Topic
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, high-resolution proton magic-angle NMR spectra of minerals containing stoichiometric hydroxyl groups as the only hydrous species are obtained, provided that the hydrogen density in the sample is less than about 15 atoms/nm^3.
Abstract: Proton magic-angle spinning (MAS) NMR at 200 and 500 MHz and at high spinning speeds (ca. 8 kHz) has been used to characterize hydrous species, both stoichiometric and nonstoichiometric, in a variety of minerals. High-resolution
^1H MAS-NMR spectra of minerals containing stoichiometric hydroxyl groups as the only hydrous species are obtainable provided that the hydrogen density in the sample is less than about 15 atoms/nm^3. Structurally isolated water molecules in analcite, NaAlSi_2O_6•H_2O, and gypsum, CaSO_4•2H_2O, yield characteristic ^1H MAS-NMR spectra with numerous spinning sidebands extending over a range of about 100 kHz, reflecting the strong, largely inhomogeneous character of the homonuclear dipolar coupling. The field dependence of both line widths and spinning sideband patterns provides evidence about the nature of the
broadening interactions. Lawsonite and hemimorphite, minerals containing stoichiometric amounts of both OH and H_2O groups, yield spectra with numerous intense spinning sidebands; strong dipolar interactions preclude discrimination of OH and H_2O.
Nonstoichiometric hydrogen in nominally anhydrous minerals (feldspars, nepheline, quartz, and grossular garnet) is found to occur in a variety of forms: mobile H_2O in fluid inclusions, anisotropically constrained, isolated H_2O molecules, and clustered species consistent with H_4O_4^(4-) groups in a hydrogarnet substitution.
183 citations
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TL;DR: In this article, laser ablation microprobe analyses of clinopyroxenes equilibrated with carbonatite melt at 20-22 kbar and 1050-1100°C are used to calculate partition coefficients for an extensive suite of trace elements.
183 citations
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TL;DR: Local saturation is an attractive mechanism for enhancing fractionation during crystallization differentiation as discussed by the authors, but it is not a process that applies to all cases and some inconsistencies remain in local saturation origin for accessory phases that cannot be evaluated without additional information.
183 citations
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TL;DR: In the presence of dissolved O2, as would be the case in most weathering solutions, dissolution of bronzite and fayalite results in the formation of two surface layers whose compositions were deduced by measurements of XPS binding energies as mentioned in this paper.
182 citations
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TL;DR: In this paper, a total of 87 groundwater samples were collected from bore wells for two different seasons, viz., Pre monsoon and Post monsoon, and analyzed for major cations and anions.
181 citations