Preliminary Exploration Results of the Kalinga Geothermal Prospect, Luzon, Philippines

Abstract

The Kalinga Geothermal Prospect, located in the eastern flank of the Luzon Central Cordillera has been explored since the late 1970?s for its impressive thermal manifestations, faults, and evident Quaternary volcanism. Exploration work conducted in 2010-2012 included limited geologic mapping, literature review, remote sensing acquisition and interpretation, geochemical sampling and geophysical surveys. Geochemical interpretation suggests the existence of a benign geothermal system with an adjacent younger, acidic system. Geologic interpretation suggests that the neutral reservoir could be hosted by the fractured metavolcanic Basement Complex, with enhanced permeability along structures and intrusive contacts. Magnetotelluric data imaged a shallow low resistivity (20-30 ohm-m) layer, which was interpreted as the clay cap overlying the neutral reservoir, while the gravity data allowed for a range of estimates for depth to the top of the intrusive contact. Conceptually, two upflow zones are interpreted, one of which feeds a benign exploitable geothermal reservoir, and the other representing an adjacent immature acidic system associated with the young Caigutan Dome. The heat source for the benign upflow is still uncertain, but there are a number of young volcanic domes mapped in the area, beneath which could be sources of conductive heat input.