Geochemistry Geophysics Geosystems最新文献

{"title":"Role of Post-Collisional Magmatism in Continental Growth and Reworking Since the Late Archean","authors":"Dongjian Ouyang,&nbsp;Ross N. Mitchell,&nbsp;Peng Peng,&nbsp;Jinghui Guo,&nbsp;Qiuli Li","doi":"10.1029/2026GC013327","DOIUrl":"https://doi.org/10.1029/2026GC013327","url":null,"abstract":"<p>The mechanisms responsible for the formation and compositional evolution of continental crust remain central questions in Earth science. Post-collisional magmatism is widely preserved in the continental record; however, its contribution to crustal growth may be underestimated because enriched isotopic signatures obscure juvenile mantle input. Here, we present integrated whole-rock geochemical, Sm–Nd–O isotopic, and zircon U–Pb–Hf–O isotopic data for ∼2.49–2.45 Ga post-collisional mafic and felsic rocks from the Daqingshan Terrane, western North China Craton. The Daqingshan mafic rocks lack diagnostic arc-like signatures, show no pronounced depletion in high-field-strength elements, and have relatively radiogenic Nd–Hf isotopic compositions, indicating derivation from a depleted but variably hybridized mantle source. Systematic mafic–felsic isotopic correspondences, together with large isotopic variations (whole-rock <i>ε</i>_Nd(<i>t</i>) = −3.1 to +4.5, zircon <i>ε</i>_Hf(<i>t</i>) = −11.2 to +6.4, zircon <i>δ</i>¹⁸O = 2.9‰ to 9.2‰), indicate that the felsic batholiths were genetically linked to the mafic magmas and formed through variable combinations of mafic magma differentiation, magma hybridization, and crustal anatexis. Hf–O isotope mixing and mass-balance estimates suggest that juvenile mantle-derived material accounts for at least ∼36% of the exposed felsic–intermediate assemblage and may approach ∼50% when unexposed mafic underplates are considered. Comparable magmatic timescales and mafic compositional trajectories in other collisional belts suggest that similar processes may have operated more widely. These results identify post-collisional mafic magmatism as a cryptic mechanism for continental crust preservation, growth, and reworking since the late Archean.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013327","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149206103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Benchmarking Multiple Methods for the Spectral Analysis of Seafloor Morphology","authors":"B. Bauer,&nbsp;I. Grevemeyer,&nbsp;L. Rüpke,&nbsp;P. Huybers,&nbsp;A. Dannowski,&nbsp;M. Riedel,&nbsp;M. Frank,&nbsp;K. Hoernle,&nbsp;C. Langmuir,&nbsp;H. Kopp","doi":"10.1029/2026GC013359","DOIUrl":"https://doi.org/10.1029/2026GC013359","url":null,"abstract":"<p>The influence of glacial sea-level changes on the quasi-periodic spacing of abyssal hills has remained controversial for over a decade. Spectral analyses of seafloor morphology have yielded contrasting conclusions regarding whether periodicities associated with orbital Milankovitch forcing are recorded in abyssal hill spacing, raising questions about the sensitivity of results to methodological choices. An important component of spectral analysis is prewhitening, or methods by which to mitigate the effects of the strong red background spectrum, characteristic of seafloor bathymetry. Various methods can have first-order implications for the inferred significance of spectral peaks. Here we benchmark four approaches for analyzing bathymetric spectra to detect periodicities in seafloor morphology. Through synthetic testing, we confirm that spectral analysis is better performed using a multitaper approach relative to other standard approaches and that a leveled spectrum can be derived by either prewhitening with an autoregressive and moving-average model or by leveling with a von Kármán model. Application of the different methods to previously published and newly analyzed bathymetric data sets shows that methodological choices substantially influence the inferred significance of spectral peaks, even when similar spectral features are present. Our results provide practical guidance for selecting appropriate spectral methods and bathymetric data sets when testing hypotheses linking glacial/interglacial sea-level variations to seafloor morphology and establish a methodological framework for future investigations of periodic signals in oceanic crustal accretion.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013359","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149206102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Tracing Orogenic Evolution From Multi-Detrital Mineral Records: U-Pb Geochronology and Trace-Element Constraints From Glacial Diamictites","authors":"Lijun Wang,&nbsp;Shoufa Lin,&nbsp;Wenjiao Xiao,&nbsp;Cees R. van Staal,&nbsp;Chris R. M. McFarlane,&nbsp;Zhijun Niu,&nbsp;Fang Song,&nbsp;Qihang Wu","doi":"10.1029/2026GC013024","DOIUrl":"https://doi.org/10.1029/2026GC013024","url":null,"abstract":"<p>Integrating multiple detrital mineral systems provides a powerful framework for reconstructing source-region tectonothermal evolution because different minerals record complementary aspects of magmatic and metamorphic processes. Glacial diamictites are particularly valuable for this approach because extensive glacial erosion can sample broad source regions and diverse crustal levels while minimizing chemical weathering and preserving unstable mineral phases. Here, we present integrated U-Pb geochronological and trace-element analyses of detrital apatite and rutile from Marinoan-aged glacial diamictites of the Yangtze Block in South China and combine these data with existing zircon data sets. Detrital apatite records dominant mafic and I-type magmatism between ∼970 and 650 Ma, with more evolved peraluminous signatures appearing at 850–820 Ma, broadly consistent with declining zircon εHf(t) values. Detrital rutile reveals dominant Neoproterozoic (∼970–790 Ma) and subordinate Paleoproterozoic (2.2–1.8 Ga) metamorphic signatures. Zr-in-rutile thermometry indicates temperatures of 480°C–980°C, including a distinct ∼950–820 Ma high-pressure, low-temperature population consistent with blueschist- to eclogite-facies conditions. These data record major tectonic transitions within the Panxi-Hannan orogen of the northwestern Yangtze Block, from an intra-oceanic arc (970–880 Ma) to a continental arc (870–790 Ma), followed by regional extension after 790 Ma. The cessation of rutile and metamorphic apatite ages coincides with the onset of regional extension in the source orogen. The ∼950–820 Ma cold-subduction signature expands the global record of Tonian low-geothermal-gradient metamorphism. Our results demonstrate that integrating multiple detrital mineral systems yields a more complete tectonic history than any single provenance proxy.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013024","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149206104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Mantle Transition Zone Constraints on Slab Penetration and Slab-Edge Mantle Flow Beneath the Kamchatka Peninsula","authors":"Muchen Sun,&nbsp;Yangyang Liao,&nbsp;Stephen S. Gao,&nbsp;Kelly H. Liu,&nbsp;Youqiang Yu","doi":"10.1029/2026GC013110","DOIUrl":"https://doi.org/10.1029/2026GC013110","url":null,"abstract":"<p>Numerous seismic studies have reported the absence of a resolvable subducted slab beneath parts of northern Kamchatka, though the mechanism for this anomaly remains debated. We utilize 1,696 P-to-S receiver functions to image the mantle transition zone (MTZ) beneath the Kamchatka Peninsula and surrounding areas. Beneath southwestern Kamchatka, the thickened MTZ and the pronounced 520-km discontinuity support cold Cretaceous Pacific slab-related material with possible hydration within the MTZ. In contrast, significant MTZ thinning is observed beneath northern Kamchatka, where previous tomography studies also show slab absence in the shallow upper mantle. This argues against the presence of a large cold detached slab remnant in the sampled MTZ. Combined with previous seismic anisotropy, tomography, and geodynamic constraints, our results support a model that thermally buoyant mantle material flows around the slab edge and ascends into the upper mantle, forming a semi-toroidal mantle flow. The inferred slab-edge mantle flow may extend to at least MTZ depths and provide a plausible setting for progressive modification and weakening of the slab margin beneath northern Kamchatka, while allowing slab penetration farther southwest. These observations highlight the first-order role of slab–mantle interaction in controlling slab fate at convergent margins.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013110","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149206138","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Full Waveform Modeling of Bridgmanite Fabric-Induced Seismic Discontinuities in the Mid-Mantle: Implications for Double Underside Reflections Beneath Subduction Zones","authors":"John Keith Magali,&nbsp;Ye Yuan,&nbsp;Takumi Matsunaga,&nbsp;Christine Thomas","doi":"10.1029/2026GC013253","DOIUrl":"https://doi.org/10.1029/2026GC013253","url":null,"abstract":"<p>Mid-mantle (660–2,000 km) seismic observations are commonly attributed to thermo-chemical heterogeneities or phase transitions, yet many observed features remain difficult to reconcile with these mechanisms alone. It has been shown that the depth-dependent behavior of bridgmanite deformation generates a strain-induced seismic discontinuity around slabs at depths broadly consistent with these observations. Its signal in the data, however, remains largely unknown. Here, we investigate the detectability of anisotropic discontinuities produced by the (100)[001]/(010)[100] slip transition in bridgmanite beneath a subduction zone by combining geodynamic and mantle fabric modeling. We then employ full waveform simulations, and then process synthetics using array seismological methods. Our results show that the anisotropic discontinuity is detectable and can be clearly distinguished from reflections at the slab-mantle interface. For horizontally flattened slab morphologies, the reflector associated with the anisotropic discontinuity consistently exhibits positive polarity for all propagation azimuths, implying that the anisotropic layer formed beneath the slab acts as a seismically slow region. We further assess the implications of this mechanism in real data using two examples of double reflections beneath Alaska-Aleutian and Middle America. In both cases, the <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mi>S</mi>\u0000 <mn>1000</mn>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${mathrm{S}}^{1000}$</annotation>\u0000 </semantics></math>S phase corresponding to the deeper reflector exhibits positive polarity that is difficult to explain either in terms of a thermo-chemical layer or mineral phase transitions, but is consistent with the anisotropic discontinuity interpretation. These results suggest that mantle deformation plays an important role in the formation of mid-mantle structures that may not exhibit velocity and density contrasts across their boundaries, but can nonetheless generate observable reflections.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013253","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149206071","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Geodynamic Significance of Intraplate Basaltic Magmatism From the Western Mediterranean Region","authors":"Chia-Yu Tien,&nbsp;Nicky White,&nbsp;Megan Holdt,&nbsp;John Maclennan,&nbsp;Benedict Conway-Jones","doi":"10.1029/2025GC012840","DOIUrl":"https://doi.org/10.1029/2025GC012840","url":null,"abstract":"<p>Dynamic topography changes as mantle convection evolves, making its past surface expression difficult to reconstruct. Widespread Neogene-Quaternary intraplate basaltic magmatism across the Western Mediterranean Region allows us to test whether dated basalts preserve the mantle thermal structure responsible for regional dynamic support. We combine major, trace, and rare earth element (REE) analyses and modeling from six volcanic provinces with calibrated earthquake tomographic models and residual topographic and bathymetric measurements. The geochemical data set includes both newly acquired and published analyses. Rare earth element inverse modeling of samples least affected by lithospheric-mantle influence indicates that melting occurred beneath lithosphere typically 60–70 km thick and at asthenospheric potential temperatures ranging from approximately ambient to 50°C above ambient mantle. These estimates agree with independent tomographic constraints. Dynamic support calculated from the inferred thermal structure is also consistent with measured residual anomalies. Lithospheric thinning accounts for most of the largest positive anomalies of approximately 0.5 km without requiring large asthenospheric temperature anomalies. The agreement demonstrates that Western Mediterranean intraplate basaltic magmatism records upper-mantle thermal structure capable of generating regional surface support and provides a basis for reconstructing past mantle conditions and transient dynamic topography from dated basalts.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012840","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149205871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Subduction Recycling and Closure of the Paleo-Asian Ocean in the Beishan Orogen: Constraints From the Niujuanzi Ophiolitic Mélange and Associated Intrusions","authors":"Yujia Song,&nbsp;Xijun Liu,&nbsp;Yao Xiao,&nbsp;Honghu Zeng,&nbsp;Pengde Liu","doi":"10.1029/2026GC013230","DOIUrl":"https://doi.org/10.1029/2026GC013230","url":null,"abstract":"<p>Ophiolitic mélanges and associated intrusions provide key archives for reconstructing the evolution of ancient ocean basins and subduction-related mantle modification. The Hongliuhe–Niujuanzi–Xichangjing ophiolitic mélange in the central Beishan Orogen preserves important records of the Paleo-Asian Ocean, but the timing of oceanic subduction, terminal closure, and subsequent postcollisional reworking in the Niujuanzi remain debated. Here we integrate field observations, zircon U–Pb geochronology, whole-rock and mineral geochemistry, and Sr–Nd–Hf–Pb isotopic data from the newly dated and geochemically characterized ophiolitic rocks and associated dioritic to granodioritic intrusions. Zircon U–Pb ages define three Paleozoic magmatic episodes: Early Silurian diorites at 435–427 Ma, Late Silurian ophiolitic gabbros at 423–418 Ma, and Early Devonian granodiorites at ca. 403 Ma. The diorites display continental arc-like geochemical signatures and were derived from a lithospheric mantle source modified by slab-derived fluids. The gabbros show N-MORB-like affinities with weak subduction-related enrichment, consistent with formation in an SSZ setting. The granodiorites were generated mainly by partial melting of the ancient lower crust with minor mantle input, recording a transition to postcollisional extension. Silicate in situ Pb isotopes exhibit a temporal shift toward Indian MORB-like signatures from the Early Silurian to Early Devonian, indicating progressive mantle source modification by recycled subduction components. These results demonstrate that the Niujuanzi basin remained active until the Late Silurian, closed by the end-Silurian, closed during the latest Silurian to the earliest Devonian (ca. 418 Ma), and transitioned to postcollisional extension in the Early Devonian, providing a refined geodynamic model for the central Beishan Orogen.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013230","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149205347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Flip-Flop Detachments Require Moderate Strength Contrasts Between Fault Zone and Fault Blocks","authors":"A. Demont,&nbsp;J.-A. Olive,&nbsp;M. Cannat","doi":"10.1029/2026GC013177","DOIUrl":"https://doi.org/10.1029/2026GC013177","url":null,"abstract":"<p>Large-offset detachment faults frequently occur at slow- and ultraslow-spreading mid-ocean ridges, especially where magma supply is limited. Observations show that detachments at ultraslow ridges often alternate in polarity (“flip-flop” regime), but the mechanical controls governing their formation remain poorly understood. Here we use two-dimensional thermo-mechanical models to systematically investigate how frictional and cohesive strength contrasts between fault zones and surrounding lithosphere influence faulting styles in nearly amagmatic ultraslow ridge environments. Our models incorporate a self-evolving thermal structure and Mohr-Coulomb elasto-plasticity with friction and cohesion weakening during deformation, along with parameterizations of fluid circulation. We identify three primary deformation regimes: distributed minor faults, sequential flip-flop detachments, and persistent runaway detachments. Flip-flop detachments emerge under moderate frictional and cohesive weakening, where faults alternate polarity as antithetic faults periodically replace dominant detachments. Persistent runaway detachments, as produced by models, show excessive cross-axis migration that is not typically observed in nature. A strong, viscous lower lithosphere promotes distributed deformation and hinders the onset of persistent detachments. Analytical force balance modeling further shows that flip-flop faulting occurs when fault strength loss balances the defocusing effect of lithospheric flexure, which necessitates moderate frictional weakening (∼0.2–0.3) achievable via serpentinization of the fault zone. In contrast, runaway detachments require further weakening. These findings clarify the mechanical conditions driving flip-flop detachment formation and highlight how relatively modest rheological contrasts between intact and deformed lithosphere enable large-offset faulting at ultraslow mid-ocean ridges.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013177","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149205343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Global Implications of Terrain-Induced Bias in Paleomagnetic Data From 3D Forward Modeling of Mt. Etna","authors":"A. E. Hendrickx,&nbsp;C. Thieulot,&nbsp;L. V. de Groot","doi":"10.1029/2026GC013098","DOIUrl":"https://doi.org/10.1029/2026GC013098","url":null,"abstract":"&lt;p&gt;In paleomagnetism, records of paleosecular variation (PSV) on centennial timescales are often based on magnetic measurements from lava flows. However, samples from recent flows that cooled in known magnetic fields often fail to produce the expected paleomagnetic directions, and samples from the same flow often show large within- and between-site dispersion. Direct measurements of local magnetic anomalies in volcanic terrain showed that the topography of the underlying lava flow distorts the magnetic field. Such Magnetic Terrain Effects (MTEs) are subsequently recorded by overlying flows and can account for much of this dispersion. Here we present a data-independent numerical model capable of simulating topographies and predicting magnetic fields over highly magnetized rocks. Using this Python-based forward model and high-resolution Digital Elevation Models, we replicate field measurements taken on Mt. Etna. The computed anomalies often match the location and shape of the measured results, showing intensity deviations up to 14 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;μ&lt;/mi&gt;\u0000 &lt;mi&gt;T&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${upmu }mathrm{T}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, inclination deviations up to &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;mo&gt;°&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $12{}^{circ}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, and declination deviations up to &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;14&lt;/mn&gt;\u0000 &lt;mo&gt;°&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $14{}^{circ}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, compared to the measured deviations of 13 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;μ&lt;/mi&gt;\u0000 &lt;mi&gt;T&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${upmu }mathrm{T}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;19&lt;/mn&gt;\u0000 &lt;mo&gt;°&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $19{}^{circ}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;21&lt;/mn&gt;\u0000 &lt;mo&gt;°&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $21{}^{circ}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, respectively. Our findings suggest that MTEs must be considered in paleomagnetic interpretations: while distinguishing between MTE and PSV is nearly impossible in individual measurements when the underly","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013098","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149146170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Multistage Evolution and Inheritance in a Magma-Poor Conjugate Margin: Insights From Serpentinized Peridotites of the Newfoundland Margin (ODP Hole 1277A)","authors":"A. Secchiari,&nbsp;M. Godard,&nbsp;A. Montanini","doi":"10.1029/2026GC013203","DOIUrl":"https://doi.org/10.1029/2026GC013203","url":null,"abstract":"<p>The nature of mantle sections exhumed at magma-poor rifted margins remains poorly constrained, largely because direct sampling of mantle in modern passive margins is exceptionally rare. The Iberia–Newfoundland system is unique in providing drilled mantle rocks on both conjugate margins, offering an unprecedented glimpse into mantle heterogeneity across an entire rift system. Here we present new in situ major and trace element data from highly serpentinized peridotites recovered at ODP Hole 1277A (Newfoundland margin). The samples display mylonitic textures and are strongly depleted in clinopyroxene (≤2 vol.%). Despite pervasive serpentinization, relict mantle minerals retain evidence of high melt extraction degrees, as indicated by Al₂O₃-poor orthopyroxene (2.36–3.19 wt.%) and orthopyroxene trace element systematics. Geochemical modeling of orthopyroxene REE compositions indicates ≥14% melt extraction initiated in the garnet stability field, likely predating the Jurassic rifting. Following depletion, the mantle was locally overprinted by melt-rock interaction, as highlighted by high and variable spinel Cr#, REE disequilibrium in coexisting pyroxenes, and clinopyroxene with atypical V-shaped REE profiles (La_N/Sm_N = 4.3). During Jurassic rifting, the Newfoundland margin mantle section was reactivated and deformed within lithospheric-scale shear zones, leading to mylonitization and exhumation. The refractory nature of the mantle likely promoted limited melt extraction and retention of these transient melts within the lithosphere, now preserved as spinel-pyroxene symplectites. Subsequent cooling enabled hydration at ∼500–600°C and ultimately pervasive serpentinization. These results highlight that the pre-rift evolution of the lithospheric mantle exerts a primary control on the evolution of magma-poor rifted margins.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013203","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149146381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}