Minerals of Rare Earth Elements in High-Phosphorus Ooidal Ironstones of the Western Siberia and Turgai Depression

Abstract

The aim of this research was to study the rare earth (REE) minerals in ooidal ironstone deposits of the West Siberian basin and the Turgai depression. Authigenic minerals (monazite and cerite) were described, and their main mineral form was identified as light rare earth element phosphate (LREE-phosphate) in this study. LREE-phosphate is included in ferruginous ooids, peloids, and oncoids and forms a consistent mineral association with Fe-hydroxides (goethite and its hydrated amorphous derivatives) and Fe-rich layered silicates (Fe-illite-smectite, chamosite, berthierine). The constancy of the mineral association in two deposits of different ages indicates a general mechanism behind the formation of these minerals. LREE-phosphates (authigenic monazite) are characterized by microscopic sizes (up to 24 μm), diverse morphology (mainly spherical or xenomorphic), and occupy spaces between the micro-cortex in ferruginous spheroids. This mineral can be found in other deposits of ooidal ironstone. According to its mineralogical and chemical characteristics, LREE-phosphate mainly belongs to the authigenic (nodular or “gray”) monazite. However, the incomplete (not 100%) correspondence of Kikuchi bands with the reference monazite does not allow its reliable identification. Based on its small size, chemical leaching or bacterial interaction is recommended to extract REE from ooidal ironstone while predicting the associated removal of phosphorus from iron ore due to its dominant phosphate mineral form. Ooidal ironstone should be considered a complex deposit and an unconventional natural type of REE ores as an example of the largest Bakchar and Lisakovsk deposits.

Mineralogy and Geochemistry of some Phosphate Deposits for Possible Rare Earth Elements Mineralization Potentials within Sokoto Basin, Northwestern Nigeria

“…K 2 O had a negative relationship suggesting the samples may be primary phosphorites and the presence of minute K 2 O content outside the apatite crystal lattice (15) . The strong relationship of Fe 2 O 3 T/P 2 O 5 may be due to the deposition of Fe 2 O 3 and FeO during the process of phosphatization which is also peculiar with primary phosphorites (16) while the negative correlation with SiO 2 reflects a mutual substitution before the final precipitation within the depositional environment. A positive correlation with MnO indicates some level of affinity with P 2 O 5 and occurrence within the apatite structure.…”

Editorial for Special Issue “Rare Earth Deposits and Challenges of World REE Demand for High-Tech and Green-Tech at the Beginning of the 3rd Millennium”

“…Deady et al [19] investigated these issues in relation to volcanic derived placers at Aksu Diamas, Turkey, finding that a range of REE and REE-bearing minerals are concentrated with Quaternary sediments derived from weathering of alkaline igneous rocks. Rudmin et al [20] extend the study of sedimentary deposits to those produced by authigenesis, identifying processes for the formation of REE phosphates in ooidal ironstones and discussing the implications for potential future processing.…”