Geochemical Study of Rare Earth Elements (REE) in Jajarm Bauxite Deposit (North East of Iran)

Jajarm bauxite deposit (north east of Iran) is the largest bauxite deposit in Iran which is located as a stratiform ore body between Elika and Shemshak formations. From the bottom to top of the profile, this deposit is consists of lower kaolinite, shaly and hard bauxite, and upper kaolinite, respectively. In this study rare earth elements of the hard and shaly bauxite sections of the deposit are investigated by use of the results of 22 chemical analyses. Correlation coefficient between rare earth elements and other elements demonstrate that clay minerals and also some minerals such as Churchite, Loparite, Xenotime, Rhabdophane, Monazite, Florencite, Anatase and Euxenite are the likelihood REE bearing minerals in Jajarm bauxite deposit. In Jajarm deposit toward the carbonate footwall of the profile the concentration of rare earth elements increases, thus from this point of view, this deposit is similar to karstic types. Increase of concentration of the REE at lower part of the profile is not same for all of the rare earth elements and it is as the result of the ionic potential of each of them and also it may be related to the type of the REE bearing minerals. So with increase of the ionic potential of the elements their concentration at lower part of the profile decreases. Due to the accompaniment of HREE with zircon and clay minerals, these elements have leached at the same amount from hard to shaly bauxite. As the result of the two different valences of Ce & Eu, these elements show different trends from other rare earth elements in chondrite normalized patterns and also as the concentration at lower part of the deposit. This anomalous manner is more obvious for Ce, so this element show positive anomaly and more enrichment in hard bauxite section in comparison with other LREE. In contrast with the hard bauxite, the negative anomaly and less enrichment of Ce can be seen in shaly bauxite. The variation of Eu is less than Ce and it is almost limited to relative negative anomaly of Eu in hard bauxite section.