Basic Knowledge of Geochemical Processes

Travertines (or thermogene travertines in Pentecost 2005) are formed from hydrothermal water with an initial high concentration of Ca2+ and CO2 partial pressure (Ford and Pedley 1996; Gandin and Capezzuoli 2008, 2014; Capezzuoli et al. 2014). In this type of water, the active CO2 degassing immediately after discharging on the ground increases pH and saturation state with respect to CaCO3 of the water. Precipitation (and dissolution) of CaCO3, which is associated with CO2 degassing (and uptake), is often simply represented in the following reaction 2.1: