Geology and Geochemistry for Medium Enthalpy Geothermal System of Mount Pandan

Abstract

Geothermal field of Mount Pandan is located between Bojonegoro, Madiun, and Nganjuk. Based on the geological condition, Mount Pandan is lied in the middle of Kendeng Basin and at the northern part of active volcanic. Mount Pandan is a non-active volcano, Early Pleistocene in age with elevation 800 masl. This research conducted by petrographic and geochemistry analysis to identify the conceptual model and geothermal system of Mount Pandan. The lithology of the study area consists of volcanic breccia, andesite intrusion, carbonate siltstone, and limestone. Furthermore, there are 12 warm springs produced by the emergence of geothermal heated groundwater that rises to the surface that controlled by strike-slip fault. JR-1, JR-2, JR-3 and BK group are controlled by NE-SW sinistral fault and the other of manifestations in Mount Pandan are controlled by NW-SE dextral fault. JR-1, JR-2, and JR-3 warm springs emerge in 206 masl as chloride water and JR-4, JR-5, BK group, TD-1 and PG-1 warm springs emerge in 490 masl as bicarbonate water. Regarding geochemistry analysis, the reservoir temperature of Mount Pandan is 185°C that reveals this mountain has geothermal medium enthalpy system. In addition, the reservoir rocks are carbonate sedimentary rocks from Kalibeng Formation that its heat source associated by magmatic activities.