Hugoniot equation of state of anorthite glass and lunar anorthosite

Abstract

Twenty-one Hugoniot experiments were conducted on an amorphous material of anorthite composition, in the pressure range 8-120 GPa, using both routine and new methods. Two Hugoniot measurements at about 120 GPa were made on lunar gabbroic anorthosite (Apollo 15,418). Theoretical Hugonicts are constructed for both materials assuming they are disproportionate to their component oxides. These accurately predict the P-p behaviour of the lunar anorthosite Hugoniot at 120 GPa and the anorthite glass Hugoniot above 50GPa, but overestimate the shock temperatures of anorthite glass. The mixed oxide model fails to predict the release paths of either material. We conclude that the mixed oxide model is a good description of the bulk properties of the high-pressure phases of anorthite, but does not represent the actual phases. A significant enrichment of calcic refractory material in the Earth's lower mantle is not precluded by the bulk properties of the anorthite high-pressure phases.

Molecular dynamics studies of CaAl2Si2O8 liquid. Part II: Equation of state and a thermodynamic model

“…13, brackets connected by the dashed-dot curve). The data of Jeanloz and Ahrens are now interpreted (Campbell and Heinz, 1993) to reflect the properties of an amorphized substance and this conclusion along with the data of Boslough et al (1986;solid circles in Fig. 13) leads to the observation that the experimentally determined densities of the liquid and of the glass are identical at pressures in the interval 25-40 GPa.…”

“…13 along with experimental data. Also shown are model q-P isotherms and experimental data describing the Hugoniot of pressure-amorphized (Campbell and Heinz, 1993), initially crystalline-anorthite (CaAl 2 Si 2 O 8 ) from Jeanloz and Ahrens (1980) and anorthite glass from Boslough et al (1986).…”

“…5000 K isotherm ofTable 1) compared to experimental data fromRigden et al (1989) on shocked liquid (six lowest pressure brackets),Asimow and Ahrens (2008) on shocked liquid (four highest pressure brackets),Jeanloz and Ahrens (1980) on shocked crystalline anorthite (three pressure brackets connected by the dashed-dot Hugoniot curve), andBoslough et al (1986) on shocked glass (filled circles). The dashed curves are Rayleigh lines connecting initial and final shock states.…”

Degree of polymerization of the CaAl2Si2O8 aluminosilicate glass

“…2 and Table 1. Figure 2 also depicts the pressure dependence of the relative density for a glass of the same composition according to the data obtained under the plane shock wave compression of the glass [15]. …”

Shock-induced transformations in the system NaAlSiO4?SiO2: a new interpretation

“…If we take 3.74_ 0.10 g/cm 3 as a range of the zero-pressure density of the CaA12Si2Os-rich hollandite (Table 2), the Ko~ and K'o~ range between 196 and 211 GPa and between 2.0 and 2.3 for 70= 1.0+0.5 and Err=0 to 1000 J/g. Boslough et al (1986) calculated the high-pressure equation of state of anorthite through a mixed oxide model as the candidate high-pressure assemblage of CaO in the B2 phase, A1203 corundum and SiO2 stishovite, Ko~ = 227 GPa and K'o~ = 5.1 were given for the candidate with a zero pressure density of 4.07 g/cm 3. These values are in a reasonable agreement with our calculation although Boslough et al (1986) and the present study differ in the high-pressure phases and the zero-pressure density assumed.…”