Geochemistry Geophysics Geosystems最新文献

{"title":"Uranium Addition and Loss in Serpentinites: The Potential Role of Iron Oxides","authors":"Emily H. G. Cooperdock,&nbsp;Juan Carlos de Obeso,&nbsp;Frank J. Pavia","doi":"10.1029/2025GC012353","DOIUrl":"10.1029/2025GC012353","url":null,"abstract":"<p>Fluid-mobile uranium serves as a tracer for water-rock alteration in serpentinized mantle rocks, which constitute an important uranium reservoir. However, the mechanism for uranium addition, where uranium is hosted, and the stability of the uranium enriched material during subduction is not settled. We use geochemistry data from marine (mid-ocean ridge and fracture zone, fore-arc, fore-arc muds) and subaerially exposed (subducted, obducted, orogenic) serpentinites to show that uranium enrichment varies systematically with tectonic setting and depth from the seafloor. Only the upper ∼100 m of drilled and dredged serpentinites from marine settings contain ≥0.1 μg/g uranium enrichment, which does not correlate with the degree of serpentinization. Other settings (deeper marine samples, subducted, obducted and/or orogenic serpentinites) do not show the same degree of uranium enrichment, suggesting that uranium was lost or never gained. We use these data to argue that uranium addition requires oxidizing—bearing fluids and that uranium enrichment can be used as an indicator of these conditions. To understand where uranium is hosted, we show that uranium is enriched in samples with bulk rock Fe³⁺/Fe_tot ≥ 0.6 and appears to be buffered at a maximum uranium concentration of ∼1 μg/g. We explore potential mineral hosts for uranium in highly enriched serpentinites and propose that Fe-(oxyhydr)oxides (e.g., hematite, goethite) formed during weathering and/or carbonation could be under-appreciated hosts for uranium in serpentinized systems. We use these results to explore implications for uranium cycling and uranium isotope fractionation during subduction.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012353","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144935069","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":"The Magnetic Fingerprint of Pulsed Granite Magma Emplacement and Alteration: Slaufrudalur Pluton, Iceland","authors":"O. Quintela,&nbsp;S. Burchardt,&nbsp;T. Mattsson,&nbsp;B. Almqvist,&nbsp;C. Stevenson,&nbsp;W. McCarthy,&nbsp;B. V. Óskarsson,&nbsp;I. Pitcairn,&nbsp;E. Rhodes,&nbsp;T. Witcher,&nbsp;S. H. M. Greiner,&nbsp;B. Latimer","doi":"10.1029/2025GC012199","DOIUrl":"10.1029/2025GC012199","url":null,"abstract":"<p>Magma reservoirs typically form through the incremental emplacement of smaller magma pulses over extended timescales. Pulsed reservoir growth significantly impacts a magma body's temperature evolution, chemical differentiation potential, and the probability, scale, and timing of volcanic eruptions. Moreover, the addition of thermal energy and magmatic fluids reheat and hydrothermally alter previously emplaced magma. Consequently, it may be difficult to distinguish individual magma pulses in exposed solidified intrusions (plutons), obscuring evidence of magma body construction and evolution. In this study, we employ geological mapping combined with petrofabric and Anisotropy of Magnetic Susceptibility (AMS), Anisotropy of Anhysteretic Remanent Magnetization (AARM), hysteresis, First-Order Reversal Curves (FORCs) and susceptibility versus temperature analyses to investigate pulsed magma emplacement and its consequences in terms of fabric overprinting and hydrothermal alteration within the Slaufrudalur pluton in Southeast Iceland. The field mapping documents distinct emplacement styles, including magma ascent in marginal zones, subhorizontal sheet emplacement, and bulk intrusion below the sheets. The AMS fabrics show high <i>K</i>_<i>m</i> values (∼1 × 10⁻² SI), but overall weak degrees of anisotropy (<i>P</i>_<i>j</i> &lt; 2%). The weak magnetic fabrics reflect the destructive interference between the magnetite fabric and the fabric of hematite and iron hydroxides. Later, pulses of magma are less oxidized, which indicates that the alteration was caused by volatile release from magma that intruded below already emplaced magma. Our results demonstrate that rock magnetic data provide a novel approach to detecting magma pulse interactions and associated alteration in plutons, offering insights into magma body dynamics.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012199","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144927262","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":"Ferrimagnetic Structure of 3C Pyrrhotite (Fe7S8) From Neutron Diffraction","authors":"Chin-Wei Wang,&nbsp;Chorng-Shern Horng,&nbsp;Andrew P. Roberts","doi":"10.1029/2025GC012470","DOIUrl":"10.1029/2025GC012470","url":null,"abstract":"<p>Pyrrhotite is a paleomagnetically important magnetic mineral in many geological settings. It forms numerous polytypes with different stacking patterns of the NiAs structure along the crystallographic <i>c</i> axis to produce different vacancy-ordered superstructures. Monoclinic 4C pyrrhotite (Fe₇S₈) is the best-known ferrimagnetic member of the pyrrhotite family; the magnetic properties of other pyrrhotite polytypes remain largely unknown. Recent discovery of the importance of magnetism in 3C pyrrhotite (Fe₇S₈) in methanic sedimentary environments makes it important to establish its magnetic structure and magnetic properties. We present powder neutron diffraction results at low and high temperatures, which enable determination of the magnetic structure of 3C compared to 4C pyrrhotite. We find that 3C pyrrhotite is a collinear ferrimagnet with a saturation magnetization of 2.714(3) μ_B at 300 K, which is less than the 3.048(3) μ_B determined for our measured 4C pyrrhotite sample. Our analyses indicate iron deficiency in both studied samples, which likely reduces the expected net magnetization compared to the respective fully vacancy ordered cases. The studied 3C pyrrhotite is thermally unstable above 390 K. Demonstration of the ferrimagnetism of 3C pyrrhotite, which has contrasting magnetic properties to 4C pyrrhotite, has important implications for interpreting sedimentary magnetic signals. This work indicates a need to document more fully the magnetic properties of pyrrhotite polytypes, including 3C pyrrhotite with variable vacancy ordering.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012470","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144927172","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":"Disentangling Partial Melting and Crustal Recycling Signatures in Ocean Island Basalts With Multivariate Statistics","authors":"Zachary T. Eriksen,&nbsp;Andreas Stracke","doi":"10.1029/2025GC012390","DOIUrl":"10.1029/2025GC012390","url":null,"abstract":"<p>Ocean island basalts (OIB) provide valuable constraints on mass exchange between the mantle and crust. When appropriate compositional data transformations are applied, multivariate analyses of OIB compositions can be used to infer mantle source heterogeneity and elucidate its driving processes. We apply Principal Factor Analysis (PFA) to log-ratio transformed global OIB data, resolving latent variables (“factors”) which show that melt degree and recycled continental crust contributions are the dominant factors shaping OIB compositions. Recycled oceanic crust (ROC) signals are initially masked by variable degrees of partial melting. But by filtering for samples formed under similar melting conditions and reapplying PFA, we resolve an ROC factor, distinct upper and lower continental crust (UCC and LCC) factors, a depth-of-melting factor, and a factor unique to Hawaii. Visualizing OIB samples in factor space (“biplots”) establishes a new framework for evaluating crustal recycling processes. In general, continental materials (UCC + LCC) are subducted together with oceanic crust and overwhelmingly shape the record of mantle heterogeneity sampled by OIB. However, rare geodynamic conditions may promote recycling of atypical combinations of recycled materials. The Azores, for example, uniquely sample mantle with UCC (+ROC) components devoid of LCC, while St Helena and Austral-Cook (canonical “HIMU”) reflect the striking absence of recycled continental input. Moreover, Northern and Southern Hemisphere hotspots appear to sample different combinations of continental materials. Overall, the proportion and type of continental materials in OIB mantle sources apparently depends on their availability in a given paleotectonic environment and the physicochemical parameters of past subduction.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 9","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012390","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144927170","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":"Structural Architecture of the Cenozoic Kallianos (Post-?)Orogenic Vein-Hosted Au-Ag-Te Deposit and Its Relationship to the North Cycladic Detachment System, Greece","authors":"L. Hamel,&nbsp;T. A. Ducharme,&nbsp;D. A. Schneider,&nbsp;B. Grasemann","doi":"10.1029/2025GC012501","DOIUrl":"10.1029/2025GC012501","url":null,"abstract":"<p>The Kallianos Au-Ag-Te deposit is a Cenozoic orogenic-style deposit on Evia, hosted in the Cycladic Blueschist Unit. Integrated field observations and isotopic data illustrate a connection between the structural architecture that hosts mineralization in the deposit and the regional stress field associated with a crustal-scale detachment, the North Cycladic Detachment System, implying a first-order paragenetic relationship to post-orogenic extension. Mineralized and barren veins occur alongside parallel faults and joints in two distinct orientations, each locally defining conjugate or en-echelon sets. Younger sub-vertical tension gash sets (V₂, V₃) cross-cut older transposed and boudinaged mineralized veins (V₁). Sulfide mineralization is hosted in steeply dipping cm-scale qz ± cal ± ab V₃ veins. Structural relationships show cross-cutting of NW-striking V₂ by NNW-striking V₃ veins. The latter two vein sets opened orthogonal to the NE-trending stretching lineations, associated with brittle-ductile shear bands indicating top-NE kinematics, underscoring their relationship to crustal extension accommodated by the detachment system. Carbon-Oxygen isotope data from vein calcite (δ¹³C: −3.31–0.40‰ and δ¹⁸O: 14.43–20.78‰) reflect fluid mixing with the graphite-bearing wall rock. White mica ⁴⁰Ar/³⁹Ar and in situ ⁸⁷Rb/⁸⁷Sr geochronology suggest that the host rock accommodated greenschist facies deformation between c. 20–31 Ma, whereas hydrothermal mica in vein haloes indicates fluidization and vein sealing at c. 21–26 Ma. Zircon (U-Th)/He dates reveal that the rocks cooled below ∼200°C at c. 11–14 Ma, corresponding to the exhumation of the deposit into the brittle crust. A comprehensive study of this younger, mostly undeformed post-orogenic deposit can help elucidate the tectonic setting of older, polydeformed orogenic gold deposits.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012501","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144894264","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":"The Role of Peridotite for Oceanic Volcanism","authors":"Andreas Stracke,&nbsp;Vincent J. M. Salters","doi":"10.1029/2025GC012463","DOIUrl":"10.1029/2025GC012463","url":null,"abstract":"<p>The complementary products of oceanic crust formation are compositionally variable melt-depleted peridotites. Together with the oceanic crust, the melt-depleted peridotites are continuously recycled back into the mantle. Before remelting today, after some 10⁸–10⁹ years of recirculation within the mantle, the peridotites have developed extremely variable radiogenic isotope ratios, documented by εHf extending to values of &gt;450 in abyssal peridotites. Peridotite isotope ratios thus range far beyond those observed in their melting products, basalts formed at mid-ocean ridges or ocean islands (εHf &lt; 25). Here, we stress that such compositionally heterogeneous, and variably dense melt-depleted peridotites are the predominant component of Earth's mantle. We discuss a first-order approach to assess how basalts reflect the chemical and isotopic signatures of the individual components of their heterogeneous mantle sources. Generally, the incompatible element compositions of basalts are dominated by melts from minor, incompatible element enriched components, foremost recycled crust. But oceanic basalts also inherit characteristic isotopic signatures from the predominant, trace element-poor, and variably dense peridotites. The covariation between variable peridotite composition and density establishes a critical link between basalt chemistry and the thermochemical buoyancy forces that control mantle upwelling and basalt production rates under mid-ocean ridges or ocean islands. Exploiting strategies to relate geochemical and geophysical observables determined by the inherent heterogeneity of peridotite will therefore lead to a new, integrative understanding of the chemical geodynamics of the Earth's mantle-crust system.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012463","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144869443","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":"Detection and Analysis of Aleutian Arc Seismicity (2022–2023) Using an Autonomous Hydrophone Array","authors":"Vaibhav Vijay Ingale,&nbsp;Gabrielle Tepp,&nbsp;Robert P. Dziak,&nbsp;Ross Parnell-Turner","doi":"10.1029/2025GC012320","DOIUrl":"10.1029/2025GC012320","url":null,"abstract":"<p>The Aleutian trench, extending from the Gulf of Alaska to Kamchatka, marks the subduction boundary between the Pacific and North-American plates. It hosts the Aleutian Islands, one of Earth's most significant volcanic arcs, with 52 historically active volcanoes. Given the long history of eruptions and strong earthquake-induced tsunamis that pose hazards to Aleutian communities, studying this area is essential for assessing geohazards and subduction zone processes. To investigate submarine volcanism and seismicity along the western Aleutian Islands, four autonomous underwater hydrophones (AUH) were deployed in June 2022 for 12 months ∼100 km north of Adak Island. The AUHs were moored at depth of ∼500 m in a diamond-shaped array with 10 km spacing. The AUHs recorded different types of acoustic signal packets (events), including long-duration (∼40 s) spindle-shaped T-phases with frequencies &lt;60 Hz, that are characteristics of tectonic earthquakes and short-duration (∼10 s), impulsive signals with a wide range of frequencies (40–100 Hz) were observed, peaking in activity during March 2023, that are associated with shallow seismic events. We characterized all hydroacoustic events by their temporal distribution, back-azimuths, rise time, and received level to establish acoustic signal categories based on the likely source mechanisms. By comparing hydroacoustic detections with a land-based earthquake catalog, we observe that short-duration events originated from seismic unrest beneath Tanaga Island. The temporal distribution of magnitudes and depths of seismic events, coupled with rise times and received levels of matched hydroacoustic signals, suggests that the seismic unrest is linked to magma transport at shallow depths beneath Tanaga Island.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012320","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144853757","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":"Crust-Mantle Interaction During Continental Deep Subduction: Evidence From Light Mo Isotopes in Post-Collisional Mafic Igneous Rocks From the East Kunlun Orogen","authors":"Qing-Chen Yang,&nbsp;Wei Fang,&nbsp;Li-Qun Dai,&nbsp;Li-Tao Ma,&nbsp;Zi-Fu Zhao","doi":"10.1029/2025GC012451","DOIUrl":"10.1029/2025GC012451","url":null,"abstract":"<p>It is intriguing whether and how crust-mantle interaction would proceed in continental subduction zones. Here, we report zircon U-Pb ages and Hf isotopes, major and trace elements, and Sr-Nd-Mo isotopes for Late Paleozoic mafic igneous rocks from the East Kunlun orogen (EKO). Zircon U–Pb dating of these rocks yields concordant ages of 384–387 Ma, corresponding to post-collisional magmatism in the EKO. The mafic rocks are characterized by arc-type trace element distribution patterns and slightly enriched Sr-Nd isotopes, indicating their derivation from a fertile mantle source with the involvement of crustal material. Their high Th/La ratios (0.28–0.77) are inconsistent with the recycling of typical oceanic crust but can be related to continental crust-derived melts with residual allanite during crustal anatexis. This is further strengthened by the similarity in Sr-Nd isotopes and zircon Hf isotopes between these mafic rocks and gneiss that represent ancient continental crustal components in the EKO. Notably, the post-collisional mafic rocks have variably low δ⁹⁸Mo values of −0.64‰ to −0.07‰. Combined with the enriched Sr-Nd isotopes and high Th/La features, it is inferred that the light Mo isotopic signatures are inherited from the deeply subducted continental crust. Given that continental crust is generally characterized by high δ⁹⁸Mo values of 0.10–0.40‰, the light Mo isotope compositions of the mafic rocks should be inherited from the previously dehydrated continental crust-derived melts. Our study highlights that the light Mo isotope features can be used to decipher the recycling of continental crust in collisional orogens.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012451","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144853758","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":"Preservation of Primary Si Isotope Signatures in Devonian Lahn-Dill-Type Iron Ores as Revealed by Femtosecond Laser Ablation","authors":"Grit Steinhoefel,&nbsp;Leanne Schmitt,&nbsp;Thomas Angerer,&nbsp;Thomas Kirnbauer,&nbsp;Sabine Klein","doi":"10.1029/2025GC012223","DOIUrl":"10.1029/2025GC012223","url":null,"abstract":"<p>Silicon isotopic ratios (expressed as δ³⁰Si) become established as a powerful tool to decipher the formation processes of quartz deposits throughout the Earth's history. In this study, we established a protocol for matrix-independent in situ Si isotopic analysis using ultraviolet femtosecond laser ablation (UV fs LA) coupled to multi-collector inductively coupled plasma mass spectrometry and applied this method to microcrystalline quartz in Lahn-Dill-type iron ores. Obtained results on “MPI-DING” silicate glasses using NIST SRM 610 as the calibration standard agree with excepted values within uncertainty, revealing an external reproducibility of ±0.2‰ (2 SD) for δ³⁰Si. Analysis of quartz and quartz-hematite microdomains in iron ores (Fortuna Mine, Rhenish Massif, Germany) show little differences in average δ³⁰Si ranging between −3.66 ±0.97‰ (2 SD) and −3.06 ±0.90‰ (2 SD) but exhibit an overall large variability between −4.56 and −2.04‰ on the micrometer-scale. Together with detailed petrographic and geochemical investigations (Schmitt et al., 2023, https://doi.org/10.1007/s00126-023-01218-3; 2024, https://doi.org/10.1007/s00126-024-01307-x), we conclude that strong kinetic effects during absorption of seawater Si on Fe-(oxyhydr)oxides of hydrothermal origin caused very negative and variable δ³⁰Si values in quartz precursors, which were preserved during diagenesis. The derived lower limit for Devonian seawater is −0.9‰ by assuming that the less negative δ³⁰Si values reflect precipitation closest to equilibrium conditions. This implies a prevalence of volcanogenic-derived Si in the Rhenohercynian Ocean, a back-arc basin characterized by high volcanic activity. Our results demonstrate the capability of matrix-independent Si isotope analysis by UV fs LA to unravel quartz formation processes.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012223","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144833218","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":"Transform Faulting in the Northern Red Sea Revealed by Ocean Bottom Seismometers Deployed in the Zabargad Fracture Zone","authors":"Hasbi Ash Shiddiqi,&nbsp;Laura Parisi,&nbsp;Eduardo Valero Cano,&nbsp;Margherita Fittipaldi,&nbsp;Nico Augustin,&nbsp;Guillaume Baby,&nbsp;Paul Martin Mai,&nbsp;Sigurjón Jónsson","doi":"10.1029/2025GC012253","DOIUrl":"10.1029/2025GC012253","url":null,"abstract":"<p>The Zabargad Fracture Zone (ZFZ), the largest rift-axis offset in the Red Sea, extends from 23.5°N to 26°N. It is covered by thick sedimentary layers that have hindered the ability of geophysical data sets to image the geometry of the normal faults and any potential transform faults. Passive seismology observations in the region have been limited to onshore recordings, leading to high uncertainty in earthquake locations and hampering detailed seismicity analyses. To address this limitation, we deployed a network of ocean bottom seismometers (OBSs) and land-based stations for a duration of 12 months. From these data, we built the first high-resolution earthquake catalog for this region of the Red Sea by applying a deep-learning-based algorithm to automatically detect earthquakes and pick P- and S-phases. To obtain reliable earthquake locations, we derived a 1-D seismic velocity model of the ZFZ. We established a calibration between <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>M</mi>\u0000 <mi>L</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${M}_{L}$</annotation>\u0000 </semantics></math> measured on land and on OBSs to overcome magnitude overestimation using the OBS data alone. Additionally, we computed focal mechanisms of selected events using waveform polarities and amplitude ratios. The hypocenter distribution reveals two major seismicity clusters, the North and South clusters. The North cluster highlights NW–SE trending normal faults reflecting the extensional tectonics of the Red Sea. In the South cluster, we discover a NE–SW transform fault, possibly in its early development stage and NW–SE normal faults. The depth of seismicity reveals variations in the brittle-ductile transition zone depth, with shallow depth in the north indicating higher shallow lithospheric temperature.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 8","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012253","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144843395","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}