西峰地区晚第三纪红土稀土元素的初步研究

A PRELIMINARY STUDY ON REE OF THE LATE TERTIARY LATERITE IN XIFENG AREA

本文基于对甘肃西峰地区晚第三纪红土和第四纪风成黄土及古土壤稀土元素的分析 ,揭示出红土稀土元素丰度与黄土及古土壤相比变化范围较大 ,可能与碳酸盐的相对淋溶与淀积有关 ;红土ΣL REE/ΣHREE值明显低于黄土 ,指示着一定程度的风化作用 ;而稀土参数δEu、δCe等变化不大 ,红土、黄土和古土壤稀土模式具有很大的一致性 ,特别是将红土的稀土元素丰度用碳酸盐校正后 ,这个特点更加明显 ,反映了红土与第四纪黄土和古土壤在成因上具有相似性 ,这一特征支持红土基本物质“风成说”的观点。红土稀土模式曲线亦与 U CC稀土模式一致 ,说明红土的稀土模式可以作为上地壳稀土模式的代表。

The REE analysis results of late Tertiary laterite,Quaternary eolian loess and paleosol in Xifeng,Gansu Province,showed that total laterite REE abundance is more variable than that of loess and paleosol,due to the eluviation and deposition of the carbonate.The ratio of LREE/HREE is higher than in loess and paleosols,suggesting a strange weathering of the laterite.At the same time,their indices of δEu and δCe and the REE distribution pattern normalized to chondrite,in general,are uniform with the loess and paleosol,suggesting that their original material was transported from the same source area.These results support the hypothesis of eolian origin of the laterite.The revised laterite REE pattern is also parallel to UCC,showing the pattern is of an adequate substitution.