| A survey of surface, spring and borehole
waters associated with the ophiolite rocks of Cyprus shows five broad water
types (1) Mg-HCO3, (2) Na-SO4-Cl-HCO3, (3)
Na-Ca-Cl-SO4-OH-CO3, (4) Na-Cl-SO4 and (5)
Ca-SO4. The waters represent a progression in chemical reactivity
from surface waters that evolve within a groundwater setting due to hydrolysis
of the basic/ultrabasic rock as modified by CO2-weathering. An increase
in salinity is also observed which is due
to mixing with a saline end-member (modified sea-water) and dissolution of
gypsum/anhydrite. In some cases, the waters have pH values greater than 11. Such
high values are associated with low temperature serpentinisation reactions. The
system is a net sink for CO2. This feature is related not only to
the hydrolysis of the primary minerals in the rock, but also to CaCO3
or Ca-Mg-CO3 solubility controls. Under hyperalkaline conditions,
virtually all the carbon dioxide is lost from the water due to the sufficiently
high calcium levels and carbonate buffering is then insignificant. Calcium
sulphate solubility controls may also be operative when calcium and sulphate
concentrations are particularly high.
Keywords: Cyprus, Troodos, ophiolite, serpentinisation,
spring, stream, water quality, bromide, iodine, boron, trace elements,
hyperalkaline. |