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Active foundering of a continental arc root beneath the Sierra Nevada

Domenii publicaţii > Ştiinţele pământului şi planetare + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: Zandt, G., Gilbert, H., Owens, T., Ducea, M.N., Saleeby, J., and Jones, C.

Editorial: Nature, 431, p.41-46, 2004.

Rezumat:

Seismic data provide unique images of crust-mantle interactions during ongoing
removal of the dense batholithic root beneath the southern Sierra Nevada. The
removal was initiated between 10 and 3 Ma with a Rayleigh?Taylor-type
instability, but with a pronounced asymmetric flow into a mantle downwelling
(drip) beneath the adjacent Great Valley. A nearly horizontal bottom-to-the-SW
shear zone accommodated the detachment of the ultramafic root from its granitoid
batholith. With continuing flow into the mantle drip, viscous drag at the base of
the remaining ~35-km-thick crust has thickened it by ~7 km in a narrow crustal
welt beneath the western flank of the range. Adjacent to the welt and at the top of
the drip, a V-shaped cone of crust is being dragged down ~25 km into the core of
the mantle drip, causing the disappearance of the Moho in the seismic images.
Viscous coupling between the crust and mantle is driving present-day surface
subsidence.

Cuvinte cheie: drip, foundering, arc root,