Filtering by Subject: Mineral Physics

A non-equilibrium slurry model for planetary cores with application to Earth’s F-layer

Andrew Walker, Chris Davies, Alfred Wilson, et al.

Published: 2024-07-09
Subjects: Earth Sciences, Fluid Dynamics, Geophysics and Seismology, Mineral Physics

Slurry regions may exist in the cores of several terrestrial bodies and are expected to influence the dynamics of deep planetary interiors and the viability of maintaining global magnetic fields. Here we develop a two-component slurry model of the lowermost outer core of the Earth (the F-layer). In contrast to most previous models of slurries in planetary cores, we explicitly model the physics [...]

The sensitivity of lowermost mantle anisotropy to past mantle convection

James A Ward, Andrew Walker, Andy Nowacki, et al.

Published: 2024-06-20
Subjects: Geophysics and Seismology, Mineral Physics

It is widely believed that seismic anisotropy in the lowermost mantle is caused by the flow-induced alignment of anisotropic crystals such as post-perovskite. What is unclear, however, is whether the anisotropy observations in the lowermost mantle hold information about past mantle flow, or if they only inform us about the present-day flow field. To investigate this, we compare the general and [...]

Theoretical infrared signature of OH defects in Fe3+, Cr3+ and Al3+-doped enstatite

Etienne Balan, Jannick Ingrin

Published: 2024-06-08
Subjects: Mineral Physics

The infrared spectroscopic properties of selected defects involving one proton and one nearby M3+ (M=Al, Cr, Fe) substitution in orthoenstatite are investigated by first- principles calculations. Based on the theoretical results, the absorption bands experimentally observed on synthetic samples with high crystalline quality and low doping levels can be assigned to specific defect configurations. [...]

Synchrotron radiation reveals transient weakening during mineral phase transformations

Andrew J. Cross, Rellie Goddard, Kathryn M Kumamoto, et al.

Published: 2024-05-13
Subjects: Earth Sciences, Geology, Mineral Physics, Tectonics and Structure

Phase transformations are widely invoked as a source of rheological weakening during subduction, continental collision, mantle convection, and various other geodynamic phenomena. However, the likelihood and magnitude of such weakening in nature remains undetermined. Here, experiments performed on a synchrotron beamline reveal dramatic weakening across the polymorphic quartz↔coesite phase [...]

Grüneisen parameter formalism in the study of the Earth's core formation: a sensitivity study

Vincent Clesi, Renaud Deguen

Published: 2024-03-21
Subjects: Condensed Matter Physics, Earth Sciences, Geochemistry, Geology, Mineral Physics, Other Earth Sciences, Planetary Geophysics and Seismology, Planetary Mineral Physics, Planetary Sciences

The Grüneisen parameter is an important parameter for the thermal state and evolution of the core, but its uncertainties and their implications are sometimes overlooked . Several formalisms using different parameters values have been used in different studies, making comparison between studies difficult. In this paper, we use previously published datasets to test the sensitivity of modeling the [...]

Three-dimensional mineral dendrites reveal a non-classical crystallization pathway

Zhaoliang Hou, Dawid Woś, Cornelius Tschegg, et al.

Published: 2024-03-04
Subjects: Earth Sciences, Fluid Dynamics, Geochemistry, Mineral Physics, Physical Sciences and Mathematics, Physics

Manganese (Mn) dendrites are a common type of mineral dendrite that typically forms two-dimensional structures on rock surfaces. Three-dimensional (3D) Mn dendrites in rocks have rarely been reported, hence their growth implications have largely escaped attention. Here, we combine high-resolution X-ray and electron-based data with numerical modelling to give the first detailed description of [...]

Excited state lifetime of electron trapping centres in alkali feldspars

Svenja Riedesel, Mayank Jain

Published: 2023-11-02
Subjects: Earth Sciences, Mineral Physics, Other Earth Sciences, Physical Sciences and Mathematics, Physics

The development of the infrared photoluminescence (IRPL) signal enables the direct non-destructive probing of the trapped electron population in feldspars. Whilst IRPL offers new perspectives for luminescence dating, it also enables detailed, site-selective measurements of the dosimetric defects emitting IRPL at 880 nm (IRPL880) and 955 nm (IRPL955), allowing improved understanding of [...]

A key role for diffusion creep in eclogites: Omphacite deformation in the Zermatt-Saas Unit, Italian Alps

David Daniel McNamara, John Wheeler, Mark Pearce, et al.

Published: 2023-04-18
Subjects: Earth Sciences, Geochemistry, Geology, Mineral Physics, Tectonics and Structure

Eclogites are important components of subduction-collision zones, with the mineral omphacite acting as the supporting framework mineral that accommodates the majority of any accumulated strain. As such it is important to determine which deformation mechanisms operate in omphacite during and after its formation to understand the rheology of deforming subducted crust. Such information is key to [...]

Examining the power supplied to Earth's dynamo by magnesium precipitation and radiogenic heat production

Alfred Wilson, Monica Pozzo, Chris Davies, et al.

Published: 2023-04-05
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics, Planetary Sciences

We examine magnesium and potassium solubility in liquid Fe mixtures, representative of Earth’s core composition, in equilibrium with liquid silicate mixtures representative of an early magma ocean. Our study is based on the calculation of the chemical potentials of MgO and K2O in both phases, using density functional theory. For MgO, we also study stability against precipitation of the solid [...]

Compressibility of ferropericlase at high-temperature: evidence for the iron spin crossover in seismic tomography

Viktoria Elisabeth Trautner, Stephen Stackhouse, Alice Turner, et al.

Published: 2023-04-05
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics

The iron spin crossover in ferropericlase, the second most abundant mineral in Earth’s lower mantle, causes changes in a range of physical properties, including seismic wave velocities. Understanding the effect of temperature on the spin crossover is essential to detect its signature in seismic observations and constrain its occurrence in the mantle. Here, we report the first experimental results [...]

DiadFit: An Open-Source Python3 Tool for Peak fitting of Raman Data from silicate melts and CO2 fluids

Penny E Wieser, Charlotte L DeVitre

Published: 2023-04-04
Subjects: Earth Sciences, Geology, Mineral Physics, Physical Sciences and Mathematics, Volcanology

We present DiadFit - an open-source Python3 tool for efficient processing of Raman spectroscopy data collected from fluidinclusions, melt inclusions and silicate melts. DiadFit is optimized to fit the characteristic peaks from CO2 fluids (Fermi diads,hot bands, 13C), gas species such as SO2, N2, solid precipitates (e.g., carbonates), and Ne emission lines with easily tweakablebackground positions [...]

Can homogeneous nucleation resolve the inner core nucleation paradox?

Alfred Wilson, Dario Alfè, Andrew Walker, et al.

Published: 2023-03-24
Subjects: Condensed Matter Physics, Earth Sciences, Geophysics and Seismology, Mineral Physics, Planetary Geophysics and Seismology, Planetary Mineral Physics

Barometers behaving badly: Assessing the influence of analytical and experimental uncertainty on clinopyroxene thermobarometry calculations at crustal conditions

Penny E Wieser, Adam J Kent, Christy Till, et al.

Published: 2022-12-01
Subjects: Earth Sciences, Geochemistry, Geology, Mineral Physics, Volcanology

The composition of clinopyroxene and Clinopyroxene-Liquid (Cpx-Liq) pairs are frequently used to calculate crystallization/equilibration pressures in igneous systems. While canonical uncertainties are often assigned to calculated pressures based on fits to calibration or test datasets, the sources of these uncertainties (and thus ways to reduce them) have not been rigorously assessed. We show [...]

Comparative study of alteration sequences in pegmatitic aluminium phosphates

Cassian P. F. Pirard

Published: 2022-09-29
Subjects: Earth Sciences, Geochemistry, Geology, Mineral Physics, Other Earth Sciences

Aluminium phosphates are mineral phases commonly occurring in rare-element pegmatites that record initial magmatic crystallization, metasomatic and hydrothermal replacements and precipitation and low-temperature alteration. Here we perform a comparative mineralogical study between several localities to assess similarities and variations in these parageneses and establish a general alteration [...]

Characterisation of phosphate mineralogy in Montebras-en-Soumans Pegmatite, Massif Central, France

Cassian P. F. Pirard

Published: 2022-09-22
Subjects: Earth Sciences, Geochemistry, Geology, Mineral Physics

Montebras-en-Soumans pegmatitic cupola hosts large pods of phosphate composed of primary amblygonite-montebrasite. These aluminium phosphate masses are considerably altered by post-magmatic processes producing a number of secondary metasomatic hydrothermal phosphates (lacroixite, wardite, morinite, viitaniemiite, apatite, triplite, eosphorite) and low-temperature phosphates (apatite, crandallite, [...]


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