Soil CO2 flux and temperature from a new geothermal area in the Cordón de Inacaliri Volcanic Complex (northern Chile)

The Hydrothermal Alteration of the Cordón de Inacaliri Volcanic Complex in the Framework of the Hidden Geothermal Systems within the Pabelloncito Graben (Northern Chile)

“…Thirty-six samples of hydrothermally altered rocks and silica deposits from the CIVC alteration zone were collected for this study. The sampling area was divided into 2 sectors and includes and widens the regions described by Taussi et al [28]. The alteration zones developed parallel to the NW fault of the Pabelloncito graben in the western sector (CIWS), and parallel and transversely to this fault in the eastern sector (CIES), follow-ing an ENE-striking lineament.…”

“…The CIVC shares the same NW-SE tectono-morphological structure (the Pabelloncito graben) that controls the Cerro Pabellón geothermal field (Figure 1) [29]. A ~9 km 2 intense superficial, mainly fossil, hydrothermal alteration was observed in the volcanic deposits of the CIVC located inside the graben (Figure 1) and includes local sites of steaming ground with soil temperatures ranging from 40 °C to 80 °C and diffuse CO2 degassing, mainly related to an endogenous source [28].…”

“…The CIVC is part of the Pleistocene-age Palpana-Inacaliri volcanic chain [29][30][31][32] consisting of three main NW-SE-aligned stratovolcanoes, with the Inacaliri volcano itself located at the southern end of the graben [33] (Figure 1). The NW-SE graben orientation is coincident with the defined Andean Transversal Faults, which cross the Andean belt and constitute the main crustal routes for the migration of fluids towards surface [28,34]. Since 2017, the Cerro Pabellón geothermal field has been the only South American active geothermal power plant with a 48 MWe capacity already installed, with an additional 33 MWe that will be finally running by the end of 2021.…”

“…In the CIWS, large inactive areas of whitish alteration, mostly composed by kaolinite-alunite (Figure 2A), isolated silica deposits (Figure 2B,C), some of them with pinnacle-like structures (Figure 2D), and fractures filled with carbonate deposits in the topographically higher areas (Figure 2E) were identified. Active zones are also associated with heated reddish and gray steaming grounds (40-80 °C, in situ measurements [28]), surrounding the pinnacle-like structures, with few mineral precipitates in concretions and greenish to whitish centimetric efflorescence (Figure 2F). In the CIES, the inactive zones are associated with an extensive development of the whitish kaolinite-alunite rich regions along and parallel to the NW-striking lineaments of the Pabelloncito graben (Figure 3A,B).…”

“…This work is focused on the study of the hydrothermal mineralogy occurring in the Cordón de Inacaliri Volcanic Complex (CIVC), located in the Central Volcanic Zone of the Andes, near the Chile-Bolivia border. In the studied area, a significant 9 km 2 halo area of surface hydrothermal manifestations are identified [28]. In this paper, we will discuss the evolution of mineral parageneses of the hydrothermal alteration deposits of the CIVC, specifying the growth and transformation processes that occur in the silica phases, discriminating among steam-heated deposits, massive silica and sinters.…”