Pub Date : 2024-10-10DOI: 10.1016/j.epsl.2024.119055
Arthur Goodwin , Christian Schröder , Emily Bonsall , Russell J. Garwood , Romain Tartèse
The martian meteorite Northwest Africa (NWA) 11220 and paired stones (notably NWA 7034) are the only group of meteorites that sample a clastic near-surface lithology from Mars. The stones have been recognized as an impact-reworked lithology subjected to an impact-induced hydrothermal system — comparable to the postulated history of Jezero Crater, currently being explored by the NASA Perseverance rover. By applying Mössbauer spectroscopy in combination with several in situ analytical techniques including Raman spectroscopy, FTIR spectroscopy, and NanoSIMS, we show that aliphatic carbon compounds dominate the inventory of insoluble indigenous carbon compounds within NWA 11220. Disordered carbon — present in ∼5 μm heterogeneous masses — is preferentially found within porosity where it adjoins the mineral surface of titano-magnetite. This relationship suggests catalytic surfaces have enabled Fischer–Tropsch (FT) synthesis of hydrocarbons. Our in situ micron-scale analytical study indicates that such methods can help determine the origin of organic material that exists in the near-surface martian regolith. Such multimodal approaches will be a key methodology for searching for traces of past life in future samples returned from Mars.
{"title":"Abiotic origin of organics in the martian regolith","authors":"Arthur Goodwin , Christian Schröder , Emily Bonsall , Russell J. Garwood , Romain Tartèse","doi":"10.1016/j.epsl.2024.119055","DOIUrl":"10.1016/j.epsl.2024.119055","url":null,"abstract":"<div><div>The martian meteorite Northwest Africa (NWA) 11220 and paired stones (notably NWA 7034) are the only group of meteorites that sample a clastic near-surface lithology from Mars. The stones have been recognized as an impact-reworked lithology subjected to an impact-induced hydrothermal system — comparable to the postulated history of Jezero Crater, currently being explored by the NASA Perseverance rover. By applying Mössbauer spectroscopy in combination with several in situ analytical techniques including Raman spectroscopy, FTIR spectroscopy, and NanoSIMS, we show that aliphatic carbon compounds dominate the inventory of insoluble indigenous carbon compounds within NWA 11220. Disordered carbon — present in ∼5 μm heterogeneous masses — is preferentially found within porosity where it adjoins the mineral surface of titano-magnetite. This relationship suggests catalytic surfaces have enabled Fischer–Tropsch (FT) synthesis of hydrocarbons. Our in situ micron-scale analytical study indicates that such methods can help determine the origin of organic material that exists in the near-surface martian regolith. Such multimodal approaches will be a key methodology for searching for traces of past life in future samples returned from Mars.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119055"},"PeriodicalIF":4.8,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-10DOI: 10.1016/j.epsl.2024.119059
Zhen Tian , Jeffrey T. Freymueller , Yang He , Guofeng Ji , Shidi Wang , Zhenhong Li
GPS and InSAR observations of the first ∼1.5 years of postseismic deformation caused by the 2021 MW 7.4 Maduo earthquake provide a valuable opportunity to investigate fault interactions and regional rheological structure, as well as the future seismic potential around the Bayan Har block, northeastern Tibetan Plateau. We develop an integrated model to simulate the afterslip and viscoelastic relaxation contributions to the observed postseismic displacements, and found that afterslip driven by the coseismic stress is concentrated downdip of rupture, and dominates the postseismic deformation in the early stage (∼0.4 year after the event). Because afterslip decays quickly over time, viscoelastic relaxation should become the main postseismic mechanism as time goes on. The two mechanisms produce similar displacements during 0.4–1.5 years after the earthquake, but at 1.5 years after the earthquake the velocity caused by viscoelastic relaxation is larger than that caused by afterslip. Viscoelastic models assuming either a Burgers body or power-law rheology produce very similar predictions, with the Burgers body model having a slightly lower overall misfit. The rheological structure constrained by the postseismic observations supports the 35-km thick elastic upper crust overlying a Burgers body viscoelastic lower curst with a Maxwell viscosity of 3 × 1019 Pa s (5 - 50 × 1018 Pa s at 95% confidence), assuming the Kelvin viscosity is equal to 10% of that value. This is different from the regional rheology inferred by the postseismic investigations on the 2001 MW 7.8 Kokoxili and the 2008 MW 7.8 Wenchuan events, and the preferred thickness of the elastic crust is also different from that inferred from magnetotelluric profiles deployed in previous studies. We thus infer that the rheological structure within the Bayan Har block is possibly heterogeneous from west to east. Finally, the normal stress changes triggered by the coseismic rupture and postseismic process are estimated to be negative, but the shear stress changes to be positive on the western Kunlun fault, the eastern Dari fault and Bayan-Har Mountain fault. However, the current observations and studies are quite insufficient on those fault segments, therefore, we need to focus on their faulting behavior and seismic risk in the future.
{"title":"Postseismic deformation due to the 2021 MW 7.4 Maduo (China) earthquake and implications for regional rheology and seismic hazards around the Bayan Har block","authors":"Zhen Tian , Jeffrey T. Freymueller , Yang He , Guofeng Ji , Shidi Wang , Zhenhong Li","doi":"10.1016/j.epsl.2024.119059","DOIUrl":"10.1016/j.epsl.2024.119059","url":null,"abstract":"<div><div>GPS and InSAR observations of the first ∼1.5 years of postseismic deformation caused by the 2021 <em>M<sub>W</sub></em> 7.4 Maduo earthquake provide a valuable opportunity to investigate fault interactions and regional rheological structure, as well as the future seismic potential around the Bayan Har block, northeastern Tibetan Plateau. We develop an integrated model to simulate the afterslip and viscoelastic relaxation contributions to the observed postseismic displacements, and found that afterslip driven by the coseismic stress is concentrated downdip of rupture, and dominates the postseismic deformation in the early stage (∼0.4 year after the event). Because afterslip decays quickly over time, viscoelastic relaxation should become the main postseismic mechanism as time goes on. The two mechanisms produce similar displacements during 0.4–1.5 years after the earthquake, but at 1.5 years after the earthquake the velocity caused by viscoelastic relaxation is larger than that caused by afterslip. Viscoelastic models assuming either a Burgers body or power-law rheology produce very similar predictions, with the Burgers body model having a slightly lower overall misfit. The rheological structure constrained by the postseismic observations supports the 35-km thick elastic upper crust overlying a Burgers body viscoelastic lower curst with a Maxwell viscosity of 3 × 10<sup>19</sup> Pa s (5 - 50 × 10<sup>18</sup> Pa s at 95% confidence), assuming the Kelvin viscosity is equal to 10% of that value. This is different from the regional rheology inferred by the postseismic investigations on the 2001 <em>M<sub>W</sub></em> 7.8 Kokoxili and the 2008 <em>M<sub>W</sub></em> 7.8 Wenchuan events, and the preferred thickness of the elastic crust is also different from that inferred from magnetotelluric profiles deployed in previous studies. We thus infer that the rheological structure within the Bayan Har block is possibly heterogeneous from west to east. Finally, the normal stress changes triggered by the coseismic rupture and postseismic process are estimated to be negative, but the shear stress changes to be positive on the western Kunlun fault, the eastern Dari fault and Bayan-Har Mountain fault. However, the current observations and studies are quite insufficient on those fault segments, therefore, we need to focus on their faulting behavior and seismic risk in the future.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119059"},"PeriodicalIF":4.8,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419372","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}
Pub Date : 2024-10-09DOI: 10.1016/j.epsl.2024.119054
Vaishanavi Chauhan , Sanjay Kumar Mandal , Dirk Scherler , Manoj Kumar Jaiswal , Marcus Christl , Anil D. Shukla
Despite high rock uplift and surface runoff, most Himalayan river valleys feature tens of meters thick fill terraces, a legacy of aggradational episodes. Climate oscillations during the late Quaternary are commonly invoked to explain shifts from river incision to aggradation. While tectonic processes are known to cause transient aggradation, identifying their signatures and possible causes remains challenging. This study comprehensively analyzes ∼120-m thick valley-fill deposits exposed above the modern channel of the upper Beas River in the northwestern Indian Himalayan state of Himachal Pradesh. Luminescence dating of the valley fill reveals an aggradation period exceeding 100 kyr during the late Pleistocene, which likely commenced considerably earlier, based on an estimated >400-m thick fill buried beneath the present valley floor. The prolonged aggradation, encompassing several glacial-interglacial cycles, and the absence of systematic changes in Be-derived paleo-erosion rates or Sr/Sr and Nd/Nd isotope ratio-derived sediment provenance over time rule out late Quaternary climate oscillations as the sole driver of aggradation. Instead, we explain the longevity and extent of valley aggradation as the fluvial system's response to localized higher rock uplift rates downstream, as substantiated by the southern range flank morphology and the river network topology. We suggest that along-strike variations in thrust kinematics in this sector of the Himalaya likely caused the out-of-sequence lateral range growth and, consequently, triggered aggradation in the upstream valley. The implied temporal changes in stress and strain are critical for seismic hazard assessment.
{"title":"Prolonged sediment aggradation in an internal Himalayan valley due to out-of-sequence lateral fault growth","authors":"Vaishanavi Chauhan , Sanjay Kumar Mandal , Dirk Scherler , Manoj Kumar Jaiswal , Marcus Christl , Anil D. Shukla","doi":"10.1016/j.epsl.2024.119054","DOIUrl":"10.1016/j.epsl.2024.119054","url":null,"abstract":"<div><div>Despite high rock uplift and surface runoff, most Himalayan river valleys feature tens of meters thick fill terraces, a legacy of aggradational episodes. Climate oscillations during the late Quaternary are commonly invoked to explain shifts from river incision to aggradation. While tectonic processes are known to cause transient aggradation, identifying their signatures and possible causes remains challenging. This study comprehensively analyzes ∼120-m thick valley-fill deposits exposed above the modern channel of the upper Beas River in the northwestern Indian Himalayan state of Himachal Pradesh. Luminescence dating of the valley fill reveals an aggradation period exceeding 100 kyr during the late Pleistocene, which likely commenced considerably earlier, based on an estimated >400-m thick fill buried beneath the present valley floor. The prolonged aggradation, encompassing several glacial-interglacial cycles, and the absence of systematic changes in <figure><img></figure>Be-derived paleo-erosion rates or <figure><img></figure>Sr/<figure><img></figure>Sr and <figure><img></figure>Nd/<figure><img></figure>Nd isotope ratio-derived sediment provenance over time rule out late Quaternary climate oscillations as the sole driver of aggradation. Instead, we explain the longevity and extent of valley aggradation as the fluvial system's response to localized higher rock uplift rates downstream, as substantiated by the southern range flank morphology and the river network topology. We suggest that along-strike variations in thrust kinematics in this sector of the Himalaya likely caused the out-of-sequence lateral range growth and, consequently, triggered aggradation in the upstream valley. The implied temporal changes in stress and strain are critical for seismic hazard assessment.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119054"},"PeriodicalIF":4.8,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419377","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}
Pub Date : 2024-10-08DOI: 10.1016/j.epsl.2024.119058
Alexei V. Ivanov
It is frequently proposed that large bolide impacts and voluminous volcanic eruptions may be responsible for environmental catastrophes. In the conventional approach, the potential causes and consequences are matched using an age-versus-age plot, with preferential ages selected for comparison. This approach inevitably results in a one-to-one correlation, which may be misleading. To address this issue, a novel statistical metric, named conformity, has been proposed which accounts for the possibility of age coincidence resulting from random processes (i.e. bad luck coincidence). The available and updated geochronological datasets of bolide impacts, large igneous provinces, CO2-concentration peaks in the atmosphere, mass extinctions, ocean anoxic events, and climatic optima and thermal highs were subjected to a comparison in terms of their concordance. The most significant discovery is the correlation between the ages of mass extinctions and those of giant bolide impacts (crater diameter >40 km), as well as volcanism of continental large igneous provinces and CO2-concentration peaks in the atmosphere. The severity of mass extinctions appears to be dependent upon the number of simultaneously occurring causes. The most pronounced Late Maastrichtian (∼66 Ma) and Changhsingian (∼252 Ma) mass extinctions were likely caused by a combination of factors, including the simultaneous occurrence of volcanism of continental large igneous provinces, giant bolide impact and CO2-concentration rise in the atmosphere. Conversely, the ages of large igneous provinces, bolide impacts and CO2-concentration peaks are not correlated, indicating that these three causes were not interdependent.
经常有人提出，大型螺栓撞击和大量火山爆发可能是造成环境灾难的原因。在传统方法中，潜在的原因和后果是通过年龄与年龄对比图来匹配的，并选择优先年龄进行比较。这种方法不可避免地会产生一一对应的相关性，可能会产生误导。为了解决这个问题，我们提出了一种名为 "符合性 "的新统计指标，它考虑到了随机过程可能导致的年代巧合（即运气不佳的巧合）。我们对现有的和更新的有关螺栓撞击、大型火成岩带、大气中二氧化碳浓度峰值、大灭绝、海洋缺氧事件以及气候最适宜期和高温期的地质年代数据集进行了一致性比较。最重要的发现是大灭绝的年龄与巨型螺栓撞击（陨石坑直径为 40 公里）的年龄、大陆大型火成岩带的火山活动以及大气中二氧化碳浓度峰值之间的相关性。大灭绝的严重程度似乎取决于同时发生的原因的数量。最明显的马斯特里赫特晚期（66 Ma ∼66 Ma）和长兴期（252 Ma ∼252 Ma）大灭绝很可能是由多种因素共同造成的，包括同时发生的大陆大型火成岩带的火山活动、巨型螺栓撞击和大气中二氧化碳浓度的上升。相反，大火成岩带、巨栓撞击和二氧化碳浓度峰值的年龄并不相关，这表明这三个原因并不是相互依存的。
{"title":"Correlating 300 million years of catastrophes","authors":"Alexei V. Ivanov","doi":"10.1016/j.epsl.2024.119058","DOIUrl":"10.1016/j.epsl.2024.119058","url":null,"abstract":"<div><div>It is frequently proposed that large bolide impacts and voluminous volcanic eruptions may be responsible for environmental catastrophes. In the conventional approach, the potential causes and consequences are matched using an age-versus-age plot, with preferential ages selected for comparison. This approach inevitably results in a one-to-one correlation, which may be misleading. To address this issue, a novel statistical metric, named conformity, has been proposed which accounts for the possibility of age coincidence resulting from random processes (i.e. bad luck coincidence). The available and updated geochronological datasets of bolide impacts, large igneous provinces, CO<sub>2</sub>-concentration peaks in the atmosphere, mass extinctions, ocean anoxic events, and climatic optima and thermal highs were subjected to a comparison in terms of their concordance. The most significant discovery is the correlation between the ages of mass extinctions and those of giant bolide impacts (crater diameter >40 km), as well as volcanism of continental large igneous provinces and CO<sub>2</sub>-concentration peaks in the atmosphere. The severity of mass extinctions appears to be dependent upon the number of simultaneously occurring causes. The most pronounced Late Maastrichtian (∼66 Ma) and Changhsingian (∼252 Ma) mass extinctions were likely caused by a combination of factors, including the simultaneous occurrence of volcanism of continental large igneous provinces, giant bolide impact and CO<sub>2</sub>-concentration rise in the atmosphere. Conversely, the ages of large igneous provinces, bolide impacts and CO<sub>2</sub>-concentration peaks are not correlated, indicating that these three causes were not interdependent.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119058"},"PeriodicalIF":4.8,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142420035","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}
Pub Date : 2024-10-08DOI: 10.1016/j.epsl.2024.119017
Irina M. Artemieva
Ocean age-dependent cooling subsidence with seafloor deepening is traditionally described by models of thermo-chemical buoyancy of oceanic plates with globally constant parameters, that specify a linear correlation between square-root of seafloor age, sqrt(age), and bathymetry. Here I present a worldwide analysis of the ocean floor split into 94 segments, delineated by wide-offset transform faults and mid-ocean ridges, to demonstrate a strong heterogeneity of sediment-corrected isostatic cooling subsidence both between and within normal oceans. Anomalous oceans are identified from bathymetry deviation from age-dependent predictions during data processing. Subsidence parameters for individual ocean segments significantly deviate from global constants in conventional models and show a large variability of subsidence rate (270–535 m/Ma1/2) and zero-age depth (−1.30 to −3.03 km) with plate thickness estimated between 50 and 160 km for cooling models with constant mantle properties.
Statistically strong correlations (R2=0.80–0.94) between major characteristics of cooling subsidence and spreading rate indicate that ocean evolution is essentially controlled by spreading rate, despite this factor is not included in conventional models of ocean subsidence. Normal oceans with slower spreading rate have, statistically, higher subsidence rate which implies faster gravitational collapse caused by faster plate cooling with moderate-to-low mantle temperatures at mid-ocean ridges. Fast-spreading oceans have the opposite characteristics. The ultraslow SW Indian and the fast-spreading Central Pacific Oceans are the end-members in ocean cooling subsidence trends, with the Atlantic/NW Indian Oceans tending towards the ultraslow end, and the Pacific/SE Indian Oceans being closer to the fast-spreading end. The Arctic Ocean and the Atlantics north of the Charlie-Gibbs Fracture Zone with an atypical subsidence behavior often deviate from the global trends. Strong correlation between spreading rate, ocean half-width and the type of ocean margins implies that ridge-push dominates tectonic forces in slower-spreading, narrower oceans with passive margins, while slab-pull at active margins is a dominant tectonic force in faster-spreading oceans with half-width exceeding 4250 km.
The age of bathymetry departure from cooling subsidence, controlled by distribution of hotspots on ocean floor, correlates (R2=0.76) with spreading rate, and thus is not fully random. Slower-spreading oceans follow normal cooling subsidence to older ages (7.5–9.5 Ma1/2) than faster-spreading oceans (5–7 Ma1/2). Recognition that spreading rate controls ocean evolution with formation of active or passive ocean margins dominated by slab-pull or ridge-push contributes to advances in understanding driving forces in geodynamics.
{"title":"Heterogeneous cooling subsidence of oceanic lithosphere controlled by spreading rate","authors":"Irina M. Artemieva","doi":"10.1016/j.epsl.2024.119017","DOIUrl":"10.1016/j.epsl.2024.119017","url":null,"abstract":"<div><div>Ocean age-dependent cooling subsidence with seafloor deepening is traditionally described by models of thermo-chemical buoyancy of oceanic plates with globally constant parameters, that specify a linear correlation between square-root of seafloor age, sqrt(age), and bathymetry. Here I present a worldwide analysis of the ocean floor split into 94 segments, delineated by wide-offset transform faults and mid-ocean ridges, to demonstrate a strong heterogeneity of sediment-corrected isostatic cooling subsidence both between and within normal oceans. Anomalous oceans are identified from bathymetry deviation from age-dependent predictions during data processing. Subsidence parameters for individual ocean segments significantly deviate from global constants in conventional models and show a large variability of subsidence rate (270–535 m/Ma<sup>1/2</sup>) and zero-age depth (−1.30 to −3.03 km) with plate thickness estimated between 50 and 160 km for cooling models with constant mantle properties.</div><div>Statistically strong correlations (R<sup>2</sup>=0.80–0.94) between major characteristics of cooling subsidence and spreading rate indicate that ocean evolution is essentially controlled by spreading rate, despite this factor is not included in conventional models of ocean subsidence. Normal oceans with slower spreading rate have, statistically, higher subsidence rate which implies faster gravitational collapse caused by faster plate cooling with moderate-to-low mantle temperatures at mid-ocean ridges. Fast-spreading oceans have the opposite characteristics. The ultraslow SW Indian and the fast-spreading Central Pacific Oceans are the end-members in ocean cooling subsidence trends, with the Atlantic/NW Indian Oceans tending towards the ultraslow end, and the Pacific/SE Indian Oceans being closer to the fast-spreading end. The Arctic Ocean and the Atlantics north of the Charlie-Gibbs Fracture Zone with an atypical subsidence behavior often deviate from the global trends. Strong correlation between spreading rate, ocean half-width and the type of ocean margins implies that ridge-push dominates tectonic forces in slower-spreading, narrower oceans with passive margins, while slab-pull at active margins is a dominant tectonic force in faster-spreading oceans with half-width exceeding 4250 km.</div><div>The age of bathymetry departure from cooling subsidence, controlled by distribution of hotspots on ocean floor, correlates (R<sup>2</sup>=0.76) with spreading rate, and thus is not fully random. Slower-spreading oceans follow normal cooling subsidence to older ages (7.5–9.5 Ma<sup>1/2</sup>) than faster-spreading oceans (5–7 Ma<sup>1/2</sup>). Recognition that spreading rate controls ocean evolution with formation of active or passive ocean margins dominated by slab-pull or ridge-push contributes to advances in understanding driving forces in geodynamics.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119017"},"PeriodicalIF":4.8,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-08DOI: 10.1016/j.epsl.2024.119057
Jian Wang , Zhi Wang , Xiugen Fu , Xuan-Ce Wang , Simon A. Wilde , Yi Fu , Jian Lin , Hengye Wei , Lijun Shen , Gang Rao , Ahmed Mansour
The Tibetan Plateau plays a crucial role in both Asian and global geomorphology and climate dynamics. However, the precise mechanisms through which its deep geodynamic processes influence surface systems have remained elusive. Here, we present a novel model that can be used to evaluate these processes, employing a comprehensive approach that incorporates multistage bilateral subduction, lithospheric breakoff, and subsequent foundering based on a combined analysis of global tomography, volcanic rock ages, and geochemical isotopes. By analyzing seismic tomography data derived from extensive seismic arrays recording over 18 million multi-phase arrival times, we have constrained the locations and morphology of remnant slabs associated with the subduction of the Neo-Tethyan Ocean, Greater Indian plate, and Asian lithosphere. Our findings reveal a striking correlation between discrete episodic surface volcanism and plate uplift at distinct intervals: 56–44 Ma, 44–28 Ma, 28–18 Ma, and 18–0 Ma within the Tibetan Plateau. These intervals correspond to four stages of stepwise lithospheric subduction. Paired slab-like anomalies observed during the second and third steps suggest simultaneous detachment of subducting lithosphere from opposing directions. Building upon this observation, we propose a two-sided breakoff model. This model posits that bilateral subduction and lithospheric gravitational subsidence have induced extensive volcanism and episodic uplift within the Tibetan Plateau. The subsidence, resulting from both past and ongoing lithospheric break-offs of the Indian and Asian plates, has triggered widespread volcanism that likely exerts a significant impact on climate patterns. Our study establishes a systematic framework linking deep lithospheric processes with surface phenomena in Tibet, providing valuable insights into the dynamic interactions shaping the region's geological and climatic evolution.
{"title":"Control of stepwise subduction and slab breakoff on volcanism and uplift in the Tibetan Plateau","authors":"Jian Wang , Zhi Wang , Xiugen Fu , Xuan-Ce Wang , Simon A. Wilde , Yi Fu , Jian Lin , Hengye Wei , Lijun Shen , Gang Rao , Ahmed Mansour","doi":"10.1016/j.epsl.2024.119057","DOIUrl":"10.1016/j.epsl.2024.119057","url":null,"abstract":"<div><div>The Tibetan Plateau plays a crucial role in both Asian and global geomorphology and climate dynamics. However, the precise mechanisms through which its deep geodynamic processes influence surface systems have remained elusive. Here, we present a novel model that can be used to evaluate these processes, employing a comprehensive approach that incorporates multistage bilateral subduction, lithospheric breakoff, and subsequent foundering based on a combined analysis of global tomography, volcanic rock ages, and geochemical isotopes. By analyzing seismic tomography data derived from extensive seismic arrays recording over 18 million multi-phase arrival times, we have constrained the locations and morphology of remnant slabs associated with the subduction of the Neo-Tethyan Ocean, Greater Indian plate, and Asian lithosphere. Our findings reveal a striking correlation between discrete episodic surface volcanism and plate uplift at distinct intervals: 56–44 Ma, 44–28 Ma, 28–18 Ma, and 18–0 Ma within the Tibetan Plateau. These intervals correspond to four stages of stepwise lithospheric subduction. Paired slab-like anomalies observed during the second and third steps suggest simultaneous detachment of subducting lithosphere from opposing directions. Building upon this observation, we propose a two-sided breakoff model. This model posits that bilateral subduction and lithospheric gravitational subsidence have induced extensive volcanism and episodic uplift within the Tibetan Plateau. The subsidence, resulting from both past and ongoing lithospheric break-offs of the Indian and Asian plates, has triggered widespread volcanism that likely exerts a significant impact on climate patterns. Our study establishes a systematic framework linking deep lithospheric processes with surface phenomena in Tibet, providing valuable insights into the dynamic interactions shaping the region's geological and climatic evolution.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119057"},"PeriodicalIF":4.8,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419323","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-07DOI: 10.1016/j.epsl.2024.119025
Ke Lin , Tao Han , Kyle Morgan , Paul S. Kench , Yue-Gau Chen , Xianfeng Wang
Sea surface temperature (SST) across the tropical Indian Ocean is warming at a significantly higher rate than other tropical oceans over the past two decades. However, the cause of the abnormal warming remains unclear due to the short duration of instrumental observations as well as sparse long-term paleoclimate proxy records (e.g., from corals) within this region. Before coral-based records can be compiled to infer long-term environmental change in the region, an assessment of the suitability and robustness of the various coral archive types for evaluating warming must be made. Here, we present a 40-year coral stable oxygen isotopic ratio (δ18O) record derived from both dome-shaped (i.e., massive) and microatoll corals (Porites sp.) from the southern Maldives, located in the equatorial Indian Ocean. We found a consistent δ18O reproducibility in both dome-shaped and microatoll corals, demonstrating the viability of utilising a range of coral morphotypes for reconstructing long-term ocean conditions and climate change. Statistical analysis indicates that our coral δ18O values are primarily influenced by SST rather than sea surface salinity (SSS). Notably, the δ18O record exhibits a stepwise shift, with average δ18O values of -4.93 ‰ and -5.01 ‰ for the periods 1978–1999 and 2000–2019, respectively. This shift in δ18O corresponds with the increase in regional SST, despite its relatively small magnitude of approximately 0.3 °C. Furthermore, the negative shift in δ18O values after 2000 coincides with the transition to La Niña-like conditions and the negative Interdecadal Pacific Oscillation (IPO) phase in the tropical Pacific Ocean. Under these conditions, the geostrophic transport of the Indonesian Throughflow (ITF) was enhanced, which likely contributed to warming in the tropical Indian Ocean by bringing in more warm water from the Pacific. Therefore, the consistent shifts between our Maldives coral δ18O anomalies and instrumental SST anomalies support the argument that an intensified ITF may have contributed to the abnormal warming in the tropical Indian Ocean over the past two decades. Our findings suggest that microatoll corals in well-flushed open ocean environments can provide robust climatic proxy data comparable to dome-shaped corals. By compiling these records, we show the primary impact of SST on coral δ18O values in the tropical Indian Ocean, evidenced by a notable shift closely aligned with regional SST fluctuations around 2000.
{"title":"Tracing the stepwise warming trend in the tropical Indian Ocean through a 40-year record of oxygen isotope composition in Maldives corals","authors":"Ke Lin , Tao Han , Kyle Morgan , Paul S. Kench , Yue-Gau Chen , Xianfeng Wang","doi":"10.1016/j.epsl.2024.119025","DOIUrl":"10.1016/j.epsl.2024.119025","url":null,"abstract":"<div><div>Sea surface temperature (SST) across the tropical Indian Ocean is warming at a significantly higher rate than other tropical oceans over the past two decades. However, the cause of the abnormal warming remains unclear due to the short duration of instrumental observations as well as sparse long-term paleoclimate proxy records (e.g., from corals) within this region. Before coral-based records can be compiled to infer long-term environmental change in the region, an assessment of the suitability and robustness of the various coral archive types for evaluating warming must be made. Here, we present a 40-year coral stable oxygen isotopic ratio (δ<sup>18</sup>O) record derived from both dome-shaped (i.e., massive) and microatoll corals (<em>Porites</em> sp.) from the southern Maldives, located in the equatorial Indian Ocean. We found a consistent δ<sup>18</sup>O reproducibility in both dome-shaped and microatoll corals, demonstrating the viability of utilising a range of coral morphotypes for reconstructing long-term ocean conditions and climate change. Statistical analysis indicates that our coral δ<sup>18</sup>O values are primarily influenced by SST rather than sea surface salinity (SSS). Notably, the δ<sup>18</sup>O record exhibits a stepwise shift, with average δ<sup>18</sup>O values of -4.93 ‰ and -5.01 ‰ for the periods 1978–1999 and 2000–2019, respectively. This shift in δ<sup>18</sup>O corresponds with the increase in regional SST, despite its relatively small magnitude of approximately 0.3 °C. Furthermore, the negative shift in δ<sup>18</sup>O values after 2000 coincides with the transition to La Niña-like conditions and the negative Interdecadal Pacific Oscillation (IPO) phase in the tropical Pacific Ocean. Under these conditions, the geostrophic transport of the Indonesian Throughflow (ITF) was enhanced, which likely contributed to warming in the tropical Indian Ocean by bringing in more warm water from the Pacific. Therefore, the consistent shifts between our Maldives coral δ<sup>18</sup>O anomalies and instrumental SST anomalies support the argument that an intensified ITF may have contributed to the abnormal warming in the tropical Indian Ocean over the past two decades. Our findings suggest that microatoll corals in well-flushed open ocean environments can provide robust climatic proxy data comparable to dome-shaped corals. By compiling these records, we show the primary impact of SST on coral δ<sup>18</sup>O values in the tropical Indian Ocean, evidenced by a notable shift closely aligned with regional SST fluctuations around 2000.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119025"},"PeriodicalIF":4.8,"publicationDate":"2024-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419376","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}
Pub Date : 2024-10-07DOI: 10.1016/j.epsl.2024.119056
Xinyi Zhou , Yizhi Sheng , Yanning Zheng , Mingyue Jiang , Mengmei Wang , Zihua Zhu , Gaoyuan Li , Oliver Baars , Hailiang Dong
Biological nitrogen fixation, which converts atmospheric dinitrogen to ammonia, is catalyzed mostly by Mo-nitrogenase and is a primary contributor to bioavailable nitrogen on early Earth. Mo-nitrogenase is believed to have evolved during the Archean, despite the extremely low concentration of dissolved Mo. However, it remains unclear whether Mo minerals could serve as a source of Mo to support the prevalence of Mo-nitrogenase on early Earth. Here we investigated the bioavailability of molybdenite by incubating it with a metabolically ancient anoxygenic phototroph (Rhodopseudomonas palustris) under anoxic conditions. In the laboratory, R. palustris utilized molybdenum from molybdenite as a cofactor for nitrogen fixation. This bacterium extracted Mo from molybdenite by secreting molybdophores rhodopetrobactin A and B and by expressing Mo transport proteins. Surface-sensitive techniques demonstrated significant changes in surface chemistry of molybdenite after its interaction with cells. These findings provide novel explanations for the prevalence of Mo-nitrogenase on early Earth, with significant implications for nitrogen fixation in modern Mo-deficient environments.
生物固氮将大气中的二氮转化为氨，主要是由钼-氮化酶催化的，是早期地球上生物可用氮的主要来源。尽管溶解态钼的浓度极低，但钼-氮酶被认为是在阿基坦时期进化而来的。然而，目前仍不清楚钼矿物是否可以作为支持早期地球上钼-氮化酶盛行的钼来源。在这里，我们通过在缺氧条件下将辉钼矿与一种新陈代谢古老的缺氧光营养体（Rhodopseudomonas palustris）一起培养，研究了辉钼矿的生物利用率。在实验室中，R. palustris 利用辉钼矿中的钼作为固氮的辅助因子。这种细菌通过分泌钼藻类 rhodopetrobactin A 和 B 以及表达钼转运蛋白，从辉钼矿中提取钼。表面敏感技术表明，辉钼矿与细胞相互作用后，其表面化学成分发生了显著变化。这些发现为早期地球上钼氮酶的普遍存在提供了新的解释，对现代缺钼环境中的固氮作用具有重要意义。
{"title":"Bioavailability of molybdenite to support nitrogen fixation on early Earth by an anoxygenic phototroph","authors":"Xinyi Zhou , Yizhi Sheng , Yanning Zheng , Mingyue Jiang , Mengmei Wang , Zihua Zhu , Gaoyuan Li , Oliver Baars , Hailiang Dong","doi":"10.1016/j.epsl.2024.119056","DOIUrl":"10.1016/j.epsl.2024.119056","url":null,"abstract":"<div><div>Biological nitrogen fixation, which converts atmospheric dinitrogen to ammonia, is catalyzed mostly by Mo-nitrogenase and is a primary contributor to bioavailable nitrogen on early Earth. Mo-nitrogenase is believed to have evolved during the Archean, despite the extremely low concentration of dissolved Mo. However, it remains unclear whether Mo minerals could serve as a source of Mo to support the prevalence of Mo-nitrogenase on early Earth. Here we investigated the bioavailability of molybdenite by incubating it with a metabolically ancient anoxygenic phototroph (<em>Rhodopseudomonas palustris</em>) under anoxic conditions. In the laboratory, <em>R. palustris</em> utilized molybdenum from molybdenite as a cofactor for nitrogen fixation. This bacterium extracted Mo from molybdenite by secreting molybdophores rhodopetrobactin A and B and by expressing Mo transport proteins. Surface-sensitive techniques demonstrated significant changes in surface chemistry of molybdenite after its interaction with cells. These findings provide novel explanations for the prevalence of Mo-nitrogenase on early Earth, with significant implications for nitrogen fixation in modern Mo-deficient environments.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119056"},"PeriodicalIF":4.8,"publicationDate":"2024-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419381","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}
Pub Date : 2024-10-05DOI: 10.1016/j.epsl.2024.119053
Maria Paula Castellanos-Melendez , John Dilles , Marcel Guillong , Olivier Bachmann , Cyril Chelle-Michou
<div><div>The current race towards greener energy and its intertwined increase in Cu demand imposes the need to find mineralized centers that are economic despite greater depths. To this end, a better understanding of the processes controlling the metal tonnage of porphyry Cu deposits, the main source of Cu, is needed and the focus of current research and debate. This study provides a comprehensive view of the duration of upper-crustal magmatism and its significance in the degree of metal endowment in porphyry Cu deposits using the Yerington batholith, Nevada, USA, as a case study. The Yerington district constitutes an exceptional example of an exposed porphyry Cu system where the plutonic environment that fed the porphyritic dikes is accessible. Combining trace element geochemistry and high-precision geochronology of zircon from all exposed units, we propose that the thermal maturation of the upper crust by a continuum in magmatic activity without significant hiatuses is a key factor in enabling the formation of large porphyry Cu style mineralization. The Yerington magmatic system transitioned from a volcanically active environment with coeval plutonism to a growing upper-crustal magmatic reservoir that fed the porphyritic dikes and associated mineralized centers to then resume its volcanic activity terminating the ore-forming episode. A relatively high volcanic/plutonic ratio characterized the first expressions of Jurassic magmatism in the district from ∼170 Ma with the coeval eruption of the Artesia Lake volcanics and the protracted emplacement of the McLeod Hill pluton. Geochemically, this period recorded distinctive negative Eu anomalies and a gentle increase in Yb/Dy ratios in zircon with decreasing Ti contents over a large range of zircon crystallization temperatures. This persistent magmatism over ∼2 Myr thermally matured the upper crust, enabling the growth of magmatic reservoirs that formed the Bear and Luhr Hill plutons without known volcanic activity for ∼1.3 Myr. Zircon trace element compositions indicate that this transition occurred as a continuum in decreasing negative Eu anomalies and increasing Yb/Dy with decreasing Ti contents and age across the plutonic units, reaching the more evolved signatures and lowest crystallization temperatures in the zircon from porphyry dikes. An increase in the volcanic/plutonic ratio with the eruption of the Fulstone Spring sequence likely terminated the ore-forming potential of the district. Although many other studies have provided important views on the timing and duration of porphyry Cu deposit formation, the link to their plutonic roots has been limited due to their inaccessibility. Therefore, this study offers the first complete picture into the temporal and chemical evolution of an upper-crustal magmatic system and the roles that factors like prolonged magmatism and volcanism play before and after ore formation. We argue that without the thermal maturation of the upper crust, the constructio
当前的绿色能源竞赛与铜需求的增加相互交织，这就要求我们必须找到尽管深度更大但仍具有经济价值的矿化中心。为此，需要更好地了解控制斑岩铜矿床（铜的主要来源）金属吨位的过程，这也是当前研究和讨论的重点。本研究以美国内华达州耶灵顿岩床为案例，全面探讨了上部岩壳岩浆作用的持续时间及其对斑岩型铜矿床金属禀赋程度的影响。耶林顿地区是斑岩铜矿系统出露的一个特殊例子，在这里可以看到斑岩岩脉的成岩环境。结合所有出露单元的痕量元素地球化学和高精度锆石地质年代学，我们提出，岩浆活动的连续性和无明显间断的上地壳热成熟是形成大型斑岩型铜矿化的关键因素。耶灵顿岩浆系统从火山活动环境与共生深成岩活动过渡到不断增长的上地壳岩浆储层，该储层为斑岩岩钉和相关矿化中心提供了能量，然后又恢复了火山活动，终止了矿石形成过程。该地区侏罗纪岩浆活动的最初表现形式是火山/岩浆比率相对较高，从 170 Ma 开始，阿特西亚湖火山岩同时喷发，McLeod Hill 长岩浆岩长期喷发。从地球化学角度看，这一时期的锆石在很大的锆石结晶温度范围内出现了明显的负Eu异常和Yb/Dy比值的平缓上升，同时Ti含量不断下降。这种持续了2 Myr以上的岩浆活动使上地壳热成熟，使岩浆储层得以增长，形成了Bear和Luhr Hill岩浆柱，在1.3 Myr以上的时间里没有已知的火山活动。锆石痕量元素组成表明，这种转变是一个连续的过程，随着Ti含量和年龄的降低，负Eu异常不断降低，Yb/Dy不断增加，在斑岩岩峰的锆石中达到了更先进的特征和最低的结晶温度。随着富尔斯通泉序列的喷发，火山/岩浆岩比率的增加很可能终止了该地区的成矿潜力。尽管许多其他研究对斑岩型铜矿床形成的时间和持续时间提出了重要观点，但由于无法进入这些矿床，因此与其板岩根源的联系一直很有限。因此，本研究首次完整地揭示了上地壳岩浆系统的时间和化学演变，以及延长岩浆活动和火山活动等因素在矿石形成前后所起的作用。我们认为，如果没有上地壳的热成熟，就不可能形成长寿岩浆储层，也就不可能形成斑岩型铜矿床。在此前提下，不仅与矿石有关的岩浆活动持续时间，而且长寿命前生岩浆活动的发生也可能对矿床的最终吨位起着至关重要的控制作用，因此在勘探新斑岩矿床时应加以考虑。
{"title":"From birth to death: The role of upper-crustal thermal maturation and volcanism in porphyry ore formation revealed in the Yerington district","authors":"Maria Paula Castellanos-Melendez , John Dilles , Marcel Guillong , Olivier Bachmann , Cyril Chelle-Michou","doi":"10.1016/j.epsl.2024.119053","DOIUrl":"10.1016/j.epsl.2024.119053","url":null,"abstract":"<div><div>The current race towards greener energy and its intertwined increase in Cu demand imposes the need to find mineralized centers that are economic despite greater depths. To this end, a better understanding of the processes controlling the metal tonnage of porphyry Cu deposits, the main source of Cu, is needed and the focus of current research and debate. This study provides a comprehensive view of the duration of upper-crustal magmatism and its significance in the degree of metal endowment in porphyry Cu deposits using the Yerington batholith, Nevada, USA, as a case study. The Yerington district constitutes an exceptional example of an exposed porphyry Cu system where the plutonic environment that fed the porphyritic dikes is accessible. Combining trace element geochemistry and high-precision geochronology of zircon from all exposed units, we propose that the thermal maturation of the upper crust by a continuum in magmatic activity without significant hiatuses is a key factor in enabling the formation of large porphyry Cu style mineralization. The Yerington magmatic system transitioned from a volcanically active environment with coeval plutonism to a growing upper-crustal magmatic reservoir that fed the porphyritic dikes and associated mineralized centers to then resume its volcanic activity terminating the ore-forming episode. A relatively high volcanic/plutonic ratio characterized the first expressions of Jurassic magmatism in the district from ∼170 Ma with the coeval eruption of the Artesia Lake volcanics and the protracted emplacement of the McLeod Hill pluton. Geochemically, this period recorded distinctive negative Eu anomalies and a gentle increase in Yb/Dy ratios in zircon with decreasing Ti contents over a large range of zircon crystallization temperatures. This persistent magmatism over ∼2 Myr thermally matured the upper crust, enabling the growth of magmatic reservoirs that formed the Bear and Luhr Hill plutons without known volcanic activity for ∼1.3 Myr. Zircon trace element compositions indicate that this transition occurred as a continuum in decreasing negative Eu anomalies and increasing Yb/Dy with decreasing Ti contents and age across the plutonic units, reaching the more evolved signatures and lowest crystallization temperatures in the zircon from porphyry dikes. An increase in the volcanic/plutonic ratio with the eruption of the Fulstone Spring sequence likely terminated the ore-forming potential of the district. Although many other studies have provided important views on the timing and duration of porphyry Cu deposit formation, the link to their plutonic roots has been limited due to their inaccessibility. Therefore, this study offers the first complete picture into the temporal and chemical evolution of an upper-crustal magmatic system and the roles that factors like prolonged magmatism and volcanism play before and after ore formation. We argue that without the thermal maturation of the upper crust, the constructio","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119053"},"PeriodicalIF":4.8,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-05DOI: 10.1016/j.epsl.2024.119051
V.B. Garcia , J. O'Neil , E.L. Dantas , C.T. Augustin
Evidence for Hadean depleted mantle reservoir(s) is well-established by mantle-derived rocks from multiple Archean complexes showing excesses in 142Nd compared to the modern mantle. Yet, the existence of an early enriched mantle source, which should have concomitantly formed during these Hadean silicate differentiation event(s), has only been recently confirmed by well-resolved 142Nd deficits measured in Paleoarchean mafic amphibolites from the São José do Campestre massif of the Borborema Province, NE Brazil. To investigate the nature and extent of this early-formed enriched reservoir, a series of samples from the Seridó belt, NE Brazil, have been investigated for their geochemical and coupled 147,146Sm-143,142Nd isotopic compositions, focusing on the Paleoarchean São Tomé layered intrusion. The São Tomé intrusion is composed of layers of metamorphosed mafic and ultramafic rocks with whole-rock trace element compositions and high olivine crystal Ni contents consistent with an incompatible trace element enriched pyroxenitic mantle source. Most analyzed samples from the Seridó belt yielded negative µ142Nd, as low as ∼ -20 (representing the lowest 142Nd/144Nd ratio ever measured in terrestrial rocks), with an average µ142Nd for the São Tomé intrusion of -9.6 ± 1.4. The São Tomé samples interpreted as the least isotopically disturbed yielded an 147Sm-143Nd isochron age of 3551 ± 368 Ma, consistent with previous zircon U-Pb ages, with an initial ε143Nd = -1.7 ± 1.2. Coupling the long-lived 147Sm-143Nd and the short-lived 146Sm-142Nd systems for the São Tomé rocks suggests a Hadean enriched mantle source formed at ∼4.44 Ga with a 147Sm/144Nd of ∼0.18, which may be complementary to the early depleted mantle recorded by Eoarchean rocks from the North Atlantic Craton, possibly formed during magma ocean crystallization. These results also imply that the record of this Hadean enriched mantle source is not restricted to the São José do Campestre massif but extends to a larger portion of the Borborema Province.
与现代地幔相比，来自多个Archean复合体的地幔源岩石显示出过量的142Nd，这充分证明了Hadean贫化地幔储层的存在。然而，巴西东北部博博雷马省 São José do Campestre 地块的古新世黑云母闪长岩中测量到的 142Nd 缺陷，最近才证实存在一个早期富集地幔源，该地幔源应该是在这些黑云母硅酸盐分异过程中同时形成的。为了研究这种早期形成的富集储层的性质和范围，我们对巴西东北部塞里多带的一系列样品进行了地球化学和 147、146Sm-143、142Nd 同位素组合的研究，重点是古新世的圣多美层状侵入体。圣多美侵入体由变质的黑云母岩和超黑云母岩层组成，整个岩石的微量元素组成和橄榄石晶体的高镍含量与不相容的微量元素富集辉石地幔源一致。来自塞里多带的大多数分析样本的µ142Nd为负值，低至∼ -20（代表了在陆地岩石中测得的最低142Nd/144Nd比率），圣多美侵入体的平均µ142Nd为-9.6 ± 1.4。被解释为同位素扰动最小的圣多美样本的 147Sm-143Nd 等时年龄为 3551 ± 368 Ma，与之前的锆石 U-Pb 年龄一致，初始ε143Nd = -1.7 ± 1.2。将圣多美岩石的长寿命147Sm-143Nd和短寿命146Sm-142Nd系统耦合起来，表明哈代富集地幔源形成于∼4.44 Ga，147Sm/144Nd为∼0.18，这可能是对北大西洋克拉通的始新世岩石记录的早期贫化地幔的补充，可能是在岩浆洋结晶过程中形成的。这些结果还意味着，这种哈代富集地幔源的记录并不局限于São José do Campestre地块，而是延伸到了Borborema省的更大范围。
{"title":"Composition and age constraints on a Hadean enriched mantle source revealed by the Paleoarchean São Tomé layered intrusion, NE Brazil","authors":"V.B. Garcia , J. O'Neil , E.L. Dantas , C.T. Augustin","doi":"10.1016/j.epsl.2024.119051","DOIUrl":"10.1016/j.epsl.2024.119051","url":null,"abstract":"<div><div>Evidence for Hadean depleted mantle reservoir(s) is well-established by mantle-derived rocks from multiple Archean complexes showing excesses in <sup>142</sup>Nd compared to the modern mantle. Yet, the existence of an early enriched mantle source, which should have concomitantly formed during these Hadean silicate differentiation event(s), has only been recently confirmed by well-resolved <sup>142</sup>Nd deficits measured in Paleoarchean mafic amphibolites from the São José do Campestre massif of the Borborema Province, NE Brazil. To investigate the nature and extent of this early-formed enriched reservoir, a series of samples from the Seridó belt, NE Brazil, have been investigated for their geochemical and coupled <sup>147,146</sup>Sm-<sup>143,142</sup>Nd isotopic compositions, focusing on the Paleoarchean São Tomé layered intrusion. The São Tomé intrusion is composed of layers of metamorphosed mafic and ultramafic rocks with whole-rock trace element compositions and high olivine crystal Ni contents consistent with an incompatible trace element enriched pyroxenitic mantle source. Most analyzed samples from the Seridó belt yielded negative µ<sup>142</sup>Nd, as low as ∼ -20 (representing the lowest <sup>142</sup>Nd/<sup>144</sup>Nd ratio ever measured in terrestrial rocks), with an average µ<sup>142</sup>Nd for the São Tomé intrusion of -9.6 ± 1.4. The São Tomé samples interpreted as the least isotopically disturbed yielded an <sup>147</sup>Sm-<sup>143</sup>Nd isochron age of 3551 ± 368 Ma, consistent with previous zircon U-Pb ages, with an initial ε<sup>143</sup>Nd = -1.7 ± 1.2. Coupling the long-lived <sup>147</sup>Sm-<sup>143</sup>Nd and the short-lived <sup>146</sup>Sm-<sup>142</sup>Nd systems for the São Tomé rocks suggests a Hadean enriched mantle source formed at ∼4.44 Ga with a <sup>147</sup>Sm/<sup>144</sup>Nd of ∼0.18, which may be complementary to the early depleted mantle recorded by Eoarchean rocks from the North Atlantic Craton, possibly formed during magma ocean crystallization. These results also imply that the record of this Hadean enriched mantle source is not restricted to the São José do Campestre massif but extends to a larger portion of the Borborema Province.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119051"},"PeriodicalIF":4.8,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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