The melting curve of gold, silver, and copper to 60‐Kbar pressure: A reinvestigation

Abstract

The melting curves of gold, silver, and copper were redetermined by differential thermal analysis to 60-kbar pressure. The experiments were carried out with an end-loaded piston-cylinder high-pressure apparatus using a recently developed low-friction cell. Significant improvements in the precisionof the temperature determination above 40 kbar were obtained.We observed a slight lowering of the melting temperature of copper when graphite capsules were used, which is consistent with our past experience and indicates some alloying of the copper and carbon.The following parabolic functions (T m = a 3 + [a2(P-a•)]l/2 10 8a 2) were fitted to the raw data, and •he data corrected for the influence of pressure on the emf of the thermocouples (in parenthesis): gold T m = -2439.28+[0.262850x10-4(p+322.668)]l•2 x 2628.50 (T m = -1773.88+[0.309303x10-4(p+249.167)]l/2 x 3093.03); silver, T m =-261.759+[0.661750x10 -4 (P+99.085)]1/2 x 6617.50 (T m = -194.145+[0.668583 x 10-4(p+89.347)]1/2 x 6685.83); and copper, Tm= 129.171+[0.134011x10-3(p+122.305)]l/2 x 134.011 (T m = 199.265+[0.135218x10-3(P+105.960)]l/2 x 135.218).The precision of the pressure measurements at the 90% confidence level is 0.3+-0.5 kbar. The precision in the temperature is e5øC.

Global equation of state for copper

“…6, the current work and the previous Sesame EOS are compared against melting point data. The current work shows good agreement with lowpressure melt data [27] as well as the newer multianvil data by Brand [28], but not with the higher pressure laser-heated diamond-anvil data by Japel et al [29]. However, this high-pressure data is inconsistent with its own reported error bars and fails to extrapolate to the correct ambient melting temperature.…”

“…Pressure (GPa) Figure 6. Melting temperature as a function of pressure for current work (solid line), SESAME 3336 table (dashed) along with data from Mirwald and Kennedy [27], Brand et al [28], and Japel et al [29]. Fig.…”

H2O-rich island arc low-K tholeiite magma inferred from Ca-rich plagioclase-melt inclusion equilibria

“…The temperature was measured by two W-Re5/26 thermocouples within 1.0 cm of the sample site, and calibrated against the melting point of gold (1070°C at 0.25 GPa: Mirwald and Kennedy, 1979). The temperature of the charges was kept within 10°C of target during the experiments.…”

Experimental synthesis of isochemical kelyphite — a preliminary report

“…An R-type thermocouple was used without a correction for the effect of pressure on EMF. Pressure calibration was made according to the melting point of gold (1.65 GPa at 1154°C, Mirwald and Kennedy, 1979) and the transition of orthoenstatite to protoenstatite (0.85 GPa at 1400°C, Ohi et al, 2010). Pressure was first elevated to the desired level, and then the temperature was raised to its desired value.…”