Lithium isotopes in marine carbonates to investigate changes in seawater chemistry and continental silicate weathering in the Neoproterozoic

The Neoproterozoic Era is characterised by significant climatic change resulting in two global glaciations, a second major rise in atmospheric oxygen, two major steps in evolution that gave rise to the Ediacaran biota and several large negative carbon isotopic excursions. The onsets and terminations of these global glaciations would have undoubtably altered the chemistry of the Neoproterozoic oceans with potential consequences for life; yet the extent of continental weathering and subsequent elemental fluxes to the ocean during deglaciation is unknown. Here in this thesis, lithium (Li) isotope compositions (7Li/6Li ratios, expressed as δ7Li) in marine carbonates were used as a proxy for continental silicate weathering to investigate changes in the chemistry of Neoproterozoic oceans. Majority of Li isotope studies on marine carbonates have focused on calcium carbonates e.g., calcite and aragonite, but no systematic work has been done yet on dolomite. Therefore, in this thesis the lithium isotope fractionation during the formation of dolomite is investigated as it is the most abundant in the Precambrian.