Zhiguo Li, Ruoyuan Qiu, Thomas J. Algeo, Mingyu Zhao, Ting Chen, Yi Song, Geoffrey J. Gilleaudeau, Yefang Xing, Fang Huang, Genming Luo, Shucheng Xie
The relationship of oceanic anoxia to changes in marine productivity during the biocrises of the Late Devonian remains uncertain. We present zinc isotope (δ66Zn) data from the euxinic Upper Devonian Chattanooga Shale in the Dupont GHS core (Tennessee, USA), reflecting the Zn isotopic composition of Late Devonian seawater. From the lower Frasnian to the upper Famennian, δ66Zn values gradually increase, indicating a progressive rise in marine productivity. Strong correlations of this shift with redox proxies (UEF, MoEF, Corg/P; │r│ > 0.88; p <0.001; EF—enrichment factor) suggest that increased productivity was a key cause of contemporaneous marine euxinia and heightened ecological stress. Biomarker data record increasing inputs of terrestrial organic matter from higher plants, closely paralleling the shift in seawater Zn isotopes (r = +0.73; p < 0.005). These collectively suggest that the enhanced terrestrial phosphorus flux associated with the expansion of terrestrial higher plants was the primary driver for the observed δ66Zn patterns (r = +0.88, root mean square error = 0.11‰). Our study highlights the potential role of rising marine primary productivity in triggering Late Devonian ecological crises (e.g., the Dasberg Event), providing a cautionary parallel to the expansion of modern coastal dead zones.
在晚泥盆纪生物危机期间，海洋缺氧与海洋生产力变化的关系仍然不确定。本文报道了美国田纳西州Dupont GHS岩心中上泥盆统Chattanooga页岩的锌同位素δ66Zn，反映了晚泥盆统海水的锌同位素组成。从下弗拉斯纪到上法门纪，δ66Zn值逐渐增大，表明海洋生产力逐渐上升。这种转变与氧化还原指标（UEF、MoEF、Corg/P；│r│> 0.88; P <0.001； ef富集因子）的强相关性表明，生产力的提高是同期海洋缺氧和生态压力加剧的关键原因。生物标志物数据显示，来自高等植物的陆源有机质输入增加，与海水锌同位素的变化密切相关（r = +0.73; p < 0.005）。这些结果表明，与陆生高等植物扩张相关的陆地磷通量增强是观测到的δ66Zn模式的主要驱动因素（r = +0.88，均方根误差= 0.11‰）。我们的研究强调了海洋初级生产力上升在引发泥盆纪晚期生态危机（如Dasberg事件）方面的潜在作用，提供了与现代沿海死亡区扩张类似的警示。
{"title":"Rising productivity drove marine euxinia during the Late Devonian mass extinctions","authors":"Zhiguo Li, Ruoyuan Qiu, Thomas J. Algeo, Mingyu Zhao, Ting Chen, Yi Song, Geoffrey J. Gilleaudeau, Yefang Xing, Fang Huang, Genming Luo, Shucheng Xie","doi":"10.1130/g54182.1","DOIUrl":"https://doi.org/10.1130/g54182.1","url":null,"abstract":"The relationship of oceanic anoxia to changes in marine productivity during the biocrises of the Late Devonian remains uncertain. We present zinc isotope (δ66Zn) data from the euxinic Upper Devonian Chattanooga Shale in the Dupont GHS core (Tennessee, USA), reflecting the Zn isotopic composition of Late Devonian seawater. From the lower Frasnian to the upper Famennian, δ66Zn values gradually increase, indicating a progressive rise in marine productivity. Strong correlations of this shift with redox proxies (UEF, MoEF, Corg/P; │r│ &gt; 0.88; p &lt;0.001; EF—enrichment factor) suggest that increased productivity was a key cause of contemporaneous marine euxinia and heightened ecological stress. Biomarker data record increasing inputs of terrestrial organic matter from higher plants, closely paralleling the shift in seawater Zn isotopes (r = +0.73; p &lt; 0.005). These collectively suggest that the enhanced terrestrial phosphorus flux associated with the expansion of terrestrial higher plants was the primary driver for the observed δ66Zn patterns (r = +0.88, root mean square error = 0.11‰). Our study highlights the potential role of rising marine primary productivity in triggering Late Devonian ecological crises (e.g., the Dasberg Event), providing a cautionary parallel to the expansion of modern coastal dead zones.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"15 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145968338","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}
Deep-sea hydrothermal vents are sites where thermal energy from Earth’s interior is emitted into the ocean, and sulfide- or sulfate-rich chimneys form by mixing of hydrothermal fluids and ambient cold seawater. Sulfide minerals are semiconductors and can convert thermal to electrical energy. However, regardless of the high-temperature difference (up to 400 °C) between vent fluids and seawater, the significance of thermoelectric power generation by chimneys is poorly understood. We measured the electrical conductivity and thermoelectromotive force (TEMF) of typical sulfide minerals and each part of zoned chimney walls from seafloor hydrothermal vents to evaluate their thermoelectric conversion. Young and porous chimneys consist mainly of fine-grained sulfate and Zn sulfide, with extremely low electrical conductivity, resulting in no thermoelectric conversion. In contrast, mature chimneys with inner walls rich in Cu, Fe, and Pb sulfides are n-type semiconductors with a high thermoelectric conversion performance. Given a temperature difference of 200−300 °C between the vent fluids and ambient seawater, the TEMF of the mature chimneys approaches 10−210 mV, which is comparable to the redox potential between vent fluids and seawater (∼500 mV). This TEMF could play an essential role as a power source to overcome the overpotential required for the redox reactions at both sides of the chimney walls. Our findings suggest that seafloor chimneys are a unique self-organized thermoelectric conversion system that supplies substantial electrical energy to deep-sea ecosystems.
{"title":"Self-organized thermoelectric conversion systems on the deep seafloor","authors":"Atsushi Okamoto, Misaki Takahashi, Yoshinori Sato, Ryoichi Yamada, Kentaro Toda, Tomonori Ihara, Tatsuo Nozaki","doi":"10.1130/g53463.1","DOIUrl":"https://doi.org/10.1130/g53463.1","url":null,"abstract":"Deep-sea hydrothermal vents are sites where thermal energy from Earth’s interior is emitted into the ocean, and sulfide- or sulfate-rich chimneys form by mixing of hydrothermal fluids and ambient cold seawater. Sulfide minerals are semiconductors and can convert thermal to electrical energy. However, regardless of the high-temperature difference (up to 400 °C) between vent fluids and seawater, the significance of thermoelectric power generation by chimneys is poorly understood. We measured the electrical conductivity and thermoelectromotive force (TEMF) of typical sulfide minerals and each part of zoned chimney walls from seafloor hydrothermal vents to evaluate their thermoelectric conversion. Young and porous chimneys consist mainly of fine-grained sulfate and Zn sulfide, with extremely low electrical conductivity, resulting in no thermoelectric conversion. In contrast, mature chimneys with inner walls rich in Cu, Fe, and Pb sulfides are n-type semiconductors with a high thermoelectric conversion performance. Given a temperature difference of 200−300 °C between the vent fluids and ambient seawater, the TEMF of the mature chimneys approaches 10−210 mV, which is comparable to the redox potential between vent fluids and seawater (∼500 mV). This TEMF could play an essential role as a power source to overcome the overpotential required for the redox reactions at both sides of the chimney walls. Our findings suggest that seafloor chimneys are a unique self-organized thermoelectric conversion system that supplies substantial electrical energy to deep-sea ecosystems.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"21 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145947287","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}
Samuel L. Nicholson, Matthew J. Jacobson, Monika Markowska, Julian Schröder, Hubert B. Vonhof, Gerald H. Haug
Speleothems are high-quality archives of past climatic information. They have been crucial in revealing past changes in annual precipitation (AP), and their presence in water-limited arid regions is used as direct evidence for past wetter climates. However, the exact climate parameters constraining their deposition are unclear. A regionally specific AP-based minimum of 300−350 mm yr−1 has been applied but has not been widely tested and does not explicitly consider other important factors (temperature, evaporation, and topography). Here, we combine field observations of speleothem deposition with logistic regression (LR) and random forest (RF) statistical models to identify the climatic constraints controlling the modern distribution of active and inactive speleothems over a broad geographic region (SW Asia). Using a suite of climatological information related to precipitation, evaporation, temperature, and topography, LR shows that as AP increases, so does the probability of speleothem deposition. However, there is no clear threshold at which speleothem deposition is more likely. This shows a single parameter value cannot be used to determine speleothem deposition across the region. RF combines the effects of several climate metrics to predict areas of active speleothem deposition in SW Asia.
洞穴主题是过去气候信息的高质量档案。它们在揭示过去年降水量（AP）的变化方面起着至关重要的作用，它们在水资源有限的干旱地区的存在被用作过去潮湿气候的直接证据。然而，限制它们沉积的确切气候参数尚不清楚。已经应用了基于区域特定ap的最小值300 - 350 mm yr - 1，但尚未进行广泛测试，并且没有明确考虑其他重要因素（温度、蒸发和地形）。在此，我们将洞穴沉积物的野外观测与逻辑回归（LR）和随机森林（RF）统计模型相结合，以确定在广泛的地理区域（西南亚）控制活跃和不活跃洞穴沉积物现代分布的气候约束。利用一系列与降水、蒸发、温度和地形相关的气候信息，LR表明，随着AP的增加，洞穴沉积的可能性也随之增加。然而，没有明确的阈值，在这个阈值上洞穴沉积更有可能发生。这表明单一参数值不能用于确定整个地区的洞穴沉积。RF结合了几种气候指标的影响来预测西南亚活跃的洞穴沉积区域。
{"title":"The climatic constraints on speleothem deposition in SW Asia","authors":"Samuel L. Nicholson, Matthew J. Jacobson, Monika Markowska, Julian Schröder, Hubert B. Vonhof, Gerald H. Haug","doi":"10.1130/g54103.1","DOIUrl":"https://doi.org/10.1130/g54103.1","url":null,"abstract":"Speleothems are high-quality archives of past climatic information. They have been crucial in revealing past changes in annual precipitation (AP), and their presence in water-limited arid regions is used as direct evidence for past wetter climates. However, the exact climate parameters constraining their deposition are unclear. A regionally specific AP-based minimum of 300−350 mm yr−1 has been applied but has not been widely tested and does not explicitly consider other important factors (temperature, evaporation, and topography). Here, we combine field observations of speleothem deposition with logistic regression (LR) and random forest (RF) statistical models to identify the climatic constraints controlling the modern distribution of active and inactive speleothems over a broad geographic region (SW Asia). Using a suite of climatological information related to precipitation, evaporation, temperature, and topography, LR shows that as AP increases, so does the probability of speleothem deposition. However, there is no clear threshold at which speleothem deposition is more likely. This shows a single parameter value cannot be used to determine speleothem deposition across the region. RF combines the effects of several climate metrics to predict areas of active speleothem deposition in SW Asia.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"35 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145947288","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}
Lucy C. Webb, Francis A. Macdonald, Galen P. Halverson, Chadlin M. Ostrander, Sune G. Nielsen, Erik A. Sperling
Estimating dissolved oxygen (O2) concentrations in seawater during the Neoproterozoic is central to testing hypotheses about the role of O2 in animal evolution. Here we apply the thallium (Tl) isotope redox proxy to samples stratigraphically below the ca. 810-million-year-old (Ma) Bitter Springs Carbon Isotope Excursion and spanning the interval between the two Snowball Earth glaciations (ca. 662−650 Ma) to constrain the evolution of Neoproterozoic bottom water redox conditions. Thallium isotopes can be used to reconstruct the global extent of oxygenated oceanic bottom waters because the primary control on seawater Tl isotope compositions (ε205Tl) over million-year time scales is changes in the amount of 205Tl removal by Mn oxides on the seafloor. Samples spanning an ∼20-m.y. period preceding the Bitter Springs excursion from the Tonian Reefal Assemblage (n = 18/30) yield ε205Tlauth values lower than global oceanic inputs (ε205Tl ∼−2‱), with some samples approaching the modern seawater ε205Tl value of −6‱. These sustained low ε205Tlauth values require enhanced burial of Mn oxides elsewhere on the seafloor, which we interpret as evidence for the oxygenation of the deep ocean in the Tonian. In contrast, the majority of samples from the Cryogenian Hay Creek Group (n = 13/16) yield ε205Tlauth values similar to global oceanic inputs, suggesting that the deep ocean was not ventilated at this time. This indicates that Earth’s deep ocean was not gradually oxygenated throughout the Neoproterozoic, but rather experienced intervals of increased and decreased O2 concentrations.
{"title":"Thallium isotopic evidence for the Tonian rise and Cryogenian fall of Neoproterozoic oxygen levels","authors":"Lucy C. Webb, Francis A. Macdonald, Galen P. Halverson, Chadlin M. Ostrander, Sune G. Nielsen, Erik A. Sperling","doi":"10.1130/g53625.1","DOIUrl":"https://doi.org/10.1130/g53625.1","url":null,"abstract":"Estimating dissolved oxygen (O2) concentrations in seawater during the Neoproterozoic is central to testing hypotheses about the role of O2 in animal evolution. Here we apply the thallium (Tl) isotope redox proxy to samples stratigraphically below the ca. 810-million-year-old (Ma) Bitter Springs Carbon Isotope Excursion and spanning the interval between the two Snowball Earth glaciations (ca. 662−650 Ma) to constrain the evolution of Neoproterozoic bottom water redox conditions. Thallium isotopes can be used to reconstruct the global extent of oxygenated oceanic bottom waters because the primary control on seawater Tl isotope compositions (ε205Tl) over million-year time scales is changes in the amount of 205Tl removal by Mn oxides on the seafloor. Samples spanning an ∼20-m.y. period preceding the Bitter Springs excursion from the Tonian Reefal Assemblage (n = 18/30) yield ε205Tlauth values lower than global oceanic inputs (ε205Tl ∼−2‱), with some samples approaching the modern seawater ε205Tl value of −6‱. These sustained low ε205Tlauth values require enhanced burial of Mn oxides elsewhere on the seafloor, which we interpret as evidence for the oxygenation of the deep ocean in the Tonian. In contrast, the majority of samples from the Cryogenian Hay Creek Group (n = 13/16) yield ε205Tlauth values similar to global oceanic inputs, suggesting that the deep ocean was not ventilated at this time. This indicates that Earth’s deep ocean was not gradually oxygenated throughout the Neoproterozoic, but rather experienced intervals of increased and decreased O2 concentrations.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"37 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894959","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}
Meiyun Huang, Shujuan Jiao, Tim E. Johnson, Chris Clark, Jie Yu, Guangyu Huang, Jinghui Guo
Eclogite-facies rocks record deep burial and exhumation of crust, and on the modern Earth are most commonly associated with subduction settings. The scarcity of blueschist- and eclogite-facies metamorphism from the Archean rock record indicates either that subduction was not operative or that the evidence has somehow been destroyed. We report an eclogite-facies mineral association (phengite + kyanite + rutile) preserved, with quartz, as inclusions within garnet porphyroblasts in a putative metasedimentary rock from the Lewisian Gneiss Complex in northwest Scotland, part of the North Atlantic craton. In situ Lu−Hf dating of garnet constrains eclogite-facies metamorphism to the Mesoarchean to Neoarchean transition at 2.81 ± 0.04 Ga. Phase equilibrium modeling, Zr-in-rutile thermometry, and phengite barometry constrain pressures (P) to 1.5−2.5 GPa and temperatures (T) to 580−660 °C, corresponding to thermobaric ratios (T/P) between 230 °C/GPa and 440 °C/GPa, markedly cooler than recorded by metamorphic rocks of a similar age elsewhere. The low T/P ratios may provide an early record of the transition from some pre-plate tectonic regime to one with an increasing role for stable subduction, and which ultimately became plate tectonics. This transition reflects thickening and strengthening of the lithosphere, the inevitable long-term consequence of secular cooling of the mantle.
{"title":"Eclogite-facies metamorphism of continental crust at the Mesoarchean-to-Neoarchean transition","authors":"Meiyun Huang, Shujuan Jiao, Tim E. Johnson, Chris Clark, Jie Yu, Guangyu Huang, Jinghui Guo","doi":"10.1130/g53819.1","DOIUrl":"https://doi.org/10.1130/g53819.1","url":null,"abstract":"Eclogite-facies rocks record deep burial and exhumation of crust, and on the modern Earth are most commonly associated with subduction settings. The scarcity of blueschist- and eclogite-facies metamorphism from the Archean rock record indicates either that subduction was not operative or that the evidence has somehow been destroyed. We report an eclogite-facies mineral association (phengite + kyanite + rutile) preserved, with quartz, as inclusions within garnet porphyroblasts in a putative metasedimentary rock from the Lewisian Gneiss Complex in northwest Scotland, part of the North Atlantic craton. In situ Lu−Hf dating of garnet constrains eclogite-facies metamorphism to the Mesoarchean to Neoarchean transition at 2.81 ± 0.04 Ga. Phase equilibrium modeling, Zr-in-rutile thermometry, and phengite barometry constrain pressures (P) to 1.5−2.5 GPa and temperatures (T) to 580−660 °C, corresponding to thermobaric ratios (T/P) between 230 °C/GPa and 440 °C/GPa, markedly cooler than recorded by metamorphic rocks of a similar age elsewhere. The low T/P ratios may provide an early record of the transition from some pre-plate tectonic regime to one with an increasing role for stable subduction, and which ultimately became plate tectonics. This transition reflects thickening and strengthening of the lithosphere, the inevitable long-term consequence of secular cooling of the mantle.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"22 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894960","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}
Contourite channels and moats are integral to contourite depositional systems in deepwater sedimentary environments. Many channels and moats worldwide share significant sedimentary and stratigraphic complexity along with time-scale variability. Prominent shifts in morphology translate to shifts in stacking pattern through both space and time. Contourite channels evolve from subtle depressions on a terrace, with a predominantly aggradational sedimentary stacking pattern, to narrow and deep moats in both aggradational and progradational configurations with incision and infill phases. Moreover, shifts in facies distribution reflects evolutionary changes within and along channels and moats. These variations depict a long-term transformation from weaker to stronger bottom currents, punctuated by millennial and sub-millennial periods of intermittent activity. These are driven by diverse oceanographic and tectonic processes that govern bottom current dynamics and sediment supply. We illustrate these concepts based on the Pliocene−Quaternary channels and moats along the northern middle slope of the Gulf of Cádiz (along the southwestern Iberian Peninsula). There, the margin paleo-morphology, in particular the presence of canyons, affects the evolution of channels and moats due to short-term intermittency and variations of the Mediterranean Outflow Water. Our study offers new perspectives on contourite depositional systems; in particular, our understanding of channels and moats and their potential role in CO2 storage—impacting the twenty-first−century energy transition.
{"title":"Intermittent behavior of bottom currents: The complexity of channels and moats","authors":"W. Phothadee, F.J. Hernández-Molina, E. Llave","doi":"10.1130/g53949.1","DOIUrl":"https://doi.org/10.1130/g53949.1","url":null,"abstract":"Contourite channels and moats are integral to contourite depositional systems in deepwater sedimentary environments. Many channels and moats worldwide share significant sedimentary and stratigraphic complexity along with time-scale variability. Prominent shifts in morphology translate to shifts in stacking pattern through both space and time. Contourite channels evolve from subtle depressions on a terrace, with a predominantly aggradational sedimentary stacking pattern, to narrow and deep moats in both aggradational and progradational configurations with incision and infill phases. Moreover, shifts in facies distribution reflects evolutionary changes within and along channels and moats. These variations depict a long-term transformation from weaker to stronger bottom currents, punctuated by millennial and sub-millennial periods of intermittent activity. These are driven by diverse oceanographic and tectonic processes that govern bottom current dynamics and sediment supply. We illustrate these concepts based on the Pliocene−Quaternary channels and moats along the northern middle slope of the Gulf of Cádiz (along the southwestern Iberian Peninsula). There, the margin paleo-morphology, in particular the presence of canyons, affects the evolution of channels and moats due to short-term intermittency and variations of the Mediterranean Outflow Water. Our study offers new perspectives on contourite depositional systems; in particular, our understanding of channels and moats and their potential role in CO2 storage—impacting the twenty-first−century energy transition.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"29 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847130","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}
Lucas R. Tesser, Pierre Lanari, Jacob B. Forshaw, Thorsten A. Markmann, Mathias Hueck, Benita Putlitz, Noralinde de Leijer, Cauê R. Cioffi, Miguel A.S. Basei, Carlos E. Ganade
Garnet is widely thought to increase in stability and volume during prograde metamorphism and partial melting. Yet, whether early-formed subsolidus garnet persists or breaks down when melting begins remains an open question. Here, we integrate 3-D X-ray tomography with high-resolution major- and trace-element mapping of centrally sectioned garnets across a metapelitic metamorphic sequence to track their response from the subsolidus-suprasolidus transition to melting temperatures up to ∼770 °C. Contrary to experimental and phase equilibrium predictions, garnet undergoes extensive dissolution at the onset of partial melting, losing >40% of its volume. Melt percolation creates internal cavity networks within garnet, connecting crystal interiors to the reactive matrix, markedly shortening intracrystalline diffusion pathways at the melt-crystal interface. This process leads to the consumption of garnet and results in major- and trace-element redistribution at temperatures too low for intracrystalline diffusion in larger grains. Our findings reconcile the long-standing discrepancy between predicted progressive garnet growth above the solidus and the scarcity of melt inclusions in garnet rims in migmatites and granulites. As partial melting begins, subsolidus garnet reacts and becomes a permeable heavy rare earth elements and yttrium (HREE-Y) reservoir in the residual crust.
{"title":"Melting the myth: Prograde garnet dissolves during early crustal melting","authors":"Lucas R. Tesser, Pierre Lanari, Jacob B. Forshaw, Thorsten A. Markmann, Mathias Hueck, Benita Putlitz, Noralinde de Leijer, Cauê R. Cioffi, Miguel A.S. Basei, Carlos E. Ganade","doi":"10.1130/g54000.1","DOIUrl":"https://doi.org/10.1130/g54000.1","url":null,"abstract":"Garnet is widely thought to increase in stability and volume during prograde metamorphism and partial melting. Yet, whether early-formed subsolidus garnet persists or breaks down when melting begins remains an open question. Here, we integrate 3-D X-ray tomography with high-resolution major- and trace-element mapping of centrally sectioned garnets across a metapelitic metamorphic sequence to track their response from the subsolidus-suprasolidus transition to melting temperatures up to ∼770 °C. Contrary to experimental and phase equilibrium predictions, garnet undergoes extensive dissolution at the onset of partial melting, losing &gt;40% of its volume. Melt percolation creates internal cavity networks within garnet, connecting crystal interiors to the reactive matrix, markedly shortening intracrystalline diffusion pathways at the melt-crystal interface. This process leads to the consumption of garnet and results in major- and trace-element redistribution at temperatures too low for intracrystalline diffusion in larger grains. Our findings reconcile the long-standing discrepancy between predicted progressive garnet growth above the solidus and the scarcity of melt inclusions in garnet rims in migmatites and granulites. As partial melting begins, subsolidus garnet reacts and becomes a permeable heavy rare earth elements and yttrium (HREE-Y) reservoir in the residual crust.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"8 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847132","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}
Carbonatites are magmatic rocks that host most economic rare earth element (REE) deposits and bear on the deep Earth volatile cycle. Yet, the cumulative character of plutonic carbonatites and the rapid posteruptive alteration of volcanic carbonatites impede a direct determination of the melt compositions crystallizing these rocks. This study focused on sodium in carbonatite melts, a critical component for their genesis, magmatic evolution, and also for REE mobility, given that most carbonatite-hosted REE mineralizations are formed by alkali-rich fluids. Through experiments at subvolcanic conditions (100−200 MPa, 800−1000 °C), we determined the partition coefficient of Na between apatite and carbonatite melt, DNaapatite/carbonatite, which is rather uniformly 0.010 ± 0.003 at temperatures ≥800 °C. Applying our DNaapatite/carbonatite value to natural samples yields 8−22 wt% Na2O for the melts forming calcic carbonatites and 26−32 wt% Na2O for melts forming dolomite carbonatites. The latter are hence more evolved than calcic carbonatite melts, increasing their potential to shed alkali-rich fluids. A model accounting for calcite fractionation from calcite carbonatite melts prior to apatite saturation indicates primary Na2Omelt contents of 16−23 wt% at 900 °C and 9−11 wt% at 1100 °C, consistent with formation by liquid immiscibility from alkaline silicate magmas, but inconsistent with direct mantle derivation, in particular for dolomitic melts.
{"title":"Sodic nature of carbonatite melts and the origin of calcite versus dolomite carbonatites","authors":"Simone Marioni, Gino Sartori, Max W. Schmidt","doi":"10.1130/g53916.1","DOIUrl":"https://doi.org/10.1130/g53916.1","url":null,"abstract":"Carbonatites are magmatic rocks that host most economic rare earth element (REE) deposits and bear on the deep Earth volatile cycle. Yet, the cumulative character of plutonic carbonatites and the rapid posteruptive alteration of volcanic carbonatites impede a direct determination of the melt compositions crystallizing these rocks. This study focused on sodium in carbonatite melts, a critical component for their genesis, magmatic evolution, and also for REE mobility, given that most carbonatite-hosted REE mineralizations are formed by alkali-rich fluids. Through experiments at subvolcanic conditions (100−200 MPa, 800−1000 °C), we determined the partition coefficient of Na between apatite and carbonatite melt, DNaapatite/carbonatite, which is rather uniformly 0.010 ± 0.003 at temperatures ≥800 °C. Applying our DNaapatite/carbonatite value to natural samples yields 8−22 wt% Na2O for the melts forming calcic carbonatites and 26−32 wt% Na2O for melts forming dolomite carbonatites. The latter are hence more evolved than calcic carbonatite melts, increasing their potential to shed alkali-rich fluids. A model accounting for calcite fractionation from calcite carbonatite melts prior to apatite saturation indicates primary Na2Omelt contents of 16−23 wt% at 900 °C and 9−11 wt% at 1100 °C, consistent with formation by liquid immiscibility from alkaline silicate magmas, but inconsistent with direct mantle derivation, in particular for dolomitic melts.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"56 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145807416","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}
Luoqi Wang, Tianyi Li, Sensen Wu, Jie Yang, Yanhua Hu, Linshu Hu, Yijun Chen, YunZhao Ge, Yunfeng Chen, Can Rao, Zhenhong Du
The discovery and development of mineral resources are critical for sustaining modern energy demands. However, the geological processes that control mineralization are inherently complex, introducing considerable spatial variability that presents significant challenges for predictive modeling. While machine learning approaches have been increasingly applied to mineral prospectivity, many fail to explicitly incorporate key geological constraints, limiting their capacity to resolve the nonlinear and directionally dependent nature of mineralizing systems. Here we present a geologically constrained data-driven method that explicitly accounts for the spatial non-stationarity and anisotropy in ore-forming processes. In the benchmark case study from Canada, our method demonstrates a 7.4% improvement in recall performance compared with existing models. This robust performance is also observed in applications to the southern Cordillera region. Furthermore, the method elucidates regional ore-forming controls and quantifies spatial anisotropy in porphyry copper systems. Our findings demonstrate that incorporating geological constraints into data-driven models enhances both the accuracy and interpretability of mineral prospectivity assessments, offering a robust path forward in resource exploration.
{"title":"Geologically constrained data-driven modeling for mineral prospectivity mapping","authors":"Luoqi Wang, Tianyi Li, Sensen Wu, Jie Yang, Yanhua Hu, Linshu Hu, Yijun Chen, YunZhao Ge, Yunfeng Chen, Can Rao, Zhenhong Du","doi":"10.1130/g53947.1","DOIUrl":"https://doi.org/10.1130/g53947.1","url":null,"abstract":"The discovery and development of mineral resources are critical for sustaining modern energy demands. However, the geological processes that control mineralization are inherently complex, introducing considerable spatial variability that presents significant challenges for predictive modeling. While machine learning approaches have been increasingly applied to mineral prospectivity, many fail to explicitly incorporate key geological constraints, limiting their capacity to resolve the nonlinear and directionally dependent nature of mineralizing systems. Here we present a geologically constrained data-driven method that explicitly accounts for the spatial non-stationarity and anisotropy in ore-forming processes. In the benchmark case study from Canada, our method demonstrates a 7.4% improvement in recall performance compared with existing models. This robust performance is also observed in applications to the southern Cordillera region. Furthermore, the method elucidates regional ore-forming controls and quantifies spatial anisotropy in porphyry copper systems. Our findings demonstrate that incorporating geological constraints into data-driven models enhances both the accuracy and interpretability of mineral prospectivity assessments, offering a robust path forward in resource exploration.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"23 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145807827","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}
Eva E. Stüeken, Anthony R. Prave, Liam O’Connor, Jonas Kaempf, Anthony Clarke, Tim E. Johnson, Christopher L. Kirkland
Stromatolites are indicators of life on Earth since at least 3.5 Ga and possibly 3.7 Ga. From the mid-Archean onward, records of stromatolites display a range of morphologies and sizes, indicating that microorganisms were present in a variety of habitats. By comparison, the existing Paleoarchean stromatolite record is limited to small decimeter-scale domes, cones, and tufts that occur in evaporitic environments. Here, we document large domal stromatolites with ∼1.5 m width and 0.8 m height from a chert-jasper-carbonate member in the Paleoarchean (ca. 3.47 Ga) Mount Ada Basalt, Pilbara craton, Western Australia. Sedimentological features and trace-element chemistry show that the stromatolites grew on seafloor pillow basalts in an anoxic environment with hydrothermal influence. Aqueous alteration of basaltic-komatiitic crust likely supplied key nutrients, extending benthic microbial habitats into the deeper Paleoarchean ocean and supporting a thriving biosphere independent of continental exposure.
{"title":"Large domal stromatolites in the Paleoarchean ocean at 3.47 Ga","authors":"Eva E. Stüeken, Anthony R. Prave, Liam O’Connor, Jonas Kaempf, Anthony Clarke, Tim E. Johnson, Christopher L. Kirkland","doi":"10.1130/g53960.1","DOIUrl":"https://doi.org/10.1130/g53960.1","url":null,"abstract":"Stromatolites are indicators of life on Earth since at least 3.5 Ga and possibly 3.7 Ga. From the mid-Archean onward, records of stromatolites display a range of morphologies and sizes, indicating that microorganisms were present in a variety of habitats. By comparison, the existing Paleoarchean stromatolite record is limited to small decimeter-scale domes, cones, and tufts that occur in evaporitic environments. Here, we document large domal stromatolites with ∼1.5 m width and 0.8 m height from a chert-jasper-carbonate member in the Paleoarchean (ca. 3.47 Ga) Mount Ada Basalt, Pilbara craton, Western Australia. Sedimentological features and trace-element chemistry show that the stromatolites grew on seafloor pillow basalts in an anoxic environment with hydrothermal influence. Aqueous alteration of basaltic-komatiitic crust likely supplied key nutrients, extending benthic microbial habitats into the deeper Paleoarchean ocean and supporting a thriving biosphere independent of continental exposure.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"185 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145807826","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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