XUE Hong-fu1, HUANG Wei-hu1, ZENG Dao-guo1*, HUANG Zhi-long3, JIN Zhong-guo2, LUO Tai-yi3, WU Lin3, XIANG Zhen-zhong3
(1. Institute Geology and Mineral Exploration, Non-ferrous Metals and Nuclear Industry Geological Exploration Bureau of Guizhou, Guiyang 550005, China;
2. Non-ferrous Metals and Nuclear Industry Geological Exploration Bureau of Guizhou, Guiyang 550005, China;
3. Stake Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China)
Abstract: The REE ore-bearing layer (Pxt) in the Yulong area of the northwestern Guizhou is distributed at the bottom of the Xuanwei Formation (P3x), and overlaied discomformably above the Emeishan basalt Formation (P2-3em). It is composed of Nb- and REE-enriched ferruginous and aluminous claystones. The research shows that the distribution patterns of trace elements and rare earth elements of the ferruginous claystone are nearly consistent with those of the basalt, indicating that the ferruginous claystone has affinity with the Emeishan basalt. The projection plots of major elements reflect that the material of ferruginous claystone was mainly sourced from the Emeishan basalt. There are differences between distribution patterns of trace elements and rare earth elements of the aluminous claystone and those of the basalt. In addition, the projection plots of major elements show that the aluminous claystone has multiple material sources. These mean that in addition to the Emeishan basalt, the intermediate acidic magmatic materials had also provided part of source materials for the aluminous claystone. Although both ferruginous and aluminous claystones have light rare earth elements (LREE)-enriched distribution patterns, the aluminous claystone has higher LREE-enriched distribution patterns comparing to the ferruginous claystone. Comparing to others of the LREE, La, Ce, Pr and Nd are more obviously enriched as they are accounted for 85.76%－98.36% of the LREE, Comparing to others of heavy rare earth elements (HREE), Gd, Dy, Er and Yb are more obviously enriched as they are accounted for 84.41%－89.33% of the HREE. The ferruginous claystone was formed in an oxidation environment with weak hydrodynamic force, while the aluminous claystone was formed at the oxidation-reduction interface with strong and weak alternated hydrodynamic force. The values of CIA, CIW and ICV reflect that the ferruginous and aluminous claystones had undergone strong weathering and reworking processes.
Keywords: rare earth elements (REE) ore-bearing layer; geochemical characteristics; the Emeishan basalt; northwestern Guizhou
