Earth and Planetary Science Letters最新文献

{"title":"An abrupt change in source materials for Chinese loess deposits at the Pliocene-Pleistocene boundary: Insights from K isotopes and modeling","authors":"Jun Mu ,&nbsp;Jiawei Da ,&nbsp;Hu Yang ,&nbsp;Junfeng Ji ,&nbsp;Lianwen Liu ,&nbsp;Weiqiang Li","doi":"10.1016/j.epsl.2025.119543","DOIUrl":"10.1016/j.epsl.2025.119543","url":null,"abstract":"<div><div>The eolian deposits on the Chinese Loess Plateau (CLP) are key archives of late Cenozoic climate changes and atmospheric circulation, However, the long-standing controversy about the stability of dust sources over the last ∼ 6 Myr limits our understanding of the genesis of the CLP and its paleoenvironment implications. Here we report that an abrupt decrease in K isotope compositions (δ⁴¹K) of the CLP eolian deposits occurred at ∼2.58 Ma, with loess/paleosol displaying δ⁴¹K values (-0.41 ‰ to -0.63 ‰) lower than the bulk-silicate-earth-like Red Clay values (-0.35 ‰ to -0.45 ‰). Furthermore, The δ⁴¹K values of eolian deposits are negatively correlated with the Na₂O/K₂O and Na₂O/Al₂O₃ ratios, with negligible influence from different grain size fraction. These observations indicate that the δ⁴¹K values are not controlled by post-depositional weathering at the CLP, but rather by an increased export of weathered detritus or recycled sediments from the Northeastern Tibetan Plateau, as revealed by K isotope surveys of potential source materials and Earth system model simulations. Our results further suggest that the intensified global cooling during the Quaternary promoted greater sediments erosion and altered the dynamics of the westerlies and the Siberian High, with important implications for understanding the paleoenvironment changes and reconstruction of the East Asian atmospheric circulation across the Pliocene-Pleistocene boundary.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"668 ","pages":"Article 119543"},"PeriodicalIF":4.8,"publicationDate":"2025-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144665890","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":"Organic carbon, sea level and carbonate weathering controls on marine carbon isotope perturbations across the Hirnantian glaciation","authors":"Jiaqiang Zhang ,&nbsp;Zhen Qiu ,&nbsp;Wenjiao Xiao ,&nbsp;Paul B. Wignall ,&nbsp;Weiliang Kong ,&nbsp;Benjamin J.W. Mills ,&nbsp;Yijun Xiong ,&nbsp;Simon W. Poulton","doi":"10.1016/j.epsl.2025.119539","DOIUrl":"10.1016/j.epsl.2025.119539","url":null,"abstract":"<div><div>The Hirnantian isotopic carbon excursion (HICE) records a dramatic perturbation to the global carbon cycle across the Late Ordovician Hirnantian glaciation. The HICE is characterized by variable duration and amplitude in global records, but its ultimate driver, and controls on the observed variability, are poorly understood. Here, we present a comprehensive compilation of geochemical data and paired carbon and calcium isotope records for two continuous Hirnantian sections at Wanhe and Shuanghe on the Yangtze Shelf (South China). Our results reveal a lateral gradient of up to 4 ‰ in organic carbon isotope (δ¹³C_org) values across the shelf, decreasing from nearshore to offshore. Carbonate carbon isotope (δ¹³C_carb) data from the Wanhe and Shuanghe sections also show pronounced variability, which cannot be fully explained by primary mineralogical changes or early marine diagenesis. We therefore interpret the spatial δ¹³C_org patterns as reflecting, at least in part, shelf-scale heterogeneity in seawater dissolved inorganic carbon isotope (δ¹³C_DIC) values. Our compilation further suggests that substantial organic carbon burial likely triggered the HICE, while sea-level change subsequently drove the asynchronous, spatially heterogeneous changes in seawater δ¹³C_DIC values. Additionally, enhanced carbonate weathering, linked to falling syn-glacial sea-level, amplified the spatial heterogeneity in regional marine δ¹³C_DIC values. Moderate δ¹³C_org changes (&lt;+2 ‰) are observed in central shelf areas across the Hirnantian glaciation, suggesting that the global carbon cycle perturbations during this ice age were of more modest amplitude than often suggested.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"667 ","pages":"Article 119539"},"PeriodicalIF":4.8,"publicationDate":"2025-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144633752","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":"Deep carbon sink in the East Asian mantle and its impact on atmospheric CO2 drawdown since the Cretaceous","authors":"Chun Yang ,&nbsp;Sheng-Ao Liu ,&nbsp;Hong-Yan Li ,&nbsp;Yi-Gang Xu","doi":"10.1016/j.epsl.2025.119541","DOIUrl":"10.1016/j.epsl.2025.119541","url":null,"abstract":"<div><div>The western Pacific oceanic slab has been deeply subducted into the mantle beneath East Asia since the early Cretaceous, eventually stagnating within the mantle transition zone (410–660 km). Here we present the first quantitative estimate of the flux of deeply subducted carbon beneath East Asia related to the Pacific slab and evaluate its impact on atmospheric CO₂ levels (<em>p</em>CO₂) since the Cretaceous. We compiled chemical and zinc isotopic data for the widely distributed East Asian intercontinental basalts (EAIBs; <em>N</em> = 399), which originated from partial melting of the upper mantle above the stagnated western Pacific slab. By using a melt CO₂ degassing correction and a \"melting-mixing\" model, we show that the formation of EAIBs involved ubiquitous magma mixing between silicate melts and carbon-rich melts. Consequently, the mantle source of EAIBs is estimated to have an unexpectedly high carbon content (297 ± 118 μg/g; 1σ), about three times the average carbon in the convecting mantle (110 ± 40 μg/g), primarily due to subducting carbon input from the western Pacific slab. Based on paleogeographic reconstruction models, we show that two peak periods of subducting carbon influx into the mantle transition zone sparked the deep carbon sink beneath East Asia. There is a gap of approximately 26 Ma between peak carbon subduction and widespread EAIB eruptions. This gap suggests that deep carbon sink beneath East Asia, due to inefficient mantle carbon outgassing, may have significantly contributed to the drawdown of atmospheric <em>p</em>CO₂ since the Cretaceous.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"667 ","pages":"Article 119541"},"PeriodicalIF":4.8,"publicationDate":"2025-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144655713","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 evolution of planetesimal reservoirs revealed by Fe-Ni isotope anomalies in differentiated meteorites","authors":"Fridolin Spitzer ,&nbsp;Timo Hopp ,&nbsp;Christoph Burkhardt ,&nbsp;Nicolas Dauphas ,&nbsp;Thorsten Kleine","doi":"10.1016/j.epsl.2025.119530","DOIUrl":"10.1016/j.epsl.2025.119530","url":null,"abstract":"<div><div>Differentiated meteorites sample planetesimals formed earlier than the parent bodies of chondritic meteorites. To evaluate whether these two generations of planetesimals formed from the same or distinct materials, we have analyzed the Fe and Ni isotopic compositions for a large set of differentiated meteorites, representing approximately 26 distinct parent bodies. Most of these samples are genetically related to the carbonaceous chondrite (CC)-type reservoir, which is thought to represent some portion of the outer disk. The new data reveal that early and late CC planetesimals cover a similar range of Fe and Ni isotopic compositions, indicating that all these bodies accreted from the same mixture of dust components, either in a long-lived pressure structure of the disk or in different substructures containing the same materials. Many differentiated meteorites have an isotopic composition similar to the late-formed CR chondrites, indicating that the CR chondrite reservoir was established early and remained isolated for essentially the entire disk lifetime. Finally, CI chondrites are the only CC chondrites whose isotopic composition is not represented among differentiated meteorites. Thus, planetesimals with CI chondrite-like isotopic compositions represent a late burst of planetesimal formation and possibly formed by a distinct mechanism and/ or in a different location from the other CC planetesimals.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"667 ","pages":"Article 119530"},"PeriodicalIF":4.8,"publicationDate":"2025-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144623660","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":"Hybrid mantle plumes with recycled and primordial nitrogen: Insights from plume-influenced basaltic glasses from Reykjanes Ridge and Rochambeau Bank","authors":"Kan Li ,&nbsp;Michael R. Hudak ,&nbsp;Michael W. Broadley ,&nbsp;Molly K. Anderson ,&nbsp;David V. Bekaert ,&nbsp;John A. Krantz ,&nbsp;Namitha Kumar ,&nbsp;Manuel Pimenta Silva ,&nbsp;Doshik Hahm ,&nbsp;Joshua M. Curtice ,&nbsp;Mark D. Kurz ,&nbsp;Peter H. Barry","doi":"10.1016/j.epsl.2025.119538","DOIUrl":"10.1016/j.epsl.2025.119538","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Sources of nitrogen (N) in the plume mantle source remains hotly debated between a primordial origin (i.e., acquired during Earth’s formation) and a recycled origin associated with subduction of surficial material. Although N isotope data for plume-derived magmas are limited, the available data show clear differences in N isotope compositions between plume (δ&lt;sup&gt;15&lt;/sup&gt;N &gt;-2 ‰) and the depleted mid-ocean-ridge basalt mantle sources (i.e., DMM; δ&lt;sup&gt;15&lt;/sup&gt;N = -5 ± 2 ‰). Here we present N-isotope and noble gas isotope data from two suites of well-characterized plume-influenced submarine basaltic glasses with high &lt;sup&gt;3&lt;/sup&gt;He/&lt;sup&gt;4&lt;/sup&gt;He: 1) the Rochambeau Bank in the northeastern Lau backarc basin (up to ∼23 R&lt;sub&gt;A&lt;/sub&gt;, where R&lt;sub&gt;A&lt;/sub&gt; refers to the atmospheric &lt;sup&gt;3&lt;/sup&gt;He/&lt;sup&gt;4&lt;/sup&gt;He ratio), and 2) the Reykjanes Ridge (up to ∼18 R&lt;sub&gt;A&lt;/sub&gt;) south of Iceland. These sample suites are associated with different tectonic settings: the Tonga subducting slab interacts with the Samoan plume beneath the Lau backarc basin, whereas the Mid-Atlantic Ridge interacts with the Icelandic plume at the Reykjanes Ridge. The contrasting tectonic settings provide a unique opportunity to decipher both the origin of N in plume mantle sources and the interaction of the plume mantle with other mantle components, including recycled material from subducting slabs and the DMM. Our results show that Rochambeau Bank (δ&lt;sup&gt;15&lt;/sup&gt;N from +1.3 ‰ to +2.8 ‰) and Reykjanes Ridge samples (δ&lt;sup&gt;15&lt;/sup&gt;N from -2.3 ‰ to +0.1 ‰) are both characterized by δ&lt;sup&gt;15&lt;/sup&gt;N values that are enriched relative to the DMM. Rochambeau Bank data are consistent with ternary mixing between the DMM (δ&lt;sup&gt;15&lt;/sup&gt;N = -5 ± 2 ‰; N&lt;sub&gt;2&lt;/sub&gt;/&lt;sup&gt;3&lt;/sup&gt;He = 3.7 ± 1.2 × 10&lt;sup&gt;6&lt;/sup&gt;; N&lt;sub&gt;2&lt;/sub&gt;/&lt;sup&gt;40&lt;/sup&gt;Ar* = 138±65), a subduction component from the adjacent Tonga slab with recycled N (δ&lt;sup&gt;15&lt;/sup&gt;N = ∼+3 ‰; N&lt;sub&gt;2&lt;/sub&gt;/&lt;sup&gt;3&lt;/sup&gt;He = ∼10&lt;sup&gt;9&lt;/sup&gt;; N&lt;sub&gt;2&lt;/sub&gt;/&lt;sup&gt;40&lt;/sup&gt;Ar* = ∼5 × 10&lt;sup&gt;6&lt;/sup&gt;), and a third component with δ&lt;sup&gt;15&lt;/sup&gt;N = ∼0 ‰, N&lt;sub&gt;2&lt;/sub&gt;/&lt;sup&gt;3&lt;/sup&gt;He = ∼2 × 10&lt;sup&gt;5&lt;/sup&gt; and N&lt;sub&gt;2&lt;/sub&gt;/&lt;sup&gt;40&lt;/sup&gt;Ar* = ∼40, which we attribute to the Samoan plume component enriched in primordial N. In contrast, Reykjanes Ridge data, combined with Iceland data, are consistent with ternary mixing among the DMM, plume components with recycled N (δ&lt;sup&gt;15&lt;/sup&gt;N from 0 ‰ to +6 ‰; N&lt;sub&gt;2&lt;/sub&gt;/&lt;sup&gt;3&lt;/sup&gt;He = ∼10&lt;sup&gt;9&lt;/sup&gt;; N&lt;sub&gt;2&lt;/sub&gt;/&lt;sup&gt;40&lt;/sup&gt;Ar* = ∼5 × 10&lt;sup&gt;6&lt;/sup&gt;) and primordial N (δ&lt;sup&gt;15&lt;/sup&gt;N from -2 ‰ to +2 ‰; N&lt;sub&gt;2&lt;/sub&gt;/&lt;sup&gt;3&lt;/sup&gt;He = ∼2 × 10&lt;sup&gt;5&lt;/sup&gt;; N&lt;sub&gt;2&lt;/sub&gt;/&lt;sup&gt;40&lt;/sup&gt;Ar* = ∼40) endmembers in deep Icelandic mantle plumes. This is consistent with the presence of both recycled and primordial N being intrinsic to the Icelandic mantle plume. By integrating N data from other global plume-influenced samples (i.e., Society, Hawaii, and Central Indian Ridge), we show that the global dataset i","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"667 ","pages":"Article 119538"},"PeriodicalIF":4.8,"publicationDate":"2025-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144605935","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":"Surface airflow patterns at a barchan dune field in Hellespontus Montes, Mars","authors":"Richard Love ,&nbsp;Derek W.T. Jackson ,&nbsp;Thomas A.G. Smyth ,&nbsp;Andrew Cooper ,&nbsp;Timothy Michaels ,&nbsp;Jean-Philippe Avouac","doi":"10.1016/j.epsl.2025.119536","DOIUrl":"10.1016/j.epsl.2025.119536","url":null,"abstract":"<div><div>Mobile barchan dunes are well-developed in a crater in the Hellespontus Montes region on Mars. Previous studies of their temporal evolution show that the barchans maintain their shape and migrate in a uniform pattern. Whereas barchans are typically associated with unidirectional wind regimes, the crater experiences seasonal changes in wind regime, driven by large-scale circulation patterns. Using a multi-scale modelling approach we demonstrate that the effect of upwind mesas are minimal to steering regional wind conditions, beyond the extent of the mesas themselves which limits the effect on the development and maintenance of barchan dunes further downwind. The results of high resolution CFD modelling showed individual barchan dunes had the capability to locally steer oblique wind flows along the orientation of the barchan dunes. We hypothesise that this ability of barchan dunes to ‘steer’ near surface local wind flows, combined with the uni-directional source of sediment at the site allows barchan morphology to persist in Hellespontus Montes, despite being subject to a range of incident wind directions.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"667 ","pages":"Article 119536"},"PeriodicalIF":4.8,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144596777","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":"Serpentinite dehydration-driven redox heterogeneity in cold subduction zone magmas","authors":"Zuxing Chen ,&nbsp;Fang-Zhen Teng ,&nbsp;Yuxiang Zhang ,&nbsp;Liping Qin ,&nbsp;Jinjing Huo ,&nbsp;Robert J. Stern ,&nbsp;Jia Liu ,&nbsp;Jing Lei ,&nbsp;Zhigang Zeng","doi":"10.1016/j.epsl.2025.119537","DOIUrl":"10.1016/j.epsl.2025.119537","url":null,"abstract":"<div><div>Serpentinite-derived slab fluids likely control the oxidation state of the sub-arc mantle, yet their oxidation state remains controversial. To address this issue, we report the first set of redox-sensitive chromium isotopic data for arc and back-arc basin lavas. Samples from the Mariana Arc and eastern Manus Basin have heavier Cr isotopic compositions (δ⁵³Cr = −0.13 to −0.18 ‰) than the MORB-like δ⁵³Cr values in the Mariana back-arc basin (−0.21 to −0.31 ‰). The δ⁵³Cr values correlate with Ba/La and V/Yb ratios, suggesting the control of slab-derived fluids on across-arc Cr isotope and oxygen fugacity variations. The Cr⁶⁺-bearing oxidized alkaline fluids released by serpentinite dehydration at sub-arc depths are enriched in heavy Cr isotopes. Their infiltration and reactions with the overlying mantle wedge facilitate the sub-arc oxidation of Fe²⁺ to Fe³⁺ and Cr²⁺ to Cr³⁺, resulting in heavy Cr isotopes and high oxygen fugacity in arc magmas. Oxidized fluids diminish beyond sub-arc depths due to the complete breakdown of antigorite, thus back-arc basin basalts have MORB-like δ⁵³Cr values and low oxygen fugacity. Our study suggests that Cr isotopes can provide critical insights into the role of serpentinite-derived fluids in redox heterogeneity in subduction-related magmas.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"667 ","pages":"Article 119537"},"PeriodicalIF":4.8,"publicationDate":"2025-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144587578","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":"Sedimentary mercury cycling in recent upwelling systems","authors":"Philipp Böning ,&nbsp;Frederik Gäng ,&nbsp;Katharina Pahnke ,&nbsp;Olaf Dellwig","doi":"10.1016/j.epsl.2025.119534","DOIUrl":"10.1016/j.epsl.2025.119534","url":null,"abstract":"<div><div>Mercury (Hg) is a prime indicator of anthropogenic perturbations yet the database of Hg in modern upwelling sediments from the Humboldt and Benguela current systems is sparse. Mercury has natural and anthropogenic sources, occurs in different species, and recycling processes before final burial complicates the interpretation of Hg accumulation.</div><div>Here, we present data of total Hg along with Al, Zr, organic carbon and Pb (a more straightforward and well-studied anthropogenic indicator) for ²¹⁰Pb-dated sediments from Peru, Chile and Namibia from within and below their respective oxygen minimum zones (OMZs). Almost all sediments exhibit upcore enrichments of Hg in the upper ∼ 30 cm suggesting an anthropogenic source for Hg, similar to Pb. Peak Hg enrichments are highest off Peru (800 µg kg^-1) in the early 1980s followed by less pronounced maxima off Chile (150 µg kg^-1) and Namibia (80 µg kg^-1). This difference is likely due to a high number of industrial and pre-industrial mining sites in Peru, which is less important in Chile and essentially missing in Namibia. Mercury also accumulates in sediments below OMZs supporting previous indications of abyssal Hg exports while Pb only accumulates in OMZ sediments.</div><div>Mercury enrichments in Peruvian sediments that have negligible excess Pb contents suggest metallurgic Hg inputs since pre-industrial times (before CE 1900). By contrast, anthropogenic Hg is detectable at one coastal Namibian site, while Hg in the other Namibian sediments may be natural rather than anthropogenic. Our data suggest that both environments within and below recent OMZs are Hg accumulation hotspots.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"667 ","pages":"Article 119534"},"PeriodicalIF":4.8,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144570983","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":"Electrical breakdown products of SO2 in CO2 and N2 mixtures and the implication to the mysterious UV absorber in Venus's atmosphere","authors":"Quincy H.K. Qu ,&nbsp;Alian Wang ,&nbsp;E. Thimsen ,&nbsp;Z.C. Ling","doi":"10.1016/j.epsl.2025.119535","DOIUrl":"10.1016/j.epsl.2025.119535","url":null,"abstract":"<div><div>Sulfur-containing species are suggested as the UV-absorbers in Venus’s atmosphere, which can be generated by photochemistry or electrochemistry. Here we report an electrical discharge experiment in gas mixtures of SO₂ with CO₂ and N₂, under the pressure and temperature conditions relevant to the Venus cloud layer. We directly observed the primary breakdown products of SO₂ as free radicals SO*, S_I*, S_II*, S₂*, O_I*, O_II* using plasma spectroscopy; and the stable ending products as S₈ particles and H₂SO₄ droplets using Raman spectroscopy. Their co-exhibitions after a few minutes of electrical discharge imply the formation of short-lived intermediate phases (from the radicals as precursors), including polysulfur and sulfur-oxides, both are recognized candidates for the mysterious UV-absorber. The simultaneous observations of plasma lines of SO*<span><math><mspace></mspace></math></span>and S₂* under all experimental conditions suggest that the two major breakdown paths of SO₂, which require similar electron energy, are likely to occur simultaneously. In Venus’s cloud layer where electric activity may occur, the high breakdown rate of SO₂ by glow-to-arc electric discharge would generate various S-bearing radicals with very high transient density regionally, ∼3 orders of magnitude higher than the global mixing ratio of similar species from photochemistry. The high density of reactive S-species from regional electrochemistry could be responsible for the inhomogeneous distribution and temporal changes of dark features in Venus UV images.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"667 ","pages":"Article 119535"},"PeriodicalIF":4.8,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144570806","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":"CO2 flushing and redox as drivers of pre-eruptive amphibole breakdown","authors":"Paul A. Wallace ,&nbsp;Sarah H. De Angelis ,&nbsp;Jessica Larsen ,&nbsp;Luca Caricchi ,&nbsp;Jackie E. Kendrick ,&nbsp;Yan Lavallée","doi":"10.1016/j.epsl.2025.119532","DOIUrl":"10.1016/j.epsl.2025.119532","url":null,"abstract":"<div><div>Amphibole reaction rims record critical pre-eruptive magmatic processes, including storage and ascent dynamics. Although decompression and heating are traditionally viewed as key triggers for amphibole breakdown, variations in rim textures and mineralogy indicate that multiple or fluctuating processes often operate simultaneously. This study presents experimental results demonstrating significant impacts of CO₂ flushing and redox (<em>f</em>O₂) conditions (versus heating and decompression) on amphibole reaction rim formation in rhyolitic and rhyodacitic melts at shallow crustal conditions. In experiments at 830 °C and 120 MPa, the presence of a mixed XH₂O:XCO₂ fluid (XCO₂ = 0.3–0.7) rapidly induced a reaction, with rim thickness, grain size, aspect ratio, nucleation rate and crystal number density all increasing with CO₂ concentration. In contrast, rims produced by heating (880 °C for up to 48 h) had distinct characteristics, while decompression (120 MPa to 65 MPa over 120 h) from the same starting conditions did not produce reaction rims. Increasing oxygen fugacity (<em>f</em>O₂ from NNO+1 to RRO [NNO+2]) led to rapid rim formation within 24 h, accompanied by distinct mineralogical changes that favoured the stability of Fe³⁺ phases. These findings demonstrate that CO₂, <em>f</em>O₂, heating and decompression each exert unique influences on amphibole breakdown; thus, quantitative textural analysis of amphibole rims can help differentiate the driving mechanisms. Recognising the full range of factors affecting amphibole stability and an understanding of the multi-parametric controls is essential for accurately interpreting pre-eruptive conditions, enhancing our ability to reconstruct magmatic histories, and for assessing volcanic hazards.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"667 ","pages":"Article 119532"},"PeriodicalIF":4.8,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144557374","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}