BackgroundThe estimation of reservoir temperatures is a major goal in geothermal exploration. The in situ temperature is a key parameter for the assessment of geothermal potentials and the economic efficiency of prospected reservoirs. Deducing these temperatures from the chemical composition of geothermal fluids emerging at the earth's surface is a commonly used and relatively cost-effective method. Over more than five decades a large number of solute geothermometers have been established and constantly improved [e.g., Fournier and Rowe (1966), Giggenbach (1988), Can (2002), Sanjuan et al. (2014)]. Many of these interrelations, linking the concentration of one constituent or the ratios AbstractThe determination of reservoir temperatures represents a major task when exploring geothermal systems. Since the uncertainties of classical solute geothermometry are still preventing reliable reservoir temperature estimations, we assess the performance of classical geothermometers and multicomponent geothermometry by applying them to fluids composed from long-term batch-type equilibration experiments and to fluids from natural geothermal springs in the Villarrica area, Southern Chile. The experiments, weathering two reservoir rock analogues from the Villarrica area, highlight a strong impact of reservoir rock composition on the fluid chemistry and, consequently, on calculated in situ temperatures. Especially temperatures calculated from classical solute geothermometry are strongly affected. Multicomponent geothermometry is obviously more robust and independent from rock composition leading to significantly smaller temperature spreads. In a sensitivity analysis, the dilution of geothermal fluid with surficial water, the pH and the aluminum concentration are anticipated to be the factors causing underestimations of reservoir temperatures. We quantify these parameters and correct the results to obtain realistic in situ conditions. Thus, enabling the application of the method also on basis of standard fluid analysis, our approach represents an easyto-use modification of the original multicomponent geothermometry leading to very plausible subsurface temperatures with significantly low scattering. Keywords: Multicomponent geothermometry, Classical solute geothermometers, Laboratory alteration experiments, Villarrica geothermal systemOpen Access © The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Nitschke et al. Geotherm Energy (2017) Nitschke et al. Geotherm Energy (2017) 5:12 of cations (SiO 2 , Na/K, K/Mg, Na/K/Ca) to the in situ temperature, are based on rather well known water-rock interaction processes (silica solubility, cation exchange in the feldspar syste...

No abstract