Geodynamic models of Cordilleran orogens: Gravitational instability of magmatic arc roots

Claire A. Currie, Mihai N Ducea, Peter G Decelles, Christopher Beaumont

Research output: Chapter in Book/Report/Conference proceedingChapter

15 Citations (Scopus)

Abstract

Cordilleran orogens, such as the central Andes, form above subduction zones, and their evolution depends on both continental shortening and oceanic plate subduction processes, including arc magmatism and granitoid batholith formation. Arc and batholith magma compositions are consistent with partial melting of continental lithosphere and magmatic differentiation, whereby felsic melts rise upward through the crust, leaving a high-density pyroxenite root in the deep lithosphere. We study gravitational removal of this root using two-dimensional thermal-mechanical numerical models of subduction below a continent. The volcanic arc position is determined dynamically based on thermal structure, and formation of a batholith-root complex is simulated by changing the density of the arc lithosphere over time. For the model lithosphere structure, magmatic roots with even a small density increase are readily removed for a wide range of root strengths and subduction rates. The dynamics of removal depend on the relative rates of downward gravitational growth and lateral shearing by subduction-induced mantle flow. Gravitational growth dominates for high root densification rates, high root viscosities, and low subduction rates, resulting in drip-like removal as a single downwelling over 1-2.5 m.y. At lower growth rates, the root is removed over >3 m.y. through shear entrainment as it is carried sideways by mantle flow and then subducted. In all models, >80% of the root is removed, making this an effective way to thin orogenic mantle lithosphere. This can help resolve the mass problem in the central Andes, where observations indicate a thin mantle lithosphere, despite significant crustal shortening and thickening.

Original languageEnglish (US)
Title of host publicationMemoir of the Geological Society of America
PublisherGeological Society of America
Pages1-22
Number of pages22
Volume212
ISBN (Print)9780813712123
DOIs
StatePublished - 2015

Publication series

NameMemoir of the Geological Society of America
Volume212
ISSN (Print)00721069

Fingerprint

geodynamics
lithosphere
subduction
batholith
mantle
magmatic differentiation
crustal shortening
pyroxenite
crustal thickening
continental lithosphere
thermal structure
downwelling
granitoid
entrainment
subduction zone
partial melting
island arc
magmatism
viscosity
magma

ASJC Scopus subject areas

  • Geology

Cite this

Currie, C. A., Ducea, M. N., Decelles, P. G., & Beaumont, C. (2015). Geodynamic models of Cordilleran orogens: Gravitational instability of magmatic arc roots. In Memoir of the Geological Society of America (Vol. 212, pp. 1-22). (Memoir of the Geological Society of America; Vol. 212). Geological Society of America. https://doi.org/10.1130/2015.1212(01)

Geodynamic models of Cordilleran orogens : Gravitational instability of magmatic arc roots. / Currie, Claire A.; Ducea, Mihai N; Decelles, Peter G; Beaumont, Christopher.

Memoir of the Geological Society of America. Vol. 212 Geological Society of America, 2015. p. 1-22 (Memoir of the Geological Society of America; Vol. 212).

Research output: Chapter in Book/Report/Conference proceedingChapter

Currie, CA, Ducea, MN, Decelles, PG & Beaumont, C 2015, Geodynamic models of Cordilleran orogens: Gravitational instability of magmatic arc roots. in Memoir of the Geological Society of America. vol. 212, Memoir of the Geological Society of America, vol. 212, Geological Society of America, pp. 1-22. https://doi.org/10.1130/2015.1212(01)
Currie CA, Ducea MN, Decelles PG, Beaumont C. Geodynamic models of Cordilleran orogens: Gravitational instability of magmatic arc roots. In Memoir of the Geological Society of America. Vol. 212. Geological Society of America. 2015. p. 1-22. (Memoir of the Geological Society of America). https://doi.org/10.1130/2015.1212(01)
Currie, Claire A. ; Ducea, Mihai N ; Decelles, Peter G ; Beaumont, Christopher. / Geodynamic models of Cordilleran orogens : Gravitational instability of magmatic arc roots. Memoir of the Geological Society of America. Vol. 212 Geological Society of America, 2015. pp. 1-22 (Memoir of the Geological Society of America).
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