LUO Xiang-jian, Qin Ying, LU Shu-fan, FU Hong-bin, LIU Guo-dong, Chen Wu^*

(Guizhou Geological Survey, Guiyang 550018, China)

Abstract: The "sedimentary type REE resource" is a new type of REE resource found in Guizhou Province. Based on geological survey of the Fuchu area, and detailed profile measurement and geochemical analysis of rocks of the profile in the Fuchu area, Hezhang County, we have summarized geochemical characteristics of samples from different lithologic segments of the REE-rich rock series and then have inferred the provenance of REE-rich rock series. The results show that the REE-rich rock series is stably distributed in the Fuchu area. They can be classified into ferruginous, aluminous and clastic rock segments. The supernormal REE-enriched anomalies occurred at the bottom of aluminous rock segment and in the clastic rock segment. The variegated aluminous claystone has the highest REE content of 2542.17×10^-6 which is matched the industrial grade. The REE-rich rock series mainly have major elements of SiO₂, Al₂O₃ and Fe₂O₃, with sums of their contents ranging from 78.28% to 84.45%, and an average value of 81.13%. Their different rocks have similar TiO₂ contents, and they have obviously low contents of other compatible elements. In the same time, they are depleted in large ion lithophile elements (LILE) including Rb, Ba, K, Sr and P are depleted, while they have relatively stable contents of high field strength elements (HFSE) including Zr, Hf, Nb, Ta, Th and U. Samples of the ferruginous, aluminous and clastic rocks have similar REE distribution patterns to that of the basalt, as they all have LREE-enriched and HREE-flat patterns, with weakly negative Ce and Eu anomalies as their δCe and δEu values are less than 1. Correlation analysis of major, trace and rare earth elements shows that the provenance of upper stratum above the basalt in the Fuchu area was mainly sourced from the Permian Emeishan basalt. Especially, the supernormal REE-enriched rock series (aluminous and clastic rock segements) were not only sourced mainly from the Emeishan basalt, but also sourced partly from the intermediate acidic volcanic ash.

Keywords: provenance; geochemistry; sedimentary type REE resource; Hezhang