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ELSEVIER Earth and Planetary Science Letters 169 (1999) 303319 www.elsevier.com/locate/epsl

Summary: ELSEVIER Earth and Planetary Science Letters 169 (1999) 303­319
A model that reconciles major- and trace-element data from abyssal
Paul D. Asimow*
Lamont­Doherty Earth Observatory, Palisades, NY 10964­8000, USA
Received 4 June 1998; revised version received 30 March 1999; accepted 30 March 1999
Abyssal peridotite samples from slow-spreading oceanic ridges have been interpreted as residues of near-fractional
melting processes on the basis of trace-element data, whereas major-element compositions and modes of the same samples
require interactions between migrating melts and residual solids, either by equilibrium porous flow, refertilization, or
olivine crystallization. Modeling of major- and trace-element data shows that these peridotite samples are consistent with
a variety of melting and melt migration histories that include elements or episodes both of near-fractional melting and
of equilibrium porous flow. A component of equilibrium porous flow explains peridotite compositions better than olivine
deposition or refertilization. Mixing of primary basalt liquids composed of variable proportions of unmodified liquid
increments extracted by near-fractional melting, and of liquids transported by equilibrium porous flow generates local
trend systematics like those observed in fractionation-corrected basalt compositions at slow-spreading ridges. Both the
local trend in basalts and the fractionated trace elements in peridotites are absent at the fast-spreading East Pacific Rise,
allowing simpler models of melting and melt migration than those required at Atlantic and Indian ridges and implying a
spreading-rate or magma-flux dependence to the mechanism of melt extraction. © 1999 Elsevier Science B.V. All rights


Source: Asimow, Paul D. - Division of Geological and Planetary Sciences, California Institute of Technology,


Collections: Geosciences