The mechanism for generating plagioclase-supersaturated basic magma is crucial to the origin and evolution of massif anorthosites. A model is proposed to explain their temporal and tectonic association, invoking iterative plagioclase accumulation, magma mixing, and phenocryst resorption to produce plagioclase-supersaturated parent liquids. By analogy to mid-ocean ridge systems, the model invokes periodic replenishment of magma reservoirs in an environment of incipient or very slow dilation. These conditions are believed to characterize anorogenic anorthosite complexes.

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