Laboratory calibration of the calcium carbonate clumped isotope thermometer in the 25-250 °C temperature range

The calibration lines of both experimental approaches overlap and agree in the slopes with theoretical estimates and with other calibration experiments in which carbonates were reacted with phosphoric acid at temperatures above 70 °C. Our study suggests a universal Δ47-T calibration (T in K, Δ47 in ‰):Δ47=0.98(±0.01)·(-3.407·109/T4+2.365·107/T3-2.607·103/T2-5.880/T)+0.293(±0.004)This new Δ47-T calibration (given in the absolute reference frame), that extends the experimentally calibrated temperature range for clumped isotopes to 250 °C, can be applied to carbonates that grew at intermediate temperatures (20-250 °C).