Surface chemistry allows for abiotic precipitation of dolomite at low temperature

Significance Abundant in the geologic record, but scarce in modern environments below 50° C, the mineral dolomite is used to interpret ancient fluid chemistry, paleotemperature, and is a major hydrocarbon reservoir rock. Because laboratory synthesis of abiotic dolomite had been unsuccessful, chemical mechanisms for precipitation are poorly constrained, and limit interpretations of its occurrence. Here we report the abiotic synthesis of dolomite at 25° C, and demonstrate that carboxylated surfaces on organic matter catalyze precipitation through complexation between carboxyl groups and Mg2+ , removing water to make Mg2+ available for dolomite precipitation. This mechanism is consistent with dolomite formation in depositional environments rich in organic matter. Our experimental protocol provides opportunities for calibrating conditions of low-temperature dolomite formation throughout the geologic record.