We precipitated a suite of carbonates under controlled
conditions in the laboratory to assess the temperature
dependence of the 13C–18O clumping in the gap between
low- and high-temperature calibrations, spanning temperatures
from 20 C to 250 C and aimed to significantly
reduce the uncertainty in this temperature range. In order
to ensure reproducibility and representativeness, carbonates
were precipitated using two different methods. In
the first setup, minerals precipitated from an isotopically
equilibrated CaCO3 solution at atmospheric pressure,
whereas minerals in the second experiment were precipitated
from a solution prepared by mixing equilibrated
solutions of CaCl2 and NaHCO3 in a pressurized reaction