Garnet as a monitor for melt–rock interaction: Textural, mineralogical, and compositional evidence of partial melting and melt‐driven metasomatism

In this study, we focus on a partially melted garnet-bearing granulite from the Salvador–Esplanade Belt (Salvador da Bahia, Brazil), and examine behaviour of major trace elements during partial melting melt-driven metasomatism. Phase equilibria modelling U–Th–Pb geochronology show that sample underwent heating segment decompression path ~1.2 GPa 675–700°C to ~0.8 790°C at c. 2.06 Ga. During final stage decompression, 0.8 ~0.5 GPa, physical segregation melt resulted in establishment chemical potential gradients mass transfer between host leucosome. Modelling shows H2O, CaO, K2O, Na2O diffused into residue, whereas SiO2 was transferred adjacent Opposed senses diffusional formation quartz-rich anhydrous leucosome quartz-depleted selvedge granulite. Compositional maps garnet exhibit contrasting element distributions depending their textural position. The largest located preserve original Ca growth zoning. A transition bell-shaped profiles for Y heavy rare earth bowl-shaped light is consistent with typical Rayleigh fractionation model, fast intergranular mobility, rock-wide equilibrium prograde melting. contrast, smaller away zoning modified by intragranular diffusion, as evidenced network open channels healed cracks act connecting pathways matrix core. This results either subtle modification both inner core inclusions, or complete re-equilibration. Recognition later diffusion implies misleading thermobarometric tectonic interpretations would be obtained if composition used fingerprint early nucleation stage. study demonstrates high temperature (>750°C) presence melt, REE are not less vulnerable diffusive resetting than divalent cations like Ca2+.