Mafic adakite-like magmatism at the Cretaceous–Paleogene boundary from the Northwest Rhodopes, Bulgaria

Abstract

New findings of monzogabbro and gabbro-monzodiorite dykes aged 62 Ma reveal the existence of magmatism in the gap between termination of the Late Cretaceous subduction-related and start of the early–middle Eocene post-collisional magmatic stages in the Rhodope Massif. Their geochemical compositions strongly resemble adakitic signature as well as hornblende and epidote geobarometers predicted lower crustal conditions (20–30 km depth) of crystallization. Detailed studies on U-Pb geochronology of zircon populations and Sr-Nd-Hf isotopic compositions point to significant assimilation of the local basement and mixing of mantle-crust sources in the regime of a thickened crust.