Researchers examine the new possibility of deep sea mining for rare earth elements to combat supply chain vulnerabilities.
Rare earth elements (REEs), such as lanthanum and cerium, are vital components in many everyday and emerging technologies, including smartphones and clean energy. However, due to concerns about the environmental impact of REE extraction and supply chain vulnerabilities (as China dominates the REE market, accounting for 57.5% of production in 2020), researchers are investigating potential locations to source REEs.
Deep sea mining for rare earth elements
Pelagic, or deep sea sediments, are now being explored as a significant potential source of REEs for future exploitation. In a recent paper published in the open access journal Chemical Geology, a team of Chinese and German researchers extracted, analysed, and quantified REEs discovered in the pelagic sediments of the Tiki Basin in the Southeast Pacific and the Central Indian Ocean Basin.
The research team utilised micro-scale methods to analyse the geochemical and mineralogical characteristics of REEs bound to two pelagic carriers: Ca-phosphate, predominantly in the form of bioapatite fossils, and Fe-Mn (oxyhydr) oxides, as micronodule.
Their methods included scanning electron microscope, x-ray diffraction, electron probe micro-analyser, and laser ablation-inductively coupled plasma mass spectrometry.
REE sample results
The results demonstrated that Ca-phosphate has a dominant role in hosting REEs in the deep sea environments studied, accounting for 69.3–89.4% of the total. “The percentages of REE controlled by Fe-Mn (oxyhydr)oxides, mainly as micronodule, are moderate (8.2% to 22.0%), except Ce (70.0–80.5%),” observed the researchers.
The study also revealed differences in the quantities of REEs discovered in samples taken from the Tiki Basin and the Central Indian Ocean Basin. This indicates that multiple factors — including the productivity of overlying seawater, water depth relative to carbonate compensation depth, and hydrothermal vent input — may be influencing REE enrichment in pelagic sediments.