MINGLING IN MAFIC MAGMA CHAMBERS REPLENISHED BY LIGHT FELSIC INPUTS: FLUID DYNAMICAL EXPERIMENTS

Abstract

We investigate, by means of laboratory analogues, the fluid dynamics of magma hybridisation caused by the intrusion of felsic magma into a mafic magma chamber. The 'input' felsic magma is modelled by a cold, low density fluid and the 'resident' mafic magma by a layer of fluid wax close to its solidification point. The cold, rising input drives convection and solidification in the resident fluid, and the solidification causes significant perturbations to an otherwise simple input flow, greatly enhancing mixing and mingling between the two model magmas. The dimensionless parameters controlling the evolution of the system are determined and different morphologies of the solid mass fit into clearly defined fields in the parameter space. The most important implication of the experiments is that the freezing of mafic chambers due to felsic intrusion may give rise to intense hybridization of large volumes of magma. This potentially important mechanism for hybridization has, to date, received little attention in the literature.