MINERALOGY OF HYDROTHERMAL ALTERATION AND FLUID INCLUSIONS OF CLARK VOLCANO AREA, KERMADEC TRENCH, NEW ZEALAND

ABSTRACT

Clark Volcano is a recently discovered feature on the western side of Kermadec Ridge and represents just one of the multiple submarine hydrothermal systems that occur in this region. Mineralogical associations indicate that high temperature fluid escapes from vents. Dredged samples on the margin of this volcano exhibit both, partial replacement and direct deposition of anhydrite and barite. Four general stages were recognized. XRD analysis indicates that anhydrite and lead-strontium rich barites are the main mineralogical phases. Silica is rare and occurs only in earlier paragenetic stages. XRF analyses suggest that lead and strontium replaces barium in the barites whereas barium and strontium substitute for calcium in anhydrites. Zinc and strontium concentrations appear to be preferably associated with barite. Primary liquid-rich fluid inclusions in anhydrite are not common and ice-melting temperatures range from –8.9 to –9.3ºC, whereas vapor-rich fluid inclusions in anhydrite are rare.