Earth and Planetary Science Letters最新文献

{"title":"Structural heterogeneity and anisotropy beneath Myanmar: Insights into the complex deformation of the Indo-Burma subduction zone","authors":"Yiming Bai ,&nbsp;Shengji Wei ,&nbsp;Jing Chen ,&nbsp;Tianjue Li ,&nbsp;Bingfeng Zhang ,&nbsp;Xiao Xiao ,&nbsp;Shucheng Wu ,&nbsp;Jiayuan Yao ,&nbsp;Yu Wang ,&nbsp;Ping Tong","doi":"10.1016/j.epsl.2026.119879","DOIUrl":"10.1016/j.epsl.2026.119879","url":null,"abstract":"<div><div>The highly oblique Indo-Burma convergence has produced complex tectonic deformation along the Myanmar margin, and the depth-resolved anisotropy offers a valuable means to elucidate the mechanisms that drive this deformation. Here, we build a 3-D anisotropic body-wave velocity model in the upper 80 km using the adjoint-state traveltime tomography applied to an AI-assisted local earthquake catalog. The new model reveals pronounced azimuthal anisotropy and velocity heterogeneities. In the overriding Burma plate crust, a complex anisotropic structure is observed: fast velocity directions (FVDs) normal to the trench beneath the inner Indo-Burma Ranges while broadly parallel to the tectonic block boundaries and fault strikes beneath the Central Myanmar Basin. These patterns reflect transpressive deformation under oblique convergence. In the uppermost mantle, the observed ENE-WSW FVDs west of the Wuntho-Popa Arc are attributed to the fossil fabric in the subducting Indian plate, and the NNW-SSE FVDs farther east are associated with supra-slab along-strike flow, possibly shaped by the slab geometry complexity. Additionally, the segment of the Sagaing Fault near 21°N is likely infiltrated by crustal fluids originating from the adjacent Mogok Metamorphic Belt, potentially linked to recent asthenospheric melt upwelling. Evidence for fluid presence includes a near-fault crustal anomaly with ∼8% velocity reduction, high <em>Vp</em>/<em>Vs</em> of &gt;1.85 and FVDs parallel to the maximum horizontal compressive stress. Fluid infiltration likely promotes partial creep in this fault segment, and, together with variations in lithology and deformation state, may affect earthquake nucleation along this portion of the Sagaing Fault, including the 2025 Mw 7.8 Mandalay event.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119879"},"PeriodicalIF":4.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090727","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":"Two episodes of ultrahigh-temperature metamorphism within one orogenic cycle","authors":"Jie Dong ,&nbsp;Chunjing Wei ,&nbsp;Shuguang Song ,&nbsp;Guochun Zhao ,&nbsp;Guibin Zhang","doi":"10.1016/j.epsl.2026.119887","DOIUrl":"10.1016/j.epsl.2026.119887","url":null,"abstract":"<div><div>Ultrahigh-temperature metamorphism (UHTM) is significant for constraining the thermal-mechanical evolution of continental crust, which can periodically occur within one orogenic cycle involving subduction, collision and subsequent extension stages. However, multi-episode UHTM within one orogenic cycle has been rarely reported. Here, we performed a comprehensive investigation of petrography, phase equilibria modelling, and zircon U-Pb dating for felsic and Mg-Fe-Al granulites from the Kunlun-Qaidam Massif in north Qingzang Plateau. Three episodes of metamorphism were inferred, involving two episodes of low pressure (LP)-UHTM intervened by an episode of medium-pressure and high-temperature (MP-HT) metamorphism. The first episode LP-UHTM (I) exhibits peak <em>P–T</em> conditions of 0.5–0.8 GPa/930–1050 °C, occurring at &gt;460 Ma. The second episode MP-HT metamorphism (II) was achieved by compressional cooling from the LP-UHT conditions to MP-HT conditions of &gt;0.9–1.2 GPa/&lt;820–900 °C. This was followed by decompressional heating to another episode of LP-UHTM (III) with conditions of 0.55–0.75 GPa/900–1070 °C at &gt;410 Ma. Combining our metamorphic studies and other geological data, a three-stage tectonic model is proposed: (a) oceanic slab rollback inducing an arc-backarc extension and the LP-UHTM (I) during the late-stage subduction of the Proto-Tethys Ocean; (b) continental subduction-collision leading to the thickening of hot arc-backarc crust and the MP-HT metamorphism (II) after the closure of the Proto-Tethys Ocean, and (c) post-collisional crustal thinning and mantle upwelling related to lithosphere delamination resulting in the LP-UHTM (III). It is for the first time that we recognize two episodes of LP-UHTM occurring within &lt; 50 Myr in one orogenic cycle.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119887"},"PeriodicalIF":4.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090728","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":"Extended time delay and complex rupture behaviors of dynamically triggered earthquakes on gouge-filled fault","authors":"Yishuo Zhou ,&nbsp;Ran Xu ,&nbsp;Peng Dong ,&nbsp;Kaiwen Xia","doi":"10.1016/j.epsl.2026.119853","DOIUrl":"10.1016/j.epsl.2026.119853","url":null,"abstract":"<div><div>Seismic waves emitted by an earthquake can trigger other earthquakes over a variety of spatial and temporal scale, yet extended time delay and rupture behaviors associated with these events are not well understood. Here, we report on the experimental observation of earthquake rupture triggered by explosion-generated stress perturbations at different stress level, showing that the time delay of triggered events on gouge-filled fault is significantly higher than those on bare fault. Furthermore, we identify notable difference in rupture behaviors between the triggered events on gouge-filled and bare faults. For bare fault, the triggered events may be arrested or runaway, depending on the initial stress level at the onset of dynamic triggering. However, for gouge-filled fault, the rupture behaviors is more complex, manifested by scattered micro-ruptures, coalescent micro-ruptures, and runaway rupture. The extended time delay and complex rupture behaviors of triggered events on gouge-filled fault are attributed to the evolution of force chain within the fault gouge. Our results suggest that fault gouge plays an important role in earthquake dynamic triggering, which may provide new insights into the mechanism for extended time delay of dynamically triggered earthquakes on natural fault systems.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119853"},"PeriodicalIF":4.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090730","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":"Tracking deep mantle heat and volatiles in the Iceland plume from a high-density survey of helium isotopes along the Reykjanes Ridge","authors":"U. Balci ,&nbsp;L. Di Nicola ,&nbsp;J.G. Fitton ,&nbsp;R.N. Taylor ,&nbsp;F.M. Stuart","doi":"10.1016/j.epsl.2026.119882","DOIUrl":"10.1016/j.epsl.2026.119882","url":null,"abstract":"<div><div>The upwelling mantle plume beneath Iceland flows southwest down the Reykjanes Ridge. Several prominent V-shaped ridges (VSRs) and troughs (VSTs) extend obliquely from the ridge that are believed to result from pulses of hotter plume mantle. The intimate connection between heat and primordial He in the deep mantle means that the mantle beneath the Reykjanes Ridge should have elevated ³He/⁴He. A new high resolution He isotope study of basaltic glasses from southernmost Iceland (63°N) to 55°N along the Reykjanes Ridge demonstrates a broad peak of ³He/⁴He (16.0 R_a) centred around 60°N that coincides with the first topographic high (VSR-1). The magnitude of the He isotope anomaly broadly scales with the excess temperature inferred from crustal thickness. This supports the hypothesis that thickened oceanic crust is a consequence of a pulse of hotter mantle within the upwelling plume that flows down the Reykjanes Ridge. The along-ridge ³He/⁴He peak at 59-62°N is significantly longer (320 km) than the thickened oceanic crust of VSR-1 (60-70 km). This can most simply be explained if the hot mantle blob is surrounded by a high ³He/⁴He mantle carapace that has a temperature similar to the surrounding mantle. As helium diffusion is orders of magnitude slower than heat, this relationship can be most simply explained if the outer region of the hot, He-rich blob has lost heat to the surrounding mantle during transit from the core-mantle boundary, yet retained the deep mantle He isotope fingerprint.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119882"},"PeriodicalIF":4.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090736","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":"Oxygen vacancy diffusion in davemaoite (CaSiO3 perovskite): Implications for the redox equilibrium and the electrical conductivity of Earth’s lower mantle","authors":"Maximilian Schulze,&nbsp;Gerd Steinle-Neumann","doi":"10.1016/j.epsl.2026.119861","DOIUrl":"10.1016/j.epsl.2026.119861","url":null,"abstract":"<div><div>Davemaoite (CaSiO₃), a major rock-forming mineral in the Earth’s lower mantle, adopts a perovskite structure, which is known for the rapid diffusion of extrinsic oxygen vacancies (OV). Here, we use molecular dynamics simulations in conjunction with a machine learning potential to systematically investigate extrinsic OV diffusion in davemaoite at lower mantle conditions. We determine diffusion coefficients (<em>D</em>_v) for a series of temperatures along isobars of 25, 50, 75, 100 and 125 GPa and find that computed diffusivities closely follow an Arrhenian behavior. The pre-exponential factor is pressure independent with <span><math><mrow><mi>log</mi><msubsup><mi>D</mi><mi>v</mi><mo>∘</mo></msubsup><mspace></mspace><mo>=</mo><mspace></mspace></mrow></math></span>-6.53  ±  0.06 and the activation enthalpy increases nonlinearly with pressure from 0.87 eV to 1.66 eV. On the basis of the Arrhenian model, we predict that <em>D</em>_v decreases throughout the lower mantle by at least one order of magnitude along geotherms representative of the ambient mantle and subducted lithosphere. We argue that despite the high OV diffusivities, the davemaoite component of subducted oceanic crust does not achieve complete redox equilibration with the surrounding mantle on its way to the core-mantle boundary, and that significant redox exchange is limited to the upper parts of the lower mantle. Finally, we provide arguments that the electrical conductivity of most parts of the lower mantle cannot be explained by ionic conductivity and that its electrical conductivity must therefore be determined by iron-induced polaron hopping.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119861"},"PeriodicalIF":4.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090726","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":"Zircon thermal annealing ages determine a late Eocene birth for the First Bend of the Yangtze River","authors":"Yang Zhang ,&nbsp;Rui Li ,&nbsp;Guang-Yan Zhou ,&nbsp;David Chew ,&nbsp;Jian-Ping Zheng ,&nbsp;Qing Xiong ,&nbsp;Wei Wang","doi":"10.1016/j.epsl.2026.119888","DOIUrl":"10.1016/j.epsl.2026.119888","url":null,"abstract":"<div><div>Understanding the evolution of the First Bend of the Yangtze River is essential in deciphering the Cenozoic tectonic dynamics of the Tibetan Plateau and the associated intricate interplay between surface uplift, river erosion and sediment deposition. Nevertheless, the precise timing and mechanisms for its formation remain a subject of debate, primarily stemming from the ambiguous interpretation of sediment provenance studies that solely rely on detrital zircon U-Pb ages. Here, we employ zircon Raman spectroscopy data integrated with a new developed support vector machine model to assess whether detrital zircons from the Eocene Jianchuan Basin underwent thermal annealing after crystallization. Combined with zircon depth profiling U-Pb age data, we show that the sediments in the lower to middle sequences of the Jianchuan Basin were predominantly sourced from the Qiangtang terrane and the western Yangtze region, implying paleo-Yangtze (Jinsha) River once flowed southwards through this basin. In contrast, the overlying Jianchuan Formation mainly received recycled detritus from the underlying Paleozoic sedimentary strata. This shift in sediment supply to the Jianchuan Basin was caused by the uplift within and surrounding the basin induced by a change in stress regime from extension to compression, which resulted in the reorganization of the paleo-Yangtze river and ultimately the formation of the First Bend and the modern Yangtze River during the late Eocene.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119888"},"PeriodicalIF":4.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090735","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":"Permian mylonites in the footwall of a Miocene Cycladic core complex (Ios, Greece): Insights from (micro)structurally integrated apatite U-Pb petrochronology","authors":"Megan Elysia Flansburg ,&nbsp;Daniel Fritz Stockli ,&nbsp;Eirini Maria Poulaki ,&nbsp;Konstantinos Soukis ,&nbsp;Lisa Danielle Stockli","doi":"10.1016/j.epsl.2026.119857","DOIUrl":"10.1016/j.epsl.2026.119857","url":null,"abstract":"<div><div>Oligo-Miocene large-magnitude extension and the formation of metamorphic core complexes accommodated exhumation of High Pressure/Low Temperature (HP/LT) rocks in the eastern Mediterranean. Previous studies on Ios Island in the southern Cyclades have associated mylonitic fabrics exposed within the crystalline Cycladic Basement and along its contact with the overlying Cycladic Blueschist Unit, termed the South Cycladic Shear Zone, with Oligo-Miocene extension in the backarc of the retreating Hellenic subduction zone. We utilized apatite U-Pb geo-thermochronology, combined with Ti-in-Quartz and quartz c-axis opening-angle thermometry and microstructural characterization of mylonitic fabrics, to constrain the timing of mylonitization preserved in the footwall of the South Cycladic Shear Zone. Apatite U-Pb ages of the high-temperature (&gt; ca. 500°C) mylonites in the Basement Core are Permo-Carboniferous (ca. 302—270 Ma), with two samples yielding apparent Mesozoic apatite U-Pb ages and whose U-Pb and REE systematics may have been perturbed by Cenozoic tectonics. Despite lower-temperature (300—400°C) mylonitization within the South Cycladic Shear Zone, rocks there preserve exclusively Permo-Carboniferous (ca. 307–297 Ma) apatite U-Pb ages, corresponding to either relict high-temperature quartz domains (ca. &gt;500°C) or a detrital age signature sourced from the Cycladic Basement, but not to Cenozoic movement along the interface. The dominance of Permian cooling ages suggests that significant exhumation of the Cycladic Basement occurred prior to and concurrent with deposition of the earliest Cycladic Blueschist Unit in the late Permian to early Triassic, and that Cycladic core complexes preserve high-temperature fabrics related to pre-Miocene extension. Importantly, this work advises caution when assuming the age of mylonitic fabrics in the footwalls of metamorphic core complexes across the globe without integrating deformation conditions within thermochronometric and geochemical context.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119857"},"PeriodicalIF":4.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146036668","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":"Frictional weakening of gabbro faults after quasi-stationary contact under hydrothermal conditions","authors":"Wei Feng ,&nbsp;Lu Yao ,&nbsp;Shengli Ma ,&nbsp;Feng Shi ,&nbsp;Jinyu Zheng ,&nbsp;Giulio Di Toro","doi":"10.1016/j.epsl.2026.119893","DOIUrl":"10.1016/j.epsl.2026.119893","url":null,"abstract":"<div><div>Quasi-stationary fault contacts are known to enhance static friction. However, its role in modulating dynamic friction remains poorly understood. Here, we investigate how quasi-stationary contacts influence subsequent fault slip. We perform slide-hold-slide experiments on simulated gabbro gouge with distilled water at temperatures ranging from 25 to 400 °C and a pore pressure of 30 MPa. At 300 °C, prolonged holds (≥ 3000 s) induce significant post-hold frictional weakening and enhanced fault stability (i.e., decrease of the magnitude of stress drop). The post-hold frictional weakening correlates with hold duration, fluids and ambient temperature, suggesting the involvement of thermally-activated, time-dependent processes on the contact surfaces. Microanalytical investigations reveal the formation of clay minerals via hydrothermal alteration in the experimental fault. Our findings demonstrate that short-term hydrothermal processes occurring during static holds may leave persistent mineralogical imprints, thereby modifying fault strength and slip behavior.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119893"},"PeriodicalIF":4.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146185585","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":"New early cretaceous paleomagnetic results from the Northern Lhasa Terrane and their tectonic implications","authors":"Zijian Li ,&nbsp;Yalin Li ,&nbsp;Xiaodong Tan ,&nbsp;Zhongpeng Han ,&nbsp;Shuai Li ,&nbsp;Xingduo Ma ,&nbsp;Ying Liang ,&nbsp;Xu Zhang ,&nbsp;Jizheng Song ,&nbsp;Zihao Zhou ,&nbsp;Yuanxiang Li ,&nbsp;Shuqing Miao ,&nbsp;Chengshan Wang","doi":"10.1016/j.epsl.2026.119859","DOIUrl":"10.1016/j.epsl.2026.119859","url":null,"abstract":"<div><div>The tectonic evolution of central Tibet was shaped by multiple collisions, notably the Cretaceous collision between the Lhasa and Qiangtang terranes and the subsequent India–Asia collision. Yet, uncertainties in the Early Cretaceous paleogeography of the Lhasa terrane still obscure their timing and mechanisms. Here we present new paleomagnetic data derived from Early Cretaceous sedimentary and volcanic sequences in the northern Lhasa terrane. Field tests, rock magnetic experiments, and petrographic analyses demonstrate that the characteristic remanent magnetizations are primary. Sedimentary rocks show shallower mean directions than volcanic rocks, but Elongation–Inclination analysis effectively corrects this bias, producing consistent paleomagnetic estimates. The combined dataset defines a paleomagnetic pole at 68.6°N, 348.7°E (A₉₅ = 1.4°), indicating a paleolatitude of 25.5° ± 1.4°N for the Bangoin region during the interval of 114–113 Ma. Comparison with the Asian apparent polar wander path suggests 560 ± 200 km of intracontinental shortening since the late Early Cretaceous. Integrated with published paleomagnetic data and geological evidence, these findings indicate that the central and eastern Lhasa terrane had already collided with the Qiangtang terrane at approximately 30°N by ∼114 Ma, with subsequent westward propagation of the collision. Moreover, during the late Early Cretaceous, the southern margin of Asia was situated at a paleolatitude exceeding 20°N, in contrast to the coeval low-latitude setting (≤10°N) of the Trans-Tethyan Subduction Zone. This significant paleolatitudinal disparity supports an intra-oceanic equatorial arc–continent collision at ∼55 Ma and provides new constraints on the timing and geodynamic mechanisms of the India–Asia collision.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119859"},"PeriodicalIF":4.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146185576","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":"Triple oxygen isotope signatures of cherts record pore-fluid composition and temperature across the opal-CT to quartz transition","authors":"Oskar Schramm ,&nbsp;Katharina Ebert ,&nbsp;Patrick J. Frings ,&nbsp;Andreas Pack ,&nbsp;Tommaso Di Rocco ,&nbsp;Volker Karius ,&nbsp;Nils Keno Lünsdorf ,&nbsp;Dieter Korn ,&nbsp;Daniel Herwartz ,&nbsp;Michael Tatzel","doi":"10.1016/j.epsl.2026.119889","DOIUrl":"10.1016/j.epsl.2026.119889","url":null,"abstract":"<div><div>Sedimentary chert is the diagenetic end-product of amorphous silica that first transforms to opal-cristobalite/tridymite (CT) and subsequently to microcrystalline quartz via dissolution and reprecipitation reactions. The ¹⁸O/¹⁶O and ¹⁷O/¹⁶O ratios (i.e. triple oxygen isotope composition, δ¹⁸O, Δ’¹⁷O) of cherts record equilibration with the pore fluids at the diagenetic temperatures prevalent during the opal-CT to quartz transition. Pore fluid oxygen isotope gradients emerge when secondary minerals, e.g. clay minerals form during burial. Here, we demonstrate that chert triple oxygen isotope compositions not in equilibrium with modern like seawater can be explained by changes in pore water δ¹⁸O and Δ’¹⁷O without invoking any alteration or different paleo-seawater. We demonstrate this using a suite of Carboniferous cherts that we collected from the same stratigraphic level at five locations in the Rhenish Massif, Germany, spanning a range of inferred burial rates. The precursor sediments were deposited in the marine Rhenohercynian Basin and were subject to peak diagenetic temperatures of up to 279 ± 37 °C upon folding and thrusting. Their triple oxygen trajectory cannot be explained by any realistic paleo-seawater composition. Using our numerical silica diagenesis model, we find that the chert isotope signatures are explained by a formation temperature between 20–35 °C and a pore fluid composition of -7 to -14‰ δ¹⁸O consistent with a pore fluid gradient of -13.5 ‰ km^-1 across the Rhenohercynian Basin. This suggests that triple oxygen isotope compositions of chert systematically record near-surface conditions and therefore represent a valuable resource for paleoenvironmental research.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119889"},"PeriodicalIF":4.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146185575","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}