Geologia

Journal of Structural Geology 30 (2008) 1520–1539

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Journal of Structural Geology
journal homepage: www.elsevier.com/locate/jsg

The role of inherited tectono-sedimentary architecture in the development of the central Andean mountain belt: Insights from the Cordillera de Domeyko
` ˜ A. Amilibia a, *, F. Sabat a, K.R. McClay b, J.A. Munoz a, E.Roca a, G. Chong c
a

` ´ Departament de Geodinamica i Geofısica, Universitat de Barcelona, Zona Universitaria de Pedralbes s/n, 08018 Barcelona, Spain Fault Dynamics Research Group, Geology Department, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK c ´ ´ Departamento de Ciencias Geologicas, Universidad Catolica del Norte, Antofagasta, Chile
b

a r t i c l e i n f o
Articlehistory: Received 7 December 2007 Received in revised form 11 August 2008 Accepted 23 August 2008 Available online 10 September 2008 Keywords: Central Andes Oblique subduction Structural inheritance Basin inversion Porphyry copper deposits

a b s t r a c t
The structure of the Cordillera de Domeyko is dominated by a number of elongated N–S-trending basement ridges. These ridges were uplifted bysteep reverse N–S faults that deformed the Mesozoic– Cenozoic cover. The vergence of the fault system varies along strike, conferring an apparent doubly vergent ‘‘pop-up’’ geometry to the axial zone. Two Mesozoic pre-compressional extensional events were recorded in the area. New structural data presented in this paper indicate that most of the generated N– S-trending thrusts and related foldswere controlled by the inversion of the pre-existing Mesozoic extensional faults. Thin-skin structures in the Mesozoic–Cenozoic cover are genetically linked to major basement upthrusts, which could be interpreted as basement short-cuts formed during inversion rather than as uplifted blocks associated with major Cenozoic strike-slip faults. Growth-strata geometries date the beginning of the Andeancompressional event, which generates the Chilean Precordillera, as far back as 90 Ma ago; the resulting structural architecture is strongly controlled by inherited pre-Andean extensional structures. The association of porphyry intrusives with major reverse faults suggests that the emplacement of the Eocene–Oligocene porphyry Cu–Mo deposits in Northern Chile can be explained by an oblique-inversionTectonics Model. The upper Eocene–lower Oligocene giant porphyry copper bodies (Chuquicamata, La Escondida, El Salvador) located in the Cordillera de Domeyko show an adakitic affinity. This magma affinity, together with structural evidence presented in this work, indicates that porphyry emplacement occurred at the end of the basement-involved contractional stage that generates the anomalous thickenedcrust needed to generate these magmas. This tectonic evolution is coherent with the existence of a flat-slab subducting beneath the Central Andes (22 –26 S) during early Cenozoic, that will also produce the eastward migrating of the compressional regime in the upper plate since Late Cretaceous. Ó 2008 Elsevier Ltd. All rights reserved.

1. Introduction The Central Andes, between 22 and 25south latitude, occupies the smooth transition between a nearly flat subduction to the south and a 30 east dipping subduction to the north. It includes several N–S-trending morphostructural units between the present-day subduction margin and foreland (Fig. 1). From west to east these units are: (1) Coastal Cordillera, (2) Longitudinal Valley, (3) Chilean Precordillera and pre-Andean Depression, (4)Western Cordillera (magmatic arc), (5) Altiplano – Puna, (6) Eastern Cordillera and (7) Sub-Andean Ranges (deformed foreland). The studied area is located in the Cordillera de Domeyko, which belongs to the northern part of the Chilean Precordillera

* Corresponding author. E-mail addresses: aamilibiac@ub.edu, ken@gl.rhul.ac.uk (A. Amilibia). 0191-8141/$ – see front matter Ó 2008 Elsevier Ltd....