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Geochemical overview of Aso-4 plagioclases from crystal-rich scoria and crystal-poor, silicic pumice. (A) Histogram of An-contents of Aso-4 plagioclase. An contents for plagioclases overlap in the range of An30–75; early-erupted plagioclases tend to cluster around lower An contents while plagioclases from late-erupted units tend to shift toward higher An contents. Crystals with An > 75 are identified as recharge crystals based on test for equilibrium (following Putirka, 2016). (B) Binary plot of SrO vs. An-content displaying compositional overlap of plagioclase from early-erupted pumice and late-erupted scoria, with a tendency toward more mafic compositions in plagioclase from crystal-rich scoria. (C) Backscattered image of a plagioclase from late-erupted scoria exhibiting a sieved texture core overgrown by an euhedral rim of An60 and clear Sr enrichment within the crystal rim. Measurement errors are smaller than the symbol.
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The Aso-4 caldera-forming event (86.4 ± 1.1 ka, VEI-8) is the second largest volcanic eruption Earth experienced in the past 100 ka. The ignimbrite sheets produced during this event are some of the first ever described compositionally zoned pyroclastic flow deposits exhibiting clear compositional, mineralogical and thermal gradients with stratigrap...
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... However, many large-volume silicic eruption deposits are characterized by stark heterogeneities in composition, and crystal content, with deposits becoming progressively more crystal rich from early-to late-erupted material ("zoned ignimbrites"; e.g, (Bachmann & Bergantz, 2008;Hildreth, 1981;Huber et al., 2012;Wolff et al., 1990). The crystal-rich parts of the deposits are typically interpreted as the crystal cumulate left behind after extraction of the melt-rich pocket forming the early-erupted material, indicating that crystal-melt separation is common within these magma chambers Deering et al., 2011;Keller et al., 2021;Pamukcu et al., 2013;Wolff et al., 2020). In our model, we assume that once the chamber reaches a crystal fraction of 0.5, it can no longer erupt. ...
Magmatic volatiles drive pressure, temperature, and compositional changes in upper crustal magma chambers and alter the physical properties of stored magmas. Previous studies suggest that magmatic H2O content influences the growth and longevity of silicic chambers through regulating the size and frequency of eruptions and impacting the crystallinity‐temperature curve. However, there has been comparatively little exploration of how CO2 impacts the evolution of magma chambers despite the strong influence of CO2 on H2O solubility and the high concentrations of CO2 often present in mafic systems. In this study, we integrate the thermodynamic effects of dissolved and exsolved H2O and CO2 with the mechanics of open‐system magma chambers that interact thermally and mechanically with the crust. We applied this model to investigate how intrinsic variations in magmatic H2O‐CO2 content influence the growth and longevity of silicic and mafic magma chambers. Our findings indicate that even with a tenfold increase in CO2 content (up to 10,000 ppm), CO2 plays a minimal role in long‐term chamber growth and longevity. While CO2 content affects the magma compressibility, the resulting changes in eruption mass are balanced out by a commensurate change in eruption frequency so that the time‐averaged eruptive flux and long‐term chamber behavior remain similar. In contrast, H2O content strongly influences chamber growth and longevity. In silicic systems, high H2O contents hinder magma chamber growth by increasing the total eruptive flux and steepening the slope of the crystallinity‐temperature curve. In mafic systems, high H2O contents promote magma chamber growth by flattening the slope of the crystallinity‐temperature curve.
... They are interpreted to have formed in a heterogeneous upper-crustal magma reservoir consisting of crystal-poor rhyodacitic melt caps extracted from its complementary crystal cumulate mush. Prior to the eruption, voluminous hot recharge initiated melting of the cumulate mush and induced magma hybridization, leading to reservoir reactivation and compositional stratification of the magmas (Lipman, 1967;Kaneko et al., 2007;Keller et al., 2021). ...
... The Aso-4 age is taken from Albert et al. (2019;40 Ar/ 39 Ar dating on hornblende), while the intercaldera ages are from Hoshizumi et al. (2022;loess chronometry) and Smith et al. (2013; lake sediment chronometry). scoria (Keller et al., 2021). Crystal-rich scoria erupted at the end of the Aso-4 eruptive sequence relates to rejuvenated cumulate material, as described by Keller et al. (2021). ...
... scoria (Keller et al., 2021). Crystal-rich scoria erupted at the end of the Aso-4 eruptive sequence relates to rejuvenated cumulate material, as described by Keller et al. (2021). All Aso-4 samples contain plagioclase, ortho-and clinopyroxene, Fe-Ti oxides, and additional amphibole, while pre-Aso-4 units have a similar mineral assemblage comprising plagioclase, ortho-and clinopyroxene, Fe-Ti oxides and in the case of Aso-Y and Aso-4X additional biotite (Table 1). ...
... The white dots indicate an average of data. Data is from this study for Krakatau, Vidal et al. (2015) and Métrich et al. (2018) for Rinjani, Forni et al. (2016, Forni et al., 2018 and references therein for Campi Flegrei, Miyabuchi (2009) and Keller et al. (2021), Keller et al. (2023) for Aso. ...
Understanding the evolution of magma storage conditions on volcanoes which have had more than one caldera-forming eruption (CFE) is important to know about past and present conditions, as a key to forecast future potential hazards. Krakatau volcano is characterized by cyclic phases of growth and destruction of the edifice. A volcanostratigraphic study identified three eruptive periods: Old Krakatau, Young Krakatau, and Anak Krakatau. The Old and Young Krakatau periods ended with the first and second CFE respectively. Due to its permanent activity and edifice evolution, Krakatau poses a high risk on the surrounding inhabited islands. In this study, we combined geochemistry, rock magnetic, and petrology to infer the evolution of magma storage conditions from Old to Anak Krakatau periods. This study is the first to report on the chemical and rock magnetic characteristics, as well as storage system conditions of Old Krakatau and its relation to the ongoing evolution of Krakatau. Our data show that: 1) Old and Young Krakatau magma storage regions are shallow (within the upper 3 km), contain more differentiated magmas, from which the Old Krakatau magmas may be less oxidized and had lower temperatures than Young Krakatau; 2) Anak Krakatau magma storage is deeper (up to 26 km), less differentiated, and erupted hotter but more reduced compared to Old and Young Krakatau. The Old and Young Krakatau lavas were the products of pre-CFE and their chemical characteristics are included at maturation phase, whereas the Young Krakatau pumice samples were the product of the second CFE. Lastly, the post-second CFE activity of AK is currently in an incubation phase and represented by mafic products of frequent and small eruptions. Knowing that the volcano has experienced maturation and CFE phases in the past, the current AK may evolve to those phases in the future.
... Cumulate melting has become increasingly recognized as a major component in the generation of compositional zonation observed in numerous ignimbrites Foley et al., 2020;Forni et al., 2016Forni et al., , 2018bKeller et al., 2021;Wolff et al., 2015Wolff et al., , 2020. The association of textural evidence for melting and geochemical evidence for an origin by crystallization-differentiation within the same deposit is the key observation allowing compositional zonation to be attributed to cumulate melting (Wolff et al., 2015). ...
... The point we make here is that many observed styles of zonation do not necessarily require significant mass transfer from mafic recharge. However, often the mafic recharge magma is indeed erupted, to produce an ensemble of a felsic component with variable trace elements plus the mafic component, often mingled or mixed to produce banded and hybrid rocks, for example in Tenerife (Edgar et al., 2002;Sliwinski et al., 2015), at Campi Flegrei (Di Salvo et al., 2020;Forni et al., 2018b), and Aso (Keller et al., 2021). In magmatic systems approaching the granite minimum where cumulate melting is favored, likely cumulates will be dominated by feldspar and quartz with other phases occurring in minor proportions. ...
... The Aso-4 eruption represents the second largest volcanic event Earth has experienced within the last 100 ka with an extruded volume > 900 km 3 (Takarada and Hoshizumi, 2020). The compositionally zoned (basalt to rhyolite) Aso-4 ignimbrite sheets are interpreted to be formed in a heterogeneous upper crustal magma reservoir, consisting of crystal-poor rhyodacitic melt caps within its complementary crystal mush, partly affected by recharge and magma mixing (Kaneko et al., 2007;Keller et al., 2021;Lipman, 1967). Similar compositional zonations from mafic to silicic magma were also observed in the deposits of the Aso-3 and Aso-2 eruptions, implying recurring magmatic processes within the plumbing system (Kaneko et al., 2015). ...
... The authors subdivided the sequence in five stages according to magma composition and erupted volume of the magmas. In stage 1, right after the Aso-3 eruption (133-114.1 ka), eruptions of predominantly mafic material are observed, which become (Keller et al., 2021). The map was produced with the Web Map Service of the Geological Survey of Japan. ...
... To investigate geochemical variations in the cycle between the Aso-3 and Aso-4 CFE a total of 15 samples of fresh, juvenile pumice were collected from nine different locations associated with the Aso-3, Aso-4, intercaldera and post-Aso-4 eruptions (Fig. 1A). Aso-4 early-erupted samples relate to crystal-poor, silicic pumice, and Aso-4 late-erupted samples correlate with crystal-rich scoria described in Keller et al. (2021), which are associated with units 4I-1 (non-welded pumice flow), 4I-3 (non-to-weakly-welded scoria flow) and 4II-2 (densely-welded silicic pyroclastic flow) described in Kaneko et al. (2007). Similarly, Aso-3 early-erupted samples relate to aphyric pumice found in units 3A and 3B described in Kaneko et al. (2015) erupted at the beginning of the Aso-3 eruptive sequence, while Aso-3 late-erupted material correlates with aphyric scoria found across units 3A and 3B (Kaneko et al., 2015) erupted at a later stage of the Aso-3 sequence. ...
... During such events of magma withdrawal, the upper crystalpoor lenses erupt from the magma chamber and the leftovers are mostly constituted by a crystal-rich layer containing minor residual interstitial melts. Evidence of these processes is represented by an initial pumicebearing deposit with high-SiO 2 rhyolitic composition exhibiting low contents of crystals, progressively varying in crystallinity and bulk composition to deposits of relatively high crystal contents and with compositions ranging from SiO 2 -poor rhyolites to trachytes/trachydacites and dacites (e.g., Deering et al., 2011;Pamukcu et al., 2013;Keller et al., 2021). This specific succession can be recognized in the CACB, in which post-collapse silicic domes were emplaced just after the ignimbritic event(s), occupying the rectangular limits of the basin. ...
The Campo Alegre-Corupá Basin (CACB) records a well-documented sequence of volcano-sedimentary episodes associated with specific periods of crustal extension during the late-convergent to post-collisional tectonic stages of the consolidation of Western Gondwana. Two main volcano-sedimentary stages were detailed through stratigraphic and lithofaciological studies, combined with whole-rock geochemistry and zircon U-Pb-Hf analysis, resulting in a more complete understanding of the tectono-magmatic cycles and volcanological evolution of the CACB. During the Basin Stage (605-590 Ma), regional collisional tectonics was responsible for initiating the basin as a syn-orogenic rift, during which the sedimentary cycle progressed from alluvial fans at the northern limit of the basin to braided rivers and into a lake to the south. U-Pb geochronology and Lu-Hf isotope signatures of detrital zircon revealed that the sediments were mainly derived from the Paleoproterozoic basement of the Luis Alves Terrane, which constitutes the direct basement of the CACB, with contributions from the nearby Piên Magmatic Arc and possibly from the Curitiba Terrane to the North. The sedimentary strata were progressively covered by transitional to mildly alkaline OIB-like basalts, occurring mostly as lava flows with structural aspects suggestive of subaqueous to subaerial environments, interbedded with trachydacites and surge-like pyroclastic deposits. Large volumes of widespread and densely-welded to rheomorphic ignimbrite sheets within the CACB attest to a second infilling period corresponding to the Caldera Stage (583-577 Ma). This stage was inaugurated by the outpouring of trachytic and very subordinated IAB-like basaltic lava flows at ~583 Ma. The caldera eruption seems to have been initiated by the production of pumiceous fallouts during an early Plinian-like period of decompression of shallow magma chambers at ~580 Ma, during which the rift-related structural framework of the Basin Stage probably controlled the collapse of a graben-like caldera. Compositional and isotopic signatures suggest lithospheric mantle sources for the magmas from both volcanic stages and support a connection between basic-intermediate and silicic rocks from both bimodal associations. They also suggest a cogenetic nature between the silicic rocks from the Caldera Stage and the A-type granitoids from the nearby plutonic Graciosa Province.
... Theoretically, geochronological data from the past~200 ka can be determined by a variety of techniques, among which the most commonly applied are radiocarbon dating (e.g., Stuiver and Pearson 1993, Okuno and Nakamura 2003, Margari et al. 2007, d 18 O isotopic stratigraphy (e.g., Paterne et al. 1986, Aoki 2008, Grossman and Joachimski 2020, 230 Th-238 U disequilibrium dating of zircon crystals (e.g., Eggins et al. 2005, Guillong et al. 2016, Popa et al. 2020a, (U-Th)/He dating of zircon crystals (e.g., Farley 2002, Danisik et al. 2017) and 40 Ar/ 39 Ar dating of K-bearing phases (e.g., Renne et al. 1998, McDougall andHarrison 1999). However, many volcanic deposits, including those generated by a large number of super-eruptive events are too old for radiocarbon dating ( [ 50,000 years), and do not contain commonly datable minerals such as K-bearing phases or zircon (e.g., the Aso (Keller et al. 2021) or Aira calderas (Geshi 2020)). The solubility of these "easily datable" minerals is strongly controlled by magma storage conditions such as temperature, dissolved water content and melt composition (Nekvasil 1992, Boehnke et al. 2013, Szymanowski et al. 2020. ...
... With an extruded volume [ 900 km 3 , the Aso-4 caldera-forming eruption is classified as the second largest volcanic event Earth has experienced in the last 100 ka (Takarada and Hoshizumi 2020). The ignimbrite sheets produced during this eruption are compositionally zoned, ranging in bulk rock composition from basalt to rhyolite (Lipman 1967, Hunter 1998, Kaneko et al. 2007, Ishibashi et al. 2018, Keller et al. 2021. Our recent re-evaluation of the deposits suggests the origin of this compositional zonation to be the evacuation of a heterogeneous upper crustal reservoir, consisting of crystal-poor rhyodacitic melt caps within its complementary cumulate mush, partly affected by recharge (Keller et al. 2021). ...
... The ignimbrite sheets produced during this eruption are compositionally zoned, ranging in bulk rock composition from basalt to rhyolite (Lipman 1967, Hunter 1998, Kaneko et al. 2007, Ishibashi et al. 2018, Keller et al. 2021. Our recent re-evaluation of the deposits suggests the origin of this compositional zonation to be the evacuation of a heterogeneous upper crustal reservoir, consisting of crystal-poor rhyodacitic melt caps within its complementary cumulate mush, partly affected by recharge (Keller et al. 2021). The Aso-4 eruption age was calculated based on 40 Ar/ 39 Ar dating of hornblende crystals to 86.4 AE 1.1 ka (2s, Albert et al. 2019). ...
Precise age determinations of volcanic deposits from the Late Pleistocene and Holocene are fundamental for hazard assessment. Retrieving accurate radiogenic ages typically relies on analysing specific minerals (such as zircon or sanidine), which are in many cases lacking in the deposits. We present a new 230Th‐238U disequilibrium dating method by LA‐ICP‐MS for inclusion‐bearing ilmenite, and discuss its details and challenges. The technique is tested on ilmenites from the 86.4 ± 1.1 ka Aso‐4 super‐eruption, Japan, and from the Lower Pumice (63.1 ± 4.7 ka) and Upper Pumice (58.4 ± 2.7 ka) eruptions of Nisyros volcano, Greece. Ilmenites of the Aso‐4 eruption produce well‐defined global isochrons yielding ilmenite crystallisation ages of 89 ± 10 ka (2s) and 81 ± 15 ka (2s). Two‐point isochron model ages from the Nisyros eruptions produce youngest population ages of 66.3 ± 5.7 ka (1s) for the Lower Pumice and 61.2 ± 4.4 ka (1s) for the Upper Pumice. The age determinations obtained during this study are compatible with data reported from conventional techniques. These results demonstrate the applicability of this new method to date young volcanic deposits in a quick, reproducible way, and without relying on zircon or K‐bearing phases.
... Petrological evaluation of the magma storage conditions of past caldera-forming eruptions is an important alternative approach for constraining the possible pre-eruptive depth of voluminous silicic magma chamber. Pre-eruptive conditions have been widely investigated for caldera-forming eruptions at various volcanoes such as Campi Flegrei (Marianelli et al., 2006), Santorini (Cadoux et al., 2014), Taupo Pamukcu et al., 2020), Toba (Chesner & Luhr, 2010), Aira (Geshi et al., 2020), Aso (Keller et al., 2021;Ushioda et al., 2020), and Long Valley (Anderson et al., 1989;Gualda & Ghiorso, 2013). Petrological barometers based on the solubility models of H 2 O and CO 2 in the melt (e.g., Newman & Lowenstern, 2002), plagioclase-melt hygrometers (Waters & Lange, 2015), amphibole compositions particularly aluminum (Anderson & Smith, 1995;Ridolfi & Renzulli, 2012), and the position of quartz-feldspar saturation surface calculated by rhyolite-MELTS are typically used to estimate the pre-eruptive pressure of silicic magmas. ...
Towada volcano is an active volcano in northeast Japan, that caused two large caldera‐forming eruptions at 36 ka (episode N) and 15.5 ka (episode L). Petrological analyses and phase equilibrium experiments were performed on silicic endmember rhyolitic pumices from these two eruptions to constrain the pre‐eruptive magma storage conditions. A common mineral assemblage of plagioclase + orthopyroxene + clinopyroxene + magnetite + ilmenite was observed in both eruptions, whereas amphibole (hornblende) was observed only in the episode L pumice. Mineral thermometers presented temperatures of 832–883°C and 802–870°C for the episode N and L pumices, respectively, with an oxygen fugacity of ∼nickel–nickel oxide (NNO) + 1 in log units. The water‐saturation pressures evaluated using the plagioclase‐melt hygrometer were in the range of ∼100–200 MPa. Experiments at 100–350 MPa and 825–900°C under water‐saturated and NNO‐buffered conditions successfully reproduced the mineral assemblages in both pumices, except for magnetite. Further constraints by phase compositions and phase proportions resulted in the preferred storage conditions of 840–850°C and 150–170 MPa for both eruptions. The emergence of hornblende in the episode L magma was likely caused by the higher CaO content compared to the episode N magma and not by the difference in the storage conditions. The storage depths at ∼5–7 km coincide with the depth of the low seismic velocity beneath the present Towada volcano, suggesting possible magma accumulation at the same depths as in the past caldera‐forming eruptions.
Carboniferous plutonic activity in the Sierra Pampeanas region of NW Argentina resulted in the emplacement of several magma bodies at shallow levels, while contemporaneous volcanism was primarily recorded in the neighboring Puna region. One of these plutons, known as Los Árboles in the Sierra de Fiambalá, formed through two periods of significant felsic magma additions (326–322 Ma) and the subsequent development of tuffisites associated with subvolcanic dikes of predominantly mafic composition (315 ± 3 Ma). The presence of 2–5 m wide tuffisite dikes, indicating subvolcanic depths (~ 1 km), provides an excellent opportunity to understand the connections between plutonic and volcanic processes. Our study reveals that for felsic magma batches to reach these subvolcanic depths, the input of synchronous mafic magmatism is a critical step. The Los Árboles pluton grew through alternating stages of accommodation by sheet intrusions, which subsequently merged during incubation into larger magma bodies with dominant lateral growth, forming a ductile halo. Both mildly alkaline mafic dike swarms and tuffisites intrude the pluton. The tuff-filled clastic dikes exhibit a variety of textural features and bulk rock compositions that indicate processes of late-stage heating and low-temperature remelting (~700 °C) of the host granite. Our findings document that magmatic plumbing systems, driven by mantle processes, can reach subvolcanic levels, induce brittle-ductile transitions in the host rock, and persist in a cold storage stage for millions of years, with temperatures below the granite solidus, and be potentially eruptive through defrosting.
During the Early- to Mid-Miocene, several large-volume explosive volcanic eruptions fed by high-silicic magmas occurred contemporaneously with the lithospheric extension beneath the Pannonian Basin, eastern-central Europe. The Tokaj Mts. volcanism occurred in a thinning continental lithosphere regime at the final stage of the subduction process. Using high-precision zircon U-Pb dating, four major explosive eruption events were distinguished. Among them the 13.1 Ma Sátoraljaújhely and the 12.0 Ma Szerencs eruptions could have yielded large amount of volcanic material (possibly > 100 km3) and they were associated with caldera collapse as shown by the several hundred-metre-thick pyroclastic deposits and the long (>100 km) runout pyroclastic flow in case of the 13.1 Ma eruption. The 12.3 Ma Hegyköz and the 11.6 Ma Vizsoly eruptions were relatively smaller. The volcanic products can be readily distinguished by zircon and glass trace elements and trace element ratios, which can be used for fingerprinting and to correlate with distal deposits. The Rb, Ba, Sr content and strong negative Eu-anomaly of the glasses reflect extreme crystal fractionation, particularly for the Szerencs rhyolitic magma. The silicic volcanic products of the Tokaj Mts. show compositional similarities with the so-called ‘dry–reduced–hot’ rhyolite type consistent with an origin in an extensional environment, where the primary magmas were formed by near-adiabatic decompression melting in the mantle with subordinate fluid flux. In contrast, some of the older Bükkalja rhyolitic magmas evolved via more hydrous evolutionary paths, where amphibole played a role in the control of the trace element budget. The significant increase of zircon Hf values from -8.8 to +0.2 in the rhyolitic pyroclastic rocks of Tokaj Mts. with time implies that mantle-derived magmas became more dominant. This can be explained by the specific tectonic setting, i.e. the final stage of subduction when the descending subducted slab became almost vertical, which exerted a pull in the upper lithosphere leading to thinning and accelerated subsidence as well as asthenospheric mantle flow just before the slab detachment.
