Results 171 to 180 of about 28,093 (233)
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Annual Review of Earth and Planetary Sciences, 1986
Andesites are most commonly found at convergent plate margins, where they constitute part of the erupted lavas of volcanic arcs that parallel subduction zones. They are also found less frequently as eruptive products in divergent plate boundaries, in association with midocean ridge basaltic volcanism.
Timothy L. Grove, Rosamond J. Kinzler
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Andesites are most commonly found at convergent plate margins, where they constitute part of the erupted lavas of volcanic arcs that parallel subduction zones. They are also found less frequently as eruptive products in divergent plate boundaries, in association with midocean ridge basaltic volcanism.
Timothy L. Grove, Rosamond J. Kinzler
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Petrogenesis of oceanic andesites
Journal of Geophysical Research: Solid Earth, 1981The andesites and cogenetic rocks of the intraoceanic island arc systems vary in silica content from 49–50% SiO2 to about 76% SiO2. The most primitive compositions, having contents of about 50% SiO2, are the basaltic andesites, which are primary compositions generated by partial melting of the uppermost section of the subducted oceanic crust.
Sven Maaløe, Tom Svane Petersen
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Geochimica et Cosmochimica Acta, 2003
Abstract The recent discovery of two new angrites, Sahara 99555 and D'Orbigny, has revived interest in this small group of achondrites. We measured trace element abundances in the individual minerals of these two angrites and compared them with the three Antarctic angrites, LEW 86010, LEW 87051 and Asuka 881371.
Christine Floss +4 more
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Abstract The recent discovery of two new angrites, Sahara 99555 and D'Orbigny, has revived interest in this small group of achondrites. We measured trace element abundances in the individual minerals of these two angrites and compared them with the three Antarctic angrites, LEW 86010, LEW 87051 and Asuka 881371.
Christine Floss +4 more
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1991
The development of realistic hypotheses for the petrogenesis of potassic rocks has been hindered, until recently, by the tendency of petrologists to consider all leucite-bearing K-rich rocks as being related. Sufficient geological, geochemical, and mineralogical evidence (see Chapter 2) has now accumulated to show that this assumption is not correct ...
Roger H. Mitchell, Steven C. Bergman
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The development of realistic hypotheses for the petrogenesis of potassic rocks has been hindered, until recently, by the tendency of petrologists to consider all leucite-bearing K-rich rocks as being related. Sufficient geological, geochemical, and mineralogical evidence (see Chapter 2) has now accumulated to show that this assumption is not correct ...
Roger H. Mitchell, Steven C. Bergman
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Nature, 1957
L'Evolution de la Lithosphere Par Prof. Henri Termier et Dr.Genevieve Termier. 1 : Petrogenese. (Traite de Geologie.) Pp. iv + 654 + 54 plates. (Paris: Masson et Cie., 1956.) Broche, 8,000 francs; Cartonne toile, 8,800 francs.
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L'Evolution de la Lithosphere Par Prof. Henri Termier et Dr.Genevieve Termier. 1 : Petrogenese. (Traite de Geologie.) Pp. iv + 654 + 54 plates. (Paris: Masson et Cie., 1956.) Broche, 8,000 francs; Cartonne toile, 8,800 francs.
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Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences, 1977
Melting experiments in vacuum at Fe-saturation for high-Ti basalt compositions 70215 and 15318 Red Glass, and low-Ti basalt composition 15555-15016, have defined equilibrium crystallization sequences and the liquid-lines-of-descent, and show that much of the chemical variety in the natural samples is due to near-surface fractionation processes. However,
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Melting experiments in vacuum at Fe-saturation for high-Ti basalt compositions 70215 and 15318 Red Glass, and low-Ti basalt composition 15555-15016, have defined equilibrium crystallization sequences and the liquid-lines-of-descent, and show that much of the chemical variety in the natural samples is due to near-surface fractionation processes. However,
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Clays and clay minerals (National Conference on Clays and Clay Minerals), 1963
AbstractThe formation of typical bentonites occurs in two stages. The first stage comprises the development, transportation, and deposition of the volcanic ash, which determines the geometry and structure of the bentonite rock and influences the alteration of the ash during the second stage. The second stage encompasses the alteration of volcanic glass
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AbstractThe formation of typical bentonites occurs in two stages. The first stage comprises the development, transportation, and deposition of the volcanic ash, which determines the geometry and structure of the bentonite rock and influences the alteration of the ash during the second stage. The second stage encompasses the alteration of volcanic glass
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Petrogenesis of ophiolitic chromitite
Geological Society, London, Special Publications, 1993Abstract Chromite deposits comprise an integral part of the mantle sequences observed within many ophiolite complexes; in particular, those where a harzburgite is the dominant mantle sequence lithology. The chromite segregations are invariably contained within a dunite envelope and show a wide variety of ore textures, some of which are ...
Stephen Roberts, Christopher Neary
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Nature, 1939
THIS memoir is probably the most instructive contribution to modern petrology since Brogger published his description of the Oslo area (1931)1. It describes the north-eastern (British) part of the Birunga lava-field—a region of Tertiary and Recent vulcanism which produced ‘alkali’ lavas of basic to intermediate composition. The field extends along, and
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THIS memoir is probably the most instructive contribution to modern petrology since Brogger published his description of the Oslo area (1931)1. It describes the north-eastern (British) part of the Birunga lava-field—a region of Tertiary and Recent vulcanism which produced ‘alkali’ lavas of basic to intermediate composition. The field extends along, and
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Oxidation in High Temperature Petrogenesis
American Journal of Science, 1961A study has been made of a variety of metamorphic and magmatic rocks to determine how oxidative processes are reflected in their mineral assemblages. In this study particular attention is paid to solid solutions. Field and experimental evidence agree with theory as to the responses of ferromagnesian solid solution to compositional changes of the ...
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