Applications of mercury stable isotopes for tracing volcanism in the geologic record

Mercury (Hg) enrichments in ancient sediments have been used as a proxy of volcanism, especially large igneous province (LIP) eruptions. However, considering the existence of other potential Hg sources besides volcanoes and the diverse factors (e.g., organic matters, clay minerals, sulfide minerals and Fe oxides) that can affect Hg sequestration, there are considerable uncertainties to simply regard sedimentary Hg anomalies as signatures of volcanic activities. Mercury stable isotopes, a promising tool for tracing the origins and transformations of Hg, have been increasingly used for determining the causes of Hg spikes and understanding the geochemical behavior of Hg in the geologic record. To date, lots of researches have applied Hg concentrations and Hg isotopes to identify LIP volcanisms linking with significant geological events such as mass extinctions, ocean anoxic events and other environmental perturbations that mainly occurred in the Phanerozoic. However, the results in previous studies clearly show that not all Hg enrichments are derived from volcanic inputs, which emphasize the need for more caution in using Hg as a fingerprint of volcanism. With a better understanding of Hg isotopes in the future, there will be important implications for Hg isotopes to reconstruct volcanic activities in the rock records and their impacts on biological evolution.