Contributions to Mineralogy and Petrology最新文献

{"title":"Mineral chemistry of metasomatic haloes in granite: constraints on fluid chemistry during spodumene pegmatite crystallization","authors":"Elena Geiger,&nbsp;Julian Menuge,&nbsp;Teimoor Nazari-Dehkordi,&nbsp;Maurice Brodbeck","doi":"10.1007/s00410-026-02343-8","DOIUrl":"10.1007/s00410-026-02343-8","url":null,"abstract":"<div><p>Crystallizing spodumene pegmatites exsolve hydrothermal fluids, which generate exomorphic metasomatic halos in their host rocks. Composition, timing and frequency of fluid release relate to the evolution of the pegmatite. At the Moylisha prospect of the Leinster pegmatite belt in SE Ireland, spodumene pegmatites intrude the granite of the Leinster Batholith. Narrow (~ 10 cm) visible halos developed at the contact, but halo mineralization may occur meters away, isolated from pegmatite contacts. Two halo assemblages were identified using petrography, in situ chemistry and imaging of metasomatic minerals and textures. A rutile-present assemblage (ferroan muscovite-siderophyllite-feldspar-quartz-rutile) has rare alkali-enriched mica and contains accessory rutile. In the rutile-absent assemblage (ferroan muscovite–quartz–apatite ± siderophyllite ± feldspar) micas are Nb–Ta-enriched and have lower Nb/Ta ratios; apatite is abundant. The metasomatic evolution of both assemblages is modelled with a progressive reaction model as the interaction of the host rock with two distinct fluids. The rutile-present assemblage fluid is mainly enriched in rare alkalis and likely expelled after the onset of orthoclase and spodumene crystallization in the pegmatite but before resorption of primary minerals. The rutile-absent assemblage fluid additionally carries Nb, Ta, K and P and likely corresponds to the late hydrothermal stage of pegmatite evolution after partial resorption of primary minerals. Isolated halo mineralization has potential implications for mineral exploration as it can be detected distal to the pegmatite. The (mineral) chemistry of the halo has potential for distinguishing pegmatites where spodumene is preserved, from pegmatites that have undergone widespread albitization and spodumene resorption.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02343-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148695597","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":"Titanium diffusive isotope effects in Fe-bearing basalt","authors":"Bruna da Silva Ricardo,&nbsp;Neil R. Bennett,&nbsp;Xu Chu,&nbsp;Robert Webster,&nbsp;Nicolas Greber,&nbsp;Suzette Timmerman,&nbsp;Benjamin J. A. Moulton,&nbsp;Corliss Kin I Sio","doi":"10.1007/s00410-026-02345-6","DOIUrl":"10.1007/s00410-026-02345-6","url":null,"abstract":"<div><p>Titanium isotope systematics have been increasingly used as a tracer for magmatic processes. A knowledge gap is how Ti isotopes fractionate during chemical diffusion. The magnitude of diffusive fractionation is described by <i>β</i>, which correlates the diffusivities of isotopes to their inverse mass ratio. To determine <i>β</i>_Ti, we have conducted diffusion-couple experiments on Fe-bearing basaltic melts at 1380 °C and 1 GPa using a piston-cylinder press. The measured Ti isotopic variability arising from diffusion is ~ 0.4‰ (± 0.05‰, 2 SD), and the best-fit <i>β</i>_Ti is 0.022 ± 0.003 (2 SD). This value agrees with published values determined using Fe-free basalt analogues. A low <i>β</i>_Ti is consistent with Ti being strongly bound to the silicate network in basaltic melts, even if present in coordination numbers greater than four. Using this experimentally constrained <i>β</i>_Ti, we modeled isotopic fractionation during rapid olivine growth and boundary layer development. Under realistic magmatic conditions, the maximum δ⁴⁹Ti predicted is ~ 0.13‰. Titanium isotopes therefore have the potential to detect kinetic effects occurring in natural basaltic melts. </p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148695359","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":"A grain boundary diffusion model for the development of oscillatory zoning in garnet","authors":"Frank S. Spear,&nbsp;Joseph P. Gonzalez","doi":"10.1007/s00410-026-02354-5","DOIUrl":"10.1007/s00410-026-02354-5","url":null,"abstract":"<div><p>Oscillatory zoning in blueschist and eclogitic garnets has been interpreted as indicative of fundamental processes that occur in subduction zones such as the infiltration of external fluids, fluctuations in the temperature and/or pressure, the accumulation and release of strain, or a change in the identities of reacting phases. Although these processes may and probably do occur, they are not necessarily required to produce oscillatory zoning in garnet from subduction zones. The present contribution describes a 2-D numerical model that generates oscillatory zoning of Mn in garnet (compensated by zoning in Fe and, to a lesser degree, Ca and Mg) based not on the invocation of external agents such as the influx of fluids but simply on the relative rates of garnet growth and elemental fluxes resulting from grain boundary diffusion. The number of oscillations is governed by the number of cycles in which the ratio of diffusion to reaction (D/R) changes. The magnitude of the compositional change is a function of the magnitude of the change in this ratio, and the width of the oscillations is a function of the duration of the change in the ratio. It is proposed that oscillatory zoning in blueschist and eclogitic garnet is common because the temperature of formation is appropriate for variations in the grain boundary diffusion of Mn to be manifested in the composition of garnet. At higher temperatures (e.g., Barrovian conditions), the grain boundary diffusivity of Mn and other major elements is sufficiently rapid to prevent the creation of major oscillations. However, several studies have shown that oscillations may still be preserved in more slowly diffusing trace elements even in the absence of major element oscillations. As a case study, we apply this model to evaluate the development of oscillatory zones in garnets from a retrogressed blueschist from the Tillotson Peak Complex, Vermont, USA. Results from flux calculations suggest that oscillatory zones can be formed on decadal timescales potentially consistent with paleo-seismic cycles.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02354-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148750660","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":"Eruptive pulsing of maar and scoria cone clusters in the West Eifel volcanic field, Germany, during the last glacial maximum revealed by zircon (U-Th)/He dating of crustal xenoliths","authors":"Anne Sturm,&nbsp;Axel K. Schmitt,&nbsp;Martin Danišík,&nbsp;István Dunkl","doi":"10.1007/s00410-026-02351-8","DOIUrl":"10.1007/s00410-026-02351-8","url":null,"abstract":"<div><p>The West Eifel Volcanic Field (Germany) is the type locality of maars, a common volcano type in continental intraplate volcanic fields. Timescales of eruptive recurrence and spatiotemporal clustering of maars and scoria cones are critical to assess controls of melting, magma ascent, and venting in such fields. Here, we overcome limitations of conventional geochronometers to constrain these timescales through zircon (U-Th)/He dating of crustal xenoliths accidentally scavenged during magma ascent. Zircon U-Th-Pb crystallization ages distinguish metaigneous and metasedimentary xenolith provenance from Palaeozoic basement. The absence of pre-eruptive ⁴He in zircon was verified by dating petrologically diverse xenoliths from individual vents, yielding consistent results. Zircon (U-Th)/He eruption ages are: Meerfelder Maar (75 ± 4 ka, all 2σ), Mosenberg (78 ± 9 ka), Emmelberg (48 ± 3 ka), Daun maar group (23 ± 1 ka), Pulvermaar (25 ± 2 ka), Wartgesberg (23 ± 3 ka), Oberwinkler Maar (195 ± 7 ka), and Facher Höhe (25 ± 2 ka). Oberwinkler Maar falls into a previously postulated volcanic hiatus, whereas two volumetrically dominant clusters at c. 25 and 75 ka coincide with deposition of the Central European Eltville and Rocourt tephra markers. The onset of volcanic activity and its peak coinciding with the last glacial maximum correlate with progressive marine regression in the North Sea basin. This contradicts previous models linking volcanic upsurges to interglacial warming and sea level rise. Zircon (U–Th)/He dating of pyrometamorphic crustal xenoliths thus provides a robust chronological framework to improve knowledge about eruptive pulsing in intraplate volcanic fields.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02351-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148750661","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 role of fractional crystallization in the formation of unzoned Li-mineralized pegmatites: insights from in situ apatite geochemistry","authors":"Shuaijie Liu,&nbsp;Mei-Fu Zhou,&nbsp;Huan Chang,&nbsp;Bin Chen,&nbsp;Hui Zhao","doi":"10.1007/s00410-026-02348-3","DOIUrl":"10.1007/s00410-026-02348-3","url":null,"abstract":"<div><p>The role of fractional crystallization in the formation of unzoned Li-mineralized pegmatites remains poorly understood. Apatite crystallizes throughout the cooling history of pegmatitic melts and can preserve critical information on the properties of the initial melt and its subsequent evolution. In this study, we report in situ element and Nd isotope compositions of apatite from unzoned Li-mineralized pegmatites in the Altyn Tagh Orogen, northern Tibetan Plateau, to investigate their formation and mineralization processes. These pegmatites have Nd isotope compositions similar to those of coeval S-type granites, suggesting that pegmatitic melts are likely fractionated products of granitic melts. Texturally early apatite (Ap1) has positive Eu anomalies (Eu/Eu^* = 1.0–93), resulting from the depletion of Sm and Gd in the initial pegmatitic melts. This depletion may be due to fractionation of monazite and zircon within the nearby parent granitic melts prior to pegmatitic melt extraction, as supported by phase equilibrium modelling. Ap1 has elevated Li concentrations of &gt; 6 μg/g, which can be taken to discriminate Li-mineralized from barren pegmatites, indicating that fractionation of granitic melts leads to initial Li enrichment. Compared to Ap1, which is closely associated with plagioclase and contains information about the properties of the initial pegmatitic melts, Ap2 formed in a late stage and coexists with spodumene, montebrasite, and muscovite. Texturally late apatite (Ap2) has negative Eu anomalies (Eu/Eu^* = 0.001–0.9). The shift from positive to negative Eu anomalies in pegmatitic melts recorded in Ap1 and Ap2 reflects feldspar crystallization within the pegmatitic melts. Ap2 has higher Li concentrations than Ap1, indicating that in situ fractional crystallization further enriched Li, culminating in spodumene crystallization. Our study demonstrates that unzoned pegmatites experience significant in situ fractional crystallization after the emplacement of melts, which is crucial for their formation and Li-mineralization, akin to zoned pegmatites.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148750912","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":"High-pressure phase relations in the Mg–Fe–O system and the conditions at which ferropericlase inclusions in diamonds are formed","authors":"Caterina Melai,&nbsp;Daniel J. Frost,&nbsp;Tiziana Boffa Ballaran,&nbsp;Catherine A. McCammon,&nbsp;Nobuyoshi Miyajima,&nbsp;Lin Wang","doi":"10.1007/s00410-026-02341-w","DOIUrl":"10.1007/s00410-026-02341-w","url":null,"abstract":"<div><p>Constraints can be placed on the formation conditions of (Mg,Fe)_XO ferropericlase inclusions in natural diamonds based on their Fe³⁺ contents, given suitable knowledge of how these contents change with pressure, temperature, composition and oxygen fugacity. To achieve this, experiments have been conducted to determine the maximum Fe³⁺/Fe_tot ratio in ferropericlase, controlled by its coexistence with magnetite–magnesioferrite (Fe₃O₄–MgFe₂O₄) up to pressures of ~ 6 GPa, and with the high-pressure [Fe,Mg]₂Fe₂O₅ phase between 10 and 30 GPa. The experiments were performed between 1200 and 1800 °C and across a range of bulk Fe/(Fe + Mg) ratios. Mössbauer and electron energy loss spectroscopy were used to determine ferropericlase Fe³⁺/Fe_tot ratios, a task that is complicated by exsolution of nanocrystalline magnetite–magnesioferrite during quenching. Using these data, a thermodynamic model was developed that describes the entire range of ferropericlase compositions in the Mg–Fe–O system between 1 atmosphere and 30 GPa. It is shown that the Fe³⁺/Fe_tot ratio of ferropericlase within diamond-forming assemblages decreases strongly above 10 GPa, and that the majority of ferropericlase inclusions in diamonds with measured Fe³⁺/Fe_tot, have ratios too high for them to have formed in the lower mantle. Most of these ferropericlase inclusions have maximum formation depths in the transition zone, but a few of the most oxidised could only have formed in the upper mantle from oxidised precursors such as carbonates. We also show that high pressure (Fe,Mg)₂Fe₂O₅ and (Fe,Mg)₃Fe₂O₆ phases can become stable during diamond formation towards the base of the transition zone, when bulk Fe/(Fe + Mg) ratios are &gt; 0.5.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02341-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148614265","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":"Apatite records open-system evolution of jurassic granitoids in the Cathaysia Block, Southeast China","authors":"Bao-Quan Zhou,&nbsp;Jin-Hui Yang,&nbsp;Jin-Feng Sun,&nbsp;Jing-Yuan Chen","doi":"10.1007/s00410-026-02340-x","DOIUrl":"10.1007/s00410-026-02340-x","url":null,"abstract":"<div><p>Apatite is a robust recorder of open-system magmatic evolution in granitoids, as it may preserve subtle geochemical signals of magma compositional changes. Here, we integrate textural, compositional, and O-isotopic analyses of magmatic apatite from Jurassic granodiorites and biotite granites in the Cathaysia Block, Southeast China, to better constrain the nature and evolution of open-system magmatic processes and refine the petrogenesis of these granitic rocks. In granodiorites, O-isotope disequilibrium between apatite and zircon documents open-system magmatism: low-δ¹⁸O apatite (Group 1; 5.7–7.1‰; Δδ¹⁸O_{zircon–apatite} = +1.31‰) indicates greater mantle-derived input, whereas high-δ¹⁸O apatite (Group 2; 8.0–9.0‰; Δδ¹⁸O_{zircon–apatite} = -0.84‰) reflects enhanced supracrustal assimilation. In biotite granites, apatite and zircon are in near isotopic equilibrium (Group 3; 6.3–9.0‰; Δδ¹⁸O_{zircon–apatite} = -0.08–0.09‰ ), and δ¹⁸O differences among samples likely reflect variable proportions of mantle- and crust-derived components. Apatite core–rim zoning provides additional evidence for complex magma interaction: apatite in granodiorites shows abrupt core-to-rim decreases in REE, Y, and SiO₂, consistent with mafic recharge, while apatite in biotite granite displays opposite trends, reflecting hybridization with congenetic, more evolved felsic melts. Apatite trace-element systematics further track mineral–melt differentiation during magma evolution: decreasing Sr coupled with increasingly negative Eu anomalies reflects plagioclase fractional crystallization, whereas pronounced LREE depletion in apatite indicates early allanite crystallization. Together, these in situ textural, geochemical, and O-isotopic data highlight apatite as a powerful tracer of magma sources, open-system evolution, and differentiation processes in granitoids.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 7","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148381059","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":"Low-temperature, anhydrous (Fe-Ca)-rich garnets do not grow cubic: new evidence from blueschists of the Franciscan Complex (Cazadero, USA)","authors":"Sofia Lorenzon,&nbsp;Enrico Mugnaioli,&nbsp;Cristian Biagioni,&nbsp;Dominik C. Hezel,&nbsp;Kenneth J. T. Livi,&nbsp;Tommaso Tacchetto,&nbsp;Fabrizio Nestola,&nbsp;Bernardo Cesare","doi":"10.1007/s00410-026-02342-9","DOIUrl":"10.1007/s00410-026-02342-9","url":null,"abstract":"<div><p>Garnet is a key mineral of several metamorphic and igneous rock types in the lithosphere. Despite being traditionally considered the archetypal cubic mineral, crystallizing in <i>Ia</i><span>(:overline{3})</span><i>d</i> space group, there is increasing evidence that almandine and spessartine garnets from low-temperature metapelites and metabasites are optically anisotropic, and therefore possibly not cubic. Here, we study the best-known occurrence of optically anisotropic garnet - the metabasites of the Franciscan Complex (Cazadero, USA) - integrating polychromatic polarization microscopy (PPM), electron microprobe analysis (EMPA) with and without flank method for Fe³⁺/ΣFe estimation, field emission scanning electron microscopy coupled with focus ion beam (FIB−FESEM), electron energy-loss spectroscopy (EELS), single-crystal X-ray diffraction (SCXRD) and electron backscatter diffraction (EBSD). The result of this multi-analytical approach is a comprehensive optical, chemical and crystallographic characterization of these birefringent garnets. The Cazadero garnet has optical sector zoning according to twelve pyramidal sectors forming a rhombic dodecahedron. Within sectors, a concentric oscillatory zoning is also observed. From a chemical point of view, no sector zoning is detected, whereas the concentric oscillatory zoning is maintained. Chemical maps and profiles show a typical growth distribution characterized by a bell-shaped distribution of Mn. Considering the Fe³⁺ contents measured by both the EMPA flank method and EELS, a distinctive chemical zoning ranges from Alm₅₃Sps₂₀Grs₁₆Pyr₀₁Adr₁₀ in the core to Alm₆₆Sps₀₄Grs₂₀Pyr₀₃Adr₀₇ in the rim. Therefore, the analyzed garnets are almandine with a non-negligible andradite component, that reaches up to 10 mol%. Accurate X-ray diffraction refinements reveal that garnets are orthorhombic with <i>I</i>2/<i>a</i>12/<i>d</i> (<i>Fddd</i>) space group, with pseudo-tetragonal unit cell (<i>c</i> – <i>a</i> from − 0.009 Å to 0.014 Å). Symmetry lowering is due to Al-Fe³⁺ ordering within the octahedral sites, which is also supported by <i>Y</i> site distortion (difference in average &lt; <i>Y</i> – O&gt; distance from 0.0021 to 0.0041 Å). Our study provides new constraints on the origin of anhydrous almandine-rich garnets from low-grade metamorphic rocks occurring worldwide: we propose that their non-cubic structure (orthorhombic at Cazadero) is a growth feature, and is given by their Fe³⁺ content, coupled with low Mg and high Ca.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 7","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02342-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148323641","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":"Melt extraction and magma storage in the middle crust: insights from amphibole and apatite geochemistry in the Famatinian arc","authors":"Giuliano Camilletti,&nbsp;Juan Otamendi,&nbsp;Lorenzo Tavazzani,&nbsp;Julien Allaz,&nbsp;Olivier Bachmann","doi":"10.1007/s00410-026-02338-5","DOIUrl":"10.1007/s00410-026-02338-5","url":null,"abstract":"<div><p>Magma reservoirs in middle to upper crust play a crucial role in the evolution of continents and volcanic activity, yet their architecture, compositional evolution, and melt extraction mechanisms remain incompletely understood. The Valle Fértil batholith (VF), an exhumed section of the Ordovician Famatinian arc, provides an exceptional opportunity to investigate these processes in situ. This study integrates bulk-rock and mineral geochemistry (plagioclase, amphibole, quartz and apatite) with textural observations to reconstruct the magmatic evolution of the middle to upper part of the Famatinian arc section. Amphibole compositions reveal a systematic compositional evolution from Intermediate to Silicic lithological units, reflecting progressive differentiation. Trace element variations in amphibole indicate fractional crystallization as the dominant control on magma evolution. Apatite compositions record relative changes in oxygen fugacity of the system, and they capture the chemical evolution of the magmas as well as the amphibole. Chemometric reconstructions of amphibole equilibrium melts indicate derivation from dacitic to high-silica rhyolitic compositions, closely resembling silicic volcanic rocks from the Famatinian arc. These findings suggest that the middle crust of the Famatinian arc functioned as a vertically stratified magmatic distillation column, linking more mafic lower crustal units with high-silica magmas found in the upper crust, confirming the dominant role of trans-lithospheric differentiation columns in the evolution of arc crusts. </p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 7","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02338-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148323946","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":"An unexpected assemblage: Moissanite and carbonaceous material from SSZ mantle rocks of the Dun Mountain Ophiolite, New Zealand","authors":"Aerona Moore,&nbsp;Jonathan C. Aitchison,&nbsp;Andreas Hertwig,&nbsp;Trevor R. Ireland,&nbsp;Ashley Locke,&nbsp;Axel K. Schmitt,&nbsp;Renjie Zhou","doi":"10.1007/s00410-026-02339-4","DOIUrl":"10.1007/s00410-026-02339-4","url":null,"abstract":"<div><p>Moissanite (SiC) and other super-reducing minerals have been reported from supra-subduction zone (SSZ) ophiolites, yet their origin remains controversial given the oxidized conditions expected in forearc mantle. In this study, hundreds of moissanite grains have been recovered from mantle rocks of the Early Permian Dun Mountain Ophiolite, New Zealand. We report the first occurrence of moissanite found in direct association with disordered carbonaceous material (CM), which records low peak formation temperatures of &lt; 334 °C. Carbon isotope analyses reveal characteristic light compositions for both moissanite (δ¹³C = − 33.7 to − 19.2‰; mean − 25.0‰) and associated CM (δ¹³C = -39.2 to -29.0‰; mean − 35.3‰). The light C isotope signatures of both phases are consistent with moissanite formation via fractionation of ultra-reduced, carbon-rich fluids derived from organic-rich sediments carried by a subducting lithospheric slab. Preservation of moissanite in an oxidized forearc mantle could be aided by low temperatures and relatively short mantle residence times. Whilst the total mass of moissanite formed under these settings is low, these findings highlight the occurrence of localised ultra-reducing conditions at shallow depths in SSZ environments and identify an under-recognised pathway for carbon cycling in subduction zones.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"181 7","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-026-02339-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148281660","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}