The incomplete Evros ophiolites in NE Greece form a NE-SW-oriented
discontinuous belt in the Alpine orogen of the north Aegean. Field data,
petrology and geochemistry are presented here for the intrusive section
and associated mafic dykes of these ophiolites. Bodies of high-level
isotropic gabbro and plagiogranite in the ophiolite suite are cross-cut
by NE-SW-trending boninitic and tholeiitic-boninitic affinity dykes,
respectively. The dykes fill tensile fractures or faults, which implies
dyke emplacement in an extensional tectonic regime. The
tholeiitic-transitional boninitic gabbro is REE- and HFS-depleted
relative to N-MORB, indicating derivation from melting of a refractory
mantle peridotite source. Associated boninitic dykes are slightly
LREE-enriched, showing mineral and whole-rock geochemistry similar to
the gabbro. The plagiogranite is a strongly REE-enriched high-silica
trondhjemite, with textures and composition typical for an oceanic crust
differentiate. Plagiogranite-hosted tholeiitic and transitional
boninitic dykes are variably REE-enriched. Geochemical modelling
indicates origin of the plagiogranite by up to 75% fractional
crystallization of basaltic magma similar to that producing the
associated tholeiitic dykes. All mafic rocks have high LILE/HFSE ratios
and negative Ta-Nb-Ti and Ce anomalies, typical for subduction
zone-related settings. The mafic rocks show a similar trace-element
character to the mafic lavas of an extrusive section in Bulgaria,
suggesting they both form genetically related intrusive and extrusive
suites of the Evros ophiolites. The field occurrence, the structural
context, the petrology and geochemical signature of the studied magmatic
assemblage provide evidence for its origin in a proto-arc (fore-arc)
tectonic setting, thus tracing the early stages of the tectono-magmatic
evolution of Jurassic arc-marginal basin system that has generated the
supra-subduction type Evros ophiolites.