Petrographic, Geochemical, and Fluid Inclusion Evidence for the Origin of Siliceous Cap Rocks Above Volcanic-Hosted Massive Sulfide Deposits at Myra Falls, Vancouver Island, British Columbia, Canada

摘要

Massive sulfides at the Myra Falls volcanic-hosted massive sulfide (VHMS) camp, Vancouver Island, British Columbia, Canada, are overlain by white chert, black chert, argillite, and siltstone. White chert is best developed above the Battle orebody, where it forms a siliceous caprock (3–5 m thick) above the massive sulfides. There is a gradational lateral change from white chert above massive sulfides to black chert and unaltered argillite, 100 to 150 m south of the Battle orebody. Chert horizons are also located above the Ridge and Extension ore zones, but only minor chert lies above the HW orebody, which is instead overlain by a thick argillite sequence.