LUO Wu-ping¹, LI Guang-lai^1*, LI Cheng-xiang¹, LIU Xiao-bo¹, YIN Xiao-yan¹, WEI Xing-lin²

（1.Fundamental Science on Radioactive Geology and Exploration Technology Laboratory (ECIT), Nanchang 330013, China；
2. Jiangxi Nuclear Industry Geological Bureau, Nanchang 330046, China）

Abstract: The weathered crust profile in the Xijialing REE deposit of the Xiangshan area has been divided into the yellow soil layer, iron plate layer, red soil layer, spherical regolith and residual rock from top to bottom of the profile, on the basis of detailed field geological investigation. Then their petrographic and element geochemical researches have been carried out by using X-Ray diffraction (XRD), X-Ray fluorescence (XRF), Inductively Coupled Plasma Mass Spectrometry ICP-MS), and other research methods. by The results show that the rock weathering degree is decreased gradually, but contents of plagioclase, K-feldspar, and biotite are increased from top to bottom of the profile, with appearance of clay minerals such as illite and kaolinite. From the yellow soil layer to the residual rock, contents of K, Na, Ca, and FeO are generally increased, oxygen fugacity (OX) values and Fe2O3 contents are firstly increased and then decreased with their maximum values in the iron plate layer, contents of SiO2 are firstly decreased and then increased, while contents of Al2O3 are firstly increased and then decreased, respectively. The results of trace element analysis show that contents of immobile elements including Th, U, Ta, Nb, Zr, Hf, and Ga in each layers are similar with non-significant differentiation, while contents of active elements including Rb, Ba, and Sr are increased gradually from the top to bottom. The REE contents of yellow soil layer, iron plate layer, red soil layer, and residual rock are much lower than those of the spherical regolith. The significant enrichment of REE in the spherical regolith could be explained that the REE adsorbing capacity of yellow soil layer, iron plate layer, and red soil layer was greatly decreased due to the combination of clay minerals and colloid Fe(OH)3, resulting in the significant enrichment of REE in the spherical regolith. In addition, Ce is obviously enriched in yellow soil layer, iron disk layer, and red soil layer, but depleted in spherical regolith, with no obvious anomaly in residual rock. This may be because that Ce was tied by minerals such as cerianite formed in the upper parts of the profile during weathering process.

Keywords: Weathering crust eluvial REE deposit； elemental geochemistry；Xiajialing；Xiangshan

ACTA MINERALOGICA SINICA Vol. 39, No.3, 2019, page 237-246