Subduction erosion

Not to be confused with Erosion and tectonics.

Tectonic erosion or subduction erosion is the loss of crust from an overriding tectonic plate due to subduction.^[1] Two types of tectonic erosion exist: frontal erosion at the outer margin of a plate and basal erosion at the base of the plate's crust.^[1] Basal erosion causes a thinning of the overriding plate.^[2] When frontal tectonic erosion consumes a crustal block at the outer margin it may induce a domino effect on upper crustal tectonics causing the remaining blocks to fault and tilt to fill the “gap” left by the consumed block.^[2] Subduction erosion is believed to be enhanced by high convergence rates and low sediment supply to the trench.^[1]

Before the Neoproterozoic, subduction erosion rates were probably higher than at present due to higher convergence rates. A scarcity of blueschists from this time seems to support this view.^[1] However, this assertion is arguably wrong because the earliest oceanic crust would have contained more magnesium than today's crust and, therefore, would have formed greenschist-like rocks at blueschist facies.^[3]

The following features and processes have been associated with subduction erosion:

• Extensional tectonics: Tectonic erosion is believed be a widespread phenomenon in northern Chile with the normal faulting around Mejillones Peninsula attributed to an extensional domino effect caused by the consumption of a lithospheric block.^[2]
• Regional subsidence and transgression: The Miocene transgression of southern Chile has been suggested to have been caused by basal tectonic erosion.^[4] Subduction erosion does not explain the Miocene transgression further inland in Patagonia.^[5]
• Magmatic belt migration: Concurrent with the Andean orogeny the eastward migration of the magmatic belts in Chile from the Late Cretaceous onward is thought to be caused by subduction erosion.^[6]

See also

• Crustal recycling
• Delamination

References

1. Stern, Charles R. (2011). "Subduction erosion: Rates, mechanisms, and its role in arc magmatism and the evolution of the continental crust and mantle". Gondwana Research. 20 (2–3): 284–308. Bibcode:2011GondR..20..284S. doi:10.1016/j.gr.2011.03.006.
2. Niemeyer, Hans; González, Gabriel; Martínez-De Los Ríos, Edmundo (1996). "Evolución tectónica cenozoica del margen continental activo de Antofagasta, norte de Chile". Revista Geológica de Chile (in Spanish). 23 (2): 165–186.
3. Palin, Richard M.; White, Richard W. (2016). "Emergence of blueschists on Earth linked to secular changes in oceanic crust composition". Nature Geoscience. 9 (1): 60–64. Bibcode:2016NatGe...9...60P. doi:10.1038/ngeo2605. S2CID 130847333.
4. Encinas, Alfonso; Finger, Kenneth L.; Buatois, Luis A.; Peterson, Dawn E. (2012). "Major forearc subsidence and deep-marine Miocene sedimentation in the present Coastal Cordillera and Longitudinal Depression of south-central Chile (38°30'S – 41°45'S)". Geological Society of America Bulletin. 124 (7–8): 1262–1277. doi:10.1130/b30567.1. hdl:10533/135235.
5. Encinas, Alfonso; Pérez, Felipe; Nielsen, Sven N.; Finger, Kenneth L.; Valencia, Victor; Duhart, Paul (2014). "Geochronologic and paleontologic evidence for a Pacific–Atlantic connection during the late Oligocene–early Miocene in the Patagonian Andes (43–44°S)". Journal of South American Earth Sciences. 55: 1–18. Bibcode:2014JSAES..55....1E. doi:10.1016/j.jsames.2014.06.008. hdl:10533/130517.
6. Charrier, Reynaldo; Pinto, Luisa; Rodríguez, María Pía (2006). "3. Tectonostratigraphic evolution of the Andean Orogen in Chile". In Moreno, Teresa; Gibbons, Wes (eds.). Geology of Chile. Geological Society of London. pp. 21, 45–46. ISBN 9781862392199.