The lowermost succession of Javas in the Proterozoic Ventersdorp Supergroup contains Jight weathering ocelli up to 15 cm in diameter which occur in layers of a darker weathering volcanic material. Sorne ocelli appear to merge, and discrete light weathering layers may be the ultimate end-stage of this coalescence. Alternatively, coexisting magmas in the neck of the volcano may have been erupted in varying proportions, and turbulence during fiow caused spalling of large drops of the Jighter weathering material into the other. Severa) lines of field evidence suggest that two distinct liquids coexisted and were rapidly quenched after eruption. Chemical data for ocelli and matrix are consistent with the hypothesis of liquid immiscibility. The differences in compositions between the coexisting pairs of liquids are small and it is suggested that the original magmas must have been close to the consulute composition.
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