Trace element geochemistry during chemical weathering - As exemplified by the weathered crust of granite, Longnan, Jiangxi

The granite weathering in Longnan, Jiangxi, is represented by mineralogical changes of feldspars --> montmorillonite, illite --> kaolinite, halloysite --> bauxite, with Na, Ca, Si, P, V, U and Sr being in a mobile state while Ti, Al, Fe, Sc, Th, Zr and Hf remaining relatively conservative. With the exception of Zr/Hf, Nb/Ta, Th/Sc, Zr/Nd and Sm/Nb, changes are notable in r atios between most of the trace elements. Re-distribution of REE and Y has taken place during the chemical weathering, and the REE patterns of weather ed samples in the profile, with original characters of the parent rock stil l recognizable, has undergone some fractionation. Generally, the extent of chemical weathering is the critical factor determining the mineralogical an d chemical characteristics of the profiles and this must be taken into acco unt in any study of tracing the provenance on the basis of mineralogical an d trace element characteristics of the sediments.