Geological Field Mapping for Geothermal Exploration

Abstract

A geological map shows the various rock types of the area, structural features, geological formations, hydrothermal manifestations, age relationships, etc. With the development of technology, geological maps today are more precise than ever as a combination of accurate satellite imagery, aerial photographs, high-tech geological equipment and Geographic Information Systems (GIS) advancements. Field mapping activity is usually carried out in four phases, which have a stepwise relationship: a) planning/research; b) field data collection; c) laboratory analysis and d) report writing. At the beginning of a geological study of a new geothermal area, in the reconnaissance and prefeasibility stages of a geothermal project, the question is: what aspects is geology looking for? In volcanic environment, the presence of evolved magmas related to the presence of acidic rocks increases the possibility of having huge magmatic chambers that are not so deep. If the age of these rocks is preferably less than 500 000 years, this can give enough heat for a geothermal system (heat source). The study of the types and the kinematics of geological faults in geothermal exploration is very important as the faults and fractures control the movement of the hot fluids at depth (flow pattern). On the basis of other characteristics like degree of fracturing and permeability of the rock deposits observed at the surface, which can be extrapolated at depth, the possible caprock and lithologic units can be inferred, where a geothermal reservoir can be hosted.