SOURCES OF MERCURY DURING LARGE IGNEOUS PROVINCE EMPLACEMENT: THE CENTRAL ATLANTIC MAGMATIC PROVINCE AND SIBERIAN TRAPS

Mercury concentrations in the sedimentary record are emerging as an important proxy for ancient volcanic events, including large igneous province (LIP) emplacement. However, few direct constraints exist for LIP Hg emissions, which limits our interpretation of Hg sedimentary records. This study seeks to improve our understanding of the geologic Hg cycle by constraining the Hg degassing history of LIP magmas. We present data from basaltic dikes, sills, and flows of the Central Atlantic Magmatic Province (CAMP) and the Siberian Traps to gain insight into Hg emissions from LIP emplacement. In order to study the relation between emplacement depth and Hg concentration in the CAMP, we measured Hg concentration in samples from the Talcott basalt flow and from the associated Higganum-Fairhaven feeder dike system at multiple emplacement depths. In addition, we examined basalt from the Siberian Traps that intruded and baked preexisting coal beds. We measured Hg concentration in the basalt and in the coal at multiple distances from the basalt to constrain how contact metamorphic heating of the coal contributed to Hg emissions during Siberian Trap emplacement. Because mercury has a strong chemical affinity for organic compounds, the coal beds had relatively high Hg concentrations which may have been volatilized as a result of high temperatures during the Siberian Traps volcanism. We hypothesize that Hg concentrations will track progressive Hg degassing and decrease in proximity to the paleosurface. Furthermore, we predict that coal in proximity to the basalt intrusion will be depleted in Hg compared to coal farther away from the intrusion. Refined constraints on Hg release will improve interpretation of the sedimentary Hg record. Since the CAMP and the Siberian Traps coincide with the end-Triassic and end-Permian extinctions, we can potentially use Hg data to better understand the timing of volcanism associated with these extinction events.