Pub Date : 2025-02-01DOI: 10.1016/j.epsl.2024.119174
Jie Chen , Javier Escartin , Mathilde Cannat
Fault scarps at Mid-Ocean Ridges (MOR) are recognizable on the seafloor, and often measured to estimate the tectonic component of plate divergence. This estimate, based on linear fault scarp parameters, is referred to here as apparent tectonic strain (ATS). However, ATS may differ from the actual tectonic strain at a lithosphere scale. This is clear at detachment faults at magma-poor slow-ultraslow spreading ridges that do not correspond to linear scarps yet accommodate very high strain. Here we study fault scarps in young volcanic MOR seafloor, using high-resolution (1–2 m) bathymetry data of 8 sites with spreading rates of 14–110 km/Ma. Our results show a weak correlation between ATS and factors such as spreading rate, melt flux, or thermal regime, challenging the use of ATS as a proxy for the MOR tectonic component of plate divergence. Instead, ATS is time-dependent and heterogeneous spatially, controlled by the frequency and size of dike intrusions with associated faults and volcanic eruptions that resurface the seafloor and cover faults. Our findings also have implications for estimates of tectonic extension in subaerial volcanic rifting systems that undergo similar processes.
{"title":"Fault scarps and tectonic strain in young volcanic seafloor","authors":"Jie Chen , Javier Escartin , Mathilde Cannat","doi":"10.1016/j.epsl.2024.119174","DOIUrl":"10.1016/j.epsl.2024.119174","url":null,"abstract":"<div><div>Fault scarps at Mid-Ocean Ridges (MOR) are recognizable on the seafloor, and often measured to estimate the tectonic component of plate divergence. This estimate, based on linear fault scarp parameters, is referred to here as apparent tectonic strain (ATS). However, ATS may differ from the actual tectonic strain at a lithosphere scale. This is clear at detachment faults at magma-poor slow-ultraslow spreading ridges that do not correspond to linear scarps yet accommodate very high strain. Here we study fault scarps in young volcanic MOR seafloor, using high-resolution (1–2 m) bathymetry data of 8 sites with spreading rates of 14–110 km/Ma. Our results show a weak correlation between ATS and factors such as spreading rate, melt flux, or thermal regime, challenging the use of ATS as a proxy for the MOR tectonic component of plate divergence. Instead, ATS is time-dependent and heterogeneous spatially, controlled by the frequency and size of dike intrusions with associated faults and volcanic eruptions that resurface the seafloor and cover faults. Our findings also have implications for estimates of tectonic extension in subaerial volcanic rifting systems that undergo similar processes.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119174"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158121","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 : 2025-02-01DOI: 10.1016/j.epsl.2024.119170
Saadi Chabane, Lorenzo Paulatto, Daniele Antonangeli, Paola Giura
Thermal conductivity of minerals composing planetary mantles plays a fundamental role in controlling the heat propagation and hence the dynamic history of a planet. Here we present ab-initio calculations of the lattice dynamics and thermal conductivity of MgO as a function of temperature and pressure, accounting for phonon scattering and the renormalization it induces. Our calculations, validated by measurements of phonon energies and linewidths, point to a complex interplay between pressure-induced and temperature-induced effects, which influences the predominance of 3- or 4-phonon contributions, the former leading to a reduction in energies, the latter to an increase. Thus, not only the relative magnitude but also the sign of the anharmonic corrections depends strongly on the planetary geotherms. Our study shows that calculations taking into account only 3-phonon scattering underestimate thermal conductivity by 20–45% under the conditions of the Earth's lower mantle, while including anharmonic renormalization up to fourth order provides results in good agreement with high-pressure, high-temperature experiments. The predominance of 3-phonon interactions at core-mantle boundary (CMB) conditions significantly reduces phonon energies, leading to a thermal conductivity of 50.7 Wm-1K-1, further reduced by extrinsic effects, including isotopic disorder, oxygen vacancies and iron inclusion. In particular, oxygen vacancies of up to 1% decrease the thermal conductivity of MgO at CMB conditions by ∼40%, an effect that adds to that of Fe/Mg replacement. Our results indicate that mass disorder effectively reduces thermal conductivity of lower mantle minerals, contributing to the thermal blanketing that limits the heat flux from the core.
{"title":"Pressure- and temperature-dependent anharmonicity of MgO: Implications for the thermal conductivity of planetary mantles","authors":"Saadi Chabane, Lorenzo Paulatto, Daniele Antonangeli, Paola Giura","doi":"10.1016/j.epsl.2024.119170","DOIUrl":"10.1016/j.epsl.2024.119170","url":null,"abstract":"<div><div>Thermal conductivity of minerals composing planetary mantles plays a fundamental role in controlling the heat propagation and hence the dynamic history of a planet. Here we present <em>ab-initio</em> calculations of the lattice dynamics and thermal conductivity of MgO as a function of temperature and pressure, accounting for phonon scattering and the renormalization it induces. Our calculations, validated by measurements of phonon energies and linewidths, point to a complex interplay between pressure-induced and temperature-induced effects, which influences the predominance of 3- or 4-phonon contributions, the former leading to a reduction in energies, the latter to an increase. Thus, not only the relative magnitude but also the sign of the anharmonic corrections depends strongly on the planetary geotherms. Our study shows that calculations taking into account only 3-phonon scattering underestimate thermal conductivity by 20–45% under the conditions of the Earth's lower mantle, while including anharmonic renormalization up to fourth order provides results in good agreement with high-pressure, high-temperature experiments. The predominance of 3-phonon interactions at core-mantle boundary (CMB) conditions significantly reduces phonon energies, leading to a thermal conductivity of 50.7 Wm<sup>-1</sup>K<sup>-1</sup>, further reduced by extrinsic effects, including isotopic disorder, oxygen vacancies and iron inclusion. In particular, oxygen vacancies of up to 1% decrease the thermal conductivity of MgO at CMB conditions by ∼40%, an effect that adds to that of Fe/Mg replacement. Our results indicate that mass disorder effectively reduces thermal conductivity of lower mantle minerals, contributing to the thermal blanketing that limits the heat flux from the core.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119170"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158929","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 : 2025-02-01DOI: 10.1016/j.epsl.2024.119164
Amy G. Ryan , Lars N. Hansen , Amanda Dillman , Mattia Pistone , Mark E. Zimmerman , Stewart A. Williams
We present the results of high-temperature (900 °C), high-pressure (200 MPa) deformation experiments that identify the processes and deformation conditions leading to melt migration in crystal-rich mushes. This study is relevant to transport of magmas in transcrustal magma reservoirs. Experimental samples comprise juxtaposed pieces of soda-lime glass and densified mixtures of borosilicate glass and quartz sand, which, at elevated temperatures and pressures, have melt and shear viscosities similar to natural silicate melts and crystal-rich mushes. The synthetic mushes have crystal fractions of 0.60 to 0.83. Samples were deformed in torsion at shear strain rates of 10–5 to 10–4 s-1 to shear strains up to 2.7. Image analysis of experimental samples shows melt migrates into the mush during shear. In mushes with crystal fractions ≥ 0.75 shearing causes melt-filled mm-scale dikes to form and propagate into the mush. To our knowledge, these features are the first dikes formed in high-temperature, high-pressure deformation experiments. Dike formation results from shear-induced dilation, which causes the mush to become underpressurized relative to the melt, at an estimated pressure differential of 10 MPa. Experimental conditions indicate shear-induced dilation and diking occur while the mush is still viscous (i.e., Weissenberg number < 10–2). We apply our results to Soufrière Hills Volcano (Montserrat, West Indies) and use our analysis to predict the deformation conditions that would lead to diking and rapid, voluminous melt migration in that active volcanic system.
{"title":"Shear-induced dilation and dike formation during mush deformation","authors":"Amy G. Ryan , Lars N. Hansen , Amanda Dillman , Mattia Pistone , Mark E. Zimmerman , Stewart A. Williams","doi":"10.1016/j.epsl.2024.119164","DOIUrl":"10.1016/j.epsl.2024.119164","url":null,"abstract":"<div><div>We present the results of high-temperature (900 °C), high-pressure (200 MPa) deformation experiments that identify the processes and deformation conditions leading to melt migration in crystal-rich mushes. This study is relevant to transport of magmas in transcrustal magma reservoirs. Experimental samples comprise juxtaposed pieces of soda-lime glass and densified mixtures of borosilicate glass and quartz sand, which, at elevated temperatures and pressures, have melt and shear viscosities similar to natural silicate melts and crystal-rich mushes. The synthetic mushes have crystal fractions of 0.60 to 0.83. Samples were deformed in torsion at shear strain rates of 10<sup>–5</sup> to 10<sup>–4</sup> s<sup>-1</sup> to shear strains up to 2.7. Image analysis of experimental samples shows melt migrates into the mush during shear. In mushes with crystal fractions ≥ 0.75 shearing causes melt-filled mm-scale dikes to form and propagate into the mush. To our knowledge, these features are the first dikes formed in high-temperature, high-pressure deformation experiments. Dike formation results from shear-induced dilation, which causes the mush to become underpressurized relative to the melt, at an estimated pressure differential of 10 MPa. Experimental conditions indicate shear-induced dilation and diking occur while the mush is still viscous (i.e., Weissenberg number < 10<sup>–2</sup>). We apply our results to Soufrière Hills Volcano (Montserrat, West Indies) and use our analysis to predict the deformation conditions that would lead to diking and rapid, voluminous melt migration in that active volcanic system.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119164"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158146","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 : 2025-02-01DOI: 10.1016/j.epsl.2024.119171
Charis M. Horn, Philip Skemer
The relatively low strength of the hydrous minerals has been theorized to play a role in the initiation of subduction through the feedbacks between faulting, hydration reactions, and rheological weakening. To further explore the behaviour of hydrous magnesium silicate minerals under the high stress conditions relevant to propagating faults, we performed nanoindentation tests on three serpentine species—lizardite, antigorite, and chrysotile—from room temperature up to their respective dehydration temperatures. While all serpentine minerals exhibit markedly lower indentation hardness than olivine under the same conditions (Hol = 13.1–14.9 GPa), we find that antigorite (Hatg = 5.7–6.7 GPa) is almost a factor of three harder than lizardite (Hliz = 2.2–2.6 GPa), which is itself an order of magnitude harder than chrysotile (Hctl = 0.1 GPa). We also indented chlorite from room temperature up to 400 °C and found that it has a hardness between that of lizardite and antigorite (Hchl = 2.8–4.0 GPa). Chrysotile is even weaker than the mineral talc (Htlc = 0.6 GPa), another hydrous magnesium silicate, which was tested in a previous study. The weakest hydrous magnesium silicates – talc and chrysotile – are approximately one order of magnitude weaker than antigorite and almost two orders of magnitude weaker than olivine. There is a systematic relationship between indentation hardness and the lattice spacing between c-planes in these sheet silicates. Geodynamic models of subduction initiation typically use an ad hoc finite yield stress to trigger localized deformation. This study confirms that hydrous magnesium silicates are a likely candidate for alteration products that can facilitate localized deformation both before and after subduction initiation. However, the degree of weakening is highly dependent on the specific reaction product.
{"title":"Rheology of hydrous minerals in the subduction multisystem","authors":"Charis M. Horn, Philip Skemer","doi":"10.1016/j.epsl.2024.119171","DOIUrl":"10.1016/j.epsl.2024.119171","url":null,"abstract":"<div><div>The relatively low strength of the hydrous minerals has been theorized to play a role in the initiation of subduction through the feedbacks between faulting, hydration reactions, and rheological weakening. To further explore the behaviour of hydrous magnesium silicate minerals under the high stress conditions relevant to propagating faults, we performed nanoindentation tests on three serpentine species—lizardite, antigorite, and chrysotile—from room temperature up to their respective dehydration temperatures. While all serpentine minerals exhibit markedly lower indentation hardness than olivine under the same conditions (H<sub>ol</sub> = 13.1–14.9 GPa), we find that antigorite (H<sub>atg</sub> = 5.7–6.7 GPa) is almost a factor of three harder than lizardite (H<sub>liz</sub> = 2.2–2.6 GPa), which is itself an order of magnitude harder than chrysotile (H<sub>ctl</sub> = 0.1 GPa). We also indented chlorite from room temperature up to 400 °C and found that it has a hardness between that of lizardite and antigorite (H<sub>chl</sub> = 2.8–4.0 GPa). Chrysotile is even weaker than the mineral talc (H<sub>tlc</sub> = 0.6 GPa), another hydrous magnesium silicate, which was tested in a previous study. The weakest hydrous magnesium silicates – talc and chrysotile – are approximately one order of magnitude weaker than antigorite and almost two orders of magnitude weaker than olivine. There is a systematic relationship between indentation hardness and the lattice spacing between c-planes in these sheet silicates. Geodynamic models of subduction initiation typically use an ad hoc finite yield stress to trigger localized deformation. This study confirms that hydrous magnesium silicates are a likely candidate for alteration products that can facilitate localized deformation both before and after subduction initiation. However, the degree of weakening is highly dependent on the specific reaction product.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119171"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143157735","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 : 2025-02-01DOI: 10.1016/j.epsl.2024.119155
Cin-Ty Lee , Duncan Keller , Rajdeep Dasgupta , Kirsten Siebach , Patrick McGovern , Jackson Borchardt , Julin Zhang
The thermal state of planetary crusts depends primarily on heat flow from the mantle to the crust and the depth-integrated radioactive heat generation in the crust. The latter scales with crustal thickness, such that for a given concentration of heat-producing elements, the thicker the crust, the hotter it will be. If estimates of Martian crustal thickness are correct and if these thicknesses are representative of the Noachian crust, thermal modeling shows that the thick crust underlying the southern highlands should have been hot enough 4–3 billion years ago to produce widespread partial melting in the lower crust, whereas the thinner crust beneath the northern lowlands would not have been hot enough to melt. Widespread melting of the lower crust in the southern highlands should have generated significant amounts of silicic magmas, such as granites, as direct partial melts or by fractional crystallization of such melts. Silicic plutons are thus predicted to lie at depth beneath the southern highlands, now hidden beneath a carapace of younger basaltic flows. High surface heat flux imparted by the thick southern highlands crust would also have reduced the extent of permafrost, generating an underlying, stable aquifer of liquid water in the Martian regolith during the Noachian. Tapping of this aquifer by volcanoes or impacts may have caused episodic flooding on an otherwise frozen planet.
{"title":"Crustal thickness effects on chemical differentiation and hydrology on Mars","authors":"Cin-Ty Lee , Duncan Keller , Rajdeep Dasgupta , Kirsten Siebach , Patrick McGovern , Jackson Borchardt , Julin Zhang","doi":"10.1016/j.epsl.2024.119155","DOIUrl":"10.1016/j.epsl.2024.119155","url":null,"abstract":"<div><div>The thermal state of planetary crusts depends primarily on heat flow from the mantle to the crust and the depth-integrated radioactive heat generation in the crust. The latter scales with crustal thickness, such that for a given concentration of heat-producing elements, the thicker the crust, the hotter it will be. If estimates of Martian crustal thickness are correct and if these thicknesses are representative of the Noachian crust, thermal modeling shows that the thick crust underlying the southern highlands should have been hot enough 4–3 billion years ago to produce widespread partial melting in the lower crust, whereas the thinner crust beneath the northern lowlands would not have been hot enough to melt. Widespread melting of the lower crust in the southern highlands should have generated significant amounts of silicic magmas, such as granites, as direct partial melts or by fractional crystallization of such melts. Silicic plutons are thus predicted to lie at depth beneath the southern highlands, now hidden beneath a carapace of younger basaltic flows. High surface heat flux imparted by the thick southern highlands crust would also have reduced the extent of permafrost, generating an underlying, stable aquifer of liquid water in the Martian regolith during the Noachian. Tapping of this aquifer by volcanoes or impacts may have caused episodic flooding on an otherwise frozen planet.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119155"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158122","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 : 2025-02-01DOI: 10.1016/j.epsl.2024.119166
Elmar Albers , Alexander Diehl , Jessica N. Fitzsimmons , Laramie T. Jensen , Frieder Klein , Jill M. McDermott , Autun Purser , Jeffrey S. Seewald , Maren Walter , Gunter Wegener , Wolfgang Bach , Antje Boetius , Christopher R. German
The nature of deep-sea hydrothermal systems is commonly inferred from physicochemical plume characteristics and seafloor observations, as was the case for the ‘Polaris’ site on the ultraslow-spreading Gakkel Ridge, Earth's northernmost hydrothermal system. Initial reports showing temperature and turbidity anomalies in its hydrothermal plume combined with its location on a neovolcanic axial seamount suggested a volcanically-hosted ‘black smoker’-type system. That interpretation, however, is inconsistent with our more complete data set derived from extensive water column sampling and seafloor surveys. The buoyant plume exhibits minor turbidity anomalies and low metal concentrations (dissolved Mn ≤ 3.1 nM), but contains substantial concentrations of H2 (275 nM) and 13C-enriched CH4 (365 nM, δ13C = –13.2). Instead of a ‘black smoker’ vent field, we observed small-scale chimney structures at the seafloor. Together, these data imply intermediate-temperature reaction of hydrothermal fluids with ultramafic rock in the subseafloor before discharge through pillow basalt outcrops at the seafloor. Our study challenges the ability of established approaches to vent exploration, reliant exclusively on in situ sensing to reveal the full geodiversity of subseafloor hydrothermal venting. Ultramafic-influenced systems, releasing H2 and CH4 into the ocean, may be a recurring feature along the entire 25% of the global ridge system that is ultraslow-spreading.
{"title":"Ultramafic-influenced submarine venting on basaltic seafloor at the Polaris site, 87°N, Gakkel Ridge","authors":"Elmar Albers , Alexander Diehl , Jessica N. Fitzsimmons , Laramie T. Jensen , Frieder Klein , Jill M. McDermott , Autun Purser , Jeffrey S. Seewald , Maren Walter , Gunter Wegener , Wolfgang Bach , Antje Boetius , Christopher R. German","doi":"10.1016/j.epsl.2024.119166","DOIUrl":"10.1016/j.epsl.2024.119166","url":null,"abstract":"<div><div>The nature of deep-sea hydrothermal systems is commonly inferred from physicochemical plume characteristics and seafloor observations, as was the case for the ‘Polaris’ site on the ultraslow-spreading Gakkel Ridge, Earth's northernmost hydrothermal system. Initial reports showing temperature and turbidity anomalies in its hydrothermal plume combined with its location on a neovolcanic axial seamount suggested a volcanically-hosted ‘black smoker’-type system. That interpretation, however, is inconsistent with our more complete data set derived from extensive water column sampling and seafloor surveys. The buoyant plume exhibits minor turbidity anomalies and low metal concentrations (dissolved Mn ≤ 3.1 nM), but contains substantial concentrations of H<sub>2</sub> (275 nM) and <sup>13</sup>C-enriched CH<sub>4</sub> (365 nM, δ<sup>13</sup>C = –13.2). Instead of a ‘black smoker’ vent field, we observed small-scale chimney structures at the seafloor. Together, these data imply intermediate-temperature reaction of hydrothermal fluids with ultramafic rock in the subseafloor before discharge through pillow basalt outcrops at the seafloor. Our study challenges the ability of established approaches to vent exploration, reliant exclusively on in situ sensing to reveal the full geodiversity of subseafloor hydrothermal venting. Ultramafic-influenced systems, releasing H<sub>2</sub> and CH<sub>4</sub> into the ocean, may be a recurring feature along the entire 25% of the global ridge system that is ultraslow-spreading.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119166"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158149","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 : 2025-02-01DOI: 10.1016/j.epsl.2024.119163
G. Madeira , L. Esteves , S. Charnoz , E. Lega , F. Moynier
Modeling the isotopic and elemental abundance of the bulk silicate Moon represent major challenges. Similarities in the non-mass dependent isotopic composition of refractory elements with the bulk silicate Earth suggest that both the Earth and the Moon formed from the same material reservoir. On the other hand, the Moon's volatile depletion and isotopic composition of moderately volatile elements points to a global devolatilization processes, most likely during a magma ocean phase of the Moon. Here, we investigate the devolatilization of the molten Moon due to a tidally-assisted hydrodynamic escape, first proposed by Charnoz et al. (2021), with a focus on the dynamics of the evaporated gas. Unlike the 1D steady-state approach of Charnoz et al. (2021), we use 2D time-dependent hydrodynamic simulations carried out with the FARGOCA code modified to take into account the magma ocean as a gas source. Near the Earth's Roche limit, where the proto-Moon likely formed, evaporated gases from the lunar magma ocean form a circum-Earth disk of volatiles, with less than 30% of material being re-accreted by the Moon. We find that the measured depletion of K and Na on the Moon can be achieved if the lunar magma-ocean had a surface temperature of about 1800-2000 K. After about 1000 years, a thermal boundary layer or a flotation crust forms a lid that inhibits volatile escape. Mapping the volatile velocity field reveals varying trends in the longitudes of volatile reaccretion on the Moon's surface: material is predominantly re-accreted on the trailing side when the Moon-Earth distance exceeds 3.5 Earth radii. For values of 0.0003 and 0.03, 60% and more than 99% of the volatile material, respectively, is re-accreted on the trailing side, suggesting a dichotomy in volatile abundances between the leading and trailing sides of the Moon. This dichotomy may provide insights on the tidal conditions of the early molten Earth. In conclusion, tidally-driven atmospheric escape effectively devolatilizes the Moon, matching the measured abundances of Na and K on timescales compatible with the formation of a thermal boundary layer or an anorthite flotation crust.
{"title":"Hydrodynamical simulations of proto-Moon degassing","authors":"G. Madeira , L. Esteves , S. Charnoz , E. Lega , F. Moynier","doi":"10.1016/j.epsl.2024.119163","DOIUrl":"10.1016/j.epsl.2024.119163","url":null,"abstract":"<div><div>Modeling the isotopic and elemental abundance of the bulk silicate Moon represent major challenges. Similarities in the non-mass dependent isotopic composition of refractory elements with the bulk silicate Earth suggest that both the Earth and the Moon formed from the same material reservoir. On the other hand, the Moon's volatile depletion and isotopic composition of moderately volatile elements points to a global devolatilization processes, most likely during a magma ocean phase of the Moon. Here, we investigate the devolatilization of the molten Moon due to a tidally-assisted hydrodynamic escape, first proposed by <span><span>Charnoz et al. (2021)</span></span>, with a focus on the dynamics of the evaporated gas. Unlike the 1D steady-state approach of <span><span>Charnoz et al. (2021)</span></span>, we use 2D time-dependent hydrodynamic simulations carried out with the <span>FARGOCA</span> code modified to take into account the magma ocean as a gas source. Near the Earth's Roche limit, where the proto-Moon likely formed, evaporated gases from the lunar magma ocean form a circum-Earth disk of volatiles, with less than 30% of material being re-accreted by the Moon. We find that the measured depletion of K and Na on the Moon can be achieved if the lunar magma-ocean had a surface temperature of about 1800-2000 K. After about 1000 years, a thermal boundary layer or a flotation crust forms a lid that inhibits volatile escape. Mapping the volatile velocity field reveals varying trends in the longitudes of volatile reaccretion on the Moon's surface: material is predominantly re-accreted on the trailing side when the Moon-Earth distance exceeds 3.5 Earth radii. For <span><math><msub><mrow><mi>k</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>/</mo><mi>Q</mi></math></span> values of 0.0003 and 0.03, 60% and more than 99% of the volatile material, respectively, is re-accreted on the trailing side, suggesting a dichotomy in volatile abundances between the leading and trailing sides of the Moon. This dichotomy may provide insights on the tidal conditions of the early molten Earth. In conclusion, tidally-driven atmospheric escape effectively devolatilizes the Moon, matching the measured abundances of Na and K on timescales compatible with the formation of a thermal boundary layer or an anorthite flotation crust.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119163"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143157733","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 : 2025-02-01DOI: 10.1016/j.epsl.2024.119176
Siyang Zhou , Youxue Zhang , Noriko T. Kita
We report the first study of titanium (Ti) isotope fractionation during diffusion in Fe-free basaltic melts using diffusion couple experiments. Ti is a high-field strength element with low diffusivity similar to Si. Understanding Ti isotope diffusion could provide insight into the behavior of other low-diffusivity elements in magmatic processes. For this study, we selected two experimental charges with the largest initial contrast in TiO2 concentrations from previous diffusion couple experiments. We measured the 49Ti/47Ti isotope ratio profiles in these experiments using Secondary Ion Mass Spectrometry (SIMS). Our results show that SIMS measurements using Cameca IMS-1280 can achieve a precision of 0.05 ‰ to 0.1 ‰ (1SD internal error) for δ49Ti at ∼3 wt% TiO2 using multi-collector Faraday cup and electron multiplier (EM). However, the precision drops to 0.5‰ at 0.03 wt% TiO2 using the EM. For an initial Ti concentration contrast of about 180 in a diffusion couple, the total variation in δ49Ti across the diffusion couple profile is about 3.0 ‰. Diffusivities of different Ti isotopes are related by D49/D47 = (m47/m47)β, where D47 and D49 are the diffusivities of 47Ti and 49Ti, m47 and m49 are their atomic masses, and β is an empirical parameter characterizing diffusive isotope fractionation. By fitting the isotope ratio profiles, we determined a β value of 0.0318 ± 0.0021 (1SD error) for the TiO2-−MgO interdiffusion couple at 1500 °C, and values of 0.019 to 0.031 for the SiO2-TiO2 interdiffusion couple. Hence, total Ti isotope ratio variation greater than 1‰ could be generated along a diffusion profile when the initial TiO2 concentration contrast exceeds 15. Such high concentration contrast may be realized for basalt-rhyolite or basalt-komatiite magma mixing. This study expands the database of diffusion parameters for non-traditional isotopes and offers new insight into Ti isotope fractionation during magmatic process, with potential to further understand magma and rock evolution. For example, we schematically modeled Ti concentration and isotopes in Horoman peridotite massif, and were able to explain most observed data.
{"title":"Diffusive titanium isotope fractionation in silicate melts","authors":"Siyang Zhou , Youxue Zhang , Noriko T. Kita","doi":"10.1016/j.epsl.2024.119176","DOIUrl":"10.1016/j.epsl.2024.119176","url":null,"abstract":"<div><div>We report the first study of titanium (Ti) isotope fractionation during diffusion in Fe-free basaltic melts using diffusion couple experiments. Ti is a high-field strength element with low diffusivity similar to Si. Understanding Ti isotope diffusion could provide insight into the behavior of other low-diffusivity elements in magmatic processes. For this study, we selected two experimental charges with the largest initial contrast in TiO<sub>2</sub> concentrations from previous diffusion couple experiments. We measured the <sup>49</sup>Ti/<sup>47</sup>Ti isotope ratio profiles in these experiments using Secondary Ion Mass Spectrometry (SIMS). Our results show that SIMS measurements using Cameca IMS-1280 can achieve a precision of 0.05 ‰ to 0.1 ‰ (1SD internal error) for δ<sup>49</sup>Ti at ∼3 wt% TiO<sub>2</sub> using multi-collector Faraday cup and electron multiplier (EM). However, the precision drops to 0.5‰ at 0.03 wt% TiO<sub>2</sub> using the EM. For an initial Ti concentration contrast of about 180 in a diffusion couple, the total variation in δ<sup>49</sup>Ti across the diffusion couple profile is about 3.0 ‰. Diffusivities of different Ti isotopes are related by <em>D</em><sub>49</sub>/<em>D</em><sub>47</sub> = (<em>m</em><sub>47</sub>/<em>m</em><sub>47</sub>)<sup>β</sup>, where <em>D</em><sub>47</sub> and <em>D</em><sub>49</sub> are the diffusivities of <sup>47</sup>Ti and <sup>49</sup>Ti, <em>m</em><sub>47</sub> and <em>m</em><sub>49</sub> are their atomic masses, and β is an empirical parameter characterizing diffusive isotope fractionation. By fitting the isotope ratio profiles, we determined a β value of 0.0318 ± 0.0021 (1SD error) for the TiO<sub>2</sub>-<sub>−</sub>MgO interdiffusion couple at 1500 °C, and values of 0.019 to 0.031 for the SiO<sub>2</sub>-TiO<sub>2</sub> interdiffusion couple. Hence, total Ti isotope ratio variation greater than 1‰ could be generated along a diffusion profile when the initial TiO<sub>2</sub> concentration contrast exceeds 15. Such high concentration contrast may be realized for basalt-rhyolite or basalt-komatiite magma mixing. This study expands the database of diffusion parameters for non-traditional isotopes and offers new insight into Ti isotope fractionation during magmatic process, with potential to further understand magma and rock evolution. For example, we schematically modeled Ti concentration and isotopes in Horoman peridotite massif, and were able to explain most observed data.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119176"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158150","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 : 2025-02-01DOI: 10.1016/j.epsl.2024.119173
Min Liu , Yen Joe Tan , Hao Guo , Hongyi Li , Renqi Lu , Jinzhong Jiang
The foreshocks preceding the 2021 Mw 6.1 Yangbi earthquake are one of the better-monitored complex foreshock sequences, however, the underlying physical processes and controlling factors are still in debate. In this study, we determine precise foreshock hypocenters, high-resolution earthquake source region velocity structure, and 3-D fault geometry for the 2021 Yangbi sequence by leveraging seismic data from 19 local stations. Our results suggest that natural fluid diffusion is likely a driver of the Yangbi foreshock sequence based on three lines of evidence: 1) regions with low Vs and relatively high Vp/Vs are widespread within the fault system; 2) earliest foreshocks exhibit diffusion-like migration front, and 3) foreshock evolution coincides with typical fault valving behavior, where the rupture of an Mw 4.6 foreshock broke a barrier of fluid flow. Besides, our results reveal that the fault system consists of three secondary fault zones (SFZ1-3) connected by a compressive stepover zone. SFZ1-2 and SFZ3 exhibit predominantly right-lateral strike-slip and normal faulting components, respectively. The extensional environment of SFZ3 may serve as the main channel for deep fluid upwelling into the stepover zone. The compressive stepover zone forms a region with high fluid pressure, facilitating further fluid diffusion into SFZ1-2, which can explain the earliest foreshock evolution that started in the stepover zone before migrating into SFZ1. Therefore, our observations also illuminate how 3-D fault geometry controls fluid diffusion within the fault system, which may further combine with stress triggering and possible aseismic slip to result in the complex 2021 Yangbi foreshock sequence.
{"title":"Fluids and fault structures underlying the complex foreshock sequence of the 2021 Mw 6.1 Yangbi earthquake","authors":"Min Liu , Yen Joe Tan , Hao Guo , Hongyi Li , Renqi Lu , Jinzhong Jiang","doi":"10.1016/j.epsl.2024.119173","DOIUrl":"10.1016/j.epsl.2024.119173","url":null,"abstract":"<div><div>The foreshocks preceding the 2021 Mw 6.1 Yangbi earthquake are one of the better-monitored complex foreshock sequences, however, the underlying physical processes and controlling factors are still in debate. In this study, we determine precise foreshock hypocenters, high-resolution earthquake source region velocity structure, and 3-D fault geometry for the 2021 Yangbi sequence by leveraging seismic data from 19 local stations. Our results suggest that natural fluid diffusion is likely a driver of the Yangbi foreshock sequence based on three lines of evidence: 1) regions with low Vs and relatively high Vp/Vs are widespread within the fault system; 2) earliest foreshocks exhibit diffusion-like migration front, and 3) foreshock evolution coincides with typical fault valving behavior, where the rupture of an Mw 4.6 foreshock broke a barrier of fluid flow. Besides, our results reveal that the fault system consists of three secondary fault zones (SFZ1-3) connected by a compressive stepover zone. SFZ1-2 and SFZ3 exhibit predominantly right-lateral strike-slip and normal faulting components, respectively. The extensional environment of SFZ3 may serve as the main channel for deep fluid upwelling into the stepover zone. The compressive stepover zone forms a region with high fluid pressure, facilitating further fluid diffusion into SFZ1-2, which can explain the earliest foreshock evolution that started in the stepover zone before migrating into SFZ1. Therefore, our observations also illuminate how 3-D fault geometry controls fluid diffusion within the fault system, which may further combine with stress triggering and possible aseismic slip to result in the complex 2021 Yangbi foreshock sequence.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119173"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143158151","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 : 2025-02-01DOI: 10.1016/j.epsl.2024.119175
Eduardo Contreras-Reyes , Matías Carvajal , Felipe González
Accurate and precise 3-D geometry models of subduction zone plate boundaries are crucial for advancing earthquake science, enhancing hazard assessments, and improving our understanding of geodynamics. Despite extensive studies, the offshore portion of subduction interfaces is usually poorly constrained due to the limited use of available marine constraints in current models. Here, we present a new 3-D offshore geometry of the Nazca-South AMerica (NSAM) subduction interface off western South America based on a comprehensive compilation of offshore active seismic data. We use 66 multi-channel, and 30 wide-angle seismic profiles acquired from Colombia (4°N) to southern Chile (46°S), covering a margin-length of 6,000 km, to generate a high-precision mesh (± 0.5 km). This data product contributes to scientific and applied research on one of the longest and most active subduction zones on Earth and enhances our understanding of global subduction zone processes and geohazards.
{"title":"Offshore geometry of the South America subduction zone plate boundary","authors":"Eduardo Contreras-Reyes , Matías Carvajal , Felipe González","doi":"10.1016/j.epsl.2024.119175","DOIUrl":"10.1016/j.epsl.2024.119175","url":null,"abstract":"<div><div>Accurate and precise 3-D geometry models of subduction zone plate boundaries are crucial for advancing earthquake science, enhancing hazard assessments, and improving our understanding of geodynamics. Despite extensive studies, the offshore portion of subduction interfaces is usually poorly constrained due to the limited use of available marine constraints in current models. Here, we present a new 3-D offshore geometry of the Nazca-South AMerica (NSAM) subduction interface off western South America based on a comprehensive compilation of offshore active seismic data. We use 66 multi-channel, and 30 wide-angle seismic profiles acquired from Colombia (4°N) to southern Chile (46°S), covering a margin-length of 6,000 km, to generate a high-precision mesh (± 0.5 km). This data product contributes to scientific and applied research on one of the longest and most active subduction zones on Earth and enhances our understanding of global subduction zone processes and geohazards.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"651 ","pages":"Article 119175"},"PeriodicalIF":4.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143157737","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}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号