Mid-Pleistocene lavas from the Seguam volcanic center, central Aleutian arc: closed-system fractional crystallization of a basalt to rhyodacite eruptive suite

1992 ◽  
Vol 110 (1) ◽  
pp. 87-112 ◽  
Author(s):  
Bradley S. Singer ◽  
James D. Myers ◽  
Carol D. Frost
Keyword(s):  
Fractional Crystallization ◽  
Closed System ◽  
Volcanic Center ◽  
Aleutian Arc

Emmons Lake Volcanic Center, Alaska Peninsula: source of the Late Wisconsin Dawson tephra, Yukon Territory, Canada

2003 ◽  
Vol 40 (7) ◽  
pp. 925-936 ◽  
Author(s):  
Margaret T Mangan ◽  
Christopher F Waythomas ◽  
Thomas P Miller ◽  
Frank A Trusdell
Keyword(s):  
Compositional Data ◽  
Late Quaternary ◽  
Yukon Territory ◽  
Volcanic Center ◽  
Pyroclastic Deposits ◽  
Alaska Peninsula ◽  
Aleutian Arc ◽  
Pumice Flow ◽  
North And South ◽  
The Bering Sea

The Emmons Lake Volcanic Center on the Alaska Peninsula of southwestern Alaska is the site of at least two rhyolitic caldera-forming eruptions (C1 and C2) of late Quaternary age that are possibly the largest of the numerous caldera-forming eruptions known in the Aleutian arc. The deposits produced by these eruptions are widespread (eruptive volumes of >50 km3 each), and their association with Quaternary glacial and eolian deposits on the Alaska Peninsula and elsewhere in Alaska and northwestern Canada enhances the likelihood of establishing geochronological control on Quaternary stratigraphic records in this region. The pyroclastic deposits associated with the second caldera-forming eruption (C2) consist of loose, granular, airfall and pumice-flow deposits that extend for tens of kilometres beyond Emmons Lake caldera, reaching both the Bering Sea and Pacific Ocean coastlines north and south of the caldera. Geochronological and compositional data on C2 deposits indicate a correlation with the Dawson tephra, a 24 000 14C BP (27 000 calibrated years BP), widespread bed of silicic ash found in loess deposits in west-central Yukon Territory, Canada. The correlation clearly establishes the Dawson tephra as the time-stratigraphic marker of the last glacial maximum.

Etude geochimique des elements en traces dans les series de roches volcaniques du rift d'Asal; identification et analyse des processus d'accretion

1980 ◽  
Vol S7-XXII (6) ◽  
pp. 851-861 ◽  
Author(s):  
J. L. Joron ◽  
M. Treuil ◽  
H. Jaffrezic ◽  
B. Villemant
Keyword(s):  
Partial Melting ◽  
Fractional Crystallization ◽  
Closed System ◽  
Mantle Source ◽  
Crystallization Process ◽  
Tectonic Activity ◽  
Dynamic Evolution ◽  
Mantle Material ◽  
Spreading Rates ◽  
Fractional Crystallization Process

Abstract Study of samples of the main volcanic units of the Afar rift, from margins to late axial series, have yielded the following conclusions: 1) the magmatic liquids are strongly differentiated by a fractional crystallization process in shallow chambers, the evolution of which is limited by injection of new primary liquids as shown in the latest axial series; 2) primary liquids are generated by melting of a homogeneous mantle source, a process whereby successive partial melting in a closed system is stopped by percolation of the generated liquid. The degrees of partial melting are closely related to spreading rates; 3) the magmatic processes involve a discontinuous dynamic evolution of spreading displayed by a pulsatory magmato-tectonic activity which is controlled by the speed of decompression of mantle material.

Evidence for contrasting compositional spectra in comagmatic intrusive and extrusive rocks of the late Archean Blake River Group, Abitibi, Quebec

1988 ◽  
Vol 25 (1) ◽  
pp. 134-144 ◽  
Author(s):  
Suzanne Paradis ◽  
John Ludden ◽  
Léopold Gélinas
Keyword(s):  
Magma Chamber ◽  
Fractional Crystallization ◽  
Open System ◽  
Closed System ◽  
Greenstone Belt ◽  
Magma Mixing ◽  
Volcanic Rocks ◽  
Abitibi Greenstone Belt ◽  
Intrusive Rocks

The Flavrian pluton is a sill-shaped intrusion in the Blake River Group (BRG) volcanic rocks in the Noranda region of the Abitibi greenstone belt. The pluton is dominated by trondhjemites and tonalites, with minor peripheral quartz gabbro and hybrid phases. The BRG volcanic rocks consist of a bimodal suite of basalt–andesite and rhyolite. The Flavrian trondhjemites are geochemically identical to the rhyolitic lavas of the BRG (SiO2 ≥ 72%, La/Sm = 3.4, La/Yb = 3.6, Zr/Y = 3.9, Y/Nb = 3.1), and the Flavrian gabbroic and dioritic rocks are identical to the BRG basalts and andesites (SiO2 < 58%, La/Sm = 3.0, La/Yb = 5.5, Zr/Y = 4.2, Y/Nb = 3.3). However, the tonalitic rocks of the Flavrian pluton have no extrusive equivalents in the BRG. The different compositional spectra of the extrusive and intrusive rocks are interpreted as being a result of a transition in magma-chamber evolution from a zoned open system that was active during the evolution of the volcanic rocks to closed-system plutonic crystallization. The latter destroyed the compositional bimodality of the magma chamber and resulted in the evolution of intermediate compositions (tonalites) generated by both fractional crystallization and magma mixing.

Diverse lavas from closely spaced volcanoes drawing from a common parent: Emmons Lake Volcanic Center, Eastern Aleutian Arc

2009 ◽  
Vol 287 (3-4) ◽  
pp. 363-372 ◽  
Author(s):  
Margaret Mangan ◽  
Thomas Miller ◽  
Christopher Waythomas ◽  
Frank Trusdell ◽  
Andrew Calvert ◽  
...  
Keyword(s):  
Volcanic Center ◽  
Aleutian Arc ◽  
Common Parent

scholarly journals Sr isotope chemistry of contaminated Tertiary volcanic rocks from Disko, central West Greenland

1987 ◽  
Vol 36 ◽  
pp. 315-336
Author(s):  
A. K. Pedersen ◽  
S. Pedersen
Keyword(s):  
Fractional Crystallization ◽  
Closed System ◽  
Dominant Role ◽  
Volcanic Rocks ◽  
The Other ◽  
Sr Isotopes ◽  
Sr Isotope ◽  
Crustal Rocks ◽  
Early Tertiary ◽  
Sandstone Composition

The Sr isotope chemistry of 26 samples of Tertiary volcanic rocks from the Vaigat and Maligat Formations on Disko are presented together with 5 samples of potential sedimentary contaminants from Disko and Nugssuaq. The volcanic rocks include one primitive picrite; 11 basalts, 8 andesites, 4 dacites and 2 rhyolites. Except for two basalts, all the basaltic to rhyolitic rocks are distinctly enriched in radiogenic Sr and this together with petrographical observations is taken as evidence for reaction with crustal rocks. The widespread xenoliths and xenocrysts point to Mesozoic to early Tertiary sediments as the major contami­nants and a shale and a sandstone composition have accordingly been chosen as model contaminants. Assimilation and Fractional Crystallization (AFC) calculations indicate that mafic silicates were the predominant fractionating phases in the contaminated members of the Vaigat Formation, whereas plagioclase crystallization and equilibration played a dominant role in the contaminated members of the Maligat Formation. The Kuganguaq Member in the Vaigat Formation cannot be modelled with a shale contaminant, but easily with a sandstone contaminant, and one dacite sample in the Nordfjord Member of the Maligat Formation is best modelled with sandstone contaminant. For all the other rocks, there is evidence of a dominating shale contamination. The most strongly contaminated rock on Disko analysed for Sr isotopes is a rhyolite from the Nordfjord Member, whereas another rhyolite showed evidence of less contamination but very extensive feldspar fractionation. None of the silica-enriched rocks on Disko appear to be formed by closed system fraction­ation of a basic uncontaminated magma.

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