Geochemistry Geophysics Geosystems最新文献

{"title":"Multiple Seamount Subduction and Lithological Variability Possibly Control Pore Fluid Pressure and Shallow Slow Earthquake Activity in Nankai Trough off Muroto","authors":"Paul Caesar M. Flores,&nbsp;Shuichi Kodaira,&nbsp;Gaku Kimura,&nbsp;Kazuya Shiraishi,&nbsp;Yasuyuki Nakamura,&nbsp;Gou Fujie,&nbsp;Tetsuo No,&nbsp;Yuka Kaiho","doi":"10.1029/2024GC011926","DOIUrl":"https://doi.org/10.1029/2024GC011926","url":null,"abstract":"<p>The clustered distribution of shallow slow earthquakes in the Nankai Trough has been attributed to different factors such as seamount subduction, pore fluid pressure, fluid migration, and sediment input. However, there is still a lack of comprehensive understanding of how these factors interact to generate slow earthquakes. We examined the seismic reflection profiles crossing four subducted seamounts off Muroto to understand how they deform the accretionary wedge. Along-trough seismic reflection profiles within the accretionary wedge were also used to infer the lithology of the underthrusted sediments. The seamounts are at different stages of subduction and their associated underplated sediments were identified. Comparison with published sandbox models indicates that the underplated sediments comprise fluid-rich trench fill sediments. Negative polarity decollement and transparent underthrust are observed off Muroto. The transparent underthrust is interpreted as mudstone, while stratified underthrust sediments in other regions are interpreted as turbidites. Comparing with previous numerical simulations, we propose the following deformational history: (a) subduction of the first seamount resulted in underplating of a large volume of fluid-rich trench fill sediments, (b) the underplated sediments are undergoing horizontal compression from subsequent subduction of the three seamounts resulting in high pore pressure consistent with previously reported low velocity zones, and (c) the horizontal compression may also result in fluid expulsion and these fluids migrate updip and get trapped because the mudstones serve as an impermeable cap. This mechanism accounts the aforementioned factors associated with slow earthquakes and likely controls the clustered distribution off Muroto.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011926","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143849077","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":"Assessment of Seawater Nd Isotope Signatures Extracted From Foraminiferal Shells and Authigenic Phases From Volcanogenic Sediments of the Adriatic Sea","authors":"Guohui Gao,&nbsp;Christophe Colin,&nbsp;Giuseppe Siani,&nbsp;Sophie Sepulcre,&nbsp;Rosella Pinna-Jamme,&nbsp;Frederic Haurine,&nbsp;Arnaud Dapoigny","doi":"10.1029/2024GC011992","DOIUrl":"https://doi.org/10.1029/2024GC011992","url":null,"abstract":"<p>The neodymium isotope signatures (<i>ε</i>Nd) of the authigenic fraction have been extensively used to reconstruct past seawater <i>ε</i>Nd and hydrological circulation. Among the various methods, sequential extraction of hydrogenic ferromanganese oxyhydroxides from bulk sediments represents a rapid and straightforward approach that may potentially induce artifacts due to the potential release of non-seawater-derived Nd during the extraction procedure. Here we investigated different methods for extracting past seawater Nd isotope compositions from a core collected in the Adriatic Sea whose tephra layers have been previously well documented. We analyzed <i>ε</i>Nd in planktonic foraminifera samples and in non-decarbonated sediment leachates obtained with three solutions commonly used in the context of the Mediterranean Sea: (a) 0.02 M hydroxylamine hydrochloride (HH) solution, (b) 1N HCl, and (b) a 25% (v/v) acetic acid (AA). Our results show that (a) the foraminiferal <i>ε</i>Nd remains unaffected by the diagenesis of tephra content; (b) all three methods indicate significantly more radiogenic <i>ε</i>Nd values in tephra levels (up to 1.5 <i>ε</i>Nd unit), which is attributed to tephra dissolution accounting for 2.7% of extracted Nd; (c) of the three leaching methods applied to samples with low tephra content, hydroxylamine hydrochloride (HH) yields <i>ε</i>Nd values that are more consistent with those obtained on planktonic foraminifera; (d) the <i>ε</i>Nd values of planktonic foraminifera in core MD90-917 remained constant indicating that the Adriatic deep water primarily reflects the local Nd isotope composition over the last 20 kyr.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011992","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143849102","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":"Pockmark Occurrence in the Northern Gulf of Mexico Influenced by Glacial Cycles and Hydrate Stability","authors":"A. Kumar,&nbsp;A. E. Cook,&nbsp;M. A. Lawal,&nbsp;A. Portnov,&nbsp;V. Lecours","doi":"10.1029/2024GC011781","DOIUrl":"https://doi.org/10.1029/2024GC011781","url":null,"abstract":"<p>On the continental slope of the northern Gulf of Mexico, pockmarks concentrate near the estimated updip edge of the hydrate stability zone (HSZ). We identified 5,691 pockmarks in the northern Gulf of Mexico by combining existing records with manually mapped pockmarks from bathymetric data. Nearly 70 percent of the pockmarks occur within 330–600 m water depth and the number of pockmarks drops abruptly at water depths &gt;600 m. Based on hydrate stability modeling, we argue that the updip edge of the HSZ shifted downslope since the last glacial maximum. This downslope shift caused hydrate dissociation and released charged free gas resulting in pockmark formation on the seafloor. Moreover, we observe that fluctuations in the updip edge of the HSZ since the last glacial maximum (from 330 to 605 m water depth) coincide with increased pockmark abundance. On other continental margins, pockmarks have been observed within a similar water depth range, suggesting that the loss of hydrate stability during deglaciation is a worldwide phenomenon that created intense fluid emission from the seafloor.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011781","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143846164","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":"Late Paleozoic Diachronous Subduction Initiation of the SE Paleo-Asian Ocean: Implications for Tectonic Transition From Passive to Active Continental Margin Along Northern North China Craton","authors":"Hao Zeng,&nbsp;Dongfang Song,&nbsp;Wenjiao Xiao,&nbsp;Haotian Huang","doi":"10.1029/2025GC012197","DOIUrl":"https://doi.org/10.1029/2025GC012197","url":null,"abstract":"<p>Subduction initiation is fundamental to our understanding of plate tectonics. However, the mechanisms and processes of subduction initiation, especially at passive continental margins, are poorly understood due to limited geological records. Here we identify a magmatic sequence resembling the Izu-Bonin-Mariana (IBM) forearc crust in the Mandula area of Inner Mongolia that recorded the subduction initiation of the Paleo-Asian Ocean (PAO) along the northern margin of the North China Craton (NCC). Geochemical analysis indicates that basalts and sheeted diabase dikes originated from partial melting of the upwelling asthenosphere at a forearc spreading center, succeeded by incipient arc volcanic and intrusive rocks, with increasing input of subducted slab-derived hydrous fluids. Zircon U-Pb ages reveal that the magmatic events in the Mandula area have taken place in a relatively short time interval between ∼284 Ma and ~272 Ma, similar to the duration of IBM forearc magmatism. The new results integrated with available data suggest that the southward subduction initiation of the PAO along the northern NCC was diachronous from early Carboniferous to early Permian and propagated from east to west following arc-continent collision. Therefore, our study provides a four-dimensional spatiotemporal perspective for tectonic transition from passive to active continental margin along the northern NCC.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012197","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143846163","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 Source Evolution Along the South Atlantic Transect (31°S) Records a Transition From HIMU Plume Component to Depleted MORB","authors":"P. D. Kempton,&nbsp;R. M. Coggon,&nbsp;I. Millar,&nbsp;T. M. Belgrano,&nbsp;E. Albers,&nbsp;A. Michalik,&nbsp;J. A. Milton,&nbsp;A. D. Evans,&nbsp;R. N. Taylor,&nbsp;D. A. H. Teagle","doi":"10.1029/2025GC012175","DOIUrl":"https://doi.org/10.1029/2025GC012175","url":null,"abstract":"<p>Interactions between mantle plumes and mid-ocean ridges create considerable spatial variation in composition along ridge axes. What is less well known is the temporal variation in MORB compositions along single mantle flow lines. IODP Expeditions 390/393/390C/395E recovered basaltic basement from seven sites along a flow line, the South Atlantic Transect (SAT), on the western flank of the mid-Atlantic Ridge (MAR) at ∼31°S. SAT basalts ≤49 Ma are tholeiitic with isotopic compositions similar to MORBs from the MAR between 25° and 28°S. Basement from the oldest SAT site (U1556; 61.2 Ma) is more complex, consisting of three stratigraphic sequences (SSA, SSB and SSC) ranging from MORB-like at the bottom (SSC) to Ocean Island Basalt (OIB)-like at the top (SSA); their isotopic compositions are distinct relative to both younger SAT basalts and the EM1-type Tristan–Gough plume that dominates the region, being more akin to HIMU. The presence of previously unrecognized HIMU mantle in this region is due to one or more ridge jumps that occurred west of the Walvis Ridge at ∼65 Ma. These ridge jumps relocated the spreading axis over a portion of the HIMU plume that had previously given rise to late-stage, off-axis HIMU magmatism adjacent to the Walvis Ridge. Upwelling beneath the spreading center progressively tapped a variably depleted source, reproducing it in reverse in the volcanic stratigraphy at Site U1556. Continued upwelling beneath the spreading center removed most of the HIMU plume material within ∼12 Myr, the time of Site U1558 (49.2 Ma).</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012175","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143836179","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":"Compositional and Textural Variability Among Tektites From Indochina and South China: Insights Into the Impact Origin of the Australasian Tektite Strewn Field","authors":"S. Boschi,&nbsp;S. Goderis,&nbsp;S. Liao,&nbsp;W. Li","doi":"10.1029/2024GC012133","DOIUrl":"https://doi.org/10.1029/2024GC012133","url":null,"abstract":"<p>The Australasian tektite strewn field, approximately 0.8 Ma in age, covers nearly 10% of the Earth's surface, making it the largest and most recent strewn field globally. This study provides a comprehensive analysis of the elemental composition and texture of tektites recovered from various locations within the strewn field, particularly Vietnam, Thailand, and South China. These tektites exhibit a consistent major and minor element composition similar to the Upper Continental Crust characteristic of normal tektites. Notable elemental deviations in the concentrations of CaO, FeO, MgO, Pb, and Sr are observed in the Indochina Peninsula tektites, suggesting the mixing of multiple target rock components. Indochinites from Thailand and Vietnam show lower Pb and Sr levels compared to those from China, Indonesia, and Australia, potentially reflecting proximity to the hypothetical impact site on the Bolaven Plateau, Laos. The local stratigraphy of basalts over laterite and sandstone at the proposed source crater site may explain the observed decrease in Pb and Sr concentrations, primarily due to sandstone admixture, while variable MgO, CaO, and FeO suggest a basaltic contribution. The high abundance of lechatelierite inclusions and elevated SiO₂ in Indochinites compared to South China tektites underscore the role of target rock composition in tektite formation. Schlieren flow structures further confirm rock mixing during the early impact stages. Overall, the findings elucidate the relationship between tektite formation, target rock interaction, and impact processes, supporting the Indochina Peninsula as the impact area and highlighting the need for further research on elemental fractionation and target rock heterogeneity.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012133","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143831255","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":"Petrological Evidence for Magma Mobilization Years Before the 2020/2021 Eruption of La Soufrière Volcano, St. Vincent","authors":"Michal Camejo-Harry,&nbsp;Jon Blundy,&nbsp;Euan J. F. Mutch,&nbsp;Thomas Hudson,&nbsp;John-Michael Kendall,&nbsp;Thomas Christopher,&nbsp;Rodrigo Contreras-Arratia,&nbsp;Joan L. Latchman,&nbsp;Leanka Henry","doi":"10.1029/2024GC012093","DOIUrl":"https://doi.org/10.1029/2024GC012093","url":null,"abstract":"<p>Anticipating the onset of the 2020/2021 effusive-explosive eruptive sequence at La Soufrière volcano, St. Vincent was challenging despite the established monitoring networks in operation. Here, we integrate petrological data to decipher retrospectively signs of imminent eruption from available pre-eruptive monitoring data. Using diffusion chronometry, we estimated the timescales over which magmas transported to the surface. We examined olivine crystals hosted in basaltic andesite scoria, categorizing them into four groups based on their textures (euhedral to anhedral) and core compositions (Fo_73–89). Multiply zoned olivine populations are tracked through a multi-stage journey from depth to surface corresponding to periods of magma ascent and accumulation years before eventual eruption. This correlates temporally with two phases of unrest from monitoring data: (a) a protracted <i>priming</i> phase (lasting more than a decade) manifesting in low-level seismicity, small crater transformations (rockfalls and new fumaroles) and an elevated CO₂ degassing signal; and (b) a subsequent <i>transition</i> phase, initiating just over a year before eruption with the onset of geophysical unrest in the form of discrete episodes of elevated seismicity and volcano inflation. Our findings provide new insight into the dynamics of magma mobilization at La Soufrière. We demonstrate that magmatic unrest in the roots of the sub-volcanic system precedes geophysical precursors by years, drawing connections between individually ambiguous surface signals over long timescales. Monitoring strategies optimized to detect early stages of magmatic unrest, such as identifying and locating rarer deep seismicity and routine sampling at the crater plume, could improve future responses to volcanic crises in St. Vincent.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012093","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143822149","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":"Finite Element Method for Garnet Diffusion Chronometry","authors":"Hailin Wu,&nbsp;Lingsen Zeng,&nbsp;Rongfeng Ge,&nbsp;Wenbin Zhu","doi":"10.1029/2025GC012182","DOIUrl":"https://doi.org/10.1029/2025GC012182","url":null,"abstract":"<p>Crystal geometries and boundary conditions significantly influence garnet diffusion chronometry results, yet they are frequently overlooked and pose challenges in the resolution of the diffusion equation under these complexities. To address these challenges, we introduced the Finite Element Method (FEM). We elucidated the method's rationale, from the derivation of the weak form to the formulation of the global linear system. We then evaluated the method's accuracy against the exact solution, revealing a relative error of ±3–4‰ under the specified settings, which is an order of magnitude lower than that of LA-ICP-MS, thus demonstrating the robustness of the method. Following that, our two- and three-dimensional numerical experiments showcased FEM's adaptability in modeling species diffusion across arbitrary geometries and both Dirichlet and Neumann boundary conditions. Finally, the crystal's geometric effects on the ultimate elemental concentration were examined, revealing that they hold particular significance when the diffusion length is small. We conclude that the FEM surpasses the geometric limitations of minerals while simultaneously accommodating a variety of boundary conditions, thus offering significant potential for broad applications in the field.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012182","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143822064","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":"An Assessment of Monazite Fission-Track Thermochronology as a Proxy for Low-Magnitude Cooling, Catalina-Rincon Metamorphic Core Complex, AZ, USA","authors":"Gilby Jepson,&nbsp;Barbara Carrapa,&nbsp;Sean Jones,&nbsp;Barry P. Kohn,&nbsp;Andrew J. W. Gleadow,&nbsp;Sarah W. M. George,&nbsp;Caden J. Howlett,&nbsp;Kerry Gallagher,&nbsp;Alex N. Frickenstein,&nbsp;George Gehrels,&nbsp;Antoine Triantafyllou","doi":"10.1029/2024GC011881","DOIUrl":"https://doi.org/10.1029/2024GC011881","url":null,"abstract":"<p>Conventional low-temperature thermochronology can resolve rock cooling over geological timescales (&gt;1 Myr) typically associated with ∼6–2 km of erosion, often induced by tectonic processes. Lower magnitude erosional events, however, produced by surface processes remain difficult to resolve. Here, we apply monazite fission-track (MFT) thermochronometry to the tectonically well-constrained Catalina-Rincon metamorphic core complex (MCC) to assess its ability to resolve low-temperature cooling in the upper-crust over ∼10⁶ years timescales. Established low-temperature thermochronology (apatite fission-track [AFT] and apatite and zircon [U-Th-Sm]/He) record timing of MCC and subsequent Basin and Range tectonic exhumation (26–20 Ma and 15–12 Ma, respectively). Monazite fission-track data were obtained from samples collected in two vertical elevation profiles. The eastern transect displays a Late Miocene—Pliocene age-elevation trend and implies a two-stage cooling history related to late-stage footwall uplift associated with Basin and Range normal faulting (∼7.5–5.1 Ma) and subsequent Pliocene—Pleistocene erosion (∼4.0–3.0 Ma). The northwestern transect data suggest a single period of rapid Pliocene—Pleistocene cooling (∼2.8–1.0 Ma). Thermal history modeling, however, fails to find a solution that satisfies the MFT annealing model with the AFT annealing and (U-Th-Sm)/He diffusion models. This suggests that the present MFT thermal annealing model does not account for all sources of annealing. We suggest that Pliocene—Pleistocene MFT ages may record a period of climate-enhanced erosion during a known phase of increased precipitation associated with the development of the North American Monsoon.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011881","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143821987","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":"Redox-State and Bioproductivity of the Glaciogenic Early Cryogenian Rapitan Iron Formation (Cranswick River, Canada): Constraints From Combined Cadmium—Chromium Isotopes","authors":"Robert Frei,&nbsp;Geoff Baldwin,&nbsp;Michael G. Babechuk,&nbsp;Balz S. Kamber,&nbsp;Elizabeth C. Turner","doi":"10.1029/2024GC012038","DOIUrl":"https://doi.org/10.1029/2024GC012038","url":null,"abstract":"<p>The Rapitan Group (Northwest Territories, Canada) includes banded iron formation (BIF), an unusual sediment type that is associated with late Neoproterozoic glaciations, in this case, the early Cryogenian Sturtian glaciation. New non-traditional stable isotope data from jasper and hematite iron formation (IF) from the Cranswick River area contribute new insights regarding water chemistry changes in the respective depositional basin during glacier advance and retreat. Cr isotope signatures are characterized by strongly positively fractionated δ⁵³Cr values (+0.68–1.47‰), attesting to strongly oxidized surface waters during the entire depositional episode. Relatively weakly fractionated δ¹¹⁴Cd isotope signatures (−0.02 to +0.28‰), and the absence of organic matter in the samples, indicate a low bioproductivity during BIF deposition. Detailed fluctuations over an intermittent glacier advance and retreat cycle recorded in the studied section, however, reveal an ephemeral increase in primary production (excursion to slightly elevated δ¹¹⁴Cd values) just after deposition of a diamictite layer, which agrees with corresponding elevated δ⁵³Cr values. This evidence attests to the sensitivity of the Cd-Cr double isotope tracer applied to BIFs to reconstruct changes in the surface waters of depositional basins and track climate changes that accompanied the glacial episodes. When compared to data from the younger (Marinoan/Ediacaran) Urucum BIF in Brazil, the Rapitan section differs by lack of negative Ce anomalies in its rare earth element patterns, implying that water column oxidation was not as strong during the early Cryogenian as compared to the Marinoan/Ediacaran glacial episodes.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012038","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143818559","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}