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Preheated shock experiments in the molten CaAl 2 Si 2 O 8 ‐CaFeSi 2 O 6 ‐CaMgSi 2 O 6 ternary: A test for linear mixing of liquid volumes at high pressure and temperature
Author(s) -
Thomas Claire W.,
Asimow Paul D.
Publication year - 2013
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/jgrb.50269
Subject(s) - silicate , mole fraction , ternary operation , thermodynamics , mixing (physics) , partial molar property , molar volume , mineralogy , volume (thermodynamics) , chemistry , materials science , analytical chemistry (journal) , physics , organic chemistry , quantum mechanics , computer science , programming language
Abstract We performed 17 new shock wave experiments on preheated (1673 K) hedenbergite liquid (CaFeSi 2 O 6 ) and two model basalt liquids (an equimolar binary mix of CaAl 2 Si 2 O 8 + CaFeSi 2 O 6 and an equimolar ternary mix of CaAl 2 Si 2 O 8 + CaFeSi 2 O 6 +CaMgSi 2 O 6 ) in order to determine their equations of state (EOS). Ambient pressure density measurements on these and other Fe‐bearing silicate liquids indicate that FeO has a partial molar volume that is highly dependent on composition, which leads to large errors in estimates of the densities of Fe‐bearing liquids at ambient pressure based on an ideal mixing of any fixed set of end‐member liquids. We formulated a series of mixing tests using the EOS determined in this study to examine whether ideal mixing of volumes might nevertheless suffice to describe the ternary system CaAl 2 Si 2 O 8 ‐CaFeSi 2 O 6 ‐CaMgSi 2 O 6 at high temperature and pressure. The ideal mixing null hypothesis is rejected; compositional variations in partial molar volume of FeO appear to extend to high pressure. Only densities of Fe‐bearing liquid mixtures with oxide mole fraction of FeO less than 0.06 can be adequately approximated using an ideal solution.