FERUVITE FROM THE SULLIVAN PB-ZN-AG DEPOSIT, BRITISH-COLUMBIA

Feruvite, an uncommon Ca-and Fe2+-rich tourmaline species, has been di scovered in the footwall of the Sullivan Pb-Zn-Ag deposit (British Col umbia) near gabbro sills and dikes. Its chemical composition varies ac cording to occurrence: feruvite from the shallow footwall has lower Ca , higher Al, and higher X-site vacancies than that from the deep footw all. The major chemical substitution involved in the feruvite is the e xchange vector CaMgO square(-1)Al(-1)(OH)(-1). The most important fact or controlling feruvite formation; at Suilivan is likely the reaction of Fe-rich hydrothermal fluids with Ca-rich minerals in gabbro and hos t rocks. This reaction led to the breakdown of Ca-rich minerals (plagi oclase and hornblende), with release of Ca to solution and its incorpo ration into feruvite. This process probably postdated the main stages of formation of fine-grained, intermediate schorl-dravite in the tourm alinite pipe in the footwall, and is attributed to postore intrusion o f gabbro and associated albite-chlorite-pyrite alteration.