Earth and Planetary Science Letters最新文献

{"title":"Carbon, nitrogen, and noble gas isotopes reveal deep volatile signatures in thermal springs in the Central Volcanic Zone (CVZ) of the Andes","authors":"PH Barry ,&nbsp;JM de Moor ,&nbsp;MW Broadley ,&nbsp;AM Seltzer ,&nbsp;DV Bekaert ,&nbsp;K Patil ,&nbsp;CGE Bartels ,&nbsp;ED Young ,&nbsp;BE Longworth ,&nbsp;B Barosa ,&nbsp;A Bastianoni ,&nbsp;D Bastoni ,&nbsp;M Cascone ,&nbsp;SJ Turner ,&nbsp;RL Tyne ,&nbsp;M Anderson ,&nbsp;K Li ,&nbsp;J Curtice ,&nbsp;N Kumar ,&nbsp;GL Jessen ,&nbsp;D Giovannelli","doi":"10.1016/j.epsl.2024.119169","DOIUrl":"10.1016/j.epsl.2024.119169","url":null,"abstract":"<div><div>In subduction zones, thermal springs release deeply-sourced volatiles from Earth's mantle, crust, and/or subducted slab-derived material. The origin and apparent ages of these volatiles are important for understanding the deep volatile cycle, which in turn affects the distribution of microbial life in the subsurface. Here, we report carbon (¹³C, ¹⁴C), noble gas (He, Ne, Ar, Kr and Xe), and clumped nitrogen isotope data in gas and water samples from thermal springs within the Central Volcanic Zone (CVZ) of the Andean Convergent Margin (ACM). He isotopes show that CVZ gases are predominantly sourced from the crust (∼77 %), with smaller mantle contributions (∼23 %), consistent with previous studies from the CVZ. Thermal spring samples with non-atmospheric He-Ne characteristics have low ¹⁴C activities, and are deeply derived (i.e., from the mantle and crust) and old (&gt;22,000 years). To gain additional constraints on volatile sources, a gas sample from Pirquitas Argentina was analyzed using a new high-precision technique to reveal significant geogenic anomalies in argon (⁴⁰Ar/³⁶Ar = 492), fissiogenic xenon (88 % crustal), and helium (84 % crustal) isotopes. Clumped N₂ isotopologue results also indicate that the N₂-rich Pirquitas sample is dominated by crustal and magmatic N₂, which was unambiguously released at high temperatures (indicated by Δ₃₀ of ∼0‰). When taken together, all carbon, noble gas and clumped N₂ isotope data from CVZ thermal springs point toward a predominantly crustal source of volatile elements, which is consistent with the thick crust beneath the arc. We conclude that thermal springs with noble gas isotopic evidence for minimal air contributions are old, suggesting that any microbial communities entrained in them are also supported by deeply-derived and old organic carbon.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119169"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143157736","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"More than an age: U-Pb dating constrains alteration of Precambrian carbonates","authors":"Nathalie Neagu ,&nbsp;Andrew Kylander-Clark ,&nbsp;Woodward W. Fischer ,&nbsp;Uri Ryb","doi":"10.1016/j.epsl.2024.119154","DOIUrl":"10.1016/j.epsl.2024.119154","url":null,"abstract":"<div><div>The Campbellrand Platform (South Africa) is one of the best-preserved carbonate archives for studying Neoarchean marine environments immediately preceding the Great Oxygenation Event. These carbonates preserve depositional structure and textures, like a variety of dolomitized stromatolites and microbialites encased in herringbone calcite – a type of early marine calcite cement. The preservation of depositional textures in Precambrian carbonates is often used to argue for the retention of primary paleoenvironmental signals, which are, in turn, used to infer the conditions in ancient surface environments including the composition of seawater and climate. Here we tested this idea using laser-ablation ICP-MS U-Pb to independently date specific carbonate mineral fabrics from the ∼2.58 Ga Reivilo Formation and ∼2.52 Ga Gamohaan Formation at the Campbellrand platform in the Northern Cape Province of South Africa. U-Pb dates of dolomite fabrics are mostly younger than their expected stratigraphic age and their initial ²⁰⁷Pb/²⁰⁶Pb compositions follow the modeled terrestrial Pb-isotope evolution trend. These results suggested that dolomite fabrics have experienced open-system alteration in which diagenetic fluids carrying a terrestrial signature reset U-Pb dates and overprinted initial Pb-isotope compositions during deep diagenesis. In contrast, herringbone calcite fabrics yielded near-stratigraphic U-Pb dates that clustered around an average of 2403 (±93) Ma and initial ²⁰⁷Pb/²⁰⁶Pb values that plotted below the modeled terrestrial Pb-isotope evolution trend. These results revealed that Neoarchean herringbone calcite fabrics were minimally altered in a closed system with respect to Pb, at deposition or some 10-100 Ma later, and have remained closed with respect to both U and Pb since. The closed-system behavior of a highly sensitive system like U-Pb in herringbone calcites serves as an independent validation for the reliability of herringbone calcites as useful recorders of marine environments. U-Pb dating of ancient carbonates thus offers a complementary tool for petrographic analyses that can identify and evaluate the timing and nature of alteration (open or closed system) of primary geochemical signatures in Precambrian carbonates.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119154"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A significant doubling of rockfall rates since the Little Ice Age in the Mont-Blanc massif, inferred from 10Be concentrations and rockfall inventories","authors":"Léa Courtial-Manent ,&nbsp;Jean-Louis Mugnier ,&nbsp;Ludovic Ravanel ,&nbsp;Julien Carcaillet ,&nbsp;Philip Deline ,&nbsp;Jean-François Buoncristiani","doi":"10.1016/j.epsl.2024.119142","DOIUrl":"10.1016/j.epsl.2024.119142","url":null,"abstract":"<div><div>By combining cosmogenic nuclide data and rockfall inventories, we have employed a rigorous methodology to focus on long-term erosion trends and the increase in rockfall in the Mont-Blanc massif (European Alps) over the last century. To do this, we used mathematical formulations based on power law integration, which enabled us to identify the complex links between rockfall distribution and erosion rates. Our approach was applied to the Mer de Glace basin (Mont-Blanc massif), where we combined analyses of ¹⁰Be concentration in the supraglacial load (based on 8 samples) with Terrestrial Laser Scanning (TLS) data capturing 123 rockfalls ranging from 1 to 566 m³, as well as direct observations of 71 rockfalls ranging from 100 to 20,000 m³. Within the overlapping volume range of both inventories, power law fitting yields a common exponent (<em>b</em>-value) of 0.75 ± 0.18. However, the TLS-derived rockfall rate (ā in m^-2.yr^-1) is approximately 5 times higher than that derived from the observation-based inventory. This difference is probably linked to the current intense permafrost degradation affecting scanned rockwalls at altitudes below 3800 m a.s.l. The 20,000 m³ rockfall documented by the network of observers has a statistical return time estimated at &lt;6 years, which suggests that larger or more significant rockfalls will occur in the future. Based on a two-segment power law, the erosion rate is estimated at &gt; 4.1 mm.yr^-1 for the period 2006–2011.</div><div>According to our study of glacial dynamics, the supraglacial clasts sampled aggregate ̴800 rockfalls greater than 1 m³ that occurred diachronically between 1845 and 1987 but whose cumulative total corresponds to &lt;7 years of present rockwall erosion rate in the upper Mer de Glace basin. The mean ¹⁰Be concentration of the 8 supraglacial samples is 2.7 ± 1.3 10⁴ at.g^-1 and was obtained when exposing rock faces subjected to erosion of &lt;1.2 ± 1 mm.yr^-1. The erosion rate would, therefore, have significantly increased between the Little Ice Age (maximum 2.2 mm.yr^-1 from ¹⁰Be result) and the beginning of the 21st century (minimum 4.1 mm.yr^-1 for 2003–2011 surveys). These erosion rates do not consider past volume rockfalls greater than those observed recently and are minimal erosion rate estimates. Nevertheless, they highlight the increase in mass movement hazards linked to global warming <em>via</em> permafrost degradation in high-altitude rockwalls.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119142"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158145","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Nanoscale reservoirs store solar wind-derived water on the lunar surface","authors":"Alexander M. Kling ,&nbsp;Jennika Greer ,&nbsp;Michelle S. Thompson ,&nbsp;Philipp R. Heck ,&nbsp;Dieter Isheim ,&nbsp;David N. Seidman","doi":"10.1016/j.epsl.2024.119178","DOIUrl":"10.1016/j.epsl.2024.119178","url":null,"abstract":"<div><div>Observations of widespread hydration across the lunar surface could be attributed to water formed via the implantation of solar wind hydrogen ions into minerals at the surface. Solar wind irradiation produces a defect-rich outer rim in lunar regolith grains which can trap implanted hydrogen to form and store water. However, the ability of hydrogen and water to be retained in space weathered regolith at the lunar surface is not well-understood. Here, we present results of novel and coordinated high-resolution analyses using transmission electron microscopy and atom probe tomography to measure hydrogen and water within space weathered lunar grains. We find that hydrogen and water are present in the solar wind-damaged rims of lunar grains and that these species are stored in higher concentrations in the vesicles that are formed by solar wind irradiation. These vesicles may serve as reservoirs that store water over diurnal and possibly geologic timescales. Solar wind-derived water trapped in space weathered rims is likely a major contributor to observations of the widespread presence, variability, and behavior of the water across the lunar surface.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119178"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143157739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Fault scarps and tectonic strain in young volcanic seafloor","authors":"Jie Chen ,&nbsp;Javier Escartin ,&nbsp;Mathilde Cannat","doi":"10.1016/j.epsl.2024.119174","DOIUrl":"10.1016/j.epsl.2024.119174","url":null,"abstract":"<div><div>Fault scarps at Mid-Ocean Ridges (MOR) are recognizable on the seafloor, and often measured to estimate the tectonic component of plate divergence. This estimate, based on linear fault scarp parameters, is referred to here as apparent tectonic strain (ATS). However, ATS may differ from the actual tectonic strain at a lithosphere scale. This is clear at detachment faults at magma-poor slow-ultraslow spreading ridges that do not correspond to linear scarps yet accommodate very high strain. Here we study fault scarps in young volcanic MOR seafloor, using high-resolution (1–2 m) bathymetry data of 8 sites with spreading rates of 14–110 km/Ma. Our results show a weak correlation between ATS and factors such as spreading rate, melt flux, or thermal regime, challenging the use of ATS as a proxy for the MOR tectonic component of plate divergence. Instead, ATS is time-dependent and heterogeneous spatially, controlled by the frequency and size of dike intrusions with associated faults and volcanic eruptions that resurface the seafloor and cover faults. Our findings also have implications for estimates of tectonic extension in subaerial volcanic rifting systems that undergo similar processes.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119174"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Pressure- and temperature-dependent anharmonicity of MgO: Implications for the thermal conductivity of planetary mantles","authors":"Saadi Chabane,&nbsp;Lorenzo Paulatto,&nbsp;Daniele Antonangeli,&nbsp;Paola Giura","doi":"10.1016/j.epsl.2024.119170","DOIUrl":"10.1016/j.epsl.2024.119170","url":null,"abstract":"<div><div>Thermal conductivity of minerals composing planetary mantles plays a fundamental role in controlling the heat propagation and hence the dynamic history of a planet. Here we present <em>ab-initio</em> calculations of the lattice dynamics and thermal conductivity of MgO as a function of temperature and pressure, accounting for phonon scattering and the renormalization it induces. Our calculations, validated by measurements of phonon energies and linewidths, point to a complex interplay between pressure-induced and temperature-induced effects, which influences the predominance of 3- or 4-phonon contributions, the former leading to a reduction in energies, the latter to an increase. Thus, not only the relative magnitude but also the sign of the anharmonic corrections depends strongly on the planetary geotherms. Our study shows that calculations taking into account only 3-phonon scattering underestimate thermal conductivity by 20–45% under the conditions of the Earth's lower mantle, while including anharmonic renormalization up to fourth order provides results in good agreement with high-pressure, high-temperature experiments. The predominance of 3-phonon interactions at core-mantle boundary (CMB) conditions significantly reduces phonon energies, leading to a thermal conductivity of 50.7 Wm^-1K^-1, further reduced by extrinsic effects, including isotopic disorder, oxygen vacancies and iron inclusion. In particular, oxygen vacancies of up to 1% decrease the thermal conductivity of MgO at CMB conditions by ∼40%, an effect that adds to that of Fe/Mg replacement. Our results indicate that mass disorder effectively reduces thermal conductivity of lower mantle minerals, contributing to the thermal blanketing that limits the heat flux from the core.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119170"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shear-induced dilation and dike formation during mush deformation","authors":"Amy G. Ryan ,&nbsp;Lars N. Hansen ,&nbsp;Amanda Dillman ,&nbsp;Mattia Pistone ,&nbsp;Mark E. Zimmerman ,&nbsp;Stewart A. Williams","doi":"10.1016/j.epsl.2024.119164","DOIUrl":"10.1016/j.epsl.2024.119164","url":null,"abstract":"<div><div>We present the results of high-temperature (900 °C), high-pressure (200 MPa) deformation experiments that identify the processes and deformation conditions leading to melt migration in crystal-rich mushes. This study is relevant to transport of magmas in transcrustal magma reservoirs. Experimental samples comprise juxtaposed pieces of soda-lime glass and densified mixtures of borosilicate glass and quartz sand, which, at elevated temperatures and pressures, have melt and shear viscosities similar to natural silicate melts and crystal-rich mushes. The synthetic mushes have crystal fractions of 0.60 to 0.83. Samples were deformed in torsion at shear strain rates of 10^–5 to 10^–4 s^-1 to shear strains up to 2.7. Image analysis of experimental samples shows melt migrates into the mush during shear. In mushes with crystal fractions ≥ 0.75 shearing causes melt-filled mm-scale dikes to form and propagate into the mush. To our knowledge, these features are the first dikes formed in high-temperature, high-pressure deformation experiments. Dike formation results from shear-induced dilation, which causes the mush to become underpressurized relative to the melt, at an estimated pressure differential of 10 MPa. Experimental conditions indicate shear-induced dilation and diking occur while the mush is still viscous (i.e., Weissenberg number &lt; 10^–2). We apply our results to Soufrière Hills Volcano (Montserrat, West Indies) and use our analysis to predict the deformation conditions that would lead to diking and rapid, voluminous melt migration in that active volcanic system.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119164"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Rheology of hydrous minerals in the subduction multisystem","authors":"Charis M. Horn,&nbsp;Philip Skemer","doi":"10.1016/j.epsl.2024.119171","DOIUrl":"10.1016/j.epsl.2024.119171","url":null,"abstract":"<div><div>The relatively low strength of the hydrous minerals has been theorized to play a role in the initiation of subduction through the feedbacks between faulting, hydration reactions, and rheological weakening. To further explore the behaviour of hydrous magnesium silicate minerals under the high stress conditions relevant to propagating faults, we performed nanoindentation tests on three serpentine species—lizardite, antigorite, and chrysotile—from room temperature up to their respective dehydration temperatures. While all serpentine minerals exhibit markedly lower indentation hardness than olivine under the same conditions (H_ol = 13.1–14.9 GPa), we find that antigorite (H_atg = 5.7–6.7 GPa) is almost a factor of three harder than lizardite (H_liz = 2.2–2.6 GPa), which is itself an order of magnitude harder than chrysotile (H_ctl = 0.1 GPa). We also indented chlorite from room temperature up to 400 °C and found that it has a hardness between that of lizardite and antigorite (H_chl = 2.8–4.0 GPa). Chrysotile is even weaker than the mineral talc (H_tlc = 0.6 GPa), another hydrous magnesium silicate, which was tested in a previous study. The weakest hydrous magnesium silicates – talc and chrysotile – are approximately one order of magnitude weaker than antigorite and almost two orders of magnitude weaker than olivine. There is a systematic relationship between indentation hardness and the lattice spacing between c-planes in these sheet silicates. Geodynamic models of subduction initiation typically use an ad hoc finite yield stress to trigger localized deformation. This study confirms that hydrous magnesium silicates are a likely candidate for alteration products that can facilitate localized deformation both before and after subduction initiation. However, the degree of weakening is highly dependent on the specific reaction product.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119171"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143157735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Crustal thickness effects on chemical differentiation and hydrology on Mars","authors":"Cin-Ty Lee ,&nbsp;Duncan Keller ,&nbsp;Rajdeep Dasgupta ,&nbsp;Kirsten Siebach ,&nbsp;Patrick McGovern ,&nbsp;Jackson Borchardt ,&nbsp;Julin Zhang","doi":"10.1016/j.epsl.2024.119155","DOIUrl":"10.1016/j.epsl.2024.119155","url":null,"abstract":"<div><div>The thermal state of planetary crusts depends primarily on heat flow from the mantle to the crust and the depth-integrated radioactive heat generation in the crust. The latter scales with crustal thickness, such that for a given concentration of heat-producing elements, the thicker the crust, the hotter it will be. If estimates of Martian crustal thickness are correct and if these thicknesses are representative of the Noachian crust, thermal modeling shows that the thick crust underlying the southern highlands should have been hot enough 4–3 billion years ago to produce widespread partial melting in the lower crust, whereas the thinner crust beneath the northern lowlands would not have been hot enough to melt. Widespread melting of the lower crust in the southern highlands should have generated significant amounts of silicic magmas, such as granites, as direct partial melts or by fractional crystallization of such melts. Silicic plutons are thus predicted to lie at depth beneath the southern highlands, now hidden beneath a carapace of younger basaltic flows. High surface heat flux imparted by the thick southern highlands crust would also have reduced the extent of permafrost, generating an underlying, stable aquifer of liquid water in the Martian regolith during the Noachian. Tapping of this aquifer by volcanoes or impacts may have caused episodic flooding on an otherwise frozen planet.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119155"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ultramafic-influenced submarine venting on basaltic seafloor at the Polaris site, 87°N, Gakkel Ridge","authors":"Elmar Albers ,&nbsp;Alexander Diehl ,&nbsp;Jessica N. Fitzsimmons ,&nbsp;Laramie T. Jensen ,&nbsp;Frieder Klein ,&nbsp;Jill M. McDermott ,&nbsp;Autun Purser ,&nbsp;Jeffrey S. Seewald ,&nbsp;Maren Walter ,&nbsp;Gunter Wegener ,&nbsp;Wolfgang Bach ,&nbsp;Antje Boetius ,&nbsp;Christopher R. German","doi":"10.1016/j.epsl.2024.119166","DOIUrl":"10.1016/j.epsl.2024.119166","url":null,"abstract":"<div><div>The nature of deep-sea hydrothermal systems is commonly inferred from physicochemical plume characteristics and seafloor observations, as was the case for the ‘Polaris’ site on the ultraslow-spreading Gakkel Ridge, Earth's northernmost hydrothermal system. Initial reports showing temperature and turbidity anomalies in its hydrothermal plume combined with its location on a neovolcanic axial seamount suggested a volcanically-hosted ‘black smoker’-type system. That interpretation, however, is inconsistent with our more complete data set derived from extensive water column sampling and seafloor surveys. The buoyant plume exhibits minor turbidity anomalies and low metal concentrations (dissolved Mn ≤ 3.1 nM), but contains substantial concentrations of H₂ (275 nM) and ¹³C-enriched CH₄ (365 nM, δ¹³C = –13.2). Instead of a ‘black smoker’ vent field, we observed small-scale chimney structures at the seafloor. Together, these data imply intermediate-temperature reaction of hydrothermal fluids with ultramafic rock in the subseafloor before discharge through pillow basalt outcrops at the seafloor. Our study challenges the ability of established approaches to vent exploration, reliant exclusively on in situ sensing to reveal the full geodiversity of subseafloor hydrothermal venting. Ultramafic-influenced systems, releasing H₂ and CH₄ into the ocean, may be a recurring feature along the entire 25% of the global ridge system that is ultraslow-spreading.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119166"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}