Petrology of the 31.6 Ma Central Rhodope Perelik monotonous intermediate ignimbrite eruption

Abstract

Volcanism during the Priabonian–Oligocene times (35–27 Ma) in the Rhodope Massif produced large volume of shoshonitic and calcalkaline lavas and three large volume silicic ignimbrites and fallout deposits. The youngest of these ignimbrites, named here as Perelik ignimbrite (PI), consists of three areas, previously described as three separate ignimbrite units, namely Bratsigovo-Dospat, Perelik and Kotili-Vitina. The ~300 m thick ignimbrites cover an area of 700 km2, 220 km2 and 350 km2, respectively. Our study demonstrates that these ignimbrites have identical ages of ~31.6 Ma and mineral and chemical compositions and are parts of a single large eruption. Based on these data, we suggest that the original areal coverage was much larger, possibly 3000 km2, with magma volume of ~1000 km3. These results classify the Perelik eruption as one of the largest European Oligocene supereruptions These ignimbrites have notably high phenocrystal content (40–50%) and are a relatively homogeneous chemical composition, which are characteristics features of the ‘monotonous intermediate’ ignimbrites. Here, we provide petrographic observations, and chemical and isotopic (Sr, Nd) analyses to explain the P-T conditions of crystallization of these ignimbrites.