Filtering by Subject: Mineral Physics

Shear-wave Anisotropy in the Earth’s Inner Core

Sheng Wang, Hrvoje Tkalčić

Published: 2021-09-17
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics

Earth’s inner core anisotropy is widely used to infer the deep Earth's evolution and present dynamics. Many compressional-wave anisotropy models have been proposed based on seismological observations. In contrast, inner-core shear-wave (J-wave) anisotropy – on a par with the compressional-wave anisotropy – has been elusive. Here we present a new class of the J-wave anisotropy observations [...]

Safety and Belonging in the Field: A Checklist for Educators

Sarah E Greene, Gwen S. Antell, Jake Atterby, et al.

Published: 2021-08-19
Subjects: Atmospheric Sciences, Biogeochemistry, Climate, Cosmochemistry, Earth Sciences, Education, Environmental Education, Environmental Health and Protection, Environmental Indicators and Impact Assessment, Environmental Monitoring, Environmental Sciences, Environmental Studies, Fresh Water Studies, Geochemistry, Geographic Information Sciences, Geography, Geology, Geomorphology, Geophysics and Seismology, Glaciology, Higher Education, Human Geography, Hydrology, Life Sciences, Meteorology, Mineral Physics, Natural Resource Economics, Natural Resources and Conservation, Natural Resources Management and Policy, Nature and Society Relations, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Oil, Gas, and Energy, Other Earth Sciences, Other Environmental Sciences, Other Geography, Other Oceanography and Atmospheric Sciences and Meteorology, Other Planetary Sciences, Outdoor Education, Paleobiology, Paleontology, Physical and Environmental Geography, Physical Sciences and Mathematics, Planetary Biogeochemistry, Planetary Geochemistry, Planetary Geology, Planetary Geomorphology, Planetary Geophysics and Seismology, Planetary Glaciology, Planetary Hydrology, Planetary Mineral Physics, Planetary Sciences, Planetary Sedimentology, Remote Sensing, Sedimentology, Social and Behavioral Sciences, Soil Science, Spatial Science, Speleology, Stratigraphy, Sustainability, Tectonics and Structure, Volcanology, Water Resource Management

Ensuring taught fieldwork is a positive, generative, collective, and valuable experience for all participants requires considerations beyond course content. To guarantee safety and belonging, participants’ identities (backgrounds and protected characteristics) must be considered as a part of fieldwork planning and implementation. Furthermore, getting fieldwork right is an important step in [...]

Machine learning thermobarometry and chemometry using amphibole and clinopyroxene: a window into the roots of an arc volcano (Mount Liamuiga, Saint Kitts)

Oliver John Higgins, Tom Sheldrake, Luca Caricchi

Published: 2021-07-04
Subjects: Earth Sciences, Geochemistry, Mineral Physics, Stratigraphy, Volcanology

The physical and chemical properties of magma govern the eruptive style and behaviour of volcanoes. Many of these parameters are linked to the storage pressure and temperature of the erupted magma, and melt chemistry. However, reliable single-phase thermobarometers and chemometers which can recover this information, particularly using amphibole chemistry, remain elusive. We present a suite of [...]

Geodynamic, geodetic, and seismic constraints favour deflated and dense-cored LLVPs

Fred Richards, Mark James Hoggard, Siavash Ghelichkhan, et al.

Published: 2021-06-18
Subjects: Cosmochemistry, Earth Sciences, Geochemistry, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics

Two continent-sized features in the deep mantle, the large low-velocity provinces (LLVPs), influence Earth's supercontinent cycles, mantle plume generation, and its geochemical budget. Seismological advances have steadily improved LLVP imaging, but several fundamental questions remain unanswered, including: What is their vertical extent? And, are they purely thermal anomalies, or are they also [...]

Interphase misorientation as a tool to study metamorphic reactions and crystallization in geological materials

Luiz F. G. Morales

Published: 2021-06-07
Subjects: Geology, Mineral Physics, Other Earth Sciences

Interphase boundaries are planar defects that separate two different minerals, which in general have different compositions and/or crystalline structures and may play an important role as a pathway for fluids in rocks and affect their physical properties. For the proper characterization of interphase boundaries, one needs to define the misorientation between adjacent grains and the orientation of [...]

Timing of Martian Core Formation from Models of Hf–W Evolution Coupled with N-body Simulations

Matthew C Brennan, Rebecca A Fischer, Francis Nimmo, et al.

Published: 2021-06-04
Subjects: Geochemistry, Mineral Physics, Planetary Sciences

Determining how and when Mars formed has been a long-standing challenge for planetary scientists. The size and orbit of Mars are difficult to reproduce in classical simulations of planetary accretion, and this has inspired models of inner solar system evolution that are tuned to produce Mars-like planets. However, such models are not always coupled to geochemical constraints. Analyses of Martian [...]

Assessment of quartz grain growth and the application of the wattmeter to predict recrystallized grain sizes

Leif Tokle, Greg Hirth

Published: 2020-12-04
Subjects: Geology, Mineral Physics, Tectonics and Structure

We investigated relationships between the recrystallized grain size and stress in experimentally deformed water-added quartz aggregates. For stresses >100 MPa there is a variation in the measured recrystallized grain size for a given stress. We found this variation correlates with a change in the c-axis fabric in general shear experiments, where samples with larger recrystallized grain sizes for [...]

The miscibility of Calcium Silicate Perovskite and Bridgmanite: A single phase perovskite in hot, iron-rich regions

Joshua Martin Richard Muir, Feiwu Zhang

Published: 2020-11-01
Subjects: Earth Sciences, Mineral Physics, Physical Sciences and Mathematics

Calcium silicate perovskite and bridgmanite are two phases believed to coexist throughout the lower mantle, which at some temperature, at least theoretically, dissolve into each other to form a single perovskite solid solution (CaxMg1-xSiO3). This may have large seismic and geochemical implications due to the changes in density, elasticity and element partition coefficients between single and [...]

High-Pressure Deformation of Iron–Nickel–Silicon Alloys and Implications for Earth’s Inner Core

Matthew C Brennan, Rebecca A Fischer, Samantha Couper, et al.

Published: 2020-10-21
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics

Earth’s inner core exhibits strong seismic anisotropy, often attributed to the alignment of hexagonal close-packed iron (hcp-Fe) alloy crystallites with the Earth’s poles. How this alignment developed depends on material properties of the alloy and is important to our understanding of the core’s crystallization history and active geodynamical forcing. Previous studies suggested that hcp-Fe is [...]

Quantification of non-linear multiphase flow in porous media

Yihuai Zhang, Branko Bijeljic, Ying Gao, et al.

Published: 2020-08-20
Subjects: Earth Sciences, Engineering, Hydrology, Life Sciences, Medicine and Health Sciences, Mineral Physics, Physical Sciences and Mathematics

We measure the pressure difference during two-phase flow across a sandstone sample for a range of injection rates and fractional flows of water, the wetting phase, during an imbibition experiment. We quantify the onset of a transition from a linear relationship between flow rate and pressure gradient to a non-linear power-law dependence. We show that the transition from linear (Darcy) to [...]

Explaining the dependence of M-site diffusion in forsterite on silica activity: a Density Functional Theory approach

Joshua Martin Richard Muir, Michael Jollands, Zhang Feiwu, et al.

Published: 2020-07-29
Subjects: Earth Sciences, Mineral Physics, Physical Sciences and Mathematics

Experimentally silica activity (aSiO2) has been shown to have an effect on Mg diffusion in forsterite but without any obvious mechanism. We calculated the effects of aSiO2 and aluminium content (the main contaminant in the experimental studies), and their co-effect, on Mg diffusion in forsterite, using thermodynamic minimisations of defect formation energies (calculated using Density Functional [...]

Dislocation interactions in olivine control postseismic creep of the upper mantle

David Wallis, Lars Hansen, Angus J. Wilkinson, et al.

Published: 2020-06-29
Subjects: Condensed Matter Physics, Earth Sciences, Geology, Mineral Physics, Physical Sciences and Mathematics, Physics, Tectonics and Structure

Changes in stress applied to mantle rocks, such as those imposed by earthquakes, induce a period of evolution in viscosity and microstructure. This transient creep is often modelled based on stress transfer among slip systems due to grain interactions. However, recent experiments have demonstrated that the intragranular accumulation of stresses among dislocations is the dominant cause of strain [...]

Seismological Expression of the Iron Spin Crossover in Ferropericlase in the Earth’s Lower Mantle

Grace Shephard, Christine Houser, John Hernlund, et al.

Published: 2020-06-29
Subjects: Earth Sciences, Geochemistry, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics, Physics, Quantum Physics, Tectonics and Structure

The two most abundant minerals on Earth which together make up over 90% of the Earth’s lower mantle are (Mg,Fe)O-ferropericlase (Fp) and (Mg,Fe)SiO3-bridgmanite (Bm). Iron in Fp undergoes a high-spin to low-spin (HS-LS) crossover that influences density, viscosity, elasticity, thermal conductivity, and elemental partitioning, however, the predicted effects of this transition are not apparent in [...]

Rates of olivine grain growth during dynamic recrystallization and post-deformation annealing

Pamela Speciale, Whitney M. Behr, Greg Hirth, et al.

Published: 2020-06-22
Subjects: Earth Sciences, Geology, Mineral Physics, Physical Sciences and Mathematics, Tectonics and Structure

We performed deformation and grain growth experiments on natural olivine aggregates with moderate olivine water contents (COH = 600±300 ppm H/Si) at 1000-1200°C and a confining pressure of 1400±100 MPa. Our experiments differ from published grain growth studies in that most were: 1) conducted on natural olivine cores rather than hot-pressed aggregates, and 2) dynamically recrystallized prior to [...]

International disparities in open access practices of the Earth Sciences community

Olivier Pourret, David William Hedding, Dasapta Erwin Irawan, et al.

Published: 2020-03-30
Subjects: Biogeochemistry, Cosmochemistry, Earth Sciences, Geochemistry, Geology, Geomorphology, Geophysics and Seismology, Glaciology, Hydrology, Library and Information Science, Mineral Physics, Other Earth Sciences, Paleobiology, Paleontology, Physical Sciences and Mathematics, Sedimentology, Social and Behavioral Sciences, Soil Science, Speleology, Stratigraphy, Tectonics and Structure, Volcanology

Short communication on international disparities in open access practices of the Earth Sciences community


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