Dynamics and time evolution of a shallow plumbing system: The 1739 and 1888–90 eruptions, Vulcano Island, Italy

In this work we analyze the morphology of latitic enclaves occurring in the rhyolitic lava flow of Pietre Cotte (Island of Vulcano, Italy). We show that enclave morphology is a feature inherited from the shallow plumbing system of the volcano during the invasion of the latitic magma into the rhyolitic magma. The complexity of enclave morphology is quantified by fractal analyses. Using the empirical relationship given by Perugini et al. (2005) relating the fractal dimension and viscosity ratio, the range of viscosity ratios that developed during the injection of the latitic magma into the rhyolitic one is estimated. Thermodynamical and rheological modeling indicates that the most plausible scenario to explain the variability of observed viscosity ratios is represented by a plumbing system where a large volume of latitic magma intruded a smaller volume of rhyolitic magma. The comparison of volume proportions of magmas on the outcrop with those estimated by the modeling allows us to infer that most of the latitic magma remained in the plumbing system after the ending of the 1739 eruptive cycle. The strong similarity of compositions from the Pietre Cotte lava flow and products erupted during the last volcanic activity of Vulcano (1888-1890) is interpreted as the reactivation of the latitic magma, that possibly evolved through fractional crystallization to produce trachy-rhyolitic compositions, during the 1888-1890 eruptive cycle. We suggest that the methodological approach presented here can represent a further tool for hazard mitigation in volcanic areas. In particular, it allows obtaining information about the dynamics of plumbing systems of active volcanoes and their time evolution.