The Post-Perovskite Transition and Mineralogical Changes in the Chemically Heterogeneous Lower Mantle

Tuesday, 16 December 2014: 1:40 PM
Sang-Heon Dan Shim1, Yu Ye1, Brent Grocholski2, Shenzhen Xu3, Dane Morgan3, Jiyong Zhao4 and Esen E Alp4, (1)Arizona State University, Tempe, AZ, United States, (2)American Association for the Advancement of Science Arlington, Arlington, VA, United States, (3)Univ of Wisconsin- Madison, Madison, WI, United States, (4)Argonne National Laboratory, Argonne, IL, United States
The discovery of the post-perovskite transition in 2004 has made huge impact on our understanding on the structures and dynamics of the lowermost mantle. For the last 10 years, the post-perovskite transition has been related to major seismic structures in the region, including the D’’ discontinuity, the D’’ anisotropy, and the anti-correlation between the bulk sound speed and shear wave velocity. Whereas the post-perovskite phase appeared to provide a coherent framework to explain many of the major structures, more recent mineral physics studies have revealed that the compositional effects can be significant. High-resolution seismic imaging studies have reported complex structures which cannot be explained by the post-perovskite transition in chemically simple systems. Furthermore, recently proposed mineralogical changes in the lower mantle will affect the properties of post-perovskite and may provide alternative explanations for some seismic structures. In this talk, we will discuss the post-perovskite phase transition and other phase transitions in chemical heterogeneities in the lowermost mantle and their importance in understanding seismic structures. We will also report new data on the spin and oxidation state of iron in mantle silicate which can affect the post-perovskite transition.