LIU Fei-xiang1,2, YIN Xin-ya3*, LIU Qi1*
(1. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China;
2. University of the Chinese Academy of Sciences, Beijing 100049, China;
3. Guizhou Minzu University, Guiyang 550025, China)
Abstract: Climate change is strongly affected by the concentration of CO2 in the atmosphere. Weathering of continental lithosphere is an important process controlling the variation of atmospheric CO2 concentration. By rebuilding the information of paleo-continental weathering profile, we can effectively understand the evolution history of Earth's climate. Traditionally, strontium (Sr) isotopes were used to trace the continental weathering, but there are still some deficiencies in the interpretation of Sr isotope records. For example, the Sr isotope ratios of seawater can be affected by hydrothermal fluids, while the Sr isotope ratios of waters in rivers can be easily affected by different types of weathered rocks. In addition, only the weathering of silicates is considered to control the atmospheric CO2 sink over the geological time scale, but it is difficult to distinguish Sr isotope records of the carbonate weathering from those of the silicate weathering. Therefore, another suitable tracer of isotope system is required to reconstruct the history of continental weathering. Lithium (Li), a trace element, is mainly concentrated in the silicate minerals of the lithosphere, but very limited in carbonates. Thus, Li isotope system can be a promising tracer for the silicate weathering. Meanwhile, Li isotope ratios are less affected by vital biofractionation effects, and can be recorded well in marine carbonates. These advantages of Li isotope ratios in marine carbonates have provided strong support for tracing the continental weathering history. More importantly, it is necessary to clearly understand the geochemical behaviors of lithium isotopes related to the weathering, transport, and crystallization processes. Therefore, in this paper, we have introduced the Li isotope compositions of different reservoirs, and Li partitioning and isotope fractionation behaviors between various substances and phases, reviewed the recent progresses of lithium isotopes applied for tracing and reconstructing the continental weathering history, and given details of the key problems to be solved in the future.
Keywords: lithium isotopes; weathering; isotope fractionation
ACTA MINERALOGICA SINICA Vol. 41, No.2, 2021, page 127-138
