Preliminary Estimation Of Cadmium Isotopic Composition Of The Upper Continental Crust

As a transition metal element,Cadmium is easily taken in and used by creatures,but it is poisonous and harmful to human body.Cadmium isotopes have been successfully applied to tracing the evolution of planets and nebulae,circulation of marine nutrient and sources of artificial pollution,etc.And they have great potential for tracing the atmospheric circulation,surface water cycle and fossil fuels burning.As cadmium of upper continent crust（UCC）is the main source of supergene process of low temperature,its Cd isotopic composition has great importance in geological processes.However,there is still a lack of relevant research.42 typical geological samples of the continental upper crust,including loess,stream sediments and granites,were analyzed for the Cd isotopic composition.Theδ^114/110Cd of all samples range from-0.781‰to+0.034‰,with a variation of 0.815‰.Theδ^114/110Cd of the two S-type granites are-0.781‰and-0.166‰,respectively.Theδ^114/110Cd of 15 stream sediments vary from-0.373‰to+0.034‰‰.Theδ^114/110Cd of25 loess samples range from-0.595±0.117‰to 0.021±0.066‰（2SD）,with a variation of 0.616‰and a mean value of-0.174±0.327‰（2SD）.The varying ratios suggest that the weathered upper crust may be heterogeneous in Cd isotopic composition.Based on this study and previous research,we preliminarily determinate the mean Cd isotopic composition of UCC,which is-0.169±0.336‰（2SD,n=36）.The value differs significantly from chondrites,the estimation of BSE,hydrothermal crustal,precipitates,seawater and marine sediments.Most importantly,it is significantly different from the products of various plant samples and industrial activities.This will facilitate the study of Cd migration and transformation in the continental supergene environment and atmospheric environment,as well as the application of Cd isotope tracer technology in the treatment of human health,environmental pollution and crust-mantle differentiation.