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The distribution of Helium in the intracluster medium (ICM) permeating galaxyclusters is not well constrained due to the very high plasma temperature.Therefore, the plasma is often assumed to be homogeneous. A non-uniform Heliumdistribution can however lead to biases when measuring key cluster parameters.This has motivated one-dimensional models that evolve the ICM compositionassuming that the effects of magnetic fields can be parameterized or ignored.Such models for non-isothermal clusters show that Helium can sediment in thecluster core leading to a peak in concentration offset from the cluster center.The resulting profiles have recently been shown to be linearly unstable whenthe weakly-collisional character of the magnetized plasma is considered. Inthis paper, we present a modified version of the MHD code Athena, which makesit possible to evolve a weakly-collisional plasma subject to a gravitationalfield and stratified in both temperature and composition. We thoroughly testour implementation and confirm excellent agreement against several analyticalresults. In order to isolate the effects of composition, in this initial studywe focus our attention on isothermal plasmas. We show that plasmainstabilities, feeding off gradients in composition, can induce turbulentmixing and saturate by re-arranging magnetic field lines and alleviating thecomposition gradient. Composition profiles that increase with radius lead toinstabilities that saturate by driving the average magnetic field inclinationto roughly $45^{\circ}$. We speculate that this effect may alleviate the coreinsulation observed in homogeneous settings, with potential consequences forthe associated cooling flow problem.

Local Simulations of Instabilities Driven by Composition Gradients in the ICM