Abstract

Volcanic-hosted massive sulfide deposits exhibit a continuous range in metal composition from copper-dominated (Cyprus type) to lead-rich zinc (+ copper) deposits (Kuroko type). This spectrum is best viewed as a progressive enrichment in large ion lithophile elements (LILE) in the ores (e.g., Pb, Ba) and the magmatic systems (e.g., K) responsible for their generation. Thus, lead-rich volcanic-hosted massive sulfide deposits are associated with calc-alkalic magmatism in mature are systems (e.g., Buchans) or in back-arc sites, where older continental crust can be implicated in magma genesis. At the copper-rich end of the spectrum, ores are related to plagiogranites in supra-subduction-zone ophiolite complexes, and LILE enrichment is minimal. The ancient back-arc assemblages that now constitute greenstone belts host Cu-Zn massive sulfide deposits associated with tholeiitic-calc-alkalic magmatic systems of intermediate LILE enrichment. I suggest that these variations in both the metal composition of such ores and the petrochemistry of coeval intrusions relate in a fundamental way to the siting of their emplacement in arc and back-arc systems and the duration of the subduction process.

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