REE characteristics of rhodochrosite from the Daotuo manganese deposit in Guizhou

The Daotuo manganese deposit in Guizhou is a large-scale carbonate manganese deposit discovered in 2010 and hosted in the manganese-bearing black shales with rhodochrosite as the main manganese-bearing mineral at the base of the Nanhuan Datangpo Formation. The results of research in this study are generalized as follows. (1) The ΣREE contents range between 171.84×10^-6 and 243.08×10^-6 for the manganese ores with different manganese contents; 32.52×10^-6 and 135.69×10^-6 for the selected rhodochrosite in which the ΣREE contents amount to 15% and 80% of the whole manganese-bearing rocks, and ΣREE contents in rhodochrosite tend to increase with the increase of manganese contents. The REE distribution patterns for the rhodochrosite exhibit the "cap"-type distribution patterns showing low LREE contents, enriched MREE contents and relatively lower HREE contents than MREE contents, while almostly smooth straight distribution patterns for the whole manganese-bearing rocks. (2) The δCe values equal to about 1, and increase with the increase of Mn contents, indicating the gradual absorption of the element Ce during the deposition and enrichment of the manganese oxides and hydroxides. (3) There is no correlation between Mn and MREE, and a good correlation between P and MREE. It is inferred that the MREE enrichment in rhodochrosite may be caused by the phosphates, and coexistence of the phosphates and rhodochrosite may be ascribed to the incomplete separation of the elements P and Mn in the depositional environments at that time.