Thermodynamic limits for assimilation of silicate crust in primitive magmas

Abstract Some geochemical models for basaltic and more primitive rocks suggest that their parental magmas have assimilated tens of weight percent crustal silicate wall rock. But what are the thermodynamic limits assimilation in magmas? We pursue this question quantitatively using a freely available tool phase equilibria modeling open magmatic systems—the Magma Chamber Simulator (https://mcs.geol.ucsb.edu)—and focus on wall-rock partial melts, which is thermodynamically efficient compared to bulk stoped blocks igneous systems. In simulations, diverse komatiitic, picritic, assimilate progressive melts preheated average lower, middle, upper crust amounts allowed by thermodynamics. Our results indicate it difficult any subalkaline magma than 20?30 wt% or middle before evolving compositions with higher SiO2 (52 wt%). On other hand, typical komatiitic potential as much own mass (59?102 wt%) lower retain composition. The melt assimilant heavily influence both how energetically possible final composition given temperatures. These findings important implications role generation evolution of, e.g., ultramafic mafic trans-Moho systems, siliceous high-Mg basalts, massif-type anorthosites.