Behavior Of Elements During Weathering Of Granite-A Case Study In Lianyang,Guangdong Province

The research on the behavior of elements in the process of rock weathering mainly includes the weathering index based on major elements or oxides and the mass balance calculation based on immobile elements.The former is an index to quantitatively measure the weathering degree of the sample based on the change of the chemical composition of the sample;the latter is currently widely used to quantitatively study the behavior of elements in the open system.The mass balance calculation is based on the immobile elements present in the system.The immobile elements are used as reference to calculate the migration of other elements in the geochemical process.In this paper,the weathered crust of a biotite granite in Lianyang,Guangdong Province is selected as the research object to study the behavior of elements in the process of granite weathering.From the bottom rock to the top soil,the CIA increases with the decrease of depth,WIG?WIP and WIC decrease with the decrease of depth,and the variation law is basically the same,indicating that the weathering degree of the sample gradually increases,which is consistent with the field observation results,which proves that WIG is suitable for quantitative characterization of the weathering degree of granite.The above results show that without CO₂ content data,the weathering degree of granite can still be quantitatively characterized accurately,which makes it possible to apply the huge RGNR project data in China.Before the mass balance calculation,the immobile elements in the system should be determined first.In this paper,the immobile elements in the system are determined bytai method.It is considered that there are no absolutely immobile elements in the geological or geochemical process,but there may be relatively immobile elements in a subdivision stage of the continuous changing geochemical process.In this paper,the results of mass balance calculation show that almost all elements have different degrees of mass brought in or out,which is consistent with the idea of method of plateau.But in most processes,SiO₂?Fe₂O₃?Ti?Sn?Mo?Cu?Zn?V?Zr?Nb and Th are mass constant in most stages,which can be considered as immobile elements.The other elements in the weathering process there is a large degree of bring in or out,belong to the mobile elements.During weathering,Ce anomalies are more related to weathering degree.When weathering degree is strong,Ce anomalies increase with weathering degree and Ce anomalies do not change with weathering degree when weathering degree is weak.According to the stable attributes of immobile elements in the geochemical process,the change trend of the content of immobile elements between parent rock and weathered products is the same,which provides a theoretical basis for trying to construct a stable geochemical tracer method and will play an important role in geology,environment,court and other fields.