ISSN:
1432-0967
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
Notes:
Abstract Experiments were performed in the three phase system high-silica rhyolite melt+low-salinity aqueous vapor+hydrosaline brine, to investigate the partitioning equilibria for copper in magmatic-hydrothermal systems at 800° C and 1 kbar, and 850° C and 0.5 kbar. Daqm/mlt Cu and apparent equilibrium constants, Kaqm/mlt Cu,Na, between the aqueous mixture (aqm=quenched vapor+brine) and the silicate melt (mlt) are calculated. Daqm/mlt Cu increases with increasing aqueous chloride concentration and is a function of pressure. Kaqm/mlt Cu,Na=215(±73) at 1 kbar and 800° C and Kaqm/mlt Cu,Na=11(±6) at 0.5 kbar and 850°C. Decreasing pressure from 1 to 0.5 kbar lowers Kaqm/mlt Cu,Na by a factor of approximately 20. Data revealed no difference in Kaqm/mlt Cu,Na or Daqm/mlt Cu as a function of the melt aluminium saturation index. Within the 2-phase field the Kaqm/mlt Cu,Na show no variation with total aqueous chloride, indicating that copper-sodium exchange between the vapor, brine and silicate melt is independent of the mass proportion of vapor and brine. Model copper-sodium apparent equilibrium constants for the hydrosaline brine and the silicate melt revealed a negative dependence on pressure. Model apparent equilibrium constants for copper-sodium exchange between the brine and vapor were close to unity at 1 kbar and 800° C.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004100050104
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