A new study by the Department of Earth and Planetary Sciences, ETH Zürich, has examined the arc magmas near the subduction zone, stating that water is the dominant volatile substance in them. Water in hydrous magmas undergoes a separate phase, triggering explosive volcanic activity. Such super-wet magmas can generate economically valuable mineral resources, especially Copper deposits.
Typically, the water content in magma is considered to be between 4-6%. Meanwhile, a few super-wet magmas contain as much as 6-8% water. The key scientific finding of a study published in Nature Communications says that these magmas are instrumental in forming porphyry copper deposits, which account for nearly 75% of the world’s copper.
These copper deposits are formed when the magma is rich in copper-bearing fluids and expels these fluids into the Earth’s upper crust.
Although the super-wet magmas are abundant at greater depths, and not expected to persist at shallow depths, scientists are suggesting that super-wet magmas are far more common than previously thought. To support this proposal, researchers studied zircon crystals in copper-rich rocks found worldwide and recorded high water content.
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“Consequently, ‘super-wet’ arc magmas would normally be expected to stall at deeper crustal levels. However, several studies have inferred the presence of super-wet magmas in some volcanic centers and mid to upper crustal intrusions suggesting these magmas may occasionally ascend to the near-surface,” says the study.
As copper is a vital material in renewable energy technologies like solar panels, wind turbines, and electric vehicles, this study offers a practical tool for locating new copper deposits. By identifying the high water content at ancient magmatic systems, geologists can better predict hidden copper resources.
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Journal Reference:
Nathwani, C., Blundy, J., Large, S. J., Wilkinson, J. J., Buret, Y., Loader, M. A., & Tavazzani, L. (2024). A zircon case for super-wet arc magmas. Nature Communications, 15(1), 1-11. DOI: 10.1038/s41467-024-52786-5