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Science 30 October 1964:
Vol. 146. no. 3644, pp. 635 - 637
DOI: 10.1126/science.146.3644.635
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Articles

Origin of High-Alumina Basalt, Andesite, and Dacite Magmas

Warren Hamilton 1

1 U.S. Geological Survey, Denver, Colorado

The typical volcanic rocks of most island arcs and eugeosynclines, and of some continental environments, are basalt, andesite, and dacite, of high alumina content. The high-alumina basalt differs from tholeiitic basalt primarily in having a greater content of the components of calcic plagioclase. Laboratory data indicate that in the upper mantle, below the level at which the basaltic component of mantle rock is transformed by pressure to eclogite or pyroxenite, the entire basaltic portion probably is melted within a narrow temperature range, but that above the level of that transformation plagioclase is melted selectively before pyroxene over a wide temperature range. The broad spectrum of high-alumina magmas may represent widely varying degrees of partial melting above the transformation level, whereas narrow-spectrum tholeiite magma may represent more complete melting beneath it.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Geological evolution of the New Hebrides island arc.
A. H. G. MITCHELL and A. J. WARDEN (1971)
Journal of the Geological Society 127, 501-529
   Abstract »    PDF »
Andesitic Volcanism and Seismicity around the Pacific.
W. R. Dickinson, W. R. Dickinson, and T. Hatherton (1967)
Science 157, 801-803
   Abstract »    PDF »


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