Geochemistry Geophysics Geosystems最新文献

{"title":"Disentangling Impact Ejecta Dynamics Using Micro–X-Ray Fluorescence (μ-XRF): A Case Study From the Terrestrial Cretaceous-Paleogene (K-Pg) Boundary","authors":"Pim Kaskes,&nbsp;Roald Tagle,&nbsp;Mariia Rey,&nbsp;Steven Goderis,&nbsp;Sophie Decrée,&nbsp;Jan Smit,&nbsp;Philippe Claeys","doi":"10.1029/2024GC012151","DOIUrl":"10.1029/2024GC012151","url":null,"abstract":"<p>This study presents a non-destructive geochemical and petrographic workflow to generate high-resolution chemostratigraphic records across key stratigraphic intervals, exemplified by a terrestrial Cretaceous-Paleogene (K-Pg) boundary sequence preserved at Starkville South (Raton Basin, Colorado, USA). To fingerprint specific Chicxulub impact ejecta and to unravel their mode and timing of deposition, we combined high-resolution (25 μm) micro-X-ray fluorescence (μ-XRF) mapping and quantitative integrated-area linescans with scanning electron microscopy. A complex microstratigraphy is observed at Starkville South in which additional sublayers are identified in contrast to the classic “dual-layer” succession described in the literature for US Western Interior K-Pg sites. First, a basal claystone occurs with abundant glassy impact spherules that were altered over time to kaolinite and jarosite due to acidic and reducing conditions in a local swamp. This first lithology is followed by a carbonaceous shale rich in ejected quartz grains. These two ejecta intervals are interpreted to have formed primarily by ballistic transport from the Chicxulub impact structure and were likely emplaced within ∼1 hr after impact at Starkville South. In the overlying lignite, pronounced enrichment in zirconium and chromium are detected, hinting at an ejecta sequence containing three distinct sublayers with a large part of the siderophile element anomaly being likely preserved at the base of this coaly interval, including the famous iridium anomaly. These enrichments are attributed to fine-grained impact dust composed of pulverized granitoid basement (Zr) and an admixture of meteoritic material (Cr, Ni, and likely Ir), probably deposited &lt;20 years after impact following slow atmospheric settling.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012151","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144814699","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":"Lava Lake Spattering Drives Seismic Tremor During the Geldingadalir 2021 Eruption, Iceland","authors":"Alea Joachim,&nbsp;Eva P. S. Eibl,&nbsp;Daniel Müller,&nbsp;Thomas R. Walter,&nbsp;Tom Winder,&nbsp;Nicholas Rawlinson","doi":"10.1029/2024GC012084","DOIUrl":"10.1029/2024GC012084","url":null,"abstract":"<p>Volcanic eruptions generate a continuous ground motion that is commonly referred to as tremor. Although tremor is used worldwide for real-time monitoring of volcanoes, the mechanisms involved are generally poorly understood. Here, we study the episodic effusion during 2021 Geldingadalir eruption. We use photogrammetric data and videos acquired by drones hovering over the active lava lake on 8 June 2021, and compare them with volcanic tremor recorded by a seismometer at 1.8 km distance from the vent. This allows us to investigate the timing of tremor, eruption, and the rise and falls of the lava lake. We observe an episodic seismic tremor lasting about 5 min, followed by over 7-min-long repose times. A closer study of one effusion episode reveals that within these 12 min the lava lake rises and falls by 24.6 <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>±</mo>\u0000 </mrow>\u0000 <annotation> $pm $</annotation>\u0000 </semantics></math> 0.6 m. The rise time is about 10 min, while the lake level drops within 2 min, contrasting with the tremor observations. By combining tremor and video analysis, we show that the tremor amplitude is not related to the lake level, but peaks when the bubble bursting and spattering in the lava lake is at its maximum. We therefore suggest that the tremor is closely related to the bubble bursting activity and is thus indicative of near-surface processes during an eruption. This study provides insights into tremor generation associated with the Geldingadalir eruption, leading to a conceptual model to assess its implications for the characterization and interpretation of dynamic lava lake evolution.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012084","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144811339","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":"Properties and Dispersal of a Hydrothermal Plume in a Weakly Stratified Under-Ice Environment","authors":"Maren Walter,&nbsp;Andreas Türke,&nbsp;Alexander Diehl,&nbsp;Christopher R. German,&nbsp;Christian Mertens,&nbsp;Jonathan Mette,&nbsp;Patrick Monien,&nbsp;Simon Prause,&nbsp;Jürgen Sültenfuß,&nbsp;Wolfgang Bach,&nbsp;Vera Schlindwein,&nbsp;Antje Boetius","doi":"10.1029/2024GC012016","DOIUrl":"10.1029/2024GC012016","url":null,"abstract":"<p>The Aurora vent field (82°53.83′N, 6°15.32′W) is located in the weakly stratified Arctic Ocean under perennial ice cover at the western edge of the ultraslow-spreading Gakkel Ridge, the slowest spreading mid-ocean ridge on Earth. Here, we report data on the dispersal of the proximal hydrothermal plume in this extreme environment. The hydrothermal plume is of unusual dimensions, with a small horizontal, but large vertical extent, which is caused by the hydrography of the Arctic Ocean. Water column parameters such as turbidity and redox potential show a highly variable but horizontally confined non-buoyant plume. Dissolved iron (dFe), manganese (dMn), δ³He, and methane (CH₄) all show distinct enrichment in the hydrothermal plume relative to background deep-water, but relatively low peak concentrations due to the dilution over a vertical extent of over 500 m. Plume particle samples exhibit elevated Fe/Al ratios consistent with Fe-oxyhydroxide precipitation close to the vent, whereas particulate Mn/Al ratios do not reveal any complementary pMn enrichment in the proximal plume. The positive correlation between Fe/Al, and several other element/Al ratios (e.g., P, V, As) is consistent with scavenging of these elements onto Fe-hydroxide plume particles and removal into the underlying sediments. Surface sediment samples collected close to Aurora reveal highly elevated concentrations of hydrothermally sourced elements in the immediate vicinity of the vent-site. For example, proximal surface sediments contained up to 8,222 mg kg⁻¹ Cu, whereas Cu concentrations in core tops a few kilometers away from the site were much lower (&lt;50 mg kg⁻¹).</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012016","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144811338","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":"Sound Velocities of Basaltic Glass at Earth's Deep-Mantle Pressures","authors":"Xiaowan Su,&nbsp;Jin Liu,&nbsp;Yongsheng Zhou,&nbsp;Jun Hu,&nbsp;Mathieu Roskosz,&nbsp;Jung-Fu Lin","doi":"10.1029/2025GC012272","DOIUrl":"10.1029/2025GC012272","url":null,"abstract":"<p>The elasticity of compressed silicate melts is essential to decipher seismic properties and dynamic evolution of deep mantle magmas. Here, we report the compressional (<i>V</i>_P) and shear (<i>V</i>_S) wave velocities of a basaltic glass (Na_0.036Ca_0.220Mg_0.493Fe_0.115Al_0.307Ti_0.012K_0.002Si_0.834O₃) up to 63 GPa at 300 K using Brillouin and impulsive stimulated light scattering spectroscopies coupled with diamond anvil cells. The <i>V</i>_P and <i>V</i>_S data from 2.4 to 62.8 GPa exhibit convex upward trend, but the pressure-dependent velocity slopes become flatter at around 38 ± 3 GPa. The <i>V</i>_P and <i>V</i>_S values increase from 6.86 ± 0.03 to 11.62 ± 0.20 km/s and from 3.70 ± 0.03 to 5.28 ± 0.07 km/s, respectively. These velocity behaviors are likely associated with the 4- to 6-fold silicon coordination number increase. Comparison with literature data on MgSiO₃ glass, silicate, and pyrolitic glasses at high pressure suggests that the addition of Al₂O₃ can enhance the <i>V</i>_S and <i>V</i>_P of the basaltic glass, whereas FeO and CaO substitutions decrease its velocities. Using our results as an analog for basaltic melts, which can incorporate significant amounts of Al₂O₃ and FeO, the countercationic effects of Al₂O₃ and FeO on velocities and density of the basaltic melt could make it less visible seismically at the mid-lower mantle depths of ∼1,500 km.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012272","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145135332","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":"Comparing Geochemical and Geodynamical Models of Plume and Ridge Mantle Source Composition","authors":"Paul Béguelin,&nbsp;James Panton,&nbsp;Morten Andersen,&nbsp;Tim Elliott,&nbsp;Huw Davies,&nbsp;Joel Rodney,&nbsp;Abigail Plimmer","doi":"10.1029/2025GC012357","DOIUrl":"10.1029/2025GC012357","url":null,"abstract":"<p>We use a multidisciplinary approach to investigate how the parameter space of mantle convection affects present-day mantle composition. We compare 22 forward geodynamical mantle circulation model simulations against 24 variants of a geochemical inversion model of the global radiogenic isotope data set of mantle-derived lavas. Both models are fully independent but able to output compositional parameters for the lower mantle sampled by upwelling mantle plumes and for the upper mantle sampled by mid-oceanic ridges. Geodynamical model results suggest an excess degree of peridotite melt-depletion Δ<i>F</i>_<i>d</i> = +0.4% ± 0.4% and an excess amount of recycled crust Δ<i>f</i>_RC = +2.7% ± 3.1% in plumes compared to ridges, while the geochemical inversion returns Δ<i>F</i>_<i>d</i> = +0.4% ± 1.2% and Δ<i>f</i>_RC = +1.5% ± 0.6%. Models are thus in quantitative agreement but with opposite sensitivities, allowing to restrict their respective parameter space. Geodynamical runs show best fits with the narrow geochemical Δ<i>f</i>_RC for core-mantle boundary (CMB) temperatures of 3,400–3,800 K and a recycled crust buoyancy number of 0.44–0.66. A dense primordial layer at the CMB also leads to a better fit. Variants of our geochemical model show a best fit with the narrow geodynamical Δ<i>F</i>_<i>d</i> value when early mantle differentiation occurs in the garnet stability field. We also find that the formation of early compositional heterogeneities is needed to fully explain the isotope range of mantle melts. Our work emphasizes the need to correct isotopic data for the effects of non-magmatic processes in a quantitative geochemical model before extracting the parameters relevant to a comparison with geodynamical model results.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012357","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144773775","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":"Lithospheric Seismic Structure of the Anatolian Plate and Its Implications for Plateau Uplift: Evidence From Joint Inversion of Receiver Functions and Surface Waves","authors":"Pengzhe Zhou,&nbsp;Ian D. Bastow,&nbsp;Rita Kounoudis,&nbsp;Christopher S. Ogden,&nbsp;Yanghua Wang","doi":"10.1029/2025GC012393","DOIUrl":"10.1029/2025GC012393","url":null,"abstract":"<p>High topography (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>&gt;</mo>\u0000 </mrow>\u0000 <annotation> ${ &gt;} $</annotation>\u0000 </semantics></math>1 km) on the Anatolian Plate is widely attributed to buoyant mantle support, not just the isostatic response of crustal shortening. However, uncertainties in lithospheric structure hinder attempts to discriminate between competing uplift mechanisms. We jointly inverted receiver functions with Rayleigh wave group-velocity dispersion curves to obtain 1D shear velocity profiles for 575 seismograph stations across Anatolia. Crustal thickness increases from <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>25 km in the west to <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>≤</mo>\u0000 </mrow>\u0000 <annotation> ${le} $</annotation>\u0000 </semantics></math>44 km below Eastern Anatolia, with short length-scale Moho topography in places. Within the Central Anatolian Plateau (CAP), thicker crust, lower residual topography, higher residual Bouguer gravity anomalies, and faster upper-mantle wavespeeds north of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 <mn>39</mn>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> ${sim} 39{}^{circ}$</annotation>\u0000 </semantics></math>N than to the south suggest that northern CAP lithospheric removal is less-developed. Processes like slab break-off, lithospheric delamination and/or dripping are therefore more likely to contribute to the uplift in the south, with additional support from buoyant mantle flow through the Cyprus slab tear. A <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>5 km Moho step across the Eastern Anatolian Fault (EAF) results partly from dominant crustal shortening on the Anatolian Plate. Further east, no Moho depth contrast exists across the Bitlis suture; Arabia-Eurasia crustal shortening has thus been accommodated by both plates. An ENE–WSW-trending band of positive residual topography and negative residual Bouguer anomalies parallels the EAF below the northwestern tip of Arabia. This connects to a zone of peak residual topography and slow uppermost mantle wavespeeds below the magmatically active Eastern Anatolian Plateau. These observations are explained best by NE-flowing, buoyant mantle plume material from the Afar hotspot to the south.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012393","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144758578","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":"Temporal Evolution of Seismicity in the Central Southern Alps, New Zealand: Evidence for Rainfall-Triggered Seismicity","authors":"Konstantinos Michailos,&nbsp;Calum J. Chamberlain,&nbsp;Guy Simpson,&nbsp;Simon C. Cox,&nbsp;John Townend,&nbsp;Lauren J. Vargo,&nbsp;Nicolas Oestreicher,&nbsp;Meghan S. Miller","doi":"10.1029/2025GC012317","DOIUrl":"10.1029/2025GC012317","url":null,"abstract":"<p>Understanding the conditions and mechanisms that produce earthquakes is of high scientific relevance. The central Southern Alps/Kā Tiritiri o te Moana of New Zealand is an active orogen that offers a unique opportunity to study the processes that drive seismogenesis. A new high-quality, matched-filter-based microseismicity catalog has been constructed by following a fully automated detection and location process. The catalog spans from 2009 to 2020 with local magnitudes between <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>M</mi>\u0000 <mi>L</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${M}_{L}$</annotation>\u0000 </semantics></math> −1.81 and 3.42. Our results indicate a seasonal pattern in earthquake occurrence, with a notable correlation between shallow-depth earthquakes (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>6 km hypocentral depths) and large, mostly summer, rainfall events beneath three separate glaciers. We hypothesize that a combination of seasonal snowmelt and heavy rainfall events raises the water table during spring and summer, changing pore-fluid pressure in the upper crust and triggering earthquakes. Our findings highlight the role of extreme rainfall and glacier dynamics in triggering shallow earthquakes, which can improve hazard assessment in the central Southern Alps/Kā Tiritiri o te Moana and similar alpine regions worldwide.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012317","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144751629","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":"Ductile Crustal Flow Facilitates Intraplate Volcanism: Seismic Evidence From Tengchong, China","authors":"Xingpeng Dong,&nbsp;Kai Yang","doi":"10.1029/2025GC012432","DOIUrl":"10.1029/2025GC012432","url":null,"abstract":"<p>The mechanisms and processes driving intraplate volcanism remain incompletely understood despite significant advances in recent decades. Here, we use high-resolution multiparameter full-waveform inversion to image the three-dimensional seismic structure beneath the Tengchong volcanic region in southwestern China. Our model reveals a pronounced low-velocity anomaly and elevated Poisson's ratio in the uppermost mantle, consistent with a deep-seated magma reservoir. Significantly, we resolve a laterally extensive mid-to-lower crustal channel characterized by low velocity, high Poisson's ratio, and positive radial anisotropy (<i>V</i>_SH &gt; <i>V</i>_SV) extending from the southeastern Tibetan Plateau toward Tengchong. This feature is interpreted as ductile crustal flow, which ascends beneath Tengchong and interacts with the overlying crustal magma system. Our findings provide the first seismic evidence that deep crustal flow can dynamically couple with mantle-derived magmatism to facilitate intraplate volcanism. These results offer new insights into crust-mantle interactions and the generation of volcanism in continental interiors.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012432","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144751625","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":"Duration and Geochemical Evolution of Triassic and Jurassic Magmatism Along the Eastern North American Margin","authors":"Zachary S. Foster-Baril,&nbsp;Emily R. Hinshaw,&nbsp;Daniel F. Stockli,&nbsp;Christopher M. Bailey,&nbsp;Jacob Setera","doi":"10.1029/2024GC011900","DOIUrl":"10.1029/2024GC011900","url":null,"abstract":"<p>Our understanding of the impact of melt generation and the interplay between magmatism and mechanical stretching during progressive rifting leading to seafloor spreading remains rudimentary. The Eastern North American Margin (ENAM) provides an excellent location to study the influence of rift magmatism on continental break-up considering the preservation of ∼30 Myr of syn-rift strata and voluminous basaltic dikes, sills, and flows. Previous studies mainly focused on magmatism preserved in ENAM rift basins, emphasizing Central Atlantic Magmatic Province activity. Aeromagnetic data sets show pervasive magmatism across the ENAM proximal domain in the form of dikes that largely remain undated. We present in situ apatite U-Pb geochronology and whole-rock geochemical data from diabase dikes along the ENAM to determine the temporal and chemical evolution of Mesozoic dike emplacement and evaluate whether these magmas were emplaced rapidly at ∼201 Ma or in episodic pulses during rifting and break-up. New in situ apatite U-Pb analyses collectively indicate multiple magmatism pulses along the proximal domain of the ENAM, clustering around ∼201, ∼180, and ∼150 Ma. A first pulse at the Triassic/Jurassic boundary is likely due to decompression melting of an enriched mantle, a second smaller pulse in the Early Jurassic potentially correlative to the Blake Spur Magnetic Anomaly and lithospheric breakup, and a third small pulse in the Early Jurassic potentially correlative to the transition to symmetric seafloor spreading. These results indicate that prolonged off-axis magmatism is likely due to slow spreading rates driving delocalization of extension away from the rift axis into the proximal domain.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011900","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144725682","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 Control of End-Member Iron-to-Sulfide Ratios on Hydrothermal Plume Geochemistry at the Rainbow, Broken Spur, and Lost City Vent Fields in the Mid-Atlantic Ridge","authors":"Serhat Sevgen,&nbsp;Nadine Le Bris,&nbsp;Mustafa Yücel","doi":"10.1029/2025GC012370","DOIUrl":"10.1029/2025GC012370","url":null,"abstract":"<p>The Mid-Atlantic Ridge (MAR) represents a unique tectonic environment hosting distinct hydrothermal vent fields. Considering the growing interest in understanding the role of hydrothermal vents in both local and global ocean systems, the MAR offers an opportunity to investigate hydrothermal geochemistry within a single basin. Here, we present findings from three representative vent settings along the MAR: Broken Spur, Rainbow, and Lost City, as explored during a research expedition aboard the R/V L’Atalante in 2018. We conducted high temperature hydrothermal fluid sampling with ROV Victor 6000 to assess the concentrations of major ions, ∑H₂S, Fe, and Mn in each vent field. Notably, our results highlight that Rainbow and Lost City vent fluids exhibit minimal spatial and temporal variations over a 20-year timeframe while Broken Spur fluids displayed significant variation since their last sampling 25 years ago, specifically losing ∼60% of their dissolved Fe concentration. We further analyzed hydrothermal plume composition evolution using geochemical models and suggested that the Fe:∑H₂S ratio plays a key role in controlling the minerals precipitated during hydrothermal fluid-seawater mixing. In the Broken Spur hydrothermal plume, a low Fe:∑H₂S ratio favors the early dominance of metal sulfides, whereas in the Rainbow hydrothermal plume, a high Fe:∑H₂S ratio might promote the formation of Fe-oxide and Fe-silicate phases alongside metal sulfides. These findings provide a framework for tracing hydrothermal fluid evolution along the subseafloor-plume interface. They also highlight the potential impact of hydrothermal vents on the near-field transport of micronutrient metals in the deep ocean.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 7","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012370","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144714841","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}