| Abstract |
Plan view maps depict temperature, geology and alteration mineralogy at three levels (100m, 400 m, 750 m) below ground surface within the Broadlands-Ohaaki geothermal field. The distribution of adularia-illite-calcite-pyrite and calcite-siderite-kaolinite mineral assemblages are spatially and genetically related to the position of two main fluid types,chloride and steam-heated waters, respectively. In addition, the dismbution of temperature sensitive clay minerals (montmorillonite, illite) closely parallels the patterns of isotherms. For both active and extinct geothermal settings, alteration mineralogy supplies information regarding fluid temperature, and permeability which is useful for interpreting the paleohydrology. |