Diversification of Archean tonalite-trondhjemite-granodiorite suites in a mushy middle crust

Abstract Tonalite-trondhjemite-granodiorite (TTG) suites are the dominant component of Earth's first continents, but their origins debated. The trace element concentrations these rocks conventionally linked to source depths and inferred geodynamic settings with implicit assumption that TTG compositions source-controlled. Alternatively, variable may be caused by fractional crystallization in plutons after emplacement less clearly depth. Most TTGs Archean mid-crustal exposures igneous gray gneiss complexes; processes influence evolution magmas this setting poorly understood. We present a petrological–geochemical model explains coexistence middle crust low-pressure high-pressure geochemical trends, irrespective tectonic or depth source. propose were long-lived crystal mushes controlled separation early-crystallizing plagioclase melt. Using phase equilibrium modeling, we demonstrate suite from southern Superior Province Canada represents variably plagioclase-rich melt-rich fractions common parent magma. behavior have strong on trends TTGs, including degree rare earth fractionation. Our results suggest not primarily reflect cannot used alone infer settings.