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  • 1
    Electronic Resource
    Electronic Resource
    Incremental growth of a large volume, chemically zoned magma body: a study of the tephra sequence beneath the Rainier Mesa ash flow sheet of the Timber Mountain Tuff (1994)
    Springer
    Bulletin of volcanology 56 (1994), S. 377-385 
    Details
    ISSN: 1432-0819
    Keywords: Zoned magma body ; Chemical variation ash-flow sheets ; Tephra sequence ; Differentiation time constraints ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Rainier Mesa ash-flow is a large (1200 km3), 11.6 My old, chemically zoned unit that ranges in composition from 55 to 76% SiO2 — one of the largest chemical ranges ever observed in a large volume ash-flow sheet. Two chemical trends occur in this sheet, a low silica (55–66% SiO2) and a high silica (〉66% SiO2) trend. Ninety per cent of the Rainier Mesa sheet occurs in the high silica trend. Immediately beneath the Rainier Mesa sheet is a thick tephra sequence. The chemical variation of this sequence is nearly equivalent to the high silica portion of the Rainier Mesa ash-flow sheet (about 66–78% SiO2). Throughout the tephra sequence numerous small ash-flow layers occur, and each ash-flow layer is chemically zoned from more evolved at the base to less evolved at the top. This is consistent with having been erupted from a zoned magma body. The lowest silica tephra units are at the base of the sequence and the highest silica units are at the top — that is, the large-scale chemical trend of the entire sequence is opposite to that of the individual ash-flow layers. These ash-flow layers are of very small volume. The tephra sequence provides a unique record of the incremental development of the zoned, high silica portion of the Rainier Mesa magma body.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326463
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  • 2
    Electronic Resource
    Electronic Resource
    Incremental growth of a large volume, chemically zoned magma body: a study of the tephra sequence beneath the Rainier Mesa ash flow sheet of the Timber Mountain Tuff (1994)
    Springer
    Bulletin of volcanology 56 (1994), S. 377-385 
    Details
    ISSN: 1432-0819
    Keywords: Key wordsZoned magma body ; Chemical variation ; ash-flow sheets ; Tephra sequence ; Differentiation ; time constraints ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Rainier Mesa ash-flow is a large (1200 km3), 11.6 My old, chemically zoned unit that ranges in composition from 55 to 76% SiO2– one of the largest chemical ranges ever observed in a large volume ash-flow sheet. Two chemical trends occur in this sheet, a low silica (55–66% SiO2) and a high silica (〉66% SiO2) trend. Ninety per cent of the Rainier Mesa sheet occurs in the high silica trend. Immediately beneath the Rainier Mesa sheet is a thick tephra sequence. The chemical variation of this sequence is nearly equivalent to the high silica portion of the Rainier Mesa ash-flow sheet (about 66–78% SiO2). Throughout the tephra sequence numerous small ash-flow layers occur, and each ash-flow layer is chemically zoned from more evolved at the base to less evolved at the top. This is consistent with having been erupted from a zoned magma body. The lowest silica tephra units are at the base of the sequence and the highest silica units are at the top – that is, the large-scale chemical trend of the entire sequence is opposite to that of the individual ash-flow layers. These ash-flow layers are of very small volume. The tephra sequence provides a unique record of the incremental development of the zoned, high silica portion of the Rainier Mesa magma body.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326463
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  • 3
    Electronic Resource
    Electronic Resource
    [ohne Titel] (1979)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 26 (1979), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: RESUME. L'individualisation de 2 spores bicellulaires à partir d'un měme pansporoblaste caractérise la sporulation du parasite de l'Amphipode Orchestia gammarellus (Pallas) précédemment décrit sous le nom de Marteilia sp. Cette sporulation le distingue des espèces du měme genre parasite d'Huǐtres qui sont toutes caractérisées par la production de spores tricellulaires. Les conditions semblables dans lesquelles les pansporoblastes paraissent se differencier à partir d'une cellule souche dans laquelle ils poursuivent leur évolution vers la sporogenèse ainsi que divers caractères cytologiques communs, nous incitent à maintenir tous ces parasites dans une měme famille mais à placer celui de l'Amphipode dans un genre différent. Nous proposons de le nommer Paramarteilia orchestiae gen. n., sp. n.Ces parasites ne peuvent ětre maintenus dans les Protozoaires en raison de leur évolution vers la pluricellularité et de l'individualisation de ces éléments somatiques que représentent la cellule souche primaire, les pansporoblastes et cellules sporales (à l'exception des sporoplasmes). Il semble logique de les inclure dans l'embranchement des Myxozoaires créé par Grassé pour les Myxosporidies et Actinomyxidies qui différencient également des spores pluricellulaires et des éléments somatiques. Les centrioles à 9 singlets de P. orchestiae ainsi que les cellules primaires uninucléées, quel que soit le nombre de pansporoblastes qu'elles contiennent, peuvent ětre considérés comme des caractères résiduels d'Unicellulaires.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1979.tb04642.x
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  • 4
    Electronic Resource
    Electronic Resource
    A model for the origin of the alkaline complexes of Egypt (1981)
    [s.l.] : Nature Publishing Group
    Nature 291 (1981), S. 571-574 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The major structural features of the Nubian Shield were formed during the Pan-African compression-accretion process (1,000-550 Myr BP)9"11. This NE-SW oblique compression (see Fig. 4) produced both NE-SW and NW-SE zones of weakness9'12. Most of the alkaline complexes of Egypt are associated with ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/291571a0
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  • 5
    Electronic Resource
    Electronic Resource
    Feldspar geothermometry of the Hell Canyon Pluton, Boulder Batholith, Montana (1979)
    Springer
    Contributions to mineralogy and petrology 71 (1979), S. 151-155 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The bulk compositions of the groundmass alkali feldspar from the Hell Canyon Pluton is 0.146mole% albite. The composition of the outermost zone of the oscillatory zoned plagioclase is 0.686 mole% albite, whereas the most calcic cores have a composition of 0.43 mole% albite. The structural state of the alkali feldspar is near orthoclase. Both composition of coexisting feldspars and structural state of the alkali feldspar are nearly constant throughout the pluton. Exsolved albite in the alkali feldspar have a composition of 0.965 mole% albite and the orthoclase host has a composition of 0.032 mole%. Singe crystal X-ray studies indicate that the albite intergrowths are coherent with the host. Equilibrium temperatures derived from the coexisting feldspar average 554 ° C; about 150 ° C, too low for the minimum solidus temperatures for reasonable emplacement pressures (2 kb). If this minimum solidus temperature is assumed, then the alkali feldspar has lost about 0.15 mole% albite. This loss was most likely caused by hydrothermal solutions associated with the crystallizing magma and equilibrated at about 550 ° C. However, based on the coherent albite intergrowths and the orthoclase structure state it can be inferred that the system was relatively free of volatiles below 500 ° C. Final equilibirium between orthoclase host and albite intergrowths occurred at about 311 ° C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00375431
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  • 6
    Electronic Resource
    Electronic Resource
    Magma mixing: the Marsco suite, Isle of Skye, Scotland (1984)
    Springer
    Contributions to mineralogy and petrology 87 (1984), S. 231-241 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Magma mixing has been proposed as a major mechanism for the origin of a wide variety of rock suites. In mid-ocean basalts there are few obstacles to mixing because of the similarities in chemical and physical properties of the proposed end-members. However, in calc-alkaline rocks the proposed end-members have disparate properties and these present obstacles to mixing. The Marsco suite is ideal to evaluate the process of magma mixing because it is considered to be a classic example of magma mixing of diverse magma types and because compositionally diverse, coexisting liquids were present throughout the area. The results of this study are that the chemical data for the Marsco suite fit a mixing model remarkably well and that the mixing did not take place at the present level of exposure. The Marsco mixed suite is similar to the experiments of Kouchi and Sunagawa (1982, 1983) in which mixing was produced by forced convection. Based on the Marsco suite, a similar occurrence in Ardnamurchan, and the experimental data, we conclude that mixing was dominated by mechanical mixing and this mechanical mixing was efficient enough to allow diffusional processes to homogenize the liquids. It is postulated that injection of mafic magma into the base of a silicic magma system leads to mixing and mobilization of the system. The mechanical interaction that produces the mixing also leads to disruption of the system. Liquids involved with the mixing process at depth are mobilized and coexist at shallower levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373056
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  • 7
    Electronic Resource
    Electronic Resource
    The origin of the acidic and basic rocks of the Tichka Massif, Morocco, based on rare earth elements (1980)
    Springer
    Contributions to mineralogy and petrology 75 (1980), S. 89-95 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Tichka Massif is one of many late-Paleozoic massifs emplaced in northwestern Africa. It consists of granitic pods surrounded by a complex assemblage of dioritic and gabbroic rocks. Previous workers have suggested an independent origin for the granitic and gabbroic rocks and this study evaluates this suggestion using REE data. The Ce/Yb ratio versus Ce plot for the gabbro shows a large Ce/Yb variation for small changes in Ce, whereas the granites show a linear increase of Ce/Yb with Ce. In the granites, the samples with the highest Ce/Yb ratio have the lowest SiO2, whereas in the gabbros the Ce/Yb ratio is lowest in the low SiO2 rocks. The diorites show a tightly clustered pattern. Based on the REE data the granite-diorite-gabbro sequence cannot be related by fractional crystallization. Partial melting of a garnet bearing mantle is consistent with the gabbroic trends. Partial melting of a crustal source with small amounts of apatite and abundant hornblende can produce the granitic rocks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371892
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  • 8
    Electronic Resource
    Electronic Resource
    Albite-rich domains in potash feldspar (1970)
    Springer
    Contributions to mineralogy and petrology 25 (1970), S. 138-143 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Detection of sodium-rich areas in orthoclase by electron microprobe analyses supports a theory for perthite formation that involves a preexsolution stage with sodium atoms clustering to form albite domains coherent with the overall lattice. Orthoclase with a heterogeneous matrix, ranging in composition from one up to 14 weight percent albite, and ranging in size from 2 to 10 microns are present in a hypabyssal nepheline syenite from Beemerville, New Jersey, U.S.A. These become unstable at relatively low concentrations of albite (less than 15 weight percent albite) and exsolve forming incoherent albite grains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389782
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  • 9
    Electronic Resource
    Electronic Resource
    Distribution of Ti and P in oceanic basalts as a test of origin (1974)
    Springer
    Contributions to mineralogy and petrology 43 (1974), S. 307-316 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract A model is proposed to explain the distribution of titanium and phosphorus in oceanic basalts. This model is based on, the existence of titanium and phosphorus as primary components of specific mineral phases, the use of volumetric considerations to predict the stabilities of these phases and the existence of water as OH− in the mantle. If this model is correct then the distribution of titanium and phosphorus and their ratio may be used to test models for the origin of oceanic basalts. The amount of titanium and/or phosphorus is dependent on (in order of importance) the percent water in the original melt, amount of fractionation of silicate phases, and the depth. The ratio is largely dependent only on depth of partial melting, provided titanium and phosphorus are not depleted in the mantle by partial melting. A χ 2 analysis of the frequency distributions of these elements and their ratio is performed in order to test several models for the origin of basalts. From this analysis it is concluded that partial melting is the primary process for the generation of basalts but the degree of partial melting is relatively small and that the alkalinity of basalts increases with depth of partial melting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373486
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  • 10
    Electronic Resource
    Electronic Resource
    Magma mixing in the acidic-basic complex of Ardnamurchan: Implications on the evolution of shallow magma chambers (1982)
    Springer
    Contributions to mineralogy and petrology 79 (1982), S. 411-423 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Ardnamurchan net-veined complex consists of three rock types: a porphyritic mafic rock, an aphyric intermediate rock and a silicic rock. Pillows of mafic and intermediate rock are included in the silicic rock and contain crenulated and some chilled margins. Liquid-liquid relationships are inferred for these three magmas. The trace element data, using ratio-ratio plots, are consistent with magma mixing being the dominant process and are inconsistent with any process that is dominated by crystal fractionation or melting. The major element data, using multiple linear regression techniques, are consistent with magma mixing of high-silica silicic magma and primitive mafic magma, along with about 35 percent crystal fractionation to form the intermediate rock type. All of the data taken together are consistent with a magma mixing model with some fractionation to produce the variation observed. The simplest model is that a fractionating basaltic magma comes into contact with a silicic magma and limited mixing produces the intermediate magma. This net-veined complex may be the only evidence available for interaction of mafic and silicic melts that occurred in the Ardnamurchan high-level magma chamber before the silicic magma was lost to eruptive and surface processes. In general the chemical and field relationships are consistent with Smith's model for the evolution of high-level, magma chambers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01132071
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