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Geochimica et Cosmochimica Acta, 1973
Phase equilibria determined in high-pressure studies of the systems Mg2Si2O6-CaMgSi2O6 and MgSiO3-Mg3Al2Si3O12 can be used to estimate equilibration conditions of ultramafic rocks containing the assemblage enstatite + diopside + garnet. Garnet lherzolite nodules from kimberlites in northern Lesotho appear to have equilibrated in the upper mantle at ...
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Phase equilibria determined in high-pressure studies of the systems Mg2Si2O6-CaMgSi2O6 and MgSiO3-Mg3Al2Si3O12 can be used to estimate equilibration conditions of ultramafic rocks containing the assemblage enstatite + diopside + garnet. Garnet lherzolite nodules from kimberlites in northern Lesotho appear to have equilibrated in the upper mantle at ...
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Lithos, 1968
Meteoritic pyroxenes, while analogous in many respects to those from terrestrial rocks, show some unique features. Among these are the presence of minerals close to MgSiO3 in composition, the common occurence of minerals belonging to the clinoenstatite-clinohypersthene series, the rarity of calcium-rich and aluminium-rich pyroxenes, and the absence of ...
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Meteoritic pyroxenes, while analogous in many respects to those from terrestrial rocks, show some unique features. Among these are the presence of minerals close to MgSiO3 in composition, the common occurence of minerals belonging to the clinoenstatite-clinohypersthene series, the rarity of calcium-rich and aluminium-rich pyroxenes, and the absence of ...
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Geochimica et Cosmochimica Acta, 1979
A thermodynamic analysis of pyroxene-melt equilibria is performed through use of a literature survey of analyses of high-Ca pyroxene and coexisting silicate melt pairs and analyses of low-Ca pyroxene silicate melt pairs. Reference is made to a modified version of a model developed by Bottinga and Weill (1972) which more successfully accounts for ...
Roger L. Nielsen, Michael J. Drake
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A thermodynamic analysis of pyroxene-melt equilibria is performed through use of a literature survey of analyses of high-Ca pyroxene and coexisting silicate melt pairs and analyses of low-Ca pyroxene silicate melt pairs. Reference is made to a modified version of a model developed by Bottinga and Weill (1972) which more successfully accounts for ...
Roger L. Nielsen, Michael J. Drake
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Elasticity of pyroxene-garnet and pyroxene-ilmenite phase transformations in germanates
Physics of the Earth and Planetary Interiors, 1974Abstract Ultrasonic data for the velocities of the low- and high-pressure polymorphs of germanate compounds undergoing the pyroxene-garnet (CaGeO 3 , CdGeO 3 ) and pyroxene-ilmenite (MgGeO 3 , MnGeO 3 ) phase transformations have been determined as a function of pressure to 7.5 kbar at room temperature for polycrystalline specimens hot-pressed at ...
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Journal of the Geological Society, 1978
THE PAPERS PRESENTED can be divided into two broad subject areas: the study of pyroxenes in plutonic rocks as a means of tracing the history of magma input and crystallization within a magma chamber; and the study of relict pyroxenes in altered volcanic rocks as a means of 'seeing through' the effects of chemical alteration and thus of identifying any ...
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THE PAPERS PRESENTED can be divided into two broad subject areas: the study of pyroxenes in plutonic rocks as a means of tracing the history of magma input and crystallization within a magma chamber; and the study of relict pyroxenes in altered volcanic rocks as a means of 'seeing through' the effects of chemical alteration and thus of identifying any ...
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The thermodynamics of pyroxene geotherms
Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences, 1978Abstract Correctly formulated thermodynamics provides the only reliable means of applying the results of mineral equilibria experiments to the calculation of the temperature and pressure of formation of mineral assemblages. The problems of formulating geothermometers and geobarometers are considered with particular reference to ...
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Disordered pyroxene in chondrites
Geochimica et Cosmochimica Acta, 1968Abstract A summary of the results on the occurrence of disordered pyroxene in chondrites is presented. Disordered orthopyroxene has been found in 5 of 15 enstatite and 20 of 51 ordinary chondrites. X-ray diffraction studies of Bamle enstatite deformed under shearing stress conditions (29–34 kbars at 500–900°C) and 150 and 450 kbars explosive shock ...
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Single-pyroxene thermobarometry
Tectonophysics, 1980Abstract Enstatites in peridotites from the Vourinos ophiolites, Greece, have exceptionally high Cr/Al ratios, though the pyroxenes are in equilibrium with picotite. Phase-chemistry data yield new empirical relations for the critical effect of Cr on Al solubility, in full agreement with local Cr/Al ratio variations observed in some massifs. These new
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