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Mon, 19 Jul 1999 15:15:07 -0600 |
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Dear Alison,
These low delta 18O values are frequently encountered where there has been
oxygen isotopic equilibration between DIC and water at higher temperatures.
The basic idea is that the equilibrium constant decreases with temperature
and with water dominating the system, precipitating carbonate has lower
delta 18O values with increasing temperature. On a plot of Temp vs delta 18O
of dolomite, curves can be drawn corresponding to the oxygen isotopic
composition of the water. With this diagram, one can estimate temperature
of equilibration if the delta value of the water is known or vice versa.
There are probably more recent citations on the basic concept the but one
often used was L.S. Land (1980) pp 87-110 in SEPM Spec. Pub.28 entitled
CONCEPTS AND MODELS OF DOLOMITIZATION ( Eds. D.H.Zenger, J.B.Dunham,
R.L.Ethington). An example from the Devonian of Western Canada is given by
K.L. Aulstead et al, (1988), Geochim. Cosmochim. Acta 52, pp 1027-1035.
Roy Krouse
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