| Abstract |
This abstract describes and summarizes a provisional interpretation of the technical data related to a new geothermal exploration area in the Andes. It is located in the northernmost part of Chile, near a small town named Colpitas, and located in the, Region of Arica and Parinacota (XV) with an elevation ranging from about 4,000 to 5,200 m asl. Geologically, the area is characterized by volcanic rocks and volcanoclastic deposits, and volcano-sedimentary sequences ranging in age from the Miocene to Holocene with at least 3 active volcanic complexes within the Central Andes Volcanic Zone. Structurally, there are at least 2 main systems of volcanic centers aligned in NW-SE and NNE directions with the same orientation than the fold axes and fault strikes associated to Middle Miocene deformation. The latter have uplifted the Western Cordillera, affecting to pre-Middle Miocene rocks. From a regional scale there is a NW-SE alignment of Holocene-Pleistocene volcanic edifices. Additionally, towards the NE of the area, subsuperficial seismic activity has been evidenced and could be associated to geological structures affecting Middle Miocene and Mio-Pliocene rocks. Thermal activity occupies the bottom portion of a wide basin, thermal springs have temperatures that range from 28 to 55°C with a total flow of <10 l/sec. Many of the springs have moderate bubbling of what is likely to be CO2 and H2S gas. The springs are strongly controlled by the regional hydrology, as they discharge in low lying areas and in stream drainages. In this areas salt deposits XRD indicate the presence of silica sinter (amorphous silica /opal-A, quartz, cristobalite) and sulphur, halite, ulexite, calcite and other minerals. Na/K ratios of the thermal spring waters give equilibration temperatures higher than 200°C. Helium isotopes ratio from bubbling in the hot springs shows R/Ra values between 1,4 and 1,6, suggesting the existence of an active heat source in the area. A 3D MT study was recently carried out, showing an important conductive zone of several tens of km2. The resistivity of the conductive areas is around 3-8 ? m, while the connection patch is >~10 ? m. The geophysical anomaly shows an important prospective area for a geothermal reservoir. This area will be drilled during 2011 for determining the potential of the prospect, leading to the feasibility study for installing a geothermal power plant in the next years. |