degree 34.71) that directionally enriched Cyanobacteria (relative abundance 40.40%). The Shannon index of Cyano-BSCs from the group (SMB) reached 7.72 ± 0.09, reflecting high microbial community diversity. SEM confirmed M. vaginatus directly regulated bacterial assembly (path coefficient = 0.59, p < 0.05) and indirectly improved the soil environment (path coefficient = 0.64, p < 0.05), establishing a “cyanobacteria-community-environment” feedback loop. Conversely, the Leptolyngbya sp. groups (SL, SLB), despite enriching nitrogen-fixing bacteria and fungi, exhibited low carbon fixation efficiency (notably 1.26 g·kg−1 OM in SL) and lack of EPS; communities remained stochastic (NCM, SL: R2 = 0.751) with no effective regulatory pathway—a pattern mirrored in S and SB groups. Our findings demonstrate that M. vaginatus acts as a core engineer of biological soil Cyano-BSCs formation via an “EPS-mediated habitat filtering—functional group enrichment—cooperative network assembly” cascade, enforcing deterministic community construction. Leptolyngbya sp., with limited niche-constructing ability, fails to exert comparable control. This work provides a targeted framework for the artificial restoration of Cyano-BSCs in arid zones.

Abstract Geochemical studies of shergottites have predicted an enriched end member associated with the final residual liquid of the Martian magma ocean, which may result in the formation of a KREEP-like silica-rich primitive crust on early Mars. In this work, we investigate the evolution of the Martian crust using the 1D parameterized mantle convection model. By combining various observational and geophysical constraints, our model supports the KREEP-like silica-rich primitive crust that formed before 4.527 Ga, i.e., the time for the formation of the earliest basaltic secondary crust associated with the early mantle overturn, whose thickness would be at least 3–8 km. During the consequential evolution, the silica-rich primitive crust on the northern hemisphere would have been removed by the Borealis impact. However, the silica-rich primitive crust of the southern hemisphere would still survive and would be buried below the ejecta of the Borealis impact and local basaltic secondary crust, which may correspond to the low-density layer below the southern highland of Mars suggested by gravitational observations.

ABSTRACT Delhi has been a culturally rich city since ancient times, and hosts numerous heritage buildings, several of which are inscribed on the UNESCO World Heritage List. As one of the most polluted hotspots, the megacity presents elevated risks of pollutant-driven stone alteration. In this study, Humayun’s Tomb is analyzed for the pollutant-driven decay processes by characterizing the rooftop black crust (BC) formed under varying exposure conditions. A multi-analytical protocol, including XRF, XRD, FTIR, SEM-EDX, CHNS analyzer, and ICP-MS, was adopted. Outcomes consistent with the dominance of pollution-induced sulfur and calcium led to the formation of the BC matrix along with the carbonaceous framework. Gypsum was most abundant at the more wind-exposed, rain-sheltered rooftop locations and comparatively weaker at more protected areas, revealing a clear exposure and orientation related gradient in crust development. Trace-element profiles further suggest regional air pollution markers, consistent with Delhi’s major emission sources, including vehicular traffic, road/soil dust, construction dust, biomass burning, and industrial activities. As the first integrated analytical investigation at Humayun’s Tomb, this study provides a multi-analytical evidence base to inform preventive conservation strategies and the prioritization of cleaning and monitoring actions at this site and at comparable monuments in similarly polluted urban environments.

ABSTRACT Numerous earthen heritage sites with high historical, scientific, and cultural value are widely distributed across northwestern China. Under repeated freeze–thaw cycles, the earthen heritage sites undergo severe deterioration, including sheet-like spalling, crack propagation, basal undercutting, and partial collapse, among which sheet-like spalling is the most typical and destructive failure mode. In this study, laboratory tests on earthen specimens were conducted under controlled freeze–thaw cycles. By combining three-dimensional laser scanning with depth-of-field digital microscopy, the formation and evolution of sheet-like spalling were continuously tracked and documented. Concurrently, multiple indicators were monitored, including the spatiotemporal migration of moisture, the redistribution of soluble salts, the evolution of specific surface area and mean pore size, and the attenuation of elastic wave velocity. The results indicate that sheet-like spalling can be generalized into a four-stage progressive sequence of “powdering – agglomeration – crusting – spalling.” During this process, the coupled water–salt system persistently migrates from the interior towards the surface, leading to continuous enrichment of salts and the development of a high-salinity surface hard crust. This is accompanied by a microstructural transition from particle disintegration and refinement to salt-cemented aggregation and interfacial deterioration at the crust – substrate boundary.

The North China Craton (NCC), one of the oldest cratons worldwide, may provide information on the evolution and geodynamic processes of the early Earth, especially during the pre-Mesoarchean period. Many ancient zircons have been discovered in the Jiapigou terrane of the northeastern NCC on the basis of our recent studies, providing an excellent opportunity to trace the early crustal evolution trend of the NCC. Here, we present a detailed study of the petrography, mineralogy, zircon U–Pb dating and Lu–Hf isotopes of supracrustal rocks (biotite schist) obtained from the Jiapigou terrane. Geochronology combined with the internal structures and Th/U ratios of the zircons reveal that the zircons acquired from the supracrustal rock can be divided into the following two types: magmatic zircons and metamorphic zircons. Among the magmatic zircons, the youngest zircon age (2.49 Ga) is considered to represent the time at which the protolith of the supracrustal rock (i.e., Neoarchean) crystallized, whereas the others were likely captured or inherited from their magma sources. The zircon Hf isotopes reveal that unexposed Hadean–Paleoarchean crust (4.18–3.57 Ga) is present beneath the Jiapigou terrane, and its growth history can be traced back to the Hadean period. Moreover, the evidence derived from this and previous studies indicates that the Jiapigou terrane underwent two crustal recycling events (3.37–3.20 Ga and ~2.96 Ga) during the Paleoarchean, two crustal reworking episodes (2.53 Ga and 2.49 Ga) during the Neoarchean, and later metamorphism at 2.41 Ga. Thus, the Jiapigou terrane has undoubtedly recorded multiple episodes of early crustal growth and/or reworking that are similar to, but not limited to, those of the northern and southern margins of the NCC.

The mineralogical and geochemical composition of cave sediments provides crucial insights into past climatic and biological dynamics. This study investigates the authigenic crusts of San Teodoro Cave (Sicily), a key Upper Pleistocene palaeontological site, through a multi-analytical approach.The cave hosts two superimposed phosphatic crusts, separated by sterile sediment, reflecting shifts in depositional and post-depositional conditions. Our analyses reveal a complex mineral assemblage consisting of calcite, aragonite, and various phosphate phases. Calcite is the dominant phase in the older crust, whereas the presence of aragonite in the younger brown crust likely indicates periods of increased aridity, potentially corresponding to conditions during the Last Glacial Maximum. Aragonite precipitation was favoured by elevated Mg/Ca ratios, limited water infiltration, and kinetically controlled processes. Phosphate minerals, derived from bat guano, record localised pH variations and biologically mediated geochemical activity. The development of stable crusts without evidence of bioturbation further suggests the cessation of hyena activity within the cave. These findings demonstrate that the aragonite-phosphate association is a probable indicator of extreme dryness and specific taphonomic pathways in Mediterranean Pleistocene cave environments, offering a high-resolution proxy for paleoenvironmental reconstruction during the driest phases of the Late Pleistocene.

Summary Located at the easternmost passive margin of the Eurasian Plate, the southeastern Korean Peninsula shows geological signatures consistent with Miocene backarc opening associated with the Pacific Plate subduction. The region comprises two contrasting crustal blocks—the Early Cretaceous Gyeongsang Basin and Miocene Yeonil Basin (YB)—and hosts multiple fault systems that record both extensional and contractional deformation, providing an ideal setting to investigate crustal evolution along a passive margin. Motivated by this complex setting, we performed high-resolution P-receiver function imaging using a dense broadband seismic network. Our results reveal two Moho offsets: a western offset from 33 to 28 km, and an eastern offset from 28 to 26 km, coinciding with major fault zones and likely reflecting localized crustal thinning and subsequent reactivation. Crustal anisotropy, inferred from changes in fast-axis orientations, varies spatially, with Miocene fossil anisotropy in the GB and both fossil and present-day stress-induced anisotropy in the YB. Variations in P-to-S velocity ratio (VP/VS) reflect compositional heterogeneity and fault-related fracturing. Large earthquakes (M ≥ 4) occurred in low-VP/VS zones associated with relatively rigid and possibly locked crustal segments, while high-VP/VS regions coincide with zones of crustal weakening and microseismicity. Our findings suggest that extension-related deformation and inherited structural heterogeneity are preserved within the crust of this fossil backarc system, linking past tectonic processes to present-day structure and seismicity.

ABSTRACT This study evaluated the influence of roasting conditions on the physical and chemical changes in pork loin, with emphasis on the relationship between color development, crust formation, and heat and mass transfer under controlled oven conditions. Uniform heat transfer allowed precise monitoring of temperature profiles, moisture loss, color parameters ( L* , a* , b* , browning index, Δ E* ), and crust thickness. Indicators of lipid oxidation, protein oxidation, and Maillard reaction progression were also assessed as a function of roasting temperature. Increasing process temperature reduced crust moisture, promoting crust thickening and surface darkening. Color evolution correlated with crust temperature, evidencing melanoidin formation alongside lipid and protein oxidation. Fourier transform infrared spectra of the crust and UV–visible analysis of extracted pigments confirmed the presence of browning compounds, with characteristic absorption bands indicating protein aggregation and advanced Maillard reaction products. This study accurately described the relationship between color, temperature, and moisture in the crust, highlighting the importance of roasting conditions in browning compound formation. These findings contribute to a better understanding of the mechanisms underlying surface browning and crust development in meat products. The results provide valuable insights for optimizing cooking and industrial roasting processes, enabling more accurate prediction and control of color evolution and crust properties. Applying the developed mathematical models can support technological advances in oven cavity design and process automation, improving roasting efficiency, ensuring consistent product quality, and minimizing the formation of undesirable compounds. Overall, this research offers practical strategies to enhance the technological, sensory, and safety attributes of roasted meat products.

ABSTRACT Phanerozoic magmatism in the northern Andes records a complex history of plate convergence, subduction dynamics and lithospheric inheritance along the northwestern margin of South America. This special issue synthesizes recent multidisciplinary advances that address the temporal, spatial and geodynamic evolution of Andean magmatism in Colombia and Ecuador, integrating petrographic, geochemical, geochronological, structural and geophysical perspectives. The contributions compiled herein provide new constraints on key stages of Andean development, including the construction and migration of Jurassic magmatic arcs, the formation and inversion of Cretaceous marginal and back-arc basins, and the Neogene reorganization of the convergent margin associated with changes in subduction geometry and slab segmentation. Several studies highlight the progressive transition from mantle-dominated to crustally influenced magmatic systems, the role of syn-tectonic pluton emplacement, and the links between deep crustal processes and surface magmatism. Other contributions emphasize the long-term influence of Precambrian lithospheric architecture on Phanerozoic crustal evolution, underscoring the importance of inherited structures in controlling Andean deformation and magmatic patterns. Collectively, the papers in this volume demonstrate that the tectono-magmatic evolution of the northern Andes is best explained by the interplay between variable subduction regimes, arc migration and segmentation, terrane accretion, and crust – mantle interactions through time. This synthesis provides a framework for improved palaeogeographic reconstructions of northwestern South America and highlights outstanding questions that will guide future research on Andean orogenic processes.

Abstract The Álamo Complex, part of the Galician–Castilian Lineament within the Central Iberian Zone, lies between the Ollo de Sapo Domain and the Schist–Greywacke Complex. It comprises six tectonometamorphic sectors dominated by psammitic–pelitic metasediments (MTS), gneisses, migmatites, leucogranites and tourmaline-rich rocks. Zircon U–Pb dating identifies three Ediacaran partial melting events (∼628, 584 and 549 Ma) that occurred under high-pressure conditions within the kyanite stability field. These contrast with a low-pressure Variscan partial melting episode (∼310–315 Ma). Orthogneisses and leucogranites dated at ∼482–465 Ma record Cambro–Ordovician magmatism, characterized by abundant inherited Ediacaran zircon cores, indicating significant crustal recycling. Petrographic and geochemical similarities, together with shared zircon inheritance patterns, link the Álamo Complex with the Ollo de Sapo Domain and other segments of the Galician–Castilian Lineament, suggesting a common magmatic evolution. Tourmaline-rich rocks likely formed by boron metasomatism initiated during the Ediacaran and enhanced by recurrent partial melting. Variscan magmatism is represented by intrusive mafic and granitic bodies (∼307–311 Ma) and tourmaline-bearing leucogranites, reflecting continued reworking of Ediacaran crust into the Late Palaeozoic. These results shed light on the crustal evolution of Central Iberia.

The Wadi Khashab area in the southern Nubian Shield of Egypt records the transition from subduction-related to post-collisional magmatism, representing a major phase in the evolution of the Arabian-Nubian Shield. Understanding the geochemistry of uranium (U) and thorium (Th) is crucial for tracking magmatic and post-magmatic processes, as these radioactive elements provide valuable insights into crustal evolution. This study integrates field observations, petrography, whole-rock geochemistry, and gamma-ray spectrometric analyses of U and Th to clarify the petrogenesis and geodynamic setting of the granitic rocks. Two distinct magmatic pulses were identified: an older calc-alkaline suite (quartz diorite, tonalite, granodiorite) with low high-field-strength elements (HFSE: Nb = 8-20 ppm, Zr ∼200 ppm) and I-type characteristics, formed in a volcanic arc; and a younger suite of A-type biotite granites and altered varieties (albitized and greisenized), characterized by high SiO 2 and enrichment in incompatible elements. Geochemical modeling suggests that the older suite originated from the hybridization of mantle-derived melts with mafic lower crust, while the younger suite was derived from partial melting of the crust. U-Th geochemistry indicates that magmatic fractionation was overprinted by hydrothermal fluids, leading to significant uranium enrichment in the altered granites, with average contents of 16.2 ppm in albitized and 13.6 ppm in greisenized varieties. These altered granites are classified as uraniferous, with U and Th mainly hosted in resistant accessory minerals. This study links U-Th mobility to specific post-emplacement alteration events, providing new insights into post-accretionary fluid-driven processes in the Nubian Shield and highlighting the area's potential for uranium mineralization.

Soil salinization has emerged as a major constraint to global agricultural productivity, severely disrupting soil structure, nutrient cycling, and plant establishment. This study evaluates the functional potential of the cyanobacterium Desertifilum salkalinema SSAU-7 and the microalga Chlorella vulgaris SSAU-8 as bio-ameliorants for saline soils. Both isolates demonstrated high salinity tolerance and exhibited key plant growth-promoting traits, including indole-3-acetic acid (IAA) and hydrogen cyanide (HCN) production. Under escalating salt concentrations, D. salkalinema SSAU-7 and the mixed consortium maintained stable photosynthetic activity and enhanced extracellular polymeric substance (EPS) secretion, while C. vulgaris SSAU-8 showed reduced photo-physiological performance at 10g L⁻¹ salinity. Soil microcosm experiments revealed that microbial inoculation facilitated the development of biological soil crusts (BSCs), which significantly improved soil physicochemical properties over 75 days. Notably, treated soils exhibited reduced pH (7.5-8.0), a 209% increase in total organic carbon, a 10% enhancement in porosity, and an 8% reduction in bulk density. EPS emerged as a critical driver of soil aggregation and fertility restoration by integrating essential structural components within the saline matrix. The BSC-amended soils further promoted Oryza sativa germination and early seedling vigor, underscoring the agricultural relevance of these microbial consortia. Collectively, our findings establish cyanobacteria-microalgae co-cultures as a promising eco-engineering strategy for reclaiming saline landscapes and strengthening soil resilience under salt stress.

Abstract The formation of juvenile felsic crust in intra-oceanic arcs (IOAs) represents a fundamental but poorly understood process in Earth's crustal evolution. While Archean tonalite-trondhjemite-granodiorite (TTG) suites have been extensively studied, the mechanisms driving post-Archean crustal growth in IOAs, particularly in the absence of pre-existing continental material, remain unclear. The Luzon Granitoid Complex (LGC) in the Central Cordillera of Northern Luzon, Philippines, offers valuable insights into juvenile crustal growth within a late Eocene (34–36 Ma) intra-oceanic arc system. Integrated analysis of U–Pb zircon geochronology, Hf isotopes, whole-rock geochemistry, and petrography classifies the LGC as low-pressure intra-oceanic arc granitoids (LP-IOAGs), comprising tonalites and trondhjemites with calc-alkaline compositions and primitive oceanic arc signatures. These LP-IOAGs exhibit diagnostic low-pressure characteristics (Sr/Y < 20, La/Yb < 10, flat HREEs), indicating plagioclase-dominated fractionation in a relatively thin arc crust without garnet involvement. Our results reveal two distinct petrogenetic signatures: (1) partial melting of gabbroic-amphibolitic lower crust (LREE-enriched Group 2: LaN/YbN > 2) and (2) fractional crystallization of mafic magmas (flat REE Group 1: LaN/YbN < 2). This heterogeneity in formation mechanisms, occurring simultaneously within the same arc segment, challenges conventional evolution models that ascribe specific processes to discrete spatial or temporal stages. Furthermore, zircons from the LGC exhibit consistently depleted mantle-like εHf(t) values (+ 13 to + 15), confirming derivation from purely juvenile sources without crustal recycling. These results show that low-pressure intra-oceanic arc granitoids (LP-IOAGs) can produce continental crust-like signatures via chemically distinct, yet coeval magmatic processes, independent of ancient crustal contributions. This advances our understanding of post-Archean crustal growth mechanisms.

Early Cretaceous adakitic rocks are widespread along the Tan-Lu Fault and the Dabie Orogen in eastern China. Conventional models attribute their origin to partial melting of thickened lower crust, associated with lithospheric thinning in the North China Craton. Our study presents comprehensive geochemistry for low-Mg adakitic rocks (LMAs) from the Southern Tan-Lu Fault Zone (STLFZ), and compares them with those from the Dabie Orogen. The STLFZ LMAs share similar Sr-Nd-Hf isotopic signatures with the Dabie LMAs, suggesting a shared source derived from the Paleoproterozoic basement of the northern Yangtze Block. However, the STLFZ LMAs are geochemically distinct, with lower La/Yb, Sr/CaO, and Nb/Ta ratios, but higher Nb/La ratios, reflecting differences in residual mineral assemblages and melting conditions. Phase equilibrium modeling reveals that the STLFZ LMAs likely formed through fluid-fluxed melting under garnet amphibolite facies, contrasting with the eclogite-facies dehydration melting for the Dabie LMAs. This implies that the STLFZ was not significantly thickened at the time of melting. Furthermore, the STLFZ LMAs were emplaced at ca. 130−115 Ma, later than the Dabie LMAs (ca. 143−130 Ma). These spatial, temporal, and genetic differences probably reflect the reactivation of the Tan-Lu Fault (ca. 146−130 Ma), which triggered dehydration melting, crustal foundering, and mantle metasomatism in the Dabie Orogen. Subsequent underplating of hydrous magmas beneath the STLFZ then facilitated fluid-fluxed melting under normal crustal thickness conditions. These findings provide new insights into the heterogeneous mechanisms of adakitic magmatism and the role of major tectonic structures in controlling crustal evolution.

Linear magnetic anomalies (LMAs) in marine settings provide important clues about formation and evolution of the oceanic crust. LMA interpretation can be challenging as it relies on visual inspection of spatial patterns of magnetic anomalies, which may not be well defined due to sparse and irregular ship tracks. Interpreting such magnetic anomalies based on human perception is inherently subjective as well as time-consuming. We aim to minimize subjectivity and speed up the interpretation by using deep learning (DL). Two significant challenges arise when applying DL to marine magnetic anomalies. First, the anomalies may exhibit discontinuities due to sparse and highly irregular tracklines. Second, the quantity of labeled marine magnetic data maps is very limited. For the first challenge, we employed anisotropic diffusion to smooth LMA along the local orientations, thereby enhancing the continuity. For the second challenge, we investigated deep transfer learning. We implemented three different DL models, namely, standard convolutional neural network (CNN), transfer learning without anisotropic diffusion and with it. When applied to a test dataset consisting of magnetic anomalies from East Pacific Rise and Reykjanes, CNN without transfer learning achieved moderate accuracy. With transfer learning, the prediction accuracy improved substantially. When anisotropically diffused marine magnetic anomalies were used as input, the prediction accuracy reached an even higher level. We applied our best-performing deep learning model—transfer learning combined with anisotropic diffusion—to marine magnetic anomalies from the Shatsky Rise region in the western Pacific and the Azores Plateau region in the northern Atlantic. Predictions at both areas exhibit LMAs resulting from spreading ridge volcanism. Some of the nonlinear predictions are due to poor data coverage, while others are correlated with complex tectonics such as tectonic reorganization, fracture zones, faults, etc.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-30926-1.

Abstract The collision of continents typically leads to orogenesis as a result of crustal thickening and isostatic compensation. High topography is a main locus of precipitation‐fueled erosion, providing a feedback‐loop between tectonics, surface processes, and climate. This feedback raises the question whether erosion or the strength of the colliding plates limits mountain growth on Earth. Here, we explore the interaction between surface processes and tectonics using numerical thermo‐mechanical‐surface‐processes models motivated by the new non‐dimensional Beaumont number . We first derive and discuss the number for collisional orogens growing primarily by crustal thickening and decoupled evolution of crust and mantle, and subject to fluvial erosion. Second, we explore the parameter space of using numerical models, leading to a refined ‐plot determining orogen Type, and showing that holds for a wide range of initial and boundary conditions as observed on Earth. Third, we show (a) that coupling between crust and mantle inhibits crustal thickening, (b) that orogens can move between Types through a change of a key parameter determining , and (c) that the height of strength limited orogens is set by the strength of the weakest orogen foreland, which also influences the distribution of shortening. Finally, we discuss how applies to different mountain belt types on Earth and whether there is a common pattern in how changes over the lifetime of an orogen.

Neoarchean crustal evolution in the Madras Block: Geochemical and petrological evidence from felsic gneiss and amphibolite