Element Behavior Of Granite During Weathering

Granite weathering profile,as the research object in Huairou District of Beijing,compared with the collected three granite weathering profile’s data（CZ2017D04、LC19B和WAZ18D01）and comparative analysis based on 12 kinds of the major elements or oxides,29 kinds of trace elements and 14 kinds of rare earth elements to explore the elements’space changes and migration behavior in the process of granite weathering.The CIA is assumed that Al₂O₃,Na₂O,K₂O and Cao are all feldspar minerals,and the degree of weathering is measured by the mole ratio of Al₂O₃ and Na₂O,K₂O and Ca O.The WIG is defined as the mole ratio of active elements Na₂O,K₂O,Ca O and P₂O₅ to Al₂O₃,Fe₂O₃ and Ti O₂ The CIA and WIG were used to describe and evaluate the weathering degree of samples in weathering profile,and the differences of weathering degree among four weathering profiles were explored.It is confirmed that WIG has the same effect as CIA in describing the weathering degree of samples,and makes up for the defect that CO₂is not analyzed in the regional geochemical survey plan in China,which provides the possibility for the analysis of a large number of regional geochemical data.The immobile elements in the weathering process of granite are determined by method of plateau,and the mass balance calculation is used to quantitatively describe and analyze the process and content of the elements.It is found that the seven major elements of Si O₂,Al₂O₃,Fe₂O₃,K₂O,Na₂O,P and Mn in the weathering process of granite are immobile elements in most weathering stages.However,due to the small content of trace elements,they are greatly affected by weathering degree and leaching,and do not share the same immobile elements.Through the mass transfer,it is found that As,Th and U elements are brought out obviously,Mg O,Hg,and B elements are brought in obviously,and other elements are brought in and brought out completely or have no obvious change rule during the weathering process of granite in the profile.