Publication Date
11-15-2017
Department
Ames Laboratory; Physics and Astronomy
Campus Units
Physics and Astronomy, Ames Laboratory
Report Number
IS-J 9482
DOI
10.1016/j.epsl.2017.08.032
Journal Title
Earth and Planetary Science Letters
Volume Number
478
First Page
40
Last Page
45
Abstract
The highest pressure form of the major Earth-forming mantle silicate is MgSiO3 post-perovskite (PPv). Understanding the fate of PPv at TPa pressures is the first step for understanding the mineralogy of super-Earths-type exoplanets, arguably the most interesting for their similarities with Earth. Modeling their internal structure requires knowledge of stable mineral phases, their properties under compression, and major element abundances. Several studies of PPv under extreme pressures support the notion that a sequence of pressure induced dissociation transitions produce the elementary oxides SiO2 and MgO as the ultimate aggregation form at ∼3 TPa. However, none of these studies have addressed the problem of mantle composition, particularly major element abundances usually expressed in terms of three main variables, the Mg/Si and Fe/Si ratios and the Mg#, as in the Earth. Here we show that the critical compositional parameter, the Mg/Si ratio, whose value in the Earth's mantle is still debated, is a vital ingredient for modeling phase transitions and internal structure of super-Earth mantles. Specifically, we have identified new sequences of phase transformations, including new recombination reactions that depend decisively on this ratio. This is a new level of complexity that has not been previously addressed, but proves essential for modeling the nature and number of internal layers in these rocky mantles.
DOE Contract Number(s)
AC02-07CH11358
Language
en
Department of Energy Subject Categories
58 GEOSCIENCES; 79 ASTRONOMY AND ASTROPHYSICS
Publisher
Iowa State University Digital Repository, Ames IA (United States)
Included in
Astrophysics and Astronomy Commons, Cosmochemistry Commons, Geochemistry Commons, Mineral Physics Commons, Physics Commons