TY - JOUR
T1 - The solubility and oxidation state of nickel in silicate melt at low oxygen fugacities
T2 - Results using a mechanically assisted equilibration technique
AU - Dingwell, D. B.
AU - O'Neill, H. St C.
AU - Ertel, W.
AU - Spettel, B.
N1 - Copyright:
Copyright 2014 Elsevier B.V., All rights reserved.
PY - 1994/4
Y1 - 1994/4
N2 - The solubility of Ni in a silicate melt has been measured using a new, mechanically assisted equilibration technique over a wide range of controlled f{hook}O2 values. The melt composition corresponds to the 1 atm eutectic in the system CaAl2Si2O8-CaMgSi2O6 + 10 wt% CaO. The experiments were performed at 1300°C and over an f{hook}O2 range of 10-8.5 to 10-13.75, and over a temperature range of 1270 to 1390°C at a constant gas mixing ratio ( CO2 CO = 1:1). The experiment consists of a sample of melt contained within a crucible of Ni metal and held in a 1 atm gas mixing furnace. A Ni spindle is entered into the sample from above and continuously rotated at a constant angular velocity using a viscometer head. The stirring of the sample serves to accelerate the approach to equilibrium between the liquid sample and the metal crucible (and spindle). This arrangement allows relatively rapid equilibration of Ni content following changes to higher or lower f{hook}O2 values. Samples of the melt may be taken at any time for analysis and thus the equilibrium solubility of Ni in the silicate melt may be determined from unambiguous experimental reversals. The Ni contents of samples, analysed both by INAA and by ICP-AES, range from 25 to 5300 ppm. The data presented in this paper indicate that the oxidation state of Ni in the investigated melt is Ni2+ over the entire range of f{hook}O2 investigated. This conclusion contrasts with recent reports in the literature of an inflection in the f{hook}O2 dependence of Ni solubility, which has been interpreted as solution of neutral Ni at low f{hook}O2 (Morse et al., 1991; Colson, 1992; Ehlers et al., 1992). We also present data for the temperature dependence of Ni solubility in the investigated melt. The solubility decreases with increasing temperature at constant f{hook}O2. The present results are in good agreement with the metal-loop-equilibration experiments reported by Holzheid et al. (1994).
AB - The solubility of Ni in a silicate melt has been measured using a new, mechanically assisted equilibration technique over a wide range of controlled f{hook}O2 values. The melt composition corresponds to the 1 atm eutectic in the system CaAl2Si2O8-CaMgSi2O6 + 10 wt% CaO. The experiments were performed at 1300°C and over an f{hook}O2 range of 10-8.5 to 10-13.75, and over a temperature range of 1270 to 1390°C at a constant gas mixing ratio ( CO2 CO = 1:1). The experiment consists of a sample of melt contained within a crucible of Ni metal and held in a 1 atm gas mixing furnace. A Ni spindle is entered into the sample from above and continuously rotated at a constant angular velocity using a viscometer head. The stirring of the sample serves to accelerate the approach to equilibrium between the liquid sample and the metal crucible (and spindle). This arrangement allows relatively rapid equilibration of Ni content following changes to higher or lower f{hook}O2 values. Samples of the melt may be taken at any time for analysis and thus the equilibrium solubility of Ni in the silicate melt may be determined from unambiguous experimental reversals. The Ni contents of samples, analysed both by INAA and by ICP-AES, range from 25 to 5300 ppm. The data presented in this paper indicate that the oxidation state of Ni in the investigated melt is Ni2+ over the entire range of f{hook}O2 investigated. This conclusion contrasts with recent reports in the literature of an inflection in the f{hook}O2 dependence of Ni solubility, which has been interpreted as solution of neutral Ni at low f{hook}O2 (Morse et al., 1991; Colson, 1992; Ehlers et al., 1992). We also present data for the temperature dependence of Ni solubility in the investigated melt. The solubility decreases with increasing temperature at constant f{hook}O2. The present results are in good agreement with the metal-loop-equilibration experiments reported by Holzheid et al. (1994).
UR - http://www.scopus.com/inward/record.url?scp=0028193943&partnerID=8YFLogxK
U2 - 10.1016/0016-7037(94)90428-6
DO - 10.1016/0016-7037(94)90428-6
M3 - Article
AN - SCOPUS:0028193943
SN - 0016-7037
VL - 58
SP - 1967
EP - 1974
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
IS - 8
ER -