LONG Ke-shu¹, FU Yong^1,2*, CHEN Rui¹, YE Yuan-mou¹, YAN Shuang¹, CHEN Man-zhi¹

（1. College of Resource and Environment of Guizhou University, Guiyang 550025, China;
2. Institute of Mineral Resource，Chinese Academy of Geological Sciences, Beijing 100037, China）

Abstract: Based on a systematic analysis of the REE in rocks and ores of the Xinmin Bauxite deposit in the Northern Guizhou, the REE characteristics and enrichment mechanism of bauxite deposits in the Northern Guizhou have been discussed in this paper. The results show that the Huanglong Formation limestones are characterized with "flat" REE distribution patterns. The Hanjiadian Formation mudstone, the Liangshan Formation carbonaceous mudstone and the Dazhuyuan Formation ore-bearing rocksare characterized with " right-declined " LREE-enriched REE distribution patterns. In addition, REE distribution patterns of the Dazhuyuan Formation ore-bearing rocks are changed with the increase of the weathering intensity from the steep "right-declined" patterns for aluminous mudstones, to the flat "right-declined" patterns for bean shaped, compact massive, and clastic bauxites, and finally to the "left-declined" patterns for erthy bauxites. The total REE contents (∑REE) of ore-bearing rocks are generally decreased from bottom to top or along the downward dipping direction of the orebody, but increased along the striking direction of the orebody in the profile. These could be affected by the different rocks and thicknesses of the footwall, as the REE is much easier to be enriched in the mudstone footwall than the limestone footwall or the REE contents are generally increased with the increase of thickness for the same limestone footwall. Generally, the ∑REE contents of ores are controlled by their mineral assemblages (lithological types), with characteristics of " high REE in aluminous mudstone containing independent REE minerals, rich REE in oolitic grains of ores, poor REE in bean shaped ores, and poor REE in high aluminum ores". Based on the analysis of experimental data and correlation diagrams (Sr/Ba-∑REE, Sr/Cu-∑REE, δCe -∑REE, and δEu-∑REE), it can be seen that the REE is more likely to be enriched in salty seawater under the environment of dry and hot climate . Although the ore-bearing rocks were mainly formed in the oxidized environment, the high ∑REE rocks were formed in reduced environment.

Keywords: rare earth elements (REE); enrichment mechanism; bauxite deposit; the Northern Guizhou

ACTA MINERALOGICA SINICA Vol. 39, No.4, 2019, page 443-454