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Evolutionary cycles during the Andean orogeny: repeated slab breakoff and flat subduction?
Author(s) -
Haschke M. R.,
Scheuber E.,
Günther A.,
Reutter K.J.
Publication year - 2002
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1046/j.1365-3121.2002.00387.x
Subject(s) - subduction , geology , eclogitization , slab , magmatism , orogeny , crust , slab window , seismology , geochemistry , geophysics , oceanic crust , tectonics
Tectonomagmatic similarities between the modern Chilean flat‐slab region and pre‐Neogene magmatic episodes suggest that they represent analogues to flat subduction. Evolutionary patterns in each magmatic suite include (i) increasing La/Yb ratios and Sr‐and Nd‐isotopic enrichment through time, (ii) eastward‐migration of magmatism after periods of transpressional/transtensional intra‐arc deformation, and (iii) subsequent termination and virtual absence of main‐arc activity for 5–10 Myr. These patterns may reflect slab shallowing followed by flat subduction and thickening of the overlying crust. If repeated, they require interchanging episodes of slab steepening. Increasing convergence rates force slab kinking and eventual failure of the oversteepened slab, followed by rebound of the slab tip (owing to lack of further slab pull), flat subduction and termination of subduction‐related magmatism. Rapid subduction leads to shallow overriding of the detached slab fragment. Eclogitization of the gradually steepening slab tip at depth and subsequent slab pull permits asthenospheric corner flow and subduction‐related magmatism.