Geochemistry Geophysics Geosystems最新文献

{"title":"Early–Late Carboniferous Tectonic Evolution of the Northern North China Craton (NE China): Constraints From Zircon Ages, Geochemistry, and Crustal Thickness Modeling","authors":"Yunfei Chang,&nbsp;Qingxiang Du,&nbsp;Huachun Gan,&nbsp;Xiaoli Shen,&nbsp;Zuozhen Han,&nbsp;Xiaoxue Hou,&nbsp;Huicong Zhang","doi":"10.1029/2026GC012960","DOIUrl":"https://doi.org/10.1029/2026GC012960","url":null,"abstract":"<p>The tectonic evolution of the northern margin of the North China Craton (NCC) remains controversial. In this study, we obtained zircon U–Pb ages, geochemical data, and Sr–Nd isotopic data for volcanic rocks, and detrital zircon ages for sedimentary rocks from the Yufutun, Tongqigou, and Benxi formations in central-southern Jilin Province, NE China. Dating of basalts and andesites from the Yufutun Formation yields Late Carboniferous ages (302–307 Ma). The basalts exhibit relatively flat rare earth element patterns, with high ratios of Nb/Ta (17.65–20.55), Sm/Nd (0.30–0.36), and initial ⁸⁷Sr/⁸⁶Sr (0.7064–0.7068), indicating derivation from a primitive mantle source with geochemical characteristics similar to those of back-arc basin basalts. The andesites show high Th (3.44–4.97 ppm) and Ce (33.96–44.79 ppm) values and low initial ⁸⁷Sr/⁸⁶Sr ratios (0.7039–0.7042), suggesting a mixed source of crustal and lithospheric mantle components and geochemical affinities similar to arcs. The youngest detrital zircon ages obtained from sedimentary rocks of the Yufutun, Tongqigou, and Benxi formations are 342 ± 3 Ma, 311 ± 7 Ma, and 317 ± 5 Ma, respectively. Geochemical data from sediments of the Yufutun and Benxi formations indicate a passive margin, while siliceous rocks of the Tongqigou Formation indicate an active margin. Whole-rock trace elements and detrital zircon Eu/Eu* ratios were used to estimate crustal thickness, suggesting that subduction of the Paleo-Asian Ocean initiated around 330 Ma and that collision between the NCC and the marginal arcs began at 270 Ma, with scissor-like closure occurring from west to east along the northern margin of the NCC.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 8","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC012960","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148753108","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":"Exhumed eo-Alpine High-Pressure Rocks Fed Campanian Turbidites in Eastern Sardinia","authors":"Francesco Massari,&nbsp;Maria Giuditta Fellin,&nbsp;Cristina Stefani,&nbsp;Eva Enkelmann,&nbsp;Iginio Dieni,&nbsp;Stefano Sanchetti","doi":"10.1029/2025GC012662","DOIUrl":"https://doi.org/10.1029/2025GC012662","url":null,"abstract":"<p>This study investigates the detrital record of the early orogenic evolution of the Sardinia-Calabria system, preserved in Upper Cretaceous arenites exposed in eastern Sardinia. Sardinia and Corsica form a continental block that includes a segment of the Alpine orogen and of its former foreland basin. We investigate Upper Cretaceous arkosic turbidites from the Lanaittu Valley in eastern Sardinia. Biostratigraphy constrains the depositional age of the arenites to the middle-late Campanian. Petrographic analyses confirmed the presence of rare glaucophane-crossite combined with up to 13% kyanite and trace amounts of lawsonite. Using U-Pb and (U-Th)/He methods, double-dated detrital zircons reveal a significant population (22%) that records mid-to-Late Cretaceous exhumation-related cooling. Older zircon U-Pb date populations, with a dominant Middle Permian peak and Proterozoic components, indicate a cratonic provenance consistent with the Sardinia/Calabria basement. A multi-source area within an active orogenic belt is envisaged, supplying detritus to a basin located on the thinned Sardinian crust. These data indicate an episode of eo-Alpine high-pressure metamorphism and exhumation, likely related to the subduction of the Western Ligurian Ocean beneath a portion of the Alkapeca microplate, which is identified with the northern Calabria-Peloritani subterrane. This metamorphic event is comparable to eo-Alpine events recorded elsewhere in the Mediterranean region, such as in the Sesia zone of the Western Alps. Exhumation is inferred to have occurred during ongoing convergence, marking an early stage of Alpine subduction.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 8","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012662","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148752489","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":"Event Deposits Recorded Over the Past 800 kyr in IODP Hole U1433A (South China Sea): Implications of a Revised Methodology for Chronology and Paleoclimate Reconstruction","authors":"Xunpeng Li,&nbsp;Shuang Sun,&nbsp;Yuwei Zhang,&nbsp;Ziqiang Mao,&nbsp;Lina Jin,&nbsp;Yulong Zhao,&nbsp;G. Ian Alsop,&nbsp;Zhifei Liu,&nbsp;Yin Lu","doi":"10.1029/2026GC012907","DOIUrl":"https://doi.org/10.1029/2026GC012907","url":null,"abstract":"<p>Instantaneous event deposits such as turbidites, debrites, and slumps are common and frequently occur in marginal seas. These instantaneous deposits represent seconds to days in duration, and can therefore significantly impact age-depth models and interpretation of paleoclimate history based on thick sedimentary sequences recovered in deep drill cores. However, these event deposits have rarely been considered when investigating International Ocean Discovery Program (IODP)/ODP deep cores from marginal seas. To resolve the problem, we take the South China Sea, one of the largest active marginal seas worldwide, as a typical research example. We identified 129 centimeter-to-meter-scale event layers from Hole U1433A (189–0 m, 800–0 kyr) in the southwest part of the deep South China Sea. These instantaneous event deposits account for ∼16% of the total sediment thickness in Hole U1433A, and significantly affect the reconstruction of the age-depth model and paleoclimate history. We refine the preliminary age-depth model, that is based on paleomagnetic and microfossil ages recovered from the hole, by removing instantaneous event deposits. We further test the effectiveness of our applied sedimentological approach by comparing paleoclimate profiles that include or omit those event layers. This test indicates that the event-free approach is effective and essential for a better reconstruction of the age-depth model and paleoclimate history based on the IODP deep core. Our revised sedimentological methodology may also prove suitable for other marginal seas with frequent instantaneous event deposits elsewhere in the world.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 8","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC012907","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148752633","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":"Oxygen Fugacity Buffers and an Interactive Calculator","authors":"Michael Anenburg","doi":"10.1029/2026GC013032","DOIUrl":"https://doi.org/10.1029/2026GC013032","url":null,"abstract":"<p>Oxygen fugacity buffers are equilibrium phase assemblages that constrain the chemical potential of oxygen. They may be coexisting minerals or fluids, or their metastable extrapolations. Oxygen fugacity values vary as a function of pressure and temperature, such that raw numbers often have little interpretive value. Instead, oxygen fugacity is generally reported relative to oxygen fugacity buffers that provide convenient and tangible reference curves. The exact calculation of these curves is typically highly complex, involving the solution of thermodynamic relationships using advanced algebra, calculus, and numerical methods. As a result, buffers are often calculated using simple parameterizations which are easily implemented. This simplification of oxygen fugacity buffer curves comes at the cost of accuracy and precision in pressure and temperature space. Occasionally, several parameterizations for a single buffer exist, causing discrepancies in published results. Here, we introduce an online calculator built using the shiny package for the R programming language. The calculator solves the often complex thermodynamics and provides a simple interface for users to manipulate input parameters. All calculations are fully documented and justified. This paper describes some of the common calculation methods for oxygen fugacity buffers, including 1 bar parameterizations, correct usage of tabulated standard pressure data, high-pressure equations of state and phase transitions, gas mixing at low and high pressures, and more. A description of the many challenges and problems in the current literature is provided, and recommendations for future calibrations are suggested.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 8","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013032","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148647867","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":"Carbonate-Associated Sulfate Does Not Record Superheavy δ34S in Deep Scandinavian Bedrock Fractures: Implications for Pyrite Formation in the Deep Biosphere","authors":"V. Fichtner,&nbsp;F. Genske,&nbsp;E. Kooijman,&nbsp;H. Drake","doi":"10.1029/2025GC012798","DOIUrl":"https://doi.org/10.1029/2025GC012798","url":null,"abstract":"<p>In deep bedrock fractures of the Fennoscandian shield, pyrite with “superheavy” δ³⁴S values of up to 147‰ exists together with calcite. The extreme variability and ³⁴S-enrichment in pyrite indicate that microbial sulfate reduction (MSR) evolved to almost complete sulfate exhaustion in closed-system microenvironments. The bulk δ³⁴S_pyrite of up to 81‰ implies a sulfate source with unusually high δ³⁴S, although such a source has not yet been identified. Here, we aim to decipher this source by analyzing carbonate-associated sulfate (CAS) of calcite related to superheavy pyrite. Our δ³⁴S_CAS values reveal low to moderate ³⁴S enrichment, with δ³⁴S_CAS between 2.3 and 28.2‰, which is far below the bulk δ³⁴S_pyrite of up to 81‰ indicating a decoupled sulfate pool for CAS and pyrite origin. The extreme δ³⁴S fractionation recorded by pyrite implies very slow MSR rates, which typically promote calcite dissolution rather than precipitation. Calcite precipitation was thus inhibited during superheavy pyrite formation. Instead, the calcite shows signs for anaerobic oxidation of methane coupled to sulfate reduction (AOM-SR), reflected by ¹³C-depletion and moderate ³⁴S-enrichment. The AOM-SR process reduces sulfate concentration, in turn providing conditions suitable for the formation of superheavy pyrite. We propose that a limited supply of substrates (sulfate and organic matter) and Fe²⁺, their episodic input into the deep fracture system together with low diffusion rates of fracture fluids enabled a balance and completion of microbial methanogenesis, AOM-SR, and MSR. Extreme isotope signatures may thus represent diagnostic features of episodic, energy-limited deep biosphere ecosystems, with implications for understanding subsurface microbial ecology and biogeochemical cycling.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 8","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012798","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148617074","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":"Highly Enriched and Heterogeneous Mantle Signals Recorded in Mantle Pyroxenite Veins","authors":"Zhen-Yu Zhang,&nbsp;Chuan-Zhou Liu,&nbsp;Yan Liang,&nbsp;Tong Liu,&nbsp;Chang Zhang,&nbsp;Bo-Da Liu,&nbsp;Wen-Bin Ji,&nbsp;Wei-Qi Zhang,&nbsp;Ke Huang","doi":"10.1029/2026GC013072","DOIUrl":"https://doi.org/10.1029/2026GC013072","url":null,"abstract":"<p>The Earth's mantle is inherently heterogeneous, reflecting ongoing mantle depletion and crustal recycling driven by plate tectonics. Radiogenic isotopes in oceanic basalts are commonly used to characterize mantle reservoirs, but the full chemical diversity of mantle-derived melts may be obscured by magma mixing during melt transport and storage. Pyroxenite veins formed by melt segregation or melt–peridotite interaction in the lithospheric mantle provide an alternative archive that may better preserve the compositional diversity of mantle-derived melts. We present Nd–Hf isotopic data for bulk rock, clinopyroxene, and orthopyroxene from pyroxenite veins in three mantle massifs exposed along the Yarlung-Tsangpo Suture Zone in southern Tibet. Clinopyroxene and orthopyroxene from the same samples display distinct initial isotopic compositions, indicating crystallization from compositionally different melt pulses. Orthopyroxene commonly records more enriched and less radiogenic signatures than clinopyroxene, highlighting its potential to preserve isotopic information on enriched melt components. Additionally, the pyroxenite veins define a wide range of initial Nd–Hf isotopic compositions (initial <i>ε</i>_Nd = −10.3 to +8.6 and initial <i>ε</i>_Hf = −8.4 to 18.3), extending beyond the variability reported for basaltic lavas and cumulates from the same ophiolitic system. These variations are consistent with mixing between melts derived from depleted mantle and melts originating from enriched mantle domains. Our results suggest that mantle pyroxenite veins can preferentially preserve the isotopic heterogeneity of the enriched mantle source. Overall, this study highlights the value of mineral-scale isotopic analyses in pyroxenites for documenting mantle heterogeneity and provides new constraints on melt migration and aggregation processes in the upper mantle.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 8","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013072","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148617075","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 Continental Basalt Sources and Mantle Processes Using Fe Stable Isotopes","authors":"Yi-Shan Cheng,&nbsp;Jian-Qiang Liu,&nbsp;Li-Hui Chen,&nbsp;Xun Yu,&nbsp;Gang Zeng,&nbsp;Xiao-Jun Wang,&nbsp;Zhao-Yang He,&nbsp;Jian Zhao,&nbsp;Frances M. Deegan,&nbsp;Valentin R. Troll,&nbsp;Hong-Fu Zhang","doi":"10.1029/2025GC012828","DOIUrl":"https://doi.org/10.1029/2025GC012828","url":null,"abstract":"<p>Iron (Fe) isotopes have emerged as powerful tracers of mantle source heterogeneity and melting processes, yet the mechanisms producing heavy Fe isotope signatures (high δ⁵⁷Fe values) in intraplate basalts remain debated. Competing interpretations include partial melting of recycled pyroxenite domains versus carbonate-induced oxidation of a mantle source. Here we present new high precision Fe isotope data together with whole rock elemental and Sr-Nd-Pb-Hf isotopic compositions of Cenozoic Chifeng basalts from eastern China to test the above hypotheses. Fractionation corrected bulk-rock δ⁵⁷Fe values of Chifeng basalts vary from +0.08‰ to +0.30‰, which cannot be readily explained by either magmatic processes or mantle oxidation. Systematic covariations of δ⁵⁷Fe with SiO₂, trace element ratios (Nb/Zr, Ce/Pb, and Gd/Yb), and radiogenic isotopes (¹⁴³Nd/¹⁴⁴Nd and ²⁰⁶Pb/²⁰⁴Pb) demonstrate that Fe isotope variations are closely linked to source heterogeneities. Quantitative modeling reveals a positive correlation between pyroxenite-melt fraction and δ⁵⁷Fe value, indicating that variations in pyroxenitic input likely control the Fe isotopic compositions of Chifeng basalts. In fact, the Indian-type Pb isotope signatures together with the heavy δ⁵⁷Fe values of Chifeng basalts are best accounted for by recycled Pacific oceanic crust that was hybridized with subducted sediments and subsequently incorporated into the asthenosphere beneath eastern China. The integrated Fe–Nd–Pb isotope data further support melt–melt mixing between pyroxenite-derived and peridotite-derived melts within the lithospheric mantle. Therefore, the Fe isotope signatures of Chifeng basalts record source lithological heterogeneity linked to recycled pyroxenites and demonstrate the utility of Fe isotopes in resolving mantle processes.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 8","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012828","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148617076","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":"Petrogenesis and Tectonic Evolution of Cenozoic Magmatism in the Southernmost Northern Andes: Insights From Zircon Petrochronology","authors":"J. Iglesias,&nbsp;C. Witt,&nbsp;L. C. Sandoval Espinel,&nbsp;M. Zattin,&nbsp;M. Poujol,&nbsp;O. Bruguier,&nbsp;O. Poma,&nbsp;M. J. Hernández,&nbsp;O. Averbuch,&nbsp;M. Seyler,&nbsp;D. Bosch,&nbsp;F. Chanier,&nbsp;S. Ventalon,&nbsp;C. Liorzou,&nbsp;V. Bosse","doi":"10.1029/2025GC012829","DOIUrl":"https://doi.org/10.1029/2025GC012829","url":null,"abstract":"<p>This study integrates new zircon U–Pb ages, zircon εHf_(t)–δ¹⁸O isotopic data, and whole-rock geochemistry to refine the temporal and spatial framework of magmatism in the southern Northern Andes (SNA) from ∼65 to 6 Ma. The San Lucas, Catamayo, Portachuela, and Gonzanamá batholiths and magmatic suites, along with Late Miocene plutons, display emplacement patterns strongly controlled by pre-existing crustal architecture. Early San Lucas magmatism (65–63 Ma) most-likely intruded into thick continental crust (∼60 km) and exhibited enriched isotopic signatures (εHf_(t): −5 to +5 and δ¹⁸O: 6‰–12‰), while later pulses (54–49 Ma) intruded through thinner crust (∼30 km) and exhibited less enriched compositions (εHf_(t): +4.3 to +6.5 and δ¹⁸O: 5‰–6.5‰). West of the Las Aradas Fault, the Catamayo (36–32 Ma) and Gonzanamá (21–17 Ma) magmatic suites display juvenile signatures (εHf_(t): +7 to +14 and δ¹⁸O: 3.7‰–6‰), reflecting their emplacement into a thin oceanic-type basement. East of the fault, the early pulse of the Catamayo suite (39 Ma) intruded thicker crust (∼60 km) and recorded more evolved signatures (εHf_(t): +4.7 to +7). Magmatism in the Portachuela (∼32–16 Ma) derives from enriched mantle sources, possibly influenced by limited sediment subduction (εHf_(t): −1.3 to +6.7 and δ¹⁸O: 3.5‰–6.7‰). Some Late Miocene plutons (13–6 Ma) exhibit adakitic signatures as well as high-pressure fractionation and isotopic enrichment (εHf_(t): +0.7 to +7 and δ¹⁸O: ∼4‰ to 6.7‰) that are consistent with crustal thickening. Collectively, these results demonstrate that SNA magmatism reflects two contrasting reservoirs across the Las Aradas Fault, underscoring strong spatial controls and challenging models of large-scale arc migration by highlighting the roles of mantle input, basement heterogeneity, and variable crustal thickness.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 8","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012829","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148617246","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":"Crustal Thickness Inversion From Magmatic Geochemistry Reveals Spatiotemporal Evolution and Two-Stage Uplift of the Iranian Plateau","authors":"Jun Hu,&nbsp;Yongwei Zhao,&nbsp;Zhengquan Chen,&nbsp;Ni Li,&nbsp;Huan Kang","doi":"10.1029/2026GC013007","DOIUrl":"https://doi.org/10.1029/2026GC013007","url":null,"abstract":"<p>The Cenozoic topographic growth of the Iranian Plateau, situated at the Arabia-Eurasia collision front, provides insights into continental collision dynamics. However, the relative contributions of tectonic shortening versus deep mantle processes to crustal thickening remain debated because systematic quantitative constraints on paleo-crustal thickness evolution are limited. Here, from a compiled data set of 2,525 Eocene to Quaternary volcanic rocks across the Alborz Magmatic Belt and Urumieh-Dokhtar Magmatic Arc, we utilized 1,198 rigorously filtered samples to reconstruct crustal thickness since ∼56 Ma. Using Sr/Y and (La/Yb)_N ratios as pressure-sensitive proxies, we propose a two-stage model of crustal thickening and surface uplift. Results indicate a relatively thin Eocene crust (∼37 km), corresponding to near-sea-level paleotopography. During the Oligocene–Miocene, continental collision drove diachronous, northwest-to-southeast crustal thickening. This established a unified thick crust (∼54 km) and regional isostatic uplift of 1.5–3.2 km, representing the first stage of primary tectonic shortening. Since the Pliocene (&lt;5 Ma), localized secondary uplift has occurred in northwestern Iran and central Alborz, resulting in paleoelevation approaching ∼4 km. This secondary uplift was driven by deep geodynamic processes (slab break-off and lithospheric delamination) superimposed on the Arabia-Eurasia convergence. This two-stage model is consistent with two discrete episodes of accelerated exhumation recorded by thermochronological data during the Oligocene and at 6–3 Ma. Our quantitative evidence supports the plateau's role as a topographic barrier enhancing the Miocene South Asian Summer Monsoon. This study highlights the Iranian Plateau's significance for linking deep geodynamics, crustal thickening, and surface-environmental change.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 8","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013007","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148617245","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":"Marine Sediment Record of Eruption-Fed Vertical Density Currents, Kermadec Arc (Rangitāhua)","authors":"Janne M. Scheffler,&nbsp;Martin Jutzeler,&nbsp;Steffen Kutterolf,&nbsp;Rebecca J. Carey,&nbsp;Josephin Wolf,&nbsp;Jacek Raddatz,&nbsp;Kuo-Lung Wang,&nbsp;Hao-Yang Lee","doi":"10.1029/2025GC012859","DOIUrl":"https://doi.org/10.1029/2025GC012859","url":null,"abstract":"<p>Products of explosive volcanism can be transported into the oceans, where they form marine tephra layers. The processes responsible for their deposition are often complex, involving multiple transport mechanisms. During the RV <i>Investigator</i> voyage IN2022-V02 (2022), a 35-cm-thick marine tephra unit was piston-cored at 2,460 m water depth in the Havre Trough, north of New Zealand. The unit grades from planar laminated medium sand at the base to cross-laminated fine sand and massive sandy silt at the top. It is composed predominantly of elongated (tube-shaped), vesicular, curviplanar rhyolitic glass shards, with rare lithic clasts and pyroxene and feldspar fragments enriched at the base. Planktic foraminifera occur as intact bioclasts, increasing upward from 1 to 20 vol.%. The homogeneous major and trace element composition of glass shards throughout the sequence indicates a juvenile origin from a single volcanic event. Geochemical fingerprinting identified the Macauley Volcano, located ∼100 km from the core site, as the most likely source. The stratigraphy and vertical arrangement of the bedforms are consistent with a model of sedimentation by subaerial eruption plume fallout and/or pyroclastic density currents traveling over the ocean, followed by vertical density currents through the water column that eventually transformed into seafloor-hugging turbidity currents upon impact on the seafloor. Our results demonstrate that the sedimentary history of primary marine tephra associated with large magnitude eruptions may be complex and include vertical density currents. This sedimentation regime may significantly contribute to the lateral variation in the thickness of marine marker tephra layers.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 7","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012859","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148616387","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}