ISOTOPIC HOMOGENEITY AMONG NONEQUIVALENT SECTORS OF CALCITE

Coeval crystallographic growth sectors were microsampled from a fractu re-filling calcite cement crystal with well-developed crystal faces an d concentric zoning to test empirically for isotopic sector zoning. Is otopic and minor element homogeneity among coeval parts of the {01 (1) over bar 2} and {21 (3) over bar 1} sectors suggests that isotopic se ctor zoning ages not occur in calcite. Empirical results are compatibl e with theoretical considerations based on crystal surface geometry, g rowth mechanisms, and a thermodynamic growth model.