Geochemical Evolution of Age-Progressive Magmatic Centres in the Northern Aegean Arc

Over the past 32 million years, slab rollback and trench retreat in the Aegean region have led to back-arc extension and southward migration of the subduction zone. Consequently, several age-progressive plutonic centres with associated volcanism formed over a ~300 km distance. This study compiles new and existing geochemical data from igneous rocks of the four oldest magmatic centres in northern Greece: Leptokaria/Kassiteres (~32 Ma), Maronia (~29 Ma), Samothraki (~23–16 Ma), and Limnos (~22–19 Ma).

Major and trace element data reveal significant compositional diversity among the magmatic units. Maronia, Samothraki, and Limnos exhibit shoshonitic compositions characterized by strong enrichment in incompatible elements, whereas Leptokaria/Kassiteres is dominated by a high-K calc-alkaline series with more moderate incompatible element enrichment.

Isotopic data indicate that the two oldest centres, Leptokaria/Kassiteres and Maronia, have less radiogenic Sr and more radiogenic Nd signatures than the younger shoshonites from Samothraki and Limnos. In addition, the shoshonitic rocks display higher La/Yb ratios than the calc-alkaline samples, with the highest values observed in the Limnos and Samothraki samples.

High P/Nd and Ba/La ratios in the shoshonites are consistent with a lower degree of partial melting, however, suggest an additional influence from a mantle source enriched by subducted P- and Ba-rich sediments. Nd/Sr and Hf/Nd ratios, together with isotopic signatures, indicate that sediment–mantle mixing played a major role before partial melting. The observed geochemical and isotopic diversity along the arc is likely the result of mixing of variable sediment with the mantle, possibly in the form of a heterogeneous peridotite–sediment mélange.