David L. Huston, Bruce E. Taylor, Wouter Bleeker, Donald H. Watanabe; Productivity of volcanic-hosted massive sulfide districts: New constraints from the δ18O of quartz phenocrysts in cogenetic felsic rocks. Geology ; 24 (5): 459–462. doi: https://doi.org/10.1130/0091-7613(1996)024<0459:POVHMS>2.3.CO;2
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A correlation has been established between Zn productivity of volcanic-hosted massive sulfide districts and δ18O of quartz phenocrysts from cogenetic rhyolitic rocks. In highly productive districts, ores are associated with rhyolitic rocks, of possible S-type affinity, containing high δ18O quartz phenocrysts. In less-productive districts, ores are associated with I-type rhyolitic rocks with low δ18O phenocrysts. This correlation may be caused by (1) low-temperature isotopic alteration that produced 18O-rich overgrowths on phenocrysts, and (2) emplacement of transitional S-type intrusions at greater depths than I-type intrusions, resulting in larger hydrothermal cells and allowing leaching of more Zn. The latter hypothesis is favored.