When magmas do not interact: paired Roman-age activity revealed by tephra studies at Stromboli volcano

Detailed stratigraphic and geochemical studies were carried out on remnants of the partially collapsed Pizzo-o-Sopra-la-Fossa (Pizzo) scoria cone, which represents the best viewpoint for observing the present-day activity on top of the Stromboli volcano, Italy. The main outcrop is above the active craters and is strongly altered by acid fumarolic gases; for this reason, the Pizzo activity has previously been poorly studied (for age and composition).We focus mainly on the well-preserved Le Croci fallout succession. We show that the Pizzo activity occurred in the Roman age (∼2.4–1.8 ka) and was fed by two compositionally and genetically distinct magma groups, each occupying a separate reservoir. Shoshonitic basalts (Pizzo-SHO) were stored at lower depths than high-K basalts to high-K basaltic andesites (Pizzo-HKCA). Although Pizzo- SHO and Pizzo-HKCA magmas were affected by multiple mafic magma inputs (with different dynamics as reflected in variable mineral zoning), they did not interact with each other.