Braid deltas, environments that form where braided rivers meet base level, are more abundant on Holocene Earth than previously appreciated. A worldwide survey identified 786 braid deltas with feeder systems >500 m wide. Braid deltas occur at all latitudes north of the Antarctic Circle and are most abundant by land area in the 45°S−60°S and 60°N−90°N latitude bands. Marine-associated braid deltas compose 71% of the dataset, with the remainder in marginal lacustrine settings. Half of the observed braid deltas do not form radial terminal delta-plain geometry. Hierarchical clustering analysis separates braid deltas into nine clusters that define a classification scheme. Drivers of differentiation include basin type, embayment, sediment supply, and flow intermittence. The classified dataset provides analogues to ancient, nonvegetated deltaic environments and the essential framework for development of braid-delta facies models.
{"title":"Global distribution, hierarchical clustering classification, and significance of Holocene braid deltas","authors":"Jason G. Muhlbauer, Christopher M. Fedo","doi":"10.1130/g53851.1","DOIUrl":"https://doi.org/10.1130/g53851.1","url":null,"abstract":"Braid deltas, environments that form where braided rivers meet base level, are more abundant on Holocene Earth than previously appreciated. A worldwide survey identified 786 braid deltas with feeder systems >500 m wide. Braid deltas occur at all latitudes north of the Antarctic Circle and are most abundant by land area in the 45°S−60°S and 60°N−90°N latitude bands. Marine-associated braid deltas compose 71% of the dataset, with the remainder in marginal lacustrine settings. Half of the observed braid deltas do not form radial terminal delta-plain geometry. Hierarchical clustering analysis separates braid deltas into nine clusters that define a classification scheme. Drivers of differentiation include basin type, embayment, sediment supply, and flow intermittence. The classified dataset provides analogues to ancient, nonvegetated deltaic environments and the essential framework for development of braid-delta facies models.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"2 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145651156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Changyeol Lee, Nestor G. Cerpa, Jaehoon Lee, Minyoung Huh
Scattered non-age-progressive intraplate volcanism (SIV) is globally widespread, yet its underlying mechanism remains poorly understood. A hypothesis posits that the magma feeding this volcanism originates from hydrous melting of upwelling mantle from the mantle transition zone (MTZ), driven by subduction-induced return flow. Here, we test this hypothesis using a two-dimensional numerical model of passive MTZ upwelling that incorporates magma formation and transport based on two-phase flow theory. Our results show that dehydration of the upwelling MTZ mantle at the 410 km discontinuity initially forms a large, horizontally elongated magmatic solitary wave. Driven by buoyancy, this wave ascends and subsequently disintegrates into multiple, smaller (∼10−20 km in diameter) magmatic solitary waves. These discrete waves ascend randomly through the asthenosphere in a process akin to “mantle rain,” reaching the lithosphere base in ∼10 m.y. Our model provides a viable explanation for SIV.
{"title":"Intraplate volcanism induced by magmatic solitary waves ascending from the mantle transition zone","authors":"Changyeol Lee, Nestor G. Cerpa, Jaehoon Lee, Minyoung Huh","doi":"10.1130/g53800.1","DOIUrl":"https://doi.org/10.1130/g53800.1","url":null,"abstract":"Scattered non-age-progressive intraplate volcanism (SIV) is globally widespread, yet its underlying mechanism remains poorly understood. A hypothesis posits that the magma feeding this volcanism originates from hydrous melting of upwelling mantle from the mantle transition zone (MTZ), driven by subduction-induced return flow. Here, we test this hypothesis using a two-dimensional numerical model of passive MTZ upwelling that incorporates magma formation and transport based on two-phase flow theory. Our results show that dehydration of the upwelling MTZ mantle at the 410 km discontinuity initially forms a large, horizontally elongated magmatic solitary wave. Driven by buoyancy, this wave ascends and subsequently disintegrates into multiple, smaller (∼10−20 km in diameter) magmatic solitary waves. These discrete waves ascend randomly through the asthenosphere in a process akin to “mantle rain,” reaching the lithosphere base in ∼10 m.y. Our model provides a viable explanation for SIV.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"32 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145651158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Adrian E. Castro, Daniel R. Viete, Stephanie Walker, Steven J. Jaret, Isabella Brunet, Katherine Morin, Dana C. Brenner, Supratik Roy, Ethan F. Baxter, Oliver M. Wolfe, Jay Thomas
The Manhattan Prong (a belt of ancient rock in southern New York, USA) underlies one of the largest population bases in North America yet its tectonometamorphic history remains poorly understood. We performed monazite U-Pb and garnet Sm-Nd petrochronology in association with garnet diffusion chronometry on a sample of the Manhattan Schist from Central Park, New York City. Monazite included in both garnet and matrix yielded a 206Pb/238U date of ca. 438 Ma, though one matrix grain yielded a distinctly younger date of ca. 391 Ma; all monazite analyzed showed identical rare earth element compositions. Garnet yielded a robust isochron date of ca. 386 Ma, interpreted to constrain the timing of garnet growth at near-peak metamorphic conditions. Retention of manganese zoning in 1-mm-scale garnet requires that near-peak metamorphic conditions at ca. 386 Ma persisted for <5 m.y. The Manhattan Schist records a polymetamorphic history involving Taconic greenschist-facies metamorphism at ca. 438 Ma, recorded by relict monazite, then short-lived Acadian kyanite-grade metamorphism at ca. 386 Ma, recorded by garnet and the major rock-forming assemblage. These results are consistent with tectonic models that involve localized, episodic heating of the middle crust, rather than gradual and more pervasive processes of heating and cooling. Our study is an example of the nuanced tectonometamorphic understanding that can be gained by combining accessory and major phase petrochronology.
{"title":"Decoupled monazite and garnet petrochronology reveals short-duration, high-temperature Acadian metamorphism in the Manhattan Schist, New York City, USA","authors":"Adrian E. Castro, Daniel R. Viete, Stephanie Walker, Steven J. Jaret, Isabella Brunet, Katherine Morin, Dana C. Brenner, Supratik Roy, Ethan F. Baxter, Oliver M. Wolfe, Jay Thomas","doi":"10.1130/g53777.1","DOIUrl":"https://doi.org/10.1130/g53777.1","url":null,"abstract":"The Manhattan Prong (a belt of ancient rock in southern New York, USA) underlies one of the largest population bases in North America yet its tectonometamorphic history remains poorly understood. We performed monazite U-Pb and garnet Sm-Nd petrochronology in association with garnet diffusion chronometry on a sample of the Manhattan Schist from Central Park, New York City. Monazite included in both garnet and matrix yielded a 206Pb/238U date of ca. 438 Ma, though one matrix grain yielded a distinctly younger date of ca. 391 Ma; all monazite analyzed showed identical rare earth element compositions. Garnet yielded a robust isochron date of ca. 386 Ma, interpreted to constrain the timing of garnet growth at near-peak metamorphic conditions. Retention of manganese zoning in 1-mm-scale garnet requires that near-peak metamorphic conditions at ca. 386 Ma persisted for &lt;5 m.y. The Manhattan Schist records a polymetamorphic history involving Taconic greenschist-facies metamorphism at ca. 438 Ma, recorded by relict monazite, then short-lived Acadian kyanite-grade metamorphism at ca. 386 Ma, recorded by garnet and the major rock-forming assemblage. These results are consistent with tectonic models that involve localized, episodic heating of the middle crust, rather than gradual and more pervasive processes of heating and cooling. Our study is an example of the nuanced tectonometamorphic understanding that can be gained by combining accessory and major phase petrochronology.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"19 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145599612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Charlie Bristow, Nicholas Lancaster, Khalid Al-Ramadan, Christina Neudorf, Amanda Keen-Zebert
Luminescence dating of interdune sabkha sediments and cross strata deposited on the lee face of a 160-m-high mega-crescentic dune in the eastern Rub’ al-Khali sand sea provides information on dune dynamics and preservation potential. Optically stimulated luminescence ages show that the rates of dune accumulation varied during the latest Pleistocene and Holocene. Sedimentary structures indicate that megadune migration was the result of strong northwesterly “Shamal” winds. During the same interval of the late Pleistocene and early Holocene, linear dunes in the northeastern United Arab Emirates were also accumulating rapidly, indicating that the period 16−9 ka was characterized by regionally widespread dune formation and/or reworking. The dune has subsequently migrated to the SSE almost 900 m since the early Holocene, at an average rate of 77 m/k.y., indicating persistence of the Shamal wind system for at least 20 k.y. Rates of megadune migration and wet sabkha accumulation reveal that, despite their very large size, less than 1% of the megadune would be preserved in a sedimentary record.
{"title":"Not much to show for it: Late Pleistocene dynamics of migrating megadunes in the Rub’ al-Khali, Saudi Arabia, indicate minimal preservation of their deposits","authors":"Charlie Bristow, Nicholas Lancaster, Khalid Al-Ramadan, Christina Neudorf, Amanda Keen-Zebert","doi":"10.1130/g53651.1","DOIUrl":"https://doi.org/10.1130/g53651.1","url":null,"abstract":"Luminescence dating of interdune sabkha sediments and cross strata deposited on the lee face of a 160-m-high mega-crescentic dune in the eastern Rub’ al-Khali sand sea provides information on dune dynamics and preservation potential. Optically stimulated luminescence ages show that the rates of dune accumulation varied during the latest Pleistocene and Holocene. Sedimentary structures indicate that megadune migration was the result of strong northwesterly “Shamal” winds. During the same interval of the late Pleistocene and early Holocene, linear dunes in the northeastern United Arab Emirates were also accumulating rapidly, indicating that the period 16−9 ka was characterized by regionally widespread dune formation and/or reworking. The dune has subsequently migrated to the SSE almost 900 m since the early Holocene, at an average rate of 77 m/k.y., indicating persistence of the Shamal wind system for at least 20 k.y. Rates of megadune migration and wet sabkha accumulation reveal that, despite their very large size, less than 1% of the megadune would be preserved in a sedimentary record.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"18 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145560584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Naixiao Xu, Hao Cheng, Geoffrey D. Bromiley, Henry J.B. Dick, Lingmin Zhang
The extent of chlorine isotope heterogeneity within Earth’s mantle remains a subject of active debate. To contribute to this discussion, we present the first in situ chlorine isotope measurements of apatite from Integrated Ocean Drilling Program Hole U1473A (Southwest Indian Ridge) gabbros. The apatites record a pristine mantle δ37Cl value of −0.51‰ ± 0.04‰, consistent with global mid-ocean ridge basalt averages. Systematic negative covariations between δ37Cl and Cl content across lithological boundaries cannot be explained by fractional crystallization alone. Compared to altered gabbros from Ocean Drilling Program Hole 735B (Atlantis Bank), apatites from U1473A show lower δ37Cl values. The preservation of euhedral textures and constant OH concentrations in these apatites, combined with amphibole geochemistry, rules out lower-temperature seawater alteration. Instead, these trends reflect high-temperature processes, including melt−rock interaction, brine assimilation, or mantle heterogeneity. Our findings demonstrate that δ37Cl variability in mantle-derived apatites records both crustal recycling and intrinsic mantle heterogeneity, confirming their utility as reliable tracers of deep Earth volatile cycling.
{"title":"Mantle chlorine isotope signature and melt−rock interaction revealed by apatite at the Southwest Indian Ridge","authors":"Naixiao Xu, Hao Cheng, Geoffrey D. Bromiley, Henry J.B. Dick, Lingmin Zhang","doi":"10.1130/g53563.1","DOIUrl":"https://doi.org/10.1130/g53563.1","url":null,"abstract":"The extent of chlorine isotope heterogeneity within Earth’s mantle remains a subject of active debate. To contribute to this discussion, we present the first in situ chlorine isotope measurements of apatite from Integrated Ocean Drilling Program Hole U1473A (Southwest Indian Ridge) gabbros. The apatites record a pristine mantle δ37Cl value of −0.51‰ ± 0.04‰, consistent with global mid-ocean ridge basalt averages. Systematic negative covariations between δ37Cl and Cl content across lithological boundaries cannot be explained by fractional crystallization alone. Compared to altered gabbros from Ocean Drilling Program Hole 735B (Atlantis Bank), apatites from U1473A show lower δ37Cl values. The preservation of euhedral textures and constant OH concentrations in these apatites, combined with amphibole geochemistry, rules out lower-temperature seawater alteration. Instead, these trends reflect high-temperature processes, including melt−rock interaction, brine assimilation, or mantle heterogeneity. Our findings demonstrate that δ37Cl variability in mantle-derived apatites records both crustal recycling and intrinsic mantle heterogeneity, confirming their utility as reliable tracers of deep Earth volatile cycling.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"28 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145554262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Quentin Bollaert, Mathieu Chassé, Nicolas Menguy, Corentin Le Guillou, Artur Bastos Neto, David Troadec, Laurence Galoisy, Georges Calas
The origin of the mobility of low-solubility elements such as niobium during supergene weathering remains elusive, despite growing evidence, especially in strongly weathered regolith. In the critical zone, the low mobility of these high field strength elements (HFSEs) is assigned to the resistance of their mineral hosts. This property led to their use as geochemical invariants to quantify mass transfer during alteration. Pyrochlore is a quintessential weathering-resistant mineral accommodating most HFSEs. Here, we investigate the surface alteration layers of pyrochlore using a nanoscale approach within a well-characterized regolith subject to intense weathering over millions of years. In the profile, porous pyrochlore rims exhibit distinct chemistry with higher Th contents. Sharp chemical and textural nanometer-scale interfaces between Pb-rich and Th-rich pyrochlore provide compelling evidence for interface-coupled dissolution-reprecipitation. This demonstrates the alterability of the Nb octahedral framework in pyrochlore and the relative stability of its Th-rich counterpart during tropical weathering. Nanoscale analyses of Ce-rich pyrochlores in two additional lateritic horizons confirm the generality of this mechanism across the deposit. The presence of Nb in secondary nano-cerianite found in manganiferous veins establishes its transport during weathering. These nanomineralogical studies of secondary assemblages provide the first direct evidence of Nb mobility during weathering at the deposit scale, underscoring the need to reappraise HFSE geochemical cycles at Earth’s surface, especially in light of growing mining volumes. This paves the way for further investigations into the alteration of weathering-resistant minerals at the nanoscale, providing new models of mobilization and sequestration through previously undocumented processes.
{"title":"Pyrochlore nanomineralogy questions the immobility of niobium during tropical weathering","authors":"Quentin Bollaert, Mathieu Chassé, Nicolas Menguy, Corentin Le Guillou, Artur Bastos Neto, David Troadec, Laurence Galoisy, Georges Calas","doi":"10.1130/g53465.1","DOIUrl":"https://doi.org/10.1130/g53465.1","url":null,"abstract":"The origin of the mobility of low-solubility elements such as niobium during supergene weathering remains elusive, despite growing evidence, especially in strongly weathered regolith. In the critical zone, the low mobility of these high field strength elements (HFSEs) is assigned to the resistance of their mineral hosts. This property led to their use as geochemical invariants to quantify mass transfer during alteration. Pyrochlore is a quintessential weathering-resistant mineral accommodating most HFSEs. Here, we investigate the surface alteration layers of pyrochlore using a nanoscale approach within a well-characterized regolith subject to intense weathering over millions of years. In the profile, porous pyrochlore rims exhibit distinct chemistry with higher Th contents. Sharp chemical and textural nanometer-scale interfaces between Pb-rich and Th-rich pyrochlore provide compelling evidence for interface-coupled dissolution-reprecipitation. This demonstrates the alterability of the Nb octahedral framework in pyrochlore and the relative stability of its Th-rich counterpart during tropical weathering. Nanoscale analyses of Ce-rich pyrochlores in two additional lateritic horizons confirm the generality of this mechanism across the deposit. The presence of Nb in secondary nano-cerianite found in manganiferous veins establishes its transport during weathering. These nanomineralogical studies of secondary assemblages provide the first direct evidence of Nb mobility during weathering at the deposit scale, underscoring the need to reappraise HFSE geochemical cycles at Earth’s surface, especially in light of growing mining volumes. This paves the way for further investigations into the alteration of weathering-resistant minerals at the nanoscale, providing new models of mobilization and sequestration through previously undocumented processes.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"5 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145554316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chetan Nathwani, Emanuel Giovanini, Olivier Bachmann, Paolo Sossi, Julien Allaz, Marine Cotte, Lorenzo Candioti, Cyril Chelle-Michou
Sulfide saturation during arc magma evolution depletes ascending magmas in chalcophile elements (e.g., Cu) and promotes metal recycling into the mantle. Although sulfide saturation is posited to be delayed by high oxygen fugacity (ƒO2) in the deep crust of arcs, the timing and controls on sulfide saturation in arcs remain disputed. Here, we report new constraints on S speciation in the deep crust of arcs using measurements of the relative abundance of S species (S2−, S4+, and S6+) in apatite in deep crustal arc cumulates from the Sierra Valle Fértil−La Huerta (Argentina). Sulfide is rare in primitive cumulates (<0.01%), only becoming abundant in evolved cumulates (Mg# <0.65), indicating that sulfide saturation was delayed in the magmatic evolution. Apatite yields consistently high S6+/ΣS (0.8−1.0), giving an fO2 of 1.4 ± 0.4 log units above the fayalite-magnetite-quartz (FMQ) redox buffer. Delayed sulfide saturation was therefore the result of the parental magma having elevated fO2 acquired from its mantle source. We use modeling to show that magma differentiation at FMQ+1.4 would be sufficient to delay sulfide saturation and produce mafic to intermediate melts with elevated Cu concentrations. Oxidized, hydrous intermediate magmas may therefore play a key role in delivering elevated sulfur and Cu fluxes to magmatic-hydrothermal systems and the atmosphere, contributing to the Cu deficit of modern continental crust.
弧岩浆演化过程中的硫化物饱和耗尽上升岩浆中的亲铜元素（如Cu），促进金属再循环进入地幔。虽然在弧深地壳中，高氧逸度（ƒO2）延迟了硫化物的饱和，但弧中硫化物饱和的时间和控制仍然存在争议。本文通过对阿根廷Sierra Valle f - La Huerta地区深地壳弧堆积中磷灰石中S元素（S2−、S4+和S6+）相对丰度的测量，报道了弧深地壳中S物种形成的新限制。硫化物在原始堆积物中含量较低（<0.01%），在演化堆积物中含量较丰富（Mg# <0.65），表明岩浆演化过程中硫化物饱和度延迟。磷灰石的产率一直很高，S6+/ΣS(0.8−1.0)，在费雅石-磁铁矿-石英（FMQ）氧化还原缓冲液上的fO2为1.4±0.4 log单位。因此，延迟的硫化物饱和是母岩浆从地幔源获得的fO2升高的结果。我们利用模型表明，FMQ+1.4的岩浆分异足以延迟硫化物饱和，并产生镁基到中间的高铜浓度熔体。因此，氧化、含水的中间岩浆可能在向岩浆-热液系统和大气输送硫和铜通量的过程中发挥了关键作用，从而导致现代大陆地壳的铜亏缺。
{"title":"Sulfate-dominant apatite in the deep arc crust indicates that high oxidation state promotes copper fluxing in arcs","authors":"Chetan Nathwani, Emanuel Giovanini, Olivier Bachmann, Paolo Sossi, Julien Allaz, Marine Cotte, Lorenzo Candioti, Cyril Chelle-Michou","doi":"10.1130/g53549.1","DOIUrl":"https://doi.org/10.1130/g53549.1","url":null,"abstract":"Sulfide saturation during arc magma evolution depletes ascending magmas in chalcophile elements (e.g., Cu) and promotes metal recycling into the mantle. Although sulfide saturation is posited to be delayed by high oxygen fugacity (ƒO2) in the deep crust of arcs, the timing and controls on sulfide saturation in arcs remain disputed. Here, we report new constraints on S speciation in the deep crust of arcs using measurements of the relative abundance of S species (S2−, S4+, and S6+) in apatite in deep crustal arc cumulates from the Sierra Valle Fértil−La Huerta (Argentina). Sulfide is rare in primitive cumulates (&lt;0.01%), only becoming abundant in evolved cumulates (Mg# &lt;0.65), indicating that sulfide saturation was delayed in the magmatic evolution. Apatite yields consistently high S6+/ΣS (0.8−1.0), giving an fO2 of 1.4 ± 0.4 log units above the fayalite-magnetite-quartz (FMQ) redox buffer. Delayed sulfide saturation was therefore the result of the parental magma having elevated fO2 acquired from its mantle source. We use modeling to show that magma differentiation at FMQ+1.4 would be sufficient to delay sulfide saturation and produce mafic to intermediate melts with elevated Cu concentrations. Oxidized, hydrous intermediate magmas may therefore play a key role in delivering elevated sulfur and Cu fluxes to magmatic-hydrothermal systems and the atmosphere, contributing to the Cu deficit of modern continental crust.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"24 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145508808","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Diogo Ribeiro, Bertrand Rottier, Antoine Godet, Georges Beaudoin, Clifford G.C. Patten, Carl Guilmette, Adrian G. Rehm, Isaac S. Malta, Jochen Kolb, Douglas K. Tinkham, Iain Pitcairn
The southern Superior Province (Canada) comprises large metasedimentary belts, such as the Pontiac and Quetico subprovinces, adjacent to Au-endowed greenstone belts. The Pontiac sedimentary rocks have been proposed as a source of Au for the highly endowed southern Abitibi greenstone belt. However, a comparison with sedimentary rocks adjacent to poorly endowed greenstone belts is lacking. Here we examine a suite of metasedimentary and minor volcanic rocks collected from three transects in the Pontiac and Quetico metasedimentary belts adjacent to greenstone belts with variable Au endowments. We combine in situ Au data of sulfides in metasedimentary rocks with whole-rock ultra-low-detection Au data. Gold concentrations decrease across metamorphic isograds in the well- and moderately endowed transects, while limited Au mobility is observed in the poorly endowed transect. The release of Au from metasedimentary rocks is linked to the pyrite-pyrrhotite transition. This reaction is incomplete in the poorly endowed transect, explaining the limited Au mobility observed. Our data reveal a spatial correlation between Au mobility in metasedimentary belts and Au endowment in the adjacent greenstone belts.
{"title":"Gold mobility in Archean metasedimentary belts: Implications for orogenic gold deposits","authors":"Diogo Ribeiro, Bertrand Rottier, Antoine Godet, Georges Beaudoin, Clifford G.C. Patten, Carl Guilmette, Adrian G. Rehm, Isaac S. Malta, Jochen Kolb, Douglas K. Tinkham, Iain Pitcairn","doi":"10.1130/g53574.1","DOIUrl":"https://doi.org/10.1130/g53574.1","url":null,"abstract":"The southern Superior Province (Canada) comprises large metasedimentary belts, such as the Pontiac and Quetico subprovinces, adjacent to Au-endowed greenstone belts. The Pontiac sedimentary rocks have been proposed as a source of Au for the highly endowed southern Abitibi greenstone belt. However, a comparison with sedimentary rocks adjacent to poorly endowed greenstone belts is lacking. Here we examine a suite of metasedimentary and minor volcanic rocks collected from three transects in the Pontiac and Quetico metasedimentary belts adjacent to greenstone belts with variable Au endowments. We combine in situ Au data of sulfides in metasedimentary rocks with whole-rock ultra-low-detection Au data. Gold concentrations decrease across metamorphic isograds in the well- and moderately endowed transects, while limited Au mobility is observed in the poorly endowed transect. The release of Au from metasedimentary rocks is linked to the pyrite-pyrrhotite transition. This reaction is incomplete in the poorly endowed transect, explaining the limited Au mobility observed. Our data reveal a spatial correlation between Au mobility in metasedimentary belts and Au endowment in the adjacent greenstone belts.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"29 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145485391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hongxiang Guan, Steffen Kiel, Xiaoyan Xu, Jiachen Fan, Yi Zhang, Xiaoming Miao, Hangyu Nan, Nengyou Wu, Sanzhong Li
Chemosymbiosis-based invertebrate communities dominate deep-sea hydrothermal vents and methane seeps, but reliable methods for detecting chemosymbiosis in the fossil record and tracing its evolution into the geologic past are still lacking. Here, we investigate the lipid inventory of shells of four seep-dwelling bivalve species (from both live specimens and empty shells) hosting either methanotrophic or thiotrophic symbionts. All species share a common suite of lipids that are mostly derived from external heterotrophic sources, except for cholesterol and cholestanols in bathymodiolin mussels. The δ13C values of these sterols as low as −83‰ indicate an origin of these compounds from the animal. The transfer was independent of the symbionts being methanotrophic or thiotrophic and thus of the distinct biosynthetic pathways for cholesterol and cholestanol of these animals. This finding opens a new prospect for molecular paleontology by taking advantage of the source specificity and diagenetic stability of these compounds. It could allow tracing chemosymbiosis and its evolution into the fossil record, in particular in bathymodiolin mussels, and potentially also in other metazoan groups.
{"title":"Sterols transferred from soft tissues to bivalve shells: A new tracer of molecular paleontology","authors":"Hongxiang Guan, Steffen Kiel, Xiaoyan Xu, Jiachen Fan, Yi Zhang, Xiaoming Miao, Hangyu Nan, Nengyou Wu, Sanzhong Li","doi":"10.1130/g53933.1","DOIUrl":"https://doi.org/10.1130/g53933.1","url":null,"abstract":"Chemosymbiosis-based invertebrate communities dominate deep-sea hydrothermal vents and methane seeps, but reliable methods for detecting chemosymbiosis in the fossil record and tracing its evolution into the geologic past are still lacking. Here, we investigate the lipid inventory of shells of four seep-dwelling bivalve species (from both live specimens and empty shells) hosting either methanotrophic or thiotrophic symbionts. All species share a common suite of lipids that are mostly derived from external heterotrophic sources, except for cholesterol and cholestanols in bathymodiolin mussels. The δ13C values of these sterols as low as −83‰ indicate an origin of these compounds from the animal. The transfer was independent of the symbionts being methanotrophic or thiotrophic and thus of the distinct biosynthetic pathways for cholesterol and cholestanol of these animals. This finding opens a new prospect for molecular paleontology by taking advantage of the source specificity and diagenetic stability of these compounds. It could allow tracing chemosymbiosis and its evolution into the fossil record, in particular in bathymodiolin mussels, and potentially also in other metazoan groups.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"183 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145454983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Large, shallow earthquakes typically produce surface ruptures, whereas aftershocks rarely do. Here, we document a rare case in which the 2024 Mw 7.0 Wushi earthquake (western China) did not rupture the surface, but a Mw 5.7 aftershock did. Integrated field observations, satellite imagery, interferometric synthetic aperture radar (InSAR) data, and relocated seismicity reveal that the aftershock reactivated shallow back- and fore-thrusts, forming a pop-up structure with clear surface breaks. This event demonstrates that aftershocks can generate significant surface deformation by reactivating pre-existing shallow faults—a process not commonly accounted for in seismic hazard assessments. Our findings emphasize the need to incorporate secondary shallow faults into hazard models, especially in complex fold-and-thrust systems.
{"title":"Aftershock-induced surface ruptures overshadow the 2024 Mw 7.0 Wushi mainshock, China","authors":"Haibing Li, Jiawei Pan, Marie-Luce Chevalier, Dongliang Liu, Shiguang Wang, Heng Luo, Long Zhang, Lihua Fang, Teng Wang, Fucai Liu, Shenqiang Chen, Xiaohui He, Xunzhang Zhu, Yihu Zhang, Qiong Wu, Chunrui Li","doi":"10.1130/g54078.1","DOIUrl":"https://doi.org/10.1130/g54078.1","url":null,"abstract":"Large, shallow earthquakes typically produce surface ruptures, whereas aftershocks rarely do. Here, we document a rare case in which the 2024 Mw 7.0 Wushi earthquake (western China) did not rupture the surface, but a Mw 5.7 aftershock did. Integrated field observations, satellite imagery, interferometric synthetic aperture radar (InSAR) data, and relocated seismicity reveal that the aftershock reactivated shallow back- and fore-thrusts, forming a pop-up structure with clear surface breaks. This event demonstrates that aftershocks can generate significant surface deformation by reactivating pre-existing shallow faults—a process not commonly accounted for in seismic hazard assessments. Our findings emphasize the need to incorporate secondary shallow faults into hazard models, especially in complex fold-and-thrust systems.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"2 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145448349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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