ABSTRACT
ABSTRACT: Large empirical field studies of groundwater chemistry in crystalline rock aquifers have been carried out in Norway to ascertain how (and, indeed, whether) groundwater chemistry depends on lithology. A number of dissolved elements, such as radon, uranium and fluoride, exhibit a lithological dependence. However, the distribution of pH and several major ion components in groundwater can largely be explained in terms of feldspar hydrolysis and secondary calcite saturation / precipitation. We contend that the main trends in groundwater chemical composition in most crystalline silicate rock aquifers are not strongly dependent on lithology, but are dependent on five more universal factors; (i) the initial PCO2 of the recharge water, (ii) the degree to which the aquifer geochemical system is “open” or “closed” with respect to CO2, (iii) the availability and composition of hydrolysable silicate phases, (iv) the degree to which CO2 has been consumed by plagioclase hydrolysis and (v) the extent to which feldspar hydrolysis has continued beyond the point of calcite saturation.
