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Silicate minerals
About: Silicate minerals is a research topic. Over the lifetime, 1794 publications have been published within this topic receiving 67064 citations.
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TL;DR: In this article, atom probe tomography (APT) and energy-filtered transmission electron microscopy (EFTEM) were applied to a borosilicate glass sample of nuclear interest altered for 25.75 years at 90°C in a confined granitic medium in order to better understand the rate-limiting mechanisms under conditions representative of a deep geological repository for vitrified radioactive waste.
116 citations
TL;DR: In this paper, the relative partitioning behavior of REE in high-silica rhyolites is dominated by crystal-chemical controls and not by liquid structural effects, and the true REE partition coefficients of La Primavera and Bishop Tuff pyroxenes obtained by microprobe are only slightly higher than they are in lower silica rhymes, and are not as variable as previously thought.
114 citations
TL;DR: In this article, the authors investigated the characteristics of aqueous dissolution of three complex silicate glasses (rhyolitic, basaltic, and simulated nuclear-waste glass) by analytical techniques based on energetic ion beams, which provided depth profiles of various elements including hydrogen, on the altered surface of the materials.
114 citations
TL;DR: In this article, a network of electrical elements is presented for use in interpreting impedance spectra and conductive paths in hot or cold, wet or dry, minerals and rocks at any pressure.
Abstract: Abstract Impedance spectroscopy helps distinguish the contributions that grain interiors and grain boundaries make to electrical resistance of silicate minerals and rocks. The technique also distinguishes the low-frequency response due to the presence of instrument electrodes. We measured olivine, orthopyroxene, clinopyroxenes, and both natural and synthetic clinopyroxenite. Measurements were made at 1 bar, from 750 to 1150 °C, and over a frequency range from < 10-4 to > 106 Hz; some measurements were also made at 300-850 °C and 10-20 kbar. The grain-interior response lies at highest frequency, the sample- electrode response at low frequencies, and the grain boundary response at mid-frequencies. Grain interiors show as semicircular impedance arcs when plotted on the complex plane, and sample-electrode responses of hot single crystals and of hot dry rocks are exhibited as depressed arcs. In comparison, monofrequency measurements contain no information to identify the source of the response; at 1 kHz they detect only the resistance sum of grain interiors and grain boundaries and at low frequency (≤ 1 Hz) are likely to sense all three components. The major experimental problem is to find electrodes that make good contact with the sample and that are stable with time. The effect of pressure (10 kbar, 300-800 °C) is to diminish the resistance associated with grain boundaries and the sample-electrode interface, in the laboratory and presumably in nature. Monofrequency measurements at 1 bar may underestimate the conductivity of rocks at similar temperature but higher pressure. A network of electrical elements is presented for use in interpreting impedance spectra and conductive paths in hot or cold, wet or dry, minerals and rocks at any pressure. In dry rocks, a series network path predominates; in wet rocks, aqueous pore fluid and crystals both conduct. Finite resistance across the sample-electrode interface is evidence that electronic charge carriers are present at the surface, and presumably within, the silicate minerals and rocks measured.
113 citations
TL;DR: In this paper, the photoelectron binding and Auger electron kinetic energies of Si, O and tetrahedrally coordinated Al ions in the silicate framework suggest that negative charge on the framework is delocalized over these ions.
Abstract: X-ray photoelectron and X-ray-induced Auger electron spectra of silicate minerals have been measured. The systematic shifts of the photoelectron binding energies of Si, O and tetrahedrally coordinated Al ions in the silicate framework suggest that the negative charge on the framework is delocalized over these ions. On the other hand, it is deduced from the photoelectron binding and Auger electron kinetic energies that the octahedrally coordinated Al and Mg ions in the silicate mineral are not subject to a strong effect from the negative charge on the silicate framework. A comparison of the Na 1s binding and KL23L23 Auger kinetic energies of the exchangeable Na ion in the silicate mineral with those of sodium halides reveals that the bonding state of the exchangeable Na ion is comparable to those of Na ions in sodium chloride and fluoride.
113 citations