Preprints

Filtering by Subject: Mineral Physics

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

Joshua Martin Richard Muir, Feiwu Zhang

Published: 2020-11-02
Subjects: Earth Sciences, Mineral Physics, Physical Sciences and Mathematics

Calcium silicate perovskite and bridgmanite are two phases which coexist in the lower mantle but at some temperature will dissolve into each other to form a single phase. In this work we use DFT to calculate the temperature at which this occurs at 3 pressures- 25, 75 and 125 GPa. At these three pressures we find solubility of Ca in Mg of 0.41/0.52/0.92 % at 2000 K and 0.72/1.07/3.30 % at 2500 K [...]

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

Matthew C Brennan, Rebecca A Fischer, Samantha Couper, Lowell Miyagi, Daniele Antonangeli, Guillaume Morard

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, Qingyang Lin, Martin J. Blunt

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, Andrew Walker

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, Ricardo A. Lebensohn

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 E. Shephard, Christine Houser, John Hernlund, Juan J. Valencia-Cardona, Reidar Trønnes, Renata Wentzkovitch

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 Behr, Greg Hirth, Leif Tokle

Published: 2020-06-23
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, Haiyan Liu, Jonathan Tennant

Published: 2020-03-31
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

The controls of pressure and water on highly anisotropic Mg diffusion in forsterite

Joshua Martin Richard Muir, Zhang Feiwu, Andrew Walker

Published: 2020-03-31
Subjects: Earth Sciences, Mineral Physics, Physical Sciences and Mathematics

Mg diffusion is important for explaining many deformational properties in forsterite but its mechanism is unknown and so the effect of variables such as pressure or water content is difficult to constrain. Knowing the effect of water on Mg diffusion is important, as some parts of the upper mantle are very wet. In this study we used DFT to calculate the anhydrous and hydrous diffusion of Mg in [...]

Notes on the creation and manipulation of solid solution models

Robert Myhill, James Connolly

Published: 2019-12-04
Subjects: Chemistry, Earth Sciences, Materials Chemistry, Mineral Physics, Physical Sciences and Mathematics

A large class of solid solution models are built on the premise that exchange of chemical species takes place on a finite number of unique sites, and that the thermodynamic properties of the solution are a function of the proportions of species occupying each of the sites. The site-occupancy spaces spanned by such models are geometrically equivalent to convex polytopes, n-dimensional [...]

Ultramafic rock carbonation: Constraints from listvenite core BT1B, Oman Drilling Project

Andreas Beinlich, Oliver Plümper, Esmée Boter, Inigo A. Müller, Fatma Kourim, Martin Ziegler, Yumiko Harigane, Romain Lafay, Peter B. Kelemen

Published: 2019-11-14
Subjects: Earth Sciences, Geochemistry, Geology, Mineral Physics, Other Earth Sciences, Physical Sciences and Mathematics

The occurrence of the quartz–carbonate alteration assemblage (listvenite) in ophiolites indicates that ultramafic rock represents an effective sink for dissolved CO2. However, the majority of earlier studies of ultramafic rock carbonation had to rely on the surface exposure of reaction textures and field relationships. Here we present the first observations on ultramafic rock alteration obtained [...]

The Fate of Carbon during Earth’s Core–Mantle Differentiation

Ingrid Blanchard, Eleanor S. Jennings, Ian A. Franchi, Xuchao Zhao, Sylvain Petitgirard, Nobuyoshi Miyajima, Seth Andrew Jacobson, Dave Rubie

Published: 2019-11-14
Subjects: Earth Sciences, Geochemistry, Mineral Physics, Physical Sciences and Mathematics

Carbon is an essential element for the existence and evolution of life on Earth, constitutes up to 50% of dry biomass, and is likely a requirement for all life in the universe. Its high abundance in Earth’s crust and mantle (the Bulk Silicate Earth, BSE) is surprising because carbon is strongly siderophile (metal-loving) and should have segregated almost completely into Earth’s core during [...]

The variation and visualisation of elastic anisotropy in rock-forming minerals

David Healy, Nicholas Timms, Mark Pearce

Published: 2019-10-31
Subjects: Earth Sciences, Geochemistry, Geology, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics, Tectonics and Structure

All minerals behave elastically, a rheological property that controls their ability to support stress, strain and pressure, the nature of acoustic wave propagation and influences subsequent plastic (i.e. permanent, non-reversible) deformation. All minerals are intrinsically anisotropic in their elastic properties – that is, they have directional variations that are related to the configuration [...]

An equation of state for high pressure-temperature liquids (RTpress) with application to MgSiO3 melt

Aaron S. Wolf, Dan J. Bower

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

Dan J. Bower, Michael Gurnis, Maria Seton

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 [...]

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