Compositional transects showing Al₂O₃, CaO, and CaO/Na₂O profiles across the crystal–liquid interface in resorbed crystals. At 900 °C, plagioclase (Pl) crystals are surrounded by a boundary layer melt (BLM) enriched in dissolved plagioclase components. Boundary layers are typically 2 μm and up to 3.5 μm wide; at greater distances from crystals, melt compositions are unaffected by dissolving plagioclase (far-field melt, FFM). Some plagioclase rims also show 1- to 2-μm-wide rims of elevated CaO and CaO/Na₂O (↑An rim). Error bars in (b) indicate typical analytical uncertainties.