Rj. Bakker et Lw. Diamond, Determination of the composition and molar volume of H2O-CO2 fluid inclusions by microthermometry, GEOCH COS A, 64(10), 2000, pp. 1753-1764
H2O-CO2 fluid inclusions are common in nature but their accurate analysis b
y microthermometry has been hindered by insufficient characterisation of th
e fluid properties along the solvus (high temperature miscibility boundary)
of the system. Thus some of the previous methods of calculating fluid incl
usion composition (x) and molar volume (V) have relied on notoriously unrel
iable optical estimates of phase volume fractions. Although the T-V-x prope
rties of the solvus can be modelled thermodynamically from equations of sta
te, a review shows that none of the published equations are accurate enough
to be useful in fluid inclusion microthermometry. Therefore, the available
experimental data have been used to construct a new V-x diagram, contoured
for phase transition temperatures and phase volume fractions. This diagram
allows the bulk composition and molar volume of individual fluid inclusion
s to be determined accurately from two microthermometric measurements: the
temperature of partial homogenisation of the carbonic phases (in the presen
ce of excess aqueous liquid), and the temperature of total homogenisation.
Copyright (C) 2000 Elsevier Science Ltd.