| Abstract |
Hydrothermal minerals in the Darajat geothermal field occur in two main styles: replacement and in veins. The former is a product of reactions between thermal fluids and primary minerals present in the reservoir rocks, comprising andesite lavas and pyroclastics. Although the minerals formed in both styles are the same, e.g. wairakite, prehnite, epidote, calcite, their significance differs and show that changes in hydrology have occurred in at least part of the Darajat reservoir. The textural relations within the vein minerals, for example, record local progressive cooling. |