TY - JOUR
T1 - Thermophysical properties and phase diagrams in the system MgO–SiO
2
–FeO at upper mantle and transition zone conditions derived from a multiple-Einstein method
AU - Jacobs, Michael H.G.
AU - Schmid-Fetzer, Rainer
AU - van den Berg, Arie P.
PY - 2019/5/1
Y1 - 2019/5/1
N2 -
We applied a lattice vibrational technique, based on representing the vibrational density of states with multiple-Einstein frequencies, to determine consistency of data on thermophysical properties and phase diagrams in the system MgO–FeO–SiO
2
. We present analyses of these data in the temperature range between 0 and 2000 K and pressure range between 0 and 20 GPa. The result is a database containing phases relevant to the Earth upper mantle and transition zone. We show that consistency of different datasets associated with the dissociation of the ringwoodite form of Fe
2
SiO
4
depends on the crucible material that has been used to perform partitioning experiments between ringwoodite and ferropericlase, and that this results in different phase diagrams for FeSiO
3
and the post-spinel part of Mg
2
SiO
4
–Fe
2
SiO
4
. We show that the existence of a phase field coesite + ringwoodite in the phase diagram of FeSiO
3
is possible and that it might be used to fine-tune pressure scales. We demonstrate that the phase boundary between coesite and quartz is very sensitive to the low-temperature heat capacity of coesite and that heat capacity data of β-quartz are too large to be reconciled with the phase boundary between β-quartz and coesite. We compare our results with seismic data associated with the 410 km seismic discontinuity.
AB -
We applied a lattice vibrational technique, based on representing the vibrational density of states with multiple-Einstein frequencies, to determine consistency of data on thermophysical properties and phase diagrams in the system MgO–FeO–SiO
2
. We present analyses of these data in the temperature range between 0 and 2000 K and pressure range between 0 and 20 GPa. The result is a database containing phases relevant to the Earth upper mantle and transition zone. We show that consistency of different datasets associated with the dissociation of the ringwoodite form of Fe
2
SiO
4
depends on the crucible material that has been used to perform partitioning experiments between ringwoodite and ferropericlase, and that this results in different phase diagrams for FeSiO
3
and the post-spinel part of Mg
2
SiO
4
–Fe
2
SiO
4
. We show that the existence of a phase field coesite + ringwoodite in the phase diagram of FeSiO
3
is possible and that it might be used to fine-tune pressure scales. We demonstrate that the phase boundary between coesite and quartz is very sensitive to the low-temperature heat capacity of coesite and that heat capacity data of β-quartz are too large to be reconciled with the phase boundary between β-quartz and coesite. We compare our results with seismic data associated with the 410 km seismic discontinuity.
KW - Anharmonicity
KW - Elasticity
KW - Equation of state
KW - Pressure scale
KW - Vibrational density of states
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U2 - 10.1007/s00269-018-01020-y
DO - 10.1007/s00269-018-01020-y
M3 - Article
AN - SCOPUS:85060340434
SN - 0342-1791
VL - 46
SP - 513
EP - 534
JO - Physics and Chemistry of Minerals
JF - Physics and Chemistry of Minerals
IS - 5
ER -