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

We investigate, by means of laboratory analogues, the fluid dynamics o f magma hybridisation caused by the intrusion of felsic magma into a m afic magma chamber. The 'input' felsic magma is modelled by a cold, lo w density fluid and the 'resident' mafic magma by a layer of fluid wax close to its solidification point. The cold, rising input drives conv ection and solidification in the resident fluid, and the solidificatio n causes significant perturbations to an otherwise simple input flow, greatly enhancing mixing and mingling between the two model magmas. Th e dimensionless parameters controlling the evolution of the system are determined and different morphologies of the solid mass fit into clea rly defined fields in the parameter space. The most important implicat ion of the experiments is that the freezing of mafic chambers due to f elsic intrusion may give rise to intense hybridization of large volume s of magma. This potentially important mechanism for hybridization has , to date, received little attention in the literature. (C) 1998 Elsev ier Science B.V. All rights reserved.