Preprints

Filtering by Subject: Mineral Physics

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

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

Published: 2020-06-30
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: 2020-06-23
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, et al.

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 mechanism of Mg diffusion in forsterite and the controls on its anisotropy

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 rheological properties in forsterite but its mechanism is unknown. Without knowing a mechanism the effect of variables such as pressure are hard to constrain. In this study we used Density Functional Theory (DFT) to calculate the diffusivity of Mg vacancies and interstitials in forsterite and thus the diffusion rate of Mg in forsterite. We predict [...]

Notes on the creation and manipulation of solid solution models

Robert Myhill, James Connolly

Published: 2019-12-05
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, et al.

Published: 2019-11-15
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 Jennings, Ian A. Franchi, et al.

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: 2019-11-01
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 James Bower

Published: 2019-09-07
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 James Bower, Michael Gurnis, Maria Seton

Published: 2019-09-07
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

Dan James Bower, Michael Gurnis, Daoyuan Sun

Published: 2019-09-07
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

Dan James Bower, June K. Wicks, Michael Gurnis, et al.

Published: 2019-09-07
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

Dan James Bower, Michael Gurnis, Jennifer M. Jackson, et al.

Published: 2019-09-07
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

Simon Hunt, Andrew Walker, Oliver Lord, et al.

Published: 2019-08-22
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

Markus Ohl, Oliver Plümper, Vasileios Chatzaras, et al.

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 [...]

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