Geochemical Assessment of Low-Temperature Geothermal Fields in Philippine Geothermal System: The Case of Mabini (Batangas) and Montelago (Naujan, Oriental

Abstract

The geothermal potential of Mabini and Montelago prospects is evaluated by the employment of geochemical tools: the CI-SO4 HCO3 and CI/B vs CI plots, and the fluid mineral equilibrium diagrams and g geothermometry. The former set is to select the sprin(s) fit for geothermometry calculations by identifying the types of waters and hydrol9ogical processes, while the latter set is to evaluate the state of equilibrium of the aquifer of the selected spring.

In Mabini prospect, the springs fit for geothermometry calculations originated from sea waters that pecolated at depth and reacted with the rock. These springs attained fluid mineral equilibria at depth. The temperature of the aquifer feeding this type of springs ranges from 150 (Tquartz) to 200oC (NaKCa at p=1/3).

In Montelago prospect, its springs originated from lake waters that percolated at depth and reacted with the rock. These springs also attained fluid mineral equilibria. The aquifer temperature range from 150 (TChalcedony) to 190oC (Na/K-Fournier).