Contributions to Mineralogy and Petrology最新文献

{"title":"Diffusion of silicon in olivine and forsterite: water effect, diffusion laws, and implication for upper mantle rheology","authors":"Emmanuel Gardés,&nbsp;David Gibouin,&nbsp;Bertrand Radiguet,&nbsp;Adrian David,&nbsp;Wilfrid Prellier,&nbsp;Sylvie Demouchy,&nbsp;Katharina Marquardt","doi":"10.1007/s00410-026-02324-x","DOIUrl":"10.1007/s00410-026-02324-x","url":null,"abstract":"<div><p>As the slowest species, the diffusion of silicon controls the deformation of olivine and plays a crucial role in Earth dynamics. The diffusion of silicon in olivine remains controversial as literature diffusivities spread over several orders of magnitude. Furthermore, the extent of enhancement by hydrogen, observed in both olivine and forsterite (iron-free olivine) remains unclear. We performed experiments of volume diffusion of silicon in dry forsterite. We conclude to a significant effect of hydrogen as diffusivities from previous hydrous experiments with up to 1000 wt. ppm H₂O are up to 3 log unit higher than our anhydrous experiments. We analyze our results together with literature data for both forsterite and olivine, and provide laws for silicon volume diffusion in olivine (Ol) </p><p><span>(D_{{Si}}^{{Ol}} = left( {10^{{ - 10.50}} + 10^{{ - 8.78}} C_{{H_{2} O}}^{{0.42}} } right)e^{{ - frac{{316000 + 1460~P}}{{8.314~T}}}} ,)</span> </p><p>and in forsterite (Fo)</p><p><span>(D_{{Si}}^{{Fo}} = left( {10^{{ - 11.64}} + 10^{{ - 9.38}} C_{{H_{2} O}}^{{0.42}} } right)e^{{ - frac{{316000 + 1460~P}}{{8.314~T}}}} ,)</span></p><p>where the diffusivity <i>D</i>_<i>Si</i> is in m²/s, temperature <i>T</i> in K, pressure <i>P</i> in GPa and hydrogen concentration <span>(C_{{H_{2} O}})</span> in wt. ppm H₂O. Hydrogen starts enhancing the diffusion of silicon in olivine at very low concentrations. Diffusivity is already increased by 1.7 log unit at 1 wt. ppm H₂O. Consequently, the diffusion of silicon virtually always occurs in the hydrous regime in mantle olivine. However, variable mantle hydration is not expected to result in drastic variation in diffusivity. A change in olivine hydrogen concentration by a factor 10 modifies diffusivity by a factor 2.6 only. As the deformation mechanism of olivine that should prevail in the asthenosphere, i.e. dislocation creep, depends linearly on silicon diffusivity, olivine viscosity will primarily relate to temperature rather than hydration. </p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 7","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148281234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling alkali-exchange alteration in volcanic glass to obtain original rhyolitic melt compositions and magma storage pressures for the Permian Ora Ignimbrite (Italy)","authors":"Genna R. Chiaro,&nbsp;Guilherme A. R. Gualda,&nbsp;Calvin F. Miller","doi":"10.1007/s00410-026-02335-8","DOIUrl":"10.1007/s00410-026-02335-8","url":null,"abstract":"<div><p>Volcanic glass contains a wealth of information about the magma reservoirs that feed eruptions; however, glass is highly susceptible to secondary processes that modify original compositions. Here, we investigate well-preserved, glass-bearing fiamme from two vitrophyre horizons in the ~ 275 Ma Ora Ignimbrite, a crystal-rich (~ 40%), supereruption-sized (~ 1,300 km³) rhyolite in northern Italy. Glass compositions from these fiamme present a paradox: average K₂O concentrations are too low to crystallize sanidine (2.3—3.6 wt. % K₂O); yet, all fiamme contain abundant euhedral sanidine and have glass compositions strongly depleted in Ba, consistent with sanidine crystallization. Glass data also show a strong negative correlation between K₂O and Na₂O, suggestive of alkali-exchange alteration. We test if 1:1 alkali exchange is a viable mechanism for reduction of K₂O in the Ora glasses. Our results suggest that Ora glasses experienced “reverse” alkali-exchange alteration, in which K is replaced by Na on a 1:1 atomic basis. We generated a series of ten synthetic compositions for each fiamma by starting with the measured composition and iteratively adding 0.5 wt. % K₂O and subtracting 0.33 wt. % Na₂O at each step, following a 1:1 exchange on a molar basis of the oxides. We employ rhyolite-MELTS pressure calculations to find compositions consistent with equilibration between melt, quartz, plagioclase, sanidine, and a fluid phase. By progressively replacing K with Na in the glass compositions, the model returns compositions saturated in quartz + sanidine + plagioclase (Q2F), in agreement with the mineralogy and trace-element geochemistry observed in Ora fiamme. We thus present a new application of rhyolite-MELTS geobarometry that provides estimates of original glass compositions and magma storage pressures from Q2F-bearing rhyolitic fiamme for glass affected by Na–K exchange. These results demonstrate that subtly altered volcanic glass can still provide meaningful information about their magmatic origins.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 7","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02335-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148202941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crystal clots record stable mush conditions and rapid pre-eruptive heating beneath Unzen volcano (1991–1995)","authors":"Kurumi Iwahashi,&nbsp;Atsushi Yasuda,&nbsp;Hidemi Ishibashi,&nbsp;Natsumi Hokanishi","doi":"10.1007/s00410-026-02331-y","DOIUrl":"10.1007/s00410-026-02331-y","url":null,"abstract":"<div><p>The condition of a crystal-rich, mushy magma reservoir plays a crucial role in governing both the processes leading up to volcanic eruptions and the style of eruption that follows. However, constraining its pre-eruptive state remains a significant challenge. In this study, we use crystal clots as a petrological tool to investigate the thermal and compositional evolution of the mushy magma reservoir beneath Unzen volcano prior to the 1991–1995 eruption. We analyzed the major-element compositions of crystals and interstitial glass within the crystal clots, with particular focus on amphibole and plagioclase, to estimate the depth of formation, temperature, and chemical composition of the magma reservoir. Our results indicate that the physicochemical conditions of the mushy reservoir remained largely stable throughout the eruption sequence. Furthermore, textural evidence of amphibole breakdown suggests that heating of the reservoir prior to magma mixing occurred on a timescale of approximately between &gt; 24 h and &lt;  ~ 48 h.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 7","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02331-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148202934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Electrical conductivity of geikielite (MgTiO3) at lunar mantle conditions: the role of metastable defect states and thermal history","authors":"Takashi Yoshino,&nbsp;Daisuke Yamazaki","doi":"10.1007/s00410-026-02333-w","DOIUrl":"10.1007/s00410-026-02333-w","url":null,"abstract":"<div><p>The electrical conductivity of geikielite (MgTiO₃), the Mg endmember of the ilmenite group, was investigated at mantle pressures of 2 and 4.3 GPa and temperatures up to 1850 K using a Kawai-type multi-anvil apparatus. Electrical conductivity increases by more than seven orders of magnitude between 800 and 1700 K and exhibits two distinct conduction regimes separated by a transition at ~ 1500–1700 K. The high-temperature regime is characterized by large activation enthalpies (Δ<i>H</i> ≈ 1.8–2.3 eV), whereas the low-temperature regime shows much lower values (Δ<i>H</i> ≈ 0.19–0.31 eV). Stepwise annealing experiments reveal a pronounced thermal-history dependence: repeated heating to progressively higher maximum temperatures (<i>T</i>_max) produces metastable conductivity states, enhancing low-temperature conductivity by up to six orders of magnitude and systematically reducing activation enthalpy. This behavior indicates activation and freezing-in of defect-related charge carriers. Negative activation volumes further support a hopping-type conduction mechanism. Although Ti³⁺ was not directly detected, the combination of reducing experimental conditions, Al³⁺ impurities (~ 0.35 wt% Al₂O₃), low activation energies, and strong thermal memory is most consistent with small-polaron hopping involving Ti³⁺–Ti⁴⁺ pairs. At lunar core–mantle boundary temperatures, geikielite reaches conductivities of 10¹–10² S/m, exceeding those of olivine and overlapping estimates for the lunar low-velocity zone. Our results demonstrate that solid-state Ti-rich oxides can produce high electrical conductivity without partial melting, providing new constraints on the thermochemical evolution and electromagnetic structure of the lunar interior.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 7","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02333-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148202935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quartz oxygen isotope constraints on the petrogenesis of tourmaline‑rich rocks in the Cornubian Batholith, SW England, with implications for Sn mineralization","authors":"Axel Müller,&nbsp;Martin J. Whitehouse,&nbsp;Ben J. Williamson","doi":"10.1007/s00410-026-02337-6","DOIUrl":"10.1007/s00410-026-02337-6","url":null,"abstract":"<div><p>We investigate the origin and evolution of quartz populations in tourmaline‑bearing rocks of the Cornubian Batholith, SW England, to constrain fluid sources and Sn‑mineralization processes. Our study focuses on massive quartz–tourmaline rocks (MQT) because of their spatial and genetic association with Sn mineralization. MQT occur as small stock‑ to dyke‑like bodies (typically &lt; 300 m) exemplified by Roche Rock and Porth Ledden. Fifteen quartz samples from MQT and comparative quartz from biotite granite, tourmaline granite, pegmatite, tourmaline breccia and veins (Porth Ledden, Porthmeor Cove, Roche Rock, Tresayes, Wheal Remfry) were subject to SEM‑cathodoluminescence and oxygen‑isotope (δ¹⁸O) analysis. SEM‑CL reveals multiple quartz generations: primary magmatic quartz (granites, aplites, MQT), pegmatitic quartz, secondary fracture‑fill quartz, oscillatory hydrothermal overgrowths on magmatic cores (typical in MQT), and complexly zoned vein quartz. All δ¹⁸O values are relatively high (+ 11.5 to + 27.7‰), mostly clustering between + 12 and + 15‰. Magmatic quartz (granites, aplites) range from + 11.5 to + 14.8‰, overlapping pegmatite quartz, implying incorporation into the granitic melts of high‑δ¹⁸O metasedimentary material, consistent with local Devonian metasediments. Hydrothermal quartz spans + 12.7 to + 27.7‰; two anomalously high values (+ 25.6, + 27.7‰) in crystal rims suggest late addition of formation waters. We infer that MQT at Porth Ledden and Roche Rock formed by partial metasomatic replacement of tourmaline granite due to infiltration and entrapment of pneumatolytic, B‑rich fluids in the roof zone. Metasomatism dissolved K‑feldspar, mobilizing K, Rb, Ba, Sr, Cs, Pb and notably Sn, producing cavities later infilled by hydrothermal quartz and tourmaline. A progressive increase in δ¹⁸O from magmatic to late hydrothermal quartz suggests fluid cooling and possible mixing with oxidizing formation waters, rather than a component of meteoric-derived waters that contributed to the precipitation of cassiterite.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 7","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02337-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148202937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Formation of ekanite in “antiskarn” by carbonatitic melt infiltration into charnockitic gneiss, Ampegama, southwestern Highland Complex, Sri Lanka","authors":"K. A. Geeth Sameera,&nbsp;Christoph A. Hauzenberger,&nbsp;G. W. A. Rohan Fernando,&nbsp;Radek Škoda,&nbsp;Prasanna L. Dharmapriya,&nbsp;Chutimun Chanmuang N.,&nbsp;Lutz Nasdala","doi":"10.1007/s00410-026-02330-z","DOIUrl":"10.1007/s00410-026-02330-z","url":null,"abstract":"<div><p>Carbonatitic melt–rock interactions in the crust provide key insights into element mobility, metasomatic processes, and the formation of rare mineral assemblages in high-grade metamorphic terrains. Ekanite-containing calc-silicate dykes at Ampegama, southwestern Highland Complex, Sri Lanka, provide compelling evidence for the interaction of crustal-derived carbonatitic melt with charnockitic gneiss wall rocks, forming an “antiskarn”-type assemblage with ekanite. The dykes, reaching up to 2 m in width, contain variously oriented, irregularly shaped fragments of charnockitic gneiss and form gradational boundaries and reaction zones with wall rocks / enclosed fragments. Field occurrence, textures and variations in mineralogical and chemical composition from charnockitic gneiss over contact zone toward calc-silicate indicate formation of silicate minerals – such as wollastonite, scapolite, clinopyroxene, titanite and ekanite (Ca₂Th_0.9U_0.1Si₈O₂₀) – via metasomatic reactions between carbonatitic melt and wall rocks. Other minerals (e.g. K-feldspar) reflect assimilation from wall rocks. In addition, there are reaction textures that indicate late-stage overprint by CO₂ and F-rich fluids. Unaltered ekanite is bottle-green and transparent and may have gem quality. It is metamict (glassy) but still contains crystallograpically oriented inclusions. The Th-U-Pb age of ekanite, determined by electron probe micro-analyser (EPMA) chemical dating, is 524.4 ± 6.4 Ma (2σ), assigning primary ekanite growth to late-stage regional metamorphism in the Highland Complex. Phase equilibria modeling of the host charnockitic gneiss gives the peak pressure-temperature conditions of ca. 850 ± 50 °C and 6 ± 1 kbar and the carbonatitic melt infiltration has occurred at or close to the peak conditions. Thorium necessary for ekanite formation is proposed to have been taken up from monazite- and thorite-bearing wall rocks by the ascending carbonatitic melt. This melt was likely derived from the anatexis of crustal carbonate rocks during regional metamorphism.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 7","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02330-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148202938","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heterogeneous sources beneath a mature plumbing system in the Aegean arc: evidence from the magma evolution of the Milos volcanic system","authors":"Anna Grosche,&nbsp;Karsten M. Haase,&nbsp;Reiner Klemd,&nbsp;Panagiotis C. Voudouris","doi":"10.1007/s00410-026-02334-9","DOIUrl":"10.1007/s00410-026-02334-9","url":null,"abstract":"<div><p>The Aegean arc is known for its along-arc geochemical variations due to different mantle sources, subducted sediment input, and distinct magma storage and eruption conditions. In contrast to the other Aegean arc volcanoes, the Milos volcanic system is dominated by intermediate to felsic volcanic products, suggesting an extensive magma evolution during ascent through the arc crust. New trace element and Sr-Nd-Pb isotope data of lavas from Milos compared to the other islands indicate the presence of a more depleted mantle wedge beneath Milos, similar to Santorini, and confirm previous models of an increasing influence of subducted sediment from the Central to the Western Aegean arc. Lavas from the western and eastern parts of Milos island exhibit distinct trace element and Pb isotope ratios irrespective of the temporal evolution of the magmatic activity that can be explained by a heterogeneous sediment mixture and more pronounced crustal assimilation in the lavas of East Milos. Amphibole thermobarometry of andesitic to rhyolitic lavas and basaltic enclaves indicates that mantle-derived melts stagnate and fractionate at pressures of ~ 450 MPa in the lower crust, whereas more evolved melts stagnate at ~ 200 MPa in the upper crust prior to eruption. Pre-eruptive magma temperatures are estimated by plagioclase-liquid thermometry between 840 and 940 °C. Increasing felsic lava production with time in the long-lived (3 Ma) Milos volcanic field is in accordance with a mature magma plumbing system that is characterized by lower and upper crustal magma storage. The geochemical diversity of volcanic rocks of Milos reflects the complex interplay of multiple magmatic processes within the broader Aegean arc.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 7","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148202940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Formation and preservation of Paleoproterozoic boron-rich evaporites","authors":"Dan Wang,&nbsp;Rolf L. Romer,&nbsp;Fulai Liu,&nbsp;Zhonghua Tian,&nbsp;Zongsheng Jiang,&nbsp;Zhiyong Zhu,&nbsp;Yuwei She,&nbsp;Yahan Wang,&nbsp;Na Wang,&nbsp;Guocheng Lv","doi":"10.1007/s00410-026-02329-6","DOIUrl":"10.1007/s00410-026-02329-6","url":null,"abstract":"<div><p>Ancient evaporitic borate deposits are rare in the geological record, and the mechanisms governing their formation and long-term preservation remain poorly constrained. The Paleoproterozoic Liao–Ji orogenic belt of the North China Craton hosts several metamorphosed stratiform borate deposits that provide a unique opportunity to address these issues. Heavy δ¹¹B (+ 7.5 to + 9.8‰) of borate minerals (suanite, ludwigite and szaibelyite) and δ³⁴S_V−CDT (+ 8.7 to + 16.1‰) of pyrrhotite demonstrate marine contributions, whereas whole-rock geochemistry, mineral chemistry, and negative ε_Nd values (mostly between − 2 and − 7) reflect substantial crustal input. MORB-like iron isotopes (-0.049 to + 0.292‰) indicate a dominantly hydrothermal source of iron. These features point to boron concentration within an evaporitic basin at the continent margin that received mixed marine and terrigenous contributions. Phase modelling and Zr-in-titanite temperatures constrain peak <i>P–T</i> conditions of regional granulite-facies metamorphism of the Wengquangou deposit to 750–800 °C at 0.6–1.0 GPa. In situ LA<i>–</i>ICP<i>–</i>MS U<i>–</i>Pb dating of zircon defines two age populations at ca. 2.15 Ga and 1.87–1.84 Ga, corresponding to the ages of deposition and granulite-facies metamorphism, respectively. Apatite U<i>–</i>Pb ages of ca. 1.71–1.64 Ga record a later post-peak thermal or fluid-related overprint. Prograde dehydration reactions converted soluble hydrous borates into stable anhydrous assemblages, fundamentally modifying mineralogy while largely retaining primary isotopic characteristics. This high-grade metamorphic overprint played a key role in stabilizing the deposit against post-depositional dissolution. Our data show that ancient evaporitic borate deposits formed by similar processes as modern ones, involving the leaching and mobilization of B from volcanic and sedimentary rocks, transport of B into a continent-margin basin, and concentration of B by evaporation. The rare preservation of ancient borate deposits does not indicate that they rarely formed, but that they are generally not preserved as regions hosting major evaporitic borate deposits seldom undergo subsequent high-grade metamorphism.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 7","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148202936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Controls on Fe3+/FeT ratios in volcanic amphiboles across silicic magmatic systems: effects of magmatic redox, crystallization temperature, and dehydrogenation","authors":"Barbara C. Ratschbacher,&nbsp;Claire E. Bucholz,&nbsp;Jennifer M. Jackson,&nbsp;Thomas S. Toellner,&nbsp;Wolfgang Sturhahn,&nbsp;Felix Marxer","doi":"10.1007/s00410-026-02321-0","DOIUrl":"10.1007/s00410-026-02321-0","url":null,"abstract":"<div><p>Amphiboles record crystallization temperatures, pressures, and melt compositions through their major- and minor-element chemistry. Their Fe³⁺/Fe^T (Fe³⁺/(Fe³⁺ + Fe²⁺)) ratios have also been proposed to record melt Fe³⁺/Fe^T ratios, and, by extension, magmatic oxygen fugacity (<span>({f}_{{O}_{2}})</span>). To test this, we analyzed Fe³⁺/Fe^T ratios in volcanic amphiboles from five silicic volcanic systems using single-crystal synchrotron-Mössbauer spectroscopy and combined these data with major-element chemistry, H₂O concentrations, and H isotope compositions measured from the same area of individual grains. The studied amphiboles crystallized under independently constrained magmatic <span>({f}_{{O}_{2}})</span> conditions spanning ΔNNO = −0.6 to + 2.2 (log units below and above the Ni-NiO buffer). The data show that Fe³⁺/Fe^T ratios are influenced by both primary magmatic processes and post-crystallization modifications. Three of the five volcanic systems show evidence for complex amphibole growth histories manifested in low- and high-Al amphibole compositions. Across the studied samples, Fe³⁺ is primarily accommodated through a ferri-Tschermak-type substitution (Si^4+(IV) + Fe^2+(VI) = Al^3+(IV) + Fe^3+(VI)) and amphibole Fe³⁺/Fe^T ratios generally increase with increasing <span>({f}_{{O}_{2}})</span> ranging from 0.14 ± 0.03 to 0.68 ± 0.01. However, two processes shift Fe³⁺/Fe^T ratios relative to values expected from independently constrained <span>({f}_{{O}_{2}})</span>: post-crystallization dehydrogenation and temperature-dependent Fe²⁺-Fe³⁺ exchange. Although these processes modify Fe³⁺/Fe^T ratios, they do not change amphibole Fe# (Fe^Total/(Fe^Total + Mg)), which varies more consistently with independently constrained <span>({f}_{{O}_{2}}.)</span> Amphibole Fe³⁺/Fe^T ratios therefore provide the most reliable record of magmatic <span>({f}_{{O}_{2}})</span> in systems that show no evidence for dehydrogenation and don’t have complex thermal and/or mixing histories. In more complex volcanic systems, amphibole Fe# provides a useful complementary metric for evaluating redox systematics.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 6","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148172828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Author Correction: Shallow storage of the explosive Earthquake Flat Pyroclastics magma body, Okataina Volcanic Center, Taupo Volcanic Zone, New Zealand: evidence from phase-equilibria experiments","authors":"Thomas W. Sisson,&nbsp;Robert P. Rapp,&nbsp;Elizabeth R. G. Grant,&nbsp;Dawnika L. Blatter,&nbsp;Kari M. Cooper","doi":"10.1007/s00410-026-02328-7","DOIUrl":"10.1007/s00410-026-02328-7","url":null,"abstract":"","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 6","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02328-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148172379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}