Fig. 1: Back-scattered electron (BSE) imaging of representative olivine grains in Weltevreden komatiites.

Though affected by serpentinization, the unaltered core is preserved. The upper row is low δ18O olivine grains; the lower row is normal δ18O olivine grains. The yellow spots represent the analysis domain for δ18O by SIMS and Fo by EPMA. The yellow number is the δ18O value of olivine; the black number is the Fo content. Each grain shows uniform δ18O-Fo compositions without core-rim zoning. Ol, olivine; Ser, serpentine; Py, pyroxene; Mt, magnetite.