Earth and Planetary Science Letters最新文献

{"title":"Wetted two-grain boundaries in olivine aggregates and seismic velocities in the oceanic upper mantle","authors":"Andrew J. Berry ,&nbsp;Ulrich H. Faul ,&nbsp;Qiheng Yang ,&nbsp;Harri Kokkonen ,&nbsp;Andrew M. Kingston ,&nbsp;Ajay Limaye ,&nbsp;Martin D. de Jonge","doi":"10.1016/j.epsl.2024.119119","DOIUrl":"10.1016/j.epsl.2024.119119","url":null,"abstract":"<div><div>The distribution of basaltic melt between crystals of olivine (Mg_1.8Fe_0.2SiO₄), after equilibration at 1350 °C and 1 GPa for up to 14 days, was investigated by fluorescence tomography. The system is an analogue for low-degree partial melts in the Earth's upper mantle, the connectivity of which controls the rate at which magmas are transported from the source to the surface by porous flow. In fluorescence tomography the distribution of an incompatible element that partitions almost exclusively into the melt can be used to map the distribution of melt. We chose to use Nb (0.7 wt%) because of its high incompatibility and the high energy of its Kα fluorescence, which allowed samples with a thickness of up to 300 μm to be studied. The tomographic reconstructions showed not only melt pockets at four-grain corners and melt channels on three-grain edges, as predicted, but also melt sheets corresponding to wetted two-grain boundaries. The spatial resolution of the method is controlled by the size of the excitation beam (in this case 2–3 μm), but smaller features can be observed and their thickness inferred from the intensity of the fluorescence signal. The melt sheets identified have a thickness of ∼0.5 μm, but there is also evidence for thinner sheets. Better resolution of thin sheets could be achieved by increasing the concentration of Nb in the melt. Fluorescence tomography is an ideal approach for determining the distribution of melt at low melt fractions since only the melt is imaged. The speed of data acquisition opens up the possibility of systematically studying the evolution of melt connectivity as a function of melt fraction. A melt distribution that includes wetted two-grain boundaries has a lower permeability and would be more visible seismically than the expected tubule geometry. The presence of melt can hence explain the significant drop in seismic velocity observed in the oceanic upper mantle.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119119"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158930","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":"Insight into climate and hydrology of the late cretaceous western interior basin from clumped isotope Paleothermometry and strontium isotopes","authors":"Allison N. Curley ,&nbsp;Sierra V. Petersen ,&nbsp;Henry Fricke ,&nbsp;James Gleason","doi":"10.1016/j.epsl.2024.119180","DOIUrl":"10.1016/j.epsl.2024.119180","url":null,"abstract":"<div><div>High sea levels in the Late Cretaceous led to the formation of vast seaways on every continent. These shallow seaways are without modern analogs and many fundamental aspects of their oceanography are poorly understood. In the Campanian (∼83–72 Ma), the Western Interior Seaway (WIS) of North America linked the proto-Gulf of Mexico and Arctic Ocean. Given its shallow depth, freshwater inputs to the WIS could have had a greater influence on conditions in the seaway compared to a deeper ocean and would have become increasingly important as the WIS regressed through the Maastrichtian. The isotopic composition of mollusk shells in freshwater facies can help constrain the composition and temperature of these inputs, improving our understanding of surface temperature, hydrological dynamics, and paleoelevation. Here we measure Δ₄₇ temperature, δ¹⁸O_water, and ⁸⁷Sr/⁸⁶Sr in late Campanian (∼75 Ma) unionid bivalve shells from fluvial and pond deposits near the western shore of the WIS (∼42°N-56°N). Sample mean surface water temperatures spanned 22–44 °C, with a mean of 30 ± 2.7 °C. The latitudinal temperature gradient across this region is reduced compared to today, at ∼7 °C across these 14° of latitude based on stream sample means. These temperatures are outside the optimal growth conditions of modern unionids in North America, indicating a shift in niche. Following this finding, we recalculate δ¹⁸O_water values from previously published δ¹⁸O_carb values using new Δ₄₇ temperatures instead of assumed growth temperatures. Our findings support previous observations of a bimodal distribution in freshwater δ¹⁸O_water values in this region although the absolute values shift higher. Spatial patterns of δ¹⁸O_water are consistent with a Campanian Proto-North American Monsoon and the lowest δ¹⁸O_water values we report are consistent with paleoelevation of &gt;3500 m in the Proto-Cordillera. ⁸⁷Sr/⁸⁶Sr values broadly align with different facies, with more radiogenic values occurring in major trunk rivers draining the highlands and less radiogenic values in streams recharged by low-elevation precipitation. Predominance of a ⁸⁷Sr/⁸⁶Sr signature consistent with weathering Paleozoic carbonates could be consistent with seasonal increases in rock weathering associated with a monsoon.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119180"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158956","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":"High-resolution seismic tomography of the transition zone from normal to flat slab subduction in central Chile: Implications for volcanoes, plate coupling and flat subduction","authors":"Lei Gao ,&nbsp;Zixin Chen ,&nbsp;Ying Liu ,&nbsp;Haijiang Zhang ,&nbsp;Jiashun Hu ,&nbsp;Diana Comte ,&nbsp;Francisco Hernán Ortega Culaciati","doi":"10.1016/j.epsl.2024.119167","DOIUrl":"10.1016/j.epsl.2024.119167","url":null,"abstract":"<div><div>To better understand factors controlling the distribution of volcanoes, plate coupling along the subducting plate interface, and the transition from normal to flat slab subduction, we have determined high-resolution Vp, Vs and Vp/Vs models in the central Chile subduction zone where normal slab subduction transits to flat slab subduction. In the study region spanning latitudes of 22° to 31°S, volcanoes to the north of latitude 25.5°S are underlaid by intensive intermediate-depth earthquakes, but those to the south are correlated with very few. Based on velocity features, we proposed that volcanoes to the north are likely caused by partial melting of mantle wedge by incorporation of fluids released during the dehydration reactions of various hydrous minerals in the slab that are responsible for inducing intermediate-depth earthquakes, while volcanoes to the south are likely caused by sub-slab hot materials migrating upwards through the tear or gap due to the transition from normal subduction to flat subduction. Along the plate surface constructed based on our inverted velocity models and relocated earthquakes, higher plate coupling is spatially correlated with lower Vp/Vs values and fewer earthquakes, whereas lower plate coupling is correlated with relatively higher Vp/Vs values and intensive small earthquakes. These features suggest that the plate coupling state is controlled by the existence of fluids along the plate interface, with high degree of fluids reducing plate coupling and causing the creep deformation. In the region where the flat slab subduction is evident, there exist apparent high velocity anomalies above the intraslab seismicity. This indicates that some buoyant materials such as oceanic plateaus, aseismic ridges and seamount chains that featured high velocity anomalies were subducted with the slab and caused the nominal flat subduction.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119167"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143157730","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":"Mantle induced hydration and oxidation of intracontinental granite sources in the North China Craton","authors":"Chuan-Mao Yang ,&nbsp;Yi-Gang Xu ,&nbsp;Xiao-Ping Xia ,&nbsp;Jin-Hui Yang ,&nbsp;Xiao-Long Huang ,&nbsp;Christopher J. Spencer ,&nbsp;Jin-Feng Sun ,&nbsp;Ze-Xian Cui ,&nbsp;Meng-Jing Li ,&nbsp;Wan-Feng Zhang ,&nbsp;Qing Yang","doi":"10.1016/j.epsl.2024.119177","DOIUrl":"10.1016/j.epsl.2024.119177","url":null,"abstract":"<div><div>Arc magmatism is typically highly oxidized, due to the influx of oxidizing aqueous fluids released from the subducting plate. The observation that some intracontinental A- and I-type granites also exhibit high oxidation presents a significant challenge in igneous petrology and geodynamics. This is particularly true for regions such as the North China Craton (NCC), situated over 1000 km from the trench. In this study, we measured water content, oxygen fugacity (<span><math><mrow><mi>f</mi><msub><mi>O</mi><mn>2</mn></msub></mrow></math></span>), and O-Hf isotopes in zircons from the late Mesozoic granites from the NCC. The results reveal positive correlations between water content and <span><math><mrow><mi>f</mi><msub><mi>O</mi><mn>2</mn></msub></mrow></math></span>, and between water content and <span><math><mrow><msub><mrow><mi>ε</mi></mrow><mtext>Hf</mtext></msub><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow></mrow></math></span>, indicating the predominant control of primary magma composition, rather than magmatic differentiation, on water content and <span><math><mrow><mi>f</mi><msub><mi>O</mi><mn>2</mn></msub></mrow></math></span> of zircon. The Early Cretaceous A-type and I-type granites, which involved greater amount of mantle-derived melts, exhibit more elevated water, Nb, Ta, and <span><math><mrow><mi>f</mi><msub><mi>O</mi><mn>2</mn></msub></mrow></math></span> than the Jurassic granites. This suggests that the hydration and oxidization of intracontinental granitoids of the NCC are strongly influenced by the ingress of mantle-derived oxidized hydrous melts/aqueous fluids to the granitoid source, which were likely released from the Paleo-Pacific plate at a greater depth than the sub-arc mantle. The proposed model involves significant water in intracontinental crustal melting, thereby challenging the paradigm of intraplate A- and I-type granite genesis and shedding light on the crustal and mantle processes during cratonic destruction.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119177"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143157732","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":"Unity of terrestrial and extraterrestrial soils in granular configuration","authors":"Jun Zhang ,&nbsp;Yong Li ,&nbsp;Yifei Cui ,&nbsp;Zi Wu ,&nbsp;Yuan Xue ,&nbsp;Jianyi Cheng ,&nbsp;Hu Jiang ,&nbsp;Yao Li ,&nbsp;Jian Guo ,&nbsp;Jiayan Nie ,&nbsp;Guodong Wang ,&nbsp;Ao Luo","doi":"10.1016/j.epsl.2025.119239","DOIUrl":"10.1016/j.epsl.2025.119239","url":null,"abstract":"<div><div>Grain size distribution (GSD) is crucial for understanding soil properties and surface processes. We find that both terrestrial soils and lunar soils are subjected to a unified GSD function, <em>P</em>(<em>D</em>)= <em>g</em>(<em>μ</em>)<em>D^-μ</em>exp(-<em>D/D</em>_c), reducing the textural fractions and grade modes to a parameter pair (<em>μ, D</em>_c), which unifies terrestrial and extraterrestrial soils in granular configuration, beyond the environments and mechanisms of soil genesis. To construct a framework of the soil formation, we generalize the textural composition to a grade space representing the granular configuration, and conceptualize soil genesis as the random aggregation of the fractal fragmentation of parent lithospheric material and fragments from other sources (e.g., meteorites impacts or surface transport processes). Random simulation reproduces the multiple grade modes observed in soils, and spontaneously derives the unified GSD function. Then we numerically generate the (<em>μ, D</em>_c)-fields for soils on earth and moon, which refine the digital data mapping based on site measurements and depict the local fluctuation of soil parameters. The GSD unity also provides a tool of generating “numerical simulants” of lunar soils to fill the gap in material simulants. The study leads to a GSD-paradigm (in contrast to the conventional landscape-paradigm) in soil study, which is expected to facilitate the data harmonization on earth and promote the generation of lunar regolith data in favor of the in-situ resource utilization and base construction on moon.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"654 ","pages":"Article 119239"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143300332","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":"Hydrologically-induced crustal stress changes and their association with seismicity rates in Taiwan","authors":"Ya-Ju Hsu ,&nbsp;Roland Bürgmann ,&nbsp;Zhongshan Jiang ,&nbsp;Chi-Hsien Tang ,&nbsp;Christopher W. Johnson ,&nbsp;Da-Yi Chen ,&nbsp;Hsin-Hua Huang ,&nbsp;Miao Tang ,&nbsp;Xinghai Yang","doi":"10.1016/j.epsl.2024.119181","DOIUrl":"10.1016/j.epsl.2024.119181","url":null,"abstract":"<div><div>Studying crustal stress changes associated with hydrological cycles and their influence on seismicity rate illuminates the complex interplay between crustal stress conditions, faulting orientations, and earthquake nucleation. By analyzing GNSS position time series in 2006–2021 across Taiwan, we reveal a prevailing NW-SE trending seasonal contraction and expansion of the Earth's crust in response to hydrological loading and unloading in SW Taiwan, consistent with the maximum annual water storage change inferred from hydrological data. Inspection of seismicity rates in SW Taiwan indicates a positive correlation between excess seismicity rate and reduced NW-SE compression and/or decreasing vertical loading. Though hydrologically-induced contraction aligns with the tectonic compressive stress axis in the wet season, this alignment does not lead to more frequent earthquakes during peak water storage. Instead, seismicity peaks during the dry months, coinciding with maximum uplift and water unloading. This suggests that hydrologically-induced vertical stress or pressure changes play the dominant role in triggering earthquakes, as evidenced by vertical stress amplitudes 2∼4 times greater than the horizontal stress changes. The statistical correlation evaluating the timing of earthquakes and hydrologically-induced stress changes further affirms that the seismicity rate increases with reduced tectonic compression and enhanced vertical unloading in SW Taiwan. The observed relationship also implies the earthquake nucleation time is comparable to the stressing period of annual water cycles in SW Taiwan. Hydrologically-triggered earthquakes appear to be more sensitive to pressure variations than to shear stress changes, similar to tidally-modulated seismicity.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119181"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158957","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":"How does the newly-formed drainage divide migrate after a river capture event?","authors":"Shuang Bian ,&nbsp;Xibin Tan ,&nbsp;Andrew V. Zuza ,&nbsp;Chao Zhou ,&nbsp;Feng Shi ,&nbsp;Yiduo Liu ,&nbsp;Junfeng Gong","doi":"10.1016/j.epsl.2024.119165","DOIUrl":"10.1016/j.epsl.2024.119165","url":null,"abstract":"<div><div>Tectonic and climatic perturbations can drive drainage adjustment. A river capture event is usually a landmark shift in drainage evolution, which significantly changes the river network topology. Although these events can be identified through field observations and provenance analysis, reconstructing this evolution and pinpointing the capture timing remain challenging. Here, we provide a new way of determining capture timing via drainage divides, based on theory, numerical simulations, and two natural cases. Our theoretical studies show that the steady-state elevation of the captor and beheaded rivers will decrease and increase following a capture event, respectively. The newly-formed drainage divide that emerged between the beheaded river and capture point will have large cross-divide differences in steady-state elevation and erosion rate and thus migrates towards the beheaded-river side until reaching a new steady state (no cross-divide difference in steady-state elevation). Numerical simulations reproduce the characteristic phenomena of drainage-divide migration following capture events. We find that (1) the migration of newly-formed drainage divides after capture events may last for tens of millions of years, with the migration rate decreasing exponentially over time; (2) a larger captured area, higher uplift rate, or lower erosion coefficient may cause higher migration rate of the newly-formed drainage divide in the other same conditions. These insights from theoretical analysis and numerical simulations are further applied to the Dadu-Anning and Yarlung-Yigong capture events in the southeastern Tibet. We predict that the present Dadu-Anning drainage divide would further migrate ∼94–123 km southward to reach a steady state in tens of millions of years. The Yarlung-Yigong capture event occurred earlier, in the early-middle Cenozoic, because the newly-formed drainage divide has already reached a steady state.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119165"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143157734","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":"Cadmium isotopes as a tracer for deep carbon recycling","authors":"Sheng-Ao Liu,&nbsp;Tianhao Wu,&nbsp;Ziteng Wang,&nbsp;Dandan Li,&nbsp;Kexin Song","doi":"10.1016/j.epsl.2024.119168","DOIUrl":"10.1016/j.epsl.2024.119168","url":null,"abstract":"<div><div>Global marine carbonates have cadmium (Cd) concentrations much higher than those of mantle peridotites, and especially, Phanerozoic carbonates are uniquely characterized by heavier Cd isotopic composition (expressed as δ^114/110Cd against NIST 3108) relative to the mantle. These characteristics make the Cd systematics potentially useful for tracing recycled carbonates in the mantle. We test the feasibility of this application through analyses of seventeen well-characterized Cenozoic intraplate basalts from Eastern China, and for comparison, six mid-ocean ridge basalts (MORB) are also investigated. The MORB have a mean δ^114/110Cd value of 0.13 ± 0.04 ‰ (2sd), in accord with previous analyses for other MORB, illustrating a relatively homogeneous Cd isotopic composition of global MORB and the depleted upper mantle. The Eastern China basalts have δ^114/110Cd values varying between 0.17 ± 0.05 ‰ (2sd) and 0.65 ± 0.05 ‰ (2sd), which are slightly to notably higher than those of the mantle and MORB. The maximum δ^114/110Cd offset (∼0.5–0.6 ‰) between these basalts and the mantle fairly exceeds the magnitude of Cd isotope fractionation even at low degrees of partial melting. The high δ^114/110Cd values cannot also be explained by volatilization-induced Cd loss, given the positive correlation between δ^114/110Cd and Cd concentrations. Instead, this correlation points to a key role of recycled carbonates, supported by the “carbonated” geochemical signals of these basalts (e.g., low Ti/Eu ratios). Binary mixing model indicates that recycling of approximately 2–10 % carbonates into sources can explain the high δ^114/110Cd observed in these basalts. Given that Cd is a trace element in the mantle (∼38 ng/g), the Cd isotopic composition of mantle rocks is sensitive to even a tiny amount of recycled carbonates. Therefore, we propose for the first time that Cd isotopes are a new and powerful tool of tracing Earth's deep carbon recycling over geologic time.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119168"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158120","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":"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}