Spatial Distribution of Alteration Mineralogy and Ground Temperature at Wairakei Thermal (Geyser) Valley, New Zealand

Abstract

A survey of thermal activity, shallow(15cm deep)temperatures, and surface alteration at Wairakei (Geyser Valley), made in September 1989, shows that activity there extends over an area of about and now consists entirely of steaming ground warm ground fumaroles and mud pools. Features which prior to 1960dischargedalkali-chloride water are now either extinct or else replaced by fumaroles. However, two new fumaroleshave appeared in recent years, and the occurrence of silica sinter, including geyserite, records the locationsof the extinct alkali-chloride features. Steam-condensate-produced alteration comprises a subzone of kaolinite + alunite hematite silica polymorphs, which is associated with presently steaming ground, and a kaolinite +smectite hematite alunite cristobalite tridymite amorphous silica subzone. The latter occurs in areas of fossil steaming ground, surroundinggeyserite depositsand associated with mud pools.