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Building cratonic keels in Precambrian plate tectonics
A L Perchuk1,2, T V Gerya3, V S Zakharov4
1Geological Faculty, Lomonosov Moscow State University, Moscow, Russia. alp@geol.msu.ru.
Nature
|October 15, 2020
Summary
Ancient continental cores (cratons) feature deep mantle keels formed by Precambrian subduction. This process created thick, layered lithosphere, crucial for craton survival and diamond formation.
Area of Science:
- Geology
- Geophysics
- Tectonics
Background:
- Cratons are ancient continental cores with thick mantle keels.
- Mantle keels are isolated, depleted, buoyant, and diamond-bearing mantle volumes.
- Keel formation occurred only in the Early Earth (1.5-3.5 billion years ago) and lacks modern analogues.
Purpose of the Study:
- Investigate the origin of layered mantle keels.
- Explore the role of early Earth tectonics in keel formation.
- Understand the conditions for craton longevity.
Main Methods:
- Modeled oceanic subduction and arc-continent collision.
- Simulated increased early Earth mantle temperatures (150-250°C higher).
- Analyzed protokeel emplacement and cooling dynamics.
Main Results:
- Hot, buoyant sublithospheric mantle under subducting plates did not subduct.
- Slabs left behind craton-scale protokeel emplacements.
- Protokeel thickness correlated with cratonic lithosphere age maxima.
Conclusions:
- Precambrian subduction of depleted oceanic plates formed layered mantle keels.
- This mechanism explains keel layering and craton survival.
- Subsequent cooling of protokeels enabled diamond formation.
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