Chachimbiro Geothermal area, Northern Ecuador -- A new magnetic
exploration.
Abstract
Geophysical surveys are efficient ways to obtain information on areas
that are promising for geothermal energy. One of the geophysical
techniques commonly used is the magnetic method, which is useful to
detect shallow structures and changes in magnetization due to processes
related to geothermal activity, such as faulting and hydrothermal
alterations. Despite the richness of available geothermal resources in
South America and Ecuador, the use of these resources for electricity
production is very limited. Chachimbiro, in northern Ecuador, is one of
the potential sites for developing a geothermal power plant. Our
objective is to provide complementary magnetometry data to improve the
existing model of the geothermal area. We performed high resolution
ground magnetometry survey of ~30 m spacing around the
prospective drilling area in order to better understand the shallow
structures above the reservoir. We also performed two additional survey
lines with ~5 m spacing across possible fault locations.
After necessary data reductions the magnetic anomaly map was compared
with a digital elevation model and a geological map of the area. This
helped to understand the distribution of the anomalies and their
relation with the presence of high magnetic susceptibility materials,
hydrothermal alterations and topography. Major anomalies observed in the
magnetic profiles were compared with forward fault models, allowing us
to distinguish topographic from fault effects. We then compared our new
magnetometry results with previous geophysical models of the Chachimbiro
geothermal system. The large long-wavelength negative anomaly on the
Northeast side of the survey area seems to coincide with the suggested
location of the clay cap, and can therefore be used to improve the
existing models. The new magnetic exploration of Chachimbiro therefore
shows the usefulness of this method to locate magnetic anomalies related
to faulting and hydrothermal alterations.