Abstract

Knowledge of melt transfer within the mantle is primarily from the study of mid-ocean ridge settings, leaving elusive the process of sub-arc melt transfer. The sub-arc mantle section of the Sapat Complex (Kohistan-Pakistan) exposes coarse-grained dunites that contain clinopyroxene-enriched zones, which, in turn, contain gabbroic lenses. Structural, petrological, and chemical relationships indicate that the clinopyroxene-enriched zones reflect a continuum of melt transport mechanisms between pervasive percolation and fully segregated melt flow. This spectrum of mechanisms and the petrographic features at Sapat are explained by mechanical flow instabilities (porosity waves) that cause channeling of pervasively distributed melt.

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