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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: For example, in this paper, the ages of primary mantle minerals, metasomatic phases, and a range of mantle rock types from xenoliths in recent volcanics in northern Tanzania were obtained.
95 citations
TL;DR: In this paper, the authors examined samples from the Hanford Site at microscopic scale to determine the mode of uranium occurrence, and constructed a conceptual model for its emplacement, which was tested using a model of reactive diffusion at that scale.
94 citations
TL;DR: Raman spectroscopy has been used to study the molecular structure of a series of selected uranyl silicate minerals including uranophane, sklodowskite, cuproskloda, boltwoodite and kasolite as mentioned in this paper.
Abstract: Raman spectroscopy has been used to study the molecular structure of a series of selected uranyl silicate minerals including uranophane, sklodowskite, cuprosklodowskite, boltwoodite and kasolite. Raman spectra clearly show well resolved bands in the 750 to 800 cm-1 region and in the 950 to 1000 cm-1 region assigned to the ν1 modes of the (UO2)2+ units and to the (SiO4)4- tetrahedra. Sets of Raman bands in the 200 to 300 cm-1 region are assigned to ν2 δ (UO2)2+ and UO ligand vibrations. Multiple bands indicate the non-equivalence of the UO bonds and the lifting of the degeneracy of ν2 δ (UO2)2+ vibrations. The (SiO4)4- tetrahedral are characterized by bands in the 470 to 550 cm-1 and in the 390 to 420 cm-1 region. These bands are attributed to the ν4 and ν2 (SiO4)4- bending modes. The minerals show characteristic OH stretching bands in the 2900 to 3500 cm-1 and 3600 to 3700 cm-1 region ascribed to water stretching and SiOH stretching vibrations. The high wavenumber position of the δH2O bands indicate strong hydrogen bonding of water in these uranyl silicates. Bands in the 1400 to 1550 cm-1 region are attributed to δSiOH modes. The Raman spectroscopy of uranyl silicate minerals enabled separation of the bands attributed to distinct vibrational units. This enabled definitive assignment of the bands. The spectra are analysed in terms of the molecular structure of the minerals.
94 citations
TL;DR: This paper found that most of the nitrogen in igneous and sedimentary rocks is fixed ammonium ion held within the lattice structures of silicate minerals, where ammonium is held by primary primary minerals.
94 citations
TL;DR: In this paper, the solubility of H2O and CO2 in silicate melts at high pressures and temperatures was investigated and it was shown that the solusability of CO2 depends strongly on pressure and, compared to that of H 2O, depends only to a small extent on temperature.
Abstract: Available data on the solubility of H2O and CO2 in silicate melts at high pressures and temperatures reveal that (1) the solubility of H2O is several times greater than that of CO2 and (2) the solubility of H2O depends strongly on pressure and, compared to that of CO2, depends only to a small extent on temperature. It has been suggested that the species in silicate melts can be chosen so that the molar solubility of H2O may not depend on the bulk composition of the melt. The solubility of CO2, on the other hand, varies significantly with pressure, temperature, and bulk composition of the melt. Solution of volatiles at high pressure affects the structure of the silicate melts. Water depolymerizes the melt, the result being lowered viscosity. The same depolymerization is manifested in the enhanced stability of silicate minerals on the liquidus, which are less polymerized than the minerals precipitating from the same melt composition at the same pressure under volatile-free conditions. Carbon dioxide, on the other hand, enhances polymerization of the melt, the result being increased viscosity and increased stability of liquidus minerals which are more polymerized than those that would precipitate under volatile-free conditions. Because of the large difference in the solubilities of CO2 and H2O in silicate melts, partial melting of an (H2O + CO2)-bearing mantle results in enrichment of H2O in the liquid, whereas the residual mantle becomes, enriched in CO2. At P ≲ 20 at the CO2 may be retained in a vapor phase. At higher pressures, carbonate is likely to be the stable phase. Therefore it would be expected that as the result of partial melting throughout geological history the upper mantle would be heterogeneous with respect to vapor components.
94 citations