Results 191 to 200 of about 278,731 (238)

Time differences within a calc-alkaline association

Contributions to Mineralogy and Petrology, 1972
A Strontium isotope study of a high-K diorite complex at Yeoval, N.S.W. (Australia) points to clear time differences (40 m.y.) between the diorite suite (gabbro-diorite-grano-diorite) and surrounding granites. Such a time interval, in association with other data, precludes a genetic relationship between these rock groups whereas the data support a ...
Gulson, B. L., Bofinger, V. M.
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Origin of Lead in Andean Calc-Alkaline Lavas, Southern Peru

Science, 1980
Lead isotope data from Quaternary andesitic lavas of the Arequipa and Barroso groups of southern Peru and from regional Precambrian granulitic gneisses reveal a lead component in the lavas from the gneisses. The lava leads can be accounted for by two-component mixtures of lead from mantle and lower crustal sources, although the mixing process need not ...
G R, Tilton, B A, Barreiro
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Radioactivity and geochemistry of calc-alkaline neovolcanites of the West Carpathians

Studia Geophysica et Geodaetica, 1989
The distribution of radioactive elements(Th, U, K) and selected trace elements(Rb, Sr, Ba, Y, Zr, V, Cr, Ni) in a set of 29 volcanic rocks of the West Carpathians was studied. The rock types follow the typical calc-alkaline sequence from basaltic andesites to rhyolites with average contents of SiO2, K2O, Th, U, Rb, Ba and Zr increasing, and with ...
Vladimír Kropáček, Věra Vaňková
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Physicochemical model for the crystallization of rocks of the calc-alkaline series

Geochemistry International, 2012
The Al-rich region of the CaO-MgO-Al2O3-SiO2 system was experimentally studied at pressures of 1.0–2.8 GPa and temperatures of 1300–1535°C. The slopes of the lines of the monovariant reactions An + Sp = Cpx + Cor + (Ga) and L = Cpx + Ga + Cor + Sp and the compositions of the phases involved in these reactions are determined. The results are utilized in
N. V. Surkov, Yu. G. Gartvich
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Effects of volatiles on mixing in calc-alkaline magma systems

Nature, 1982
The intimate mixing between different magmas of disparate densities, characteristic of some calc-alkaline magma systems, is explained by a new mechanism involving the emplacement of a layer of wet undersaturated mafic magma at the base of a magma chamber containing more differentiated magma.
Herbert E. Huppert, R. Stephen J. Sparks, J. Stewart Turner   +2 more
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Calc-alkaline nuees ardentes: A new classification

Journal of Geodynamics, 1985
Several nuees ardentes deposits, all in a subduction context (Lesser Antilles, Central America, Washington-U.S.A., Kamchatka, Indonesia) are compared. All these tephra are andesitic to dacitic and have a typical calc-alkaline minerology. A new classification is proposed on the basis of glass-grain morphology and grain-size analyses of the deposits.
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Vesiculation processes in a water-rich calc-alkaline obsidian

Earth and Planetary Science Letters, 1997
The effect of temperature and viscosity on the kinetics of bubble growth was measured for a natural water-rich rhyolite melt. The change in volume of a natural crystal-poor calc-alkaline rhyolitic obsidian with an initial water content of ≈ 1.8 wt% H2O was determined in the temperature interval 520–624°C.
STEVENSON R. J, BAGDASSAROV, N, ROMANO, Claudia   +2 more
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Petrography and geochemistry of Plio-Quaternary calc-alkaline volcanoes of Southwestern Colombia

Journal of South American Earth Sciences, 1996
Abstract The six studied southwestern Colombian Plio-Quaternary volcanoes (Purace, Dona Juana, Galeras, Azufral, Cumbal and Chiles) are located in the central part of the Northern Volcanic Zone (NVZ) of the Andes. The lavas are predominantly andesites and dacites, with lesser amount of basalt, and range 52% to 70% SiO2.
Delaloye, Michel, Droux, Alain
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Trace element evidence for plagioclase recycling in calc-alkaline magmas

Earth and Planetary Science Letters, 1991
Abstract Trace element zoning in plutonic plagioclase feldspars from the Val Fredda Complex, southern Adamello Massif, Italy has been measured using secondary-ion mass spectrometry (SIMS). The studied samples range from hornblende-gabbro through diorite to granitoid with an overall range in plagioclase composition from An96 to An15.
Blundy, JD, Shimizu, N
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Magma mingling, zoning and emplacement in calc-alkaline granitoid plutons

Tectonophysics, 1989
The study of some Carboniferous orogenic granitoid plutons from northern Sardinia reveals the close relationship between their composition and the abundance of the enclosed mafic magmatic inclusions. The latter represent blobs of mingled basaltic magma. Most of the plutons are normally zoned with their felsic character increasing towards the core. This
M.J Zorpi, C Coulon, J.B Orsini, C Cocirta   +3 more
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