Rheological Properties of the Magmas Feeding the Campi Flegrei Caldera (Italy) and Their Influence on Mixing Processes

Abstract

AbstractThis chapter reviews and discusses the main rheological and physical properties and models (viscosity and density) of the melts feeding the Campi Flegrei caldera volcanism. Viscosity and density control flow and diffusion, and thus multicomponent convection and chemical mobility in the magma chamber. These, in turn, are thought to constrain magma mixing processes in the system. Our main goal is to summarise and analyse mixing experiments using natural volcanic products of the caldera as starting material. The mixing experiments have been performed using different devices (Taylor-Couette and centrifuge). Results show how easily Campi Flegrei caldera melts may mix. They confirm that different chemical elements homogenise in the melt at differing rates, providing an innovative quantitative approach, the estimation of a new parameter for measuring multi-component diffusion in magmas: Relaxation of Concentration Variance or Concentration Variance Decay. This enables the measurement of mobility for all elements present in the melt simultaneously. Comparing experimental and natural data clearly confirm the unavoidability of mixing during the replenishment history of the caldera reservoir(s).