The contribution of continental volcanic arcs to global weathering fluxes: Insights from the Southern Andes

Tectonic modulation of caldera volcanism on the South Aegean Volcanic Arc

Abstract The low dimensionality of basalt geochemical data has long been inferred but has not been quantitatively evaluated from the relationships among elemental contents. We developed regression‐based machine learning models and examined the relationships among elemental contents for basalts. We applied an extended gradient boosting algorithm (natural gradient boosting), which allows predictions with associated probability distributions, to a training data set of global basalt compositions, including midocean ridge, ocean island, and volcanic arc basalts. From four input elements (Th, Nb, Zr, and Ti), the trained models can successfully predict the contents of 12 trace elements (Rb, Ba, U, La, Ce, Pb, Sr, P, Nd, Y, Yb, and Lu; R 2 > 0.7) and 5 major elements (SiO 2 , MgO, Na 2 O, CaO, and K 2 O; R 2 > 0.67). The adopted model interpretation techniques quantitatively identified key input features for output element estimations, such as similar elemental incompatibility (e.g., Th‐Rb contents) and elemental ratios/products involving different incompatible elements (e.g., Zr/Th ratios for Yb contents). This is consistent with well‐established geochemical principles related to elemental incompatibility and tectonic setting and was achieved without prior geochemical knowledge of the samples. On a projection of a reduced two‐dimensional map constructed from the four input elements, numerical variations of the identified key input features were correlated with the output contents. Given the successfully constructed regression‐based models based on only four input elements, basalt geochemical data have a low dimensionality. Moreover, our approach can potentially provide a more comprehensive understanding of the link between basalt geochemistry and geological processes.

Columns SiO2 through A/CNK of Table 3 contained incorrect values. See the PDF file for the corrected table.

The volcanic island complex of Milos, situated ~200 km north of the Hellenic subduction zone, records the interplay of volcanic, tectonic, and gravitational processes within multidirectional, polyphased rift systems that developed throughout the Mio–Plio–Quaternary. Its active and seismogenic fault network hosts both perennial and transient hydrothermal venting zones, offering a natural laboratory to examine fluid circulation within a volcanic arc built on stretched continental crust. This study refines the relationships between magmatism, seismicity, and hydrothermal activity, with implications for local geological hazards. Two new morpho-tectonic sketches are presented. The first places the Milos volcanic center within the structural framework of the Aegean microplate; the second illustrates the spatial organization of the Milos tectono-hydrothermal-volcanic system. These reconstructions integrate detailed physiographic analyses (relief, slope), field observations, and multidisciplinary datasets on seismicity, hydrothermalism, and mineralization. At the scale of the Aegean microplate, (i) NE–SW faults are attributed to extensional deformation along the Mid-Cycladic Lineament; (ii) E–W faults relate to the opening of the Milos, Cretan, and Christiana basins, parallel to the mid-Miocene West Cycladic Detachments; (iii) NW–SE faults correspond to the Myrtoon Basin and Gulf of Milos openings, the latter being closed to the south by the Fyriplaka volcano; and (iv) N–S faults controlling the Zephyria graben and the eastern margin of Milos are continuous with Cretan fault systems and are parallel both to the Eocene trans-Cycladic thrust in the region and to magnetic anomalies in the subducted Tethyan oceanic crust south of the Hellenic subduction zone. At the archipelago scale, seismicity, hydrothermal venting, alteration zones, and phreatic explosions are concentrated in the hanging wall of the Achivadolimni fault, along or near the intersections of the N–S Zephyria and NW–SE Fyriplaka grabens, directly above the inferred magma chamber. Microearthquake hypocentres, likely linked to fluid-induced fault dilation, occur beneath the Gulf of Milos (~7 km) and Fyriplaka volcano (~5 km). Their distribution suggests a genetic link between the intersecting grabens, cooling of isotherms beneath the gulf by descending seawater, surface hydrothermal manifestations, and tectonic earthquakes (e.g. Mw 5.3 Milos, 1992). A shallow hydrothermal convection loop (<3 km) probably overlies a magmatic reservoir where fluids accumulate beneath a self-sealed, low-permeability cap, possibly corresponding to a thermal brittle-ductile transition (370–450 °C). Co-seismic ruptures may locally breach this barrier, inducing “arterial fault” behaviour along the Achivadolimni fault. Pulsating hydrothermal activity and historical phreatic eruptions are interpreted as surface expressions of transient injections of over-pressurized magmatic fluids, leading to decompression, phase transitions, and fluid expulsion during seismic events. These coupled magmatic-hydrothermal-tectonic processes should be integrated into future hazard assessments for Milos.

The Highland Border Complex (HBC; e.g. River North Esk, Stonehaven) is here interpreted as part of a Cambrian – Early Ordovician hyperextended continent-ocean transition zone that was tectonically emplaced onto the S Laurentian margin related to Early Ordovician collision with a volcanic arc to the SE (Midland Valley). All HBC units include terrigenous sediment. Volcanics range from alkaline OIB, to variably enriched (North Esk), to MORB (Stonehaven). They include radiolarian chert and hydrothermal metalliferous deposits. A local conglomerate with locally stretched clasts (North Esk) includes chert and ultramafic detritus (with chromite). During and after emplacement, cross-cutting high-strain zones developed in response to progressive left-lateral/oblique ductile syn-metamorphic to brittle post-metamorphic stresses. Three main collision-related deformation events affected both the HBC and the adjacent Dalradian (North Esk), the first two under greenschist facies metamorphic conditions. Following peak metamorphism, the HBC and Dalradian in the Highland Border rotated to near vertical (Downbend). After exhumation via orogenic collapse and/or erosion, the Lower Old Red Sandstone (LORS) transgressed the Highland Border. In the North Esk, the basal LORS (Devonian Lintrathen ignimbrite) unconformably overlies the HBC, precluding this contact as the Highland Boundary Fault. The North Esk Fault and Highland Boundary Fault (Stonehaven) can be broadly correlated as a long-lived crustal discontinuity.

The Middle Permian was characterized by a major climatic warming trend that heralded the end of the late Paleozoic Ice Age, as well as by widespread marine anoxia during the Capitanian biotic crisis. Although the Emeishan large igneous province (ELIP) has been implicated as a potential driver of this warming, its role remains contentious. We present a comprehensive analysis of mercury abundance and isotopes, along with zircon geochemistry, from tuffs interbedded in a Middle Permian deep-water succession from South China. Our data reveal sustained continental arc volcanism (CAV) prior to the ELIP eruptions that coincided with the Middle Permian warming, suggesting a potential causal relationship between them. Supported by Carbon-Oxygen-Phosphorus-Sulfur-Evolution modeling, we propose that globally increased CAV may have released sufficiently large quantities of CO2 to the atmosphere to trigger climate warming, ultimately leading to marine anoxia and biotic crisis. Our findings challenge the prevailing view of the ELIP as the sole cause of the Middle Permian warming and highlight the potential importance of CAV in Earth’s climate history.

The Santorini volcano in the South Aegean Volcanic Arc is of great scientific importance. Knowledge of historical eruptions is valuable for better understanding the volcanic cycle and for improved hazard assessments. One of the little-known historical eruptions occurred either in 1570 or in 1573 or from 1570 to 1573 CE. We bring to light a very little-known but reliable Greek manuscript dated in 1588 CE which improves our knowledge about this eruption. The manuscript documents that the eruption occurred in 1572 and took place within the sea caldera between Santorini and Palaia Kameni. It makes it clear that “fire, smoke, and stones” were coming out between the two islands and a new volcanic island named Mikri Kameni was born. This landscape has been verified by independent maps of the 17th and 18th centuries. The floating pumice was transported by the sea as far as to Thessaloniki and Constantinople. Also, we learn a lot about the consequences of the eruption: (1) smoke and heat destroyed the vineyards and the planting season on Santorini, i.e., spring–summer, (2) it is likely that sulfurous gases were released, and (3) the residents of Santorini were forced to move to nearby islands. The duration of the eruption was ~1 year, but the fire and smoke disappeared suddenly. The Volcanic Explosivity Index of the eruption was estimated to be as high as 3.

Northeast Asia is a complex tectonic collage bounded by Paleozoic–Mesozoic internal and peripheral orogens, whose distribution and continuity are obscured by later deformation and magmatic overprinting. Here we present zircon data from granites and xenoliths in the Yeongdeok area, southeastern Korea, which suggest the presence of a long-lived (ca. 30 Myr) late Paleozoic volcanic arc system. Zircon cores yield U–Pb ages of 278–255 Ma, while rim ages cluster around 250 Ma, corresponding to the emplacement of the Yeongdeok adakite pluton and associated hydrothermal alteration. The 18O depletion (δ1⁸O = 4.7–0.6‰) observed in many zircons, along with core-to-rim decreases, is interpreted as the result of recycling of hydrothermally altered volcanic carapace material. Negative zircon εHf(t) values commonly observed in the xenolith-hosted zircons contrast with the consistently positive values of the host Yeongdeok pluton. These unradiogenic Hf signatures resemble those of detrital zircons from the Pyeongan Supergroup, deposited in an arc-related foreland basin. Our findings suggest a protracted late Paleozoic volcanic arc system—now largely eroded except for its plutonic roots—and, when integrated with data from the northern North China Block and Hida Belt of southwest Japan, provide new constraints on the configuration of the Central Asian Orogenic Belt.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-21691-2.

Abstract Precise position and geometry of the subducted slab are crucial for deciphering subduction zone volcanism. This is particularly important in the southern Costa Rican subduction zone, where the Cocos Ridge subducted at ∼2–3 Ma, coincident with the uplift of the Talamanca Range but later than the arc volcanism cessation (∼5–8 Ma). Here, we apply a refined Dip Direction Searching method to teleseismic receiver function waveforms from 17 broadband stations in this region. A northeast‐dipping interface is imaged deep to ∼110 and ∼60 km in the northwest and southeast of the subduction zone, respectively, interpreted as the Moho of the Cocos slab that has possibly undergone tearing. A flat interface is identified at ∼40–60 km depth exclusively beneath the Talamanca Range, which is most likely the Moho of the Nazca plate that has stagnated there since ∼8 Ma, blocking melt upwelling and consequently stopping the arc volcanism.

Nutrient availability and rising oxygen levels are important for the Cambrian Explosion (~540–515 Ma), both of which can be satisfied via enhanced weathering driven by climate and tectonics. Although increased subduction and continental arc volcanism coincided with the Cambrian Explosion, their weathering-nutrient feedback role remained unclear. Here we integrate Li-Os isotopes with previously published Sr isotope to investigate connections between subduction-driven weathering dynamics and animal diversification. Our results reveal a shift from enhanced erosion of arc-related juvenile rocks (ca. 540–525 Ma) to clay-forming weathering of old crust (525–515 Ma). We propose that subduction-driven warming and uplift may have accelerated erosion of phosphorus-rich juvenile rocks, releasing nutrients that boosted marine productivity and subsequent oxygen buildup through organic burial. This process ultimately fueled early animal diversification, providing additional evidence for tectonic control of biogeochemical cycles during the Cambrian Explosion.

The South Aegean Sea hosts two ENE–WSW rift zones with sedimentary basins of 500–700 m depth: the Christiana–Santorini–Kolumbo–Amorgos (CSKA) and the Astypalaea–Nisyros–Kos (ANK) zones. These form discontinuous graben structures with sediment thicknesses of 600–700 m from the Late Pliocene to Quaternary. Both rift zones comprise active volcanic centres: Santorini–Kolumbo in the CSKA and Nisyros in the ANK. Segmented by transverse NW–SE fault lines, these zones produce 25–40 km fault blocks, limiting maximum earthquake sizes per segment. High seismic activity includes the 7.4 magnitude 1956 Amorgos earthquake in the CSKA and several ∼6.5 events near Kos in the ANK (1933, 2017). Volcanic activity is stronger in the southwestern CSKA, with eruptions in Santorini continuing from the Minoan event (∼3.6 ka) to 1950, while Nisyros last erupted in 1878–85. The CSKA rift is also marked by a dyke system along the Santorini caldera and aligned submarine domes extending NE from Kolumbo. Both rifts are slightly oblique to the Aegean volcanic arc, with NW–SE crustal extension confirmed by Global Positioning System, showing 4–5 mm a −1 extension between the eastern Cycladic and southern Dodekanese islands. These rift geometries reflect deep tectonic processes related to magma generation and shallow crustal deformation above the East Mediterranean subducted slab.

Abstract The amounts of volatiles emitted from large Plinian eruptions are typically estimated using the difference between their concentration in silicate melt inclusions formed at depth, and their concentration in the partially degassed glassy groundmass of tephras (the so-called petrologic method). However, a pre-eruptive fluid phase coexisting with the magma prior to eruption may add significantly to the emission budgets. We have combined previously published chlorine emission data obtained by the petrologic method from seven Plinian eruptions along the Central American Volcanic Arc (CAVA) with new data obtained from magmatic fluid inclusions in the same samples. The presence of the magmatic fluid inclusions demonstrates the pre-eruptive criticality of these volcanic systems. The pre-eruptive magmatic fluid phase of silicic CAVA eruptions is water dominated, and contains on average 5 ± 3.5 mass% NaCl equivalents and 5 ± 4 mass% CO2 with no systematic along-arc variations. The pressures obtained from the typical magmatic fluid inclusions range between 140 ± 30 and 170 ± 30 MPa for the various eruptions, which corresponds to minimum pre-eruptive water contents in the melts between 4.8 and 5.2 mass%. We consider a scenario where each magma coexists with between 1 and 5 volume % pre-eruptive fluid, which is erupted together with the magma, and thus adds on average 6 to 30 mass % “excess” Cl to the degassing budgets determined by the petrologic method, and by inference also represents minimum values for “excess” Br degassing. The high efficiency of Br for ozone destruction in the stratosphere is enhanced through interactions with sulfur aerosols present in an eruption column, causing average increases in stratospheric halogen loading, referred to as equivalent effective stratospheric chlorine (EESC), between 6 and 97% per eruption. Depending on the amount and composition of a pre-eruptive fluid phase, the estimated stratospheric loading of a Plinian eruption may thus be doubled compared to data from the petrologic method. Fluid inclusion data from other large eruptions may therefore be used to significantly revise the global emission budgets and the effects of stratospheric ozone destruction related to Cl and Br from large explosive eruptions.

ABSTRACT Explosive volcanic eruptions can alter hydrogeomorphic conditions, manifesting in fluvial stratigraphic records by abrupt changes in sediment composition, channel geometries, and stacking patterns. Recognition of these kinds of perturbation is important to reconstruct the timing of volcanism and paleogeography linked to tectonic evolution. In this study, we investigate coastal outcrops of the Cretaceous Goseong Formation in the Gyeongsang Basin on the southern Korean Peninsula to identify early fluvial responses to explosive volcanic eruptions and concomitant changes in fluvial sedimentation and its architecture. The Goseong Formation consists of low-sinuosity braided stream (FA-1) and calcrete-bearing floodplain (FA-2) deposits, with ignimbrite (FA-3) in the uppermost part of the studied successions. These are interpreted to have been deposited on alluvial plains flanked by a growing continental volcanic arc (Gyeongsang Volcanic Arc). Field examination and sediment compositional analyses suggest that the Goseong Formation is characterized by vertical variations, including: i) sediment composition from terrigenous clastic to volcanogenic sediments, ii) geometry of channel deposits from multi-story, sheet-type (apparent width to thickness (W/T) ratio = 26.4) to single- to multi-story, ribbon-type (W/T ratio = 11.7), and iii) an increase in the thickness ratio of crevasse channel and splay deposits to floodplain fines. These transitions reflect modifications of fluvial sedimentation via onset of influx of the volcanogenic sediments derived from the Gyeongsang Volcanic Arc. In contrast to classic models, channel narrowing is interpreted to have resulted from rapidly aggrading in-channel beds driven by influx of volcanogenic sediments and limited lateral migration caused by pre-existing plant ecosystems and early cementation. At given flood discharges, the raised in-channel beds, by supply of volcanogenic sediments, promoted frequent overbank flooding, leading to the common appearance of crevasse channel and splay deposits in the upper Goseong Formation. This concurrent aggradation of both in-channel beds and adjacent floodplain areas rapidly perched trunk channels, triggering frequent channel avulsion that ultimately prevented channel widening. Therefore, the upper Goseong Formation can be considered a record of early fluvial responses to the onset of explosive volcanic eruptions, and our findings provide new insights into the evolution of volcano-sedimentary successions in nonmarine environments.

Slab-derived fluid contributes to subducted material recycling and crust growth: Insights from the arc volcanics in East Junggar (NW China)

Abstract Subduction zones are integral to Earth's deep water cycle, influencing magmatism, lithosphere dynamics and seismicity. They often exhibit development of extensional processes in the upper plate, which may lead to volcanic arc splitting and backarc basin opening. Here, we investigate numerically the factors controlling arc rifting and back‐arc opening and basin evolution, emphasizing the roles of slab dehydration, and melting processes linked to upper plate thermal structures and variable sediment fluxes. Using an extensive suite of 2D and 3D thermo‐mechanical models, we assess intra‐arc rift initiation timing in the upper plate, lithospheric thinning, and arc rifting patterns. Model results reveal that higher crustal temperatures and sedimentation rates enhance melting and crustal weakening along the arc, facilitating strain localization and faster roll‐back, but may simultaneously diminish stress transfer efficiency. Additionally, 3D modeling captures along‐strike variations, including slab tearing and toroidal mantle flows, offering insights into the complex interplay of subduction dynamics and their effect for arc rifting. These findings are compared with natural laboratories in the Mediterranean and in retreating subduction systems of SE Asia.

Intra-oceanic arc subduction within the Meso-Tethys Ocean constrained by arc crust remnants in the Lagkorco ophiolite, Central Tibet

As the largest active convergent orogenic system, the Himalaya-Tibetan Plateau and southeast Asia stand out as globally significant tectonomorphic features. Mesozoic and Cenozoic tectonic convergence among the Eurasian, Australian-Indian and Pacific plates, involving oceanic subduction, arc accretion, and continental collision has not only formed the world's highest Himalaya-Tibetan Plateau and geometrically diverse volcanic arcs in east and southeast Asia, but also reactivated ancient orogens in central Asia. These tectonically diverse regions also host complex topography, environment, and climate systems, including the Asian monsoon which impacts about half of the global population. Publications in this thematic issue present the latest multidisciplinary advances in Mesozoic and Cenozoic tectonics, landscape evolution, paleoclimate records, geohazards, and their interactions in and around the Tibetan Plateau and southeast Asia.

Diagnostic implications of shortwave-thermal infrared characteristics of typical alteration minerals for mineral exploration in continental volcanic arcs: A case study of the Zhalong Cu-Sn polymetallic deposit, Tibet

This geochemical study concerns the Al-Teeb River sediments that accumulate in the river course or river basin. The river is one of the seasonal rivers in Iraq, located in the Missan Governorate in southeastern Iraq, northeast of Amara City. It originates from the Himrin mountains near the Iranian border and flows into Hor Al-Snnaf. It has a maximum length of about 63 km and runs through the Al-Teeb District. Eight samples were collected and subjected to geochemical analyses by XRF. Numerous geochemical parameters and major and trace element relationship diagrams have been used to infer the origin and type of sediments, paleoclimate, and source rocks. The average chemical alteration index (44.12) indicates that the sediments have undergone low to moderate weathering. Results obtained from the chemical index of weathering (55.043), plagioclase index of alteration (50.5), and index of chemical variability (2.37) support this conclusion and confirm the low weathering of the source rocks and low maturity. The climate of source rocks is semi-arid to sub-humid and mean annual temperature is 15.22°C. The chemical classification of Al-Teeb river sediments is greywacke and originated from continental arc or oceanic arc environments.