Variation of K-rich magma formation during early Aegean arc migration, NE Greece

Magmatic activity in the Aegean region has migrated southward by ~400 km over the past ~34 Ma due to rollback of the subducting African plate, producing age-progressive magmatic centres. In NE Greece, its earliest stage is recorded in the Maronia Magmatic Corridor, where magmatism between ~34 and 29 Ma evolved from calc-alkaline in the northeast to shoshonitic compositions in the southwest. We present new major-element, trace-element ( n = 67), and Sr-Nd-Pb-isotope ( n = 36) data for volcanic and plutonic rocks to investigate magma generation and evolution during early Aegean arc migration. The magmatic rocks define geochemically distinct calc-alkaline and shoshonitic suites. The most mafic samples (4–10 wt% MgO) show higher (Ce/Yb) N ratios in the shoshonite suite (10.8 ± 2.0) than the older calc-alkaline suite (5.5 ± 1.1), accompanied by distinct mean 206 Pb/ 204 Pb i ratios (18.68 ± 0.04 vs. 18.78 ± 0.03). Both suites evolved along coherent fractional-crystallisation ± assimilation trends, although the shoshonitic magmas show mantle-source heterogeneity. Lavas with transitional compositions ( 206 Pb/ 204 Pb i : 18.73 ± 0.01) bridge the two suites. Volcanic and plutonic rocks within individual centres display geochemical similarities, indicating common parental magmas and interconnected plumbing systems. Elevated P₂O₅ contents in transitional (0.4 ± 0.1 wt%) and shoshonitic (0.6 ± 0.2 wt%) magmas reflect increasing contribution from phosphorus-rich shallow-marine sediments, distinct from the pelagic sediments dominating the older calc-alkaline magmas. Our results show that changes in subducted pelagic-to-shallow-marine sediment input during slab rollback control K-enrichment in early Aegean arc magma generation, offering a geochemical framework for identifying discrete slab compositional inputs in migrating arc systems.