A Submarine Magmatic-Hydrothermal System at Brothers Volcano, Kermadecs

Abstract

Secondary minerals in dredge samples from the Brothers Volcano include silicates, silica polymorphs; Na-Al, Ca, Ba and Ba-Sr sulphates; Fe, Cu, Zn, As and Pb sulphides; Fe and Mn oxide/oxyhydroxides and native S. The variety and range of mineral compositions indicate deposition in different parts of a submarine hydrothermal system characterised by differences in temperature (ambient seawater to >300oC), fluid compositions, degree of magmatic-hydrothermal water-rock interaction and degree of seawater influence. Secondary minerals originate from a partly exhumed waning hydrothermal system/s (NW caldera); the main upflow of a relatively well-established active magmatic-hydrothermal system on the seafloor where sulphide-rich chimneys are extant (SE caldera) and a nascent magmatic-hydrothermal system where crack zones localise upwelling acid waters from depth (cone).