Earth and Planetary Science Letters最新文献

{"title":"Interaction of Kerguelen and Amsterdam-St. Paul dual hotspots with Southeast Indian Ridge","authors":"Yiming Luo ,&nbsp;Jian Lin ,&nbsp;Zhiyuan Zhou ,&nbsp;Xubo Zhang ,&nbsp;Fan Zhang ,&nbsp;Jinchang Zhang ,&nbsp;Han Chen","doi":"10.1016/j.epsl.2024.119088","DOIUrl":"10.1016/j.epsl.2024.119088","url":null,"abstract":"<div><div>We investigated the influence of the Kerguelen (K) and Amsterdam-St. Paul (ASP) dual hotspots on mantle evolution and crustal accretion in the eastern Indian Ocean. Using surface plate motion constraints from the global plate reconstruction model and the 3-D mantle convection code (ASPECT), we illustrated detailed processes of mantle upwelling, melting, and crustal accretion in the ridge-dual hotspot system. Model results demonstrate that the K hotspot significantly increased the mantle temperature over a wide region of over 1,500 km, leading to a 1–2 km increase in average crustal thickness along the entire Southeast Indian Ridge (SEIR). Only ridge-dual hotspot interaction models can explain key crustal variations along the SEIR. Gravity analysis revealed the K hotspot's long-term interaction with nearby ridges formed significant crustal anomalies, while the ASP hotspot's 10 Myr interaction with SEIR created localized anomalies. The distance between the ridge and hotspot, as well as plume flux, are key factors controlling the strength of ridge-hotspot interaction. The K hotspot, with its relatively higher plume flux, has double the influence distance of the ASP hotspot. Furthermore, our models indicate a possible direct interaction between the K and ASP hotspots, resulting in the ASP plume materials flowing towards the K plume.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119088"},"PeriodicalIF":4.8,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553601","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":"The sulfur isotopic composition of Cenozoic pyrite is affected by methane content and depositional environment","authors":"C. Spruzen ,&nbsp;H.J. Bradbury ,&nbsp;E.R. Kast ,&nbsp;A.V. Turchyn","doi":"10.1016/j.epsl.2024.119097","DOIUrl":"10.1016/j.epsl.2024.119097","url":null,"abstract":"<div><div>The sulfur isotopic composition of pyrite (δ³⁴S_pyr) is often used to reconstruct ancient geobiological processes, but recent studies have shown that δ³⁴S_pyr is strongly dependent on local sedimentary environmental conditions. Here we present a global compilation of &gt;3700 published pyrite sulfur isotopic compositions from the past 165 million years, from outcrop as well as marine sediment cores. We show that sediment core δ³⁴S_pyr has a statistically significant relationship with methane content, sedimentation rate, lithology, and proximity from shore, while outcrop δ³⁴S_pyr has distinct distributions depending on categories of depositional water depth and lithology. There are no obvious trends in the average δ³⁴S_pyr from the late Mesozoic to the present, although we suggest that this temporal record is affected by the inherent bias of data compilation. Our study further emphasizes the importance of considering sedimentology and stratigraphic context when using the sulfur isotopic composition of pyrite to infer global environmental changes.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119097"},"PeriodicalIF":4.8,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553602","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":"Prediction of barchan dunes migration using climatic models and speed-up effect of dune topography on air flow","authors":"C. Daudon ,&nbsp;M. Beyers ,&nbsp;D. Jackson ,&nbsp;J.P. Avouac","doi":"10.1016/j.epsl.2024.119049","DOIUrl":"10.1016/j.epsl.2024.119049","url":null,"abstract":"<div><div>This study presents and validates a workflow that quantitatively links the rate of barchan dunes migration, which can be measured from remote sensing, to the wind velocity, either measured at a meteorological station or extracted from reanalysis data. The workflow requires the selection of a sand transport law and a procedure to estimate the effect of the local topography on the near surface airflow, namely the speed-up effect, that results from the compression of streamlines as the wind climbs up the dune topography. Additionally, the estimate of sand flux under natural conditions needs to account for short duration wind gusts which are usually not fully accounted for or sampled in climatic models. Those spatial and temporal variations of wind speed have a strong influence on the local sand flux due to the non-linearity of the sand transport models. We investigate these effects by using computational fluid dynamic (CFD) modeling to estimate the speed-up effect on airflow and sand transport. We next include that effect to compare the predicted dune migration rate with remote sensing observations, at two desert barchan dune fields located along the southern rim of the Arabia Gulf. We find that, at the two sites, the speed-up effect increases the predicted sand flux by a factor of ∼3 and that the measured and predicted dune migration rates agree well if the sand transport law of <span><span>Kok et al. (2012)</span></span> is used, combined with the cessation threshold from <span><span>Pähtz and Durán (2023)</span></span> along with reanalysis data ERA5-Land with an hourly sampling. The proposed workflow is applicable to any barchan dune field on Earth or Mars.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119049"},"PeriodicalIF":4.8,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534641","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":"Decoding the interplay between magma thermodynamics and lithospheric thermal state as a possible explanation for the origin of the Daly Gap","authors":"Lucas Martins Lino ,&nbsp;Francy Roxana Quiroz-Valle ,&nbsp;Silvio Roberto Farias Vlach ,&nbsp;Valdecir de Assis Janasi ,&nbsp;Celso Renato Quiroz-Valle ,&nbsp;Miguel Ângelo Stipp Basei","doi":"10.1016/j.epsl.2024.119090","DOIUrl":"10.1016/j.epsl.2024.119090","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The mechanisms responsible for determining whether a magmatic system will generate a bimodal or monotonous intermediate volcanic suite are still widely debated in igneous petrology. Thus, the compositional characteristics of volcanic suites represent the ultimate reflection of their magmatic evolution and provide crucial insights into their remote volcanic and igneous plumbing systems. Decoding what these erupted compositions record is challenging however, and of paramount importance for volcanology, igneous petrology, and tectonic studies. This work employs an integrated petrological and thermal numerical modeling approach to identify the variables that modulate the compositional diversity registered in several volcano-tectonic settings, using two Neoproterozoic extensional rift basins in southern Brazil as case studies. Based on rhyolite-MELTS thermodynamic models of fractional crystallization, the resulting crystallization-differentiation curves of basaltic magmas indicate that the prevalence or scarcity of intermediate compositions in the volcanic record results from the thermodynamic control of differentiation patterns, whereas the numerical models also support the interplay with lithospheric heat transfer/maintenance processes. There is a well-known, yet underexplored, tendency of fractionating basaltic magmas to differentiate rapidly through intermediate compositions, possibly associated with a sudden increase in silica contents owing to Fe-Ti oxides crystallization and/or crystal productivity. This may explain the lack or scarcity of these compositions within predominantly bimodal volcanic suites, an observation known as the Daly Gap. The models presented in this contribution explore the nonlinear dependency between composition, crystallinity, and temperature (X-F-T) of differentiating basaltic magmas, which seems to be a common feature shared by alkaline, transitional, and even sub-alkaline basalts. When accounting for the considered thermic state of the medium they intrude into (&lt;em&gt;ca.&lt;/em&gt; 300 to 800 °C) and the modeled accretion rates (&lt;em&gt;ca.&lt;/em&gt; 0.01770 to 0.00354 m/yr) for intervals ≤ 300 ka, the models reveal that magma reservoirs undergoing crystallization-differentiation can only store intermediate compositions capable of erupting in relatively warm environments. Conversely, magma reservoirs with lower heat accumulation consist of alternating basic and silicic compositions, potentially giving rise to bimodal volcanic sequences. In these systems, compositional gaps are associated with increased crystal productivity over limited temperature intervals in the X-F-T space, coupled with relatively lower degrees of heat accumulation. Additionally, a subordinate compositional gap has been observed in the modeled silicic magmas, supporting our interpretation that increased crystal productivity results in subdued compositions along continuous liquid lines of descent. These nonlinear crystallization-fractionation patterns of ba","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119090"},"PeriodicalIF":4.8,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533958","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":"Anorthosites produced by water-fluxed anatexis of deep arc gabbros, Gangdese batholith, Tibet","authors":"Pengsheng Dong ,&nbsp;Roberto F. Weinberg ,&nbsp;Di-Cheng Zhu ,&nbsp;Eleanor C.R. Green ,&nbsp;Jiankang Yi ,&nbsp;Peter A. Cawood ,&nbsp;Shi-Min Li ,&nbsp;Shaorong Chen","doi":"10.1016/j.epsl.2024.119093","DOIUrl":"10.1016/j.epsl.2024.119093","url":null,"abstract":"<div><div>During arc growth, the remelting and cannibalization of older arc rocks may add to the complexity of the arc system, as shown by compositional variations that deviate from the normal compositional trends of arc magmas. While a range of arc rocks is ultimately produced, anorthosites are seldom described in arcs. Based on the study of gabbro migmatites and anorthosites from the eastern Gangdese arc in Tibet, supported by thermodynamic modelling, we demonstrate that anorthosites can form by anatexis of arc gabbros in deep crustal sections fluxed by aqueous fluids enriched in Na and Sr. Anorthosites in the eastern Gangdese arc are associated with the Lilong pluton, which comprises rocks ranging from ultramafic cumulates to gabbros and quartz diorites. The anorthosites appear as leucosomes in gabbro migmatites associated with residual melanosomes, dominated by amphibole, garnet and epidote. They appear also as dykes with variable contents of euhedral poikilitic amphibole, with or without garnet. These anorthosites exhibit distinctive compositions, with elevated Na₂O (&gt; 5 wt.%), Al₂O₃ (&gt; 20 wt.%) and Sr (&gt; 1000 ppm), as well as reduced rare earth element and high field strength element contents. These features set them apart from typical mantle-derived anorthosites, such as those in layered-intrusions. The anatectic rocks (magmatic and residual rocks) yield ages from 86 Ma to 75 Ma, recording &gt;10 Myr of anatexis. The start of anatexis overlaps the youngest ages in the protolith gabbros (97 Ma to 84 Ma) suggesting the possibility of anatexis starting before the end of complete protolith crystallization. Phase equilibrium calculations demonstrate that anorthositic melts can be produced by the melting of gabbroic rocks under granulite-facies at ∼ 1.2 GPa and ∼ 950-830 °C in the presence of significant H₂O influx with added Na. Melt generation produces a residue enriched in garnet, amphibole and epidote, consistent with field observations and previous experimental studies. Composition of zircons in the residue and in the anatectic anorthosites tell complementary stories about the melting process. Significantly, anorthosite zircons are characterized by high Eu/Eu* and low Th concentrations, indicative of plagioclase breakdown, and apatite and epidote remaining in the source. This signature of arc anorthosite zircons can be used to search for anorthosite contribution elsewhere. The results highlight the role of Na-Sr aqueous fluids in the arc root in generating unusual magmas that result in compositional diversity of arc magmas.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119093"},"PeriodicalIF":4.8,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533960","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":"Characterization of bedrock mass-wasting at fault-bound abyssal hills","authors":"Alex Hughes ,&nbsp;Jean-Arthur Olive ,&nbsp;Luca C. Malatesta ,&nbsp;Javier Escartín","doi":"10.1016/j.epsl.2024.119073","DOIUrl":"10.1016/j.epsl.2024.119073","url":null,"abstract":"<div><div>Fault-bound abyssal hills form at mid-ocean ridges and cover ∼65 % of Earth's surface, but few studies have characterized the extent to which bedrock erosion controls their morphology. Here, we use bathymetry data to characterize the morphology of fault-bound abyssal hills on a global scale, and employ numerical modelling and seismicity catalogues to quantify how simultaneous rock uplift and bedrock erosion sculpt deep-ocean landscapes. By generating a global database on abyssal hill morphology, we show that most large abyssal-hill scarps (&gt;100 m in height) within the near-axis zone of seismicity (i.e., &lt;30 km from axis) have slopes between 10 and 30°, well below the expected range of underlying normal fault dips of 45–60°. We interpret this as a manifestation of efficient bedrock mass wasting on near-axis growing faults, a process that operates from fault inception. Using a non-linear topographic diffusion model to parameterise the effects of erosion, we find a balance between erosion and rock uplift that is similar for slow, intermediate, and fast spreading rates. We express the ratio of erosion to uplift as an inverse Peclet number that ranges between 0.06 and 0.82 for abyssal hills. We also calculate a global bedrock diffusivity for abyssal hills in the range 0.01–1.51 m² yr⁻¹. These results imply that bedrock erosion is a significant process that sculpts abyssal hill morphology and reshapes the oceanic crust. Overall, this study provides a framework to incorporate bedrock mass wasting into future models of ocean-floor evolution and, more generally, to active extensional settings on Earth and beyond.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119073"},"PeriodicalIF":4.8,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533957","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":"Iron-sulfur-carbon redox interactions in the continental subduction factory and their effect on volatile element storage in the mantle wedge","authors":"Bibiana Förster ,&nbsp;Sonja Aulbach ,&nbsp;Gray E. Bebout ,&nbsp;Gianluca Bianchini ,&nbsp;Claudio Natali ,&nbsp;Roberto Braga","doi":"10.1016/j.epsl.2024.119074","DOIUrl":"10.1016/j.epsl.2024.119074","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The ultramafic rocks of the Ulten Zone tectonic mélange experienced a well-documented multi-stage metamorphic history, from residence in a hot mantle wedge to down-dragging and trapping in a Variscan slab accompanied by amphibolitisation, and finally two-stage exhumation accompanied by chloritisation and serpentinisation. We use these rocks as a natural laboratory to investigate whether volatile element fluxes in continental subduction zones promote long-term volatile element storage in the overlying mantle wedge. Here, we obtained new data on the chemical composition, iron speciation, carbon concentrations and isotopic compositions of ultramafic bulk rocks, and the carbon-oxygen isotope composition of carbonates in samples from &gt;10 ultramafic lenses, which we combine with previously published data for additional insights.&lt;/div&gt;&lt;div&gt;The carbonate stable isotope compositions show a distinct provinciality, whereby rocks from the little retrogressed ultramafic lenses in the NE Ulten Zone domain have lower average δ&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;V-PDB&lt;/sub&gt; and δ&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;V-SMOW&lt;/sub&gt; of –16.8‰ to –5.7‰ and +8.0‰ to +17.8‰, respectively, than those in the more retrogressed SW domain (–11.2‰ to 0.0‰ and +12.9‰ to +20.7‰, respectively), suggesting influx of distinct crustal fluids. Bulk-rock carbon contents range from 130 to 28,000 μg g&lt;sup&gt;-1&lt;/sup&gt;, exceeding estimates for the convecting mantle, and are on average higher in rocks from the NE domain (median 880 μg g&lt;sup&gt;-1&lt;/sup&gt;), which can be modelled as Rayleigh-style dolomite addition at ∼800–700 °C. Rocks from the SW domain have lower C contents (median 570 μg g&lt;sup&gt;-1&lt;/sup&gt;) which correlate positively with δ&lt;sup&gt;13&lt;/sup&gt;C and can be modelled as Rayleigh-style calcite addition at ∼500–400 °C. The lowest δ&lt;sup&gt;13&lt;/sup&gt;C and C contents point to dedolomitisation during low-temperature (400 °C) serpentinisation, and furthermore suggest the contribution of a &lt;sup&gt;13&lt;/sup&gt;C-depleted phase to the bulk-rock compositions.&lt;/div&gt;&lt;div&gt;After melt depletion during formation of the pre-Variscan continental lithosphere, the sulfur inventory was replenished during amphibolitisation near peak-metamorphic conditions, via sulphidation during interaction with siliceous fluid. Sulfur was markedly (re-)depleted during processes related to exhumation, reflecting low sulfur fugacity during chloritisation and serpentinisation. The available data suggest that the high bulk-rock Fe&lt;sup&gt;3+&lt;/sup&gt;/ΣFe (median 0.18) resulted from reduction of some aqueous sulphate during amphibolitisation, accompanied by redox-neutral carbonation, and from carbonate reduction during chloritisation when sulfur fugacity was low.&lt;/div&gt;&lt;div&gt;Ignoring exhumation-related C loss and taking near-peak metamorphic conditions as representative, significant amounts of C in carbonates and water in amphiboles may be stored in continental mantle wedges. These are subsequently stabilised below collisional orogens, which cover vast areas of Earth's conti","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119074"},"PeriodicalIF":4.8,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533959","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":"Magmatic degassing dynamics at Halema'uma'u Crater, Kīlauea, Hawaii","authors":"A. La Spina ,&nbsp;M. Burton ,&nbsp;B.F. Houghton ,&nbsp;A.J. Sutton ,&nbsp;B. Esse","doi":"10.1016/j.epsl.2024.119062","DOIUrl":"10.1016/j.epsl.2024.119062","url":null,"abstract":"<div><div>Lava lake activity within Halema‘uma‘u crater on Kīlauea volcano, Hawaii, between 2010 and 2018 provided a remarkable opportunity to observe the dynamics of magmatic degassing occurring in both quiescent and lava-spattering degassing regimes. We collected open-path FTIR absorption spectra of magmatic gas in December 2015, when distributed lake surface degassing and spattering activity occurred on the SE margin of the lava lake. We quantified seven volcanic gas species, H₂O, CO₂, SO₂, HCl, HF, CO and OCS, distinguishing between spattering and lake surface degassing. Passive and solar traverse measurements allowed quantification of compositions and relative SO₂ emission rates of 60 % from spattering and 40 % from lake surface degassing. Spattering gas has a CO₂/SO₂ molar ratio of 0.88 compared with 0.56 for lake surface degassing, consistent with a partial sulphur loss from magma during spattering. We propose that spattering is the result of continuous formation of coalescing gas bubbles driven by downwelling lava lake crust, which promotes gas loss from 10s-100 s of metres within the lake. Spattering degassing provide a mechanism for partial degassing of magma within the Halema‘uma ‘u lava lake, and production over time of a large volume of partially degassed magma. This is in agreement with petrological models indicating that summit-derived partially degassed magma accumulated in the MERZ in the decade prior to the 2018 LERZ eruption. Calculations of equilibrium temperature and redox state are consistent with gas-rock buffering.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119062"},"PeriodicalIF":4.8,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533956","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":"Earth's precession rate evolution and rapid fall during the Late Proterozoic","authors":"David Waltham ,&nbsp;Mattias Green","doi":"10.1016/j.epsl.2024.119086","DOIUrl":"10.1016/j.epsl.2024.119086","url":null,"abstract":"<div><div>We consider the use of cyclostratigraphic estimates of ancient Earth-axis precession rates, <em>k</em>, as a proxy for ancient length of day and ancient Earth-Moon distance. Analysis of published estimates for <em>k</em> indicate a statistically robust acceleration in the rate at which <em>k</em> fell during the Late Proterozoic. We investigate whether this accelerated fall-rate can be reasonably explained by an increase in tidal drag, at that time, or whether alternate explanations are needed. A tidal drag explanation requires an unusually large and long-lived resonance in Earth's oceans. However, alternate explanations are even less viable. A rearrangement of Earth's internal structure can be ruled out by the excessive geothermal heat production this would have caused, whilst mass redistribution due to Late Proterozoic glaciation can also be ruled out as the <em>k</em>-history did not return to its former trend after glaciation ended. Disruption of the Earth-Moon-Sun system by a nearby passing star is similarly unable to account for the observations since the required disruption is much too large to have happened without additional, clearly observable effects. We also consider a possible impact from thermally driven, atmospheric tides but reject this explanation as it would decelerate the fall in precession rather than accelerate it. These conclusions required development of novel techniques for inverse modelling the <em>k</em>-history to directly give (i) tidal-drag and (ii) the potential energy liberated by internal mass distribution.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119086"},"PeriodicalIF":4.8,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533967","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":"Geochemical constraints on reaction temperature and pressure and heat- and mass-transfer efficiency at Rainbow Hydrothermal Field","authors":"Guy N. Evans ,&nbsp;Adedapo N. Awolayo ,&nbsp;Benjamin M. Tutolo ,&nbsp;William E. Seyfried Jr.","doi":"10.1016/j.epsl.2024.119063","DOIUrl":"10.1016/j.epsl.2024.119063","url":null,"abstract":"<div><div>Seafloor vent fluids hosted by oceanic core complexes (OCCs) are thought to represent circulation of seawater-derived hydrothermal fluid along deeply penetrating, low-angle detachment faults. However, estimation of the source temperatures and pressures of such fluids has been limited because geochemical methods typically require vent fluid silica concentrations to be buffered by quartz, a condition not often met at oceanic core complexes. Here, we extend the calculation of the Si-Cl geothermobarometer to enable predictions of fluid Si concentrations in equilibrium with any Si-buffering mineral assemblage, rather than being restricted to quartz. We apply this method to Rainbow Hydrothermal Field vent fluid compositions and find that they are consistent with buffering by a plagioclase+talc+chlorite+tremolite mineral assemblage at conditions ranging from (430 °C, 359 bar) to (470 °C, 468 bar), which correspond to depths of 1.3–2.4 km below the seafloor. These estimates agree well with the locations of seismically imaged magma chambers within the Rainbow Massif. Additionally, calculations of fluxibility and Fe solubility support this relatively shallow origin for Rainbow vent fluids and imply relatively efficient heat and Fe extraction from the seafloor. We estimate that only 24–30 % of the heat content and almost no Fe is lost during upflow of Rainbow vent fluids.</div><div>Compared to other OCC-hosted seafloor vents, the source region of Rainbow vent fluids is anomalously shallow, an observation consistent with geological interpretations of the Rainbow Massif. Vent fluids at Rainbow Hydrothermal Field have exhibited apparently stable and greater-than-seawater salinity for over two decades. We interpret these vent fluids as vapors derived from a higher-salinity source fluid that developed over multiple cycles of magma injection and phase-separation inherent to the formation of oceanic crust along slow-spreading, non-volcanic segments of oceanic spreading centers. Alternatively, higher-salinity source fluids could be derived from mineral hydration reactions associated with serpentinization of ultramafic rocks. The occurrence of greater-than-seawater salinity vent fluids is thus predicted to be a common feature of OCC-hosted vent fields, as indicated by several known examples, including the TAG, Kairei, and Edmond vent fields.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119063"},"PeriodicalIF":4.8,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533955","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}