Hydrothermal alteration studies of Gunung Endut, Banten with petrographic method

Hydrothermal alteration is a great indicator of thermal fluid dynamics, especially in a geothermal system. Hydrothermally altered minerals are formed based on temperature and the properties of the protolith. Hydrothermal alteration samples from Gunung Endut Geothermal Working Area were analysed using petrography methods. Importance in determining the hydrothermal alteration for geothermal alteration are use as geothermometers, predict scaling and corrosion, estimate fluid pH and many more. Temperature, permeability and fluid type involved in the alteration process were identified based on the thin section observation. Majority of the samples shows the presence of clay minerals, chlorite and pyrite, indicating a moderate intensity of alteration formed under an argillic alteration environment at ≤ 180 °C. Based on the altered minerals observed under the petrographic microscopy, we then deduce that acidic fluids are the main type of fluid found in Gunung Endut Geothermal Working Area because that argillic alteration minerals showed acid environment.