Preprints
Filtering by Subject: Mineral Physics
An equation of state for high pressure-temperature liquids (RTpress) with application to MgSiO3 melt
Published: 2019-09-06
Subjects: Earth Sciences, Mineral Physics, Physical Sciences and Mathematics
The thermophysical properties of molten silicates at extreme conditions are crucial for understanding the early evolution of Earth and other massive rocky planets, which is marked by giant impacts capable of producing deep magma oceans. Cooling and crystallization of molten mantles are sensitive to the densities and adiabatic profiles of high-pressure molten silicates, demanding accurate Equation [...]
Lower mantle structure from paleogeographically constrained dynamic Earth models
Published: 2019-09-06
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics
Seismic tomography reveals two large, low-shear velocity provinces (LLSVPs) beneath Africa and the Pacific Ocean. These structures may have existed for several 100 Myr and are likely compositionally distinct based on observed seismic characteristics interpreted in light of geodynamic models and mineral physics constraints. We investigate the dynamics of the LLSVPs through the use of evolutionary [...]
Dynamic origins of seismic wavespeed variation in D
Published: 2019-09-06
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics
The D discontinuity is defined by a seismic velocity increase of 1–3% about 250 km above the core–mantle boundary (CMB), and is mainly detected beneath locations of inferred paleosubduction. A phase change origin for the interface can explain a triplicated arrival observed in seismic waveform data and is supported by the recent discovery of a post-perovskite phase transition. We investigate the [...]
A geodynamic and mineral physics model of a solid-state ultralow-velocity zone
Published: 2019-09-06
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics
Recent results (Wicks et al., 2010) suggest that a mixture of iron-enriched (Mg,Fe)O and ambient mantle is consistent with wavespeed reductions and density increases inferred for ultralow-velocity zones (ULVZs). We explore this hypothesis by simulating convection to deduce the stability and morphology of such chemically-distinct structures. The buoyancy number, or chemical density anomaly, [...]
Enhanced Convection and Fast Plumes in the Lower Mantle Induced by the Spin Transition in Ferropericlase
Published: 2019-09-06
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics
Using a numerical model we explore the consequences of the intrinsic density change (Δρ/ρ ≈ 2–4%) caused by the Fe2+ spin transition in ferropericlase on the style and vigor of mantle convection. The effective Clapeyron slope of the transition from high to low spin is strongly positive in pressure‐temperature space and broadens with high temperature. This introduces a net spin‐state driving [...]
The anelasticity of zinc and its implications for the Earth’s inner core
Published: 2019-08-21
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics
The Earth’s inner core exhibits significant anisotropy in both seismic velocity and attenuation as well as hemispherical and depth variations. These observations point to an inner core that is both complex and dynamic. However, interpretation of these observations without knowledge of the attenuation processes active in the inner-core is difficult. To address this we have used zinc, as a [...]
Mechanisms of fault mirror formation and fault healing in carbonate rocks
Published: 2019-05-14
Subjects: Earth Sciences, Life Sciences, Mineral Physics, Physical Sciences and Mathematics
The development of smooth, mirror-like surfaces provides insight into the mechanical behaviour of crustal faults during the seismic cycle. To determine the thermo-chemical mechanisms of fault mirror formation, we investigated carbonate fault systems in seismically active areas of central Greece. Using multi-scale electron microscopy combined with Raman and electron energy loss spectroscopy, we [...]
Microstructural Constraints on Magmatic Mushes under Kīlauea Volcano, Hawaiʻi
Published: 2019-05-06
Subjects: Earth Sciences, Geochemistry, Geology, Mineral Physics, Physical Sciences and Mathematics, Volcanology
Distorted olivines of enigmatic origin are ubiquitous in erupted products from a wide range of volcanic systems (e.g., Hawaiʻi, Iceland, Andes). Investigation of these features at Kīlauea Volcano, Hawai’i, using an integrative crystallographic and chemical approach places quantitative constraints on mush pile thicknesses. Electron back-scatter diffraction (EBSD) reveals that the microstructural [...]
Anomalous structure of MgCO3 liquid and the buoyancy of carbonatite melts
Published: 2019-04-23
Subjects: Earth Sciences, Geochemistry, Mineral Physics, Physical Sciences and Mathematics
MgCO3 is one of the most important components of mantle-derived carbonatite melts, and yet also one of the most difficult to study experimentally. Attempts to constrain its thermodynamic properties are hampered by decarbonation, which occurs at only ~500 °C, far below its metastable 1 bar melting temperature. Molecular dynamic simulations, however, can predict the thermodynamic properties of the [...]
High-angular resolution electron backscatter diffraction as a new tool for mapping lattice distortion in geological minerals
Published: 2019-04-18
Subjects: Earth Sciences, Geology, Mineral Physics, Physical Sciences and Mathematics
Analysis of distortions of the crystal lattice within individual mineral grains is central to the investigation of microscale processes that control and record tectonic events. These distortions are generally combinations of lattice rotations and elastic strains, but a lack of suitable observational techniques has prevented these components being mapped simultaneously and routinely in earth [...]
Core Formation and Geophysical Properties of Mars
Published: 2019-02-25
Subjects: Earth Sciences, Geochemistry, Mineral Physics, Physical Sciences and Mathematics, Planetary Geophysics and Seismology, Planetary Sciences
The chemical and physical properties of the interiors of terrestrial planets are largely determined during their formation and differentiation. Modeling a planet’s formation provides important insights into the properties of its core and mantle, and conversely, knowledge of those properties may constrain formational narratives. Here, we present a multi-stage model of Martian core formation in [...]
Structure and elasticity of phlogopite under compression: Geophysical implications
Published: 2018-10-09
Subjects: Earth Sciences, Mineral Physics, Physical Sciences and Mathematics
We investigated the response of the crystal structure, lattice parameters, and unit-cell volume of hydrous layered silicate phlogopite at conditions relevant to subduction zone settings. We have used first principles simulation based on density functional theory to calculate the equation of state and full elastic constant tensor. Based on the generalized gradient approximation, the full single [...]
Segregation of bare and protonated Mg vacancies to dislocation cores in MgO
Published: 2018-09-27
Subjects: Earth Sciences, Mineral Physics, Physical Sciences and Mathematics
Water can be incorporated into the lattice of mantle minerals in the form of protons charge-balanced by the creation of cation vacancies. These protonated vacancies, when they interact with dislocations, increase strain rates by enhancing dislocation climb and, potentially, by reducing the Peierls barrier to glide. We use atomic scale simulations to investigate segregation of Mg vacancies to [...]
Atomistic simulations of Mg vacancy segregation to dislocation cores in forsterite
Published: 2018-09-27
Subjects: Earth Sciences, Mineral Physics, Physical Sciences and Mathematics
Interactions between dislocations in olivine and extrinsic cation vacancies created under hydrous or oxidizing conditions may influence the rheology of the Earths upper mantle. In this study, we use atomic-scale simulations to calculate segregation energies for bare and protonated Mg vacancies to M1 and M2 sites in the core regions of [100](010) and [001](010) edge dislocations, and [100] and [...]
Lubrication of dislocation glide in forsterite by Mg vacancies: insights from Peierls-Nabarro modeling
Published: 2018-07-26
Subjects: Condensed Matter Physics, Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics, Physics
Dislocation glide is an important contributor to the rheology of olivine under conditions of high stress and low to moderate temperature, such as occur in mantle wedges. Interactions between point defects and dislocation core may alter the Peierls stress,