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《GEOCHIMICA》 1995-03
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REE GEOCHEMISTRY OF GRANITOID WEATHERING CRUST AND PROPERTIES OF ORES IN SOUTHERN CHINA

Chi Ru'an; Xu Jingming; He Peijiong; Zhu Yongjun(Institute of Nuclear Energy Technology, Tsinghua University, Beijing 100084)  
The weathering crust of REE granites in southern China can be divided into humic layer,completely weathering layer and partly weathering layer. In the completely weathering layer, rare earth elements are adsorped on the clay minerals (mainly halloysite and kaolinite) in hydrous complex or hydroxy and hydrous complex during the weathering leaching process. The layered clay minerals have two active adsorptive centers, i.e. the replacing structure and the residual bond on fractured surface. The order of adsorbility of these two centers is as follows: La3+Ce3+Pr3+Nd3+Sm3+Eu3+Gd3+Tb3+Dy3+Ho3+Y3+Er3+Tm3+Yb3+Lu3+ based on quantum chemical calculating, and Ce3+ is unstable and easily form CeO2, which leads to the fractionation of REE during their migration and enrichment. Therefore, the light rare earths are slightly more enriched at the upper layer and the heavy those at the bottom of the ore body of the weathering crust.The ores of the weathering crust type have four main physicochemical properties:the variety of contained water, the bufferity to resist the change of acid and base,the relative chemical stability of adsorbed rare earth ions and the exchangeability of ions absorbed on the clay minerals.
【Fund】: 清华大学青年科学基金
【CateGory Index】: P588.121
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