Crustal-scale structural architecture in central Chile based on seismicity and surface geology: Implications for Andean mountain building

Marcelo Farías, Diana Comte, Reynaldo Charrier, Joseph Martinod, Claire David, Andrés Tassara, Felipe Tapia, Andrés Fock

Research output: Contribution to journalArticlepeer-review

113 Citations (Scopus)

Abstract

We document a crustal-scale structural model for the central Chile Andes based on seismicity and surface geology, which consists in a major east verging ramp-detachment structure connecting the subduction zone with the cordillera. The ramp rises from the subducting slab at ∼60 km depth to 15-20 km below the western edge of the cordillera, extending eastward as a 10 km depth flat detachment. This structure plays a fundamental role in the Andean orogenesis because most of the shortening has been accommodated by structures rooted in it and allows the distribution of crustal thickening in a "simple shear deformation mode." Indeed, despite shortening distribution being very asymmetric (∼16 km versus ∼70 km in the western and eastern side, respectively), the western side is higher and thicker than what is expected. Yield strength envelopes show strong rheological control on this structure. Vp and Vp/Vs variations in the upper mantle and in the deepest limit of the seismogenic interplate contact mark the intersection of the ramp with the slab, which coincides with the blueschist-eclogite transition. Therefore, subduction processes would control the depth where the major east verging structure may merge with the slab. Such a ramp-flat structure is observed in other parts of the Chilean margin; hence, it seems to be a first-order feature in the Andean subduction zone. This structure delimitates upward the rocks, transmitting part of the plate convergence stress fromthe plate interface, and controls mountain-building tectonics, thus playing a key role in the Andean orogeny.

Original languageEnglish
Article numberTC3006
JournalTectonics
Volume29
Issue number3
DOIs
Publication statusPublished - May 2010

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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