A recent study led by Elizabeth Cottrell and Megan Holycross has challenged a long-standing theory regarding the composition of Earth’s continental crust, particularly its lower iron content and higher oxidation levels compared to oceanic crust. This research, published in Science, experiments with garnet formation, disputing the idea that the crystallization of garnet deep in the Earth’s crust causes the iron depletion and oxidized state of the continental crust. The study highlights the importance of continental crust in making Earth suitable for life, as its buoyancy contributes to dry land, allowing terrestrial existence.
To investigate this, the researchers employed laboratory simulations that replicated the intense heat and pressure found beneath continental arc volcanoes. They discovered that garnets produced during these conditions did not contain enough unoxidized iron to explain the observed properties of continental magmas. This leads to the conclusion that different conditions in the Earth’s mantle might be responsible for oxidation and iron depletion. The findings prompt further inquiries into what specific mechanisms are at play in the mantle, suggesting oxidized sulfur may play a role, an area currently under investigation. This study is part of the Smithsonian’s initiative to address fundamental questions about Earth’s uniqueness.
