The Cumulate Paradigm Reconsidered

The cumulate terminology outlined by Wager and coworkers provided a logical system for describing the textures of the rocks of layered intrusions, but recent work shows that this model fails to accommodate all the processes responsible for the petrographic features of coarse-grained rocks. Textures of "adcumulates" and "orthocumulates" in the Skaergaard Intrusion cannot be correlated with concentrations of incompatible elements representing "trapped liquid." Compaction and open-system percolative processes have altered their textures, modes, and even bulk compositions. Although a rock may be a cumulate, in the absence of other evidence, it can be misleading to refer to it in terms of the cumulate nomenclature.