Archives par mot-clé : Iron

Europium points to new suspect in continental mystery

by Rice University, May 16, 2018 in ScienceDaily

Clues from some unusual Arizona rocks pointed Rice University scientists toward a discovery — a subtle chemical signature in rocks the world over — that could answer a long-standing mystery: What stole the iron from Earth’s continents?

The find has weighty implications. If the iron content of continental rocks was a bit greater, as it is in the rocks beneath Earth’s oceans, for example, our atmosphere might look more like that of Mars, a planet so littered with rusty, oxidized rocks that it appears red even from Earth.

In a new paper available online in Science Advances, Rice petrologists Cin-Ty Lee, Ming Tang, Monica Erdman and Graham Eldridge make a case that garnet steals the most iron from continents. The hypothesis flies in the face of 40-plus years of geophysical thinking, and Tang, a postdoctoral fellow, and Lee, professor and chair of the Department of Earth, Environmental and Planetary Sciences at Rice, said they expect a healthy dose of skepticism from peers.

“The standard view … (…)

The onset of widespread marine red beds and the evolution of ferruginous oceans

by Haijun Song et al., August 2017, in Nature

Banded iron formations were a prevalent feature of marine sedimentation ~3.8–1.8 billion years ago and they provide key evidence for ferruginous oceans. The disappearance of banded iron formations at ~1.8 billion years ago was traditionally taken as evidence for the demise of ferruginous oceans, but recent geochemical studies show that ferruginous conditions persisted throughout the later Precambrian, and were even a feature of Phanerozoic ocean anoxic events.