Tracing silicate weathering using lithium isotopes: from the lab, to the field and the past

Silicate weathering is the primary mechanism by which atmospheric CO2 is removed and stored for long periods of time. It is therefore a key biogeochemical mechanism in controlling the present and past climate, and may also have a significant role in future carbon dioxide removal. However, tracing silicate weathering is difficult in the modern environment, and have proven particularly challenging during geological history.

Lithium isotopes appear to be a tracer with significant potential in this field, because they only trace silicate weathering, and are apparently unaffected by biological processes.

Here we will present the behaviour of Li isotopes during weathering experiments and in the field. We will then demonstrate how this relates to Li isotope excursions through climatic events in Earth history, and what Li isotope data tell us about the operation of the “weathering thermostat” – the purported temperature-dependent stabilisation mechanism of the climate.