  Sharp edges in X-ray surface brightness with continuous gas pressure called
cold fronts have been often found in relaxed galaxy clusters such as Abell 496.
Models that explain cold fronts as surviving cores of head-on subcluster
mergers do not work well for these clusters and competing models involving gas
sloshing have been recently proposed. Here, we test some concrete predictions
of these models in a combined analysis of density, temperature, metal
abundances and abundance ratios in a deep Chandra exposure of Abell 496. We
confirm that the chemical discontinuities found in this cluster are not
consistent with a core merger remnant scenario. However, we find chemical
gradients across a spiral "arm" discovered at 73 kpc north of the cluster
center and coincident with the sharp edge of the main cold front in the
cluster. Despite the overall SN Ia iron mass fraction dominance found within
the cooling radius of this cluster, the metal enrichment along the arm,
determined from silicon and iron abundances, is consistent with a lower SN Ia
iron mass fraction (51% +- 14%) than that measured in the surrounding regions
(85% +- 14%). The "arm" is also significantly colder than the surroundings by
0.5-1.6 keV. The arm extends from a boxy colder region surrounding the center
of the cluster, where two other cold fronts are found. This cold arm is a
prediction of current high resolution numerical simulations as a result of an
off-center encounter with a less massive pure dark matter halo and we suggest
that the cold fronts in A496 provide the first clear corroboration of such
model, where the closest encounter happened ~ 0.5 Gyr ago. We also argue for a
possible candidate dark matter halo responsible for the cold fronts in the
outskirts of A496.
