Abstract: How the carbon cycle influences the atmospheric carbon dioxide level is of a major concern for Earth’s habitability.The oceanic lithium (Li) cycle can be used to trace carbon cycle because both cycles are controlled by chemical weathering,
hydrothermal-seafloor interaction, and marine clay authigenesis which also known as reverse weathering. The variations in
seawater Li isotope compositions posit changes in the sink and source processes such as continental weathering intensity and/or rate as well as reverse weathering rate. This paper reviews the global cycle of oceanic lithium and the mass balance for seawater lithium isotopes, focusing on the present-day fluxes and associated isotope fractionation mechanisms. Challenges still remain to better constrain the budgets as well as isotope fractionation factor especially in hydrothermal alteration and reverse weathering. The review also extends to the use of seawater li isotope records in tracing carbon cycle during climate events and critical time periods in the earth history. Collectively, this review highlights the potential as well as limitations of utilizing seawater Li isotope records to trace global carbon cycle in deep time. 

Key words: Li isotope, carbon cycle, chemical weathering, reverse weathering, hydrothermal alteration