Earth and Planetary Science Letters最新文献_第7页

Mantle flow and deformation of the eastern Adria subduction: New insights from AdriaArray seismic anisotropy 东亚德里亚俯冲的地幔流动和变形：来自AdriaArray地震各向异性的新认识

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-22 DOI: 10.1016/j.epsl.2025.119793

Laura Petrescu , Felix Borleanu , Samuel Celis , Dániel Kalmár , the AdriaArray Seismology Group

The Adriatic slab beneath the Dinarides-Albanides-Hellenides represents a uniquely segmented and dynamically complex subduction system, where slab tears and edges significantly influence mantle flow patterns. Benefiting from unprecedented dense seismic data from the 2022–2025 AdriaArray deployment, we reveal sharp lateral variations in SKS anisotropy that directly image the mantle’s deformation response to slab fragmentation and subduction processes. Our SKS splitting analysis uncovers a striking spatial dichotomy: near-coastal stations record weak, slab strike-perpendicular anisotropy consistent with focused sub-slab mantle inflow, while inland stations above the subducted plate display robust, slab strike-parallel anisotropy reflecting organized mantle wedge deformation. Interpreted in the context of seismic tomography, our results provide evidence of two distinct slab tears at ∼45°N and ∼42°N. Here, toroidal mantle flow facilitates mantle wedge replenishment, reshaping mantle convection around the subduction system. Moreover, the slab’s north-south geometry varies significantly, influencing observed anisotropy patterns: the northern, thinner slab segment beneath the Dinarides is predominantly characterized by strike-parallel flow, likely occurring in the mantle wedge. The stations above the thicker, deeper southern segment beneath the Albanides-Hellenides exhibit more complex, multi-layered mantle flow, possibly integrating sub-slab, wedge, and slab-internal deformation components. These observations provide unprecedented direct evidence for how tear-induced mantle circulation and segmented subduction modulate mantle dynamics beneath a complex subduction zone.

Dinarides-Albanides-Hellenides下的亚得里亚海板块代表了一个独特的、动态复杂的俯冲系统，其中板块撕裂和边缘显著影响着地幔的流动模式。得益于2022-2025年AdriaArray部署的前所未有的密集地震数据，我们揭示了SKS各向异性的急剧横向变化，直接描绘了地幔对板块破碎和俯冲过程的变形响应。我们的SKS分裂分析揭示了一个引人注目的空间二元性：近海岸台站记录了弱的、板块走向垂直的各向异性，与集中的板块下地幔流入相一致，而俯冲板块上方的内陆台站显示了强的、板块走向平行的各向异性，反映了有组织的地幔楔变形。在地震层析成像的背景下解释，我们的结果提供了在~ 45°N和~ 42°N两个不同的板撕裂的证据。在这里，环形地幔流动促进了地幔楔的补充，重塑了俯冲系统周围的地幔对流。此外，板块的南北几何形状差异很大，影响了观测到的各向异性模式：迪纳里德板块下方的北部较薄板块主要以走向平行流动为特征，可能发生在地幔楔中。位于Albanides-Hellenides下方较厚、较深的南段之上的站点显示出更复杂的多层地幔流动，可能整合了亚板块、楔块和板块内部变形分量。这些观测结果提供了前所未有的直接证据，说明在复杂俯冲带下，撕裂诱发的地幔循环和分段俯冲如何调节地幔动力学。

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引用次数: 0

Axial-valley floor faults tell a different story than faults outside the axial valley: the role of dike-induced deformation 轴谷底断层与轴谷外的断层讲述了一个不同的故事：岩脉引起的变形的作用

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-22 DOI: 10.1016/j.epsl.2025.119796

Jie Chen , Masako Tominaga , Javier Escartín

Slow-spreading ridges are highly segmented divergent plate boundaries with various modes of magma supply and faulting. Conventionally, magmatism and faulting that accommodate the plate divergence are thought to have an inverse relationship. However, our observations on fine-scale faulting, using high-resolution Autonomous Underwater Vehicle (AUV) bathymetry data along the axial-valley floor of the 14°N segment of the Mid-Atlantic Ridge, challenge this hypothesis. We show that axial faulting decreases from the segment center to the segment end as the rate of magma supply decreases and the lithosphere cools. This general pattern is also observed on several other slow-spreading ridge segments. We propose that this pattern relates to the link between fine-scale, newly-created axial faults and fissures and modes of magma supply. At segment centers, diking is frequent and centralized to the ridge axis, yielding strain localization and creating closely-spaced faults, whereas at segment ends, diking is less frequent and more widely distributed, yielding strain delocalization with faults distributed throughout the axial valley floor.

缓展脊是高度分段的发散型板块边界，岩浆供给和断裂方式各异。传统上，岩浆活动和容纳板块发散的断层作用被认为是反比关系。然而，我们利用高分辨率自主水下航行器（AUV）测深数据，沿着大西洋中脊14°N段的轴向谷底对精细断层进行了观察，挑战了这一假设。研究表明，随着岩浆供给速率的降低和岩石圈的冷却，轴向断裂从岩石圈中心到岩石圈末端逐渐减小。在其他几个缓慢扩展的脊段上也观察到这种一般模式。我们认为这种模式与精细的、新形成的轴向断裂和裂缝与岩浆供应方式之间的联系有关。在分段中心，岩脉频繁且集中于脊轴，导致屈服应变局部化，形成紧密断层；而在分段末端，岩脉频率较低且分布较广，导致屈服应变局部化，断层分布于整个轴向谷底。

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引用次数: 0

Residual mass-independently fractionated oxygen present in solids accreted during planetesimal formation in the early Solar System: potential evidence from main group pallasites 早期太阳系中星子形成过程中固体中存在的与质量无关的残余分馏氧：来自主要类群的潜在证据

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-20 DOI: 10.1016/j.epsl.2025.119717

Martin F. Miller

Refractory Ca-Al-rich inclusions (CAIs) in chondritic meteorites, the oldest known solids in the Solar System, are characterised by ‘mass-independently fractionated’ (MIF) oxygen isotopic compositions, with δ¹⁷O variations approximately equal to those of δ¹⁸O. The apparent absence of this characteristic from nearly all other oxygen-bearing constituents of early-formed asteroids, together with the brief formation interval for CAIs, indicates that the process responsible was localised and of short duration in the context of Solar System evolution. From reassessing a recent study of main group pallasite meteorites, it is argued that the oxygen isotopic compositions of their coexisting olivine and chromite potentially provide evidence that a minor component of solids containing MIF oxygen was accreted during formation of the parent planetesimal, or its precursors, shortly after CAI formation. Modelling indicates that a contribution of ∼1.6 ± 0.3 % conforming to δ¹⁷O ∼ δ¹⁸O – γ, for γ assigned as –1.21 or –3.45 (from literature data) is consistent with the reported measurements. If true, and the pallasite olivine and chromite derived from the mantle of an impacted planetesimal and the IIIAB parent body respectively, as proposed elsewhere, then a ‘residual’ MIF oxygen component must have been present in solids accreted by those early planetesimals, probably in the same feeder zone. A testable prediction is that such residual MIF oxygen may similarly have been accreted in more early-formed planetesimals than recognised hitherto. If so, its presence should be detectable from comparable measurements of coexisting oxygen-bearing minerals in the associated meteorites, subject to the δ¹⁸O range being of sufficient magnitude.

球粒陨石中的难熔富钙铝包裹体（CAIs）是太阳系已知最古老的固体，其特征是“质量无关分异”（MIF）氧同位素组成，δ17O的变化近似等于δ18O的变化。在早期形成的小行星中，几乎所有其他含氧成分都明显缺乏这一特征，再加上cai的形成间隔很短，这表明在太阳系演化的背景下，这一过程是局部的，持续时间很短。通过重新评估最近对主要类群pallasite陨石的研究，认为它们共存的橄榄石和铬铁矿的氧同位素组成可能提供了证据，表明在母星子或其前体形成后不久，在母星子或其前体形成期间，含有少量MIF氧的固体成分被吸积。建模表明，δ17O ~ δ18O - γ的贡献为~ 1.6±0.3%，γ的分配为- 1.21或- 3.45（来自文献数据）与报道的测量结果一致。如果这是真的，并且像其他地方提出的那样，pallasite橄榄石和铬铁矿分别来自受影响的星子和IIIAB母体的地幔，那么“残余”的MIF氧成分一定存在于这些早期星子吸积的固体中，可能在同一个喂养区。一个可验证的预测是，这种残余的MIF氧可能在更多的早期形成的星子中被吸积，而不是迄今为止所认识到的。如果是这样，在δ18O值范围足够大的情况下，通过对伴生陨石中共存的含氧矿物的可比测量，应该可以探测到它的存在。

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引用次数: 0

Coral reef terrace age deduced from retreating knickpoints 珊瑚礁阶地年龄由退缩的凿点推断

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-18 DOI: 10.1016/j.epsl.2025.119792

Yiran Wang , Aron J. Meltzner , Michael E. Oskin , Jennifer Quye-Sawyer , Lin Thu Aung , Noelynna Ramos

The accurate dating of Quaternary coral terraces has long been challenging due to recrystallization of aragonite corals. Here, we present an approach to infer terrace age based on (1) the linkage between sea-level drop and river knickpoint formation and (2) the history of sea-level rise and fall recorded by the elevation–age relationship of knickpoints. Our study in northwestern Luzon, Philippines, combines field surveys, sedimentological analysis, and topographic and river-profile analysis, through which we map the coral reef terrace extent and correlate terrace outer edges to the initiation location of major knickpoints in adjacent river profiles. Through χ transformation, the knickpoint retreat distance is equivalent to knickpoint/terrace age, and therefore the elevation–retreat distance relationship of the knickpoints can be used to determine the age of the correlated terrace. Using this method, we deduce that the lower coral reef terrace sequences (T1-T4) correspond to Marine Isotope Stages (MIS) 5a, 5c, 5e, and 7a, respectively. Furthermore, we suggest the coastal area is gently tilting seaward with an average uplift rate of ∼1 m/kyr, and the highest terrace surface (420–440 m) may be more than 400 kyr old. We propose that this technique offers a promising solution for dating coral reef terraces in uplifting coastal regions where absolute age-dating techniques fail due to diagenetic alteration, and for terraces associated with bedrock rivers that developed before the penultimate glacial period.

由于文石珊瑚的再结晶，第四纪珊瑚梯田的准确测年一直是一个挑战。在此，我们提出了一种基于(1)海平面下降与河流裂缝点形成之间的联系以及(2)裂缝点的高程-年龄关系记录的海平面上升和下降的历史来推断阶地年龄的方法。我们在菲律宾吕宋岛西北部的研究结合了实地调查、沉积学分析、地形和河流剖面分析，通过这些分析，我们绘制了珊瑚礁阶地的范围，并将阶地的外缘与邻近河流剖面中主要断裂点的起始位置相关联。通过χ变换，裂缝点的后退距离相当于裂缝点/阶地年龄，因此可以利用裂缝点的高程-后退距离关系来确定相关阶地的年龄。利用该方法，我们推断下部珊瑚礁阶地层序（T1-T4）分别对应于海洋同位素阶段（MIS） 5a、5c、5e和7a。此外，我们认为沿海地区缓慢向海倾斜，平均隆升速率为~ 1 m/kyr，最高阶地表面（420-440 m）可能超过400 kyr。我们提出，这项技术为隆升沿海地区的珊瑚礁阶地的定年提供了一种有希望的解决方案，在这些地区，绝对年龄测年技术由于成岩蚀变而失败，以及与第二次冰期之前发育的基岩河流相关的阶地。

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引用次数: 0

In-situ U-Pb dating of early marine carbonate cements constrains the age of the late Ediacaran lower Nama Group, Namibia 早期海相碳酸盐胶结物的原位U-Pb定年限制了纳米比亚晚埃迪卡拉世下Nama群的年龄

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-18 DOI: 10.1016/j.epsl.2025.119787

Mariana A. Yilales , Nick MW Roberts , Collen-Issia Uahengo , Nathan Rochelle-Bates , Fred Bowyer , Rachel Wood

The middle-late Ediacaran (∼580 to >533 Ma) saw the emergence and early diversification of animals (metazoans), but the tempo of this event is obscured by a paucity of datable ash beds and uncertainties in global stratigraphic correlation through specific intervals. The Nama Group, Namibia, is of fundamental importance as this succession preserves a diverse terminal Ediacaran fossil assemblage that includes the first appearance of metazoan biomineralization, a key evolutionary innovation. The precise age of the lowermost Nama Group is unknown, however, with best estimates based on global chemostratigraphic correlation and inferred depositional rates suggesting that the onset of deposition was between ca. 555 and 551 Ma. Here we use uranium-lead (U-Pb) radioisotopic dating by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), to date early marine pseudomorphed calcite cements from the lower Nama Group. The analyses yield an absolute age of 549.3 ± 9.8 Ma and constitute the first independent time constraint for the lowermost Nama Group. The result is consistent with current chemostratigraphic age models and validates the use of in-situ U-Pb dating of early marine carbonate cements to constrain depositional ages.

埃迪卡拉纪中晚期（~ 580 ~ >533 Ma）出现了动物（后生动物）的出现和早期多样化，但这一事件的速度由于缺乏可测定的火山灰床和通过特定间隔的全球地层对比的不确定性而模糊不清。纳米比亚的Nama群具有根本性的重要性，因为这一演替保留了多样化的埃迪卡拉末期化石组合，其中包括后生动物生物矿化的首次出现，这是一个关键的进化创新。然而，最底下的Nama群的确切年龄尚不清楚，根据全球化学地层对比和推断的沉积速率，最好的估计表明，沉积开始于约555至551 Ma之间。在这里，我们使用激光烧蚀电感耦合等离子体质谱（LA-ICP-MS）的铀铅（U-Pb）放射性同位素定年，确定了Nama群下部早期海洋伪晶方解石胶结物的年代。分析得出的绝对年龄为549.3±9.8 Ma，是最底的Nama群的第一个独立的时间约束。该结果与目前的化学地层年龄模型一致，并验证了早期海相碳酸盐胶结物原位U-Pb定年对沉积年龄的约束。

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引用次数: 0

Sediment provenance and transport pathways along the Atlantic Iberian Margin 大西洋伊比利亚边缘沉积物的来源和运输路径

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-18 DOI: 10.1016/j.epsl.2025.119788

Sara Campderrós , Leopoldo D. Pena , Ester Garcia-Solsona , Eduardo Paredes-Paredes , Albert Català , Jaime Frigola , Negar Haghipour , Isabel Cacho

The Atlantic Iberian margin is a dynamic region where oceanographic processes interact with continental sediment, influencing transport and deposition. To identify sediment sources and dominant transport dynamics we combine ⁸⁷Sr/⁸⁶Sr and Ɛ_Nd measurements on terrigenous sediments and ¹⁴C dating of planktonic foraminifera from core-tops along the margin. We present a new dataset of Sr-Nd isotope data from the Iberian Peninsula to characterize the isotopic composition of main river basins, considered potential sediment sources alongside African dust. By solving a ternary isotope mixing system, combined with a new statistical method to account for endmember isotopic distributions, we quantify the relative contribution of source areas to our samples. Our results reveal: 1) the margin is characterized by three isotopically distinct regions, 2) African dust is an important component of the terrigenous sediment (∼60 %), 3) regional differences in isotopic values reflect the influence of major river discharges: Guadalquivir in the south, Tagus in the centre, and Douro in the north, and 4) sediment transport follows a net northward direction along-slope. This sediment transport is attributed to the northward-flowing Mediterranean Outflow Water (MOW), which entrains and redistributes sediments along-slope. This is further supported by foraminifera ¹⁴C results, showing older radiocarbon ages along the MOW path, indicating sediment erosion. In contrast, younger radiocarbon ages are consistently found below MOW depths. The combined ⁸⁷Sr/⁸⁶Sr, Ɛ_Nd and ¹⁴C data suggest that MOW flow reduces sediment deposition along its path, transporting sediments northward, where it predominantly settles below the interface between MOW and the underlying North East Atlantic Deep Water.

大西洋伊比利亚边缘是一个海洋过程与大陆沉积物相互作用的动态区域，影响着运输和沉积。为了确定沉积物的来源和主要的输运动力学，我们结合了陆源沉积物的87Sr/86Sr和ƐNd测量以及沿边缘岩心顶部浮游有孔虫的14C测年。我们提出了一个新的来自伊比利亚半岛的Sr-Nd同位素数据集，以表征主要河流流域的同位素组成，这些流域被认为是非洲沙尘的潜在沉积物来源。通过求解三元同位素混合系统，结合一种新的统计方法来解释端元同位素分布，我们量化了源区对样品的相对贡献。结果表明：1)陆源沉积物主要由3个不同的区域组成；2)非洲沙尘是陆源沉积物的重要组成部分（约60%）；3)同位素值的区域差异反映了主要河流流量的影响：南部为瓜达尔基维尔，中部为塔古斯，北部为杜罗；4)沉积物沿坡向净北输。这种泥沙运移归因于向北流动的地中海流出水（MOW），它沿着斜坡携带和重新分配沉积物。有孔虫14C的结果进一步支持了这一点，显示出沿着MOW路径的更古老的放射性碳年龄，表明沉积物侵蚀。相比之下，更年轻的放射性碳年龄一直在MOW深度以下被发现。87Sr/86Sr、ƐNd和14C的综合数据表明，MOW流减少了其路径沿线的沉积物沉积，将沉积物向北输送，沉积物主要沉积在MOW流与下伏的东北大西洋深水界面下方。

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引用次数: 0

Isotope effects (Cl, O, C) of heterogeneous electrochemistry induced by Martian dust activities 火星尘埃活动诱导的非均相电化学同位素效应（Cl， O， C）

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-18 DOI: 10.1016/j.epsl.2025.119784

Neil C. Sturchio , Hao Yan , Alian Wang , W. Andrew Jackson , Huiming Bao , Chuck Y.C. Yan , Linnea J. Heraty , Yu Wei , Quincy H.K. Qu , Kevin S. Olsen

Some oxidized compounds in Martian soils may form through heterogeneous electrochemistry (HEC) stimulated by electrostatic discharge (ESD) during dust storms and dust devils. To test this hypothesis, we conducted medium-strength ESD experiments in a Mars simulation chamber and analyzed the Cl, O, and C isotopic compositions of the resulting chloride, (per)chlorate, and carbonate products. These ESD products exhibit substantial mass-dependent depletions in heavy isotopes relative to the reactants: ε³⁷Cl from -11.3 ‰ to +2.0 ‰, ε¹⁸O from -34.5 ‰ to -12.9 ‰, and ε¹³C around -11.4 ‰. These results, when compared with isotopic measurements from recent Mars missions (ESA’s ExoMars Trace Gas Orbiter and the Sample Analysis at Mars (SAM) instrument package aboard NASA’s Curiosity rover) and Martian meteorites, indicate that HEC induced by Martian dust activities can account for a substantial portion of the (per)chlorates and carbonates identified at the surface of Mars and the HCl in its atmosphere.

火星土壤中的一些氧化化合物可能是在沙尘暴和尘暴期间静电放电（ESD）刺激下形成的非均质电化学（HEC）。为了验证这一假设，我们在火星模拟室内进行了中等强度的ESD实验，并分析了氯、氯酸盐和碳酸盐产物的Cl、O和C同位素组成。这些ESD产物的重同位素相对于反应物表现出明显的质量依赖性损耗：ε37Cl从-11.3‰到+2.0‰，ε18O从-34.5‰到-12.9‰，ε13C在-11.4‰左右。这些结果，当与最近的火星任务（ESA的ExoMars痕量气体轨道器和NASA的好奇号火星车上的火星样本分析（SAM）仪器包）和火星陨石的同位素测量结果进行比较时，表明由火星尘埃活动引起的HEC可以解释在火星表面发现的氯酸盐和碳酸盐以及大气中的HCl的很大一部分。

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引用次数: 0

Changing volatile emissions and sources along the Ethiopian Rift 沿着埃塞俄比亚裂谷变化的挥发性排放物和来源

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-18 DOI: 10.1016/j.epsl.2025.119782

Abate A. Melaku , Gemechu B. Teferi , Takele Mihretie , Snorri Gudbrandsson , Yared Sinetebeb , Peter H. Barry , Tobias P. Fischer , Finlay M. Stuart , Ugur Balci , Sæmundur A. Halldórsson , Chris J. Ballentine , Darren J. Hillegonds , Emma L. Chambers , Derek Keir , Richard Bates , William Hutchison

Rift volcanoes are sites of intense volatile emissions. However, major uncertainties remain about the magnitude of rift volatile fluxes, particularly for greenhouse gases (e.g. CO₂) and whether along-rift variations in degassing relate to changing mantle sources and/or rifting processes (i.e. melt production and lithospheric thinning). Here, we investigate CO₂ flux and gas isotopes in Ethiopia; a mature, plume-influenced continental rift. We focus on one of the largest caldera volcanoes, Bora-Baricha-Tulu Moye (BBTM), which is situated in a region of high mantle melt production in the Central Main Ethiopian rift (∼500 km south-west the putative plume head). BBTM gases are characterized by plume-like ³He/⁴He values up to 17 R_a (the highest ever observed in Ethiopian Rift fumaroles) and we calculate total magmatic CO₂ flux of 757–901 t d^-1 (making BBTM the largest volcanic CO₂ emitter in the Ethiopian Rift). Using our CO₂ flux measurements, we estimate total CO₂ emissions from Ethiopia’s volcanic systems to be 2500–9200 kt yr^-1 and reveal important along-rift variation in CO₂ flux. High CO₂ flux sectors are found in Central Afar, as well as the Northern and Central Main Ethiopian Rift. These sectors are all regions of high partial melt content (evidenced by low seismic velocity in the underlying mantle) and also show the greatest ³He/⁴He values (>14 R_a). Cooccurrence of high mantle melt production, elevated CO₂ emissions and high ³He/⁴He demonstrates that in mature continental rifts carbon emissions and plume volatile contributions are particularly elevated in regions of greatest lithospheric thinning and mantle melting.

裂谷火山是释放大量挥发性物质的地方。然而，裂谷挥发性通量的大小，特别是温室气体（如二氧化碳）的大小，以及沿裂谷脱气的变化是否与变化的地幔源和/或裂谷过程（即熔体产生和岩石圈变薄）有关，仍然存在重大的不确定性。在这里，我们研究了埃塞俄比亚的二氧化碳通量和气体同位素；一个成熟的、受羽状物影响的大陆裂谷。我们的重点是最大的火山口火山之一，Bora-Baricha-Tulu Moye (BBTM)，它位于埃塞俄比亚中部裂谷的高地幔熔体生产区域（假定的羽头西南约500公里）。BBTM气体以羽状的3He/4He值为特征，高达17 Ra（埃塞俄比亚裂谷喷气孔中观测到的最高值），我们计算出总岩浆CO2通量为757-901 t d-1（使BBTM成为埃塞俄比亚裂谷中最大的火山CO2排放者）。利用我们的二氧化碳通量测量，我们估计埃塞俄比亚火山系统的二氧化碳总排放量为2500 - 9200kt年-1，并揭示了二氧化碳通量沿裂谷的重要变化。高二氧化碳通量区位于阿法尔中部以及埃塞俄比亚北部和中部裂谷。这些扇区都是部分熔体含量高的区域（下伏地幔地震速度低），也显示出最大的3He/4He值（>14 Ra）。高地幔熔体产量、高CO2排放和高3He/4He的同时发生表明，在成熟大陆裂谷中，岩石圈减薄和地幔融化最严重的地区，碳排放和地幔柱挥发贡献特别高。

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引用次数: 0

Isotopic constraints on the Barium subduction cycle 钡俯冲旋回的同位素约束

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-17 DOI: 10.1016/j.epsl.2025.119789

Qasid Ahmad , Martin Wille , Carolina Rosca , Thomas Pettke , Jörg Hermann , Stephan König

Subduction processes regulate elemental cycling and consequently the composition of Earth’s geochemical reservoirs - mantle, crust, atmosphere, and hydrosphere, exerting far-reaching effects for the evolution of life. Barium (Ba) is essential for understanding crust-mantle recycling, especially since over 90 % of Ba in arc lavas originates from subducted materials. While Ba enrichments in arc lavas have long been attributed to contributions from oceanic crust derived aqueous fluids, recent studies highlight hydrous sediment melts as a key carrier. Here, we present high-precision Ba isotope data (δ^138/134Ba) of input and output from the Tongan subduction zone. The results show that Ba is not predominantly supplied by the subducting oceanic crust. Instead, most Ba can be traced back to subducting sediments from which it is released in two stages. During early subduction, sedimentary barite dissolves and releases isotopically heavy Ba via aqueous fluids into the serpentinized mantle wedge, where this Ba is later remobilized during subsequent breakdown. With continued slab descent, remaining lithogenic phengite releases isotopically lighter Ba, which is recycled at subarc depths by hydrous melting. Both mechanisms can explain the entire range of Ba/Th and δ^138/134Ba in Tongan arc lavas without requiring Ba isotope fractionation between fluids and solids. These results from the endmember setting of Tonga, with minimal subducting sediments, imply higher proportion of sediment-derived Ba in other arcs worldwide. The Forearc Serpentinite Signature (FSS), which is created by the interaction of the mantle wedge with sediment-derived fluids at low temperatures (<600 °C), represents an additional fluid endmember that must be considered in the genesis of arc lavas. Lithogenic Ba that is not completely released at subarc depths can be further subducted into the deeper mantle, where it may later enrich mantle domains that source mid-ocean ridge and hotspot lavas. The relative proportions of sedimentary components in subducted slabs have changed over Earth’s history, highlighting the link between arc magma and mantle compositions and long-term shifts in Earth’s surface (bio)geochemical cycles.

俯冲过程调节了元素循环，从而调节了地球地球化学储层——地幔、地壳、大气和水圈的组成，对生命的进化产生了深远的影响。钡（Ba）对于理解壳幔再循环至关重要，特别是因为弧熔岩中超过90%的Ba来自俯冲物质。虽然弧熔岩中的Ba富集一直被认为是来自海洋地壳的含水流体的贡献，但最近的研究强调含水沉积物熔体是一个关键的载体。在此基础上，我们获得了铜安俯冲带输入和输出的高精度Ba同位素（δ138/134Ba）数据。结果表明，Ba主要不是由俯冲洋壳供给的。相反，大多数钡元素可以追溯到俯冲沉积物中，并分两个阶段释放出来。在早期俯冲过程中，沉积重晶石溶解，并通过水溶液将同位素重钡释放到蛇纹岩化的地幔楔中，在随后的破裂过程中，这些钡被重新活化。随着板块继续下降，剩余的成岩辉长岩释放出同位素较轻的Ba，在亚弧深度通过水熔融再循环。这两种机制都可以解释汤加弧熔岩中Ba/Th和δ138/134Ba的整个范围，而不需要流体和固体之间的Ba同位素分馏。这些结果来自汤加的端元环境，俯冲沉积物最少，意味着世界上其他弧中沉积源钡的比例更高。弧前蛇纹岩特征（FSS）是由地幔楔与低温（<600°C）下的沉积流体相互作用形成的，它代表了弧熔岩成因中必须考虑的另一个流体端元。在次弧深度未完全释放的造岩钡可以进一步俯冲到更深的地幔中，在那里它可能后来丰富了形成洋中脊和热点熔岩的地幔域。俯冲板块中沉积成分的相对比例在地球历史上发生了变化，突出了弧岩浆和地幔成分之间的联系以及地球表面（生物）地球化学循环的长期变化。

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引用次数: 0

Melting phase relations in Fe-FeS under Martian core pressures: Crystallization of Fe12S7 at the inner core? 火星核压力下Fe-FeS的熔融相关系：Fe12S7在内核的结晶？

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-17 DOI: 10.1016/j.epsl.2025.119785

Fumiya Sakai , Kei Hirose

Sulphur is believed to be a major light element in the Martian core, and if it is the single light element, 15 wt% to 34 wt% S is required to explain the mean core density deduced from the recent InSight observations. The existing Fe-FeS phase diagram at 21 GPa suggests the crystallization of Fe₃₊_xS₂ from such sulphur-rich core liquids, but melting phase relations at ∼40 GPa corresponding to Mars’ centre pressure are not known yet. Here we performed both subsolidus and melting experiments on Fe + 22.3–27.5 wt% S samples between 26 and 175 GPa to constrain the S-rich portion of the Fe-FeS phase diagram. Present experiments were conducted up to a pressure range much higher than that for the Mars’ core in order to constrain the melting curve and compression behaviour of Fe₁₂S₇. Synchrotron X-ray diffraction measurements demonstrated that Fe₁₂S₇ is formed above 27 GPa and Fe_3.2S₂ decomposes into Fe₁₂S₇ + FeS at least above 29 GPa. We also found that Fe₂S incongruently melts to liquid + Fe₁₂S₇, showing that Fe₁₂S₇ crystallizes from liquid Fe containing 20 to 25 wt% S under the proposed pressure and temperature at the Mars’ centre. Fe₁₂S₇ forms also from S-rich Fe-S-C/Fe-S-O core liquids following the crystallization of Fe₃C/FeO. Furthermore, the equation of state of Fe₁₂S₇ indicates its density is higher than the range of observed Martian mean core density. These suggest that the Martian inner core, if it exists, likely includes Fe₁₂S₇, even when considering the presence of other light elements.

硫被认为是火星核心的主要轻元素，如果它是唯一的轻元素，则需要15 wt%至34 wt%的硫来解释最近洞察号观测得出的平均核心密度。现有的21 GPa的Fe-FeS相图表明，Fe3+xS2是从这种富硫核心液体中结晶出来的，但与火星中心压力对应的~ 40 GPa的熔化相关系尚不清楚。在这里，我们对Fe + 22.3 - 27.5% wt% S样品在26 - 175 GPa之间进行了亚固态和熔融实验，以约束Fe- fes相图中富S部分。为了限制Fe12S7的熔化曲线和压缩行为，本实验在远高于火星核心的压力范围内进行。同步x射线衍射测量表明，Fe12S7在27gpa以上形成，Fe3.2S2在29gpa以上分解为Fe12S7 + FeS。我们还发现Fe2S不一致地熔化为液态+ Fe12S7，这表明Fe12S7是在火星中心所提出的压力和温度下由含20 - 25wt % S的液态Fe结晶而成的。Fe12S7也由富s的Fe-S-C/Fe-S-O核心液体在Fe3C/FeO结晶后形成。此外，Fe12S7的状态方程表明其密度高于观测到的火星平均核密度范围。这表明，即使考虑到其他轻元素的存在，火星内核（如果存在的话）也可能包含Fe12S7。

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引用次数: 0