Geologists solve important mysteries surrounding the deposition of rare earth elements

An international team of scientists has helped unravel a long-standing mystery of how rare earth elements accumulate underground – and sometimes disappear without a trace.

The Rare Earth Element (REE) is a set of 17 valuable chemical elements that are incredibly important in the manufacture of technological devices, from smartphones to critical raw materials in disk drives, wind turbines, satellites, electric vehicles, medical equipment, and much more. Being used as.

Although their name suggests they are rare, they may actually be relatively abundant resources in the earth’s crust; Their scattershot dispersion makes it difficult to separate and remove from beneath the surface, let alone in an environmentally friendly manner.

Because of this, concentrated REE deposits are a highly reputable natural resource, and scientists are constantly devising new and improved methods of finding and acquiring valuable minerals.

In a new study led by Australian National University geologist Michael Annenberg, researchers sought to find out the chemical mechanism by which REEs form beneath the surface and specifically around igneous carbonite rock.

The researchers state in their new paper, “These rare rocks and their altered and weathering derivatives provide most of the world’s REE.”

“No integrated model interprets all the characteristics of carbonitite-related REE deposits, dilution explorations as necessary to secure future supplies.”

To investigate the processes of mineralization behind REE deposits associated with carbonatite, Annenberg and his team simulated what happens when carbonite rock is heated under high pressure, before it is too cold and neutral in natural magmatic processes .

By placing small amounts of synthetic carbonite in silver or nickel capsules in a piston-cylinder system, the researchers sampled temperatures up to 1,200 ° C (2,192 ° F) at pressures up to 2.5 gigapascals (GPa) before slowly decomposing. . Cooling them to 200 ° C (392 ° F) and 0.2 GPa.

“The objective was to understand how to concentrate REE from a whole carbonite body into high-grade localized deposits,” Einberg explained on his Twitter account.

“So we decided that let’s put a carbonite in a capsule and test it ourselves.”

Before now, it was thought that some ligands – molecules capable of binding REEs, including chlorine and fluorine – were required to solubilize REE, which was capable of mobilizing chemicals in crystallized concentrations capable of extraction.

But this is not what the experiment showed. Rather, the results suggest that alkaline chemicals are required for REE transport of carbonatites as precursors to economic grade mineralization, the experiment suggests that sodium and potassium help render REE soluble. Of.

According to the researchers, alkali-bearing carbonatites are capable of forming REE-rich fluids that can travel long distances in magmatic-like conditions, while retaining high REE solubility.

Of course, just because we have seen it in laboratory conditions, it does not mean that we will observe the same exact reactions in nature’s open systems, which may have the presence of water and all other types of chemicals in the environment. Change things.

Nevertheless, it is a step forward, and one that overhauls our knowledge on the background processes involved in REE formation and concentration.

“This is a good solution that helps us better understand where ‘heavy’ rare earths such as dysprosium and ‘light’ rare earths such as neodymium and carbonite can be concentrated in and around intrusions,” senior author and geologist Frank Wall told the University of Exeter.

“We were always looking for evidence of chloride-bearing solutions but failed to find it. These results give us new ideas.”

The findings are stated in Science advance.


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