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From integrated textural and compositional studies of auriferous and barren pyrite/marcasite in the epithermal Axi gold deposit, China, we have identified a relationship between multiple gold mineralizing events, mafic magma recharge, and fluid-rock reactions. Three generations of pyrite (Py1–3) and four generations of marcasite (Mar1–4) record episodic gold mineralizing events, followed by silver-copper-lead-zinc-cadmium enrichment. The gold mineralizing events are recorded by high concentrations of subnanometer-sized gold in Py1, Py3, and Mar3 (max. = 147, 129, and 34 ppm, med. = 39, 34, and 12 ppm). Based on previous Re-Os age determinations of pyrite and U-Pb zircon ages of the andesitic wallrock, these gold events slightly postdate pulsed mafic magma recharge and represent the incursion of Au-As-S-rich magmatic volatiles into circulating meteoric water. Silver-Cu-Pb-Zn-Cd enrichment in Py2, Mar2, and Mar4 are consistent with quiescent degassing and gradual Ag-Cu-Pb-Zn-Cd enrichment in an evolved felsic magma. Barren Mar1 records the dominance of meteoric water and a limited magmatic fluid contribution. High-Co-Ni-V-Cr-Ti contents in porous cores of Py1 and Mar2 are attributed to wall rock alteration and dissolution-reprecipitation. The results provide convincing evidence that the metal budget (especially for Au, Ag, Cu, Pb, Zn, Sb) of the hydrothermal fluids and sulfides in epithermal systems are controlled by the influx of magmatic fluids and associated magma, whereas the enrichment of certain fluid-immobile elements, such as Co, Ni, V, Cr, and Ti, is caused in part by fluid-rock interaction. [ABSTRACT FROM AUTHOR]

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To better understand the behavior of Ti isotope fractionation during alkaline magma differentiation, we studied well characterized alkaline lavas from St. Helena Island (South Atlantic), as well as their titanomagnetite separates. The lavas are classified into three groups according to petrographic observations and major element composition. Group 1 and Group 2 samples (5 to > 13 wt.% MgO) have a narrow δ49/47Ti range (− 0.02 to 0.05‰), suggesting that Ti isotopic fractionation is insignificant in less evolved basaltic lavas. Conversely, Group 3 samples (MgO < 5 wt.%) are saturated with titanomagnetite and display a wide range in δ49/47Ti (− 0.02 to 1.96‰). The δ49/47Ti values for Group 3 samples show significant correlation with TiO2 and SiO2 content, as well as with Mg and Fe isotopic values. Moreover, titanomagnetite phenocrysts from Group 3 rocks have remarkably lighter δ49/47Ti values (− 0.54 to 0.01‰) relative to the corresponding whole rock (− 0.02 to 0.21‰), indicating that titanomagnetite crystallization exerts significant control over the δ49/47Ti of Group 3 samples. These observations are further supported by modeling calculations. Together with published Ti isotope data, the results demonstrate that the range in Ti isotopic evolution in alkaline, calc-alkaline and tholeiitic magmatic systems is controlled by fractional crystallization of diverse Fe-Ti oxides with contrasting Ti isotopic compositions. This makes Ti stable isotopes an important geochemical tracer for magma evolution. [ABSTRACT FROM AUTHOR]

Continental arcs are associated with volcanism concentrated into two main belts—the main arc and back arc, often separated by fold and thrust belts. The Loicas Trough, Argentina, is a post-orogenic extensional feature that obliquely cuts the fold and thrust belts. The trough hosts large Pliocene–Holocene volcanic centres, including Domuyo and Tromen, that lie between the main arc and back arc and thus provide a rare window into this setting. We present major and trace element data for the Loicas Trough, which we combine with geochemical modelling using the Magma Chamber Simulator (MCS) to explore the origin and evolution of the volcanism. The lavas display a wide continuous range from alkaline basalts to subalkaline rhyolites. Trace elements reveal variable extents of arc enrichment (2 < Nb/U < 28), which correlate with proximity to the trench and differentiation indices. Our results and MCS models indicate that the Loicas Trough parental magmas formed from compositionally zoned mantle. Best-fit models indicate that the differentiation occurs at middle and upper crustal levels, in sharp contrast to lower crustal hot zones beneath main arcs. Assimilation of partial crustal melts drives compositional evolution and obscures source signatures. Pure or high fraction end-member partial crustal melts are also identified at Domuyo based on their low Ba (~ 250 ppm) and moderate Sc contents (~ 8 ppm). We find evidence of similar lavas in transtensional settings adjacent to continental arcs worldwide, which do not adhere to the main versus back arc volcanism binary. We suggest the term arc-adjacent magmatism, where compositions are mainly controlled by extensive assimilation and reworking in the middle to upper crust. [ABSTRACT FROM AUTHOR]

The Naozhi deposit of northeast China comprises intermediate-sulfidation epithermal-style veins and subeconomic, porphyry-style Cu mineralization hosted by dioritic to granitic plutons, which formed at ca. 130 Ma. These intrusive phases were fed by magmas that ponded at mid- to upper-crustal levels and were finally emplaced at < 0.6 kbar based on amphibole geobarometry. The magmas were moderately oxidized (∆NNO − 0.35 to 2.21; with NNO being the nickel–nickel–oxide buffer) and water-rich (mostly > 4 wt. %), and likely experienced a relatively prolonged evolution in the shallow crust rather than at depth. Magma devolatilization and fluid exsolution at shallow-crustal levels lead to decreases in both oxygen fugacity (log ƒO2 − 10.96 to − 14.13) and water content (6.53 to 2.26 wt. %) at < 2.5 kbar pressures. Thermochronological data of zircon and apatite, thermal history modeling, and geological preservation record complex time–temperature histories of the mineralized intrusive rocks, from the cooling of the parent magma itself through burial by younger volcanic rocks to protracted erosion with time. It is estimated that < 2 km of pre-mineralization material was removed from the top of the Naozhi magmatic–hydrothermal system from the Early Cretaceous to present. A 108 ± 2 Ma volcanic event possibly tilted the hydrothermal system, but buried the ores, protecting them from extensive erosion. [ABSTRACT FROM AUTHOR]

Granitic magma bodies form in the ephemeral part of magma mush systems and are emplaced by a variety of mechanisms in different tectonic settings. This study investigates how granitic magma emplacement processes and tectonomagmatic interactions assert control over the architecture of mush state pluton‐scale magma transport pathways. The 1.45 Ga shallow‐crustal Götemar pluton is a 4.5 km diameter circular pluton that consists of three granite units: a coarse‐grained red granite, a medium‐grained pale to red granite, and fine‐grained pale microgranite sheets. We employed geological mapping supported by Anisotropy of Magnetic Susceptibility (AMS) to examine the magmatic and regional tectonic controls on late‐stage magma transport in the Götemar granitic magma mush system. Multiple parallel arcuate subhorizontal microgranite and medium‐grained granite sheets (from 0.1 to 10s of meters thick) were mapped within the pluton. The arcuate sheets pinch out from the northern part of the pluton toward the SE inferring magma propagation direction. A dominant set of vertical granitic sheets within the granite body strikes NW‐SE. The AMS fabrics are contact‐parallel in the main medium‐grained granite body and indicate inflation. Within the microgranite sheets, the AMS fabrics are parallel to the sheet strike and support a sheet propagation direction to the SE. The Götemar pluton displays a clear link between arcuate (concentric) magma‐transporting sheets and concentric strain‐partitioning related to the intrusion of medium‐grained granite magma. The vertical magma sheet orientations are consistent with an NE‐SW extensional stress field that is associated with the extensional back‐arc stress regime of the contemporary Hallandian Orogen. Plain Language Summary: The eruptive products of volcanoes are thought to be stored in pockets of melt in crystal‐dominated magmatic systems called crystal mushes prior to volcanic eruptions. An understanding of where magma is stored and how it is transported in mush systems is important in order to predict the eruptive behavior of the volcanic system. This contribution investigates the magma transport pathways in the Götemar granite in Sweden and its relationship to local magmatic deformation and regional deformation related to the Hallandian mountain building event. We show that magma is transported in vertical sheets parallel to the front of the Hallandian Orogen and laterally in sub‐horizontal arcuate sheets that reflect the circular shape of the granite pluton. Our study highlights the importance of understanding the shape and the formation of the magmatic granite body for deciphering the melt transport in the magma mush system under volcanoes. Key Points: Subhorizontal magma transport in a granitic magma mush controlled by magma emplacement structuresVertical magma sheets in granitic magma mush controlled by the regional stress fieldMagma transported in concentric magma fingers in the circular Götemar granite pluton [ABSTRACT FROM AUTHOR]

Earth-like planets orbiting M-dwarf stars, M-Earths, are currently the best targets to search for signatures of life. Life as we know it requires water. The habitability of M-Earths is jeopardized by water loss to space: high flux from young M-dwarf stars can drive the loss of 3–20 Earth oceans from otherwise habitable planets. We develop a 0-D box model for Earth-mass terrestrial exoplanets, orbiting within the habitable zone, which tracks water loss to space and exchange between reservoirs during an early surface magma ocean phase and the longer deep-water cycling phase. A key feature is the duration of the surface magma ocean, assumed concurrent with the runaway greenhouse. This time-scale can discriminate between desiccated planets, planets with desiccated mantles but substantial surface water, and planets with significant water sequestered in the mantle. A longer-lived surface magma ocean helps M-Earths retain water: dissolution of water in the magma provides a barrier against significant loss to space during the earliest, most active stage of the host M-dwarf, depending on the water saturation limit of the magma. Although a short-lived basal magma ocean can be beneficial to surface habitability, a long-lived basal magma ocean may sequester significant water in the mantle at the detriment of surface habitability. We find that magma oceans and deep-water cycling can maintain or recover habitable surface conditions on Earth-like planets at the inner edge of the habitable zone around late M-dwarf stars – these planets would otherwise be desiccated if they form with less than ∼10 terrestrial oceans of water. [ABSTRACT FROM AUTHOR]

An anomalous crust and lithospheric mantle in the Deccan Volcanic Province are imaged below a 160 km long W‐E profile through the joint inversion of receiver functions and surface wave dispersion. The upper crust has an unusually low S‐wave velocity (Vs ∼ 3.3–3.5 km/s) at 8–17 km depth, underlying a 4 km thick high‐velocity layer (Vs > 3.8 km/s). The low velocity possibly represents the frozen magma reservoir, the source for the magma eruption at ∼65 Ma due to the interaction of the Reunion plume with India. The shallow, high‐velocity layer could be basaltic mafic intrusions responsible for the production of massive CO2 degassing. The Moho deepens beneath the west coast to ∼45 km due to 10–15 km of magma underplating. The mantle plume scar is seen as thinned lithosphere (80–100 km), with the presence of long‐lived low‐velocity layers in the shallow mantle attributed to the presence of sulfide melts. Plain Language Summary: The Deccan volcanism occurred around 65 Ma ago when India and Seychelles, moving northward, interacted with the Reunion plume, leading to increased temperature and hence melting at the upper mantle. The buoyant magma moved upward and ponded toward the crust‐mantle boundary. When the overlying crust failed due to high overpressure and/or magma buoyancy, the magma ascended via dikes and assimilated into a shallow crust. The process is expected to produce significant crust and upper mantle modifications due to increased heat transfer and chemical transformation during magma ascent. Existing geophysical knowledge of the Deccan traps does not provide the signature of a magma ascent path and evidence for crustal transformations. Using data from a recent 160 km‐long broadband seismological experiment, we construct a detailed model of the crust and uppermost mantle, showing a complete magma plumbing system. The result shows evidence for lithospheric thinning and well‐preserved deformation in the shallow mantle in the form of sulfide melt, magma ponding at the crust‐mantle boundary beneath the coastal basin, an extensive low‐velocity layer in the upper/mid crust possibly representing the horizontally elongated frozen magma reservoir, and a densified high‐velocity layer in the shallow crust (4–8 km depth) representing basaltic mafic intrusions. Key Points: First seismic evidence of the magma plumbing system in the Deccan Volcanic Province, IndiaA thinned lithosphere with low‐velocity layers in the western segment adjoining the coastA low‐velocity layer at 8–17 km depth possibly represents a frozen magma chamber underlying a 4 km thick high‐velocity layer [ABSTRACT FROM AUTHOR]

Tholeiitic basalts and trachytes of the bimodal association of Wangtian'e volcano are studied. It is shown that trachytes formed with the leading role of crystal fractionation of the parental tholeiitic magma. It has been identified from the melt inclusion study that hedenbergite and plagioclase phenocrysts of trachytes from Wangtian'e volcanic neck crystallized in the temperature range of 1080–1100 and 1050–1060°C, respectively. After heating experiments with melt inclusions in plagioclase of trachytes, in some cases relics of carbonates and CO2 were observed in the inclusions. The trachyte phenocrysts host water-bearing Fe-rich globules and CO2 inclusions with carbonate phases. The Fe-rich silicate globules are often intergrown with titanomagnetite and are covered by amorphous carbon films. A model is suggested explaining the formation of water-bearing Fe-rich globules and CO2 inclusions with carbonate relics as a result of silicate–silicate and silicate–carbonate liquid immiscibility, that was caused by the evolution of the parental basaltic melt. Upon the trachytic melt ascending to the surface, the ferrocarbonate liquid was decomposed on magnetite, carbon, and carbon dioxide. [ABSTRACT FROM AUTHOR]

The Miocene Columbia River Basalt Group (CRBG) of the Pacific Northwest of the United States is the world's youngest and smallest large igneous province. Its earliest formations are the Imnaha, Steens, and now the Picture Gorge Basalt (PGB), and they were sourced from three different dike swarms exposed from SE Washington to Nevada to northcentral Oregon. PGB is often viewed to be distinct from the other formations, as its magmas are sourced from a shallow, relatively depleted, and later subduction-induced metasomatized mantle, along with its young stratigraphic position. It has long been known that the lowermost American Bar flows (AB1&2) of the Imnaha Basalt are chemically similar to those of the PGB, yet the Imnaha Basalt is generally thought to carry the strongest plume source component. These opposing aspects motivated us to revisit the compositional relationships between AB1&2 and PGB. Our findings suggest that tapping a shallow, variably depleted, and metasomatized mantle reservoir to produce earliest CRBG lavas occurred across the province, now pinpointed to ~17 Ma. Moreover, compositional provinciality exists indicating regional differences in degree of depletion and subduction overprint that is preserved by regionally distributed lavas, which in turn implies relatively local lava emplacement at this stage. [ABSTRACT FROM AUTHOR]

The mafic microgranular enclaves (MMEs) from Mesozoic intermediate-acid magmatic rocks, widely developed along the Fujian coast, are considered to be the results of large-scale crust–mantle interaction by magma mixing. This paper is based on zircon U-Pb chronology, along with zircon Hf isotope and mineral analyses for the host granite and MMEs from Langqi Island, in order to investigate the magma mixing mechanism of the Langqi pluton in Fuzhou, Southeast China. The results indicate that the MMEs were emplaced during the late Early Cretaceous (98.9 ± 2.2 Ma), identical to the age of the granite (100.1 ± 1.1 Ma) within the error range. The zircon εHf(t) values for the granite and MMEs are in the ranges of −2.1~0.0 and −1.7~+1.1. The zircon Hf isotope data indicate that both the granite and MMEs were predominantly derived from the ancient crustal basement of Cathaysia, with a partial mantle-derived contribution. The An values of plagioclase phenocrysts with oscillatory zoning patterns in the MMEs show oscillatory changes from the core to the rim, indicating multiple mixing events between the two magmas with different compositions. Amphiboles in the MMEs show characteristics of crust–mantle contamination, and the Ti migrated from the mafic magma with high concentration to the felsic magma with low concentration during the magma mixing process. Biotites in the host rock and MMEs belong to primary biotite, and they have relatively high MgO contents (ave. 12.78 wt.%) and relatively low FeOT/(MgO + FeOT) ratios (ave. 0.56), showing characteristics of crust–mantle contamination. The crust–mantle magma interaction in a crystal, mushy state played a significant role in controlling the formation and evolution of the Langqi pluton. The magmatism was predominantly sourced from mixing between the mantle-derived mafic magma and the crust-derived felsic magma during the subduction of the Paleo-Pacific Plate, resulting in the formation of the Langqi doleritic veins, granites, and MMEs. [ABSTRACT FROM AUTHOR]

Post-collisional potassic magmatic rocks are widely distributed in the northwestern Tibetan Plateau, yet their magmatic processes remain poorly understood. Here, we present a comprehensive analysis of the whole-rock major and trace elements, as well as the mineral textures and chemistry of the Dahongliutan volcanic rocks in the NW Tibetan Plateau, aiming to reveal the magmatic processes prior to eruption and speculate on the triggering mechanism. The results show that the Dahongliutan volcanic rocks are potassic trachyandesites, which undergo polybaric crystallization during magma ascension. The phenocrysts in these potassic rocks exhibit various textural and compositional zoning styles. The green cores of green-core clinopyroxenes show textural (e.g., resorption texture) and chemical (Fe-rich) disequilibrium with the host rock compositions, suggesting that they may be antecrysts and crystallized from early batches of more evolved magmas. Additionally, alkali feldspar phenocrysts also display disequilibrium characteristics (e.g., overgrowth rim and sieve texture), indicating hot mafic magma recharge and mixing in the magma plumbing system. Therefore, we conclude that the disequilibrium textural and compositional features of green-core clinopyroxene and alkali feldspar phenocrysts provide evidence of magma recharge and mixing prior to eruption. Furthermore, it is likely that the eruption of the Dahongliutan volcano was triggered by magma recharge. [ABSTRACT FROM AUTHOR]

A compilation of the thicknesses of contact metamorphic aureoles (CMAs) developed around intermediate to felsic plutons shows many CMAs are far broader than expected by commonly used thermal models for pluton emplacement. Shortfalls in the amount of heat potentially provided based on pluton size, compared to that needed to form the observed CMA, can be accounted for if some hot magma has been lost by volcanic eruption after passing through the pluton domain and replaced by new hot magma. A high ambient temperature may also contribute to broad CMA formation. However, the presence of coeval pairs of both narrow and broad CMAs in the same area requires contrasting types of pluton growth history. Our thermal modeling, constrained by the peak metamorphic temperature, shows the broad CMA of a well-developed pair of CMAs in the Hongusan area of Japan is due to a magmatic history, including magma tapping and replenishment. A global compilation of CMAs suggests more than 30% of plutons are associated with broad CMAs and fed contemporaneous volcanic eruption. [ABSTRACT FROM AUTHOR]

The current debate on volcanic-plutonic connection is centered on whether eficient liquid-crystal segregation dominates the evolution of a mushy reservoir to produce evolved, crystal-poor rhyolite and cumulate leftover. However, magma recharge may remarkably influence the evolution of a mushy reservoir and obscure the evidence of liquid-crystal segregation. This complexity poses a challenge to exploring the connection of volcanic-plutonic rocks. This study investigates the Qinzhou Bay granitic complex (~250–248 Ma) from South China, which contains crystal-poor (<19 vol%) peraluminous rhyolites and subsequent crystal-rich (28–54 vol%) porphyries. Although the rhyolite and porphyry units have a close spatio-temporal link, they do not share a fractionation trend and similar whole-rock Sr-Nd-O isotopic compositions; thus, a direct connection is not evidenced. We further present textural analyses, mineral and melt inclusion compositions, thermobarometry (the combination of Ti-in-zircon thermometer and Ti-in-quartz thermobarometer), and thermodynamic modeling to examine the alternative interpretations, i.e., the two units may have intrinsically independent origins or the connection of the two units has been obscured. For the rhyolite unit, thermobarometric results reveal a polybaric storage system consisting of middle (>600 ± 80 MPa) and upper (~150 ± 40 and ~60 ± 20 MPa) crustal reservoirs. Variations in quartz Fe content and chlorine-rich, metaluminous melt inclusions suggest that magma hybridization with less-evolved metaluminous magmas occurred at both crustal levels. In particular, the elevated Fe contents in the quartz population that crystallized at the shallowest level (~60 ± 20 MPa) suggest that recharge magmas were directly injected into the shallowest reservoir. Deviation of the whole-rock composition from the liquid evolution trend recorded in melt inclusions suggests a combined efect of magma mixing and crystal-melt segregation processes in upper crustal reservoirs. Thermodynamic modeling and mass balance calculations suggest that the whole-rock composition of the rhyolite could be reproduced by mixing between regionally exposed dacites and segregated melts at crystallinities of 50–60% (using parental magma represented by the least-evolved melt inclusion). For the porphyry unit, thermobarometric results reveal magma storage at middle (more than 450 ± 40 to 550 ± 40 MPa) and upper (110 ± 20 to 140 ± 20 MPa) crustal levels. The small-scale oscillatory zonation of plagioclase, the pervasive resorption of quartz and alkali feldspar, and the presence of peraluminous microgranular enclaves in the porphyries suggest a recharge event of metasediment-sourced magmas, triggering reactivation and convection of the reservoir. Autoclastic and overgrowth textures of quartz, plagioclase, and alkali feldspar phenocrysts and development of columnar jointing suggest that the reactivated porphyritic magmas ascended and emplaced at ultrashallow levels (~30 ± 10 MPa). Because of the similar storage pressures, the porphyries may represent remobilized cumulates of rhyolitic magmas, whereas the texture and geochemistry of the cumulate-liquid pair were modified, a key factor rendering a cryptic connection between the rhyolite and porphyry. Alternatively, the plumbing systems feeding the rhyolite and porphyry units are horizontally independent or vertically discrete, but this circumstance is inconsistent with the same evolution trend of quartz Fe and Al contents of the rhyolite and porphyry. Our study highlights that whole-rock composition may record blended information of complex processes, and caution should be taken when whole-rock composition is used to extract information of a single process. Multi-method constraints are required to evaluate the influence of recharge processes on the modification of liquid-cumulate records, and big data analysis on the basis of geochemistry should be conducted with caution to avoid biased understanding. [ABSTRACT FROM AUTHOR]

Decompression-induced crystallization is an important process that controls the behavior of volcanic eruptions because it strongly affects magma rheology and degassing behavior in the shallow parts of volcanic conduits. Several decompression experiments have been performed to understand and model the crystallization processes; however, the effect of superheating (i.e., heating above the liquidus temperature for a definite period of time) before decompression has not been elucidated, despite the proposal of its importance in previous cooling experiments. As the superheating influences the number of pre-existing crystals and melt homogeneity, it is expected to control decompression-induced crystallization. In this study, we investigated the effects of pre-existing crystals and melt homogeneity on crystallization during the decompression of rhyodacitic magma at a temperature of 900 °C. The magma studied herein has a liquidus temperature of ~920 °C. Five starting materials were prepared via heating at different superliquidus temperatures (940, 970, 1050, and 1300 °C) and a sub-liquidus temperature (900 °C) using an internally heated pressure vessel and a cold-seal pressure vessel, respectively. Decompression experiments using these starting materials were conducted from 130 to 30 MPa at decompression rates of 5, 20, and 100 MPa h–1. When the melt was completely homogenized (at 1050 and 1300 °C), no crystals were formed at 100 MPa h–1 and the small amounts of crystals heterogeneously formed along the capsule wall were found at 5 and 20 MPa h–1. At the same decompression rate, the number density of plagioclase formed during decompression increased as the superheating temperature decreased from 970 to 900 °C, despite the higher number densities of pre-existing crystals before decompression in the samples with lower superheating. Such finding indicates that nucleation occurs easily when the number density is initially high. This result is inconsistent with the idea that nucleation occurs when supersaturation is sufficient to overcome the energy barrier for nucleation, and the growth of pre-existing crystals decreases supersaturation. In contrast, the results of our experiments can be explained by considering that higher superheating results in a more homogeneous melt structure with few pre-crystal clusters, which are growth sites, and ultimately the suppression of nucleation. Based on these results, we conclude that pre-existing crystals and melt homogeneity strongly affect the crystal texture formed by decompression. For application to natural systems, the high number density of microlites found in natural samples may be due to heterogeneous nucleation caused by the presence of pre-crystal clusters and other mechanisms. Furthermore, the superheating of magma in a reservoir caused by the injection of high-temperature mafic magma may influence the crystal texture during magma ascent and, hence, control the explosivity of the eruption. [ABSTRACT FROM AUTHOR]

The study focuses on examining the formation and deposition process of sedimentary formations containing oil and gas in the sedimentary basins on Vietnam's continental shelf. Determining the distribution trend, characteristics, and scale of these sediments is of great importance. By analyzing field samples, lithologic data, references, documents, and conducting geological-geophysical research, the author has investigated the formation process of lower Miocene sediments with oil and gas in the Cuu Long basin. Through the study of identified characteristics, distribution scale, sedimentological features, and seismic data, the author has shed light on the process of formation and the trend of hydrocarbon accumulation in the lower Miocene sedimentary basin of the Cuu Long Basin. The predominant trend of sediment deposition distribution is observed from the continental portion of the Dalat Zone towards the Cuu Long Basin, cutting through it in a west-east direction. Furthermore, the research reveals that the lower Miocene sandstone in the Cuu Long Basin can be divided into two sequences: BI.2 and BI.1, both originating from granitoid sources. These findings also contribute to our understanding of the evolution of magma-sediment processes in the studied area and its surrounding regions. Additionally, tectonic extensions and climate changes, which lead to sealevel rise during the lower Miocene sequence, create favorable conditions for the deposition and accumulation of sedimentary particles. [ABSTRACT FROM AUTHOR]

Peperites are volcanosedimentary materials generated by the mingling of magma and unconsolidated wet sediments. They have unique insights into submarine volcanisms and the tectonic environments where they form. For the 1st time, the authors identified two types of peperites (blocky and fluidal) hosted by micritic limestone rocks in the Walash Volcanosedimentary Group of the Mawat area, Kurdistan Region-Iraq. They are designated as peperitic facies one and two (PF1 and PF2) and consist of black basaltic rocks mixed with chocolate-brown micritic limestone rocks. Their abundance demonstrates the contemporaneity of deep marine sediment deposition and submarine volcanism during Walash's nascent arc. Despite hydrothermal alteration, the basaltic rocks retained their magmatic textures. Basaltic rocks comprise mainly albite, anorthite, diopside, hematite, and alkali-feldspar. Calcite dominates micritic limestone rocks, while quartz is minor. Based on geochemical data, igneous sections are basaltic rocks with tholeiitic series that are strongly enriched in Light Rare Earth Elements with low concentration ratios of (La/Yb) and (Sr/Y), indicating geochemical affinity to normal island arc basalt with a primitive arc signature. Furthermore, their formation is thought to be caused by partial melting of subducted slabs deep within 30 km and the associated derived fluids above the subducted slab. Thirteen species of planktonic foraminifera (Morozovella) are identified through paleontological research and biostratigraphy. Using these various tools lead the authors to illustrate the tectonic setting of the formation of peperitic rocks in arc fronts of the subducted Walash arc during the Middle to Late Paleocene (60 Ma). [ABSTRACT FROM AUTHOR]

A detailed mineral-scale study was conducted on pumices of the latest, dominantly explosive eruption epoch (56–30 ka) of Ciomadul, the youngest, long-dormant volcano in eastern-central Europe for characterizing the magma storage system and for understanding better the changes in eruption style from effusive to explosive. The mineral cargo of dacitic pumices enables us to constrain the conditions of the pre-recharge crystal mush, the recharge magmas and the post-recharge magma prior to eruptions. A careful evaluation of the results yielded by various thermometers, barometers, oxybarometers, chemometers and hygrometers as well as direct comparison with experimental data were necessary to select the appropriate techniques and therefore to constrain the conditions for the Ciomadul magmatic system. Beneath the volcano, a felsic crystal mush body is inferred at 8–12 km depth comprising slightly oxidized (0.5–1.6 ∆NNO), low-temperature (680–750 °C), highly crystalline magma. This zone is underlain by a deep magma storage zone with less evolved, hot (> 900 °C) magma at 16–40 km depth. The dominantly explosive volcanism after the effusive eruptions (160–90 ka) can be explained by the ascent of distinct recharge magmas. They contained high-Mg (MgO > 18 wt%) amphibole, which could have crystallized from ultrahydrous (H2O > 8 wt%) magma at near-liquidus conditions. The rates of amphibole overgrowth and microphenocryst formation require weeks to months for the magma mixing and the eruption events. The hybridized melt became more oxidized and contained dissolved water in around 5.5 wt% at temperature of 790–830 °C calculated from the re-equilibrated Fe-Ti oxides. These magma properties along with the degree of crystallinity (27–38 vol% crystals) favored rapid magma ascent and an explosive style eruption. Thus, the strongly hydrous nature of the recharge magma in addition to the crystallinity and H2O content of the pre-eruption magma plays an important role in controlling the eruption style. [ABSTRACT FROM AUTHOR]

We present the geochemical and Sr–Nd–Pb isotopic data and the petrological evolution of primitive basaltic lavas that erupted from the Miocene to Quaternary in the East Anatolia Collision Zone to understand the geodynamic conditions and the change in the lithospheric mantle over time. Major trace element abundances, Sr–Nd–Pb isotopic compositions and petrological models show that the primitive basaltic samples were not affected by crustal contamination and fractional crystallization. They are derived from a depleted MORB mantle modified by melts derived from subducted sediments. The primitive melts of the Miocene and Quaternary series were derived from an amphibole-bearing garnet lherzolitic mantle and an amphibole-bearing garnet–spinel lherzolite mantle source, respectively. In contrast, the Pliocene basaltic melts were formed by mixing melts originating from both an amphibole-bearing spinel and garnet lherzolite. Our thermodynamic calculations indicate that the lithosphere–asthenosphere boundary (LAB) is about 30 km shallower in the Pliocene than in the Miocene.This may be explained by lithospheric delamination in the Early Pliocene. In contrast, the LAB in the Quaternary is approximately 9 km deeper than in the Pliocene, which can be explained by relamination of the mantle lithosphere. Thermal calculations have shown that about 5–11 km of the relamination can occur within 5–6 Ma and that asthenospheric melts can relaminate the base of the thinned lithospheric mantle by cooling, and the presence of the relaminated mantle lithosphere is documented throughout the whole EACZ. [ABSTRACT FROM AUTHOR]

Magmatic volatiles drive pressure, temperature, and compositional changes in upper crustal magma chambers and alter the physical properties of stored magmas. Previous studies suggest that magmatic H2O content influences the growth and longevity of silicic chambers through regulating the size and frequency of eruptions and impacting the crystallinity‐temperature curve. However, there has been comparatively little exploration of how CO2 impacts the evolution of magma chambers despite the strong influence of CO2 on H2O solubility and the high concentrations of CO2 often present in mafic systems. In this study, we integrate the thermodynamic effects of dissolved and exsolved H2O and CO2 with the mechanics of open‐system magma chambers that interact thermally and mechanically with the crust. We applied this model to investigate how intrinsic variations in magmatic H2O‐CO2 content influence the growth and longevity of silicic and mafic magma chambers. Our findings indicate that even with a tenfold increase in CO2 content (up to 10,000 ppm), CO2 plays a minimal role in long‐term chamber growth and longevity. While CO2 content affects the magma compressibility, the resulting changes in eruption mass are balanced out by a commensurate change in eruption frequency so that the time‐averaged eruptive flux and long‐term chamber behavior remain similar. In contrast, H2O content strongly influences chamber growth and longevity. In silicic systems, high H2O contents hinder magma chamber growth by increasing the total eruptive flux and steepening the slope of the crystallinity‐temperature curve. In mafic systems, high H2O contents promote magma chamber growth by flattening the slope of the crystallinity‐temperature curve. Plain Language Summary: Water and carbon dioxide play an important role in the size and frequency of volcanic eruptions. They are also important in determining how much magma chambers can grow and for how long they can remain eruptible. Here, we present computer simulations that allow us to study the feedback between thermodynamic (heat and chemistry related) and mechanical (pressure build‐up and loss related) processes in magma chambers with different amounts of carbon dioxide and water and different magma compositions to understand how magma chambers grow. The outputs of these simulations track how temperature, pressure, volume, and the proportion of crystals, melt, and gas in the magma chamber change over time. Through these outputs, we found that carbon dioxide has minimal impact on how much magma chambers grow and how long‐lived they are. In contrast, we learned that water has a strong impact on how long‐lived magma chambers are and how much they grow. The way water impacts growth and lifespan of chambers is different depending on whether the magma composition is rhyolitic or basaltic. Higher amounts of water cause rhyolitic magma chambers to be shorter‐lived and grow less. In basaltic magma chambers, higher water causes them to be longer‐lived and grow more. Key Points: Magma chamber model couples thermodynamic effects of H2O and CO2 to thermo‐mechanical processes for chamber growth, eruption, and longevityCO2 modulates eruption frequency and size but has minimal impact on the eruptibility, longevity, and growth of shallow magma chambersH2O‐rich silicic chambers can erupt more mass than mafic chambers due to feedback between syneruptive decompression and H2O solubility [ABSTRACT FROM AUTHOR]

Geo- and thermochronological methods were applied to diorites from the Cordillera Central, Luzon, Philippines to understand their emplacement and exhumation history in the island arc mountains. Five zircon U–Pb ages range from 32.54 ± 0.70 to 6.11 ± 0.15 (2SE) Ma, indicating that dioritic magmas intruded the upper crust intermittently during Cenozoic magmatism. Five zircon fission-track (ZFT) pooled ages range from 35.63 ± 2.17 to 6.91 ± 0.36 (2SE) Ma and are generally comparable with the U–Pb ages at each locality. These results suggest that the diorites cooled rapidly below ~ 250–350 °C (i.e., through the partial annealing zone of the ZFT system), following their intrusion. On the other hand, two zircon and five apatite U-Th(-Sm)/He (ZHe and AHe) weighted mean ages, ranging from 11.71 ± 0.36 to 8.82 ± 0.26 and 9.21 ± 0.52 to 0.98 ± 0.09 (2SE) Ma, respectively, indicate a decrease in cooling rates at a lower temperature range, especially through the partial retention zone of the AHe system. This observation suggests that the ZFT ages reflect initial cooling of the dioritic magma, whereas the AHe ages reflect the cooling history associated with regional exhumation following the initial cooling phase. The spatial distribution of the AHe ages suggests that rapid exhumation of the Cordillera Central during the Quaternary resulted from the block-like uplift of the entire mountain range. [ABSTRACT FROM AUTHOR]

Background: Whole genome sequencing (WGS) holds great potential for the management and control of tuberculosis. Accurate analysis of samples with low mycobacterial burden, which are characterized by low (<20x) coverage and high (>40%) levels of contamination, is challenging. We created the MAGMA (Maximum Accessible Genome for Mtb Analysis) bioinformatics pipeline for analysis of clinical Mtb samples. Methods and results: High accuracy variant calling is achieved by using a long seedlength during read mapping to filter out contaminants, variant quality score recalibration with machine learning to identify genuine genomic variants, and joint variant calling for low Mtb coverage genomes. MAGMA automatically generates a standardized and comprehensive output of drug resistance information and resistance classification based on the WHO catalogue of Mtb mutations. MAGMA automatically generates phylogenetic trees with drug resistance annotations and trees that visualize the presence of clusters. Drug resistance and phylogeny outputs from sequencing data of 79 primary liquid cultures were compared between the MAGMA and MTBseq pipelines. The MTBseq pipeline reported only a proportion of the variants in candidate drug resistance genes that were reported by MAGMA. Notable differences were in structural variants, variants in highly conserved rrs and rrl genes, and variants in candidate resistance genes for bedaquiline, clofazmine, and delamanid. Phylogeny results were similar between pipelines but only MAGMA visualized clusters. Conclusion: The MAGMA pipeline could facilitate the integration of WGS into clinical care as it generates clinically relevant data on drug resistance and phylogeny in an automated, standardized, and reproducible manner. Author summary: The genome of Mycobacterium tuberculosis (Mtb), the bacterium that causes tuberculosis, provides important information on drug resistance and can predict with which drug a patient can be best treated for tuberculosis. The Mtb genome also gives information on how Mtb spreads in communities. If the Mtb genomes from two patients suffering from tuberculosis are very similar, then these two patients are likely linked in terms of transmission. Characterizing the genome of Mtb is thus important for controlling the disease in the patient and in the population. We developed the MAGMA pipeline, a software that can accurately identify genomic variants in Mtb, even when the amounts of Mtb bacteria in the patient sample are low and contaminating bacteria are present. The genomic variants identified by the software are then analyzed using the WHO reference to identify the drug resistance profile of a patient's Mtb strain. The genetic distances between genomes are also calculated to identify closely related genomes. Using clinical Mtb samples from 79 patients, we show the strengths and advantages of the MAGMA pipeline. We conclude that MAGMA can rapidly and accurately obtain important genomic information for Mtb in clinical settings and communicates the results in a clinically relevant way. [ABSTRACT FROM AUTHOR]

This paper presents the results of an original short-period magnetotelluric survey performed on Vulcano Island (Italy). The obtained three-dimensional resistivity model details structures up to 2.5 km depth, hitherto unexplored. The La Fossa caldera area corresponds to a moderate resistive anomaly, which extends down to the resolved depth and likely represents a "conduit-like" structure along which magmatic fluids stall and ascend. Other resistive anomalies characterize volcanic edifices, craters, volcanic conduits, and/or eruptive fissures. In addition, the shallower hydrothermal system is detected as a conductive anomaly. Sharp resistivity contrasts generally characterize caldera faults. A main N‒S alignment characterizes the island sector, where considerable amounts of deep subsurface fluids accumulate and mix with the ascending magmas related to the most recent volcanic dynamics. The volcanological interpretation of such findings significantly contributes to understanding the geophysical and geochemical anomalies detected in the last year, which involved the Vulcano shallow hydrothermal system, highlighting the potential for possible hydrothermal/phreatic eruptive events. [ABSTRACT FROM AUTHOR]

Syneruptive magma mixing is widespread in volcanic eruptions, affecting explosivity and composition of products, but its evidence in basaltic systems is usually cryptic. Here we report direct evidence of mixing between basanitic and tephritic magmas in the first days of the 2021 Tajogaite eruption of Cumbre Vieja, La Palma. Groundmass glass in tephritic tephra from the fifth day of the eruption is locally inhomogeneous, showing micron-scale filamentary structures of Si-poor and Fe-, Mg-rich melt, forming complex filaments attached to bubbles. Their compositional distribution attests the presence of primitive basanitic magma, with compositions similar to late-erupted melts, interacting with an evolved tephritic melt during the first week of the event. From filament morphology, we suggest their generation by dragging and folding of basanitic melt during bubble migration through melt interfaces. Semi-quantitative diffusion modelling indicates that the filamentary structures are short-lived, dissipating in timescales of tens of seconds. In combination with thermobarometric constraints, we suggest a mixing onset by sub-Moho remobilization of a tephritic reservoir by basanite input, followed by turbulent ascent of a mingled magma. In the shallow conduit or lava fountain, bubble nucleation and migration triggered further mingling of the distinct melt-phases. This phenomenon might have enhanced the explosive behaviour of the eruption in such period, where violent strombolian explosions were common. [ABSTRACT FROM AUTHOR]

This work responds to what was reported in various audio-visual media channels and to queries and explanations from individuals and local residents on the causes of gaseous and thermal emissions from the Earth near the vicinity of the village of Al-Hindaw in Dakhla city, New Valley Governorate, Egypt. At the location of the fume exit area, magnetic, seismic, and electromagnetic geophysical investigations were carried out to identify the factor(s) responsible for the event in question. Rock samples were collected and studied geochemically and radiographically to assess their chemical compositions, as well as the quantity of organic chemicals that may have contributed to the burning and temperature increase. In light of the results of the geochemical and geophysical research, it is believed that the self-ignitions are the result of near-surface reactions and oxidation instead of volcanic activity, such as the presence of magma or other comparable phenomena. [ABSTRACT FROM AUTHOR]

The mechanism, temperature, and timescale of granite intrusion remain controversial, with wide-ranging implications for understanding continental growth, differentiation, rheology, and deformation dynamics. In this paper we present a method for determining intrusion emplacement temperature and timescale using the characteristics of the surrounding metamorphic aureole, and apply it to the Skiddaw granite in northern England. The estimated emplacement timescale (0.1–2 Myr) implies magma transport velocities of 1–100 mm/year. At the absent or low melt fractions relevant to our estimated emplacement temperature (580–650 ∘ C), such velocities are incompatible with pluton formation by successive injections through dykes. Instead, our results indicate the intrusion of a diapir of crystal-rich slurry, solidifying before emplacement, with a rheology governed by the solid crystals. The emplacement depth is likely to be governed by the depth-dependent rheology of the surrounding rocks, occurring close to the brittle-ductile transition. The wider implications of our results relate to (1) the appreciation that much of the chemical and textural characteristics of plutons may relate to pre-emplacement crystallisation at depth, passively transported to higher crustal levels, and (2) an explanation of the difficulty of seismically imaging active plutonism. [ABSTRACT FROM AUTHOR]

Geophysical data provide the chance to investigate a volcano's dynamics; considerable information can especially be gleaned on the stress and strain patterns accompanying the internal processes and the effect of magma ascent on the main structures triggering earthquakes. Here, we analysed in detail the seismicity recorded over the last two decades on Etna volcano (southern Italy), focusing on earthquakes distribution and focal mechanism clustering; the ground deformation pattern affecting the volcanic edifice with the inflation and deflation phases was also examined. Analysed data were compared in order to shed light on possible relationships with the volcanic activity and to better understand the internal dynamics of the volcano over time. Significant steps during or shortly before major eruptions in the seismic strain release and ground deformation temporal series highlight a straightforward relationship between seismicity occurring at shallow level, inflation/deflation and volcanism. Furthermore, at depths greater than 5–7 km, down to about 20 km, the orientation of the P- and T-axes clearly indicate the existence of a pressure source in the central part of the volcano. All the results underline that the stress field related to the volcano plumbing system interferes with the regional field, partly overriding it. [ABSTRACT FROM AUTHOR]

Lava fountains are a common manifestation of basaltic volcanism. While magma degassing plays a clear key role in their generation, the controls on their duration and intermittency are only partially understood, not least due to the challenges of measuring the most abundant gases, H2O and CO2. The 2021 Fagradalsfjall eruption in Iceland included a six-week episode of uncommonly periodic lava fountaining, featuring ~ 100–400 m high fountains lasting a few minutes followed by repose intervals of comparable duration. Exceptional conditions on 5 May 2021 permitted close-range (~300 m), highly time-resolved (every ~ 2 s) spectroscopic measurement of emitted gases during 16 fountain-repose cycles. The observed proportions of major and minor gas molecular species (including H2O, CO2, SO2, HCl, HF and CO) reveal a stage of CO2 degassing in the upper crust during magma ascent, followed by further gas-liquid separation at very shallow depths (~100 m). We explain the pulsatory lava fountaining as the result of pressure cycles within a shallow magma-filled cavity. The degassing at Fagradalsfjall and our explanatory model throw light on the wide spectrum of terrestrial lava fountaining and the subsurface cavities associated with basaltic vents. This study of volcanic gas chemistry during pulsatory lava fountaining at Fagradalsfjall volcano in Iceland reveals that the intermittency stems from pressure cycles and gas-melt separation within a shallow magma-filled cavity. [ABSTRACT FROM AUTHOR]

Changbaishan Volcano is considered one of the most hazardous active volcanic fields in northeastern Asia, and it has been the subject of increasing concern due to its unrest from 2002 to 2006. The physical conditions of magma chambers in the crust, particularly temperature and pressure, are crucial factors that determine the tempo and magnitude of volcanic eruptions, which are closely linked to potential hazards. However, the lithospheric thermal structure, which strongly influences rheological behaviour and melting, has been poorly studied. We conducted direct geothermal measurements and numerical forward modelling to address this issue to confirm whether a crustal magma chamber lies beneath the caldera as in earlier geophysical interpretations. We first reported four heat-flow data sets in Changbaishan Volcano. The research findings indicate that the heat flow value near the Tianchi caldera is remarkably high, at 270±16 mW m−2. As the distance from the caldera increases, the heat flow gradually decreases to a normal continental heat flow value of 75 mW m−2. 3-D transient heat simulations with a magma cooling model and a continuous magma supply model demonstrate the thermal effect of the magma chamber. The best-fitting model for the Tianchi magma system is an ellipsoidal magma chamber with a depth of 8–14 km, a 20 km east–west axis and a 70 km north–south axis, supplied with magma from the asthenosphere for 2 Myr. The high surface heat flow and crustal temperatures suggest that magma is active beneath Changbaishan Volcano within the middle-upper crust, and volcanic reactivation could occur. Thus, further research on the lithospheric thermal structure is necessary to understand the potential volcanic hazards associated with Changbaishan Volcano. [ABSTRACT FROM AUTHOR]

The Dar al Gani (DaG) olivine‐phyric shergottites share mineralogical and geochemical characteristics, which confirm that these meteorites are derived from a single source. Bulk trace elements (La/Yb—0.12), in situ maskelynite 87Sr/86Sr (~0.7014) and redox estimates (FMQ ~ −2) indicate derivation from a depleted, reduced mantle reservoir; identical to all ~470 Ma shergottites ejected at 1.1 Ma. The DaG shergottites have been variably affected by terrestrial alteration, which precipitated carbonate along fractures and modified bulk‐rock fluid mobile (e.g., Ba) elements. Nonetheless, sufficient data are available to construct a multi‐stage formation model for the DaG shergottites and other 1.1 Ma ejection‐paired shergottites that erupted at ~470 Ma. First, partial melting of a depleted mantle source occurred at 1540 ± 20°C and 1.2 ± 0.1 GPa, equivalent to > ~100 km depth. Then, initial crystallization in a staging chamber at ~85 km depth at the crust–mantle boundary took place, followed by magma evolution and variable incorporation of antecrystic olivine ± orthopyroxene. Subsequently, crystallization of olivine phenocrysts and re‐equilibration of olivine antecrysts occurred within an ascending magma. Finally, magmas with variable crystal loads erupted at the surface, where varied cooling rates produced a range of groundmass textures. This model is similar to picritic flood basalt magmas erupted on Earth. [ABSTRACT FROM AUTHOR]

Here we report the composition of biotite from the peraluminous Devonian South Mountain Batholith (SMB) of southwestern Nova Scotia (Canada), the largest intrusive body within the Appalachian orogen. The batholith was emplaced in two phases: an early (379–375 Ma) granodiorite-monzogranite suite (Stage 1) and a later (375–372 Ma) more-evolved monzogranite-leucogranite suite (Stage 2). Biotite analyses (major and minor elements) were obtained on 55 unmineralized samples representing 11 plutons. Regardless of the stage of pluton emplacement, biotite is commonly interstitial to alkali feldspar, quartz and plagioclase, indicating similar timing of biotite saturation. This suggests that biotite chemistry records conditions at similar extents of magma evolution for the chosen suite of samples. Biotite compositions are Fe-rich, with Fe/(Fe+Mg) ranging from 0.6 to 0.98, and Al-rich, with IVAl ranging from 2.2 to 2.9 atoms per formula unit (apfu; 22 oxygen basis), the latter reflecting the coexistence of other Al-rich phases, such as muscovite, garnet, aluminosilicates, and cordierite. Biotite anion sites are dominated by OH (>3 apfu), followed by F (~0.3 apfu) and Cl (≤0.02 apfu), with a general trend of decreasing OH, increasing F and a marked decrease in Cl, with increasing differentiation. Pressure (P) is estimated from the Al content of biotite to be between 280–430 MPa, consistent with a range of 240 to <470 MPa derived from phase equilibria and fluid inclusion microthermometry combined with mineral thermobarometry. Temperature (T) calculated from the Ti content of biotite ranges from 603–722 °C. Comparison of P-T estimates with water-saturated granite phase relations suggest minimum water contents of 6–7 wt% for the SMB magmas. The redox state of the SMB was estimated by comparing biotite Fe#-Ti relations with compositions calculated using the MELTS thermodynamic model, as experiments have shown that biotite Fe# increases with decreasing fO2 at a given extent of crystallization. Results of MELTS modeling for the most primitive magmas of the SMB sample suite indicate that the observed biotite Fe#-Ti variation is consistent with crystallization at FMQ to FMQ-1, with more oxidizing conditions suggested for the most strongly differentiated samples. To constrain the origin of the biotite anion site variation, a quantitative model using biotite-melt exchange coefficients (KD) derived from existing experimental data was used to track the change in biotite OH-F-Cl abundances as a function of crystallization, with or without an extant magmatic vapor phase (MVP). The model reproduces the relative OH, F, and Cl abundances in biotite, and suggests that SMB crystallization occurred in the presence of a MVP. The relatively reduced redox state of the SMB, similar to other peraluminous granitoid occurrences worldwide, aligns with other measures of fO2 for the SMB, including the occurrence of primary ilmenite. The observed correspondence between the estimated fO2 and that imposed by graphite-gas equilibrium suggests a role for reduced carbon in the generation and evolution of the SMB. This is consistent with evidence for SMB interaction with graphite-bearing felsic granulites of the underthrust Avalon terrane, and assimilation of carbonaceous and sulfidic metasediments during pluton ascent and emplacement. Reducing conditions and development of a MVP have implications for granophile element concentration processes in the SMB magmatic system. Low fO2 during crystallization affects the mineral/melt partitioning and solubility of the redox-sensitive elements Sn, W, U, and Mo, serving to suppress early SnO2 precipitation, and cause both an increase in W/Mo and an overall buildup of all four elements in evolving SMB liquids. Available experimental data indicate that reducing conditions also shifts DMVP/melt to favor partitioning into the melt phase. Therefore, early vapor exsolution under reducing conditions also lessens the extraction efficiency of these redox-sensitive elements to the MVP, further underscoring the role of extensive crystallization as an important metal enrichment process. [ABSTRACT FROM AUTHOR]

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The paper presents the first SIMS SHRIMP U-Pb data for zircon from an olivine horizon within the Nyud intrusion of the ore-bearing layered Monchegorsk pluton (Monchepluton) in the Kola Region, Russia. A 100–150 m-thick olivine horizon occurs nearly horizontally between the melanocratic and mesocratic norite of the Nyud intrusion, which disturbs its normal cumulus stratigraphic sequence. In addition, the pyroxene-plagioclase hornfelses are present at the upper contact with the olivine horizon. Twenty-three zircon grains were extracted from the large-volume olivine plagio-orthopyroxenite sample and clustered into two populations. The first population of magmatic zircon (n = 8) has a concordant and weighted average 207Pb/206Pb age of 2484.3 ± 5.6 Ma, which characterizes the formation time of the olivine horizon rocks. This serves as evidence of the olivine horizon that forms as a result of additional magma injection, which does not contradict the geological data. The 207Pb/206Pb age of single-grain zircon is 2414 ± 25 Ma, which indicates the time of postmagmatic transformations. The second population of zircon (n = 16) has a concordant and weighted average U-Pb age of 2700.6 ± 4.6 Ma, which indicates zircon absorption by olivine horizon magma probably from the rocks of the Archean greenstone belt. [ABSTRACT FROM AUTHOR]

Mount Somma–Vesuvius is a stratovolcano that represents a geological hazard to the population of the city of Naples and surrounding towns in southern Italy. Historically, volcanic eruptions at Mt. Somma–Vesuvius (SV) include high-magnitude Plinian eruptions, such as the infamous 79 CE eruption that occurred after 295 years of quiescence and killed thousands of people in Pompeii and surrounding towns and villages. The last eruption at SV was in 1944 and showed a Volcanic Explosivity Index (VEI) of 3 (0.01 km 3 of volcanic material erupted). Following the 1944 eruption, SV has been dormant for the past nearly 79 years, with only minor fumarolic and seismic activity. During its long history, centuries of dormancy at SV have ended with Plinian eruptions (VEI 6) that signal the beginning of a new cycle of eruptive activity. Thus, the current dormancy stage demands a need to better understand the mechanism involved in high-magnitude eruptions in order to better predict future eruption magnitude and style. Despite centuries of research on the SV volcanic system, many questions remain, including the evolution of magmatic volatiles from deep primitive magmas to shallower more evolved magmas. Developing a better understanding of the physical and chemical processes associated with volatile evolution at SV can provide insights into magma dynamics and the mechanisms that trigger highly explosive eruptions at SV. In this study, we present new data for the pre-eruptive volatile contents of magmas associated with four Plinian and two inter-Plinian eruptions at SV based on analyses of reheated melt inclusions (MIs) hosted in olivine. We correct the volatile contents of bubble-bearing MIs by taking into account the volatile contents of bubbles in the MIs. We recognize two groups of MIs: one group hosted in high-Fo olivine (Fo 85–90) and relatively rich in volatiles and the other group hosted in low-Fo olivine (Fo 70–69) and relatively depleted in volatiles. The correlation between volatile contents and compositions of host olivines suggests that magma fractionation took place under volatile-saturated conditions and that more differentiated magmas reside at shallower levels relative to less evolved/quasi-primitive magmas. Using the CO 2 contents of corrected MIs hosted in Fo 90 olivine from SV, we estimate that 347 to 686 t d -1 of magmatic CO 2 exsolved from SV magmas during the last 3 centuries (38–75 Mt in total) of volcanic activity. Although this study is limited to only few SV magmas, we suggest that further study applying similar methods could shed light on the apparent lack of correlation between the volatile contents of MIs and the style and age of eruptions. Further, such studies could provide additional constraints on the origin of CO 2 and the interaction between the carbonate platform and ascending magmas below SV. [ABSTRACT FROM AUTHOR]

The iconic volcanoes of the Cascade arc stretch from Lassen Volcanic Center in northern California, through Oregon and Washington, to the Garibaldi Volcanic Belt in British Columbia. Recent studies have reviewed differences in the distribution and eruptive volumes of vents, as well as variations in geochemical compositions and heat flux along strike (amongst other characteristics). We investigate whether these along-arc trends manifest as variations in magma storage conditions. We compile available constraints on magma storage depths from InSAR, geodetics, seismic inversions, and magnetotellurics for each major edifice and compare these to melt inclusion saturation pressures, pressures calculated using mineral-only barometers, and constraints from experimental petrology. The availability of magma storage depth estimates varies greatly along the arc, with abundant geochemical and geophysical data available for some systems (e.g., Lassen Volcanic Center, Mount St. Helens) and very limited data available for other volcanoes, including many which are classified as "very high threat" by the USGS (e.g., Glacier Peak, Mount Baker, Mount Hood, Three Sisters). Acknowledging the limitations of data availability and the large uncertainties associated with certain methods, available data are indicative of magma storage within the upper 15 km of the crust (~2 ± 2 kbar) beneath the main edifices. These findings are consistent with previous work recognizing barometric estimates cluster within the upper crust in many arcs worldwide. There are no clear offsets in magma storage between arc segments that are in extension, transtension or compression, although substantially more petrological work is needed for fine scale evaluation of storage pressures. [ABSTRACT FROM AUTHOR]

In the Mississippian Matachel small volcanic field of the Ossa-Morena Zone (southern Iberian Massif) outpoured basic-intermediate lavas exhibit geochemical characteristics of Low-Ti continental tholeiites and calc-alkaline lavas. Low-Ti continental tholeiites integrate two contrasting groups of rocks: basalts (Mg#: 54 to 70; Ti/Zr: 61-79; LaN/LuN: 1.6-2.9; εNdi: +4.0-+6.6; "Group #1"), and basalts and basaltic andesites (Mg#: 43 to 66; Ti/Zr: 36-58; LaN/LuN: 2.5-5.9; εNdi: -0.2-+3.5; "Group #2"). Primitive Group #1 tholeiitic magmas were generated by partial melting of a garnet-free lherzolite from an enriched lithospheric mantle, near the lithosphere-asthenosphere thermal boundary layer (with a very limited asthenosphere melting input). Progressive interaction of these magmas with crustal alkali igneous rocks resulted in the formation of the petrological evolutionary trends observed, to a larger extent in the case of Group #2 Low-Ti tholeiites. Further assimilation of amphibole-rich calc-alkaline metaigneous rocks might have originated the basalts and basaltic andesites with calc-alkaline signature (Mg#: 33 to 56; Ti/Zr: 25-78; LaN/LuN: 2.0-5.6; εNdi: +2.8-+4.8). These exhibit a "Cordilleran-type" evolutionary trend, though are unrelated to plate convergence. The magmas with calc-alkaline signature attest to a closed-system differentiation process controlled by the fractionation of plagioclase, clinopyroxene, magnetite and ilmenite. It is proposed that Mississippian lithospheric-scale intra-continental wrenching, unrelated to coeval mantle plume upwelling, reworked complexly docked mantle domains and triggered mantle melting. Enduring mid-upper crustal processes (magma storage in mid-crustal chambers and crustal assimilation) likely shaped the latest petrologic and geochemical aspects of the Matachel Low-Ti tholeiites and related rocks with calc-alkaline signature. [ABSTRACT FROM AUTHOR]

Surface deformation plays a key role in illuminating magma transport at active volcanoes, however, unambiguous separation of deep and shallow transport remains elusive. The Socorro Magma Body (SMB) lacks an upper crustal magma transport system, allowing us to link geodetic measurements with predictions of numerical models investigating rheologic heterogeneities and magma‐mush interaction in the mid‐/lower crust. New InSAR observations confirm that a pattern of central surface uplift surrounded by a region of subsidence (previously coined "sombrero" deformation) has persisted over >100 years at the SMB. Our models suggest this pattern may reflect the presence of a large (>100 km width), weaker‐than‐ambient, compliant region (CR) surrounding the mid‐crustal magma body. Interactions between a pressurizing (e.g., due to melt injection and/or volatile exsolution) sill‐like magma body and CR drive the sombrero pattern, depending on both viscoelastic relaxation and pressurization timescales, explaining its rare observation and transient nature. Plain Language Summary: Magma in the crust is transported and stored within magma bodies (regions that are mostly liquid magma) and "mush" (mostly solid crystals and some liquid magma). Mush zones are thought to be too viscous to be erupted but are likely to be weaker than the surrounding rock. To understand volcanic eruptions, it is important to understand the distribution of magma and mush, and their mutual interactions. Here we study these interactions in a mid‐crustal magma body, the Soccorro Magma Body (SMB), that does not have a surface volcano. Surface deformation at the SMB helps us study magma‐mush interaction, especially in the middle or lower crust. Previous surface deformation measurements at the SMB show "sombrero" deformation: a central area of uplift surrounded by a ring of subsidence. New satellite radar measurements are consistent with the previously reported pattern, confirming that this deformation remained remarkably constant through nearly 100 years. We suggest this is due to a large weak, mush region surrounding the SMB. Our computer models reproduce a long‐lasting, consistent sombrero deformation pattern depending on mush properties as well as pressurization history of the magma body, and we suggest these factors may explain why this pattern is relatively rare. Key Points: InSAR confirms coeval subsidence and uplift (a so‐called "sombrero" deformation pattern) persisted for >100 years at the Socorro Magma Body (SMB)A compliant region, modeled as a viscoelastic body surrounding a sill, is able to reproduce both the pattern and duration of deformationViscoelastic deformation within a broad compliant region supports the presence of mush zones at SMB and other mid‐crustal magma bodies [ABSTRACT FROM AUTHOR]

Modelling magma transport requires robust numerical schemes for chemical advection. Current numerical schemes vary in their ability to be mass conservative, computationally efficient, and accurate. This study compares four of the most commonly used numerical schemes for advection: an upwind scheme, a weighted essentially non-oscillatory (WENO-5) scheme, a semi-Lagrangian (SL) scheme, and a marker-in-cell (MIC) method. We assess the behaviour of these schemes using the passive advection of two different magmatic compositions. This is coupled in 2D with the temporal evolution of a melt anomaly that generates porosity waves. All algorithms, except the upwind scheme, are able to predict the melt composition with reasonable accuracy. In terms of total running time, the upwind and SL schemes are the fastest, and the MIC scheme is the slowest. The WENO-5 scheme shows intermediate total running time but has the lowest amount of mass loss and therefore is best suited for this problem. [ABSTRACT FROM AUTHOR]

The article focuses on geophysical characterization of the Long Valley Caldera's magma chamber in California, U.S. Topics discussed include the separation between the shallow hydrothermal system and the deeper magma chamber, with the uplift and seismicity driven by fluids exsolved through second boiling.

The Aira caldera, located in southern Kyushu, Japan, originally formed 100 ka, and its current shape reflects the more recent 30 ka caldera-forming eruptions (hereafter, called the AT eruptions). This study aimed to delineate the detailed two-dimensional (2D) seismic velocity structure of the Aira caldera down to approximately 15 km, by means of the travel-time tomography analysis of the seismic profile across the caldera acquired in 2017 and 2018. A substantial structural difference in thickness in the subsurface low-velocity areas in the Aira caldera between the eastern and western sides, suggest that the Aira caldera comprises at least two calderas, identified as the AT and Wakamiko calderas. The most interesting feature of the caldera structure is the existence of a substantial high-velocity zone (HVZ) with a velocity of more than 6.8 km/s at depths of about 6–11 km beneath the central area of the AT caldera. Because no high ratio of P- to S-wave velocity zones in the depth range were detected from the previous three-dimensional velocity model beneath the AT caldera region, we infer that the HVZ is not an active magma reservoir but comprises a solidified and cool remnant. In addition, a poorly resolved low-velocity zone around 15 km in depth suggests the existence of a deep active magma reservoir. By superimposing the distribution of the known pressure sources derived from the observed ground inflation and the volcanic earthquake distribution onto the 2D velocity model, the magma transportation path in the crust was imaged. This image suggested that the HVZ plays an important role in magma transportation in the upper crust. Moreover, we estimated that the AT magma reservoir in the 30 ka Aira caldera-forming eruptions has the total volume of 490 km3 DRE and is distributed in a depth range of 4–11 km. [ABSTRACT FROM AUTHOR]

The article analyzes the response to the climate crisis and its responsibility, highlighting Pope Francis' apostolic exhortation Laudate Deum. The Pope warns about the anthropogenic nature of the catastrophe and criticizes countries and economic powers that seek to profit at the expense of the most vulnerable. Additionally, the importance of recognizing the interrelation between the human and the non-human is mentioned, and a paradigm shift based on care, attention, and humility is proposed. On the other hand, the article presents an artwork called "Tectonic Movements" that visually represents tectonic movements and the interaction between the mantle, the crust, and the magma. The painting invites reflection on the dynamics of the Earth and its influence on the formation of landscapes and natural phenomena. [Extracted from the article]

A suite of subduction-related early Triassic igneous rocks crops out in the Pingxiang area of the DianQiong suture (DQS) in southwest China; this suite represents an important geological record of subduction and closure of the Paleo-Tethys Ocean. In this study, we report geochronological, geochemical, and NdHf isotope data for newly discovered rhyolites and biotite granites in the Pingxiang area. We use these data to constrain their emplacement ages, origins, and geodynamic implications. Zircon U-Pb dating indicates that the rhyolites and biotite granites were emplaced at 251–250 Ma and 249 Ma (early Triassic), respectively. The rhyolites and biotite granites have elevated FeOT/(FeOT + MgO) (0.78–0.89) and 10,000 × Ga/Al (2.83–4.11) ratios, with geochemical affinities to A2-type granites. These rocks are enriched in some large-ion lithophile elements (e.g., Rb, Th, and Ba) and depleted in high-field-strength elements (e.g., Nb, Ta, and Ti), indicating their formation in a subduction-related arc. The rhyolites and biotite granites have negative whole-rock εNd(t) (−11.5 to −9.7) and zircon εHf(t) (−14.5 to −6.2) values, suggesting that these magmas were derived from an ancient crust-dominated source. Geochemical and Nd isotope data reveal that the peraluminous A2-type rhyolites and biotite granites were derived by partial melting of felsic crustal rocks under low-pressure and high-temperature conditions. By integrating all the available data with the regional tectonic evolution of the southwestern Youjiang Basin and adjacent regions, we attribute the generation of the peraluminous A2-type rhyolites and biotite granites to the extensional setting that existed during oceanic subduction, which was induced by roll-back of the Paleo-Tethys oceanic lithosphere at 251–249 Ma. This study indicates that subduction-related magmatism related to Paleo-Tethys oceanic lithosphere was still active in the early Triassic. [ABSTRACT FROM AUTHOR]

The 2011–2012 eruption at Cordón Caulle in Chile produced crystal-poor rhyolitic magma with crystal-rich mafic enclaves whose interstitial glass is of identical composition to the host rhyolite. Eruptible rhyolites are thought to be genetically associated with crystal-rich magma mushes, and the enclaves within the Cordón Caulle rhyolite support the existence of a magma mush from which the erupted magma was derived. Moreover, towards the end of the 2011–2012 eruption, subsidence gave way to inflation that has on average been continuous through at least 2020. We hypothesize that magma segregation from a crystal mush could be the source of the observed inflation. Conceptually, magma withdrawal from a crystal-poor rhyolite reservoir caused its depressurization, which could have led to upward flow of interstitial melt within an underlying crystal mush, causing a new batch of magma to segregate and partially recharge the crystal-poor rhyolite body. Because the compressibility of the crystalline matrix of the mush is expected to be lower than that of the interstitial melt, which likely contains some fraction of volatile bubbles, this redistribution of melt would result in a net increase in volume of the system and in the observed inflation. We use numerical modelling of subsurface magma flow and storage to show under which conditions such a scenario is supported by geodetic and petrologic observations. [ABSTRACT FROM AUTHOR]

The Yalguba Ridge volcanic rocks form part of the Middle Paleoproterozoic (ca. 1.97 Ga) volcano-sedimentary sequence within the Karelian Craton in the Fennoscandian Shield. Yalguba variolitic textures are known worldwide and have been previously considered to originate from liquid immiscibility. The present study reveals two new variolite types recognized in the Yalguba sequence: (1) Variolites with unzoned varioles have distinct chemical and mineralogical compositions of varioles and matrix that support an origin by liquid immiscibility. They were recognized in quenched zones of pillows, so it might be assumed that melt separation caused by liquid immiscibility occurred before magma emplacement. The difference from the previously described variolites lies in the variole microtexture and might be caused by the various cooling conditions. (2) Spherulitic variolites have varioles composed of andesine–oligoclase spherulites embedded in the cryptocrystalline matrix with oligoclase–anorthoclase composition, thus the variole and matrix have similar chemical and mineralogical composition. The mineralogical and textural features of these variolites suggest that the spherulites have a primary magmatic origin due to the rapid cooling of superheated magma. The variety of variolitic textures in the Yalguba section might be caused by the different H2O saturation of parental magma and cooling conditions. [ABSTRACT FROM AUTHOR]

The Middle Paleoproterozoic (1.99 Ga) Tiksheozero ultramafic‒alkaline‒carbonatite complex in Northern Karelia is one of the Earth's oldest alkaline complexes. The major and trace-element compositions of minerals were used to decipher the genetic relations between ultramafic cumulates, alkaline rocks, and carbonatites. Based on detailed analysis of clinopyroxenes from ultramafic cumulates, it was assumed that they were derived from an alkaline melt. It was estimated that ultramafic cumulates and alkaline rocks were formed at close moderate pressure, which in combination with the above facts, is consistent with their cogenetic origin. The REE patterns of clinopyroxenes are characterized by the high LREE/HREE fractionation, with slightly convex-upward LREE patterns (La/Nd < 1), which are typical of deep-seated cumulates formed in an equilibrium with an alkaline basaltic melt. Two types of REE zoning were distinguished in apatite using cathodoluminescence imaging. The first type with an outward LREE decrease was found in apatite from silicate rocks of the complex and was likely produced by the closed-system overgrowth of apatite from a residual melt at the late magmatic stage. In contrast, apatite from carbonatite is characterized by a slight outward LREE increase, which is likely related to the re-equilibration of apatite with fresh batches of REE-enriched carbonatite magma. Precipitation of monazite along fractures and margins of apatite in complex with essential HREE and Y enrichment observed in syenite is indicative of the metasomatic interaction of this rock with fluid. Apatites from alkaline rocks and carbonatites define a common trend in the Y–Ho diagram, with a decrease in the Y/Ho ratio from foidolites to carbonatites. This fact together with the absence of signs of liquid immiscibility, and compositional variations in apatite in silicate rocks and carbonatites, are consistent with their origin through fractional crystallization rather than liquid immiscibility. [ABSTRACT FROM AUTHOR]

The origin of giant rare earth element (REE)‐rich phosphorus deposits related to ultramafic rocks is unclear. To characterize the genetic linkage between ultramafic rocks and P–REE mineralization, we investigated the whole‐rock geochemistry, geochronology and Hf isotopic compositions, along with previously published data of barren and ore‐bearing clinopyroxenites from the giant Shangzhuang REE‐rich apatite deposit (containing about 51.1 million tonnes of P2O5 and 157,400 tonnes of REEs) in the Lajishan suture, Western China. The P–REE ores and barren biotite clinopyroxenites are composed predominantly of clinopyroxene and biotite, with high levels of apatite, amphibole, allanite, sulfide and oxide minerals in the ore‐bearing samples. Zircon and allanite U–Pb ages for the barren and ore‐bearing clinopyroxenites indicate they were formed between 467 and 465 Ma. The barren and ore‐bearing samples are characterized by high CaO and low SiO2 contents, as well as similar Hf isotope ratios (εHf[t]: +3.4 to +7.7), indicating that they represent an ultramafic magma system and have been derived from a similar source. They are enriched in light REEs and depleted in Nb–Ta–Zr–Hf–Ti, similar to arc‐related lavas found worldwide. The weakly evolved barren samples have high Ba/La, Rb/Y and Dy/Yb values, and their ages are coeval with calc‐alkaline granitic plutons in the belt, which postdate the formation of the Lajishan ophiolite by ~30 myr. This suggests that the primary magma originated from garnet peridotite mantle modified by subducted Proto‐Tethys oceanic crust‐derived fluids in an arc setting. The presence of apatite intergrowth with cumulus clinopyroxene without alteration features indicates that the deposit has a magmatic origin. The ore‐bearing clinopyroxenite contains higher contents of P, REEs, and high‐field‐strength elements than the barren clinopyroxenite, which could be attributed to the in situ accumulation of apatite and allanite in the residual magma. Thus, the formation of the P‐dominated orebodies results from phosphate saturation due to the extensive fractionation crystallization of clinopyroxene and biotite during magmatic evolution. REEs were primarily enriched in the late‐stage melt, which was compatible with apatite and allanite. We propose that the formation of the Shangzhuang REE‐rich apatite deposit can be attributed to a simple differentiation of ultramafic melts in an evolved magmatic system. [ABSTRACT FROM AUTHOR]

Fractionation of sulfides during ascent of mantle-derived magmas distributes sulfur and chalcophile elements into the Earth's lithosphere. It has been suggested that continental intraplate alkaline magmas undergo early sulfide saturation. However, there is a lack of evidence linking erupted magmas to their cumulative counterparts. We examined the petrography and chalcophile and platinum group element (PGE) geochemistry of sodic and potassic differentiation lineage lavas and cumulate autoliths from The Pleiades, an intraplate alkaline volcanic field in northern Victoria Land, Antarctica. The presence of sulfide minerals and depleted PGE contents in mafic lavas show they were saturated in sulfide from the initial stages of magma differentiation. The sodic lineage lavas and their kaersutite gabbro autoliths have abundant sulfides associated with fractionation of titanomagnetite and kaersutite. Their presence is consistent with the chalcophile element geochemistry of the lavas. In the potassic lineage lavas, petrography of autoliths indicates that the sulfides are more abundant in kaersutite diorite than wehrlite, olivine essexite, olivine diorite, and syenite autoliths. Kaersutite is not a phenocryst phase in the potassic lineage but crystallized via in situ replacement of the precursor olivine and augite. During the kaersutite formation, sulfides were precipitated from the interstitial silicate melt. The melt was sulfide oversaturated due to temperature decrease, and compositional variations (mainly SiO2, ΣFeO, Fe3+/ΣFe ratio). The mantle-like isotope compositions of Cu, Zn, and S in the potassic lineage confirms a magmatic origin of the sulfides. The magmatic sulfides from The Pleiades are characterized by depleted PGE, Au and Cu contents. Fractional crystallization models show that early sulfide saturation led to impoverishment of chalcophile metals in The Pleiades magmatic system. This phenomenon may be common in continental intraplate alkaline magmas ascending through thick crusts. [ABSTRACT FROM AUTHOR]

We would like to thank Geist et al. (Contrib Miner Petrol, 2023) for the opportunity to further discuss the arguments presented in our paper "Long or short silicic magma residence time beneath Hekla volcano, Iceland?" (Sigmarsson et al. Contrib Miner Petrol 177:13, 2022). The disagreement centers around the origin of the silicic magmas at Hekla, namely whether it is by (1) fractional crystallization and a long crustal residence time before eruption or (2) partial melting of altered basaltic crust and short transfer time to the surface. We disagree with the arguments presented by Geist et al. (Contrib Miner Petrol, 2023) against the model for the origin of dacite at Hekla from dehydration melting of amphibolite, a model that still explains most if not all results obtained so far on the Hekla magma suite. [ABSTRACT FROM AUTHOR]

Recently reported major element, trace element, and volatile compositions of dacites erupted from Hekla Volcano, Iceland are inconsistent with an anatectic origin. In contrast, all of the data are consistent with dacitic melts being derived by modest amounts of crystallization of an anhydrous assemblage from an andesitic melt. Models that apply straightforward Gd, Yb, Th, and U concentrations, instead of ratios, to the problem show that the crystallization hypothesis remains valid, especially when uncertainties are propagated. [ABSTRACT FROM AUTHOR]

The Regional Natural Park of the Monts d'Ardèche, located in south-eastern France, became the Monts d’Ardèche UNESCO Global Geopark in September 2014. This territory possesses significant volcanic features dating from the Miocene to the late Pleistocene. The UNESCO Global Geopark label helped to formalize a long-standing partnership with the University of Clermont Auvergne which includes support for scientific research, establishing conservation and protection priorities, establishing geosites for the public and involvement of local people and communities in geotouristic initiatives. Here we focus on some peculiar geosites that allow us to question magmatic processes, eruptive dynamics, morphological evolution of landscapes, the chronology of eruptions, relationships between humans and volcanoes during the Pleistocene, and highlight the delicate alliance between economic pressures, heritage conservation, and scientific tourism.