Fluid inclusion calibration of clumped-isotope solid-state reordering in dolomite: Implication for thermal history reconstruction in deeply buried reservoirs

Carbonate clumped -isotope ( A 47 ) paleothermometry offers a novel means of reconstructing the paleoburial temperature of carbonate rocks. However, the application of this thermometer is challenging when applied to thermal history reconstruction in deeply buried reservoirs, due to potential modifications to the A 47 value of carbonate mineral by C-O bond solid-state reordering. Although four reordering models have been proposed based on high -temperature laboratory experiments, the operation of A 47 reordering under geological conditions is still not fully understood. The A 47 and homogenization temperature ( T h ) of primary fluid inclusions trapped within the dolomite cements from the Central Sichuan Basin, China were measured. The A 47 evolution of the dolomite samples were predicted with the four published reordering models under the constraints of independent thermal history reconstruction and T h -derived initial A 47 values. The results of this study demonstrate that T h of fluid inclusion can be a valid indication of precipitation temperature of dolomite cements even when the samples experience peak burial temperature ( T max ) up to -200-240 degrees C. It also indicate current reordering models have overall equivalent ability for A 47 prediction although there are discernible differences between sample types across different models. Both T max and model -determined threshold behavior of A 47 reordering control the reordering pathway for model prediction, and the threshold behaviors of our dolomite samples were explored under geological conditions. In this framework, the threshold temperature (-190 degrees C) for detectable dolomite reordering may be substantially higher than previous model predictions (120-150 degrees C). Moreover, the temperature at which the A 47 temperature fully equilibrates with the ambient temperature during sequential burial could exceed 240-250 degrees C. These threshold behaviors of bond reordering in dolomite under geological conditions are different from previous model calculations. Therefore, T max and threshold temperatures of A 47 reordering for different models should be considered when reconstructing thermal history based clumped -isotope solid-state reordering modeling. Our findings have significant implications for understanding the dolomite clumped -isotope reordering process and reconstructing the thermal history of deeply buried carbonate rocks.