Oral Presentation Sub22 Conference

Tracing the origin of REE enrichment in phosphorites using Sm-Nd and Sr isotopes (17198)

Diana Zivak 1 , Carl Spandler 1 , Helen Degeling 2
  1. The University of Adelaide, Adelaide, SA, Australia
  2. Geological Survey of Queensland, Brisbane, QLD, Australia

Rare earth elements (REEs, lanthanide group La-Lu, including Y) are essential for development of renewable and advanced technologies necessary for transition to net-zero carbon by 2050. Recent studies (Emsbo et al., 2015; Valetich et al., 2022) of phosphorites, a marine sedimentary rock with over 18-20 wt.% P2O5 currently mined as phosphate fertiliser, have identified them as a potential source of REEs. The primary mineral of phosphorite, carbonate fluorapatite (CFA), hosts the majority of the REEs that, along with the ease of extraction of REEs from CFA as a by-product of phosphate mining, makes phosphorites an attractive economic target. However, not all phosphorites are enriched in REEs, thus understanding the factors that control REE distribution and enrichment in these rocks is essential for informing exploration campaigns. Here we use a combination of isotopic (Sm-Nd and Sr) and geochemical (whole rock REE) methods to elucidate the origin of REEs in marine phosphorites. We find that underlying basement composition and phosphorite textures (pelletal vs. non-pelletal) play a major role in the enrichment of REEs in phosphorites.

  1. Emsbo, P., McLaughlin, P. I., Breit, G. N., du Bray, E. A., & Koenig, A. E. (2015). Rare earth elements in sedimentary phosphate deposits: solution to the global REE crisis? Gondwana Research, 27(2), 776-785. 
  2. Valetich, M., Zivak, D., Spandler, C., Degeling, H., & Grigorescu, M. (2022). REE enrichment of phosphorites: An example of the Cambrian Georgina Basin of Australia. Chemical Geology, 588, 120654. doi:https://doi.org/10.1016/j.chemgeo.2021.120654
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  • Acknowledgements: This work was funded by the Queensland Government under the New Economy Minerals Initiative (NEMI) and made possible by the generous support of several companies providing samples and deposit knowledge to the project. Dr Robert Klaebe at the Mawson Analytical Spectrometry Services (MASS) facilities at the University of Adelaide is thanked for his help in obtaining the Sm-Nd and Sr isotopic data for the project.