Earth is clingy when it comes to copper. A new Rice University study this week in the journal Science finds that nature conspires at scales both large and small -- from the realms of tectonic plates down to molecular bonds -- to keep most of Earth's copper buried dozens of miles below ground.
"Everything throughout history shows us that Earth does not want to give up its copper to the continental crust," said Rice geochemist Cin-Ty Lee, the lead author of the study. "Both the building blocks for continents and the continental crust itself, dating back as much as 3 billion years, are highly depleted in copper."
Finding copper is more than an academic exercise. With global demand for electronics growing rapidly, some studies have estimated the world's demand for copper could exceed supply in as little as six years. The new study could help, because it suggests where undiscovered caches of copper might lie.
But the copper clues were just a happy accident.
"We didn't go into this looking for copper," Lee said. "We were originally interested in how continents form and more specifically in the oxidation state of volcanoes."
Earth scientists have long debated whether an oxygen-rich atmosphere might be required for continent formation. The idea stems from the fact that Earth may not have had many continents for at least the first billion years of its existence and that Earth's continents may have begun forming around the time that oxygen became a significant component of the atmosphere.
In their search for answers, Lee and colleagues set out to examine Earth's arc magmas -- the molten building blocks for continents. Arc magmas get their start deep in the planet in areas called subduction zones, where one of Earth's tectonic plates slides beneath another. When plates subduct, two things happen. First, they bring oxidized crust and sediments from Earth's surface into the mantle. Second, the subducting plate dri
|Contact: David Ruth|