ABSTRACT
The isotopic composition of groundwater is in most cases controlled by meteorological processes. There exist, however, some extreme geological environments where reaction between groundwater and the aquifer matrix or subsurface gases can modify the water’s “meteoric” signature. Some typical processes are shown in Fig. 9-1. Effects of such water-rock interaction dominate at high temperature and over geological time scales, but can also be observed in shallow groundwater flow systems at low temperature. The alteration of the §180 -8 2H composition of groundwater gives insights into its subsurface history and geochemical reactions. In this chapter the isotope exchange processes in extreme hydrogeologic systems are explored.
