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]