Formation of dolomite at 40-80 °C in the Latemar carbonate buildup, Dolomites, Italy, from clumped isotope thermometry

The temperature of formation of replacement dolomite and delta O-18(H2O) of dolomitizing fluid in the Latemar carbonate buildup, Dolomites, Italy, were estimated independently from carbonate clumped isotope thermometry. Dolomite formed at 42-72 +/- 9-11 degrees C (+/- 2 standard deviations, SD) from fluid with delta O-18(H2O) that averages -0.3% +/- 3.3% (Vienna standard mean ocean water; +/- 2 SD). The estimated temperature and delta O-18(H2O) are similar to those of modern diffuse flow fluids at mid-ocean ridges, the kind of fluid that has been proposed previously as the dolomitizing fluid in the Latemar buildup, based on the trace element compositions of dolomite. Calcite in limestone preserves original d18O, but records clumped isotope temperatures, 44-76 +/- 9-11 degrees C (+/- 2 SD), that are higher than those at which the limestone formed. Temperature recorded by calcite, but not delta O-18, was likely reset during dolomitization. Clumped isotope thermometry has great potential for application to studies of burial and diagenesis by retrieving independent estimates of temperature and delta O-18(H2O) with uncertainties as low as +/- 5 degrees C (+/- 2 standard errors, SE) and +/- 0.75% (+/- 2 SE), respectively, from a single stable isotope analysis of a carbonate mineral.