Hydrothermal discharge from the El Tatio basin, Atacama, Chile

Abstract

El Tatio in northern Chile is one of the best-studied geothermal fields in South America. However, there remain open questions about the mass and energy budgets, water recharge rates and residence time in the subsurface, origin of dissolved solutes, and processes affecting the phase and chemical composition of groundwater and surface water. We measured and sampled surface manifestations of the geothermal system (geysers, perpetual spouters, mud pools/volcanoes, and non-eruptive hot springs) and meteoric water. From the isotopic composition we infer that the thermal water has a meteoric origin that is different from the composition of local meteoric water. The absence of detectable tritium in thermal waters indicates that most of the recharge occurred pre-1950. Boiling and steam separation from the deep reservoir appear to be the main subsurface processes affecting the thermal fluids. A large amount of heat is lost to the atmosphere by evaporation from surface water and by steam emitted from erupting geysers. Using the chloride inventory method, we estimate thermal water discharge to be 218 to 234 L/s, and the advective heat flow to be 120 to 170 MW.

Local Meteoric Water Line of Northern Chile (18° S–30° S): An Application of Error-in-Variables Regression to the Oxygen and Hydrogen Stable Isotope Ratio of Precipitation

“…Table 2) along with the combined standard deviation on hydrogen and oxygen isotope composition (y and x bars, respectively); error-in-variables local meteoric water line (EIV-LMWL solid line) and the generalized interval (dashed lines; δ 2 H = ±13.1‰ up and down the fitted values on the line). (B) Pampa de Tamarugal aquifer (thick-orange line, [69]), snow and penitentes (dark and light blue diamonds, respectively [41,43,59,61,[63][64][65][66][67][68]) and hydrothermal groundwater (red triangles, [70]; PL: Pampa Lirima, TT: Torta de Tocorpuri) samples compared with the lines described in 'A'. Arrows explain the isotope effects in hydrothermal groundwater [70,74].…”

“…To verify the effectiveness of this approach, we compared the EIV regression and the above described generalized interval with the isotope composition of the following samples from northern Chile: (i) the groundwater from Pampa del Tamarugal [69] ( Figure 1B); (ii) the snow samples (Supplementary File S5; [43,58,59,[61][62][63][64][65][66][67][68]); and (iii) the geothermal waters samples [70].…”

“…In accordance with Crawford et al [6], the Student's t-test was used to check the difference between the two regression slopes. Furthermore, the obtained EIV meteoric water line was also compared with previously published isotope data on precipitation without amount data [28,30,36,[56][57][58][59][60], snow [43,58,59,[61][62][63][64][65][66][67][68], groundwater [69], and geothermal water [70] samples collected up to this point in northern Chile.…”

Geometry of Geyser Plumbing Inferred From Ground Deformation

“…El Tatio geyser field is located in the Atacama desert of northern Chile (Figure a). Here more than 200 thermal features (Glennon & Pfaff, ) discharge regionally derived meteoric water (e.g., Munoz‐Saez et al, ) mixed with magmatic fluids (e.g., Tassi et al, ). Of the thermal features, about 80 are geysers that erupt periodically or episodically at the local boiling temperature of water (86.6 °C).…”

Large wood as a confounding factor in interpreting the width of spring-fed streams

“…The high relief of the Mogollon Rim at 2100 m induces a strong orographic effect (NRCS, 2005), yielding some of the highest precipitation in the state, an annual average of more than 800 mm (Arguez et al, 2010), and the mean annual temperature is 17 • C (Arguez et al, 2010). The area is underlain by Tertiary basalts, Permian limestone (Kaibab Formation), and sandstone (Coconino sandstone), with streambed material made up of valley fill alluvium (Moore et al, 1960). Watersheds included in this study run through oak/pine woodland and wetland meadows.…”