POST-METAMORPHIC LOW DELTA-C-13 CALCITE IN THE CYCLADIC COMPLEX (GREECE) AND THEIR IMPLICATIONS FOR MODELING FLUID INFILTRATION PROCESSES USING CARBON-ISOTOPE COMPOSITIONS
J. Ganor et al., POST-METAMORPHIC LOW DELTA-C-13 CALCITE IN THE CYCLADIC COMPLEX (GREECE) AND THEIR IMPLICATIONS FOR MODELING FLUID INFILTRATION PROCESSES USING CARBON-ISOTOPE COMPOSITIONS, European journal of mineralogy, 6(3), 1994, pp. 365-379
Calcite veins and overgrowths with deltaC-13 values of -12 parts per t
housand to -8 parts per thousand and deltaO-18 values of 24 parts per
thousand to 27 parts per thousand are shown to be characteristic featu
res of the Cyclades metamorphic complex of Greece. Field and petrograp
hic characteristics and the marked carbon and oxygen isotope disequili
brium that the veins and overgrowths show with host metamorphic rocks
indicate that they developed during post-metamorphic evolution of the
complex. The low deltaC-13 values are interpreted to be either the res
ult of the oxidation of organic carbon or solution of soil CO2 by surf
ace waters moving downwards along extensional fractures generated duri
ng the late stages of exhumation. Carbon and oxygen isotopic compositi
ons reported for the carbonate fraction of many pelitic schists on Nax
os overlap with the range of these late carbonates and may in part ref
lect a contribution of this late calcite. Uncertainties regarding the
origin of low deltaC-13 values in the carbonates of metamorphic rocks
shows that they must be used with caution as tracers of fluid-rock exc
hange.