Use of two new Na/Li geothermometric relationships for geothermal fluids in volcanic environments

Assessment of performance and parameter sensitivity of multicomponent geothermometry applied to a medium enthalpy geothermal system

“…2). Formulations of Arnórsson (1983) or Fournier and Truesdell (1973) work very well for the andesite fluids approaching the reaction temperature of 140 °C towards the end of Arnórsson (1983), Fournier (1991, Giggenbach (1988), Kharaka and Mariner (1989), Nieva and Nieva (1987), Sanjuan et al (2014) and Verma and Santoyo (1997) Page 7 of 20 Nitschke et al Geotherm Energy (2017) 5:12 the experiments, whereas the temperature of the tonalite fluids is strongly overestimated with temperatures of >300 °C. This failure may be explained by the absence of K-feldspar in the tonalite and therefore the Na/K equilibrium in this case is controlled by other potassium phases (e.g., muscovite), leading to a relative potassium enrichment, which results in that significant temperature overestimation.…”

“…The method leads to dramatic underestimated temperatures (Verma and Santoyo 1997) but also really well fitting results (Sanjuan et al 2014) for the andesite experiment. Calculated temperatures for the tonalite fluids range from underestimations (Verma and Santoyo 1997) to high overestimations (Sanjuan et al 2014). The Li/Mg geothermometer (Kharaka and Mariner 1989) underestimates the reaction temperature for both experiments to a great extent.…”

“…For the andesite fluids calculated temperatures approach reaction temperature over the course of the experiments, but decrease to slightly underestimated temperatures towards the end (120 °C). Na/Li based temperature determination (Kharaka and Mariner 1989;Sanjuan et al 2014;Verma and Santoyo 1997) is obviously rather less appropriate, giving a broad range of apparently erratic results depending upon experiment and applied formulation. The method leads to dramatic underestimated temperatures (Verma and Santoyo 1997) but also really well fitting results (Sanjuan et al 2014) for the andesite experiment.…”

“…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…”

“…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 system and equilibria of micas). Furthermore, empirical geothermometers using the ratios of Na/Li and Mg/Li (Fouillac and Michard 1981;Kharaka and Mariner 1989;Sanjuan et al 2014) has been established, additionally accounting for fluid salinity, chloride concentration and the geology of the reservoir. However, solute geothermometry still is afflicted with great uncertainties often leading to a broad range and often inconsistent calculated reservoir temperatures (Santoyo and Díaz-González 2010;Verma and Santoyo 1997), in particular exploring geothermal systems, where only few information (geology, borehole data etc.)…”