M. Isabel Benito, I. Emma Quijada, Martín Garcia-Martín, Alejandro Pertuz, Pablo Suarez-Gonzalez, Angélica Torices, Sonia Campos-Soto
Abstract not available
无摘要
{"title":"Ice-rafted dropstones at midlatitudes in the Cretaceous of continental Iberia: COMMENT","authors":"M. Isabel Benito, I. Emma Quijada, Martín Garcia-Martín, Alejandro Pertuz, Pablo Suarez-Gonzalez, Angélica Torices, Sonia Campos-Soto","doi":"10.1130/g52006c.1","DOIUrl":"https://doi.org/10.1130/g52006c.1","url":null,"abstract":"Abstract not available","PeriodicalId":12642,"journal":{"name":"Geology","volume":"65 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140340768","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}
Chen Wu, Andrew V. Zuza, Drew A. Levy, Jie Li, Lin Ding
Abstract not available
无摘要
{"title":"Discovery of Permian–Triassic eclogite in northern Tibet establishes coeval subduction erosion along an ~3000-km-long arc: REPLY","authors":"Chen Wu, Andrew V. Zuza, Drew A. Levy, Jie Li, Lin Ding","doi":"10.1130/g52012y.1","DOIUrl":"https://doi.org/10.1130/g52012y.1","url":null,"abstract":"Abstract not available","PeriodicalId":12642,"journal":{"name":"Geology","volume":"17 5 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140000852","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}
Antoine Bénard, Dmitri A. Ionov, Oliver Nebel, Richard J. Arculus
Abstract not available
无摘要
{"title":"Boninitic melt percolation makes depleted mantle wedges rich in silica: COMMENT","authors":"Antoine Bénard, Dmitri A. Ionov, Oliver Nebel, Richard J. Arculus","doi":"10.1130/g51824c.1","DOIUrl":"https://doi.org/10.1130/g51824c.1","url":null,"abstract":"Abstract not available","PeriodicalId":12642,"journal":{"name":"Geology","volume":"73 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140015521","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}
{"title":"Discovery of Permian–Triassic eclogite in northern Tibet establishes coeval subduction erosion along an ~3000-km-long arc: COMMENT","authors":"Shuguang Song, Hafiz U. Rehman","doi":"10.1130/g51860c.1","DOIUrl":"https://doi.org/10.1130/g51860c.1","url":null,"abstract":"Abstract not available","PeriodicalId":12642,"journal":{"name":"Geology","volume":"23 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140015420","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}
M. Mohr, M. Schmitz, N. Swanson‐Hysell, K.E. Karlstrom, F.A. Macdonald, M. E. Holland, Y. Zhang, N.S. Anderson
The Southwestern Laurentia large igneous province (SWLLIP) comprises voluminous, widespread ca 1.1 Ga magmatism in the southwestern United States and northern Mexico. The timing and tempo of SWLLIP magmatism and its relationship to other late Mesoproterozoic igneous provinces have been unclear due to difficulties in dating mafic rocks at high precision. New precise U-Pb zircon dates for comagmatic felsic segregations within mafic rocks reveal distinct magmatic episodes at ca. 1098 Ma (represented by massive sills in Death Valley, California, the Grand Canyon, and central Arizona) and ca. 1083 Ma (represented by the Cardenas Basalts in the Grand Canyon and a sill in the Dead Mountains, California). The ca. 1098 Ma magmatic pulse was short-lived, lasting 0.25 –0.24 +0.67 m.y., and voluminous and widespread, evidenced by the ≥100 m sills in Death Valley, the Grand Canyon, and central Arizona, consistent with decompression melting of an upwelling mantle plume. The ca. 1083 Ma magmatism may have been generated by a secondary plume pulse or post-plume lithosphere extension. The ca. 1098 Ma pulse of magmatism in southwestern Laurentia occurred ∼2 m.y. prior to an anomalous renewal of voluminous melt generation in the Midcontinent Rift of central Laurentia that is recorded by the ca. 1096 Ma Duluth Complex layered mafic intrusions. Rates of lateral plume spread predicted by mantle plume lubrication theory support a model where a plume derived from the deep mantle impinged near southwestern Laurentia, then spread to thinned Midcontinent Rift lithosphere over ∼2 m.y. to elevate mantle temperatures and generate melt. This geodynamic hypothesis reconciles the close temporal relationships between voluminous magmatism across Laurentia and provides an explanation for that anomalous renewal of high magmatic flux within the protracted magmatic history of the Midcontinent Rift.
西南劳伦西亚大型火成岩带（SWLLIP）包括美国西南部和墨西哥北部大量、广泛的约1.1 Ga岩浆活动。由于难以对岩浆岩进行高精度的年代测定，SWLLIP岩浆活动的时间和节奏及其与其他中新生代晚期火成岩带的关系一直不明确。新的锆石U-Pb精确年代测定显示，黑云母岩中的杂岩性长英岩分块在大约1098Ma（以块状长英岩为代表）时发生了不同的岩浆活动。1098 Ma（以加利福尼亚州死亡谷、大峡谷和亚利桑那州中部的块状岩屑为代表）和约 1083 Ma（以大峡谷的卡德纳斯玄武岩和加利福尼亚州死亡山脉的岩屑为代表）。约大约 1098 Ma 的岩浆脉冲持续时间短，仅为 0.25 -0.24 +0.67 m.y.，岩浆量大，范围广，死亡谷、大峡谷和亚利桑那州中部≥100 m 的岩屑就是证明，这与上涌地幔羽流的减压熔融一致。约约 1083 Ma 的岩浆活动可能是由次级羽流脉冲或羽流后岩石圈延伸产生的。约 1098 Ma 的岩浆活动脉冲劳伦提亚西南部约 1098 Ma 的岩浆活动发生在劳伦提亚中部中洲裂谷大量熔融活动异常更新之前 2 m.y.，该活动由约 1096 Ma 的 Duluth Complex 记录。1096 Ma Duluth Complex层状岩浆侵入体所记录的。地幔羽流润滑理论预测的横向羽流扩散速率支持这样一个模型，即来自深地幔的羽流在劳伦提亚西南部附近撞击，然后扩散到中洲裂谷减薄的岩石圈，经过∼2 m.y.，使地幔温度升高并产生熔体。这一地球动力学假说调和了劳伦提亚各地大量岩浆活动之间的密切时间关系，并为中洲裂谷漫长岩浆史中的高岩浆通量异常更新提供了解释。
{"title":"High-precision U-Pb geochronology links magmatism in the Southwestern Laurentia large igneous province and Midcontinent Rift","authors":"M. Mohr, M. Schmitz, N. Swanson‐Hysell, K.E. Karlstrom, F.A. Macdonald, M. E. Holland, Y. Zhang, N.S. Anderson","doi":"10.1130/g51786.1","DOIUrl":"https://doi.org/10.1130/g51786.1","url":null,"abstract":"The Southwestern Laurentia large igneous province (SWLLIP) comprises voluminous, widespread ca 1.1 Ga magmatism in the southwestern United States and northern Mexico. The timing and tempo of SWLLIP magmatism and its relationship to other late Mesoproterozoic igneous provinces have been unclear due to difficulties in dating mafic rocks at high precision. New precise U-Pb zircon dates for comagmatic felsic segregations within mafic rocks reveal distinct magmatic episodes at ca. 1098 Ma (represented by massive sills in Death Valley, California, the Grand Canyon, and central Arizona) and ca. 1083 Ma (represented by the Cardenas Basalts in the Grand Canyon and a sill in the Dead Mountains, California). The ca. 1098 Ma magmatic pulse was short-lived, lasting 0.25 –0.24 +0.67 m.y., and voluminous and widespread, evidenced by the ≥100 m sills in Death Valley, the Grand Canyon, and central Arizona, consistent with decompression melting of an upwelling mantle plume. The ca. 1083 Ma magmatism may have been generated by a secondary plume pulse or post-plume lithosphere extension.\u0000 The ca. 1098 Ma pulse of magmatism in southwestern Laurentia occurred ∼2 m.y. prior to an anomalous renewal of voluminous melt generation in the Midcontinent Rift of central Laurentia that is recorded by the ca. 1096 Ma Duluth Complex layered mafic intrusions. Rates of lateral plume spread predicted by mantle plume lubrication theory support a model where a plume derived from the deep mantle impinged near southwestern Laurentia, then spread to thinned Midcontinent Rift lithosphere over ∼2 m.y. to elevate mantle temperatures and generate melt. This geodynamic hypothesis reconciles the close temporal relationships between voluminous magmatism across Laurentia and provides an explanation for that anomalous renewal of high magmatic flux within the protracted magmatic history of the Midcontinent Rift.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"49 11","pages":""},"PeriodicalIF":5.8,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139442155","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}
Matthias Sinnesael, Andrew R. Millard, Martin R. Smith
The first occurrence of trilobites at ca. 520 Ma is an iconic feature of the Cambrian Explosion. Developing a robust evolutionary view on early Cambrian life is generally hindered by large uncertainties in the ages of fossil finds and their global stratigraphic correlation. We developed an astrochronological interpretation for the Tiout section in Morocco that features some of the oldest trilobite fossils. Our novel approach to incorporating individual astronomical cycle durations in an integrated radioisotopic and astrochronological Bayesian age-depth model results in an age estimate of 519.62 Ma (519.70−519.54 Ma 95% highest posterior distribution) for the first occurrence of trilobites in West Gondwana. This level of precise age estimation is exceptional for biological events in deep time and demonstrates the power of our novel approach.
约 520 Ma 时首次出现三叶虫是寒武纪大爆发的标志性特征。520 Ma 是寒武纪大爆发的标志性特征。由于化石发现的年代及其全球地层相关性存在很大的不确定性，因此通常无法对寒武纪早期的生命进化形成有力的看法。我们对摩洛哥Tiout地段进行了天文年代学解释，该地段有一些最古老的三叶虫化石。我们采用新颖的方法，将单个天文周期的持续时间纳入一个综合的放射性同位素和天体年代学贝叶斯年龄深度模型，得出了西冈瓦纳首次出现三叶虫的年龄估计值为 519.62 Ma（519.70-519.54 Ma 95% 最高后验分布）。这种精确的年龄估计水平对于深时生物事件来说是绝无仅有的，同时也证明了我们新方法的威力。
{"title":"A Bayesian astrochronology for the Cambrian first occurrence of trilobites in West Gondwana (Morocco)","authors":"Matthias Sinnesael, Andrew R. Millard, Martin R. Smith","doi":"10.1130/g51718.1","DOIUrl":"https://doi.org/10.1130/g51718.1","url":null,"abstract":"The first occurrence of trilobites at ca. 520 Ma is an iconic feature of the Cambrian Explosion. Developing a robust evolutionary view on early Cambrian life is generally hindered by large uncertainties in the ages of fossil finds and their global stratigraphic correlation. We developed an astrochronological interpretation for the Tiout section in Morocco that features some of the oldest trilobite fossils. Our novel approach to incorporating individual astronomical cycle durations in an integrated radioisotopic and astrochronological Bayesian age-depth model results in an age estimate of 519.62 Ma (519.70−519.54 Ma 95% highest posterior distribution) for the first occurrence of trilobites in West Gondwana. This level of precise age estimation is exceptional for biological events in deep time and demonstrates the power of our novel approach.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"20 11","pages":""},"PeriodicalIF":5.8,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139445658","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}
Sajjad Akam, Pei-Chuan Chuang, Sergei Katsev, C. Wittkop, Michelle Chamberlain, Andrew W. Dale, Klaus Wallmann, Adam J. Heathcote, E. Swanner
The greenhouse gas methane (CH4) contributed to a warm climate that maintained liquid water and sustained Earth’s habitability in the Precambrian despite the faint young sun. The viability of methanogenesis (ME) in ferruginous environments, however, is debated, as iron reduction can potentially outcompete ME as a pathway of organic carbon remineralization (OCR). Here, we document that ME is a dominant OCR process in Brownie Lake, Minnesota (midwestern United States), which is a ferruginous (iron-rich, sulfate-poor) and meromictic (stratified with permanent anoxic bottom waters) system. We report ME accounting for ≥90% and >9% ± 7% of the anaerobic OCR in the water column and sediments, respectively, and an overall particulate organic carbon loading to CH4 conversion efficiency of ≥18% ± 7% in the anoxic zone of Brownie Lake. Our results, along with previous reports from ferruginous systems, suggest that even under low primary productivity in Precambrian oceans, the efficient conversion of organic carbon would have enabled marine CH4 to play a major role in early Earth’s biogeochemical evolution.
{"title":"Methane-carbon budget of a ferruginous meromictic lake and implications for marine methane dynamics on early Earth","authors":"Sajjad Akam, Pei-Chuan Chuang, Sergei Katsev, C. Wittkop, Michelle Chamberlain, Andrew W. Dale, Klaus Wallmann, Adam J. Heathcote, E. Swanner","doi":"10.1130/g51713.1","DOIUrl":"https://doi.org/10.1130/g51713.1","url":null,"abstract":"The greenhouse gas methane (CH4) contributed to a warm climate that maintained liquid water and sustained Earth’s habitability in the Precambrian despite the faint young sun. The viability of methanogenesis (ME) in ferruginous environments, however, is debated, as iron reduction can potentially outcompete ME as a pathway of organic carbon remineralization (OCR). Here, we document that ME is a dominant OCR process in Brownie Lake, Minnesota (midwestern United States), which is a ferruginous (iron-rich, sulfate-poor) and meromictic (stratified with permanent anoxic bottom waters) system. We report ME accounting for ≥90% and >9% ± 7% of the anaerobic OCR in the water column and sediments, respectively, and an overall particulate organic carbon loading to CH4 conversion efficiency of ≥18% ± 7% in the anoxic zone of Brownie Lake. Our results, along with previous reports from ferruginous systems, suggest that even under low primary productivity in Precambrian oceans, the efficient conversion of organic carbon would have enabled marine CH4 to play a major role in early Earth’s biogeochemical evolution.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"59 3","pages":""},"PeriodicalIF":5.8,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139383523","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}
K. Konrad, Matthew G. Jackson, Bernhard Steinberger, A. Koppers, Andrea Marie Balbas, Valerie Finlayson, J. Konter, Allison Price
Age-progressive seamount tracks generated by lithospheric motion over a stationary mantle plume have long been used to reconstruct absolute plate motion (APM) models. However, the basis of these models requires the plumes to move significantly slower than the overriding lithosphere. When a plume interacts with a convergent or divergent plate boundary, it is often deflected within the strong local mantle flow fields associated with such regimes. Here, we examined the age progression and geometry of the Samoa hotspot track, focusing on lava flow samples dredged from the deep flanks of seamounts in order to best reconstruct when a given seamount was overlying the mantle plume (i.e., during the shield-building stage). The Samoan seamounts display an apparent local plate velocity of 7.8 cm/yr from 0 to 9 Ma, 11.1 cm/yr from 9 to 14 Ma, and 5.6 cm/yr from 14 to 24 Ma. Current fixed and mobile hotspot Pacific APM models cannot reproduce the geometry of the Samoa seamount track if a long-term fixed hotspot location, currently beneath the active Vailulu’u Seamount, is assumed. Rather, reconstruction of the eruptive locations of the Samoan seamounts using APM models indicates that the surface expression of the plume migrated ∼2° northward in the Pliocene. Large-scale mantle flow beneath the Pacific Ocean Basin cannot explain this plume migration. Instead, the best explanation is that toroidal flow fields—generated by westward migration of the Tonga Trench and associated slab rollback—have deflected the conduit northward over the past 2−3 m.y. These observations provide novel constraints on the ways in which plume-trench interactions can alter hotspot track geometries.
长期以来，人们一直利用岩石圈在静止的地幔羽流上运动所产生的年龄递增海山轨迹来重建绝对板块运动（APM）模型。然而，这些模型的基础要求地幔羽流的运动速度明显慢于覆盖岩石圈的速度。当羽流与辐合或发散板块边界相互作用时，它通常会在与这些机制相关的强局部地幔流场中发生偏转。在这里，我们研究了萨摩亚热点轨道的年龄演化和几何形状，重点是从海山深侧挖出的熔岩流样本，以便最好地重建特定海山何时覆盖地幔羽流（即在盾牌形成阶段）。萨摩亚海山的表观板块速度在 0 至 9 Ma 为 7.8 厘米/年，9 至 14 Ma 为 11.1 厘米/年，14 至 24 Ma 为 5.6 厘米/年。如果假定一个长期固定的热点位置（目前在活跃的维鲁鲁海山之下），那么目前的太平洋固定和移动热点APM模型就无法再现萨摩亚海山轨道的几何形状。相反，利用 APM 模型重建萨摩亚海山的喷发位置表明，羽流的表面表达在上新世向北迁移了 2°。太平洋海盆下的大规模地幔流动无法解释这种羽流迁移。相反，最好的解释是汤加海沟西移和相关的板块回滚产生的环状流场在过去2-3 m.y.使导管向北偏转。
{"title":"Toroidal flow around the Tonga slab moved the Samoan plume during the Pliocene","authors":"K. Konrad, Matthew G. Jackson, Bernhard Steinberger, A. Koppers, Andrea Marie Balbas, Valerie Finlayson, J. Konter, Allison Price","doi":"10.1130/g51588.1","DOIUrl":"https://doi.org/10.1130/g51588.1","url":null,"abstract":"Age-progressive seamount tracks generated by lithospheric motion over a stationary mantle plume have long been used to reconstruct absolute plate motion (APM) models. However, the basis of these models requires the plumes to move significantly slower than the overriding lithosphere. When a plume interacts with a convergent or divergent plate boundary, it is often deflected within the strong local mantle flow fields associated with such regimes. Here, we examined the age progression and geometry of the Samoa hotspot track, focusing on lava flow samples dredged from the deep flanks of seamounts in order to best reconstruct when a given seamount was overlying the mantle plume (i.e., during the shield-building stage). The Samoan seamounts display an apparent local plate velocity of 7.8 cm/yr from 0 to 9 Ma, 11.1 cm/yr from 9 to 14 Ma, and 5.6 cm/yr from 14 to 24 Ma. Current fixed and mobile hotspot Pacific APM models cannot reproduce the geometry of the Samoa seamount track if a long-term fixed hotspot location, currently beneath the active Vailulu’u Seamount, is assumed. Rather, reconstruction of the eruptive locations of the Samoan seamounts using APM models indicates that the surface expression of the plume migrated ∼2° northward in the Pliocene. Large-scale mantle flow beneath the Pacific Ocean Basin cannot explain this plume migration. Instead, the best explanation is that toroidal flow fields—generated by westward migration of the Tonga Trench and associated slab rollback—have deflected the conduit northward over the past 2−3 m.y. These observations provide novel constraints on the ways in which plume-trench interactions can alter hotspot track geometries.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"3 4","pages":""},"PeriodicalIF":5.8,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139389517","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}
A.N. Martin, E. Stüeken, J.A.-S. Michaud, C. Münker, S. Weyer, E.H.P. van Hees, M.M. Gehringer
The biological nitrogen (N) cycle on early Earth is enigmatic because of limited data from Archean (meta-)sediments and the potential alteration of primary biotic signatures. Here we further investigate unusual 15N enrichments reported in 2.7 Ga meta-sediments from the Abitibi greenstone belt, Canada, purportedly related to a 15N-enriched Archean atmosphere. Given that sediments from this region are contemporaneous with large-scale volcanogenic massive sulfide deposits, we utilize Cu and Zn contents to trace the effects of hydrothermal circulation on N isotope fractionation. We show that high δ15Nbulk values as high as +23‰ are associated with Cu-Zn mineralization, whereas unmineralized organic-rich shales exhibit much lower δ15Nbulk and δ15Nkerogen values. Moreover, we find a large offset between δ15Nbulk and δ15Nkerogen of as much as 17‰ and relate this to the addition of organic-bound N during the late-stage emplacement of organic-rich veins. We conclude that the previously reported high δ15N values are most parsimoniously explained by biotic and abiotic mechanisms rather than a 15N-enriched atmosphere. Crucially, both mechanisms require the presence of NH4+ in hydrothermal fluids, supporting the hypothesis that hydrothermal discharge was an important nutrient source for Neoarchean marine life.
早期地球上的生物氮（N）循环是一个谜，因为来自Archean（元）沉积物的数据有限，而且原始生物特征可能被改变。在这里，我们进一步研究了加拿大阿比提比绿岩带 2.7 Ga 元沉积物中报告的异常 15N 富集，据称这与 15N 富集的 Archean 大气有关。鉴于该地区的沉积物与大规模火山成因块状硫化物矿床同时存在，我们利用铜和锌的含量来追踪热液循环对 N 同位素分馏的影响。我们发现，高达+23‰的δ15Nbulk值与铜锌矿化有关，而未矿化的富含有机质页岩的δ15Nbulk和δ15Nkerogen值则低得多。此外，我们还发现δ15Nbulk与δ15Nkerogen之间存在高达17‰的巨大偏移，这与富含有机质的矿脉在后期置换过程中增加了有机结合氮有关。我们的结论是，以前报道的高δ15N值最有可能由生物和非生物机制而不是富含15N的大气层来解释。最重要的是，这两种机制都需要热液中存在 NH4+，这支持了热液排放是新石器时代海洋生物重要营养源的假说。
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