Can Geochemistry Distinguish Extracted Melt from Cumulate with Trapped Melt?

Volcanic and plutonic rocks are crucial to the formation and evolution of the Earth's continental crust, yet the relationship between these rock types remains a topic of ongoing scientific inquiry. A key question is whether crystal-liquid separation within magmatic reservoirs drives the formation of evolved volcanic rocks, with residual cumulates preserved in plutonic bodies. In this study, we test the hypothesis that approximately 30% of the residual melt, trapped within the terminal porosity of the plutonic residue during rhyolitic melt extraction, may obscure the geochemical signature of the cumulate. Using trace- and major-element geochemical modeling, we demonstrate that extracted melts are enriched in incompatible elements and depleted in compatible elements, while the opposite is observed in cumulate residues. Our modeling results show that the geochemical differences between extracted melts and cumulate residues remain distinguishable, even when accounting for the effects of interstitial melt. This suggests that while melt extraction may not be widespread, processes such as cumulate remobilization and other dynamic magmatic interactions could significantly reduce the compositional differences between volcanic and plutonic rocks. Our findings challenge the view that melt extraction is a predominant mechanism responsible for the differentiation of felsic magma on a global scale and highlight the complexity of magmatic processes in the Earth's crust.