North China rock study points to possible subduction nearly 4 billion years ago
A Nature study reports that a 3.95-billion-year-old rock in eastern Hebei may preserve evidence of an early subduction event.
Researchers analyzed a 3.95-billion-year-old trondhjemitic gneiss from eastern Hebei, China, and reported chemical evidence that its source material had been altered near Earth's surface before reaching mantle depths.
The authors said modeling suggests the material was rapidly buried along a cool thermal gradient, most likely through a temporary subduction event. The finding adds evidence to debates over when plate tectonics began.