Extinct volcanoes' interiors reveal rare-earth metal abundance

Scientists from the Australian National University (ANU) and the Chinese Academy of Sciences have announced breakthrough research findings on the extraction of rare-earth elements from the interiors of extinct volcanoes. This discovery could significantly impact global reserves of these precious resources, which are used in many industries.

Rare-earth metals, also known as rare-earth elements (REE), are a group of 17 chemical elements. They are extremely difficult to extract due to their dispersion and small deposits; they never occur in pure form. Their total content in the Earth's crust is 164 ppm (parts per million), which is relatively low compared to other elements such as oxygen, which has a content of 464,000 ppm, or gold, which occurs at about 0.004 ppm.

Rare-earth metals are less profitable to mine than gold, yet the demand for them continues to grow due to their wide application in various sectors of the economy. They are used in producing items such as smartphones, digital camera lenses, wind turbines, computer hard drives, batteries, LEDs, lasers, electric vehicle motors, monitors, and televisions. China is responsible for about 70% of the total global production of rare-earth metals.

The latest research conducted by ANU and the Chinese Academy of Sciences shows that the interiors of extinct volcanoes can be a valuable source of rare-earth elements. The work published in the journal "Geochemical Perspectives Letters" indicates that magmatic rocks from the interiors of inactive volcanoes contain significantly higher amounts of REE than rocks from active volcanoes.

Dr Michael Anenburg, a geologist at ANU and co-author of the study, stated, "We have never seen an iron-rich magma erupt from an active volcano, but we know some extinct volcanoes, which are millions of years old, had this enigmatic type of eruption." Dr Anenburg also added that such volcanic deposits could be found worldwide.

To understand the impact of conditions for forming iron-rich magma on REE content, scientists conducted dozens of experiments in the Experimental Petrology Laboratory at ANU. They produced rocks similar to those from iron-rich extinct volcanoes by simulating volcanic eruptions.

Chemical mixtures corresponding to volcanic rocks were placed in a pressure furnace and heated to 800°C-1500°C for two to five days until completely melted. After analysing these rocks' chemical and mineral composition, scientists learned that the highest concentration of REE is found in phosphate group minerals such as apatite, monazite, and xenotime.

The research results turned out to be surprising. The laboratory-produced rocks contained even 100 times more rare-earth elements than some currently exploited deposits. Currently, the world's largest deposits of rare-earth metals are located in China, and in Europe, the largest producer is Sweden. However, according to Dr Anenburg, Australia may soon become a significant player in the REE market thanks to the exploitation of new deposits.