Contributions to Mineralogy and Petrology最新文献

{"title":"Metasomatic ijolite, glimmerite, silicocarbonatite, and antiskarn formation: carbonatite and silicate phase equilibria in the system Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O–O2–CO2","authors":"Michael Anenburg,&nbsp;Jesse B. Walters","doi":"10.1007/s00410-024-02109-0","DOIUrl":"10.1007/s00410-024-02109-0","url":null,"abstract":"<div><p>Silicocarbonatites are carbonatite rocks containing &gt; 20% silicate minerals. Their formation is not well understood due to low silica solubility in carbonatite melts and negligible amounts of silicate minerals on carbonatite melt cotectics at upper crustal conditions. We explore whether silicocarbonatites can be thought of as antiskarns: rocks formed by leaching of SiO₂ from siliceous wall rocks by carbonatite melts, and its deposition as solid silicate minerals by reaction with chemical components already present in the carbonatite melt. Solid state thermodynamic modelling at 1–5 kbar and 500–800 °C predicts that calcite–dolomite–magnetite assemblages will transform to dolomite-free silicocarbonatites with an increase in silica contents. In sodic systems, the formation of aegirine and alkali amphiboles suppresses silica activity despite elevated silica contents. Therefore, dolomite remains stable, but Fe³⁺ is consumed, firstly from magnetite breakdown, and secondly by coupled Fe oxidation and reduction of CO₂ to CO, CH₄, and graphite, particularly at higher pressures. Despite a net increase in Fe³⁺/Fe²⁺, the system evolves to increasingly lower oxygen fugacity. In aluminous systems, nepheline indicates high temperatures whereas alkali feldspars form at lower temperatures. Modelling of potassic systems demonstrates stability of mostly phlogopite-rich biotites, leading to Fe²⁺ increase in all other carbonate and silicate phases. We find that perthites are expected in high pressures whereas two feldspars are more likely in lower pressures.</p><p>Aspects of the clinopyroxene natural compositional trend (diopside to hedenbergite to aegirine) of carbonatite systems can be explained by silica contamination. Ferrous clinopyroxenes typically require low alumina and are predicted in potassic or low temperature sodic systems, primarily at mid to high pressures. Silica contamination permits the formation of silicocarbonatite-like assemblages in a way that is not limited by SiO₂ solubility in carbonatite melts. Glimmerites and clinopyroxene-rich rocks (such as the ijolite series) that often occur around carbonatite rocks at the contact with silica-oversaturated wall rocks can be explained as the extreme end of silica contamination of carbonatite melts. Therefore, these clinopyroxenites and glimmerites can form solely via metasomatic processes without the presence of a silicate melt.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 5","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-024-02109-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140562156","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":"Lithium systematics in the Krafla volcanic system: comparison between surface rhyolites and felsic cuttings from the Iceland deep drilling project -1 (IDDP-1)","authors":"E. A. Cortes-Calderon,&nbsp;B. S. Ellis,&nbsp;T. Magna,&nbsp;L. Tavazzani,&nbsp;P. Ulmer","doi":"10.1007/s00410-024-02119-y","DOIUrl":"10.1007/s00410-024-02119-y","url":null,"abstract":"<div><p>The unexpected discovery of felsic magma by the Iceland Deep Drilling Project-1 (IDDP-1) in the Krafla volcanic system (KVS) presents a unique opportunity to investigate pre-eruptive lithium (Li) dynamics and establish a more direct connection between magma reservoirs and volcanic deposits. Our study provides new insights into Li abundances and isotope compositions in bulk-rock, minerals, and groundmass glass from rhyolitic lavas at KVS, encompassing various stages of groundmass crystallisation. Additionally, we examined felsic cuttings retrieved from the IDDP-1 well, comprising crystal-poor obsidian and crystal-bearing to -rich ‘felsite’ particles. Groundmass glasses from surface lavas show limited variability in K/Na, indicating limited secondary hydration of the glasses and that their Li contents seem to not be affected by this post-eruptive process. Lithium inventories in groundmass glasses and minerals within lavas exhibit variations consistent with the cooling history of the deposit, resembling patterns seen in Snake River Plain ignimbrites. Lithium contents of glassy rhyolitic lavas, whether bulk-rock (avg. 27.2 ± 3.1 μg/g) or groundmass glass (average 28.4 ± 4.7 μg/g), and their bulk isotopic compositions (avg. δ⁷Li =+ 4.4 ± 0.2‰) overlap with those observed in IDDP-1 obsidian cuts (avg. 24.9 μg/g Li in bulk, 28.6 ± 1.5 μg/g in groundmass glass, and δ⁷Li = 4.5 ± 0.2‰). Glassy lavas lacking spherulites may potentially preserve pristine magmatic Li element and isotope compositions, while areas with extensive groundmass crystallisation reveal Li enrichments in phenocrysts. Plagioclases in slowly cooled parts of the deposit record a two-fold increase in Li contents compared to plagioclase found in glassy counterparts, along with evidence of open-system degassing marked by heavier bulk Li isotope compositions and lower bulk Li contents of the crystallised lava portions (avg. δ⁷Li = +7.2 ± 0.1‰ and 7 ± 0.8 μg/g Li) relative to bulk glassy lithologies (avg. δ⁷Li = +4.1 ± 0.1‰ and 28 ± 2 μg/g Li). Partition coefficients derived from IDDP-1 cuts successfully predict Li inventories in vitrophyres of rhyolites on the surface of the KVS. Lithium isotope compositions of the crystal-rich IDDP-1 cuts are significantly heavier (avg. δ⁷Li = +7.2 ± 0.2‰) than lavas and IDDP-1 obsidian cuts, casting doubt on the notion that the IDDP-1 rhyolitic magma could result from the melting of felsite lenses in the KVS. Lithium contents in groundmass glasses within IDDP-1 crystal-rich cuts show higher Li contents (avg. 55.1–60.7 μg/g), correlating with the higher crystal content and an increase in other incompatible elements (avg. 250 μg/g Rb) relative to obsidian cuttings (avg. 75 μg/g Rb).</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 4","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-024-02119-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140561993","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":"Mineral-melt vanadium oxybarometry for primitive arc magmas: effect of hydrous melt composition on fO2 estimates","authors":"Saskia Erdmann,&nbsp;Michel Pichavant,&nbsp;Fabrice Gaillard","doi":"10.1007/s00410-024-02113-4","DOIUrl":"10.1007/s00410-024-02113-4","url":null,"abstract":"<div><p>If primitive arc magmas are primarily oxidized or if they acquire their oxidizing character during crustal evolution remains debated. Mineral-melt V partitioning is extremely redox sensitive and has the potential to resolve this debate, but critical low-temperature, hydrous experimental partitioning data are limited. We present new experimental V partitioning data for olivine-melt, spinel-melt, and clinopyroxene-melt based on the ≤ 1200 °C, hydrous basalt phase equilibrium experiments of Pichavant et al. (Geochim Cosmochim Acta 66:2193–2209, 2002) and Pichavant and Macdonald (Contrib Mineral Petrol 154:535–558, 2007). Combined with published experimental data, we use our olivine-melt V partitioning coefficients to show that—contrary to previous conclusions—hydrous melt composition, i.e. melt H₂O concentration in addition to the concentration of other melt components, affects V partitioning and thus calculated <i>f</i>O₂, systematically overestimating <i>f</i>O₂ for olivine-melt equilibrated at high melt H₂O concentration. False absolute <i>f</i>O₂ values and false oxidation or reduction trends may be inferred. Based on these findings, we have calibrated a set of new olivine-melt oxybarometers applicable to hydrous arc magmas partially crystallized at ~ 1025–1350 °C. In a case study on a high-Mg basalt from St. Vincent, Lesser Antilles, we show that olivine-melt V oxybarometry records oxidizing near-liquidus conditions (~ QFM + 1.8) and possibly limited oxidation (~ 0.3 log units) during intermittent crustal magma storage.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 4","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140561994","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 determination of Fe–Mg interdiffusion in orthopyroxene as a function of Fe content","authors":"Maria A. Dias,&nbsp;Ralf Dohmen","doi":"10.1007/s00410-024-02110-7","DOIUrl":"10.1007/s00410-024-02110-7","url":null,"abstract":"<div><p>We have measured the dependence of the Fe–Mg interdiffusion coefficient, <i>D</i>_Fe-Mg, on the ferrosilite component in orthopyroxene, which so far has not been experimentally calibrated. Diffusion couples, consisting of approximately 1 µm thin-films were deposited by pulsed laser ablation on orthopyroxene crystals of En₉₁Fs₉ composition. Diffusion experiments were carried out at atmospheric pressure in vertical gas mixing furnaces (CO-CO₂) at temperatures between 950 and 1100 °C at constant <i>f</i>O₂ = 10^–7 Pa. Using a focused ion beam-scanning electron microscope (FIB-SEM), FIB-foils were cut from diffusion couples before and after annealing. Diffusion profiles were extracted by using combined backscattered electron (BSE) imaging and energy dispersive X-ray (EDXS) mapping on FIB-foils which allowed to resolve concentration gradients within 20 nm. The microstructure of the diffusion experiments was investigated using transmission electron microscopy (TEM). Using this method, we obtained the first experimentally determined data on the dependence of <i>D</i>_Fe-Mg on the ferrosilite content in orthopyroxene at different temperatures, appearing to increase with increasing a temperature. For the temperature range (950 – 1100 °C), log <i>f</i>O₂ = -7 Pa, along [001] in the composition Fs9, the log <i>D</i>_Fe-Mg yields the following Arrhenius equation:</p><div><div><span>$$D_{Fe - Mg} [m^2 /s] = 3.8 cdot 10^{ - 9} exp [ - 261.07 pm 24[kJ/mol]/(R/T[K])]$$</span></div></div><p>The effect of <i>X</i>_Fe on <i>D</i>_Fe-Mg, given by <span>(D(X_{Fe} ) = D(X_{Fe} = 0.09) cdot {10}^{m (X_{Fe} - 0.09)},)</span> can be calculated by the following parameterization where <i>m</i> follows a linear regression of <i>m</i> on temperature: </p><div><div><span>$$m = - 2.711 cdot 10^4 /T(K) + 23.5408$$</span></div></div><p>By considering the <i>D</i>_Fe-Mg dependence on <i>X</i>_Fe, the timescales of natural processes obtained from modelling the compositional zoning of natural crystal may considerably differ from previously estimated timescales.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 4","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-024-02110-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140562151","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":"Towards an integrated texture toolkit, 1: unveiling the complex relationship between crystal shape and fabric in EBSD data","authors":"Ryan M. Currier,&nbsp;Tushar Mittal,&nbsp;Paulo J. Hidalgo","doi":"10.1007/s00410-024-02128-x","DOIUrl":"10.1007/s00410-024-02128-x","url":null,"abstract":"<div><p>Rock textures observed via thin section are skewed from their true 3D nature. This is due to various cut effects—artifacts introduced due to the lower dimensional nature of the thin section relative to the rock. These cut effects can be corrected, and several methods have been developed to invert crystal shape and crystal size, but with each process performed separately and sequentially. With the ongoing adoption of electron backscatter diffraction (EBSD) by petrologists, an additional data stream has now become available: the 3D orientation of 2D grain sections. For EBSD analysis, no stereological corrections are typically applied for interpreting the data. This study tests whether this orientational information is skewed due to a fabric cut effect. We test this by numerically generating synthetic crystal datasets representative of several crystal shapes and population sizes. We find that EBSD orientational data has a fabric cut effect since crystals oriented with long axes perpendicular to the thin section are more likely to be sampled compared to those with long axes oriented parallel to it. This effect must be accounted for to interpret the true 3D fabric accurately. Towards this end, we develop two new tools for working with EBSD-derived fabric: (1) a simple first-order test for determining if a measured fabric exceeds that of the fabric cut effect, and (2) a method of inverting cut fabrics that provides robust error estimations. We demonstrate the applicability and accuracy of these methods using a range of synthetic examples and a natural sample. With these newly developed tools, there is clear potential for a new textural toolkit framework, to further our ability to correct for the various cut effects while also providing accurate uncertainty estimates.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 4","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140562153","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":"Elastic thermobarometry on metapelites across the crustal section of the Famatinian Arc, Argentina","authors":"Emanuel Giovanini,&nbsp;Kenneth S. Befus,&nbsp;Juan E. Otamendi,&nbsp;Eber Cristofolini,&nbsp;Tomas Guerreiro,&nbsp;Miguel Cisneros","doi":"10.1007/s00410-024-02115-2","DOIUrl":"10.1007/s00410-024-02115-2","url":null,"abstract":"<div><p>We applied elastic thermobarometry on garnet-bearing migmatites along two transects through the crustal section at Sierra Valle Fértil-La Huerta, Argentina. We performed quartz-in-garnet barometry and zircon-in-garnet thermometry on metapelites from different paleo-depths across the crustal section. Our work recovers entrapment pressures ranging from 240 to 1330 MPa and entrapment temperatures between 691 and 1574 °C. The entrapment conditions are broadly consistent with anticipated pressures and temperatures along the crustal section derived previously using conventional, thermodynamic thermobarometers. The quartz-in-garnet barometer reproduces those conventionally established entrapment conditions when samples only experienced conditions within the alpha-quartz stability field. Raman-derived pressures for samples that experienced beta-quartz reference conditions are commonly much higher than those established by conventional barometry. Samples that preserve compressive (positive) residual pressures best reproduce reference entrapment pressures. Entrapment temperatures show high variability and overestimation of temperature conditions compared to conventional results. These results indicate elastic thermobarometry over- or under-estimates crystallization conditions in rocks crystallized at high temperatures, as is common in the Famatinian Arc deep-crust. We suggest that modeling quartz behavior across the alpha–beta transition may present challenges, as does shape maturation, viscous deformation, and radiation damage in zircon.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 4","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-024-02115-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140562013","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":"Lower crustal assimilation revealed by sulfur isotope systematics of the Bear Valley Intrusive Suite, southern Sierra Nevada Batholith, California, USA","authors":"Hervé Rezeau,&nbsp;Oliver Jagoutz,&nbsp;Patrick Beaudry,&nbsp;Benjamin. Z. Klein,&nbsp;Gareth Izon,&nbsp;Shuhei Ono","doi":"10.1007/s00410-024-02123-2","DOIUrl":"10.1007/s00410-024-02123-2","url":null,"abstract":"<div><p>The origin of the wide range of sulfur isotope compositions (i.e., δ³⁴S) measured in arc rocks remains debated. While the observed δ³⁴S variability has been attributed to slab-related fluids that flux the sub-arc mantle, others have argued that it primarily reflects crustal-derived processes by some combination of magmatic differentiation, country rock assimilation, and/or degassing. Here, we present new whole rock sulfur isotopes for the Late Cretaceous Bear Valley Intrusive Suite (BVIS) that represents a continuous arc crustal section in the southern Sierra Nevada Batholith, exposing lower crustal mafic cumulates and cogenetic mid-upper crustal tonalites. Our data reveal a range of δ³⁴S-depleted values (–1.2 to − 5.1‰) for the BVIS with overlapping δ³⁴S between mafic cumulates and tonalites. Complementary δ³⁴S measurements of structurally concordant metasedimentary pendants indicate δ³⁴S-depleted values (–11.5 to − 5.2‰) for deep metasedimentary rocks compared to δ³⁴S-enriched values (+ 1.6 to + 6.4‰) for shallower ones. Quantitative mixing models suggest that assimilation of crustal-derived sulfur from metasedimentary rocks in the lower crust can account for the δ³⁴S-depleted values in the BVIS, whereas assimilation of shallower ones is unlikely. Sulfur degassing modelling indicates that the range of δ³⁴S-depleted values observed within mid-upper crustal tonalites can be reproduced by degassing  ~60–80% of the initial melt sulfur at <i>f</i>O₂ ≤ FMQ + 1 with initial H₂O content of 10–12 wt%. Finally, the identical ranges of δ³⁴S values within the tonalites and mafic cumulates argue for limited sulfur isotope fractionation related to magmatic sulfide immiscibility. Although assimilation, magma degassing and sulfide immiscibility are not mutually exclusive during crustal magmatic processes, field, thermal and geochemical evidence favor lower crustal-derived sulfur assimilation as the primary mechanism to explain the range of δ³⁴S- depleted values within the mafic cumulates, which are ultimately inherited by the derivative tonalitic melts. Overall, this study emphasizes that deep crustal magmatic processes can severely influence the early δ³⁴S evolution of arc magmas.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 4","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140366383","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":"Incorporation mechanisms and infrared absorption coefficients of water in MgSiO3 orthoenstatite clarified via comprehensive NMR and vibrational spectroscopic measurements, and first-principles calculations","authors":"Xianyu Xue,&nbsp;Masami Kanzaki,&nbsp;Abd-Erraouf Djirar,&nbsp;Chris Gregson","doi":"10.1007/s00410-024-02114-3","DOIUrl":"10.1007/s00410-024-02114-3","url":null,"abstract":"<div><p>We performed ¹H and ²⁹Si NMR and infrared measurements, and first-principles calculations to clarify the nature of OH defects in MgSiO₃ orthoenstatite. An orthoenstatite sample synthesized at 7 GPa and 1200 °C from a composition of MgSiO₃ + 0.1 wt% H₂O yielded two ¹H MAS NMR peaks near 5.9 and 7.6 ppm that are correlated in 2D NMR spectra, and two infrared bands near 3361 and 3066 cm^− 1 that correspond to the previously reported A3 and A4 bands. The first-principles calculations confirmed that they are due to a pair of protons in a Mg (M2) vacancy. The previously reported A1 and A2 infrared bands near 3687 and 3592 cm^− 1 for orthoenstatite synthesized at low silica activities were confirmed to arise from four protons in a SiB vacancy. The latter is predicted to give two additional OH stretching bands associated with two strongly hydrogen-bonded O3b-H bonds with frequencies below the spectral range reported thus far. The previously reported infrared absorption coefficients were thus revised to account for the undetected bands. ¹H NMR may be used to quantitatively detect all four protons (expected at 1–12 ppm). Other mantle minerals should also be examined for potentially overlooked OH defects with strong hydrogen bonding.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 4","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-024-02114-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140298347","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":"From source to surface: clues from garnet-bearing Carboniferous silicic volcanic rocks, Iberian Pyrite Belt, Portugal","authors":"A. Cravinho,&nbsp;D. Rosa,&nbsp;J. M. R. S. Relvas,&nbsp;A. R. Solá,&nbsp;I. Pereira,&nbsp;J.-L. Paquette,&nbsp;M. L. Borba,&nbsp;C. C. G. Tassinari,&nbsp;D. Chew,&nbsp;F. Drakou,&nbsp;K. Breiter,&nbsp;V. Araujo","doi":"10.1007/s00410-024-02106-3","DOIUrl":"10.1007/s00410-024-02106-3","url":null,"abstract":"<div><p>This work investigates the relationships between partial melting, melt extraction, pluton growth and silicic volcanism in garnet-bearing felsic volcanic rocks that were extruded in the Iberian Pyrite Belt, at ca<i>.</i> 345 Ma. The garnets are of peritectic origin, displaying textural and chemical features of disequilibrium crystallization during partial melting reactions involving biotite at high temperatures (up to 870 °C) in the middle-lower crust. Major element composition suggests compositional equilibrium with the entrained and pinitized peritectic cordierite, but reveals some subsequent homogenization by diffusion. Trace element maps and spot analyses of garnet show, nonetheless, significant trace element variations, reflecting biotite and Y-REE-P-rich accessory phase breakdown during partial melting reactions. Peritectic garnet and cordierite growth resulted in the preservation of Th- and Y-rich prograde suprasolidus monazite, which constrains the timing of partial melting of the metapelitic protolith at <i>ca.</i> 356.8 ± 2.4 Ma. The zircon cargo further shows that a significant amount of zircon crystals from previously crystallized felsic melts were also remobilized and erupted. These were likely stored in an upper crustal pluton that grew episodically since ca<i>.</i> 390 Ma during voluminous melt generation periods within the middle to lower crust, which also resulted in voluminous volcanism. The geochemical trends of the felsic volcanic rocks reflect the entrainment of xenoliths of peritectic garnet, cordierite and feldspar, and as such, the garnet-bearing felsic volcanic rocks represent an erupted mixture of a lower-temperature (<i>ca.</i> 770 °C) silicic melt and autocrysts, and peritectic phases and zircon crystals from previously crystallized and stored felsic melts.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 4","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-024-02106-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140172957","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":"Crystallisation of trapped carbonate–silicate melts terminating at the carbonated solidus ledge: a record of carbon immobilisation mechanism in the lithospheric mantle","authors":"Jakub Haifler,&nbsp;Jana Kotková,&nbsp;Renata Čopjaková","doi":"10.1007/s00410-024-02108-1","DOIUrl":"10.1007/s00410-024-02108-1","url":null,"abstract":"<div><p>Orogenic peridotites in the crystalline basement of the northwestern Bohemian Massif contain multiphase solid inclusions (MSI), which are interpreted to be crystallisation products of trapped former carbonate–silicate melts metasomatizing their host rocks. We applied conventional thermobarometry and forward thermodynamic modelling to constrain the P–T evolution ranging from the peak metamorphic conditions of the investigated harzburgite and lherzolite, through entrapment of the melts in the outer parts of garnets, to the (re)-equilibration of the MSI assemblages. The peak conditions of c. 1100 °C/4.5–5.5 GPa are recorded by garnet cores and large pyroxene porphyroclasts. The melt entrapment, during which garnet outer parts grew, was associated with influx of the metasomatizing liquids and probably took place during the early stage of the exhumation. Thermodynamic model of amphibole-free MSI assemblage comprising <i>kinoshitalite/Ba-rich phlogopite</i> (approximated by <i>phlogopite</i> in the model), <i>dolomite, magnesite, clinopyroxene, orthopyroxene, garnet</i> and <i>chromite</i> provided robust estimate of P and T of its (re)-equilibration, c. 900–1000 °C, 1.8–2.2 GPa. Furthermore, the lack of olivine reflects co-existence of COH fluid with high X(CO₂) = CO₂/(CO₂ + H₂O) ≥ 0.6. Models employing identical P–T–X(CO₂) parameters successfully reproduced the other two amphibole-bearing assemblages observed. The modelled stability fields show perfect alignment with a characteristic isobaric segment of the solidus curve of carbonated peridotite. This co-incidence implies that the (re)-equilibration corresponds to the termination of the melt crystallisation once the near-isothermal exhumation path intersected the solidus. Decreased solubility of silicates at the carbonated peridotite “solidus ledge”, inferred from the published experimental data, as well as concentric textures of some MSI indicates sequential crystallisation from the early silicates to late dolomite. The carbonated “solidus ledge” is a relatively narrow boundary in the lithospheric mantle capable of an abrupt immobilisation of fluxing or transported carbonated melts. The investigated rocks are estimated to store approximately 0.02 kg C/m³ (or 6 ppm C) occurring as carbonates in the MSI.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 4","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-024-02108-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140171625","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}