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Published September 1980 | public
Journal Article

Melt density and the average composition of basalt


Densities of residual liquids produced by low pressure fractionation of olivine-rich melts pass through a minimum when pyroxene and plagioclase join the crystallization sequence. The observation that erupted basalt compositions cluster around the degree of fractionation from picritic liquids corresponding to the density minimum in the liquid line of descent may thus suggest that the earth's crust imposes a density filter on the liquids that pass through it, favoring the eruption of the light liquids at the density minimum over the eruption of denser more fractionated and less fractionated liquids.

Additional Information

© 1980 Springer-Verlag. Received January 31, 1980; Accepted June 24, 1980. Soon after the preparation of this manuscript, we discovered that Sparks and his coworkers had independently noted the density vs. fractionation trend discussed in this manuscript. We thank them for the opportunity to see their manuscript prior to publication. This work was supported by NSF grants OCE 79-09699, EAR 79-06321, EAR 79-23977, NASA grant NGL-22-007-247, and the Committee on Experimental Geology and Geophysics of Harvard University. Contribution Number 3392, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125. A portion of this research was done while D. Walker was a visiting Scientist at the Lunar and Planetary Institute which is operated by the Universities Space Research Association under Contract No. NASW-3389 with NASA. This paper is Lunar and Planetary Institute Contribution No. 411.

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