The evolution of the chemistry of Earth¿s atmosphere has been affected over time by the composition of gases released during volcanic eruptions, which, in turn, are the expression of Earth¿s interior processes. The eruption of CO2-rich magmas occurred between 250 and 50 Ma coincided with the emplacement of large igneous magmatic provinces named LIPs that are considered the major cause for carbon cycle perturbation and dramatic environmental changes. LIPs events also overlap with the Phanerozoic largest mass extinctions and the Oceanic Anoxic Events (OAEs). Recently, much interest has been focused on searching for geochemical tracers of large volcanic eruptions in sedimentary rocks that allow estimating the duration of LIPs events and how these might have limited the life development. Mercury (Hg) anomalous spikes are used as unique geochemical marker of LIP evidence in the sedimentary record. Volcanic eruptions are the primary source of Hg to the atmosphere and the long residence time relative to atmospheric mixing of this metal (up to 2 years), allows an efficient global distribution.
This project aims to constrain the link between LIP magmatism and Hg geochemical cycle. In particular, geochemical, mineralogical and petrological investigations will be performed on two stratigraphic sections in Gubbio, representative of Cenomanian-Turonian and Cretaceous-Paleogene boundaries, which are temporally overlapped to three important LIP events such as High Atlantic, Caribbean and Deccan Traps. The integration of data from geochemistry, mineralogy and petrology will contribute to propose a model of Hg speciation from the Earth¿s interior to the atmosphere and establish possible relations with additional trace elements.
So far, several studies have followed a similar procedure based on the Hg measurement on sediments temporally overlapped to past LIP events. With this project, I aim to investigate the Hg speciation through a multidisciplinary methodology based on geochemical, mineralogical and petrology observations. This represents an innovation and a successive step respect to the current knowledge about LIPs Hg anomalies, that relies only on a geochemical point of view. A noteworthy aspect of my proposal is the possibility to establish a link between mantle processes (e.g. magma formation and transport), inherited elements signature during LIP eruptions and the anomalies in the sedimentary rocks. In this regard, the study might contribute to understanding whether the current Hg concentrations recorded in present-day sediments near active volcanic districts are indicative of a LIP-like magmatic event that our planet is experiencing.