Geochemistry of red residua underlying dolomites in karst terrains of Yunnan-Guizhou Plateau: II. The mobility of rare earth elements during weathering
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- 作者：Hongbing ; Ji ; Shijie ; Wang ; Ziyuan ; Ouyang ; Shen ; Zhang ; Chenxing ; Sun ; Xiuming ; Liu ; Dequan ; Zhou
- 关键词：REE ; Fractionation ; Abnormal enrichment ; The convex-up patterns ; Red residua ; Karst terrain ; REE ; Weathering ; Red Residua ; Karst Terrain ; Yunnan-Guizhou Plateau
- 刊名：Chemical Geology
- 出版年：2004
- 出版时间：January 15, 2004
- 年：2004
- 卷：203
- 期：1-2
- 页码：29-50
- 全文大小：897 K
文摘
The aim of this study is to characterize the evolution of the rare earth elements (REE) in the Pingba red residua on karst terrain of Yunnan-Guizhou Plateau. The in-situ weathering and the two-stage development of the profile had been inferred from REE criterions. The REE were significantly fractionated, and Ce was less mobilized and separated from the other REEs at the highly enriched top of the profile. This is consistent with the increase of oxidation degree in the regolith. And it is also suggested that the wet/dry climate change during chemical weathering caused Ce alternative change between enrichment and invariance in the upper regolith. Chondrite-normalized REE distribution patterns for samples from dolomites and the lower regolith are characteristic of MREE enrichment and remarkable negative Ce-anomalies patterns (similar to the convex-up REE patterns). The following processes are interpreted for the patterns in this study: (1) the accumulation of MRRE-rich minerals in dolomite dissolution, (2) water–rock interaction in the weathering front, and (3) more leaching MREE from the upper part of the profile. The latter two explanations are considered as the dominant process for the formation of the REE patterns. Samples from the soil horizon exhibit typical REE distribution patterns of the upper crust, i.e., LaN/YbN