Article
Geochemistry & Geophysics
Suzanne K. Birner, Elizabeth Cottrell, Jessica M. Warren, Katherine A. Kelley, Fred A. Davis
Summary: Mid-ocean ridge peridotites show greater variability in major and trace elements compared to their basaltic counterparts. Variability in peridotites from the Southwest Indian Ridge may come from modern ridge processes or long-lived source heterogeneity. Spinel geochemistry and oxygen fugacity were investigated in this study, showing that some peridotites record melt extraction and melt-rock interaction. Oxygen fugacity remains consistent during melting, with no significant changes caused by melt addition.
EARTH AND PLANETARY SCIENCE LETTERS
(2021)
Article
Geochemistry & Geophysics
D. W. Rees Jones, H. Zhang, R. F. Katz
Summary: Channels at mid-ocean ridges are believed to form through shear flow of partially molten mantle and reactive flow of ascending magma, with their competition being controlled by the orientation of channels with respect to gravity and mantle shear. The addition of horizontal extension favors tabular channel morphology. Reactive flow is dominant deep beneath the ridge axis, while shear-driven instability is confined to the margins of the melting region.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
James Jackson, Dan McKenzie
Summary: We examined 70 reverse-faulting earthquakes at slowly-spreading ridges in the Atlantic and Indian Oceans. These earthquakes occurred at shallow depths beneath gravity and bathymetric highs on ridge flanks, consistent with previous observations. A simple quantitative model explains their occurrence by the bending of an uplifted and exhumed elastic layer. The widespread distribution of these events suggests that asymmetric spreading is the dominant mode of extension at such ridges.
EARTH AND PLANETARY SCIENCE LETTERS
(2023)
Article
Geochemistry & Geophysics
Jonathan Wolf, Daniel A. Frost, Maureen D. Long, Edward Garnero, Adeolu O. Aderoju, Neala Creasy, Ebru Bozdag
Summary: Shear-wave splitting measurements are commonly used to resolve seismic anisotropy in both the upper and lowermost mantle. However, practical constraints such as limited suitable phases and poor signal-to-noise ratios or large measurement uncertainties limit the application of these techniques. This study investigates how a beamforming methodology can improve shear-wave splitting measurement confidence intervals and shows the potential of beamforming to improve the detection of lowermost mantle anisotropy.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2023)
Article
Geochemistry & Geophysics
Fernando Martinez, Richard Hey
Summary: The offset ridge-transform structure of ocean basins is a prominent expression of plate tectonics. This study investigates the reasons for this configuration by analyzing mantle Bouguer anomalies (MBAs). The results show that the pattern of mantle melting plays a crucial role in the formation of transform faults, as the distribution and extent of melting can affect the chemical and rheological properties of the residual mantle.
EARTH AND PLANETARY SCIENCE LETTERS
(2022)
Article
Geochemistry & Geophysics
Fenitra Andriampenomanana, Andrew A. Nyblade, Michael E. Wysession, Raymond J. Durrheim, Frederik Tilmann, Guilhem Barruol, Gerard Rambolamanana, Tsiriandrimanana Rakotondraibe
Summary: The lithosphere of Madagascar has undergone a long series of tectonic processes, from the Pan-African Orogeny to extensional tectonic and magmatic events. Studies show complex lateral variations in seismic velocity and anisotropy within the uppermost mantle, reflecting the tectonic history and thermal perturbations.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geosciences, Multidisciplinary
C. Sani, A. Sanfilippo, A. A. Peyve, F. Genske, A. Stracke
Summary: Mid ocean ridge basalts are partial melts of mantle rocks that have experienced incompatible element depletion. The extent of this depletion is usually inferred from the isotope ratios of ridge basalts, but higher levels of depletion have been found in abyssal peridotites. Peridotites from the Doldrums Fracture Zone exhibit ultra-depleted hafnium isotope signatures, indicating a larger extent of incompatible element depletion compared to ridge basalts. A better understanding of chemically reactive flow is necessary to determine the rate of incompatible element depletion in the mantle and understand Earth's evolution.
Article
Geology
J. M. Kendall, D. Schlaphorst, C. A. Rychert, N. Harmon, M. Agius, S. Tharimena
Summary: Parallel melt accumulation along the Mid-Atlantic Ridge was found, and this may enhance the driving forces of the plates.
Article
Geosciences, Multidisciplinary
Natalia Torres-Rodriguez, Jingjing Yuan, Sven Petersen, Aurelie Dufour, David Gonzalez-Santana, Valerie Chavagnac, Helene Planquette, Milena Horvat, David Amouroux, Cecile Cathalot, Ewan Pelleter, Ruoyu Sun, Jeroen E. Sonke, George W. Luther III, Lars-Eric Heimburger-Boavida
Summary: Methylmercury, a potent toxin, poses a threat to the global population through the consumption of marine fish. This study investigates the release of mercury from hydrothermal vents and finds that its contribution to oceanic mercury levels is small compared to anthropogenic inputs. The majority of mercury released from the vents is rapidly diluted in seawater, suggesting that most of the mercury in the ocean is of anthropogenic origin. Implementing emissions reduction measures could effectively decrease mercury levels in the global ocean and marine fish.
Article
Geosciences, Multidisciplinary
Y. Yuan, D. Sun, C. Thomas
Summary: Using dense stations in China, a new seismic phase, PdpP, caused by mid-mantle heterogeneities, has been observed. This phase appears in two forms and can be simultaneously generated by lower mantle scatterers located close to the source region. By studying PdpP observations from Fiji-Tonga earthquakes, a series of scatterers at depths of 800-1,350 km related to the subduction of the Pacific slab along the Tonga-Kermadec trench have been located.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Geosciences, Multidisciplinary
S. J. Sim
Summary: The geomorphology of the ocean floor is not fully understood, and recent debate has focused on whether sea level changes affect the ocean floor texture. Using two-phase flow simulations of ridge magma transport, it is found that persistent melt-rich porosity waves could be responsible for the ocean floor fabric at periods of 100 kyr and longer.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geochemistry & Geophysics
Venkata A. Vaddineni, Satish C. Singh, Ingo Grevemeyer, Pranav Audhkhasi, Cord Papenberg
Summary: This study presents seismic tomographic results from a unique survey in the equatorial Atlantic Ocean, revealing changes in crustal velocities and thickness as well as the presence of partial melt in the lower crust. The evolution of the crust and uppermost mantle at this location occurs within the first 10 million years of formation, with most structures in older crust and upper mantle being fossilized and providing insight into past processes at ocean spreading centers.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2021)
Article
Multidisciplinary Sciences
Jie Chen, Jean- Arthur Olive, Mathilde Cannat
Summary: The thermal state of mid-ocean ridges plays a crucial role in seafloor spreading processes. Standard thermal models fail to explain the characteristics of shallow crustal Axial Melt Lenses (AMLs) observed at slow-ultraslow ridges. By decoupling the ridge magma supply from spreading rate, considering hydrothermal convection, and multiple modes of melt emplacement, a numerical model showed that melt flux is a better indicator of thermal regimes than spreading rate. It also highlighted the importance of along-axis melt focusing at slow-ultraslow ridges.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2023)
Article
Geosciences, Multidisciplinary
C. Beghein, J. Li, E. Weidner, R. Maguire, J. Wookey, V Lekic, P. Lognonne, W. Banerdt
Summary: Scientists have observed two different types of wave signals in seismic events on Mars, which cannot be explained by a single model, indicating the presence of seismic anisotropy. They discuss various possible origins of these signals, including crystal orientation, crack alignment, impacts, and volcanic eruptions.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geochemistry & Geophysics
Manuele Faccenda, Brandon P. Vanderbeek
Summary: The traditional approach of seismic tomography, which assumes mechanical isotropy, leads to significant artifacts in tomographic images and hinders quantitative integration with geodynamic flow models. This study uses geodynamic and seismological modeling to predict elastic properties and synthetic travel time datasets, and tests a methodology for anisotropic tomography. The results show that anisotropic inversions can recover isotropic and anisotropic structures, and provide unprecedented information about the deep geological structure.
JOURNAL OF GEODYNAMICS
(2023)
Article
Geochemistry & Geophysics
Jiaqi Li, Caroline Beghein, James Wookey, Paul Davis, Philippe Lognonne, Martin Schimmel, Eleonore Stutzmann, Matthew Golombek, Jean-Paul Montagner, William Bruce Banerdt
Summary: By analyzing the recorded broadband and low-frequency events on Mars, we have made the first detection of horizontally polarized shear wave reflections, which provide insights into the crustal structure of Mars. The analysis of marsquake signals indicates the presence of a crustal interface at a depth of approximately 8 km and a significant velocity contrast across it. Furthermore, our findings suggest the existence of seismic anisotropy within the top crustal layer at the lander site.
EARTH AND PLANETARY SCIENCE LETTERS
(2022)
Article
Geochemistry & Geophysics
Angelo Pisconti, Neala Creasy, James Wookey, Maureen D. Long, Christine Thomas
Summary: Recent advances in seismic anisotropy studies have provided significant insights into the structure and deformation of the D '' region beneath the South Atlantic. By analyzing seismic phases, researchers have detected a discontinuity within the D '' region and evidence of anisotropy. The study proposes a regional variation in mineralogy and deformation, suggesting the presence of distinct domains within and outside the large low seismic velocity province.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Sebastian Rost, Daniel A. Frost, Andy Nowacki, Laura Cobden
Summary: The seismic wavefield carries important information about the seismic source and Earth's structure, but current methods have limitations in resolving fine scale structure. In this study, we show that analyzing slowness vector deviations can help extend our knowledge to smaller scales. By analyzing seismic array data, we were able to detect strong focal and defocal effects of the teleseismic wavefield, providing more insight into the fine scale velocity structure of Earth's interior.
EARTH AND PLANETARY SCIENCE LETTERS
(2023)
Article
Multidisciplinary Sciences
Stephen P. Hicks, Lidong Bie, Catherine A. Rychert, Nicholas Harmon, Saskia Goes, Andreas Rietbrock, Songqiao Shawn Wei, Jenny S. Collier, Timothy J. Henstock, Lloyd Lynch, Julie Prytulak, Colin G. Macpherson, David Schlaphorst, Jamie J. Wilkinson, Jonathan D. Blundy, George F. Cooper, Richard G. Davy, John -Michael Kendall
Summary: Volatiles expelled from subducted plates affect the melting of the overlying mantle, which is important for arc volcanism. This study examines seismic attenuation beneath the Lesser Antilles arc and reveals the role of expelled fluids and melt in controlling volcanism. The results show that cold boundary layers transport fluids towards the back-arc, while warm mantle beneath the back-arc feeds arc volcanoes.
Article
Geochemistry & Geophysics
David Schlaphorst, Catherine A. Rychert, Nicholas Harmon, Stephen P. Hicks, Petros Bogiatzis, J-Michael Kendall, Rachel E. Abercrombie
Summary: Seismicity along transform faults provides important constraints for understanding earthquake ruptures. This study presents the first local seismicity catalog of slow spreading ridges based on data recorded by a temporary broad-band network. Most of the earthquakes are located along the Chain Transform Fault, Romanche transform fault, and the Mid-Atlantic Ridge. The seismic events are characterized by normal faulting along the ridge and strike-slip faulting along the transforms, with some reverse mechanisms.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geosciences, Multidisciplinary
T. S. Hudson, J. M. Kendall, J. D. Blundy, M. E. Pritchard, P. MacQueen, S. S. Wei, J. H. Gottsmann, S. Lapins
Summary: Mapping fluid distribution in the crust below Uturuncu volcano using seismic attenuation tomography reveals partially and fully fluid-saturated areas along aligned faults and fractures. Pressure-temperature profiles and conductivity data help identify the likely fluid composition, with shallow regions of dry and H2O/brine-saturated crust, and a deeper supercritical H2O/brine column. These observations provide insights into Uturuncu's transcrustal hydrothermal system and demonstrate the potential application of such methods for mapping crustal fluid pathways and hydrothermal/geothermal systems.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Geosciences, Multidisciplinary
T. S. Hudson, S. K. Kufner, A. M. Brisbourne, J. M. Kendall, A. M. Smith, R. B. Alley, R. J. Arthern, T. Murray
Summary: This study investigates the slip of glaciers over the underlying bed, which is the dominant mechanism governing the migration of ice into the oceans and contributes to sea-level rise. The researchers use passive seismic observations to measure frictional shear stress and slip at the bed of the Rutford Ice Stream in Antarctica. They find that basal shear stresses and slip rates vary significantly in both space and time, indicating that the bed is more complex than previously assumed in ice stream models. This research provides important constraints for ice-dynamics models and is critical for understanding the contribution of ice mass loss to sea-level rise.
Article
Geography, Physical
Adam D. D. Booth, Poul Christoffersen, Andrew Pretorius, Joseph Chapman, Bryn Hubbard, Emma C. C. Smith, Sjoerd de Ridder, Andy Nowacki, Bradley Paul Lipovsky, Marine Denolle
Summary: Distributed Acoustic Sensing (DAS) is a valuable tool for glaciological seismic applications, but analyzing the large data volumes generated poses computational challenges. Active-source DAS has the potential to image and characterize subglacial sediment, but the lack of subglacial velocity constraint limits accuracy. Compression using the frequency-wavenumber (f-k) transform and a convolutional neural network provides a significant improvement in efficiency for analyzing cryoseismic events. Combining active and passive-source data with machine learning frameworks unlocks the potential of large DAS datasets for future applications.
ANNALS OF GLACIOLOGY
(2023)
Article
Geosciences, Multidisciplinary
S. -K. Kufner, J. Wookey, A. M. Brisbourne, C. Martin, T. S. Hudson, J. M. Kendall, A. M. Smith
Summary: The crystal orientation fabric of glacier ice is crucial in determining its strength and flow behavior, making it an important factor in ice flow modeling. In this study, the authors demonstrate that shear-wave splitting (SWS) measured through glacial microseismicity can be used to infer seismic anisotropy and ice fabric in a statistical sense. By analyzing over 200,000 SWS measurements from a seismic network near Rutford Ice Stream in Antarctica, the researchers were able to identify a three-layer ice fabric structure with varying strengths and deformability along the flow direction. Their findings suggest that fast-flowing ice streams may require a more complex integration of viscosity in ice sheet models.
JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE
(2023)
Article
Geochemistry & Geophysics
M. Gauntlett, T. Hudson, J. -M. Kendall, N. Rawlinson, J. Blundy, S. Lapins, B. Goitom, J. Hammond, C. Oppenheimer, G. Ogubazghi
Summary: Understanding the crustal structure and the movement of fluids beneath a volcano is crucial for assessing volcanic hazard and exploring geothermal potential. This study uses earthquake tomography to image the seismic velocity structure beneath Nabro volcano in Ethiopia. The findings suggest the presence of solidified rocks and a primary melt storage region that fed the 2011 eruption. The observations also indicate the persistence of magma and the potential for geothermal exploration.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2023)
Article
Geochemistry & Geophysics
M. J. W. Bemelmans, J. Biggs, M. Poland, J. Wookey, S. K. Ebmeier, A. K. Diefenbach, D. Syahbana
Summary: During a volcanic crisis, high-resolution satellite SAR imagery was used to detect intra-crater uplift preceding the onset of eruptive activity. The deformation was attributed to the pressurization of a shallow hydrothermal system by magmatic gases and fluids. The observations have important implications for eruption forecasting and demonstrate the potential of monitoring with high-resolution SAR.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2023)
Article
Geochemistry & Geophysics
K. Leptokaropoulos, C. A. Rychert, N. Harmon, J. M. Kendall
Summary: Based on the study of the Chain transform in the equatorial Mid-Atlantic, it is found that the seismic activity is highest in the eastern area, while the western and central areas have lower seismic rates but release the majority of seismic moment. This segmentation is possibly due to variable fluid circulation and alteration.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2023)
Article
Engineering, Geological
Adrian White, Paul Wilkinson, James Boyd, James Wookey, John Michael Kendall, Andrew Binley, Timothy Grossey, Jonathan Chambers
Summary: Globally, earth embankments are used to protect against flooding. Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) are commonly used to identify and map animal burrows in these embankments. This study compared the efficacy of ERT and GPR in imaging badger burrow networks in clay embankments. The results showed that ERT can accurately resolve tunnels down to 1.5 m depth, while GPR surveys had limited penetration depth. The implications of this study include improved embankment management, reduced repair costs, and a better understanding of badger burrow geometry.
ENGINEERING GEOLOGY
(2023)
Article
Geology
J. M. Kendall, D. Schlaphorst, C. A. Rychert, N. Harmon, M. Agius, S. Tharimena
Summary: Parallel melt accumulation along the Mid-Atlantic Ridge was found, and this may enhance the driving forces of the plates.
Article
Geochemistry & Geophysics
Lingyu Zhang, Kristoffer Szilas
Summary: This study presents new petrological and geochemical data for the Narssaq Ultramafic Body (NUB) in the Itsaq Gneiss Complex of SW Greenland. The results indicate that the ultramafic rocks of NUB are not mantle residues, but instead represent crustal cumulates derived from high-Mg magmas.
EARTH AND PLANETARY SCIENCE LETTERS
(2024)
Article
Geochemistry & Geophysics
Rong Xu, Sarah Lambart, Oliver Nebel, Ming Li, Zhongjie Bai, Junbo Zhang, Ganglan Zhang, Jianfeng Gao, Hong Zhong, Yongsheng Liu
Summary: This study investigated the iron isotope compositions of Cenozoic basalts in Southeast China, finding significant variations related to different types of basalts and their respective sources.
EARTH AND PLANETARY SCIENCE LETTERS
(2024)
Article
Geochemistry & Geophysics
C. J. Ebinger, Miriam C. Reiss, Ian Bastow, Mary M. Karanja
Summary: The East African rift system is formed above mantle upwellings and the formation of rifts is related to lithospheric thinning and magmatic activity. The amount of splitting varies spatially and the fast axes are predominantly parallel to the orientation of the rifts. Thick lithospheric modules have less splitting and different orientations, which may indicate mantle plume flow. Splitting rotates and increases in strength as it enters the rift zones, suggesting that the anisotropy is mainly present at shallow depths.
EARTH AND PLANETARY SCIENCE LETTERS
(2024)
Correction
Geochemistry & Geophysics
Ekaterina Rojas-Kolomiets, Owen Jensen, Michael Bizimis, Gene Yogodzinski, Lukas Ackerman
EARTH AND PLANETARY SCIENCE LETTERS
(2024)
Article
Geochemistry & Geophysics
Robert W. Nicklas, Igor S. Puchtel, Ethan F. Baxter
Summary: Oxygen fugacity is a fundamental parameter for understanding redox processes in igneous systems. This study compares the Fe-XANES oxybarometry method with the V-in-olivine method for evaluating fO(2) in MORB lavas. The results show that the V-in-olivine method is not applicable to samples with low MgO content, and that the majority of Archean komatiite sources have lower fO(2) than modern MORB.
EARTH AND PLANETARY SCIENCE LETTERS
(2024)
Article
Geochemistry & Geophysics
Chunfei Chen, Stephen F. Foley, Sebastian Tappe, Huange Ren, Lanping Feng, Yongsheng Liu
Summary: The volatile components CO2 and H2O play a major role in mantle melting and heterogeneity. In this study, Ca isotopes were used to trace the lithological heterogeneity in alkaline magmatic rocks. The results revealed the presence of K-richterite and carbonate components as the source of alkaline magmas with low delta 44/40Ca values. These findings highlight the importance of Ca isotopes as a robust tracer of lithological variation caused by volatiles in the Earth's upper mantle.
EARTH AND PLANETARY SCIENCE LETTERS
(2024)
Article
Geochemistry & Geophysics
Timothee Jautzy, Gilles Rixhon, Regis Braucher, Romain Delunel, Pierre G. Valla, Laurent Schmitt, Aster Team
Summary: Although the current approach to estimate catchment-wide denudation rates using only 10Be concentrations has made significant progress in geomorphology, this study argues for the inclusion of 26Al measurements and testing of steady-state assumptions in slow eroding, formerly glaciated landscapes. The study conducted measurements of both 10Be and 26Al in stream sediments from the Vosges Massif in France and found that elevation, slope, channel steepness, and precipitation were the primary factors controlling denudation rates. The study also revealed a significant relationship between the extent of past glaciation and the cosmogenic (un-)steadiness in the stream sediments.
EARTH AND PLANETARY SCIENCE LETTERS
(2024)
Article
Geochemistry & Geophysics
Erik van der Wiel, Douwe J. J. van Hinsbergen, Cedric Thieulot, Wim Spakman
Summary: Numerical models of Earth's mantle dynamics can predict the vigour and mixing of mantle flow, and the average slab sinking rates are an unexplored parameter that can provide intrinsic information on these characteristics. Through numerical experiments, it has been found that slab sinking rates are strongly correlated with mantle convection and mixing, and may explain geochemical observations from hotspot volcanoes.
EARTH AND PLANETARY SCIENCE LETTERS
(2024)