Subduction erosion explained

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. 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

Notes and 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 . . 20 . 2–3. 284–308 . 10.1016/j.gr.2011.03.006. 2011GondR..20..284S .
2. Niemeyer. Hans . González. Gabriel . Martínez-De Los Ríos. Edmundo . Evolución tectónica cenozoica del margen continental activo de Antofagasta, norte de Chile . es. Revista Geológica de Chile. 1996. 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 . 10.1038/ngeo2605. 2016NatGe...9...60P . 130847333 .
4. Encinas . Alfonso. Finger. Kenneth L.. Buatois. Luis A.. Peterson. Dawn E.. 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). 2012. Geological Society of America Bulletin. 124. 7–8. 1262–1277. 10.1130/b30567.1. 10533/135235. free.
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) . . 55 . 1–18 . 10.1016/j.jsames.2014.06.008 . 2014JSAES..55....1E. 10533/130517 . free .
6. Book: Charrier . Reynaldo. Pinto . Luisa . Rodríguez . María Pía. Reynaldo Charrier. Moreno . Teresa . Gibbons . Wes . Geology of Chile . Geological Society of London . 2006 . 21, 45–46 . 3. Tectonostratigraphic evolution of the Andean Orogen in Chile . 9781862392199.