Homogenization temperatures of fluid inclusions trapped in calcite crystals may change with increased heating beyond the homogenization temperature. Fluid inclusions trapped in calcite during basin subsidence will tend to yield homogenization temperatures approaching maximum burial temperatures. Diagenetic studies that depend on these data will be biased.
Coarse crystalline calcite containing saline fluid inclusions was used to examine the influence of increased temperatures and pressures on measured homogenization temperatures. Stepped heating experiments were conducted at 1 atm, over a temperature range of 90 to 245 °C, along with hydrothermal experiments at confining pressures of 173 and 691 bar and temperatures of 160, 250, and 350 °C. In all cases, significant increases in the homogenization temperatures of the inclusion population were recorded.
Presumably, stresses generated during heating of the fluid inclusions exceeded the combined strength of the calcite crystal and the external pore pressure and thus caused fluid-inclusion stretching. Size is a secondary factor that controls fluid-inclusion reequilibration.