Pre-Mesozoic evolution of the central Andes; The basement revisited

Abstract

The central Andes of northern Chile and northwestern Argentina developed in a largely autochthonous, intracontinental setting during Proterozoic and Paleozoic time through a recurrent sequence of extensional and compressional tectonic regimes. The exposed pre-Andean crust consists of tectonically isolated outcrops of: (1) metamorphosed basement, (2) plutonio bodies, and (3) slightly metamorphosed volcanic and sedimentary strata resting upon and intruded by multiple plutonic units. U-Pb and Nd-Sm geochronology indicates the existence of a Precambrian foundation for the central Andes dating from at least middle Proterozoic time. Three episodes of Precambrian/Paleozoic deformation/magmatism are recognized: (1) the Panamerican at the Precambrian/Cambrian transition, (2) the Caledonian at the Ordovician/Silurian boundary, and (3) the Variscan during the Carboniferous. Intrusive units can be grouped into synorogenic (S-type) and anorogenic (A-type) rocks based on structural, petrographic, and geochemical relations. Mafic lavas of middle Proterozoic to lowerCarboniferous age likely were generated during episodes of crustal dilatation.

Bandas de cataclastitas en el Plutón Tambillo: Manifestaciones de la orogénesis oclóyica en el cordón de Lila, norte de Chile

“…1). La unidad estratificada más antigua corresponde a basaltos y brechas volcánicas dacíticas con intercalaciones de turbiditas, del TremadocianoArenigiano medio y se incluye dentro del Complejo ígneo-sedimentario del Cordón de Lila (CISL; Niemeyer, 1989;Damm et al, 1990;Zimmermann et al, 2010). El CISL se observa intruido, a su vez, por varios cuerpos plutónicos de edad ordovícica: Monzogranito Tucúcaro, Sienita Tilopozo, Granodiorita Pingo-Pingo y Monzogranito Tambillo (Mpodozis et al, 1983).…”

La Formacion QuebradaGrande, del Ordovicico, Cordon de Lila (Region de Antofagasta, norte de Chile): significado estratigrafico y paleogeografico.

“…The age of this complex is not well constrained and has been tentatively assigned to the Cambrian?-Lower Ordovician? on the basis of their stratigraphic relationships (Niemeyer, 1989;Damm et al, 1990). The CISL is unconformably overlain by a marine succession of about 1,600 m of conglomerates, sandstones and siltstones which was referred to as Quebrada Grande Formation by González et al (2006).…”

“…The porphyry is in turn unconformably overlain by Lower Silurian quartzitic and calcareous sandstones of the Quebrada Ancha Formation (Navarro et al, 2006). All these rocks are intruded by huge volumes of granitic rocks of Middle-Upper Ordovician to Lower Silurian age (Mpodozis et al, 1983;Damm et al 1990). The plutonic rocks are covered by marine quartzarenites and conglomerates of the Devonian Lila Formation (Breitkreuz, 1986 …”

“…Consequently, and following Omarini and Sureda (1994) we consider in this contribution that the CISL would belong to an independent volcanic chain than the FEPO as known in western Argentinean Puna. The AMO was constructed upon a continental crust, as is indicated by isotopic Pb composition from zircons of some of the Ordovician Plutons of Cordón de Lila (Damm et al, 1990). This fact led Bahlburg and Hervé (1997) to consider that the CISL developed upon the Proterozoic basement of the Arequipa-Antofalla Terrane, which in Chile is well exposed in the Sierra de Moreno (Loewy et al, 2004;Griem-Klee and Niemeyer, 2005;GriemKlee and Niemeyer, 2006) and Sierra de Limón Verde (Baeza-Assis, 1984), near Calama (Fig.…”

“…1). It is well known by the occurrence of important outcrops of Lower Paleozoic sedimentary, volcanic successions and intrusive rocks (Mpodozis et al, 1983;Niemeyer, 1989;Damm et al, 1990;Pérez et al, 2006;Navarro et al, 2006). The study of these units is key for the understanding of the stratigraphic, tectonic, and paleogeographic relationships between the Ordovician successions of the ArgentinaChilean Puna (Benedetto, 2001).…”