The very low Na2O + K2O contents can be explained by the cumulate nature of the rocks.
These plots show a linear relationship with some degree of scatter probably in rocks having cumulate phases.
Most of the gabbro samples plot in the arc-related mafic cumulate field, whereas some samples plot in the arc-related non-cumulate field non-cumulate gabbroic rocks formed in a supra- subduction zone tectonic setting.
Characteristic mineralogy of arc related cumulate gabbros: implications for the tectonic setting of gabbroic plutons and for andesite genesis.
Cumulate recycling and crustal evolution in the Bay of Islands ophiolite.
Autoliths of low-density roof cumulates hosted in high-density floor cumulates may have been transported downwards by convective flow (e.
However, the significant abundance of plagioclase cumulates in the Marginal Zone (~73 vol%) suggests that the development of cumulus frameworks was inevitable and would have eventually connected frameworks in the Main Zone to the walls of the pluton.
Compaction causes the densification of cumulates and simultaneous removal of intercumulus melt through porous flow (Hunter 1996).
The origin of these adcumulate textures through exchange with an overlying reservoir would be indicated by preservation of either significant plagioclase-pyroxene rocks with cotectic proportions and/or complementary mafic-ultramatic cumulates.
Compaction driven by the weight of overlying cumulates, on the other hand, is unlikely because the cumulus minerals had similar to lower density relative to the intercumulus melt.
neous cumulates part I: geochemical consequences for cumulates and liquid fractionation trends.