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Rejuvenation and erosion of the cratonic lithosphere

Abstract

Cratons are the ancient cores of continents, characterized by tectonic inactivity, a thick mantle lithosphere and low heat flow. Although stable as tectonically independent units for at least the past 2 billion years, cratons have experienced episodic rejuvenation events throughout their history. The lower part of the lithosphere is first weakened and altered by impregnation of magma at a few locations, which produces local density anomalies that have a destabilizing effect. These altered zones coalesce to form linear incisions at the base of the craton. Lateral erosion of the lithosphere is further aided by small-scale convection resulting from variations in lithosphere thickness, proceeding eventually to large-scale sinking of lithospheric mantle. Oxidation of volatile-enriched mantle leads to a significant drop in melting temperature as redox processes dominate melting mechanisms in cratonic mantle. Reduced conditions dominate in the deepest lithosphere, in contrast to shallower levels where carbon — slowly accumulated as diamond — is remobilized by oxidation.

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Figure 1: Weakening and erosion of cratonic lithosphere.
Figure 2: Comparison of melting curves for mantle peridotite in oxidized (blue; with H2O and CO2 (ref. 80,81,82)) and reduced (red; with H2O and CH4) conditions.
Figure 3: Melting curve for the mantle in a cratonic rift (red line) corresponding to the stage illustrated in Fig. 1c69.
Figure 4: Redox state in the cratonic lithosphere (blue scale) and in sub-rift asthenosphere (green scale).

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Acknowledgements

Work on alkaline rocks and cratons is supported by the Geocycles Cluster at Mainz and the Rift-Link Resarch Unit of the German Science Foundation. This is Geocycles publication No. 493. The manuscript benefited from the comments of W. Bleeker, D. Canil and N. Simon.

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Foley, S. Rejuvenation and erosion of the cratonic lithosphere. Nature Geosci 1, 503–510 (2008). https://doi.org/10.1038/ngeo261

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