Fluid-inclusion technique for determining maximum temperature in calcite and its comparison to the vitrinite reflectance geothermometer; with Suppl. Data 90-22

Theory, laboratory experiments, and empirical observation suggest that many aqueous fluid inclusions in calcite reequilibrate during overheating, and therefore some homogenization temperatures (T (sub h) ) record a temperature close to the maximum reached by the rock. This characteristic suggests that aqueous fluid inclusions in calcite can be used to establish maximum temperature (T (sub peak) ). To test this hypothesis, we have compiled fluid inclusion T (sub peak) , mean random vitrinite reflectance (R (sub m) ), and present-day T (sub peak) from 46 diverse geologic systems that have been at T (sub peak) from 10 (super 4) to 10 (super 6) yr. Present T (sub peak) ranged from 65 to 345 degrees C, T (sub h) modes and means ranged from 59 to 350 degrees C, and R (sub m) data ranged from 0.4% to 4.6%, spanning the temperature and thermal maturity range associated with burial diagenesis, hydrothermal alteration, and low-grade metamorphism.Plots of T (sub h) and T (sub peak) data for systems thought to be currently at maximum temperature demonstrate close agreement between T (sub h) and present T (sub peak) in sedimentary basins. Although caution should be applied, the relation suggests that T (sub h) of aqueous fluid inclusions in calcite may be a useful measure of maximum temperature. This study also compares T (sub h) to mean random vitrinite reflectance (R (sub m) ) to offer further support for the use of T (sub h) as a measure of T (sub peak) , and to provide a better understanding of R (sub m) . T (sub h) correlates well with R (sub m) and results in a curve similar to R (sub m) vs. T (sub peak) calibrations determined by other workers. The strong correlation (correlation coefficient r = 0.93) between T (sub peak) and R (sub m) in these systems suggests that maximum temperature is the major control on thermal maturation.