Subject: AGU Abstract


What Patterns and Lengthscales of Heterogeneity do we
Expect in D"?

Paul J. Tackley and Shunxing Xie

It now seems clear that  D" has both compositional and
thermal components, with considerable lateral variation
in each. Seismic observations have been invoked to
suggest lateral heterogeneity on a wide range of
lengthscales, from O(100 km) to O(1000s km). Here, 3-D
numerical simulations with temperature- and depth-
dependent viscosity are used to characterize the
two-dimensional patterns and lengthscales of thermal and
chemical heterogeneity which can arise in a convecting
mantle with a chemically distinct layer at the CMB.
Chemical variations are assumed to arise either from
primordial layering, separation of different slab
components, and/or reactions with the core. Many
questions can be addressed with such an approach, most of
which relate to the relationship (e.g., correlation) and
interaction between up/downwellings, and the thickness
and variability of the thermal and chemical boundary
layers.