Contributions to Mineralogy and Petrology最新文献

{"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}

{"title":"Author Correction: Apatite geochronology of the Sept-Iles Intrusive Suite (Grenville province, Canada) reveals two magmatic episodes 55 Myrs apart related to plume arrival and subsequent rifting","authors":"Hélène Legros,&nbsp;Marie A. Kieffer,&nbsp;Sarah A. S. Dare,&nbsp;Olivier Namur,&nbsp;Michael D. Higgins,&nbsp;Dany Savard,&nbsp;Stijn Glorie","doi":"10.1007/s00410-026-02336-7","DOIUrl":"10.1007/s00410-026-02336-7","url":null,"abstract":"","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 6","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148172496","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":"Chlorine (Cl) and hydrogen chloride (HCl) solubility in hydrous silicate melts: implications for volcanic gas composition","authors":"Monika K. Rusiecka,&nbsp;Bernard J. Wood","doi":"10.1007/s00410-026-02332-x","DOIUrl":"10.1007/s00410-026-02332-x","url":null,"abstract":"<div><p>Chlorine is a key volatile in magmatic and volcanic systems, being a major consumer of atmospheric ozone and an important ligand for metal transport. Despite chlorine’s importance however, the combined effects of melt composition and H₂O on Cl solubility and HCl degassing remain poorly constrained, particularly at magmatic pressures. We present high-pressure (0.5–1.63 GPa), 1200 °C experiments on hydrous andesite, dacite and rhyolite (up to ~ 8–9 wt% H₂O) equilibrated with Ag–AgI–AgCl buffers to fix fCl₂, and with graphite-saturated C–O–H fluids to buffer fO₂ near CCO. Chlorine concentrations in the glasses define chloride capacities (C_Cl) that we combine with anhydrous data from earlier work. Using LASSO regression, we obtain a revised chloride-capacity model that improves predictions for evolved, silica- and alkali-rich melts. The explicit HO_0.5 term remains statistically insignificant up to ~ 8–9 wt% H₂O, confirming that H₂O acts primarily as an ideal diluent of network-forming and network-modifying cations rather than exerting a strong, specific control on Cl dissolution. We couple the new C_Cl model with H₂–H₂O–HCl equilibria and a C–H–O–S–Cl fluid speciation code to derive a simple expression for HCl fugacity in terms of melt composition, temperature, pressure and fH₂O, without requiring explicit values of fCl₂ or fO₂. Applied to literature experiments and melt inclusions, the model predicts (i) low fCl₂ (~ 10^− 10–10^− 6 bar) and much higher fHCl (~ 10⁻¹–10² bar) at near-surface pressures, consistent with HCl-dominated volcanic emissions; (ii) SO₂/HCl ratios for the 2002–2003 Mt. Etna eruption that match plume measurements; and (iii) strong variations in SO₂/HCl and S/Cl during decompression due to contrasting pressure dependences of sulphur and chlorine capacities. Our framework links petrological archives (melt inclusions, matrix glasses) to HCl contents of magmatic gases, providing a tool to interpret excess degassing, magma plumbing and volcanic halogen fluxes to the atmosphere. We also used HSC Chemistry software to calculate the production of reactive chlorine species (ClO) from HCl in volcanic gases upon mixing with air at the vent.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 6","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02332-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148009417","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":"Reproduction of ultra-fine oscillatory zoning by direct numerical simulations of step dynamics considering impurity-induced crystal growth inhibition","authors":"Hiroki Torii,&nbsp;Hitoshi Miura","doi":"10.1007/s00410-026-02323-y","DOIUrl":"10.1007/s00410-026-02323-y","url":null,"abstract":"<div><p>Oscillatory compositional zoning (OCZ), widely observed in minerals, suggests the presence of self-organizing mechanisms inherent in the mineral formation process. In recent years, a mechanism for OCZ formation has been proposed, focusing on impurity-induced inhibition of crystal surface growth. We performed a numerical simulation that couples step dynamics and random impurity adsorption–desorption on the crystal surface with diffusive solute transport around the crystal. The results demonstrate that, even under static external conditions, the crystal growth rate exhibits spontaneous periodic variation, leading to oscillatory impurity incorporation. The resulting compositional zoning shows a periodicity on the order of several tens of nanometers, consistent with nanoscale periodic structures observed in natural minerals such as dolomite, garnet, and zircon. This study presents a novel theoretical framework that attributes the origin of the nanoscale ultra-fine OCZ to the nonlinear response of crystal growth, providing significant insights into self-organization phenomena in mineralogy and crystal growth science.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 6","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148009290","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 of amphibole in evolving Variscan subcontinental lithospheric mantle: the Marais de Limagne xenoliths, Massif Central, France","authors":"Jacek Puziewicz,&nbsp;Sonja Aulbach,&nbsp;Károly Hidas,&nbsp;Stanisław Mazur,&nbsp;Theodoros Ntaflos,&nbsp;Axel Gerdes,&nbsp;Magdalena Matusiak-Małek,&nbsp;Małgorzata Ziobro-Mikrut","doi":"10.1007/s00410-026-02326-9","DOIUrl":"10.1007/s00410-026-02326-9","url":null,"abstract":"<div><p>Amphibole in peridotite xenoliths in Cenozoic volcanic rocks of the Massif Central, France, is generally sparse but widely distributed. Here, we discuss its origin in the xenolith suite of Marais de Limagne (Devès volcanic field) and its bearing on evolution of lithospheric mantle in the southern part of the Massif Central. The xenoliths are lherzolites containing (1) no amphibole, (2) 2–5 vol. % of dispersed amphibole or (3) 12–22 vol. % of amphibole forming aggregates. The amphibole-free lherzolites are similar to LREE-depleted lherzolites typical for lithospheric mantle underlying southern part of the Massif Central. Increasing amphibole volume is correlated with a decrease of Al contents in both pyroxenes (opx: 0.19 → 0.14, cpx 0.30 → 0.21 Al atoms per formula unit, a pfu), with an increase of spinel Cr/(Al + Cr) from 0.09 to 0.17, and with a transition from LREE-depleted to LREE enriched clinopyroxene REE patterns. By comparison, the lherzolites with amphibole aggregates contain pyroxenes that are more Al-depleted (opx ~ 0.10, cpx ~ 0.13 Al a pfu) and Cr-enriched spinel (Cr/(Cr + Al) 0.21–0.39). The amphibole is pargasitic and locally was affected by incipient melting producing secondary clinopyroxene, olivine and glass. <i>In-situ</i> determination of ⁸⁷Sr/⁸⁶Sr ratios in clinopyroxene and amphibole, which are largely in isotopic equilibrium, yields values from 0.70319 to 0.70371, i.e. moderately higher than the Depleted Mantle. We suggest that heterogeneous percolation of a highly mobile metasomatic agent that contained water, Ba, Sr, K, Na and was LREE-enriched, resulted in variable addition of amphibole to anhydrous lherzolitic protoliths. Amphibole crystallized at the expense of spinel and clinopyroxene, which were the source of Al. Spinel was passively enriched in Cr as amphibole volume increased. Amphibole occurring in low volumes inherited the chemical characteristics of protolith minerals, whereby ⁸⁷Sr/⁸⁶Sr ratios up to 0.7037 may reflect an earlier, Variscan subduction imprint. In contrast, the composition of amphibole occurring in large volumes reflects the composition of the metasomatic medium. The low and rather homogeneous amphibole ⁸⁷Sr/⁸⁶Sr (0.7033–0.7034) in amphibole-rich samples, combined with published elevated hydrogen isotope ratios for amphibole in other xenoliths from the southern Massif Central, suggest relatively recent derivation of the metasomatic agent from an asthenospheric mantle source that was polluted by young subducted oceanic crust, with limited influence of sedimentary components.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 6","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02326-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147938472","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":"How dry is the Archean mantle lithosphere beneath the Kaapvaal craton, southern Africa?","authors":"Jessy Dominique,&nbsp;Bertrand N. Moine,&nbsp;Ioana B. Radu,&nbsp;Jean-Luc Devidal,&nbsp;Ana E. Pradas del Real,&nbsp;Gelu Costin,&nbsp;Dmitri A. Ionov,&nbsp;Nathalie Bolfan-Casanova","doi":"10.1007/s00410-026-02322-z","DOIUrl":"10.1007/s00410-026-02322-z","url":null,"abstract":"<div><p>Kimberlites allow exceptional insights deep into cratons by rapidly bringing to the surface well-preserved mantle fragments from a broad depth range. Water, mainly dissolved as hydroxyl, OH, is a key parameter for craton long-term stability as it affects viscosity and melting properties. We report here a multi-disciplinary (FTIR, Mössbauer, XANES, EPMA, LA-ICPMS) study of 17 harzburgite and dunite xenoliths from the Jagersfontein mine (Kaapvaal, South Africa) that are typical residues of high-degree melting (Mg# 92–94) and display minimum metasomatic interaction with the kimberlite as evidenced using trace elements. Thermobarometry yields 742–887 °C and 30-37.5 kbar for the equilibrium conditions of garnet free peridotites and 674–1084 °C and 27–51 kbar for garnet bearing peridotites. Oxygen fugacity, expressed as Δlog<i>f</i>O₂ relative to the FMQ buffer, varies between − 1.32 and − 0.29 ± 0.5 in the Cr-spinel bearing peridotites and between − 2.87 and − 0.57 ± 0.5 in garnet peridotites. OH content ([OH]) in the bulk rock varies between 29 and 99 ppm wt. H₂O. Considering the low evidences of metasomatic interactions within the peridotites and the OH equilibrium between minerals, we suggest that the hydrogen content within the xenoliths remained pristine for billions of years. The [OH] decrease with depth can be explained by melting or, because bulk [OH] and Δlog<i>f</i>O₂ decrease with increasing depth, by a change in speciation from oxidized H₂O to reduced H₂ in line with thermodynamic modelling of fluid-saturated and undersaturated peridotite. Still, despite our efforts we did not observe H₂ in the samples.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 6","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147937975","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":"Fluid evolution during the development of scapolite-bearing assemblages in striped calcsilicate layers between metapelites and metacarbonates","authors":"Jeongmin Lee,&nbsp;Hyeong Soo Kim","doi":"10.1007/s00410-026-02327-8","DOIUrl":"10.1007/s00410-026-02327-8","url":null,"abstract":"<div><p>Stratified calcsilicate layers intercalated with metapelites and metacarbonates in the northwestern Gyeonggi Massif, Korea, preserve a two-stage metamorphic and metasomatic history that records the evolution of H₂O–CO₂–NaCl (± HCl) fluids in a lithologically heterogeneous crustal environment. Scapolite-bearing assemblages in garnet-bearing and garnet-free layers display distinct microtextural and mineral-chemical features that reflect contrasting fluid-buffering capacities during medium pressure regional metamorphism. During peak metamorphism, both lithologies acted as locally internally buffered systems, allowing scapolite-I (X_Cl &lt; 0.1) to form in response to micro-scale variations in X_CO2. Clinozoisite + plagioclase (oligoclase to andesine) inclusions within scapolite-I, ferro-pargasite inclusions in clinopyroxene, and pyrite enclosed in scapolite-I indicate alternating CO₂-consuming and CO₂-producing micro-domains under relatively low <i>f</i>O₂, generating centimeter- to meter-scale heterogeneity in X_CO2. During retrograde metamorphism, the system evolved into a locally infiltration-dominated regime. Garnet-free layers selectively incorporated externally derived saline fluids, forming scapolite-II (X_Cl = 0.1–0.3), albitic plagioclase, and Ca-amphibole, recorded by scapolite-II overgrowths on scapolite-I and albitic rims on plagioclase (oligoclase to andesine). In contrast, garnet-bearing layers experienced anorthitization and destabilization of scapolite-I and clinopyroxene, releasing Na-rich and metal–chloride-bearing fluids. These contrasting metasomatic responses established a lithologic-scale Cl-circulation loop linked to variations in X_CO2 and in the activities of Na⁺, Ca²⁺, and Cl^–, explaining the selective stabilization of scapolite-II in garnet-free layers and oscillatory zoning in plagioclase. Mineralogical and geochemical evidence suggests that the saline fluids may have derived from deeply sourced metamorphic brines and/or NaCl (± HCl)-bearing hydrothermal systems associated with post-collisional alkali magmatism. Scapolite–plagioclase mineral pairs thus provide robust constraints on fluid composition and metasomatic processes during regional metamorphism and subsequent exhumation.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 6","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147938223","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":"Hybrid granite factory in the continental lower crust: an accessory mineral perspective from the Ivrea-Verbano Zone, Northern Italy","authors":"Caliméria do Carmo,&nbsp;Oscar Laurent,&nbsp;Olivier Vanderhaeghe,&nbsp;Andrea Galli,&nbsp;Lorenzo Tavazzani,&nbsp;Emilie Bruand","doi":"10.1007/s00410-026-02325-w","DOIUrl":"10.1007/s00410-026-02325-w","url":null,"abstract":"<div><p>Granitoids and volcanic rocks of hybrid composition between mantle and crustal components are common in various tectonic settings and contribute to both the growth and differentiation of the continental crust. However, the mechanisms by which such hybrid magmas are produced are debated. We focus on a key lower crustal exposure of the Permian Sesia Magmatic System located in the Ivrea-Verbano Zone—IVZ, Italy, allowing to directly investigate the deep roots of a hybrid magmatic system. Integrating multi-scale field observations and bulk-rock data with zircon and apatite petrochronology (U–Pb dating, trace elements, Lu–Hf and Sm–Nd isotopes respectively), we show that lower-crustal orthopyroxene-bearing rocks associated to migmatites in a ‘frozen’ hybridization zone, correspond to hybrid cumulates from which melts were extracted to form upper crustal granitic plutons. Igneous zircon records at least three crystallization stages: (i) initial low-crystallinity hybridization phase at lower-crustal scale; (ii) subsequent chemical differentiation in a mush system, driven by reactive porous flow at the 10²–10³ m scale; and (iii) final crystallization after significant melt extraction and subsequent, smaller-scale (10⁰–10⁻¹ m) chemical equilibration. Apatite, on the other hand, is fully homogenized at the sample scale but chemical differences between samples preserve the first-order hybridization trends. While crustal-scale differentiation (melt extraction, transfer and cooling) took place in a short time span (ca. 2–4 Ma) as previously suggested in the IVZ, our zircon U–Pb data are permissive of the construction and equilibration of the lower crustal system over a longer period of ca. 15 Myr minimum. Our study also reveals the potential of accessory minerals, in particular zircon, to preserve the successive steps involved in the complex history of the lower crust, even at high temperatures.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 6","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147829182","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":"Phase equilibria and liquid lines of descent in alkali basalts at one atmosphere and the role of oxygen fugacity","authors":"Sophia Y. M. Thorn,&nbsp;Olivier Namur,&nbsp;David A. Neave,&nbsp;Bernard Charlier,&nbsp;Jasper Berndt,&nbsp;Stephan Klemme","doi":"10.1007/s00410-026-02309-w","DOIUrl":"10.1007/s00410-026-02309-w","url":null,"abstract":"&lt;div&gt;&lt;p&gt;This study presents new experimental data on the effect of oxygen fugacity (&lt;i&gt;f&lt;/i&gt;O&lt;sub&gt;2&lt;/sub&gt;) and bulk composition on phase equilibria and liquid lines of descent in alkali basalts. Crystallisation experiments were performed at one atmosphere, in the temperature range 1220–1050 °C and at fO&lt;sub&gt;2&lt;/sub&gt; conditions corresponding to fayalite–magnetite–quartz (FMQ) equilibrium and the following log-unit deviations from this equilibrium: FMQ-1, FMQ + 1.5 and FMQ + 3. Experiments were grouped into two series, those on primitive compositions (9.9–11.9 wt% MgO; total alkali 3.1–5.3 wt%), and those on evolved compositions (5.1–5.8 wt% MgO; total alkali 5.7–8.6 wt%). Experiments on primitive compositions produce assemblages of olivine, clinopyroxene and spinel, with plagioclase present in less silica-undersaturated compositions. Experiments on evolved compositions produce similar assemblages, though olivine is often absent at higher fO&lt;sub&gt;2&lt;/sub&gt;. Whitlockite is present at low temperature, plus occasional Fe-Ti oxides. Nepheline is only observed in the most silica-undersaturated composition at low temperature. Mineral compositions and stability are strongly controlled by bulk composition and redox conditions. High MgO bulk contents favour the early appearance of olivine, while the appearance of clinopyroxene is dictated by both MgO and CaO contents. Increasing silica-undersaturation produces assemblages dominated by clinopyroxene and a high melt fraction at any given temperature, promoting alkali enrichment during melt evolution. Oxidising conditions enhance the crystallisation of spinel and other Fe-Ti oxides, in which both silica and alkalis are incompatible, through increased melt Fe&lt;sup&gt;3+&lt;/sup&gt;/ΣFe. This promotes more modest enrichments in Na&lt;sub&gt;2&lt;/sub&gt;O and K&lt;sub&gt;2&lt;/sub&gt;O with respect to SiO&lt;sub&gt;2&lt;/sub&gt; as crystallisation proceeds, with the effect strongest where bulk concentrations of FeO&lt;sub&gt;tot&lt;/sub&gt; are high and P&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; are low. It follows that &lt;i&gt;f&lt;/i&gt;O&lt;sub&gt;2&lt;/sub&gt; exerts a stronger control over the liquid lines of descent of more primitive liquids than evolved ones. We combine our results with those from the literature to calibrate new models for both &lt;span&gt;({K}_{{{rm D}}_{{{rm Fe}}^{2+}-text{Mg}}}^{{rm Ol}-{rm Melt}})&lt;/span&gt; and &lt;span&gt;({K}_{{{rm D}}_{{{rm Fe}}^{T}-text{Mg}}}^{{rm Ol}-{rm Melt}})&lt;/span&gt; in alkaline systems, with the latter formulated as:&lt;/p&gt;&lt;div&gt;&lt;div&gt;&lt;span&gt;$${K}_{{{rm D}}_{{{rm Fe}}^{T}-text{Mg}}}^{{rm Ol}-{rm Melt}}(pm 0.012, text{a.a.d.})=0.442 left(pm 0.029right)+0.287 left(pm 0.035right)left[{text{X}}_{{text{SiO}}_{2}}right]-0.442left(pm 0.027right)left[frac{{text{X}}_{{text{Na}}_{2}text{O}}+{text{X}}_{{{rm K}}_{2}text{O}}}{{text{X}}_{{text{SiO}}_{2}}}right]- 0.168left(pm 0.022right)left[{text{X}}_{text{Fo}}right]-0.138(pm 0.008)frac{1}{(1-left[frac{{text{Fe}}^{3+}}{Sigma text{Fe}}right])}$$&lt;/span&gt;&lt;/div&gt;&lt;/div&gt;&lt;p&gt;where &lt;span&gt;({text{X}}_{i})&lt;/span&gt; is the mole fraction of &lt;span&gt;(i)&lt;/span&gt; in ","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 6","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147808200","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}