The articles in this special issue (Vol. 89, no. 8) have been placed in the context of mineral-ization related to a volcano-plutonic continuum of siliceous magma bodies that rise through the crust under tectonic extension and progressively leak fluids, pyroclastic ejecta, and lava domes; explode with catastrophic evolution of ignimbrites (ash-flow tuffs) during concurrent caldera collapse; and continue to be a source of heat, fluids, and minor pyroclastic and lava dome eruptions. Long after original volcanism has ceased, faults related to caldera collapse and/or regional extension may control later magmatic and hydrothermal episodes. The de-gree to which meteoric waters are heated and mixed with magmatic fluids is the prime determinant for hydrothermal ore deposition and alteration; other factors include magma type, wall-rock composition, and stress regime. There are three principal tectono-petro-graphic-metallogenic associations: 1. Calc-alkalic: in continental arcs and, especially, back arcs. Chalcophile base metals (including some Cu porphyries) below the zone of boiling, precious metals in the epithermal zone above; acid sulfate alteration of lava domes or near-surface intrusions if fluids are domi-
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Wolfgang E. Elston (1994) studied this question.