Geochemistry Geophysics Geosystems最新文献

{"title":"Spatiotemporal Evolution of Volcanism in the Black Rock Desert Volcanic Field, Utah, and Its Migration Relative to the Colorado Plateau","authors":"Brian R. Jicha,&nbsp;Tiffany A. Rivera,&nbsp;Eva M. Golos","doi":"10.1029/2025GC012520","DOIUrl":"https://doi.org/10.1029/2025GC012520","url":null,"abstract":"<p>In the southwest USA, the Colorado Plateau is encircled by Late Cenozoic volcanic fields, most of which have eruptive histories that are marginally constrained. Establishing the spatiotemporal evolution of these volcanic fields is key for quantifying volcanic hazards and understanding magma genesis. The Black Rock Desert (BRD) volcanic field covers ∼700 km² of west-central Utah. We present 46 new ⁴⁰Ar/³⁹Ar ages from the BRD ranging from 3.7 Ma to 8 ka, which includes ⁴⁰Ar/³⁹Ar plateau ages from olivine separates. These new ages are combined with 13 recently published ⁴⁰Ar/³⁹Ar ages from the Mineral Mountains to evaluate the spatiotemporal evolution of all five BRD subfields. The oldest lavas and domes are located to the southwest, whereas the youngest lavas, which are only a few hundred years old, are located ∼30 km to the NNE. However, BRD vent migration patterns over the last 2.5 Ma are non-uniform. They are also not consistent with North American Plate motion over a partial melt zone nor have they migrated toward the center of the Colorado Plateau. BRD eruptions are almost always coincident with mapped Quaternary faults. A shear-velocity (Vs) model beneath the BRD indicates that the lithosphere has been thinned and that asthenospheric melt has coalesced at the lithosphere-asthenosphere boundary, which is supported by the trace element compositions of BRD lavas that signify that they have incorporated continental lithospheric mantle. Our data and observations suggest that the asthenosphere-lithosphere-volcanic system in the BRD is inherently complex.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 10","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012520","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145146777","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":"Authigenic Uranium Preservation and Bottom Water Oxygenation in the Scotia Sea","authors":"Moritz Hallmaier,&nbsp;Marcus Gutjahr,&nbsp;Jörg Lippold,&nbsp;Sidney R. Hemming,&nbsp;Lukas Gerber,&nbsp;Michael E. Weber,&nbsp;Anton Eisenhauer","doi":"10.1029/2025GC012415","DOIUrl":"https://doi.org/10.1029/2025GC012415","url":null,"abstract":"<p>Sedimentary uranium (U) and thorium (Th) isotopes are invaluable proxies to assess bottom water redox conditions, site-specific sediment focusing and vertical rain rates. We investigate if authigenic uranium (aU) can serve as a proxy for bottom water ventilation at International Ocean Discovery Program Site U1537 in the Scotia Sea and we provide Th-normalized vertical rain rates and focusing factors. The presented data set is complemented by bulk sediment δ²³⁴U, porewater U concentrations and biogenic barium. Furthermore, we introduce a method to check temporal variations in the detrital factor for the calculation of aU by comparing measured and modeled δ²³⁴U. We observed partial uranium remobilization in the core for sections older than 70 ka, identified by δ²³⁴U anomalies and porewater U concentrations. During interglacials, the accumulation of aU in the sediment is regulated by the decomposition of substantial quantities of organic matter, ultimately controlled by high export productivity and associated high particulate organic carbon fluxes. Conversely, during glacial times, low export productivity coincides with low aU concentrations, suggesting well-oxygenated bottom waters. However, during the Last Glacial Maximum, a rise in aU likely indicates reduced ventilation, suggesting an absence of Weddell Sea Deep Water and/or enhanced water column stratification between 23 and 17.5 ka.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012415","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145146414","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":"Fecal Biomarkers in Soils Record Landscape-Scale Wild Herbivore Abundance","authors":"A. Tyler Karp,&nbsp;James M. Russell,&nbsp;Joel O. Abraham,&nbsp;Tercia Strydom,&nbsp;A. Carla Staver","doi":"10.1029/2025GC012285","DOIUrl":"https://doi.org/10.1029/2025GC012285","url":null,"abstract":"<p>In Earth history, our understanding of how large-bodied herbivores shape a variety of ecosystem processes is limited by the quality of paleoecological proxies for herbivore composition and abundance. Fecal stanols are lipids that can be produced by microbes within animal digestive systems and that could remedy this dearth of proxies. We used two multi-decadal herbivore exclosures in Kruger National Park, South Africa, to constrain whether and how biomarker signatures preserve signals of herbivore abundance. Soil samples and dung counts were collected along transects across crests, mid-slopes, and sodic sites inside and outside exclosures. Soils were analyzed for steroid (sterols and stanols) concentrations and distributions. We found that stanol concentrations were significantly greater in sodic soils outside exclosures, where herbivore dung densities were greatest. In contrast, sterol concentrations did not differ between treatments. Ratios of stanol isomers to sterols, which account for both compound degradation and source, increased strongly with herbivore dung counts. Finally, while herbivore species compositions influenced steroid distributions, total herbivore abundance was their strongest predictor. Further calibration is needed, but this work provides strong preliminary evidence that wild herbivore populations are quantitatively recorded by fecal biomarker distributions.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012285","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145146544","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":"Contrasting Seismic Velocity and Compaction of Marine Calcareous Oozes and Volcaniclastic Deposits on the South Aegean Volcanic Arc","authors":"M. Manga,&nbsp;V. Wright,&nbsp;T. Cadena,&nbsp;I. McIntosh,&nbsp;J. Preine,&nbsp;M. Tominaga,&nbsp;P. Nomikou,&nbsp;T. Druitt,&nbsp;S. Kutterolf,&nbsp;S. Beethe,&nbsp;T. A. Ronge,&nbsp;C. Hübscher,&nbsp;J. Karstens,&nbsp;G. Kletetschka,&nbsp;Y. Yamamoto,&nbsp;A. Woodhouse,&nbsp;R. Gertisser,&nbsp;A. Peccia,&nbsp;A. Clark,&nbsp;IODP Expedition 398 Participants","doi":"10.1029/2025GC012327","DOIUrl":"10.1029/2025GC012327","url":null,"abstract":"<p>International Ocean Discovery Program Expedition 398 recovered more than 2,200 m of volcaniclastic deposits from 12 sites and 28 holes from Santorini Caldera, Greece, and the surrounding rift basins in the South Aegean Volcanic Arc. We compare and contrast discrete shipboard measurements of physical properties (density, P-wave velocity) of these volcaniclastic sediments with other uncemented marine sediments in the cores. The grain density (mass of solids divided by their volume, including any isolated vesicles) of volcaniclastic deposits is typically lower than that of volcanic glass and crystals and is sometimes less than 2 g/<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mrow>\u0000 <mi>c</mi>\u0000 <mi>m</mi>\u0000 </mrow>\u0000 <mn>3</mn>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${mathrm{c}mathrm{m}}^{3}$</annotation>\u0000 </semantics></math>, indicating the preservation of isolated gas-filled vesicles in erupted materials. Volcaniclastic deposits typically have higher P-wave velocities but lower bulk densities than oozes and other marine sediments. In volcaniclastic deposits, lapilli have higher P-wave velocities and lower bulk density than ash, the opposite trend of most sediment in which higher density is correlated with higher seismic velocity. We use granular physics models to show that the higher volcaniclastic P-wave velocity originates from two effects: (a) lower pore volume outside clasts that increases elastic moduli and (b) isolated gas vesicles in volcanic clasts that lower bulk density. In volcaniclastic sediments there is relatively little change in physical properties to depths of several hundred meters below the seafloor, which we attribute to rough grain surfaces and lower intergranular (external) porosities that hinder compaction and the decrease of intergranular pore space. These trends lead to distinctive signatures of volcaniclastic sediments in reflection seismic images.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012327","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145135570","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":"CH4-He-H2-Rich Fluids Associated With the Intrusive Rocks of the Mid-Continent Rift System in Minnesota (USA)","authors":"V. Combaudon,&nbsp;O. Sissmann,&nbsp;J. Guélard,&nbsp;S. Noirez,&nbsp;H. Derluyn,&nbsp;E. Deville","doi":"10.1029/2025GC012236","DOIUrl":"https://doi.org/10.1029/2025GC012236","url":null,"abstract":"<p>Several studies have shown that H₂ and CH₄ emissions are recorded within Precambrian areas, where the origin of gases has yet to be determined. The Mid-Continent Rift (MCR) is an aborted rift aged from 1.1 Ga and composed of volcanic and (ultra)-mafic rocks. Wells presenting free or dissolved gas were sampled in NE-Minnesota along the MCR. High pH water (up to 11.4) and low Eh (down to −300 mV) with elevated concentrations (up to 756 µmolar) of formate and acetate are associated with gases consisting of He, CH₄, CO_2, heavier hydrocarbons, and up to 500 ppmv of H₂. The CH₄ presents different ¹³C and D isotopic values, suggesting that several abiotic and biotic pathways might be active in these shallow systems. The alkaline and reducing waters associated with the igneous rocks of the MCR suggest that H₂ could have been produced through water-rock interactions at deeper levels not reached by the shallow sampled wells. The associated high concentrations of gaseous and dissolved carbon compounds (VOA and methane) suggest that subsequent redox reactions have occurred in most of the rocks crossed by the wells, consuming a part of the H₂ as it was migrating toward the surface. Those results highlight potentially active H₂ production and consumption processes, providing keys for targeting source rocks in Precambrian environments. Those results suggest that direct H₂ detection in soil gas may not be the most effective exploration strategy. Searching for biogenic methane associated with deep He and N₂ may prove to be more effective.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012236","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145146337","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":"A General Model for the Permeability of Magma Mush","authors":"Eloïse Bretagne,&nbsp;Fabian B. Wadsworth,&nbsp;Jérémie Vasseur,&nbsp;Katherine E. Schofield,&nbsp;Madeleine C. S. Humphreys,&nbsp;Katherine J. Dobson","doi":"10.1029/2025GC012461","DOIUrl":"https://doi.org/10.1029/2025GC012461","url":null,"abstract":"<p>Percolation through magma mush is a key transport mechanism for melts in the crust and is influenced by the permeability of the crystal framework. Existing models for mush permeability do not account for the range of microstructures that can evolve as mushes crystallize or compact to low melt fractions. Here, we use numerically generated domains of cuboids at the random maximum packing as a starting geometry for a loose magma mush. We then expand the cuboid edges into the pore spaces sequentially, representing a geometrical simulation of crystal overgrowth and crystallization. At each iterative step, we measure the melt fraction, specific surface area, and melt permeability via 3D fluid flow simulations. We find that (a) the permeability drops proportional to the drop in surface area as the melt fraction reduces, (b) the permeability falls to zero at a percolation threshold <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>ϕ</mi>\u0000 <mi>c</mi>\u0000 </msub>\u0000 <mo>=</mo>\u0000 <mn>0.0187</mn>\u0000 <mo>±</mo>\u0000 <mn>0.0010</mn>\u0000 </mrow>\u0000 <annotation> ${phi }_{c}=0.0187mathit{pm }0.0010$</annotation>\u0000 </semantics></math> that is independent of scale and insensitive to the starting cuboid geometry, and (c) once the percolation threshold is determined, our data match a universal percolation model without requiring any free fitting parameters. We show how this percolation model accounts for any 3D shape of the crystals that comprise the evolving mush. Importantly, this approach demonstrates that mush permeability can remain non-zero in texturally unequilibrated mushes, down to very low melt fractions. Our model outperforms previous models, which overestimate mush permeability by up to three orders of magnitude, and our model can be used to accurately predict how mush permeability changes as mushes mature and crystallize, with implications for quantifying melt extraction, percolation rates, and melt reservoir assembly.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012461","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145146299","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":"Reactive Melt Flow in the Continental Arc Root: Insights for the Transition From Gabbronorite to Garnet Granulite in the Central Qilian Belt, NE Tibet","authors":"Xiao-Kui Sun,&nbsp;Chao Wang,&nbsp;Nathan R. Daczko,&nbsp;Xiao-Ying Liao,&nbsp;Ji-Heng Zhang,&nbsp;Wen-Qiang Yang,&nbsp;Liang Liu","doi":"10.1029/2025GC012366","DOIUrl":"https://doi.org/10.1029/2025GC012366","url":null,"abstract":"<p>Understanding reactive melt flow is crucial for advancing our knowledge of crustal differentiation; however, the mechanisms governing melt migration remain debated, particularly in deep magmatic arc environments. A composite sample from the Central Qilian continental arc, NE Tibet, preserves the transition from hornblende gabbronorite to garnet granulite, offering a rare opportunity to study reactive melt flow in the arc root. Thermodynamic modeling showed that the hornblende gabbronorite was metastable under lower-crustal conditions (6.2–8.2 kbar, 900–931°C). To equilibrate with the normal thermal regime of the middle to lower crust, it underwent near-isobaric cooling to 816 ± 16°C, whereas its transformation into garnet granulite occurred under higher pressure and temperature conditions (10.2–12.2 kbar, 833–865°C). The sample records melt-rock interactions during the transition from the magmatic stage to garnet granulite facies metamorphism. Reactive melts infiltrated grain boundaries, inducing mineral replacement via dissolution-precipitation and metasomatism. Enriched rare earth elements (REEs) in blue-green pargasite, reaction microstructures and hydrous products attest to melt-rock interactions involving Mg-Sr-REE-enriched silicate melts. Trace element mapping reveals a correlation between reaction microstructures and high-Sr plagioclase bands, highlighting grain boundary pathways for melt migration. Replacement microstructures illustrate permeable reactive melt flow pathways within the lower arc crust. Reactive melt flow enhanced chemical disequilibrium and mineralogical reorganization, driving textural maturation through coupled dissolution-reprecipitation. This pervasive melt-rock interaction mechanism likely governs both crustal differentiation and the development of high Sr arc magmatic signatures.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012366","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145146336","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":"Understanding Sub-Lithospheric Small-Scale Convection by Linking Models of Grain Size Evolution, Mantle Convection, and Seismic Tomography","authors":"Juliane Dannberg,&nbsp;Zachary Eilon,&nbsp;Joshua B. Russell,&nbsp;Rene Gassmöller","doi":"10.1029/2025GC012289","DOIUrl":"https://doi.org/10.1029/2025GC012289","url":null,"abstract":"<p>The interaction between aging oceanic plates and their underlying mantle is a crucial component of the plate tectonic cycle. Sub-lithospheric small-scale convection (SSC) explains why plates appear not to thicken after a certain age. Here, we link grain-scale processes, dynamic models of asthenospheric flow, and seismic observations to gain new insights into the mechanisms of SSC. We present high-resolution 3D geodynamic models of oceanic plate evolution with an Earth-like rheology including coupled diffusion/dislocation creep and their interplay with evolving olivine grain size. Our models quantify how rheology affects the morphology and temporal stability of SSC, and we directly relate these quantities to geophysical observations from the Pacific OBS Research into Convecting Asthenosphere (ORCA) experiment. We convert variations in temperature, pressure, grain size, water content and stable melt fraction to seismic velocity and attenuation, seeking to match the wavelength and pattern of observed longitudinal convective rolls, the young SSC onset age, the large seismic velocity heterogeneity, low absolute seismic velocities, and high seismic attenuation. This requires low (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>&lt;</mo>\u0000 <mn>2</mn>\u0000 <mo>×</mo>\u0000 <mn>1</mn>\u0000 <msup>\u0000 <mn>0</mn>\u0000 <mn>19</mn>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${&lt; } 2times 1{0}^{19}$</annotation>\u0000 </semantics></math> Pa s) asthenospheric viscosity, the contribution of both diffusion and dislocation creep to deformation, and the presence of volatiles and melt. Although SSC occurs at plate ages <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>≪</mo>\u0000 </mrow>\u0000 <annotation> $ll $</annotation>\u0000 </semantics></math>60 Ma in our best-fit model, the plate thermal structure approximately matches global observations of heat flux and bathymetry, indicating an important role of vigorous SSC in Earth's plate dynamics. However, reconciling all seismological observations is challenging, and additional mechanisms are required to explain the strong velocity heterogeneities suggested by body wave tomography.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012289","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145146298","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":"Abundant Ancient Melt-Depleted Peridotite Beneath the Marion Rise, Southwest Indian Ocean, Effects on Basalt Composition and Dynamic Topography","authors":"Dominic Woelki,&nbsp;Vincent Salters,&nbsp;Andreas Stracke,&nbsp;Felix Genske,&nbsp;Gary White,&nbsp;Daniele Brunelli","doi":"10.1029/2025GC012418","DOIUrl":"10.1029/2025GC012418","url":null,"abstract":"<p>The Marion Rise (MR) at the central Southwest Indian Ridge (SWIR) is an ultra-slow spreading ridge with thin crust, shallow ridge depth, sparse basaltic coverage, and exposed peridotite. Clinopyroxenes from the MR peridotites have highly variable Hf-Nd isotopic composition extending to extreme ε_Nd of 94 and ε_Hf of 417, which requires extensive melting and evolution with high Lu/Hf for more than 1 Ga. The Yb content of clinopyroxenes is negatively correlated with the Cr# (molar Cr/Cr + Al) of spinel, but not with ε_Hf, indicating a multi-stage evolution of depletion and melt-rock reaction. The highly variable Hf-Nd isotopic compositions of the MR basalts are not systematically correlated and range from ε_Nd −8 to 9.1 and ε_Hf −10 to 32. Therefore, the basalts are probably a mixture of melts from several lithologies, for example, a recycled crustal component with exceptionally low Hf-Nd isotope ratios, in addition to melts from the volumetrically predominant, isotopically highly variable peridotites. The ancient melt-depletion of the MR peridotites with high Hf isotope ratios also reduced their density. A peridotitic mantle melted to &lt;10% can support the Marion Rise without the need of increased mantle temperature. Ultra-depleted peridotites like those from the MR ones have been documented at multiple localities, indicating that they are ubiquitous in the sub-ridge mantle. Hence, melts from such ultra depleted peridotite influences mid-ocean ridge basalt (MORB) compositions and variably melt depleted sub-ridge peridotites should be considered when evaluating ridge depth variations.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012418","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145135507","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":"Temperature Variability on Coral Reefs Versus Gridded SST – The Long and the Short of It","authors":"A. M. Dolman,&nbsp;T. Laepple","doi":"10.1029/2025GC012351","DOIUrl":"10.1029/2025GC012351","url":null,"abstract":"<p>Coral-based temperature reconstructions and gridded sea-surface-temperature (gSST) data sets both provide valuable insights into tropical climate variability. However, coral records often exhibit greater interannual to decadal variability than is observed in gSST products or Earth System Models (ESMs). This discrepancy is often attributed to large differences in spatial scale: coral records reflect conditions over areas of only a few square centimeters, while gSST and ESM grid cells span 1 to 10,000 km². In situ temperature loggers on coral reefs allow us to isolate the effects of spatial scale from other non-climatic influences on coral temperature records. Many logger studies focus on hourly to monthly timescales, temperature biases, and whether gSST can capture temperature extremes associated with coral bleaching and mortality; however, paleoclimate reconstructions provide an understanding of variability on longer timescales. Here, we compare the power spectral density and coherence of logger temperature and gSST on daily to decadal timescales using logger data from 42 sites on the Great Barrier Reef. We find that temperature variations recorded by loggers on reefs are well correlated with and have the same amplitude as gSST variations at decadal to annual timescales. Therefore, the excess decadal variability commonly seen in coral-based temperature reconstructions cannot be attributed to a general effect of spatial scale.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012351","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145101914","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}