Magmatic stability of eudialyte-group minerals (EGM) and element distribution between EGM and peralkaline silica-undersaturated melts

What is it about?

Eudialyte-group minerals (EGM) are special minerals that help scientists understand unusual types of molten rock (lava or magma) that are rich in sodium and calcium but low in silica. These minerals are getting a lot of attention because they contain elements like zirconium (Zr), niobium (Nb), tantalum (Ta), and rare-earth elements (REE), which are important for making advanced technologies like electronics and renewable energy devices. For EGM to form naturally in molten rock, there needs to be enough zirconium in the liquid rock to reach a critical concentration. We conducted experiments to see how EGM form in specific molten rock compositions when heated to high temperatures (750–1000 °C) and subjected to pressures like those found deep underground (100–200 MPa). We found that EGM can form and stay stable at lower temperatures (750–900 °C), but at higher temperatures (900–1000 °C), they break down into different minerals. In dry conditions (no water added), EGM begin to form when the molten rock has at least 0.2–0.22% zirconium dioxide (ZrO2). When water is present, more zirconium (1.1–2.85%) is needed for EGM to form. The experiments also showed that EGM are very good at trapping REE and elements like zirconium and niobium. However, at higher temperatures or when water is added, fewer of these elements end up in the EGM because they stay dissolved in the molten rock. Among the REE, the lighter ones like lanthanum (La) are less likely to be trapped in EGM compared to heavier ones.

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Why is it important?

This study helps explain the conditions needed for EGM - minerals containing elements such as Zr, Nb, Ta, and REE which are important for electronics and renewable energy devices, to form and how they capture valuable elements, which could make them useful for mining critical materials for modern technology.