| Title | Tracking Fluid Pathways in a Geothermal System Using Aster Imagery Band-Ratio Combination: the Case of Licancura Field, Northern Chile. |
|---|---|
| Authors | E. Camus, E. Veloso, F. Aron, D. Morata, C. Wechsler. |
| Year | 2016 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | ASTER, band-ratio combination, geothermal, alteration minerals. |
| Abstract | Identification of surface hydrothermal mineralogy using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery is one of the first steps to define potential areas for geothermal exploration; being especially relevant in areas of difficult access (e.g. high-altitude), where direct sampling is logistically complicated and time consuming. In Northern Chile, there is plenty of surface evidence indicating active and fossil geothermal activity, manifested as highly altered areas, yet most of these sites are located above 3,500 meters above sea level. In this work we aim to develop a remote-sensing technique as a proxy for the identification of active or fossil fluid circulation in potential geothermal zones. As a working example, this methodology was applied to the study of the Licancura Geothermal Field. Here, we used SWIR (short wave infrared) band ratio combination of ASTER imagery to identify areas associated with advanced argillic and propylitic alterations, likely related to emplacement of acid and neutral-alkali fluids. We found a correlation between highlighted electromagnetic spectrum features and minerals formed at specific temperatures at the time of fluid emplacement. Interpreted minerals assemblages are kaolinite+alunite+pyrophyllite and chlorite-epidote+illite-smectite+calcite, which show a preferential spatial distribution and abundance. Such arrangement can be used to estimate fluid circulation and evolution patterns, with different pH and temperature constraints through time. This remote-sensing technique is sought to be considered as a first tool in geothermal exploration and a guide to establish areas of potential interest for geothermal exploration. Ongoing research and work is focusing on X-ray diffraction analyses of samples collected in the field to validate the correlation between remotely-interpreted mineralogical assemblages and field mineral occurrence. |