Geochemistry Geophysics Geosystems最新文献

{"title":"Environmental and Calcification Impacts on the δ18O and δ2H Values of Cold-Water Coral Skeleton Fluid Inclusions","authors":"Yao Wu,&nbsp;Dana Hölkermann,&nbsp;Amrei Grund,&nbsp;Sophie Warken,&nbsp;Norbert Frank","doi":"10.1029/2024GC011981","DOIUrl":"https://doi.org/10.1029/2024GC011981","url":null,"abstract":"<p>Coral skeletons exhibit a complex composition of mineral and organic components, with the water content playing a significant role in their structure. Water associated with organic matrices constitutes the major share, whereas nonstructural water (skeleton inclusion water) is present in much smaller amounts, typically less than 0.5 wt% of the coral skeleton. The isotopic composition of this water may reflect biomineralization processes or environmental conditions during skeleton formation. Here, we present fluid inclusion hydrogen and oxygen isotopic compositions of cold-water coral skeletons from Angola and Iceland. We confirmed the kinetic isotope fractionation when coral skeletons were crushed at a temperature of 120°C using a cavity ring-down spectroscopy analyzer. δ¹⁸O and δ²H values are not reproducible across analytical setups with varying temperature parameters. When coral fragments are encapsulated in a glass tube, the amount of released water and its isotopic signature are far more reproducible. δ¹⁸O and δ²H values of coral skeleton inclusion water from Angola show no significant differences between the Holocene and the last glacial period. The δ²H values are characterized by strong isotopic fractionation compared to seawater. Our study highlights that current methods do not adequately capture the variability in the initial δ¹⁸O and δ²H of the “quasi-free” skeleton inclusion water in coral aragonite. It is also possible that there are varying degrees of exchange of skeleton inclusion water with seawater. A better understanding of the coral calcification process is still necessary to establish a clearer link between the isotopic compositions of seawater and skeleton inclusion water.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 6","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011981","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144473152","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":"Tracking the Caribbean Magmatic Evolution: The British Virgin Islands as a Transition Between the Greater and Lesser Antilles Arcs","authors":"Noémie Bosc,&nbsp;Delphine Bosch,&nbsp;Mélanie Noury,&nbsp;Olivier Bruguier,&nbsp;Lény Montheil,&nbsp;Douwe J. J. van Hinsbergen,&nbsp;Jean-Jacques Cornée,&nbsp;Jonathan Outin,&nbsp;Mélody Philippon","doi":"10.1029/2024GC012057","DOIUrl":"https://doi.org/10.1029/2024GC012057","url":null,"abstract":"<p>The British Virgin Islands (BVI) archipelago, located between the Greater Antilles and the Lesser Antilles, is a key location to study the geodynamic evolution of the Caribbean plate. Geochemistry of the studied samples reveals typical volcanic arc signatures, including a calc-alkaline affinity, strong negative HFSE anomalies, and LILE enrichment. The ɛHf values are homogeneous, indicative of a MORB-type mantle. Magmas were sourced from a homogeneous mantle wedge with less than 2% slab-derived sediment inputs, dominated by aqueous fluids. A concomitant melt component has been detected in the Peter and Norman Islands. U-Pb dating emphasizes an active magmatic period spanning over ca. 13 Myr (43–30 Ma), with a NE/SW decreasing age gradient. Thermobarometry data display a SW increasing emplacement depth from ∼6 to 13 km. Compared to the Greater and Lesser Antilles, this archipelago shows strong similarities with the extinct northern Lesser Antilles arc in terms of source and age. A geodynamical evolution model is proposed in which this archipelago represents a transition between the Greater and the Lesser Antilles arcs. The Oligocene cessation of magmatism (ca. 30 Ma) may coincide with a regionally documented lull in arc magmatic activity during which the Bahamas bank collided to the north. Paleomagnetic evidence of forearc sliver motion along the northeastern boundary of the Caribbean indicates a northward translation of the archipelago from a position above the Lesser Antilles subduction zone to its modern location along the highly oblique, strike-slip-dominated plate boundary, thus preventing the re-establishment of arc magmatism in the eastern Caribbean.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 6","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012057","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144315039","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":"Petrochronology of Alkaline Intrusive Magmatism in the Central High-Atlas (Morocco) and Relationships With Jurassic Salt Diapirism","authors":"Youssef Ahechach,&nbsp;Muhammad Ouabid,&nbsp;Françoise Roger,&nbsp;Fleurice Parat,&nbsp;Otmane Raji,&nbsp;Jean-Marie Dautria,&nbsp;Valérie Bosse,&nbsp;Cheikh Elwali Malainine,&nbsp;Hicham El Messbahi,&nbsp;Hamza Skikra,&nbsp;Jean-Louis Bodinier","doi":"10.1029/2025GC012178","DOIUrl":"https://doi.org/10.1029/2025GC012178","url":null,"abstract":"<p>A striking feature of the Imilchil alkaline province, in the Moroccan Central High Atlas, is the close association of magmatic intrusions with Triassic sediments exhumed by diapirism. This study reports field, petrographic, geochemical and Sr-Nd isotopic data, as well as new U-Pb zircon ages, which allow us to constrain the timing of the intrusions and to discuss their relationship to diapiric structures and the magmatic and hydrothermal processes. Our results indicate a restricted range of Late Jurassic ages (ca. 163 ± 1—ca. 149 ± 2 Ma) for the paroxysm of magmatic activity and confirm the diachronicity between diapirism and magmatism, albeit with a short interval of only a few My between the end of diapirism and the magmatic paroxysm. Deep-seated faults associated with transtensional tectonics, accommodating the increasing spreading rate of the Central Atlantic during the Jurassic, played a key role in the close association of magmatic intrusions with diapirs. The faults first triggered active diapirism in the Early- Jurassic and then guided OIB-type partial melts formed by local decompression melting of the mantle. At shallower depths, the diapiric structures acted as corridors for magma migration, probably using evaporites as preferential pathways. Magmas underwent fractional crystallization and interacted with evaporites to produce pervasive Na-rich hydrothermal fluids.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 6","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012178","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144315040","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 Uplift of Armorica and the Bretonian Movements of the Variscan Orogeny-New Insights From Detrital Zircons in the Early Carboniferous Terrigenous Rocks of the Laval Basin (Armorican Massif, France)","authors":"Wei Lin,&nbsp;Michel Faure,&nbsp;Lingtong Meng","doi":"10.1029/2024GC011944","DOIUrl":"https://doi.org/10.1029/2024GC011944","url":null,"abstract":"<p>In the French Armorican Massif, the Bretonian phase of the Variscan orogeny has been defined by the Late Devonian (Famennian-Frasnian) erosion gap, and the Early Carboniferous (Tournaisian) syntectonic terrigenous deposits of the l’Huisserie formation in the Laval basin in the Central-North Armorican Domain, ascribed to the Armorica microcontinent. This phase is coeval with vertical (epeirogenic) movements. In addition to Neo-, and Paleo-Proterozoic peaks, ascribed to the Cadomian and Icartian events, respectively, the detrital zircon age populations of the l’Huisserie formation reveal the existence of a 388–358 Ma magmatic event previously recognized by the ca 367–360 Ma dolerite dyke swarms exposed in the N. part of the Central-North Armorican Domain. The isotopic (εHf) signature of these grains documents a pre-orogenic Variscan mantle contribution for the mafic magmatism interpreted here as the indication of the south-directed subduction of the Le Conquet-Teplá ocean, that is, a branch of the Rheic ocean, below the Armorica microcontinent during the Bretonian phase. The intraplate opening of the Laval, Ménez-Bélair, and Châteaulin basins was coeval with this subduction. In the Laval area, the final closure of the basin, accommodated by north-directed folds-and-thrusts, took place after the Bashkirian (ca 320 Ma).</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 6","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011944","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144315103","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":"Geomagnetic Excursions Recorded in North Atlantic IODP Expedition 395C Sites U1555 and U1563","authors":"Anita Di Chiara,&nbsp;Sara Satolli,&nbsp;Sarah A. Friedman,&nbsp;Deepa Dwyer,&nbsp;Gary D. Acton,&nbsp;Tom Dunkley Jones,&nbsp;Boris Theofanis Karatsolis,&nbsp;Paul N. Pearson,&nbsp;Takuma Suzuki,&nbsp;Sevasti Modestou,&nbsp;Suzanne O'Connell,&nbsp;Halima Ibrahim,&nbsp;Claire E. Jasper,&nbsp;Danielle E. LeBlanc,&nbsp;Saran Lee-Takeda,&nbsp;Thena Thulasi,&nbsp;Deborah E. Eason,&nbsp;Matthias Sinnesael,&nbsp;Katharina Hochmuth,&nbsp;Anne Briais,&nbsp;Ross Parnell-Turner,&nbsp;Leah J. LeVay,&nbsp;Expedition 395C/395 Science Party","doi":"10.1029/2025GC012220","DOIUrl":"https://doi.org/10.1029/2025GC012220","url":null,"abstract":"<p>By studying deep-sea drilled records from the North Atlantic Ocean, several magnetic instabilities of short duration, such as the Iceland Basin (188 ka), the Björn (1,255 ka) and the Gardar (1,460 ka) excursions, were discovered. These records have contributed to our understanding of Earth's magnetic field and are the foundation of the Geomagnetic Instability Time Scale (GITS) in the Quaternary. Here, we present the magnetostratigraphy from Sites U1555 (0 to ∼2.7 Ma) and U1563 (0 to ∼5.2 Ma) drilled during the International Ocean Discovery Program Expedition 395C on the eastern side of the modern Mid-Atlantic Ridge (∼60°N, 20–30°W). Shipboard paleomagnetic and microfossil data provided a preliminary age model, extending the regional record to 3.4 Ma. The Virtual Geomagnetic Pole latitudes from archive halves, corroborated with data from discrete samples, were used to build a high-resolution magnetostratigraphy, which contained the expected Brunhes and Matuyama Chrons and their respective Subchrons. We also identified most of the magnetic events reported in the GITS, including the less well-documented ones, such as Osaka, Kamitzukara, Huckleberry Ridge, Reunion, Gardar, Halawa and L4 events. The high-resolution magnetostratigraphy from Sites U1555 and U1563 is compared with two previous legacy sites and contributes toward an increasingly robust GITS, expanding its use as a correlation and dating tool.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 6","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012220","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144309017","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":"Using Kgen to Generate Cross-Verified Apparent Equilibrium Constants (K∗’s) for Palaeoseawater Carbonate Chemistry","authors":"Ross Whiteford,&nbsp;Oscar Branson,&nbsp;Dennis Mayk","doi":"10.1029/2023GC011417","DOIUrl":"https://doi.org/10.1029/2023GC011417","url":null,"abstract":"<p>Quantification of palaeo pH and palaeo CO₂ from marine proxies requires the use of apparent equilibrium constants (K^∗’s). The K^∗’s required to calculate seawater carbonate chemistry are described by empirically determined calibrations, and for palaeoseawater these calibrations must be adjusted to account for changes in seawater composition. There are a number of possible calibrations that can be used to calculate K^∗’s, and each software package for calculating carbonate chemistry separately implements these K^∗ calibrations, which are manually verified against previous implementations. Palaeo applications typically only implement a single calibration for each K^∗, but have additional complexity from the need to adjust each calibration for changing seawater composition through time. The fragmented approach to K^∗ calculation can result in unintended and difficult to resolve discrepancies between outputs calculated by different pieces of software. We present “Kgen,” a synchronised collection of three pieces of software to consistently calculate palaeoseawater K^∗’s in Python, R, and Matlab. Kgen provides a simple, and nearly identical interface in each language. Through use of a Continuous Integration/Continuous Delivery (CI/CD) pipeline, Kgen guarantees consistent outputs between languages by automatically cross-checking results from all three implementations. Unifying the approach to K^∗ calculation in this way provides an extensible platform for verifiable K^∗ generation for palaeoseawater, which can be integrated into existing carbon speciation calculators to improve the consistency of results.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 6","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GC011417","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144244759","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":"Pulsed Injections of Metal-Rich Magmatic Fluids: Key Drivers of Mineralization in a Back-Arc Basin Hydrothermal System","authors":"Xia Zhang,&nbsp;Zhilei Sun,&nbsp;Yachun Cai,&nbsp;Yue Xu,&nbsp;Nengyou Wu,&nbsp;Hong Cao","doi":"10.1029/2025GC012318","DOIUrl":"https://doi.org/10.1029/2025GC012318","url":null,"abstract":"<p>Submarine magmatic–hydrothermal systems, where magmatic volatiles and fluids possibly serve as major sources of mineralization elements, have been extensively documented in numerous felsic-hosted hydrothermal fields. Previous studies have primarily focused on the contribution of magmatic volatiles in such hydrothermal systems. Although evidence has indicated that magmatic fluids have a greater capacity for transporting metals to overlying hydrothermal systems, their specific role in magmatic–hydrothermal systems remains inadequately understood. This study provides compelling evidence for the contribution of metal-rich magmatic fluid to the Minami–Ensei (ME) hydrothermal system. Pulsed injections of metal-rich magmatic fluids into the overlying hydrothermal system during mineralization process result in the elevated salinity (6.1–9.7 wt.% NaCl equiv) and <i>δ</i>¹⁸O values (1.1–8.0‰) in ME hydrothermal fluids, which are recorded by barite fluid inclusions and oxygen (O) isotope compositions, respectively. Laser-induced breakdown spectroscopy analysis indicated that the magmatic fluids injected into the ME were likely Fe-rich. Metal concentrations in magmatic fluids are several orders of magnitude higher than those in hydrothermal fluids generated via leaching, and their contribution to overlying hydrothermal systems can substantially enhance sulfide mineralization efficiency in magmatic–hydrothermal deposits. This study underscores the potential of magmatic–hydrothermal systems as promising targets for future sulfide ore exploration.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 6","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012318","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144237301","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":"3D Reconstruction of Complex Fault Systems From Volumetric Geodynamic Shear Zones Using Medial Axis Transform","authors":"Anthony Jourdon,&nbsp;Dave A. May,&nbsp;Jorge N. Hayek,&nbsp;Alice-Agnes Gabriel","doi":"10.1029/2025GC012169","DOIUrl":"https://doi.org/10.1029/2025GC012169","url":null,"abstract":"<p>Reconstructing fault surfaces from volumetric data is a longstanding challenge in geosciences. We present a novel 3D method based on the medial axis to transform a volumetric strain-rate invariant field from long-term geodynamic simulations into fault surfaces. In these geodynamic models, faults correspond to regions of locally high values of the second invariant of the strain-rate commonly referred to as shear zones. The proposed workflow begins by normalizing the strain-rate to define fault indicator field <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>ξ</mi>\u0000 </mrow>\u0000 <annotation> $xi $</annotation>\u0000 </semantics></math>. An iso-surface of a chosen <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>ξ</mi>\u0000 </mrow>\u0000 <annotation> $xi $</annotation>\u0000 </semantics></math> value is then extracted to form an envelope around the shear zones. Using the shrinking ball algorithm (Ma et al., 2012, https://doi.org/10.1007/s00371-011-0594-7), we compute the medial axis of this 3D envelope to generate a point cloud representing the geometric skeleton of the shear zones. We reconstruct fault surfaces by applying Delaunay triangulation followed by Laplacian smoothing. For models involving multiple intersecting faults, we perform a local principal component analysis (PCA) of the coordinates defining the medial axis and use the resulting eigenvectors to detect first-order orientation variations, enabling the separation and individualization of faults. We demonstrate the generality and robustness of the method by applying it several diverse 3D geodynamic scenarios: A single strike-slip fault, a branching strike-slip fault in a restraining bend, a dense strike-slip fault network, a rift system, and a subduction zone with a megathrust and a conjugate thrust fault.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 6","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012169","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144237300","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":"Thickening Cratonic Lithosphere by Horizontal Compression in the Presence of Surface Erosion and Sedimentation","authors":"Kristina Kublik,&nbsp;Claire A. Currie,&nbsp;D. Graham Pearson","doi":"10.1029/2025GC012194","DOIUrl":"https://doi.org/10.1029/2025GC012194","url":null,"abstract":"<p>Here we examine how lithospheric thickening is affected by active surface sedimentation and erosion in geodynamic models of craton formation—an aspect that has been neglected in previous models even though cratons may be the first landmasses to emerge above sea level. In our two-dimensional numerical models, inward horizontal velocities are imposed at the side boundaries of the model domain to induce thickening of the cratonic lithosphere by horizontal compression. Various rates of sedimentation and erosion are applied at the surface and the thickness of the lithosphere is monitored during the 50 Myr compression phase, and for 2 billion years after the imposed compression phase. In our models, surface processes act on the high-relief surface topography of the mobile belts adjacent to the cratonic nucleus. Erosion in the mobile belts during the compression alters lithosphere geodynamics, increasing the thickness of the mobile belt lithosphere to depths capable of supporting diamond growth. This enhanced thickening in the mobile belt regions limits shortening and thickening of the cratonic nucleus and the lithospheric thickness can vary by up to 15 km between models with different surface process rates.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 6","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012194","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144220040","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":"Origin of Silicic Magmatism at the Katla Volcanic Complex, South Iceland","authors":"Valentin R. Troll,&nbsp;Frances M. Deegan,&nbsp;Jussi S. Heinonen,&nbsp;Caroline Svanholm,&nbsp;Chris Harris,&nbsp;Christian M. Lacasse,&nbsp;Harri Geiger,&nbsp;Agata Poganj,&nbsp;Louise Thomas,&nbsp;Malin Andersson,&nbsp;Romain Meyer,&nbsp;Thorvaldur Thordarson","doi":"10.1029/2025GC012319","DOIUrl":"https://doi.org/10.1029/2025GC012319","url":null,"abstract":"<p>The Katla volcano is a bimodal caldera complex within Iceland's basalt-dominated Eastern Volcanic Zone. To unravel the petrogenesis of silica-rich rocks from Katla, we provide new δ¹⁸O values for almost 60 basaltic, intermediate, and high-silica eruptive rocks, including a number of partially melted felsic xenoliths. The basaltic samples display a range in bulk-rock δ¹⁸O values from +4.3 to +8.5‰ (<i>n</i> = 17) and the sparse intermediate samples from +4.1 to +5.9‰ (<i>n</i> = 3). In turn, silicic rock samples and feldspar separates range from +2.7 to +6.4‰ (<i>n</i> = 38), whereas felsic xenoliths yield the lowest values from −4.9 to −2.3‰ (<i>n</i> = 4). The majority (95%) of the Katla silicic volcanics have δ¹⁸O values below typical MORB (i.e., ≤5.0‰), ruling out an origin via closed-system fractional crystallization from the basaltic magmas. We utilized the new δ¹⁸O values to model possible assimilation and fractional crystallization (AFC) scenarios. The results indicate an early stage of FC/AFC at deep- to mid-crustal levels, followed by assimilation of low-δ¹⁸O hydrothermally altered sub-volcanic materials similar to the low-δ¹⁸O felsic xenoliths at shallow crustal levels. Such a two-stage magma evolution is consistent with available geophysical and geobarometry studies at Katla, indicating mid- to deep-crustal and shallow-crustal magma domains. Importantly, mafic rocks dominantly show MORB-like δ¹⁸O values, whereas low δ¹⁸O values occur essentially in silicic rocks only. This implies that the low-δ¹⁸O values at Katla are imposed by interaction with the Icelandic crust rather than reflecting low δ¹⁸O mantle sources.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 6","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012319","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144220039","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}