Recently, I attended a joint conference between the University of Houston and the university where I work, The University of Utah. At the two-day event, researchers from both universities brainstormed how we can help solve some of the pressing challenges in various fields of energy science and engineering. One field discussed was critical minerals—the backbone of modern industries and societies. This edition of Core Elements shares some new stories from the science and geography of critical minerals.
Rasoul Sorkhabi
Editor, Core Elements
Enrichment of Rare-Earth Metals in Igneous Rocks
Joaquin Corbalan P/Shutterstock.com
One of the major questions in geoscience is which factors enrich or reduce the concentrations of rare-earth elements (REEs) in minerals. Take for instance, iron oxide-apatite (IOA) deposits.
Geography of IOA deposits:
IOA deposits are associated with magmatic rocks, but the exact mechanism for their formation is debated and actively investigated.
IOAs have been reported from a wide range of geological formations.
The oldest occurrence is monazite found in the Kiruna mine in Sweden. The host rock is about 1.88 billion years old.
The youngest occurrence is monazite in the volcanic tephra of the El Laco mine in Chile. It is about 2 million years old.
IOA deposits with rich REEs have also been reported from mining tailings in the Adirondack Mountains of New York and the Pea Ridge mine of Missouri.
The new study: Yan and colleagues from China and Australia investigated the immiscibility between iron-oxide phosphate (FeP) liquids and silicate magma (FeP-Si) melts.
Design: They conducted 17 FeP-Si immiscibility experiments at more than 800–1150 degrees Celsius at 0.4–0.8 gigapascal pressures for two to three days. The experiments were done in layered piston-cylinders.
What they found:
The experiments reproduced many natural textural features of IOA deposits.
The study strongly supports that immiscibility between FeP liquid and silicate magma melts is one of the controlling factors in the enrichment of REEs in the IOA deposits.
Go deeper: Read the study, published in Geochemical Perspectives Letter,here.
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We need lithium for batteries, cobalt for smartphones, neodymium for wind turbines, and so forth. Mineral consumption will continue to grow; however, most people are not aware of the circumstances under which these minerals are produced, especially in the Global South.
In a recent commentary in Nature, Victor Maus and Tim Werner highlight the less-attractive side of the world’s mineral dependence.
Adverse environmental and social impacts:
Among adverse effects are the destruction of rainforests and biodiversity, pollution of water and soil, damage to local communities and habitats.
For every ton of REEs produced in Malaysia, up to 2,000 tons of toxic waste is also released.
Data gap:
Of the 120,000 square kilometers of land used for mining worldwide, 56 percent has no production information listed in the global S&B Capital IQ Pro database. Russia, China, Indonesia, Brazil, and the United States are among those countries for which there is not complete documentation.
Almost none of the mining operations in Myanmar, Venezuela, and Guyana are documented.
Illegal mining:
According to the U.N. Environment Programme, more than 80 percent of gold mining in Colombia and Venezuela is illegally operated.
More than 16,000 tons of REEs have been illegally mined from Malaysia’s tropical forests, according to a report published in Science.
The authors suggest:
Researchers should honestly present and evaluate their data and collaborate more on data collection.
They should investigate the causes of data gaps in terms of confidentiality, commercial interests, government regulations, and/or lack of accountability.
They should design independent ways to verify data and reports.
Las week’s quiz question was: Of the two seismic waves, P and S, which one is mainly used in the seismic survey of petroleum basins. Why? How can we also use the other seismic waves to get extra information?
Compressional P waves are routinely used in seismic surveys of petroleum basins because P waves are the fastest seismic waves and arrive (are recorded) first. Moreover, P waves travel through both solid and fluid media. That said, shear (S) waves can also be used in association with P waves, and they further provide information about physical properties of subsurface rocks and fluids through attribute analysis. For example, velocity ratios (Vp/Vs) povide information about Poisson’s ratio.
Go deeper: For more information, see these articles by Farfour and Gaci and this one by Nanda.
Now, for this week’s quiz: Why are rare-earth elements called by that name?
Please send your response by November 7 to editorial@aapg.org (subject line: Core Elements Quiz)
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