Using magnesium isotopes traces continental weathering:progress and challenges
Background,aim,and scope Continental weathering governs the surface material cycle and their transportation from the land to the lake/ocean reservoirs,regulating the global carbon cycle and climate change at different time scales by consuming atmospheric CO2.How to effectively trace continental weathering is one of the important scientific topics on Earth's surface processes.As one of the most promising tracers of carbonate and silicate weathering,magnesium(Mg)isotopes have long been used to trace and reconstruct continental weathering scenarios.To achieve effective research methods,it is helpful to review the establishment of Mg isotopes as tracers of carbonate and silicate weathering.Materials and methods With the improvement of mass spectrometry,high-precision analysis techniques of Mg isotopes have undergone rapid and mature development and have gained wide applications.We reviewed the major developments,issues and challenges in the application of Mg isotopes for tracing weathering,including its major reservoirs,weathered crust,riverine systems,laboratory experiments,and modeling simulation,all of which have been gradually evolved over the last few decades.Results Because of about 8%mass difference between 24Mg and 26Mg,the absence of valence changes and redox reactions,Mg isotopes possess the robust potential to trace carbonate and silicate weathering processes.Nonetheless,the origins and controlling factors on Mg isotopic fractionation during weathering processes remain controversial.Discussion The changes in Mg isotopic compositions from weathered crust to fresh bedrocks are complex,whereas the factors controlling Mg isotopic variations in riverine systems are diverse and controversial,especially in large river systems.In addition,the behaviour of Mg isotopic fractionation in laboratory experiments has not been conclusively established and modeling simulation of Mg isotopic compositions is still in their early stage.More attentions are focused on seasonal variation of riverine Mg isotopic compositions at small,mono-lithological catchments.Conclusions We noted that Mg isotopes system certainly has the potential and distinctiveness to trace continental weathering,both for carbonate and silicate weathering.Recommendations and perspectives For reducing the uncertainty of using Mg isotopes to trace carbonate and silicate weathering processes,it's suggested that carrying out more laboratory experiments of rocks/minerals,combining large catchments with small ones,and facilitating computation simulation as well as multi-isotopes coupling are required in the future.
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维普
