The REE occurrence state in claystone in the Wu'an area,Hebei Province
Claystone is one of the main host rocks containing rare earth elements(REE).It has a huge potential of the REE resource.Currently,due to the unclear understanding of the REE occurrence state in claystone,the development and utilization of REE in claystone are limited.In this study,the REE-rich claystone samples from the Baozhuang area in Wuan City,Hebei Province were selected for analyzing their petrological characteristics using the rock and mineral identification,automated mineral identification and characterization system(AMICS),and X-ray diffraction(XRD)and for studying the occurrence state of REE in claystone samples in terms of mineralogical,geochemical,and textural perspectives at multiple scales by using techniques including the in-situ laser ablation-inductively coupled plasma mass spectrometry(LA-ICP-MS),kaolinite colloid extraction,chemical stepwise extraction,time-of-flight secondary ion mass spectrometry(TOF-SIMS),and density functional theory(DFT)calculation.The results show that the main mineral component of claystones in this area is of kaolinite(88.19％).Leaching test results indicate that there is only 2.67％ionic REE,and only 0.04％independent REE mineral of allanite,proving that there is only a small portion of REE in ionic and independent mineral forms in the claystone.The strong correlation between the REE and kaolinite suggests that the REE could be mostly presented in forms of ultrafine REE minerals between kaolinite particles,or as isomorphic substitution ions within the kaolinite lattice.
Rare earth elements(REE)occurrence stateautomated mineral identification and characterization system(AMICS)in-situ analysis
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