Geology and Geothermal Investigation of Hot Springs in Massepe area, Sidenreng Rappang, South of Sulawesi, Indonesia

Geological mapping with the scale of 1:25, 000 and geothemial investigation of four hot springs were conducted in the Massepe, Sidenreng Rappang, South of Sulawesi Island. The study area is located at latitude of 3° 59’ 26.45” S to 4° 2’ 11.16” S and longitude from 119° 46’ 57.29" E to 119° 49’ 41.89” E. The aim of the study is to understand the geological setting and the characteristic of geothermal system of the study area. The research area is identified as a geothermal prospect area and lies in ancient volcanic area with the geomorphologic units of volcanic hill with wavy slope and denudation landform. The study area is composed of four rock units, which are basalt (Middle Miocene to Late Miocene), volcanic breccia (Middle Miocene to Pliocene), limestone (Late Miocene to Pliocene) and andesite (Pliocene), which are overlain by the surficial alluvial deposits (Pliocene until Recent). All four hot springs show the temperature between 38°C to 60°C with the surface temperature between 25°C to 29°C. pH meter reading of all the hot spring are in between 6.2 to 6.57 which is almost natural. The characteristic of geothermal system was interpreted by using geochemistry method. All four hot springs in the study area are classified as the type of chloride water with the temperature of reservoir in between 40°C and 170°C. The secondary data of the resistivity survey at the study area shows the result of the depth of the reservoirs which ranges between 800 meter tol 100 meter.