Special Issue "Properties of Melt and Minerals at High Pressures and High Temperatures"

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Geochemistry and Geochronology".

Deadline for manuscript submissions: 31 July 2019

Special Issue Editor

Guest Editor
Prof. Claudia Romano

Dipartimento di Scienze, Università degli Studi Roma Tre, L.go San Leonardo Murialdo 1, 00146 Rome, Italy
Website | E-Mail
Interests: magma physical and chemical properties; properties of melt and minerals at high pressures and high temperatures; spectroscopic studies of inorganic materials; spectroscopic studies on volatiles species; experimental volcanology and petrology; crystallization dynamics; rheology of magma; water solubility and speciation; structure of silicate melts; eruption dynamics

Special Issue Information

Dear Colleagues,

High pressure, high temperature mineralogy has long played an essential role in our understanding of planetary interiors. As developments in high-pressure, high-temperature methods continue to emerge, we continue to broaden our insights on how the properties of minerals vary with depth from crust to mantle to core. Along with comparable advances made to analytical methods, we have reached levels of accuracy and precision in the determination of properties at extreme conditions that allow for a much sharper comprehension of Earth’s and other planetary interiors. Silicate melts are critical components in nearly every igneous process, particularly at conditions of high pressure. During Earth’s period of accretion silicate melts served as transport media leading to its chemical differentiation and formation of the core, mantle and crust. Like many minerals, the physical properties of silicate melts can be very sensitive to pressure, especially at conditions favoring the transformation of tetrahedral cations to pentahedral and octahedral species. Unique compression and decompression mechanisms can be the cause of anomalous behavior in the density and viscosity of evolving magmatic systems. Our understanding of how silicate melts behave at depths of the Earth is vital because of our vulnerability to the volcanic activity at its surface as eruptions can vary widely in style, scale, duration and frequency.

Prof. Claudia Romano
Guest Editor

Manuscript Submission Information

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Keywords

  • high-pressure
  • high-temperature
  • silicate melts
  • mineralogy
  • mineral physics
  • physical properties

Published Papers (2 papers)

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Research

Open AccessArticle
High-Temperature Mineral Phases Generated in Natural Clinkers by Spontaneous Combustion of Coal
Minerals 2019, 9(4), 213; https://doi.org/10.3390/min9040213
Received: 4 March 2019 / Revised: 26 March 2019 / Accepted: 29 March 2019 / Published: 1 April 2019
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Abstract
The aim of this study is to analyze natural clinkers (= calcined clays by coal combustion) from a lower Cretaceous coal outcrop in Ariño (Teruel, NE Spain) in order to describe mineral and textural transformations produced during the spontaneous combustion of coal. To [...] Read more.
The aim of this study is to analyze natural clinkers (= calcined clays by coal combustion) from a lower Cretaceous coal outcrop in Ariño (Teruel, NE Spain) in order to describe mineral and textural transformations produced during the spontaneous combustion of coal. To achieve this aim, samples were analyzed using X-ray diffraction and optical and electron microscopy. Spontaneous combustion resulted in the melting of the surrounding clays, with the generation of an Al–Si-rich vitreous phase. Subsequently, high-temperature phases crystallized from this vitreous phase. These new minerals are interesting due to their similarity with those formed during ceramic processes, used in the manufacture of stoneware and ceramic tiles, as well as in refractory ceramics, and with natural events such as metamorphic and igneous processes. The studied natural clinkers are composed of vitreous phase mullite, hematite, hercynite, cristobalite, quartz, pyroxenes, cordierite, gypsum, pyrite, and calcium oxides. A trend from hematite to hercynite composition indicates compositional variations at sample scale, which evidence d-spacing differences in hercynite and may be related to the Al and Fe content in hercynite depending on its texture. The mullite shows higher Si/Al ratio (1.21) than the theoretical composition (0.35), indicating that this mullite is more Si-rich. Three pyroxene-type compositions (diopside-type, ferrosilite-type, and a Ca–Al-rich pyroxene) were found. Both the mullite and the pyroxenes are nonstoichiometric. Full article
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Open AccessArticle
Electrical Conductivity of Fluorite and Fluorine Conduction
Minerals 2019, 9(2), 72; https://doi.org/10.3390/min9020072
Received: 8 December 2018 / Revised: 15 January 2019 / Accepted: 24 January 2019 / Published: 27 January 2019
Cited by 1 | PDF Full-text (2553 KB) | HTML Full-text | XML Full-text
Abstract
Fluorine is a species commonly present in many minerals in the Earth’s interior, with a concentration ranging from a few ppm to more than 10 wt. %. Recent experimental studies on fluorine-bearing silicate minerals have proposed that fluorine might be an important charge [...] Read more.
Fluorine is a species commonly present in many minerals in the Earth’s interior, with a concentration ranging from a few ppm to more than 10 wt. %. Recent experimental studies on fluorine-bearing silicate minerals have proposed that fluorine might be an important charge carrier for electrical conduction of Earth materials at elevated conditions, but the results are somewhat ambiguous. In this investigation, the electrical conductivity of gem-quality natural single crystal fluorite, a simple bi-elemental (Ca and F) mineral, has been determined at 1 GPa and 200–650 °C in two replication runs, by a Solartron-1260 Impedance/Gain Phase analyzer in an end-loaded piston-cylinder apparatus. The sample composition remained unchanged after the runs. The conductivity data are reproducible between different runs and between heating-cooling cycles of each run. The conductivity (σ) increases with increasing temperature, and can be described by the Arrhenius law, σ = 10^(5.34 ± 0.07)·exp[−(130 ± 1, kJ/mol)/(RT)], where R is the gas constant and T is the temperature. According to the equation, the conductivity reaches ~0.01 S/m at 650 °C. This elevated conductivity is strong evidence that fluorine is important in charge transport. The simple construction of this mineral indicates that the electrical conduction is dominated by fluoride (F). Therefore, fluorine is potentially an important charge carrier in influencing the electrical property of Fluorine-bearing Earth materials. Full article
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