Archean eclogite-facies oceanic crust indicates modern-style plate tectonics

Area of Science:

• Earth Sciences
• Geology
• Tectonics

Background:

• The timing of Earth's plate tectonics is a significant scientific debate.
• Eclogite, a rock formed under high pressure and low temperature, indicates deep oceanic crust subduction.
• Currently, no eclogites older than 2.1 billion years have been found, suggesting plate tectonics began then.

Purpose of the Study:

• To investigate the existence of Archean orogenic eclogites.
• To determine if deep subduction occurred before 2.1 billion years ago.
• To refine the timeline of Earth's plate tectonic activity.

Main Methods:

• Documenting an Archean orogenic eclogite.
• Analyzing metamorphic conditions indicating high-pressure, low-temperature transformation.
• Dating the eclogite to establish its age.

Main Results:

• An Archean orogenic eclogite was discovered and documented.
• Evidence shows oceanic crust subducted to depths of 65-70 km around 2.5 billion years ago.
• This finding pushes back the documented age of eclogite-facies metamorphism by 400 million years.

Conclusions:

• Modern-style plate tectonics, involving deep subduction, operated by the end of the Archean eon.
• The onset of plate tectonics may be significantly older than previously established.
• This discovery challenges existing models for early Earth geological evolution.