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.

First Page Preview

First page PDF preview
You do not currently have access to this article.