Contributions to Mineralogy and Petrology最新文献

{"title":"Experimental constraints on the mechanism of ilmenite dissolution and exsolution in granitic melts","authors":"Jia-Xian Li,&nbsp;Aleksandr S. Stepanov,&nbsp;Anna M. Nikolenko,&nbsp;Dmitry A. Chebotarev,&nbsp;Jian Wang,&nbsp;Aleksandr I. Khmelnikov,&nbsp;Nikolai S. Karmanov,&nbsp;Irina A. Zhukova,&nbsp;Jin-Yu Zheng","doi":"10.1007/s00410-026-02362-5","DOIUrl":"10.1007/s00410-026-02362-5","url":null,"abstract":"<div><p>Ilmenite is a ubiquitous accessory mineral in igneous and metamorphic rocks, controlling behavior of trace elements during generation of anatectic granitic melts and fractionation of magmas. However experimental data on reactions involved in ilmenite dissolution in felsic melts are limited. We performed twenty two experiments in felsic melts of a wide compositional range (Al/(Na + K) from 0.7 to 1.3) at pressure 0.1 and 1 GPa, and at temperature from 800 to 1000 °C. In the piston-cylinder experiments, boron nitride (BN) and MgO assemblies were employed to exert different redox conditions. The oxygen fugacities estimated from ilmenite composition indicate substantial overlap between the 0.1 GPa cold-seal pressure vessels (CSPV) and 1 GPa MgO piston-cylinder experiments, whereas in BN piston-cylinder experiments conditions were more reducing. Elevated temperatures and oxygen fugacity promoted ilmenite dissolution, while melt water content and pressure exhibited relatively minor effects. Ilmenite solubility is lowest when the A/NK ratio close to 1.1 and increases toward both more alkaline and more peraluminous melt compositions. Furthermore, our experiments demonstrate that ilmenite dissolution in Ca-free systems can produce rutile at pressures as low as 0.1 GPa and melts coexisting with ilmenite commonly are close to rutile saturation. The experiments produced homogeneous ilmenite, sponge-textured ilmenite, and rutile-ilmenite intergrowths with oriented rutile lamellae. Homogeneous and exsolved ilmenite can occur under similar oxygen fugacities, and the development of the exsolution textures was determined by the combination of the elevated oxygen fugacity and melt composition. The more common development of rutile–ilmenite intergrowths at 1 GPa suggests an additional pressure control on textural re-equilibration. The experimental textures show similarities to natural textures, but the evolution of those in more stable conditions results in coarser-grained assemblages.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 10","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148927829","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":"Supersaturation dynamics govern crystallographic orientation inheritance during nucleation: insights from aqueous salt systems","authors":"Brendan V. Dyck,&nbsp;Xavier Chang,&nbsp;Ben Britton","doi":"10.1007/s00410-026-02363-4","DOIUrl":"10.1007/s00410-026-02363-4","url":null,"abstract":"<div><p>Crystal nucleation kinetics exert a primary control on rock microstructure, phase distribution, and how close to equilibrium mineral reactions proceed. In multiphase systems, epitaxy—where a child phase inherits crystallographic orientation from a parent substrate—is generally the lowest-energy nucleation pathway. Documented examples include kyanite–staurolite, biotite–tourmaline, and amphibole–pyroxene pairs, all of which are identifiable by distinct crystallographic orientation relationships (CORs) in electron backscatter diffraction (EBSD) data. However, even where epitaxial CORs are common, not all grains nucleate epitaxially because local variations in mass-transport efficiency can drive nucleation along higher-energy pathways. Lattice registry, the atomic-scale alignment across a phase boundary, is necessary for epitaxy, but it alone is not always sufficient to cause orientation inheritance. For example, in evaporite-forming environments, halite often nucleates homogeneously at evaporative boundary layers despite compatible carbonate substrates. What, then, determines whether nucleation proceeds epitaxially, heterogeneously, or homogeneously in mineralizing systems? Using the halite (NaCl), niter (KNO₃), and sylvite (KCl) aqueous salt systems we test whether the slope of a salt’s aqueous temperature–solubility curve predicts its default nucleation pathway. Shallow temperature–solubility slopes (i.e. NaCl) require evaporation or reactive mixing fronts to reach saturation, promoting diffusion-limited, boundary layer nucleation. In contrast, steep slopes (i.e. KNO₃) can be crossed by system-wide cooling alone, reducing the influence of diffusion. We crystallized niter in the presence of calcium carbonates and quartz, and halite and sylvite in the presence of fluorite and used EBSD to quantify parent–child CORs between the substrates and nucleated salt minerals. We find halite nucleates homogeneously under all tested conditions, including in solution volumes &lt; 10 μm³. In contrast, niter readily nucleates epitaxial to carbonate substrates. As an intermediate to the temperature–solubility slopes of the NaCl and KNO₃ systems, KCl grown in the presence of a fluorite substrate records a mix of epitaxial, non-epitaxial heterogeneous, and homogeneous nucleation behaviour. These results demonstrate that higher-energy nucleation pathways are favoured in systems with mass-transport-limited kinetics. The absence of epitaxial CORs in certain metamorphic and igneous reactions may therefore be a useful indicator of diffusion-limited reaction kinetics rather than due to a lack of crystallographically compatible, low-energy nucleation sites.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 10","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148927316","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":"Experimental constraints on pre-eruptive conditions at Nabro volcano, Eritrea, 2011, and implications for sulphur emissions","authors":"Amy Donovan,&nbsp;Joan Andújar,&nbsp;Bruno Scaillet,&nbsp;Iris Buisman,&nbsp;Clive Oppenheimer","doi":"10.1007/s00410-026-02357-2","DOIUrl":"10.1007/s00410-026-02357-2","url":null,"abstract":"<div><p>We present new experimental constraints on the pre-eruptive magma storage conditions at Nabro Volcano, Eritrea, prior to its 2011 eruption, and discuss the implications for sulphur emissions. We find that the magma was likely stored in the shallow crust prior to eruption, following an intrusion in March 2011. This reservoir was located at ~ 7 km depth, and was recharged immediately prior to the eruption, from a deeper reservoir located at 20 km. The temperature of the magma was 1030 °C with 3 wt% dissolved H₂O, at redox conditions around the Quartz-Fayalite-Magnetite buffer (QFM). Our experimental results show that most melt inclusions from previous studies record earlier stages of magmatic evolution. Based on the determined pre-eruptive conditions, we calculate the composition and amount of pre-eruptive excess fluid and find that 3–8 wt% of an excess fluid with 1–3 wt% S is needed to explain the amount of SO₂ measured by satellite remote sensing. The abundance of this excess fluid may have contributed to the explosive character of the eruption, whose plume reached the lower stratosphere, assisted by convective transport linked to the Asian monsoon.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 10","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02357-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148877997","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":"The effect of heterogeneous nucleation site availability on rock microstructure: a new perspective from EBSD investigation","authors":"Stefano Peres,&nbsp;Thomas A. Griffiths,&nbsp;Matteo Masotta,&nbsp;Fabio Colle,&nbsp;Alessio Pontesilli,&nbsp;Stefano Iannini Lelarge,&nbsp;Lucia Mancini,&nbsp;Rainer Abart","doi":"10.1007/s00410-026-02360-7","DOIUrl":"10.1007/s00410-026-02360-7","url":null,"abstract":"<div><p>In this study, we investigate the effect of the availability of sites for heterogeneous nucleation on the microstructure of moderately to highly undercooled synthetic trachybasalts under anhydrous and hydrous (2 wt% H₂O) conditions. Experiments were performed at 400 MPa by cooling melts from 1300 °C to target temperatures of 1150 °C, 1100 °C, and 1050 °C, followed by isothermal holds of 5 or 30 min. In one experimental series, 0.5 wt% Cr₂O₃ was added to increase the liquidus temperature of spinel and promote heterogeneous nucleation of clinopyroxene on spinel. All Cr-doped anhydrous samples comprise a high number of small skeletal crystals of clinopyroxene and spinel. Electron backscatter diffraction maps (EBSD) reveal the presence of crystallographic orientation relationships (CORs) at the interfaces shared between clinopyroxene and spinel grains situated in their centers, indicating heterogeneous nucleation of clinopyroxene on spinel. On the contrary, the Cr-free anhydrous samples are characterized by fewer large dendritic clinopyroxene crystals, which grew without significant competition from their neighbors because of the low amount of pre-existing spinel grains acting as heterogeneous nucleation sites. Our findings confirm that the availability of heterogeneous nucleation sites and the timing and sequence of nucleation can play a dominant role in shaping microstructures, more than compositional variations and nominal undercooling. Early formed mineral phases may act as seeds for heterogeneous nucleation and can potentially induce fast crystallization of magmatic systems that experience thermal or constitutional undercooling and increase magma viscosity, influencing its stagnation or fragmentation, depending on the crystallinity of the system. </p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 10","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02360-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148877995","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":"Tracing magma generation and evolution in a multi-level magma plumbing system at the Izu rear-arc","authors":"John O. Edgar,&nbsp;Abigail K. Barker,&nbsp;Cedric Hamelin,&nbsp;Chris Harris,&nbsp;Martin Jutzeler","doi":"10.1007/s00410-026-02350-9","DOIUrl":"10.1007/s00410-026-02350-9","url":null,"abstract":"<div><p>Volcanism in the Izu rear-arc is bimodal in composition and occurs in an extensional zone associated with thickened arc crust. IODP Expedition 350 sampled a 4.0 to 4.4 Ma pumiceous felsic succession at 700 m below seafloor from Site U1437 in the Izu rear-arc. Named Unit II, this 45 m thick succession exhibits multiple homogeneous pumice-rich beds that are complexly graded and interbedded. Minor tuffaceous mudstone represents hiatus in eruptions when background sedimentation resumed. Using plagioclase crystal chemistry, we investigate the generation and evolution of the magmas and reconstruct the architecture of their corresponding magma plumbing system. Plagioclase is compositionally bimodal with peak frequencies at An 30–60 and An 75–95. Plagioclase crystals have ⁸⁷Sr/⁸⁶Sr of 0.703096 to 0.703380, and ẟ¹⁸O values of 5.2 to 6.4‰. We interpret the chemical zonation within individual crystals to represent fractional crystallisation, recharge, magma mixing and partial melting of altered crust. From the plagioclase-liquid crystallisation pressures, we identified deep mafic magma pockets in the oceanic lithosphere (30 to 38 km) and below the mantle-crust transition (20 to 24 km). During ascent, the magmas differentiated and stalled in the lower (10 to 12 km) and upper crust (4 to 6 km). We infer the source of the Unit II magmas to be depleted mantle wedge, associated with rifting of the Philippine Sea Plate, enriched by a uniform contribution of mélange and variable fluid flux from the subducted slab.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 10","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02350-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148877996","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":"Carbonation of diverse ultramafic rocks: implications for Ca-rich protolith from the Setogawa Group, Central Japan","authors":"Tatsuya Hattori,&nbsp;Ryosuke Oyanagi,&nbsp;Tomoyuki Mizukami,&nbsp;Yumiko Harigane,&nbsp;Mayuko Fukuyama,&nbsp;Asuka Yamaguchi,&nbsp;Tomoaki Morishita","doi":"10.1007/s00410-026-02359-0","DOIUrl":"10.1007/s00410-026-02359-0","url":null,"abstract":"<div><p>Ophicarbonate/listvenite and ultramafic rocks are distributed in various tectonic blocks in the western Izu Peninsula. These ultramafic rocks are likely of upper mantle origin, influenced by magmatic activity associated with the formation of the Izu-Bonin-Mariana intra-arc and back-arc basins within the Philippine Sea Plate. Carbonation of ultramafic rocks plays a fundamental role in fluid-rock interaction processes in subduction zone environments, yet the controls on carbonation pathways remain incompletely understood. In particular, the influence of protolith composition on reaction progress and mineral assemblage development has not been fully constrained. This study focuses on representative ophicarbonate/listvenite from the Setogawa Group, a Paleogene accretionary complex. The Setogawa Group contains diverse ultramafic rocks such as dunite, harzburgite, lherzolite and clinopyroxenite and is highly suitable for discussing carbonation of ultramafic rocks due to differences in original rock. Based on petrographic observations and whole-rock chemical compositions, the rocks are classified as Serpentine-Talc-Magnesite rock, Dolomite-Talc-Quartz rock, and listvenite. Thermodynamic modeling further reveals that clinopyroxene-rich ultramafic rocks undergo distinct reaction pathways compared to olivine-rich compositions, with earlier talc formation and different fluid-rock ratios required for listvenitization. These findings demonstrate that the bulk composition of the protolith, particularly Ca content, controls carbonation pathways, mineral assemblages, and the evolution of physical properties during fluid-rock interaction. Our results provide a unified framework for understanding variability in listvenite formation and highlight the importance of protolith heterogeneity in controlling carbonation processes in subduction zone environments.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02359-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148837937","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":"Trace element mobility and mineral-scale redistribution during retrograde metamorphism of lawsonite-bearing high-pressure rocks from Elekdağ, Turkey","authors":"Yu-Lu Tian,&nbsp;Jia-Min Wang,&nbsp;Gültekin Topuz,&nbsp;Aral I. Okay,&nbsp;Tong Liu","doi":"10.1007/s00410-026-02358-1","DOIUrl":"10.1007/s00410-026-02358-1","url":null,"abstract":"<div><p>Subduction-zone metamorphism significantly influences trace element redistribution during burial and exhumation of oceanic lithosphere. We investigate high-pressure metamorphic rocks from the Elekdağ ophiolite (Turkey) using petrography, mineral chemistry, phase-equilibrium modelling, and rutile U–Pb geochronology. Phase-equilibrium modelling indicates peak conditions of 2.3–2.6 GPa and 530–600 °C, with rutile U–Pb dating constraining near-peak metamorphism at 102 ± 14 Ma, followed by blueschist-facies retrogression. Whole-rock geochemistry reveals that while some samples retain MORB-like compositions, others exhibit high field strength element (HFSE) depletion and large-ion lithophile element (LILE; e.g., K, Rb, Ba, B) enrichment. Phengite-hosted LILE enrichment points to open-system fluid infiltration, likely reflecting a combination of protolith seafloor alteration and retrograde metasomatism. Semi-quantitative mass-balance calculations and mineral-scale data indicate that trace element features reflect scale-dependent processes. Locally, light rare earth elements (LREEs), Sr, and HFSEs were predominantly redistributed during the breakdown of lawsonite to clinozoisite/epidote via interface-coupled dissolution–reprecipitation. Although LREEs and Sr are traditionally fluid-mobile, their high sequestration into these newly formed phases suggests restricted, localized mobility, though minor matrix-scale external fluid exchange cannot be entirely ruled out. These findings highlight a scale-dependent decoupling of element mobility and demonstrate that whole-rock geochemical signatures in retrogressed high-pressure rocks integrate protolith inheritance, open-system fluid overprinting, and mineral-scale redistribution. Relying solely on bulk geochemistry may thus lead to the misinterpretation of subduction-zone fluid-rock dynamics without integrating detailed mineral-scale budgets.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148837362","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":"Origin and implications of the low-Fe igneous series at Buldir Island, western Aleutian arc","authors":"Gene M. Yogodzinski,&nbsp;Shawn Arndt,&nbsp;Ryan Waldman,&nbsp;Michael Bizimis,&nbsp;Jeffrey Vervoort,&nbsp;Kenneth W. W. Sims","doi":"10.1007/s00410-026-02352-7","DOIUrl":"10.1007/s00410-026-02352-7","url":null,"abstract":"<div><p>Volcanic whole-rock compositions from Buldir Island define a highly calc-alkaline (low-Fe) igneous series, with molar Mg/Mg + Fe* (total iron Mg#) mostly &gt; 0.60; SiO₂ from 50–64 wt.%; and distinctly low FeO*, CaO, CaO/Al₂O₃, and FeO*/Al₂O₃ relative to MgO. Many Buldir samples have trace element characteristics similar to western Aleutian seafloor lavas along upward curving trends of increasing Sr and Sr/Y with increasing SiO₂ and decreasing MgO. Least radiogenic Sr in andesites only (57–62 wt.% SiO₂ with ⁸⁷Sr/⁸⁶Sr ~ 0.7029) requires a key role for source mixing in the origin of the low-Fe series at Buldir. Andesites and dacites falling outside these source mixing trends show evidence of fractional crystallization interpreted to be a late-stage (over-printing) effect. Partitioning data indicate that heavy REEs will behave compatibly in amphibole-saturated melts evolving at temperatures &lt; 1000 °C. However, recent hydrous and high fO₂ experiments show that Buldir melts with more than 4–5 wt.% MgO were unlikely to have reached amphibole saturation and cannot explain the decline in Yb concentrations starting at &gt;9 wt.% MgO. Distinctive reverse sigmoidal (backward-S) REE pattern shapes in Buldir samples are also unlikely to be products of amphibole removal from evolving liquids and are instead interpreted to reflect melting of a light REE-depleted MORB source under eclogite conditions followed by interaction of the resulting hydrous-felsic slab melt with mantle peridotite upon ascent. Published pMELTS simulations and experimental observations indicate this style of melt-rock reaction will also create low FeO* and CaO in primitive (high-Mg#) melts over a wide range of SiO₂ and MgO, as observed in Buldir and western Aleutian seafloor datasets. The implication is that distinctive aspects of low-Fe calc-alkalinity in most Buldir samples with SiO₂ from 50 to 62% are created at sub-MOHO depths where cool-hydrous-siliceous partial melts of subducted-eclogitized MORB rise, decompress, and undergo thermal-chemical exchange with depleted peridotite that is hotter by hundreds of °C.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02352-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148783203","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":"Mica deformation signatures: geochemical and strain investigation of phlogopite and biotite from the Drybones Bay and Mud Lake kimberlites (Northwest Territories, Canada)","authors":"Song Gao,&nbsp;Roberta L. Flemming,&nbsp;Anton R. Chakhmouradian,&nbsp;Barrett Elliott","doi":"10.1007/s00410-026-02356-3","DOIUrl":"10.1007/s00410-026-02356-3","url":null,"abstract":"<div><p>Phlogopite in kimberlites commonly displays evidence of complex deformation history. Textural evidence includes kink-banding, undulatory extinction and bent cleavage; this is conventionally ascribed to strain in the lithospheric mantle. However, the extent and intensity of deformation in phlogopite from kimberlites have not been systematically explored. In this work, the degree of strain-related mosaicity, resulting from plastic deformation in micas from the Drybones Bay and Mud Lake kimberlites (Canada), was quantified by measuring ‘streaking’ along chi (χ) direction in 2D X-ray diffraction images, as the sum of full-width-at half-maximum Σ(FWHMχ) where Σ(FWHMχ) &gt; 2.5^o indicates deformed phlogopite grains. The examined phlogopite was categorized into the low-Ti-Cr and low-Cr, Ti-rich varieties. The low Σ(FWHMχ) signature of the low-Cr, Ti-rich phlogopite grains matches their low-strain environment during or immediately after kimberlite emplacement. On the other hand, appreciable variations in Σ(FWHMχ) with respect to both deformed and undeformed low-Ti-Cr phlogopite cannot be feasibly explained by transport in a turbulent kimberlite magma during rapid ascent from the mantle. It seems most likely that the low-strained low-Ti-Cr phlogopite grains are genetically unrelated to their high-strained counterparts, which are interpreted as xenocrysts derived from metasomatized mantle xenoliths. We conclude that optically observable deformation microtextures in phlogopite are not a reliable indicator of their xenocrystic origin for the following reasons: (1) the low-Ti-Cr phlogopite population comprises both deformed and undeformed crystals; (2) some deformed low-Ti-Cr phlogopite grains are cognate phenocrysts; and (3) strain features in phlogopite xenocrysts can also be developed under crustal conditions in response to post-emplacement tectonics.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148782858","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":"Experimental calibration of V–Sc oxybarometers based on clinopyroxene- and orthopyroxene-melt equilibria","authors":"Enzo-Enrico Cacciatore,&nbsp;Zoltán Zajacz","doi":"10.1007/s00410-026-02347-4","DOIUrl":"10.1007/s00410-026-02347-4","url":null,"abstract":"<div><p>We present new experimental calibration of V–Sc exchange between clinopyroxene, orthopyroxene, and silicate melt at physical–chemical conditions characteristic of arc magmatism. The calibration combines previously published experimental datasets with new high-pressure rapid-quench experiments conducted in a molybdenum-hafnium carbide pressure vessel assembly equipped with a custom-designed semi-permeable hydrogen membrane to control oxygen fugacity (<i>f</i>O₂). Experiments were performed at 200 MPa under water-saturated conditions, covering temperatures of 1030–870 °C and <i>f</i>O₂ from − 1 to + 7 log units relative to fayalite-magnetite-quartz buffer (FMQ). Melt composition effects were evaluated by comparing liquid lines of descent of medium-K calc-alkaline basaltic and shoshonitic magmas. The resulting orthopyroxene-melt oxybarometer accurately reproduces <i>f</i>O₂, yielding a median absolute error of 0.36 log units over the range FMQ − 2 to + 5.5. Precise calibration of the clinopyroxene-melt oxybarometer was more challenging due to the clinopyroxene’s more complex composition and potential kinetic effects. Nevertheless, the proposed equation reproduces <i>f</i>O₂ with an overall median absolute error of 1.01 log units over the calibrated range FMQ − 2.5 to + 5. Provided that the equilibrium melt composition can be constrained by the analysis of silicate melt inclusions or groundmass glass, the proposed pyroxene-melt oxybarometers can be used to track the variation of magmatic <i>f</i>O₂ in diverse settings and over a broad temperature range.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02347-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148782857","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}