Earth and Planetary Science Letters最新文献

{"title":"Aerobic nitrogen cycling in a molybdenum-limited, redox-stratified Mesoproterozoic epeiric sea","authors":"Geoffrey J. Gilleaudeau ,&nbsp;Linda C. Kah ,&nbsp;Christopher K. Junium ,&nbsp;Ariel D. Anbar","doi":"10.1016/j.epsl.2025.119369","DOIUrl":"10.1016/j.epsl.2025.119369","url":null,"abstract":"<div><div>Nitrogen is a critically important element for life on Earth, and its cycling through the ocean-atmosphere system is a biologically mediated process that requires a suite of transition metals as enzyme cofactors. For example, the most common form of nitrogenase (the enzyme that mediates nitrogen fixation by prokaryotes) requires molybdenum and iron as structural components. It has been proposed, however, that ‘alternative nitrogenase’ enzymes may have been important under conditions of expanded euxinia and Mo drawdown that may have characterized parts of the Proterozoic oceans. Furthermore, it has been proposed that bioavailable nitrate was scarce in the Mesoproterozoic oceans, inhibiting the evolution of eukaryotes that lack the ability to fix their own nitrogen. To test these hypotheses, we examined nitrogen isotopes (δ¹⁵N) in black and grey shale of the ∼1.1 Ga Atar and El Mreiti groups, Taoudeni Basin, Mauritania as a proxy for nitrogen cycling in the Mesoproterozoic oceans. These strata were previously investigated for iron speciation and trace metal content, and they record a period of substantial Mo drawdown in a redox-stratified epeiric sea. In the Atar and El Mreiti groups, both shallow epicratonic and deeper pericratonic environments record strongly positive δ¹⁵N values (median = +4.6‰), indicative of an aerobic nitrogen cycle characterized by nitrification and partial denitrification, and thus surface waters that were replete in bioavailable nitrate. Even in the most Mo-limited euxinic environments, positive δ¹⁵N values suggest nitrate-replete surface waters. These results are consistent with a large compilation of δ¹⁵N data from other Mesoproterozoic basins, which collectively do not support the presence of a metal-nitrogen co-limited biosphere in the Mesoproterozoic oceans. Instead, we suggest that nitrogen fixation likely proceeded via Mo-Fe-nitrogenase and nitrate was readily available in the oceans during much of the Mesoproterozoic, with phosphorus acting as the limiting macronutrient on the marine biosphere.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"661 ","pages":"Article 119369"},"PeriodicalIF":4.8,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143875055","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":"Volcano-tectonic controls on magma residence time in arc crusts: Insights from noble gas geochemistry in the Andean Southern Volcanic Zone.","authors":"Camila Poblete-González ,&nbsp;Tom Grelet ,&nbsp;Daniele Tardani ,&nbsp;Daniele Pinti ,&nbsp;Pablo Sanchez-Alfaro ,&nbsp;Fernanda Álvarez-Amado ,&nbsp;Santiago Tassara ,&nbsp;Philippe Robidoux ,&nbsp;Pamela Pérez-Flores ,&nbsp;Felipe Aron ,&nbsp;Kim Berlo ,&nbsp;Marco Taussi","doi":"10.1016/j.epsl.2025.119352","DOIUrl":"10.1016/j.epsl.2025.119352","url":null,"abstract":"<div><div>The Southern Volcanic Zone of the Andes (SVZ) is a unique natural laboratory to explore the interaction between tectonic and volcanic processes. This study used the helium isotopic composition (<em>R</em> = ³He/⁴He of the sample) of volcanic rocks and geothermal gases to determine magma storage timescales across different volcano-tectonic settings. Precisely, we assess how transtensional and transpressional crustal settings linked to the interaction of the intra-arc Liquiñe-Ofqui Fault System (LOFS) and the margin-oblique Andean Transverse Faults (ATF), influence magma storage conditions and residence times. We focused on two volcanic systems: Sollipulli and Cordón Caulle. Measured helium isotope ratios normalized to the air ratio (or R/Ra) in geothermal gases range from 5.88 - 6.98 Ra for the Sollipulli and 2.37 - 5.42 Ra for Cordón Caulle, while the expected mantle endmember in this region is 7.9 Ra. Cordón Caulle's rocks showed the larger range of helium isotope ratios, with the highest of 5.71 Ra. We solved magma aging models, incorporating Monte Carlo simulations, to assess the progressive dilution of the magmatic ³He/⁴He endmember due to the addition of locally produced radiogenic ⁴He from decay of U and Th contained in magma chambers. Our results show shorter residence times at Sollipulli (31.8 ± 16.4 Ky), associated with transtensional LOFS-controlled setting, and longer residence times at Cordón Caulle (86.8 ± 27.8 Ky), linked to a transpressional ATF regime. These findings underscore the influence of both fault systems and deformation style on magma residence time, offering new insights into the processes that drive volcanic activity in the SVZ.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"661 ","pages":"Article 119352"},"PeriodicalIF":4.8,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143859323","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":"Massive organic carbon burial in the North China Basin is a main contributor to peak Late Paleozoic Ice Age in early Asselian","authors":"Dawei Lv ,&nbsp;Yongtao Zhao ,&nbsp;Ronald J Steel ,&nbsp;Haibo Jia ,&nbsp;Munira Raji ,&nbsp;Zhihui Zhang ,&nbsp;Lei Ju ,&nbsp;Lihua Gong ,&nbsp;Xinyi Wang","doi":"10.1016/j.epsl.2025.119370","DOIUrl":"10.1016/j.epsl.2025.119370","url":null,"abstract":"<div><div>The driving factors of the peak Late Paleozoic Ice Age (LPIA) in the Early Permian are still controversial. We aim to contribute to this issue by highlighting the significance of the volume and rate of organic carbon burial (OC) in the North China Basin (NCB) during the late Gzhelian and early Asselian. Tectonic uplift along the northern margin and adjacent regional subsidence of the NCB provided accommodation for large volumes of OC burial during this period. Notably, there was accelerated uplift of the northern margin of NCB during the early Asselian, causing increased source-area relief, greater sediment yield and increased sedimentation rates in the adjacent subsiding basin. The extended basinward growth of the Asselian clastic wedge also caused sharply expanded terrestrial vegetation and increased paleo-ocean primary productivity. The early Asselian OC burial magnitude accounted for ∼ 47 % of the global OC magnitude in the same period and resulted in a significant decrease of <em>p</em>CO₂. We argue that this significant NCB OC sink contributed greatly to the peak of the LPIA in Early Asselian.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"661 ","pages":"Article 119370"},"PeriodicalIF":4.8,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143859322","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":"Titanium isotopes as a tracer of eclogite in the mantle sources of continental intraplate basalts","authors":"Jian Zhao ,&nbsp;Xiao-Jun Wang ,&nbsp;Xin-Miao Zhao ,&nbsp;Jian-Qiang Liu ,&nbsp;Gang Zeng ,&nbsp;Chun-Xia Yi ,&nbsp;Bing Liu ,&nbsp;Jin Li ,&nbsp;Xiang-Kun Zhu ,&nbsp;Li-Hui Chen","doi":"10.1016/j.epsl.2025.119366","DOIUrl":"10.1016/j.epsl.2025.119366","url":null,"abstract":"<div><div>Recycled oceanic crust and sediments play a crucial role in generating the chemical and lithological heterogeneity of the Earth's mantle. However, unequivocally identifying the lithological properties of these recycled crustal materials in the mantle sources of basalts remains a challenge, despite its significant implications for mantle dynamics and the generation of magma diversity. Here, we explore titanium (Ti) stable isotopes as a novel method for tracing eclogite melting in the source of intraplate basalt. We present new Ti isotope data for a suite of well-characterized intraplate basalts from northeast (NE) China, which were thought to be formed through interaction between primitive low-MgO melts derived from eclogitic recycled crust and the local lithospheric mantle peridotite. Results show that these basalts display large Ti isotopic variation, with δ^49/47Ti values ranging from −0.05‰ to 0.14‰. The δ^49/47Ti values are well correlated with radiogenic Sr–Nd–Pb isotopes and stable Fe isotopes, suggesting the mixing of two endmembers with distinct Ti isotopic compositions. The low-δ^49/47Ti endmember exhibits depleted Sr–Nd isotopic compositions that resemble those of the local lithospheric mantle peridotite. The high-δ^49/47Ti endmember (δ^49/47Ti ≥ 0.14‰) is characterized by an elevated δ^57/54Fe value (≥ 0.3‰) and low values of MgO (≤ 5 wt.%), CaO/Al₂O₃ (≤ 0.4), Nb/Nb* (≤ 0.7), and Ti/Ti* (≤ 0.6), which require an eclogite melt component in equilibrium with residual rutile in the source. Our thermodynamic modeling and mass balance calculations further suggest that such a melt can be produced by partial melting of a rutile-bearing eclogite, which has a protolith of mixed recycled oceanic crust and sediments. Therefore, this study highlights that Ti isotopes can serve as a novel tool for identifying the contribution of rutile-bearing eclogite to intraplate basalts.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"660 ","pages":"Article 119366"},"PeriodicalIF":4.8,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143843664","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":"Cerium isotopic fractionation during magmatic processes and the composition of the upper mantle","authors":"Fang Liu ,&nbsp;Hongli Zhu ,&nbsp;Michael R. Perfit ,&nbsp;Xin Li ,&nbsp;Yajun An ,&nbsp;Mingxing Ling ,&nbsp;Zhaofeng Zhang","doi":"10.1016/j.epsl.2025.119365","DOIUrl":"10.1016/j.epsl.2025.119365","url":null,"abstract":"<div><div>Cerium (Ce) is a refractory, incompatible and redox-sensitive element and its isotopes can be used to trace planetary accretion and evolution in the early solar system. A knowledge of the isotopic composition of rocks that sample from the Earth's mantle is a prerequisite to understand curst-mantle evolution. In this study, we present the first comprehensive high-precision Ce stable isotopic compositions of different types of igneous rocks, including sixteen normal mid-ocean ridge basalts (N-MORB) from the East Pacific Rise (EPR) and Juan de Fuca Ridge (JdF), two depleted mid-ocean ridge basalts (D-MORB) from the EPR and Ecuador Rift, seven evolved lavas (basaltic andesites, andesites, and dacites) from the EPR. These igneous rocks, spanning compositions from primitive basalt to evolved dacite with MgO contents decreasing from 8.09 to 0.80 wt. %, display a limited variation in δ¹⁴²Ce from -0.038 to 0.024 ‰. Although these rocks have experienced different amounts and proportions of olivine, clinopyroxene, plagioclase, Fe-Ti oxides, and apatite fractional crystallization, no Ce isotopic fractionation was detected. The δ¹⁴²Ce values of MORBs show no correlation with La/Sm_(N) or Nb/Y, indicating that partial melting process cannot induce significant Ce isotopic fractionation. Our batch non-modal melting modelling shows that more than 95 % of the Ce budget will be extracted into melt after only 5 % degree of partial melting. Therefore, we conclude that Ce isotopic fractionation during magmatic processes is insignificant and the average δ¹⁴²Ce of studied samples of -0.005 ± 0.028 ‰ (2SD, <em>N</em> = 25) can be the best estimate of upper mantle's isotopic composition. Based on simple mass-balance calulation, the Ce isotopic composition of the bulk silicate Earth (BSE) is roughly estimated to be -0.008 ± 0.025 ‰ (2SD, propagated error).</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"661 ","pages":"Article 119365"},"PeriodicalIF":4.8,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143852231","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":"Water solubility in nominally anhydrous minerals in a silica-rich system at the top lower mantle","authors":"Luyao Chen ,&nbsp;Zhaodong Liu ,&nbsp;Xinyu Zhao ,&nbsp;Chaowen Xu ,&nbsp;Dongyang Ju ,&nbsp;Bingtao Feng ,&nbsp;Jinze He ,&nbsp;Ran Liu ,&nbsp;Xinyang Li ,&nbsp;Wei Du ,&nbsp;Bingbing Liu ,&nbsp;Wenliang Xu","doi":"10.1016/j.epsl.2025.119360","DOIUrl":"10.1016/j.epsl.2025.119360","url":null,"abstract":"<div><div>Although aluminous stishovite plays an important role in water transport and storage in the lower mantle, its water capacity in the top lower mantle is still poorly constrained. Here, we systematically investigated the water solubility in aluminous stishovite coexisting with bridgmanite, periclase, calcium ferrite-type phase, etc., in the presence of hydrous melts in a silica-rich MgO–Al₂O₃–SiO₂–H₂O system at pressures of 23–32 GPa and temperatures of 1600–2100 K using tungsten carbide anvils in a Walker-type large-volume press. Aluminous stishovite can accommodate significant amounts of water up to ∼3611 ppm wt., while the coexisting nominally anhydrous minerals have a very limited water storage capacity and are nearly dry. The water solubility in stishovite increases almost linearly from ∼296 to ∼3611 ppm wt. H₂O with increasing Al₂O₃ content from ∼0.3 to 3.0 wt. %. Our study further suggests that aluminous stishovite is a dominant phase for water transport and storage in a subducted oceanic crust at depths of 660–850 km, while the top peridotitic or pyrolitic lower mantle is nearly dry at least up to 850 km owing to the dry major phases of bridgmanite and periclase. The high water storage capacity of aluminous stishovite may prevent the occurrence of partial melting caused by the release of water from subducted slabs at the top of the lower mantle. The presence of hydrous aluminous stishovite may provide a plausible explanation for the high conductivity anomalies occasionally observed in some subducted slabs in the top lower mantle.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"660 ","pages":"Article 119360"},"PeriodicalIF":4.8,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834936","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":"Volcanic gases reflect magma stalling and launching depths","authors":"Shuo Ding ,&nbsp;Terry Plank ,&nbsp;J. Maarten de Moor ,&nbsp;Yves Moussallam ,&nbsp;Maryjo Brounce ,&nbsp;Peter Kelly","doi":"10.1016/j.epsl.2025.119349","DOIUrl":"10.1016/j.epsl.2025.119349","url":null,"abstract":"<div><div>Many open-vent arc volcanoes display two modes in their continuous gas emissions, one with a characteristic CO₂/ S_T ratio typical of periods of quiescent degassing and another punctuated by high CO₂/ S_T gas emitted in the weeks before eruption, a recently recognized eruption precursor. In this study we explore the origin of the two modes of degassing revealed by time-series gas data at Turrialba volcano (Costa Rica) in the context of new melt inclusion (MI) data. To reconstruct the c[CO₂] of undegassed magma, we developed a rapid-quench piston-cylinder assembly to rehomogenize the vapor bubble commonly contained in MIs. We focus on olivine-hosted MIs from a mafic scoria sample erupted from Turrialba in 1864–1866. The reconstructed CO₂ contents in MIs decrease from ∼4000 to &lt;1000 ppmw as S contents decrease from 3500 to &lt;1000 ppmw. The highest reconstructed S and CO₂ in the MIs resulted in an initial magmatic CO₂/ S_T ratio (molar) of 0.83. Informed by the MI data, we modeled the decompression degassing of Turrialba magma and vapor composition using the Sulfur_X and EVo models. Instead of being controlled by initial magmatic CO₂/S_T ratio as suggested by previous studies, we find that the quiescent gas emitted from Turrialba during 2014–2018 (CO₂/ S_T = 2.3 ± 0.8, molar) appears to reflectequilibrium with magmas stored at 4–8 km (Sulfur_X) or 2 km (EVo) depth, when H₂O is degassing extensively from the magma. A magma storage region at 4–8 km is also supported by seismic tomography. The second gas mode is noted by spikes in CO₂/ S_T ∼ 7.9 ± 2 in the weeks prior to eruption. This gas reflects equilibrium with a magma at 12–18 km (Sulfur_X) or 4–8 km (EVo), where the ascending magma is saturated with a CO₂-rich vapor. Thus, there are two important trans crustal depths beneath the volcano: one where the rate of H₂O loss from the magma and thus magma viscosity increases, and one at greater depths where high CO₂/S_T vapor forms and may facilitate dike propagation. We interpret the shallower, H₂O-loss region as the main site of magma stalling and storage, where quiescent gas is generated continuously. We interpret the greater depth (12–18 km) as the source of the precursory gas that precedes eruption, and where the mafic melt lastly equilibrated with a mush zone before ascending and triggering eruption weeks later. This hypothesis is ripe for testing at other volcanoes that exhibit two modes in gas geochemistry.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"660 ","pages":"Article 119349"},"PeriodicalIF":4.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834935","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":"Thor: a rock strength database for investigating lithologic controls in landscape evolution","authors":"Mauricio B. Haag ,&nbsp;Lindsay M. Schoenbohm","doi":"10.1016/j.epsl.2025.119364","DOIUrl":"10.1016/j.epsl.2025.119364","url":null,"abstract":"<div><div>Topographic information has been widely used to provide insights into tectonics and climate. However, these metrics are subject to lithologic effects that limit our understanding of how landscapes grow, evolve, and decay. To address this, we compile over 6100 Schmidt hammer-based rock strength measurements from 264 published studies to create an extensive rock strength database that we call <em>Thor</em>. We use this database to perform a meta-analysis that enables us to quantify, on a global scale, the impact of lithology on fluvial metrics. Our findings reveal a strong correlation between topographic metrics and rock strength, particularly the normalized steepness index (<em>k_sn</em>) and the fluvial erodibility coefficient (<em>K</em>). Additionally, using four case studies worldwide we identify that incorporating rock strength data improves the correlation between measured and predicted erosion rates for all sites, regardless of tectonic activity and climate setting. While we acknowledge the roles of climate and tectonics in shaping Earth's surface, our findings reveal a notable influence of lithology in landscape evolution, both globally and locally. These findings underscore the potential bias introduced by spatially variable lithology on commonly used topographic metrics for inferring drainage reorganization, incision, tectonics, and climate forcing.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"660 ","pages":"Article 119364"},"PeriodicalIF":4.8,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143825921","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":"CaCO3 precipitation kinetics and polymorphism in ferruginous seawater","authors":"Ben Davis Barnes ,&nbsp;Clancy Zhijian Jiang ,&nbsp;Peter Methley ,&nbsp;Justin V. Strauss ,&nbsp;Nicholas J. Tosca","doi":"10.1016/j.epsl.2025.119345","DOIUrl":"10.1016/j.epsl.2025.119345","url":null,"abstract":"<div><div>Secular trends in Precambrian calcium carbonate (CaCO₃) sediments that nucleated within the water column or precipitated directly on the seafloor reflect evolving chemical controls on their formation. Previous work has hypothesized that kinetic inhibitor species like ferrous iron (Fe²⁺) significantly raised the free energy barrier to CaCO₃ nucleation and drove alternative mineralization pathways. However, direct evidence for Fe²⁺-inhibition on CaCO₃ precipitation in anoxic seawater is limited. Here we present experimental results on the nucleation of carbonate minerals in simulated anoxic Archean-Paleoproterozoic seawater across a range of ferrous iron concentrations ([Fe²⁺] = 0.05 to 5.0 mmol/kg) and calcite saturation states. With increasing [Fe²⁺] the rate of CaCO₃ precipitation decreased, aragonite increased in abundance over calcite, and calcite crystallites exhibited marked morphological modification. We observed no concentration of ferrous iron at which calcite nucleation is fully suppressed, but at [Fe²⁺] &gt; 1 mmol/kg noted aggregates of variably Ca-rich, Fe(II)-bearing carbonate which may have crystallized from an amorphous Ca-Fe carbonate precursor. Our results suggest that it is unlikely that dissolved iron was present in high enough concentrations to independently control secular trends in Precambrian carbonate sedimentation, but that Fe²⁺-inhibition contributed to maintaining supersaturation with respect to calcite. Furthermore, our results imply that the nucleation of ferroan calcite and/or amorphous Ca-Fe carbonate from supersaturated ferruginous solutions served as an additional and potentially significant sink for iron from the Precambrian oceans.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"660 ","pages":"Article 119345"},"PeriodicalIF":4.8,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143825920","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 refined isotopic composition of cometary xenon and implications for the accretion of comets and carbonaceous chondrites on Earth","authors":"William S. Cassata","doi":"10.1016/j.epsl.2025.119307","DOIUrl":"10.1016/j.epsl.2025.119307","url":null,"abstract":"<div><div>The origins of Earth's volatiles, including water, remain uncertain. Noble gases can be used to constrain volatile sources as they exhibit significant chemical and isotopic variations amongst Solar System materials that Earth may have accreted. Here, I refine the isotopic composition of cometary xenon (Xe) measured during the Rosetta mission by optimizing its fit to isotopically similar presolar grains in meteorites. Using this composition, I show that Earth's atmosphere can be explained as a mixture of 83.6 ± 3.2% meteoritic, 15.3 ± 2.8% cometary, and 1.1 ± 0.7% fission Xe (1σ; percentages are with respect to ¹³²Xe). This same approach applied to Kr indicates Earth's atmosphere is 72.1 ± 9.5% meteoritic and 27.9 ± 9.5% cometary Kr (1σ; percentages are with respect to ⁸⁴Kr). Carbonaceous chondrites are likely the predominant source of meteoritic Xe. A carbonaceous chondrite accretion mass of 1.8– 5.2 wt.-% of Earth at the 95% confidence interval explains the relative abundances of meteoritic and fission Xe in Earth's atmosphere. Such accretion may have delivered up to 6 – 18 oceans of water to Earth. Conversely, a cometary ice accretion mass of less than 5 × 10^–5 wt.-% of Earth explains the relative abundance of cometary Xe. This would have delivered less than 0.2% of Earth's water. The data further imply a more linear temporal variation in the mass dependent fractionation of atmospheric Xe throughout the first two billion years of Earth history than previously thought.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"660 ","pages":"Article 119307"},"PeriodicalIF":4.8,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143825919","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}