The Impact of Understanding an Arcuate Feature to the Expansion of the Upper Mahiao Geothermal Resource, Tongonan, Leyte

Abstract

Identification of arcuate structures such as craters, calderas and flank collapse is important in geothermal exploration especially in inferring the location of the heat sources of a geothermal system and in mapping possible volcano-related geohazards. This study suggests criteria for the recognition and classification of different arcuate structures especially in highly-eroded volcanic terrains such as that of the Tongonan Geothermal Project (TGP), Leyte and in the understanding of their roles in the development of a geothermal system. This paper also presents the results of a recently conducted geologic mapping and remote sensing analysis in TGP which was used to refine the understanding of a known arcuate structure called the Cabungangan Crater and its impact to the further development of the geothermal resource. This volcanic feature has been previously considered to be breached crater of the Cabungangan Volcano and has been targeted for permeability and temperature in six geothermal wells. However, the types of rocks observed within the vicinity of the area are not typical deposits associated to the formation of any of the aforementioned arcuate structures. The integrated results of remote sensing, field mapping and assessment of drilled wells indicate that the Cabungangan Crater is merely an erosional feature rather than a volcanic crater.