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Eruptive dynamics is influenced by gas escape from the ascending magma. Gas pathways form in the magma via bubble coalescence, leading to gas channeling. Magmatic crystals play a key role in gas channel formation. This work constrains experimentally decompression‐induced coalescence in high‐crystallinity silicic magmas without external deformation, focusing on low gas content and bimodal crystal size (microlites and phenocrysts). All percolating samples have permeabilities of 10−14 m2 at bulk porosities of 7–10 vol% and bulk crystallinities up to 75 vol%. Our results demonstrate the possibility of coalescence‐related outgassing at high pressure (120–350 MPa) and without external strain, which corresponds to magma stagnating deep in a volcanic conduit. Channeling at such low gas content implies that bimodal crystallinity favors effusive over explosive volcanic behavior. It may also be the missing physical mechanism explaining gas transfer across magmatic systems despite high melt viscosity and low or absent magma extrusion. Plain Language Summary: The way volcanoes erupt is mainly controlled by the ability of gases to escape from the magma (outgassing). An efficient way to outgas is to connect bubbles together (coalescence) up to the point where channels form in the magma (channeling) in which gas can circulate toward the surface. We investigate experimentally how coalescence and channeling happen in immobile, crystal‐rich viscous magma in conditions (pressure and temperature) similar to those found in deep volcanic conduit, where only a small amount of gas (<10%) is present. Our experiments demonstrate that bubble connections are possible thanks to a large amount of crystals on which bubbles can lean, deform, and join each other. That gas can escape from magma at depth could favor effusive eruption over volcanic explosions and even bring new insights on degassing in immobile magma. Key Points: Gas permeability in silicic magma is possible with gas volumes below 10% thanks to high crystallinityOutgassing at low gas content can happen without external deformation nor fracturation of the magmaVolcanic outgassing in stagnant magmas is explained by deep conduit bubble channeling that may be a key mechanism in eruptive transition [ABSTRACT FROM AUTHOR]

The relative contributions of asthenospheric mantle, lithospheric mantle, and continental crust in the genesis of the Siberian Traps Large Igneous Province (ST-LIP) remain poorly constrained. Most models invoke partial melting of asthenospheric mantle within a mantle plume with an inventory of recycled crustal material, with or without melting of subcontinental lithospheric mantle, and crustal contamination during ascend through the continental lithosphere. A greater understanding of this topic is of fundamental importance because the ST-LIP basalts are associated with the large Permian-Triassic extinction and the world's largest magmatic Ni-Cu-platinum group element sulfide resources (Ni-Cu-PGE), the Norilsk-Talnakh mining camp. The ∼250 ± 2 Ma Siberian Traps at Norilsk contain a classic sequence of basaltic rocks that provide a spatial and stratigraphic context for changing chemistry of the eruptive products. We present a detailed geochemical and Sr-Nd-Hf-Mo isotopic investigation of ST-LIP volcanic rocks and associated sedimentary rocks, including coal and anhydrite, from the Norilsk area. The 98Mo/95Mo isotope ratios (reported as δ98Mo ratio relative to NIST SRM 3134) vary significantly from −0.62 to 0.07 ‰ for the older basalt formations and −0.41 to 0.03 ‰ for the younger basalt formations. The range of δ98Mo and its correlation with the other geochemical tracers cannot be explained by post-magmatic alteration, magmatic differentiation, or sulfide fractionation as Mo behaves as a lithophile element under these magmatic conditions. We suggest that the δ98Mo range can be explained by interaction of the plume with subcontinental lithospheric mantle modified by subduction processes. This is particularly prominent in the earlier Ivakinsky to Gudchikhinsky formations where light δ98Mo values coupled with low Mo/Ce can be explained by contributions from a dehydrated eclogitic component, whereas more rare heavy δ98Mo values and high Mo/Ce likely require contributions from a fluid metasomatized mantle source. Later magmas of the Nadezhdinsky formation show clear evidence of crustal contamination in their combined Mo-Sr-Nd-Hf isotope and trace element systematics, while the later more voluminous Morongovsky type magmas are shallower, large degree melts with limited crustal interaction. Our data shows the usefulness of Mo isotopes in deciphering magma sources of large igneous provinces eruptions. [ABSTRACT FROM AUTHOR]

Continental subduction is the major cause of regional heterogeneities in the lithospheric mantle and contrasting types of magmatism and mineralization in post-collisional settings. We illustrate the relation between the nature of the subducted crust and the character of magmatism for the Late Miocene New Guinea Orogen that formed by the collision of the Australian continental margin with an island arc. The bipartite nature of the subducted Australian plate margin, with Precambrian crust in the west and Phanerozoic accreted arcs in the east, is reflected in the contrasting magmatism along the strike of the New Guinea Orogen. The chemical signature of the subducted crust is particularly prominent in small-volume Late Miocene–Quaternary ultrapotassic rocks of New Guinea. In the west, ultrapotassic lavas have low εNd values (−12.6 to −20.9), indicating the recycling of ancient continental material. Conversely, high εNd values of +3.5 to +4.5 are found in ultrapotassic lavas from eastern New Guinea. This suggests recycling of juvenile continental material, similar to the orthogneisses exposed in the Late Miocene ultrahigh-pressure metamorphic complex of the D'Entrecasteaux Islands. By comparison with ultrapotassic rocks from other orogenic belts, we show that crustal recycling is responsible for regionally contrasting redox conditions in the lithospheric mantle, which may explain why porphyry-type deposits are important in some regions but absent in others. [ABSTRACT FROM AUTHOR]

Nakhlite and chassignite meteorites are cumulate rocks thought to originate from the same location on Mars. Petrogenetic relationships between nakhlites and chassignites are not fully constrained, and the two cumulus phases in nakhlites—olivine and clinopyroxene—possibly formed either together from one magma or separately from different magmas. Primary magma compositions can potentially be determined from studies of melt inclusions (MIs) trapped within early‐formed mineral phases. MIs frequently undergo post‐entrapment effects, and when such processes occur, there can be significant changes to their compositions. Here, we report major, minor, and trace element abundances for MIs in cumulus phases in nakhlites and chassignites. The melt compositions that they record are variable (MgO = 2.50–13.5 wt%, K2O = 0.03–3.03 wt%, La/Yb = 2.46%–16.4%) and are likely affected by diffusive reequilibration with changing magma composition outside of their host phases. Evidence for diffusive reequilibration suggests that nakhlite and chassignite magmas were generated in an open system, and cumulus phases may have undergone magma storage and mixing. Such processes may be akin to those that occur in terrestrial intrusive magmatic systems by open‐system magma recharge. MIs within the nakhlite and chassignite suite therefore provide insights into magmatic processes during magma storage and transit on Mars. [ABSTRACT FROM AUTHOR]

The crystal‐poor rhyolitic pumice is the product of extreme magma differentiation and is characterized by highly vesicular, honeycomb‐like structure. However, little is known about the evolutionary history and the time of volatile saturation of the pumice‐forming melt. A crystal‐poor rhyolitic pumice (TVG7‐1) has been collected from the Yoron Hole hydrothermal field in the middle Okinawa Trough, a young continental margin back‐arc basin in the western Pacific. This study conducted a detailed analysis on the texture and in situ chemical composition of plagioclase, orthopyroxene and Fe‐Ti oxides to reveal the evolution process, storage state and eruption triggers of eruptible silicic melt. Texture and zoning of specific minerals and mineral populations suggest a magmatic evolution history of open system. Additionally, the hollow reentrant texture, as well as results from plagioclase‐liquid hygrometers, confirm a water‐rich melt pocket. The exsolution of volatiles (H2O, etc.), in this melt pocket, will contribute to local oxidation conditions, which may have been recorded by the concordant behaviour of FeO and An in plagioclase. Then, the overpressure caused by volatile exsolution would destabilize the magma chamber, which will eventually be broken by magma mixing/recharge, and lead to violent melt evacuation. Consequently, crystal size distribution (CSD) provides a new perspective on understanding the kinetic effect of magma mixing/recharge in the Okinawa Trough, especially on the mineral populations. Our study reveals the petrogenesis of crystal‐poor rhyolite within the framework of the mush model, refines the magma evolution history and demonstrates that pumice magma reaches volatile saturation before the eruption. [ABSTRACT FROM AUTHOR]

Large igneous provinces (LIPs) are often the surface expressions of mantle plume process. Intensive magma could occur in the continental crust when a mantle plume penetrates the Moho. How magmas migrate in the crust, forming LIPs, remains debated. In this study, we employ 2D thermo‐mechanical numerical modelling to study the dynamics of magma intrusion and migration within the continental crust affected by a mantle plume. Our results suggest that (1) lateral magma migration dominates crustal deformation, promoting the possible formation of metamorphic core complexes; (2) two distinct crustal deformation modes are recognized regarding the presence or absence of crustal break‐up, affected by whether a significant vertical magma migration occurs; (3) the crustal thickness, Moho temperature and the length of the preset weak crust–mantle decoupling zone are the three key parameters controlling crustal magma migration. This study highlights the importance of lateral magma migration in the lower crust and provides physical mechanisms for the interpretation of magma migration under LIPs. [ABSTRACT FROM AUTHOR]

Most of the global indium resources are from deposits associated with felsic rocks. Considering that the indium concentration in the average upper crust is extremely low, magmatic-hydrothermal processes play a critical role in the enrichment and mineralization of indium. However, the extraction efficiency of indium by magmatic fluids remains unclear. We performed experiments at 800 °C, 150 MPa and oxygen fugacity of Ni-NiO buffer to determine the partition coefficient of indium between aqueous fluids and granitic melts (D In f / m ). To counteract the rapid loss of indium into the noble metal container wall, the D In f / m were obtained by the method of local equilibrium between microscopic-sized fluid bubbles and surrounding silicate melt. The results show that indium has the highest fluid-melt partition coefficients of all metals investigated so far. At a constant aluminum saturation index (ASI = 1.07–1.12), D In f / m correlates linearly with the total Cl concentration in the coexisting fluid (m Cl total ), increasing from 61 ± 11 (1σ) at m Cl total = 1.0 mol/kg H 2 O to 895 ± 105 (1σ) at m Cl total = 16 mol/kg H 2 O. When the HCl concentration in the solution increases from 0.13 to 0.49 mol/kg H 2 O at a fixed m Cl total = 2 mol/kg H 2 O, D In f / m increases parabolically from 129 ± 21 to 320 ± 24. The observed partitioning data suggest that indium was dominantly present as In(OH) 2 Cl in the low-HCl and In(OH)Cl 2 in high-HCl aqueous fluid at the experimental conditions. Numerical modeling indicates that the extraction efficiency of indium from S-type felsic magmas is very high (>85 %) and magmatic fluids may be the major source of indium for most indium deposits. Due to the high D In f / m values, fluid saturation and exsolution result in a sharp drop of indium concentration in both the residual melt and crystallized minerals, which makes the indium concentration in whole rock and minerals an indicator of fluid exsolution. [ABSTRACT FROM AUTHOR]

For active volcanoes, knowledge of the architecture of the plumbing system and the conditions of magma storage prior to an eruption are highly important, given their influence on the eruptive style and, thus, the management of future volcanic crises. Here, chlorine is used as a geobarometer for potassic alkaline magmas at the Campi Flegrei volcanic complex, revealing the shallowest depth of fluid-melt equilibration with respect to Cl. The results for representative fallout deposits of selected explosive eruptions show the existence of a multi-depth equilibration zone through time, including shallow magma storage. We describe evidence for the shallowest zone located at a depth equivalent to 65 MPa for the Agnano Monte Spina eruption (4482–4625 cal. yrs BP), at ~100 MPa for the Pomici Principali (11 915–12 158 cal. yrs BP), and the Astroni 6 (4098–4297 cal. yrs BP) eruptions, and close to 115 MPa for the last explosive eruption of Monte Nuovo (AD 1538). For comparison, the pressure estimated for a possible reservoir feeding the Cretaio eruption of Ischia island (AD 430), the only studied eruption on Ischia, is ~140 MPa. The pressure estimates for the two largest magnitude eruptions, the Campanian Ignimbrite (40 ka) and the Neapolitan Yellow Tuff (14.9 ka), are also discussed with respect to available magma withdrawal models. The pressures estimated using the Cl geobarometer for the magma leading to the fallout phases of these two eruptions provide evidence for a low-volume, shallow domain (~40 MPa) for the Plinian phase of the Campanian Ignimbrite eruption and a main, deeper reservoir (~130–165 MPa) for the Neapolitan Yellow Tuff eruption. The inferred shallowest equilibration pressures are interpreted here as corresponding to transitory, short-lived magma apophyses, whose eruption may have been facilitated by optimum tectonic stresses, rheological behavior of the crust, and efficiency of volatile exsolution. Alternatively, these magma apophyses may represent an evolved, crystal-rich ponded magma into which a volatile-rich magma ascending from depth was injected. The transient nature of such very shallow reservoirs is suggested by the short timescales inferred from diffusion modeling on crystals available in the literature for the studied Campi Flegrei eruptions. The influence of sulfur (S) on Cl solubility is assessed through Cl solubility modeling and applied to different eruptions. In addition, the pressure at which magmatic fluids and melts equilibrated with respect to Cl is shallower for the Campi Flegrei volcanic complex than the Somma-Vesuvio volcanic complex, erupting more homogeneous differentiated magma, of trachytic or phonolitic composition. This approach of using Cl to investigate the architecture of the plumbing system can be extended to all alkali-rich magma systems. [ABSTRACT FROM AUTHOR]

This paper presents the results of petrographical, mineralogical, geochemical, and isotope-geochemical studies of granophyres and host ferrogabbros, quartz ferromonzogabbros, quartz monzodiorites, and quartz monzonites in the Mesoproterozoic Valaam sill in the Ladoga Graben on the Karelian Craton. The sill is poorly layered: the ferrogabbros compose the lower part of the sill, the middle part consists of quartz gabbro-monzonites and quartz monzonites, while graphic leucogranites (granophyres) form a dense network of veins mainly in the upper part of the sill. Geochemical features of ferrogabbro, iron-rich composition of olivine and pyroxene, and low Ca composition of plagioclase indicate the evolution along the Fenner trend. The granophyres have petro- and geochemical characteristics of anorogenic alkaline granites, with negative Eu/Eu* = 0.15–0.49 and REE distribution patterns similar to those of granophyres of layered intrusions. All rocks of the sill have close Sr isotopic composition (87Sr/86Sr)T = 0.7043–0.7066, and εNd values ranging from −9.6 to −11.2. Model calculations show that fractional crystallization can lead the initial ferrogabbro melt into the immiscibility field. Ilmenite–magnetite–silicate microstructures have been identified in the ferrogabbro and ferromontzogabbro from the sill; similar microstructures in layered intrusions are considered as evidence for the immiscibility of Fe-rich and Si-rich liquids (Holness et al., 2011; Dong et al., 2013). The segregation of the high-silica melt may have occurred in an intermediate crustal chamber at around 350 MPa and 960oC; magma was supplied as crystalline mush at the sill emplacement level at around 70 MPa and acidic melt migrated through it. This melt underwent fractional crystallization and interacted with host minerals. At the level of sill emplacement, it crystallized under supercooling into granophyre aggregates. The example of the Valaam sill shows that when the Fenner fractionation reaches the final composition–-ferrogabbro, its further evolution with a conjugate decrease in SiO2 and Fe contents can be related to the incomplete separation and mixing of Fe-rich melts and immiscibly split felsic melt. Such a mechanism can be implemented for the formation of the mafic part of AMCG-type massifs. [ABSTRACT FROM AUTHOR]

Granite genesis is crucial to understanding the evolution of continental crust, yet many concerns about granite genesis remain not well answered, such as whether I-type granite contains metasedimentary components, what controls granite compositional diversity, and how granitic plutons are constructed. To explore these issues, we conducted a detailed study on the two-mica plagiogranite, tonalite, and biotite plagiogranite units of the Wujinxia composite pluton in the eastern Qilian orogen, NE Tibetan Plateau. These units comprise two-mica plagiogranite, tonalite (with diorite enclave), and biotite plagiogranite. Zircon U–Pb data reveal that three granitic units formed at ~ 487 Ma, ~ 464 Ma, and ~ 430 Ma, respectively. Magmatic and xenocrystic garnet were identified from the tonalite and biotite plagiogranite, respectively. The two-mica plagiogranite, tonalite, and biotite plagiogranite all belong to low-K series rocks (K2O/Na2O = 0.10–0.26), and were derived from deep crustal sources mainly consisting of juvenile mafic rocks, with involvement of minor metasedimentary rocks in the magma sources of the two-mica plagiogranite and tonalite. The diorite enclave within the tonalite was probably derived from an enriched mantle-derived basaltic magma. Mineral compositions, thermobarometric calculations, and whole-rock geochemical data indicate that the low-K intrusive units of the Wujinxia composite pluton resulted from multiple magmatic systems at different depths. The results suggest that I-type granites can contain metasedimentary components by partial melting of a mixed crustal source, and high-Mn content helps the preservation of high-Ca garnet within such rocks. For a composite pluton spanning a large compositional variation, its compositional diversity is jointly controlled by magma source composition, melting condition and thermal evolution of individual magma pulses, and the resulted assembly style during pluton construction. [ABSTRACT FROM AUTHOR]

The surface gap of tephriphonolite compositions in the Passa Quatro alkaline complex, in SE Brazil, is attributed to non-buoyancy of these high viscosity intermediate compositions during magmatic fractional crystallization at different depths. Thermodynamic and Rayleigh models for three alkaline suites of a strongly silica-undersaturated series were integrated to demonstrate that parental (basanite, nephelinite and alkaline basalt) and residual (phonolites) magmas are cogenetic by fractional crystallization at pressures of 10 kbar and 5 kbar, i.e. at magma chambers located above and below the Conrad discontinuity within the Upper Cretaceous-Palaeogene 40 km-thick continental crust in SE Brazil. The fractional crystallization of the parental magmas produced an ultramafic residual solid (wehrlite, olivine-bearing clinopyroxenite and clinopyroxenite) and residual liquids (evolved basanite and alkaline basalt, and phonotephrite). The latter moved up and built magma chambers at lower depths in the continental crust where those magmas initially crystallized clinopyroxenite extracts and high viscosity residual liquid that was entrapped and prevented to ascent towards the surface. Then, an abrupt change in the extract mineralogy produced a feldspathic-rich extract (leucocratic leucite monzosyenite, mesocratic syenite or leucocratic monzodiorite) and a residual phonolitic liquid with low viscosity. Following the feldspar crystallization, the magma viscosity decreased, acquiring adequate buoyancy that resulted in shallow-crust magma chambers in which phonolite diversification took place. These processes occurred due to the existence of a transcrustal, plumbing architecture where the high viscosity intermediate tephriphonolites were prevented to reach shallower depths, resulting in the Daly gap observed in the Passa Quatro Alkaline Complex. [ABSTRACT FROM AUTHOR]

We investigate the tidal dissipation in Io's hypothetical fluid magma ocean using a new approach based on the solution of the 3D Navier‐Stokes equations. Our results indicate that the presence of a shallow magma ocean on top of a solid, partially molten layer leads to an order of magnitude increase in dissipation at low latitudes. Tidal heating in Io's magma ocean does not correlate with the distribution of hot spots, and is maximum for an ocean thickness of about 1 km and a viscosity of less than 104 Pa s. Due to the Coriolis effect, the k2 Love number can depend on the harmonic order. We show that the analysis of k2 may not reveal the presence of a fluid magma ocean if the ocean thickness is less than 2 km. If the fluid layer is thicker than 2 km, k20 ≈ k22/2 ≈ 0.7. Plain Language Summary: Jupiter's moon Io is the most active volcanic body in the Solar System. Although it is generally accepted that Io's volcanic activity is driven by the heat generated by tidal friction, the origin and the distribution of tidal heating within Io's interior remain a subject of debate. Here we investigate the tidal dissipation in Io's hypothetical fluid magma ocean using a new approach based on the solution of general equations describing the motion of viscous fluid. Our results indicate that the presence of a shallow magma ocean on top of a solid, partially molten layer leads to an order of magnitude increase in dissipation at low latitudes. Tidal heating in Io's magma ocean does not correlate with the distribution of hot spots, and is maximum for an ocean thickness of about 1 km and a viscosity of less than 104 Pa s. We also discuss the sensitivity of Io's gravity signature to the presence of a magma ocean and provide estimates of gravitational perturbations induced by tidal deformation. Key Points: The presence of a shallow magma ocean on top of a partially molten layer leads to a strong increase in tidal dissipation at low latitudesDue to the Coriolis effect, the degree‐2 Love numbers for models with a magma ocean can depend on the harmonic orderThe tidal Love numbers are not sensitive to the presence of a fluid magma ocean if the thickness of the fluid layer is less than 2 km [ABSTRACT FROM AUTHOR]

Forecast of eruptive activity is a core challenge in volcanology. Here, we present an actual forecast for the end of the 2021 La Palma eruption. Using continuous GNSS data, we identified a co‐eruptive quasi‐exponential deflation trend. Assuming mass conservation, magma upflow from an overpressurized reservoir drives the eruptive process. The forecast was carried out during the eruption, however there was uncertainty in the key percentage of drop in driving pressure necessary to stop this eruption. In hindcast, we explore how forecast uncertainty reduces with increase in ingested near‐real time data. We conclude that precise forecasts could have been possible, but only after twice a characteristic exponential decay time‐scale, providing error estimates of 45% of the actual duration. We verify the mass conservation assumption using eruptive material volumes and propose that the eruption dynamics was controlled by a main reservoir at a depth close to Moho discontinuity beneath Cumbre Vieja volcano. Plain Language Summary: The forecast, an actual prediction of the temporal or spatial characteristics of a future event, of when a volcanic eruption will end is challenging. This is reflected in the scarcity of literature about it. During the 2021 eruption of La Palma, we used GNSS geodetic data that tracks the change in shape of a volcano to make such a forecast. We exploited a temporal decaying pattern of this data and some basic assumptions that could be interpreted as when the eruption would stop. The forecast was made before the eruption ended, although it was too uncertain to have practical implications. With the eruption already over, we looked back at the data and found that the more information we could have analyzed, the more accurate the forecast could have been. We conclude that accurate forecasts could be possible after twice the characteristic time of the decay process has passed. Key Points: Using deformation data, the end of La Palma eruption, although uncertain, was possible to forecastExtensive end of eruption hindcasts to understand bounds on method applicability for La Palma eruptionsReal‐time ground deformation interpretation could represent a simple and powerful tool for La Palma volcano monitoring [ABSTRACT FROM AUTHOR]

In August 2021, Askja caldera switched to reinflation following ∼40 years of continuous deflation that was first measured some 20 years after its last eruption in 1961. Various lines of evidence, including from geodetic modeling, suggest that both the deflation and reinflation events are related to a shallow magma body. To better understand the subsurface plumbing system, we derive P‐wave velocity (Vp), S‐wave velocity (Vs), and Vp/Vs models of the mid‐upper crust by leveraging a new local earthquake traveltime data set. A cylindrical low‐velocity zone, ∼3 km wide and extending to ∼8 km below sea level (bsl), was imaged beneath the caldera. Within it, two distinct lower velocity and higher Vp/Vs anomalies are illuminated, one centered at ∼0.5 km and the other at ∼6 km bsl. The shallower anomaly lies directly beneath the zone of uplift and is likely associated with the current reinflation event. Plain Language Summary: The uplift at Askja, which started in August 2021, has drawn attention not only from volcanologists but also from the general public because it followed ∼40 years of subsidence first measured in 1981, 20 years after its last eruption in 1961. Several studies have related the subsidence to the deflation of a shallow magma body beneath the volcano, but this has not previously been detected by body wave tomography, which is a technique to image 3‐D variations in the subsurface, like a medical CT scan. It uses earthquakes that occur below and surrounding the volcano. In this study, we take advantage of a new earthquake data set to image the crust immediately beneath the volcano. We discover a shallow velocity anomaly that directly underlies the locus of surface uplift. This anomaly is likely caused by the presence of partial melt and higher temperatures, which is consistent with the existence of a shallow magma body that is causing the uplift. Understanding the nature of the current volcanic unrest is crucial, particularly in light of the large explosive eruption of 1875, which dispersed ash over large parts of Iceland. Key Points: A cylindrical low‐velocity zone, ∼3 km wide and extending to ∼8 km bsl, has been imaged beneath Askja calderaWithin this zone, two distinct lower velocity and higher Vp/Vs anomalies are detected at ∼0.5 km and ∼6 km bslThe shallower anomaly underlies an area of recent surface uplift, which is consistent with shallow melt accumulation [ABSTRACT FROM AUTHOR]

We investigated how spatial variations in tidal heating affect Io's isostatic topography at long wavelengths. The long‐wavelength relief is less than the 0.3 km uncertainty in Io's global shape. Assuming Airy isostasy, degree‐2 topography <0.3 km amplitude is only possible if surface heat flux varies spatially by <19% of the mean value. This is consistent with Io's volcano distribution and is possible if tidal heat is generated within and redistributed by a convecting layer underneath the lithosphere. However, that layer would require a viscosity <1010 Pa s. A magma ocean would have low enough viscosity but would not generate enough tidal heat internally. Conversely, assuming Pratt isostasy, we found ∼0.15 km degree‐2 topography is easily achievable. If a magma ocean was present, Airy isostasy would dominate; we therefore conclude that Io is unlikely to possess a magma ocean. Plain Language Summary: As it orbits Jupiter elliptically, the difference in gravitational pull experienced by the moon Io results in tidal heating due to internal friction. Some evidence suggests this heat forms a magma ocean beneath Io's crust. If so, there would be a difference in the amount of heat generated at Io's equator versus its poles and would alter the thickness of Io's crust between the two locales. Assuming the crust has a uniform density, its thickness would be inversely proportional to the tidal heat beneath the crust, which in turn affects the difference in Io's radius at the equator versus at its poles. However, reasonable variation in tidal heating across Io would result in a greater difference in radius than is observed. The difference in observed radius is more likely if variation in tidal heat across Io affects crustal density rather than crustal thickness. Then, it is more likely that Io does not have a magma ocean. Key Points: Long‐wavelength relief implies low spatial variation in Io's tidal heating when assuming Airy isostasyTidal heat produced in a convecting aesthenosphere can reduce spatial variation in tidal heating, but requires prohibitively low viscosityIo's topography is consistent with expected tidal heating spatial variations if thermal expansion drives crustal density variations [ABSTRACT FROM AUTHOR]

Petrogenetic models of martian magmas reflect the compositional, thermal, and geodynamical evolution of its interior. Most models for shergottite meteorites, which sampled relatively young martian basalts, invoke partial melting in a mantle plume head and filtering of the magma through the crust. Olivine-phyric, poikilitic, and olivine-gabbroic shergottites contain large, Mg-rich olivine crystals that record their parent magma history and are generally regarded to form initially in slow cooling, near-equilibrium environments in the lower crust. Here we report the unexpected common occurrence of Mg-rich olivine crystals with chained, mantled dendritic, and skeletal morphologies that reflect rapid growth, requiring relatively large degrees of undercooling and possibly moderate to fast cooling rates. Novel 3D analysis of crystal textures and core Fe-Mg content demonstrates that chained and mantled dendritic olivines in enriched shergottites are among the earliest-formed crystals, indicating rapid crystal growth during initial magma pooling in the lower crust, a process that has not been documented in Earth basalts. In geochemically depleted shergottites, skeletal olivines appear later in the crystallization sequence, but before the final eruption and solidification. Geochemically intermediate samples do not contain rapid-growth olivine, indicating extended equilibrium growth. The frequent occurrence of chained, mantled dendritic, and skeletal olivines in enriched and depleted shergottites suggests that the conditions needed for rapid growth are common for mafic magmatism on Mars, and that these magmas experience complex thermal histories characterized by discrete episodes of large undercooling at depth. [ABSTRACT FROM AUTHOR]

We propose that the 495-470 Ma Ollo de Sapo magmatism in the Iberian Massif was the result of a mantle plume event in the Furongian-Early Ordovician. This plume was located beneath the northwestern margin of Gondwana and caused rapid and extensive melting of Ediacaran arc-related crustal rocks and their derived sediments. Mafic magmas due to plume partial melting underplated the crust and were emplaced at mid-lower crustal levels (~15km), and provided the heat for crustal melting. Manifestations of the plume include (i) pronounced magnetic anomalies in the region which match the distribution of Ollo de Sapo rocks, (ii) the Toledanian unconformity (and gap), which is attributed to thermal doming, and (iii) the significant thickness variations in Lower to Middle Ordovician sedimentary successions in adjacent areas. In a more regional context, we infer that the plume was one of a cluster of plumes impacting the Gondwana periphery and that it contributed to the birth and development of the Rheic Ocean throughout Gondwana margin breakup. [ABSTRACT FROM AUTHOR]

Iron oxide-copper-gold (IOCG) deposits are a vital source of copper and critical elements for emerging clean technologies. Andean-type IOCG deposits form in continental arcs undergoing extension, and they have a temporal relationship with magmatism although they do not exhibit a close spatial relation with the causative intrusions. The processes required to form IOCG deposits and their potential connections to iron oxide–apatite (IOA)-type mineralization remain poorly constrained, as well as the characteristics of magmatism linked to both deposit types. Here we combine zircon U–Pb geochronology with zircon trace element geochemistry of intrusive rocks associated with the Candelaria deposit, one of the world's largest IOCG deposits, to unravel distinctive signatures diagnostic of magmatic fertility. Our results reveal a marked transition in the geochemistry of intrusions in the Candelaria district, characterized by changes in the redox state, water content and temperature of magmas over time. The oldest magmatic stage (~ 128–125 Ma), prior to the formation of the Candelaria deposit, was characterized by zircon Eu/Eu* ratios of 0.20–0.42, and redox conditions of ΔFMQ − 0.4 to + 1.0. The earliest magmatic stage related to the formation of Fe-rich mineralization at Candelaria (118–115 Ma) exhibits low zircon Eu/Eu* ratios (0.09–0.18), low oxygen fugacity values (ΔFMQ ~− 1.8 to + 0.2) and relatively high crystallization temperatures. In contrast, the youngest stage at ~ 111–108 Ma shows higher zircon Eu/Eu* (~ 0.37–0.69), higher oxygen fugacity values (ΔFMQ ~ + 0.4 to + 1.3) and a decrease in crystallization temperatures, conditions that are favorable for the transport and precipitation of sulfur and chalcophile elements. We conclude that Candelaria was formed through two distinct ore-forming stages: the first associated with a reduced, high temperature, water-poor magma developed under a low tectonic stress, followed by a more oxidized, water-rich, and low temperature magmatic event related to a compressional regime. The first event led to Fe-rich and S-poor IOA-type mineralization, while the second event with geochemical signatures similar to those of porphyry copper systems, generated the Cu- and S-rich mineralization. This late stage overprinted preexisting IOA mineralization resulting in the formation of the giant Candelaria IOCG deposit. [ABSTRACT FROM AUTHOR]

Determining the time spans of processes related to the assembly of eruptible magma at active volcanoes is fundamental to understand magma chamber dynamics and assess volcanic hazard. This information can be recorded in the chemical zoning of crystals. Nevertheless, this kind of study is still poorly employed for the active volcanoes of the Neapolitan area (Southern Italy), in particular, for Ischia island where the risk is extremely high and this information can provide the basis for probabilistic volcanic hazard assessment. For these reasons, we acquired chemical composition on clinopyroxene crystals erupted at Ischia during the Zaro eruption (6.6 ± 2.2 ka) and performed numerical simulations of the input of mafic magma into a trachytic reservoir, in order to investigate various aspects of pre-eruptive dynamics occurring at different timescales. This event emplaced a ~ 0.1 km3 lava complex, in which the main trachytic lava flows host abundant mafic to felsic enclaves. Previous petrological investigation suggested that mafic magma(s) mixed/mingled with a trachytic one, before the eruption. In this work, the clinopyroxene zoning patterns depict the growth of crystals in different magmatic environments, recording sequential changes occurred in the plumbing system before the eruption. The evolution of the plumbing system involved a hierarchy of timescales: a few hours for magma mingling caused by mafic recharge(s) and likely occurred multiple times over a decade during which a dominant magmatic environment was sustained before the eruption. Such timescales must be considered in volcanic hazard assessment at Ischia and similar active volcanoes in densely populated areas. [ABSTRACT FROM AUTHOR]

The mobility of trace elements in supercritical fluid-melt derived from pelite rich in volatiles has been studied experimentally at pressures from 3.0 to 7.8 GPa and temperatures from 750 to 1090 °С using the diamond trap method. The experiments simulate the conditions of warm and hot subduction, in which pelite either retains the whole inventory of volatiles or releases a fluid in three successive devolatilization steps. The 3.0 GPa and 750 °С runs with pelite rich in volatiles yield a supercritical fluid (SCF) which attains equilibrium with an eclogitic residue bearing phengite and accessory rutile, zircon, and monazite. At ≥5.5 GPa and ≥850 °С, above the second critical endpoint, the SCF transforms into a supercritical fluid-melt (SCFM) which acquires higher concentrations of almost all incompatible trace elements while the mineral assemblage of the equilibrium eclogitic residue remains the same but lacks monazite. The trace-element enrichment of SCFM is most prominent for Ba, Sr, LREE, Th, and U. At the hot subduction conditions, the fluid-melt likewise contains more K, Rb, Zr, and Hf, though LREE contents become lower. The negative Nb anomaly persists in all cases. SCFM has its trace-element composition generally similar to that of hydrous melt derived from oceanic sediments, but contains more REEs and water. Partitioning of LILE, HFSE, and LREE between the SCFM and residue phases mainly depends on the fluid-melt fraction and stability of host phengite, monazite, zircon, and rutile. Thus, sediment-derived SCFM can carry both fluid-mobile and sediment-melt elements to regions of arc- and back-arc magma generation and can translate the negative Nb anomaly inherited from sediment into the magmas. Early devolatilization of pelite increases the stability of monazite and phengite in the residue and provides efficient LREE, K and Rb transport to the mantle depths of ~ 250 km. Effective LREE and Th depletion of UHP metamorphic rocks is possible by SCFM release near peak metamorphic conditions. [ABSTRACT FROM AUTHOR]

Mantle magmas interact with surrounding rocks during their ascent and storage in the continental crust, leading to open system processes as wall rock partial melting. In this study, we have experimentally investigated the reactions between a leucosome depleted migmatite and a primitive K-basaltic of Campi Flegrei (Italy). Experiments were carried out at pressure of 0.8 GPa temperatures from 1250 °C to 1050 °C and constant temperature and thermal gradient conditions. The experimental products consist of biotite-free migmatite, glass and crystals of clinopyroxene, olivine, plagioclase and Cr-spinel with proportions that vary as a function of temperature. Open system isothermal experiments indicate that the chemistry of melts and phase relationships are controlled by the high Al2O3 content of leucosome depleted migmatite with the glass composition shifting from K-trachybasalt towards shoshonite as the temperature decreases from 1200 °C to 1125 °C. At temperatures 1150°C, migmatite assimilation is not exclusively due to the assimilation fractional crystallization process because evidence of mingling and mixing is observed. T-gradient experiment shows melt composition ranging from shoshonite to phono-tephrite moving from the slightly crystalline zone (T = 1250 –1210 °C) at the bottom of the capsule towards the highly crystalline zone (T = 1160 –1140 °C). This SiO2-constant trend indicates that at temperature below the basalt solidus, the assimilation of leucosome depleted crust is represented almost exclusively by the biotite breakdown, leading to the increase in Al, Mg, Fe, Ti, and K activities in the system. The shoshonitic composition obtained in our experiments could represent the parental magma for both Campi Flegrei volcanic district and Vesuvius magmatic systems, indicating modification in a deep storage zone through mixing with the partial melts derived from restitic continental crust. [ABSTRACT FROM AUTHOR]

Modeling the behavior of trace elements during lunar magma ocean solidification is important to further our understanding of the chemical evolution of the Moon. Lunar magma ocean evolution models rely on consistent datasets on how trace elements partition between a lunar silicate melt and coexisting minerals at different pressures, temperatures, and redox conditions. Here we report new experimental trace element partition coefficients (D) between clinopyroxene (cpx), pigeonite, orthopyroxene, plagioclase, olivine (ol), and silicate melt at conditions relevant for the lunar magma ocean. The data include Dcpx−melt at ambient and high pressures (1.5 GPa and 1310 °C), and partition coefficients at ambient pressure for pig, opx, ol, and pl. Overall, clinopyroxene is a phase that may control the fractionation of key geochemical trace element ratios, such as Lu/Hf and Sm/Nd, during the evolution of the lunar magma ocean. We explore the impact of the new silicate Dmineral−melt on the trace element evolution of the lunar magma ocean and we find that accessory phosphate minerals, such as apatite or whitlockite are of critical importance to explain the observed trace element and isotopic signature of the KREEP reservoir on the Moon. The new partition coefficients were applied to calculate the trace element evolution of the residual melts of the crystallizing lunar magma ocean and we propose a new trace element composition for the urKREEP reservoir. The new data will be useful for future thermo-chemical models in order to adequately predict the duration of the lunar magma ocean and the age of the Moon. [ABSTRACT FROM AUTHOR]

Pegmatite-type lithium (Li) deposits are an important source of the low-carbon energy metal, which is generally considered to be formed by the high degrees of differentiation of strongly peraluminous granitic magma. However, the question of whether the parental rocks of these peraluminous magmas are igneous or sedimentary has been widely debated. Recent studies have identified a worldclass pegmatite-type Li deposit belt (up to 2800 km long) closely associated with the Late Triassic granitoids and (meta)sedimentary rocks along the West Kunlun and Hoh Xil-Songpan-Ganze terranes in northern Tibet. This study presents a comprehensive petrological, geochronological, and geochemical study on the two types of Late Triassic granitoids in the Caolong-Xiangkariwa area of the Yushu region of central-eastern Hoh Xil-Songpan-Ganze terrane in northern Tibet: type A includes the Tongtianhe-Zhenqin-Zhaduo-Zhaya-Xiangkariwa (TZX) diorites and granodiorites (218-212 Ma), and type B includes the Caolong two-mica and muscovite granites (213-205 Ma), as well as ore-barren, beryl-bearing, and spodumene-bearing pegmatite dikes (209-196 Ma). The TZX diorites and granodiorites contain variable amounts of amphibolite and biotite. They are metaluminous to slightly peraluminous with variable SiO2 (54.4-71.3 wt%), MgO (0.72-7.26 wt%) contents, and Mg# values (40-70). Some samples with low SiO2 (54.4-58.5 wt%) contents have geochemical features similar to high-Mg andesites: e.g., high MgO contents (5.24-7.26 wt%) and Mg# values (61-70). The TZX diorites and granodiorites exhibit less enriched (86Sr/87Sr)i (0.7080-0.7118) and εNd(t) (-4.8 to -8.0). By contrast, the Caolong two-mica and muscovite granites are characterized by the occurrence of abundant muscovite (plus tourmaline and garnet) and are strongly peraluminous. The Caolong granites and pegmatites are geochemically characterized by high SiO2 contents (68.8-79.8 wt%) and low MgO contents (0.01-0.10 wt%) and Mg# values (4-23). They have εNd(t) values (-8.8 to -11.4; granites: -8.8 to -10.8; pegmatites: -9.2 to -11.4) that are more enriched than the TZX diorites and granodiorites but similar to those of Songpan-Ganze (meta) sedimentary rocks (-7.4 to -12.9), and the Caolong two-mica granites have high zircon Î'18O values (11.6-12.1). In addition, decreasing K/Rb ratios correspond to increasing Cs contents in K-feldspar and muscovite from the Caolong granites and pegmatites. Taking into account the Late Triassic granitoids and (meta)sedimentary rocks in the Hoh Xil-Songpan-Ganze terrane, we suggest that the TZX diorites and granodiorites were most probably formed by the partial melting of metasomatized lithospheric mantle that subsequently underwent extensive fractional crystallization. Conversely, the Caolong two-mica and muscovite granites were likely generated purely by the partial melting of (meta)sedimentary rocks rather than via the evolution of dioritic-granodioritic magmas. In summary, there were two kinds of granitic magmas with different sources in the Caolong-Xiangkariwa area. Finally, the Caolong pegmatites were most likely formed by the extreme differentiation of two-mica granitic magmas rather than the dioritic-granodioritic magmas. Therefore, the evolution of magmas derived from (meta) sedimentary rocks were most likely to have formed the Li-rich pegmatites. Moreover, these (meta)sedimentary rocks representing the ultimate Li source must have undergone strong chemical weathering, resulting in significant Li enrichment. [ABSTRACT FROM AUTHOR]

Composite Ni-Cu sulfide- and Fe-Ti oxide-bearing mafic-ultramafic intrusions have been discovered in convergent margin settings worldwide, but their origins remain enigmatic. Permian Kebu mafic-ultramafic intrusion in the Central Asian Orogenic Belt hosts both Ni-Cu sulfide and Fe-Ti oxide mineralization and formed in a post-collisional, Andean-style arc setting. The Ni-Cu sulfide- and Fe-Ti oxide-bearing rocks in the intrusion have similarly arc-like trace element patterns on the primitive mantle-normalized trace element diagram and negative εNd(t) values (-16 to -5), which indicate that the parental magma of the intrusion may have been derived from the enriched, metasomatized lithospheric mantle. The magma oxygen fugacity (fO2) was calculated to be FMQ + 1.3~FMQ + 2.0, which can be attributed to the evolution of hydrated parental magma derived from the metasomatized lithospheric mantle. Also, the rocks all have negative δ13C values (-28.5‰ to -20‰), which indicates incorporation of external-derived crustal organic carbon into magmas. However, the Ni-Cu sulfide-bearing rocks contain more high-temperature carbon than the Fe-Ti oxide-bearing rocks. Modeling results based on alphaMELTS show that the magmas forming the Ni-Cu sulfide-bearing rocks may have assimilated more organic carbon than those that formed the Fe-Ti oxide-bearing rocks. Based on the estimated amounts of organic carbon in the two types of rocks, we deduced that initially oxidized magma pulses may have been reduced in variable degrees, leading to the formation of composite Ni-Cu sulfide and Fe-Ti oxide mineralization in one intrusive body. Mafic magmas in subduction-related, convergent margin settings are commonly highly oxidized due to metasomatism of the mantle wedge by slab-derived fluids/melts, and this may explain why the mafic-ultramafic intrusions associated with composite Ni-Cu sulfide and Fe-Ti oxide mineralization often occur in convergent margin settings. [ABSTRACT FROM AUTHOR]

Studies have revealed the key role of deepseated, ore-forming fluids and metals in the generation of the Early Cretaceous largescale gold deposits in the Jiaodong gold province of eastern China. However, how the ore-forming materials were transported to shallow crustal levels remains unclear. Here, we investigate trace elements and sulfur isotopes of pyrite within mafic microgranular enclaves (MMEs) of Gushan granite to evaluate the role of the syn-mineralization of mafic enclaves in the transportation of ore-forming materials. Zircon U-Pb and molybdenite Re-Os dating indicate that the magmatichydrothermal event in the potassic-altered Gushan granite occurred at ca. 120 Ma, which is contemporaneous with the Jiaodong gold mineralization. The texture and geochemical compositions of pyrite indicate that pyrite grains hosted by Gushan MMEs are of deuteric hydrothermal origin and precipitated during or shortly after magma mixing. The distribution of elements (i.e., Co, Cu, Ni, Zn, As, Ag, Au, Pb, and Bi) and the sulfur isotope (4.14‰-8.8‰) data for pyrites from Gushan MMEs are quite identical to those of the Xiejia diorite intrusion (DI) and other ores from the Jiaodong gold province, which indicates a common source of these pyrites. The common origin of the pyrites, combined with evidence from previous work, suggest that the ore-forming fluids and materials originated from the metasomatized lithospheric mantle, which was the repository of water, sulfur, and volatiles from the subducted Paleo-Pacific plate, rather than by direct release from the subducted sediments of the Paleo-Pacific plate. Our results collectively show that the arc-like mafic magmas derived from the metasomatized lithospheric mantle at ca. 120 Ma were the intermediary that transported the gold and other oreforming components from the deep mantle to the shallow crustal levels where gold and ore-related material were injected into the Weideshan granitic suite during magma mixing. Thus, the Weideshan granitic suite may have played a critical role by continuously transferring gold to the shallow crustal faults where it precipitated. Therefore, future research or deep-drilling exploration programs in the area should emphasize the Weideshan granitic suite rather than the Xiejia DI. [ABSTRACT FROM AUTHOR]

Lamprophyres are spatially and temporally widespread in continental belts, but their magmatic differentiation process and melting dynamic mechanisms remain subjects of debate. In this study, we report mineral chemistry, bulk-rock compositions, and Sr-Nd-O isotopes of the alkaline lamprophyres (including monchiquite and camptonite) from the Tuoyun Basin of the southwestern Central Asian Orogenic Belt. Based on the P-T estimates, transcrustal magmatic reservoirs from the lower crust to upper crust are revealed for monchiquite and camptonite. These magmatic reservoirs were potentially connected, and the magmatic recharge and mixing processes that occurred were recorded by zoned clinopyroxene and amphibole. The diverse crystal populations are suggested to have originated from multiple batches of magmas, which were then involved in forming the subsequent magmas. The Sr-Nd isotopic compositions are relatively depleted, with (87Sr/86Sr)i = 0.70390-0.70452 and εNd(t) = 5.46-6.49 for the monchiquite, while the values for camptonite are 0.70391-0.70463 and 4.71-5.02. Moreover, the olivine in situ O isotopes in the monchiquite show Î'18OV-SMOW values of 4.81‰-5.40‰, which are comparable to those of the mantle peridotite. Compared with the experimental melts, a hybridized mantle source of hydrous peridotite + silica-depleted pyroxenite is proposed, and partial melting of this component was induced by the upwelling asthenosphere. Ultimately, our study highlights the critical role of the magmatic plumbing system and hydrous mantle source in the formation of Tuoyun lamprophyres. [ABSTRACT FROM AUTHOR]

Basaltic volcanism on the Moon produced low- and high-Ti mare basalt suites that are also distinct with respect to their iron, titanium, and magnesium isotopic compositions. Here, the equilibrium fractionation of Fe and Ti isotopes between ilmenite and melt was experimentally investigated in order to evaluate the role of ilmenite in generating the isotopic compositional variability among the lunar mare basalts. Ilmenite crystallization experiments were conducted using two bulk compositions: an ilmenite-saturated basaltic andesite and an ilmenite-saturated Apollo 14 black glass, and the Fe and Ti isotopic compositions of the experimental ilmenites and glass (quenched melt) were analyzed using solution MC-ICPMS after hand-picking. Additionally, Nuclear Resonant Inelastic X-ray Scattering (NRIXS) measurements on synthetic ilmenite were conducted and compared to previous NRIXS measurements on synthetic lunar glasses in order to derive temperature-dependent equilibrium ilmenite-melt Fe isotopic fractionations. Experimentally determined ilmenite-melt fractionations were then incorporated into a lunar magma ocean crystallization model that tracks the major element and isotopic compositional evolution of lunar magma ocean cumulates and residual liquid. There is good agreement between the Fe equilibrium isotopic fractionation measured by NRIXS and the laboratory equilibration experiments, and we find that the isotopic fractionation is sensitive to ilmenite compositional differences (0 vs. 10% Fe3+). Further, the light Ti isotopic composition of ilmenite relative to the melt (Δ 49 Ti = ilmenite-melt − 0.09 ± 0.03 ‰ at 1100 ∘C) is consistent with the higher coordination of Ti in ilmenite relative to melts and results of previous studies. The modeled Ti isotopic compositions for lunar magma ocean cumulates display Ti isotopic variability sufficient to explain the low- and high-Ti mare basalt sources. However, the difference in Fe isotopic composition between the low- and high-Ti mare basalts cannot be attributed solely to ilmenite fractionation. Instead, Fe isotopic fractionation by additional products of lunar magma ocean crystallization, such as clinopyroxene, is required to generate the inferred Fe and Mg isotopic variability in the lunar mantle. Alternatively, the Fe and Mg isotopic compositions of the lunar mare basalts may indicate Fe-Mg interdiffusion has occurred in the Ti-rich component of the mare basalt source regions via reaction between ilmenite cumulates and the olivine- and pyroxene-rich lunar mantle. [ABSTRACT FROM AUTHOR]

It is widely acknowledged that thermal models clearly demonstrate that crustal magma bodies should solidify rapidly upon emplacement. Small plutons can cool below the solidus in thousands of years, while even large plutons require hundreds of thousands of years, but not more than a million years. However, recent U-Pb zircon geochronological data contradict these results, strongly suggesting that magmatic systems are often characterized by protracted events. Therefore, a conceptual framework that reconciles thermal models and the geochronology data is necessary. The Devonian foreland magmatism of the Sierra de San Luis is made up of two distinctive suites, the Monzonite suite (<65 wt.% SiO2) and the Granite suite (>65 wt.% SiO2), both emplaced at ca. 3.7 kbar. Classification of the studied Devonian granitoids is debatable because they have a hybrid I- to A-type granite signature. Based on a robust geochronological U-Pb zircon dataset we corroborate the development of a protracted magmatic activity with three major crystallization events for this Devonian magmatism: 391 ± 1, 384 ± 1, and 379 ± 2 Ma. Considering these geochronological data, we postulate the presence of a deep mush reservoir, where a prolonged magmatic activity, permitted the prolonged crystallization of antecrysts (ca. 395–384 Ma). Migration of the parental magma from the mush reservoir zone occurred near the time of emplacement and culminated in the formation of an ephemeral magma chamber located at shallow levels, where zircon autocrysts crystallized (ca. 379 Ma). Age spectra reported within individual samples support the idea of a massive migration of magma when conditions were favourable (e.g. thermally matured crust). Individual crystallization ages recorded by monazites hosted in two-mica granites are comparable to those obtained from zircons, supporting the presence of a long-lasting hot source. Additional geochronological data indicate that a later thermal event (ca. 353 Ma) could have partially affected some areas of the Devonian magmatic zircons promoting Pb loss, with subsequent partial resetting of the isotopic clock. [ABSTRACT FROM AUTHOR]

Although magma migration is a necessary condition for the occurrence of a volcanic eruption, static analytical models for ground deformations consider stationary sources that undergo a change only in forces acting in the Earth's interior, such as changes in pressure or volume in a geometrically defined body. The variations in pressure or volume are mostly linked to the fluid dynamics or the superficializing of magma batches. Detection and tracking of magma motion in volcanic areas represent fundamental capabilities in predicting possible eruptions and therefore in reducing their associated risks. In the 3‐dimensional space, a magma migration defines a starting volume in depression and an arrival volume in overpressure. These end members can be modeled with two bonded point sources. Such a double‐point source can be considered the equivalent of a physical dipole. Here, the analytical solutions to predict ground deformations caused by a dipole source are presented and analyzed. The dipole analytical source allows modeling the effects on ground deformation of magma migration and vice versa. Estimating the magma migration from the measured ground deformation through data inversion. The dipole solution is compared with the basic volumetric source to discern its distinctive peculiarities and range of applicability. In addition, a discrepancy analysis with the equivalent numerical model was conducted to evaluate the approximation errors of the analytical model. To evaluate the practical value of the proposed model, two case studies on Sinabung volcano and Mt. Etna are presented. The analysis of continuous deformation data from GNSS (Global Navigation Satellite System) stations on Mt. Etna shows that a dipole source activates days before the December 2018 eruption, thus allowing the identification of the final magma rise. Plain Language Summary: Traditional analytical models for ground deformations focus on fixed sources and do not consider the possibility that magma may move, which is important for predicting volcanic eruptions. To better understand and predict eruptions, it is crucial to track magma migration. The dipole analytical source is a tool that helps model how magma movement affects ground deformation. It estimates magma migration by analyzing measured ground deformation data. This method provides information on the source's strength, location, and migration direction. Two case studies on Sinabung volcano and Mt. Etna show the practical value of the dipole source. In the Mt. Etna case, a dipole source was identified days before the December 2018 eruption, demonstrating its potential for early detection. Key Points: Analytical solutions for ground deformations caused by a dipole source are presented and analyzedThe differential dipole model can describe a movement of magma within the plumbing systemThe dipole model can be useful in identifying the magmatic rising phase that potentially anticipate an eruption [ABSTRACT FROM AUTHOR]

The Gulf of Guinea exhibits a continuous emission of narrow-band and long-period signals (16, 26 and 27 s) on teleseismic records, yet the underlying excitation mechanism remains unclear. This study establishes a connection between these tremors and the vibration of thin, decoupled crustal plates at unexplored volcanoes in the gulf. We first formulate the damped plate oscillation equation, by incorporating the vibration of the thin surface crustal plate and magma flow in the subsurface sill. The findings reveal that a fundamental-mode vibration with a period of several dozen seconds can be induced by a crustal plate that is less than 1.0 km thick but extends over tens of kilometres in both length and width, given a subsurface sill depth exceeding 10.0 cm. The thin plate hypothesis also allows for excitation of a few overtone modes, but such waves in higher frequencies diminish over long distances, leaving only the monotonous fundamental-mode vibration at teleseismic stations. The long duration of Guinea tremors at each recurrence is attributed to the presence of low viscosity basaltic magma, which influences the damping factor. Direct wave loads at the shallow gulf serve as the primary vibration source, accounting for seasonal variations and recurring patterns. Sporadic energy bursts may also occur due to large storms. Radiation patterns of Guinea tremors are linked to the geometric structure of the thin plate. Our theoretical estimates of tremor spectra closely align with observed data, confirming the model's accuracy in capturing reported Guinea tremor characteristics. This study provides valuable insights into the origins of very long-period tremors at continental volcanoes. [ABSTRACT FROM AUTHOR]

Granulites from the Narryer Terrane in the northern Yilgarn Craton, Australia, record evidence for high to ultrahigh thermal gradients during the Meso–Neoarchean. U–Pb zircon ages reflect a complex history of high‐grade, prolonged and poly‐phase metamorphism, with evidence for several thermal pulses at ca. 2745–2725, ca. 2690–2660, and ca. 2650–2610 Ma. Forward phase equilibrium modeling on rocks with varying bulk compositions and mineral assemblages suggests that peak temperatures reached 880–920°C at pressures of 5.5–6 kbar at ca. 2690–2665 Ma, followed by near‐isobaric cooling. These new P–T results also indicate that these rocks experienced some of the hottest thermal gradient regimes in the metamorphic record (≥150°C/kbar). Based on P–T models, U–Pb ages, and geochemical constraints, our data suggest that the geodynamic setting for the formation of this unusual thermal regime is ultimately tied to cratonization of the Yilgarn Craton. Previous models have inferred that ultrahigh thermal gradients and coeval large‐scale anatexis in the Narryer Terrane were primarily generated by mantle‐driven processes, despite most of the lithological, isotopic, and geochemical observations being at odds with the expected geological expression of large‐scale mantle upwelling. We re‐evaluate the mechanisms for high‐grade metamorphism in the Narryer terrane and propose that long‐lived high crustal temperatures between ca. 2690 Ma and 2610 Ma were instead facilitated by elevated radiogenic heat production in thickened, highly differentiated ancient crust. Mantle‐derived magma input and new crustal addition may not be the only drivers for high‐ to ultrahigh‐temperature metamorphism and stabilization of ancient crustal blocks. [ABSTRACT FROM AUTHOR]

Despite of the relatively rare occurrence of alkaline igneous rocks on Earth, they are the most diverse group of igneous rocks due to variations in their mineral assemblages and geochemical compositions. Alkaline igneous rocks are generally characterized by Si undersaturation, and K-Na (and in some cases C) enrichment. Although there is no unified alkaline igneous rock classification scheme, diagrams such as total alkalis-SiO2 or K2O-SiO2 can be used to classify alkaline igneous rocks. The origins of silica-saturated alkaline rocks (SiO2>52 wt.%) are relatively complex because multiple episodes of magmatism are often involved, therefore most studies have focused on the origins of silica-undersaturated alkaline magmas. Numerous experimental petrological studies have been conducted in the past few decades. Initially, it was considered that enrichment of trace elements was only achieved by low-degree partial melting of mantle peridotite, but the experimental melts could not reproduce the geochemical composition of natural alkaline igneous rocks. Subsequent studies have focused on carbonate-bearing eclogites that represent the average component of subducted oceanic crust. Although experimental studies indicate that silica-undersaturated and alkali-oversaturated melts can be generated from eclogites, some studies have considered that natural silica-undersaturated alkaline igneous rocks are the result of multi-stage source enrichment by incompatible elements. Low-degree partial melts of the mantle can be emplaced in the lithospheric mantle, forming veins consisting of phlogopite, amphibole, and pyroxene. Melting experiments including these components show that the produced melts better reproduce the naturally occurring silica-undersaturated alkaline magmas. Silica-deficient alkaline igneous rocks occur in various tectonic settings. Those in intraplate and divergent settings (i.e., mainly continental rifts) normally involve contributions from recycled components such as subducted slabs at the mantle transition zone (MTZ) or metasomatized lithospheric mantle. At convergent plate boundaries, silica-undersaturated alkaline magmas can be derived by the melting of mélange or the focused breakdown of phlogopite at back-arc depths. We compiled global data for alkaline igneous rocks and discovered that silica-undersaturated alkaline igneous rocks in continental collisional zones are K-rich and differ from those from other tectonic settings. We suggest that subducted continental sediment is an important K-rich end-member, which contributes a large amount of K to the alkaline magmas in the collision zone. Moreover, the solidus of K-rich minerals in the subducted plate implies that K can only participate in magmatism in the subduction zone. Before the plate reaches a depth of ∼300 km, the mica-group minerals, K-feldspar, evaporitic minerals, and other K-rich minerals are gradually consumed and rarely participate in deeper processes. In contrast, relatively Na-rich minerals such as pyroxene can be transported into the deeper mantle with eclogitic oceanic crust, and the resultant melt can enter the lithosphere owing to convective mantle flow. This forms metasomatic minerals, such as amphibole, in the lithospheric mantle, which melt to generate Na-rich and low-Si alkaline magmas. [ABSTRACT FROM AUTHOR]

Volcanic islands are often subject to flank instability, resulting from a combination of magmatic intrusions along rift zones and gravitational spreading causing extensional faulting at the surface. Here, we study the Koaʻe fault system (KFS), located south of the summit caldera of Kīlauea volcano in Hawaiʻi, one of the most active volcanoes on Earth, prone to active faulting, episodic dike intrusions, and flank instability. Two rift zones and the KFS are major structures controlling volcanic flank instability and magma propagation. Although several magmatic intrusions occurred over the KFS, the link between these faults, two nearby rift zones and the flank instability, is still poorly studied. To better characterize the KFS and its structural linkage with the surrounding fault and rift zones, we performed a detailed structural analysis of the extensional fault system, coupled with a helicopter photogrammetric survey, covering part of the south flank of Kīlauea. We generated a high-resolution DEM (~ 8 cm) and orthomosaic (~ 4 cm) to map the fracture field in detail. We also collected ~ 1000 ground structural measurements of extensional fractures during our three field missions (2019, 2022, and 2023). We observed many small, interconnected grabens, monoclines, rollover structures, and en-echelon fractures that were in part previously undocumented. We estimate the cumulative displacement rate across the KFS during the last 600 ~ 700 years and found a decrease toward the west of the horizontal component from 2 to 6 cm per year, consistent with GNSS data. Integrating morphology observations, fault mapping, and kinematic measurements, we propose a new kinematic model of the upper part of the Kīlauea's south flank, suggesting a clockwise rotation and a translation of a triangular wedge. This wedge is bordered by the extensional structures (ERZ, SWRZ, and the KFS), largely influenced by gravitational spreading. These findings illustrate a structural linkage between the two rift zones and the KFS, the latter being episodically affected by dike intrusions. [ABSTRACT FROM AUTHOR]

Because dike propagation depends on stress state, the geometry of dikes can be used to make inferences about crustal stress conditions during emplacement. Early work relied on analytical solutions for stress in a two-dimensional elastic medium with a pressurized circular magma chamber and biaxial far-field stress. The principal stress trajectories in this classical model depend on the ratio of deviatoric stress magnitude to chamber pressure. Assuming dikes follow principal stress trajectories and bounding plausible magma chamber excess pressures lead to estimates of deviatoric stress magnitudes from the map pattern of dikes. Mériaux and Lister (2002) pointed out that this approach ignored stresses due to the magma-filled dikes themselves, which significantly alter predicted dike trajectories. They estimated deviatoric stresses 2 to 5 times previous estimates. However, Mériaux and Lister (2002) assumed the pressure distribution within the dike rather than computing it from viscous magma flow. We revisit this simplification using a 2D model which fully couples a linear elastic host rock with a pressurized chamber and a fluid-filled dike, assuming the lubrication approximation for viscous flow. This model is solved using the finite element method (FEM). Ensuring that dike propagation is stable limits the dike-tip cavity pressure for realistic fracture toughness. We find that computed trajectories fall between the classical principal stress and Mériaux and Lister (2002) trajectories for given regional stress and chamber pressure conditions. This leads to deviatoric stress magnitude estimates that are 1 to 2 times the classical estimates, and 1/2 to 1/3 the Mériaux and Lister (2002) estimates. We also explore the consequences of chamber depressurization due to magma outflow during dike propagation. For a given melt compressibility, the resulting trajectories align more closely with those obtained from the classical model, compared to those obtained assuming a constant chamber pressure. At higher ratios of tectonic stress to chamber pressure, the trajectories are nearly identical. In both the constant pressure and depressurizing chamber cases, our results suggest that realistic magma pressure profiles within a dike lead to smaller estimated ratios of deviatoric stress to chamber pressure than found by Mériaux and Lister (2002). Future work should extend dike propagation models to three dimensions, and more thoroughly explore effects of magma compressibility. [ABSTRACT FROM AUTHOR]

Axial Seamount is a submarine volcano on the Juan de Fuca Ridge with enhanced magma supply from the Cobb hotspot. We compare several deformation model configurations to explore how the spatial component of Axial's deformation time series relates to magma reservoir geometry imaged by multi‐channel seismic (MCS) surveys. To constrain the models, we use vertical displacements from seafloor pressure sensors and repeat autonomous underwater vehicle (AUV) bathymetric surveys between 2016 and 2020. We show that implementing the MCS‐derived 3D main magma reservoir (MMR) geometry with uniform pressure in a finite element model with uniform elastic host rock properties poorly fits the geodetic data. To test the hypothesis that there is compartmentalization within the MMR that results in heterogeneous pressure distribution, we compare analytical models using various horizontal sill configurations constrained by the MMR geometry. Using distributed pressure sources significantly improves the Root Mean Square Error (RMSE) between the inflation data and the models by an order of magnitude. The RMSE between the AUV data and the models is not improved as much, likely due to larger uncertainty of the AUV data. The models estimate the volume change for the 2016–2020 inter‐eruptive inflation period to be between 0.054 and 0.060 km3 and suggest that the MMR is compartmentalized, with most magma accumulating in sill‐like bodies embedded in crystal mush along the western‐central edge of the MMR. The results reveal the complexity of Axial's plumbing system and demonstrate the utility of integrating geodetic data and seismic imagery to gain insights into magma storage at active volcanoes. Plain Language Summary: Axial Seamount is a submarine volcano on the Juan de Fuca Ridge (NE Pacific Ocean) with enhanced magma supply from the Cobb hotspot. Its frequent activity and long‐term deformation time series covering eruptions in 1998, 2011, and 2015 make it an ideal place to study volcanic processes. Improved magma reservoir modeling at Axial will aid in understanding how magma transport and storage are related to surface deformation, seismicity, and eruption timing. Here we compare several models of Axial's magma reservoir to explore how the spatial component of the observed deformation at Axial compares to seismically imaged magma reservoir geometry. To constrain the models, we use vertical displacements covering an inflation period between 2016 and 2020, derived from pressure measurements collected at seafloor benchmarks and repeated bathymetric surveys. The models estimate the volume change for the 2016–2020 inflation period to be between 0.054 and 0.060 km3. Our results suggest that Axial's magma reservoir is compartmentalized, with most magma accumulating in sill‐like bodies embedded in crystal mush. The results reveal the spatial complexity of Axial's plumbing system and demonstrate how deformation data and seismic imagery can be used together to gain deeper insights into magma storage at active volcanoes. Key Points: Uniform pressurization of Axial Seamount's seismically imaged magma reservoir does not adequately fit the observed geodetic dataOur models estimate that Axial's magma reservoir inflated by 0.054–0.060 km3 during the inter‐eruptive recharge period between 2016 and 2020Axial's magma reservoir is likely compartmentalized, with magma accumulating in sills along the western‐central edge of the magma reservoir [ABSTRACT FROM AUTHOR]

Understanding the stress distribution around shallow magma chambers is vital for forecasting eruption sites and magma propagation directions. To achieve accurate forecasts, comprehensive insight into the stress field surrounding magma chambers and near the surface is essential. Existing stress models for pressurized magma chambers often assume a homogenous elastic half‐space or a heterogeneous crust with varying mechanical properties in horizontal layers. However, as many volcanoes have complex, non‐horizontal, and heterogeneous layers, we enhance these assumptions by considering mechanically stratified layers with varying dips. We employed the Finite Element Method (FEM) to create numerical models simulating three chamber geometries: circular, sill‐like and prolate. The primary condition was a 10 MPa excess pressure within the magma chamber, generating the stress field. Layers dips by 20‐degree increments, with differing elastic moduli, represented by stiffness ratios of the successive layers (EU/EL) ranging from 0.01 to 100. Our findings validate prior research on heterogeneous crustal modeling, showing that high stiffness ratios disrupt stress within layers and induce local stress rotations at mismatched interfaces. Layer dip further influences stress fields, shifting the location of maximum stress concentration over varying distances. This study underscores the significance of accurately understanding mechanical properties, layer dip in volcanoes, and magma chamber geometry. Improving forecasting of future eruption vents in active volcanoes, particularly in the Andes with its deformed, folded, and non‐horizontal stratified crust, hinges on this knowledge. By expanding stress models to incorporate complex geological structures, we enhance our ability to forecast eruption sites and magma propagation paths. Plain Language Summary: Understanding crustal stress distribution within active volcanoes is crucial to forecast how magma will propagate inside a volcano and where and when a volcanic eruption may occur. Currently, the models used to understand the stress field within volcanoes assume that the Earth's crust is made of the same materials or with horizontally layered different materials. Both cases are seldom correct. Volcanoes often have layers that are both mechanically diverse and dipping at different angles and directions. To improve forecast models, we considered a crust with layers of different mechanical properties and with variable dips. We used numerical models to simulate 3 pressurized magma chamber geometries. We changed the dip of the layers and investigated how the rocks respond to the applied pressure. We found that when the layers are inclined they respond differently to the applied pressure and the possible location of a new eruption is displaced by up to 2 km, compared to the expected location using common modeling protocols. This research improves volcano understanding, especially in regions like the Andes, where the crust is often made by geologically diverse dipping layers. By making our models more realistic we can better forecast where eruptions may occur. Key Points: FEM models used to analyze the influence of layer dip on crustal stresses resulting from magma chamber pressurizationPeak surface tensile stresses can shift by more than 2 km, deviating from homogeneous elastic half‐space assumptionsThe effect is more pronounced with an idealized circular chamber when compared to a sill‐like chamber [ABSTRACT FROM AUTHOR]

The thermal activity of a magmatic–hydrothermal system commonly changes at various stages of volcanic activity. Few studies have provided an entire picture of the thermal activity of such a system over an eruptive cycle, which is essential for understanding the subsurface heat transport process that culminates in an eruption. This study quantitatively evaluated a sequence of thermal activity associated with two phreatic eruptions in 2021 at Aso volcano. We estimated plume-laden heat discharge rates and corresponding H2O flux during 2020–2022 by using two simple methods. We then validated the estimated H2O flux by comparison with volcanic gas monitoring results. Our results showed that the heat discharge rate varied substantially throughout the eruptive cycle. During the pre-eruptive quiescent period (June 2020–May 2021), anomalously large heat discharge (300–800 MW) were observed that were likely due to enhanced magma convection degassing. During the run-up period (June–October 2021), there was no evident change in heat discharge (300–500 MW), but this was accompanied by simultaneous pressurization and heating of an underlying hydrothermal system. These signals imply progress of partial sealing of the hydrothermal system. In the co-eruptive period, the subsequent heat supply from a magmatic region resulted in additional pressurization, which led to the first eruption (October 14, 2021). The heat discharge rates peaked (2000–4000 MW) the day before the second eruption (October 19, 2021), which was accompanied by sustained pressurization of the magma chamber that eventually resulted in a more explosive eruption. In the post-eruptive period, enhanced heat discharge (~ 1000 MW) continued for four months, and finally returned to the background level of the quiescent period (< 300 MW) in early March 2022. Despite using simple models, we quantitatively tracked transient thermal activity and revealed the underlying heat transport processes throughout the Aso 2021 eruptive activity. [ABSTRACT FROM AUTHOR]

Standard geodetic models simplify magma sheet injection to the opening of geometrically simple dislocations in a linearly elastic, homogeneous medium. Intrusion geometries are often complex, however, and non‐elastic deformation mechanisms can dominate the response of heterogeneous rocks to magma‐induced stresses. We used three‐dimensional near‐surface displacements of a scaled laboratory experiment in which a steeply inclined analog magma sheet was injected into granular material. We ran forward models and inverted for eight parameters of an "Okada‐type" tensile rectangular dislocation in a homogeneous, isotropic, and linearly elastic half‐space. Displacements generated by a forward model largely mismatch the experimental displacements, but full or restricted non‐linear inversions of geometrical parameters reduce the residual displacements. The intrusion opening, dip, depth, and to a lesser degree length and width mismatch the most between the experiment and inversion results, whereas location and strike mismatch the least. Our results challenge assumptions made by many analytical and geodetic models. Plain Language Summary: Standard models of volcano deformation simplify a magma intrusion to simple geometries injected in a medium with simplified mechanical behavior. However, intrusion geometries are often complex in nature. Rocks also predominantly respond in a complex manner to magma intrusion. We used the three‐dimensional displacement of the surface of a scaled laboratory experiment in which golden syrup, a magma analog, was injected into a sand‐plaster mixture, an analog for the Earth's crust. Our forward models and inversions show that the modeled simplified geometry and mechanical response largely mismatch the laboratory experiment outcome as observed in X‐ray Computed Tomography imagery. Our results challenge the assumptions made by models commonly used to model and interpret deformation signals measured in volcanically active areas. Key Points: Analog magma intrusions in granular material are approximated by tensile opening dislocations in a linearly elastic half‐spaceInversion results match analog intrusion x‐y location and strike, but mismatch intrusion dip, opening, and depthSimplifying the host rock response to linear elasticity of homogeneous material results in inaccurate inversion model results [ABSTRACT FROM AUTHOR]

The Okinawa Trough is an incipient back-arc basin formed by the subduction of the Philippine Sea Plate beneath the Eurasian Plate and is a natural laboratory for studying basin evolution, magmatism, and crust-mantle interactions during the early stages of back-arc spreading. Back-arc spreading and recent magmatism are occurring mainly in the Middle Okinawa Trough (MOT) and Southern Okinawa Trough (SOT). In order to investigate the magmatism in the Okinawa Trough, volcanic rock samples from the MOT and SOT were analysed for Fe – Sr – Nd – Pb – Hf isotopic compositions. The Fe isotopic compositions of basaltic andesite samples from the SOT are similar to or lower than MORBs. The fluid/melt derived from the subducted slab, especially the fluid dehydrated from slab serpentinites and sediment-derived melts, entered the overlying depleted mantle wedge and participated in magma generation, which resulted in the low δ56Fe values of the SOT basaltic magmas. The δ56Fe values of volcanic rocks from the MOT increase with increasing SiO2 contents, suggesting a gradual enrichment of heavy Fe isotopes during the evolution of the magma as it ascended to the surface. While the Sr – Nd – Pb – Hf isotopic compositions do not vary significantly, suggesting that the different samples are the products of different degrees of crystal fractionation of comagma. The fractional crystallization of olivine, pyroxene, and ilmenite minerals, which enrich in light Fe isotopes, resulted in the gradual increase in Fe isotopic values of magma during its evolution. The dacites and rhyolites from the southernmost Okinawa Trough have the similar δ56Fe values with the basaltic andesite and the basalt from the SOT and MOT, accompanied by significantly lower Nd and Hf isotope ratios relative to basalts, reflecting that the contamination of crustal materials would not change the magma in Fe isotope compositions evidently. Compared with the MOT, the volcanic rocks from the SOT was more affected by subduction components on their underlying mantle, and those from the southernmost experienced more contamination by crustal materials in the evolving magma. [ABSTRACT FROM AUTHOR]

Transport properties of silicate melts control magma ocean dynamics on the early terrestrial planets and rocky exoplanets. Here we calculate the viscosity (transport of momentum) of peridotite liquid at potential magma ocean conditions (0–159 GPa, 2,200–6,000 K) using ab initio molecular dynamics simulations. We find that, unlike MgSiO3 or basaltic melts, the viscosity of the highly depolymerized peridotite liquid (a) increases monotonically with pressure without an anomalous drop and (b) is lower than those of other melts over the entire mantle pressure range. Low viscosity would promote fractional crystallization in a less polymerized magma ocean and thus contribute to mantle heterogeneity from its earliest stage. Given the compositional dependence of magma ocean properties, emphasis on multicomponent bulk silicate Earth‐like composition, instead of simple end‐members, are rendered necessary, in order to better understand high‐energy planetary accretion processes and their aftermaths. Plain Language Summary: In the aftermath of impacts, widely envisaged scenarios taking place on early terrestrial planets, the silicate mantle (i.e., rocks) experiences extreme temperatures that lead to extensive melting (i.e., magma ocean) on those planets. According to our supercomputer simulations, the viscosity of a magma depends on its composition, which can be as fluid as water for a silicate Earth‐like composition. Low viscosity entails vigorous convection, promoting fractional crystallization in the magma ocean. In light of this early differentiation process, mantle heterogeneity observed in the present‐day Earth may be remnants of the solidified magma ocean that survived over geologic time. Key Points: The viscosity of peridotite liquid is calculated at probable magma ocean conditions up to 159 GPa and 6,000 KIsothermal viscosities of peridotite liquid increase monotonically with pressure and are constantly lower than those of MgSiO3 liquidLow viscosity points to turbulent mixing in a magma ocean and favors fractional crystallization during its solidification [ABSTRACT FROM AUTHOR]

The Palaeocene granites of Dawei and the Eocene granites of Mawchi both host large‐ to medium‐scale Sn–W deposits and represent two metallogenically prominent segments of the SE Asian tin belt in Myanmar. Combined with previous geochemical data, new whole‐rock elemental and isotope analyses of tin‐mineralized granites were obtained to provide insights into sources involved in the formation of these granites. Tin granites in both regions are highly siliceous (76–80 wt%), peraluminous (A/CNK = 1.02–1.32), depleted in Sr, Ba, Zr and Ti but elevated in Li, Sn, Rb, Pb and U. The highly evolved nature of these granites is emphasized by their high Y/Ho (33–49) ratios as well as low Nb/Ta (1–11) and Zr/Hf (8–24) ratios. The chondrite‐normalized REE patterns, with M‐type tetrad effects (TE1,3 = 1.04–1.16) and strongly negative Eu anomalies (0.01–0.34), point to fractional crystallization of feldspars and other accessories during the evolution of the parental magma and are also indicative of the magmatic to hydrothermal transition that resulted in the pervasive mineralization of these bodies. The Pb isotopic compositions are variably enriched, with age‐corrected 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values ranging from 18.620 to 18.898, 15.728 to 15.770, and 38.288 to 39.402, respectively, all of which point to derivation from evolved crustal material. This is consistent with their low ɛNd(t) and ɛHf(t) values of −10.11 to −11.29, and −5.86 to −8.93, respectively. Collectively, these data suggest that crustal melting, fractional crystallization and late‐stage magma–fluid interactions all played important roles in the generation of the tin‐mineralized granites of Myanmar. [ABSTRACT FROM AUTHOR]

The origin of the wide range of sulfur isotope compositions (i.e., δ34S) measured in arc rocks remains debated. While the observed δ34S variability has been attributed to slab-related fluids that flux the sub-arc mantle, others have argued that it primarily reflects crustal-derived processes by some combination of magmatic differentiation, country rock assimilation, and/or degassing. Here, we present new whole rock sulfur isotopes for the Late Cretaceous Bear Valley Intrusive Suite (BVIS) that represents a continuous arc crustal section in the southern Sierra Nevada Batholith, exposing lower crustal mafic cumulates and cogenetic mid-upper crustal tonalites. Our data reveal a range of δ34S-depleted values (–1.2 to − 5.1‰) for the BVIS with overlapping δ34S between mafic cumulates and tonalites. Complementary δ34S measurements of structurally concordant metasedimentary pendants indicate δ34S-depleted values (–11.5 to − 5.2‰) for deep metasedimentary rocks compared to δ34S-enriched values (+ 1.6 to + 6.4‰) for shallower ones. Quantitative mixing models suggest that assimilation of crustal-derived sulfur from metasedimentary rocks in the lower crust can account for the δ34S-depleted values in the BVIS, whereas assimilation of shallower ones is unlikely. Sulfur degassing modelling indicates that the range of δ34S-depleted values observed within mid-upper crustal tonalites can be reproduced by degassing ~60–80% of the initial melt sulfur at fO2 ≤ FMQ + 1 with initial H2O content of 10–12 wt%. Finally, the identical ranges of δ34S values within the tonalites and mafic cumulates argue for limited sulfur isotope fractionation related to magmatic sulfide immiscibility. Although assimilation, magma degassing and sulfide immiscibility are not mutually exclusive during crustal magmatic processes, field, thermal and geochemical evidence favor lower crustal-derived sulfur assimilation as the primary mechanism to explain the range of δ34S- depleted values within the mafic cumulates, which are ultimately inherited by the derivative tonalitic melts. Overall, this study emphasizes that deep crustal magmatic processes can severely influence the early δ34S evolution of arc magmas. [ABSTRACT FROM AUTHOR]

If primitive arc magmas are primarily oxidized or if they acquire their oxidizing character during crustal evolution remains debated. Mineral-melt V partitioning is extremely redox sensitive and has the potential to resolve this debate, but critical low-temperature, hydrous experimental partitioning data are limited. We present new experimental V partitioning data for olivine-melt, spinel-melt, and clinopyroxene-melt based on the ≤ 1200 °C, hydrous basalt phase equilibrium experiments of Pichavant et al. (Geochim Cosmochim Acta 66:2193–2209, 2002) and Pichavant and Macdonald (Contrib Mineral Petrol 154:535–558, 2007). Combined with published experimental data, we use our olivine-melt V partitioning coefficients to show that—contrary to previous conclusions—hydrous melt composition, i.e. melt H2O concentration in addition to the concentration of other melt components, affects V partitioning and thus calculated fO2, systematically overestimating fO2 for olivine-melt equilibrated at high melt H2O concentration. False absolute fO2 values and false oxidation or reduction trends may be inferred. Based on these findings, we have calibrated a set of new olivine-melt oxybarometers applicable to hydrous arc magmas partially crystallized at ~ 1025–1350 °C. In a case study on a high-Mg basalt from St. Vincent, Lesser Antilles, we show that olivine-melt V oxybarometry records oxidizing near-liquidus conditions (~ QFM + 1.8) and possibly limited oxidation (~ 0.3 log units) during intermittent crustal magma storage. [ABSTRACT FROM AUTHOR]

This research paper discusses the construction of novel and better quantum codes from the direct product of t -copies of ring R (discussed in Section 2), using cyclic codes over R by employing the CSS construction technique. Here, we present an overview of the structure and essential properties of a ring R. Furthermore, we analyze the distance-preserving nature of the Gray map in Subsection 2.1. Here, we also investigate maximum distance separable (MDS) codes by using the concept of quantum singleton defect (QSD), which indicates the overall quality of codes. To demonstrate the practicality of our findings, we provide illustrative examples implemented using the Magma software. [ABSTRACT FROM AUTHOR]

This paper presents a model of the formation of a multiphase Akzhailau granitoid massif formed within a Caledonian block of the Earth's crust in the Hercynian time. This work is based on the results of major and trace element composition, geochronological, mineralogical and isotope-geochemical studies. Three stages of the formation of the Akzhailau massif are distinguished, which differ significantly from the previously accepted concepts about the multicomplex and polychronous origin of this intrusion: (1) the formation of moderately alkaline A2-type leuсogranites (308–301 Ma); (2) intrusion of monzodiorites into the base of leucogranites (~295 Ma), increasing degree of partial melting of protoliths with the formation of syenites and moderately alkaline granites of I-type (294–292 Ma); (3) intrusion of dikes and small bodies of alkaline ferroeckermannite A1-type leucogranites in the west and north of massif (~289 Ma). The Akzhailau massif was formed within about 15 Myr in the middle–upper crust through the interaction of plume-related subalkaline basitic magmas with metamorphosed crustal protolith of the orogenic structure. [ABSTRACT FROM AUTHOR]

Olivine from the dunite of the Guli pluton crystallized from olivine–melanephelinite magma at temperatures above 1260°C according to the melt inclusion study. The melts were enriched with volatile components (S, CO2, F, H2O, slightly Cl) and contained high amount of incompatible elements. In addition, olivine hosts sporadic inclusions of picrite-basalt composition, which are close to picrite–meimechite melts preserved in chromite from dunite according to literature data. This suggests the influx of picrite–meimechite melts and their mixing with melanephelinite magma during the formation of dunites in the magma chamber. Based on the indicator ratios of incompatible elements, these melts and melanephelinite magma had different sources, which were located in undepleted mantle at different depths and derived through different degree of partial melting. [ABSTRACT FROM AUTHOR]

There are several large intrusions composed of 60–90% leucogranites within Eastern Kazakhstan. The age of intrusions was determined that allows to conclude about the two stages of leucogranite intrusive magmatism: (1) in the Early Permian and (2) in the Early Triassic. Their formation occurred in an post-orogenic or intraplate geodynamic setting. The geochemical features of the leucogranites were considered that allows to conclude about the petrogenetic mechanisms of leucogranite magmas forming. They were formed as a result of partial melting of crustal substrates under the thermal influence of mafic magmas. Geochemical differences of leucogranites were due to different compositions of crustal substrates and different degrees of their melting. [ABSTRACT FROM AUTHOR]

The Devonian Rudniy intrusion is a composite magmatic body comprising two gabbroid units. Located in the Tsagaan-Shuvuut ridge in NW Mongolia, it is the only one known to contain disseminated sulfide Ni-Cu-PGE minerals out of numerous gabbroid intrusions surrounding the Tuva depression. The ore occurs as disseminated sulfide globules made of pyrrhotite, pentlandite, chalcopyrite, and cubanite, confined to a narrow troctolitic layer at the margins of a melanogabbro, at the contact with a previously emplaced leucogabbro. Globules generally display mantle-dominated sulfur isotopic signatures but show variable metallogenic and mineralogical characteristics, as well as notably different sizes and morphologies reflecting variable cooling and crystallization regimes in different parts of the intrusion. Sulfides from the chilled margin of the melanogabbro are surrounded and intergrown with volatile-rich (i.e., CO2-, H2O-, F-, and Cl) phases such as calcite, chlorite, mica, amphibole, and apatite. Based on the mineralogical and textural relationships of volatile-rich phases with sulfides, we argue that this assemblage represents the product of the crystallization of volatile-rich carbonate melt immiscible with both silicate and sulfide liquids. We put forward the hypothesis that volatile-rich carbonate melt envelops sulfide droplets facilitating their transport in magmatic conduits and that this process may be more widespread than commonly thought. The smaller sulfide globules, which are interpreted to derive from the breakup of larger globules during transport and emplacement, do not display an association with volatile-rich phases, suggesting that the original carbonate melt could have been detached from them during the evolution of the magmatic system. Variable rates of crystallization may have been responsible for the observed disparities in the mineralogical and metallogenic characteristics of different sulfide globules entrained in the Rudniy intrusion. [ABSTRACT FROM AUTHOR]

The gravity and gradient anomalies contain valuable information about the underground geological structures at various depths. Deep and shallow buried source bodies are able to be identified through multi-scale field separation processes, and visual comprehensions of geological structures can be obtained via 3D density inversion techniques. In this study, we propose an improved 3D imaging strategy based on gravitational field separation using the preferential continuation filter. This strategy incorporates the relationship between spectral features and buried depths of source bodies, allowing for a one-step transformation from planar gravity and full-tensor gradient field observations to a 3D density structure in the wave-number domain. Synthetic tests validate the effectiveness and robustness of the gravity and gradient imaging approaches, highlighting their advantages in high vertical resolution and low computational requirements. Nonetheless, it should be noted that the imaging effects of horizontal gradients Γ x x and Γ y y are unsatisfactory due to their weak noise resistance. Thus, they are not suitable for real data applications. The other imaging approaches are further applied to recover the subsurface 3D density structure beneath the Weishan cone in Wudalianchi Volcanic Field, Northeastern China. Our results provide insights into the possible location and shape of the low-density magma chamber. Also, the potential presence of partial melts is inferred and supported from a gravity perspective. The primary advantage of these approaches is their ability to generate a reasonable geological model in scenarios with limited prior information and physical property constraints. As a result, they have significant practical value in the field of applied geophysics, including mineral exploration and volcanology studies. [ABSTRACT FROM AUTHOR]

The geochemical monitoring of volcanic activity today relies largely on remote sensing, but the combination of this approach together with soil gas monitoring, using the appropriate parameters, is still not widely used. The main purpose of this study was to correlate data from crater gas emissions with flank emissions of soil gases at Mt. Etna volcano from June 2006 to December 2020. Crater SO2 fluxes were measured from fixed stations around the volcano using the DOAS technique and applying a modeled clear-sky spectrum. The SO2/HCl ratio in the crater plume was measured with the OP-FTIR technique from a transportable instrument, using the sun as an IR source. Soil CO2 efflux coupled with the 220Rn/222Rn activity ratio in soil gases (named SGDI) were measured at a fixed monitoring site on the east flank of Etna. All signals acquired were subject both to spectral analysis and to filtering of the periodic signals discovered. All filtered signals revealed changes that were nicely correlated both with other geophysical signals and with volcanic eruptions during the study period. Time lags between parameters were explained in terms of different modes of magma migration and storage inside the volcano before eruptions. A comprehensive dynamic degassing model is presented that allows for a better understanding of magma dynamics in an open-conduit volcano. [ABSTRACT FROM AUTHOR]