Geodynamic evolution of the early Paleozoic Western Gondwana margin 14°–17°S reflected by the detritus of the Devonian and Ordovician basins of southern Peru and northern Bolivia C.R. Reimann a, ⁎, H. Bahlburg a , E. Kooijman b , J. Berndt b , A. Gerdes c , V. Carlotto d , S. López e a Westfälische Wilhelms-Universität Münster, Institut für Geologie und Paläontologie, Corrensstrasse 24, 48153 Münster, Germany b Westfälische Wilhelms-Universität Münster, Institut für Mineralogie, Corrensstrasse 24, 48153 Münster, Germany c Goethe Universität Frankfurt, Institut für Geowissenschaften, Mineralogie, Altenhöferallee 1, 60438 Frankfurt am Main, Germany d INGEMMET, Av. Canadá 1470, Lima, Perú e Servicio Geológico y Técnico de Minas, Calle Federico Zuazo No. 1673 esq. Reyes Ortíz, La Paz , Bolivia abstract article info Article history: Received 14 July 2009 Received in revised form 3 February 2010 Accepted 4 February 2010 Available online xxxx Keywords: U–Pb Lu–Hf Detrital zircon Early Paleozoic Western Gondwana Margin Peru–Bolivia We present results of a combined study of in situ U–Pb and Lu–Hf analyses on detrital zircons of Ordovician to Devonian sandstone successions of the Eastern Cordillera of Peru and Bolivia, as well as of the Altiplano and Coastal Cordillera of Peru (14°–17°S). We use our data to constrain the provenance and tectonic evolution of this part of the Gondwana margin in the early Paleozoic. The zircon-age composition is very variable in the different locations. Sandstones of the Eastern Cordillera have a dominant input of Brazilian- age zircons (0.7–0.5 Ga) with two prominent peaks at around 0.52– 0.58 Ga and 0.61–0.67 Ga. A prevailing eastern source (Brazilian Shield, Amazonian Craton) is inferred. In contrast, sandstones from the Coastal Cordillera and Altiplano have major inputs of Famatinian (0.5–0.4 Ga), Grenvillian (1.2–0.9 Ga) and occasionally zircons of 1.85–1.75 Ga crystallisation ages. Here, a dominant provenance from the Arequipa Massif is likely. Zircons preserving a juvenile component with εHf (t) values range from about + 12 to + 6 are limited to crystallisation ages between 1.45 and 1.0 Ga. All younger grains have lower εHf (t) values consistent with recycling of old crust without juvenile additions during the Neoproterozoic. Brazilian-age zircons of an Amazonian craton provenance and Famatinian-age zircons of an Arequipa Massif provenance have similar Hf model ages suggesting their derivation from the same evolved crust. © 2010 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. 1. Introduction Sedimentary basins represent long-term archives of crustal and tectonic evolution. This information is particularly significant if intrusive and/or extrusive rocks are scarce, e.g. due to erosion or burial. With the combination of the U–Pb and Lu–Hf isotope systems of detrital zircons it is possible to trace the provenance of the sedimentary detritus and to gain information on the crustal and geodynamic evolution of the source areas (e.g. Nebel-Jacobsen et al., 2005; Kemp et al., 2006; Gerdes and Zeh, 2006; Augustsson et al., 2006; Willner et al., 2008; Veevers and Saeed, 2008; Bahlburg et al., 2009, 2010; Zeh and Gerdes, 2010). The U–Pb isotope system can be used to infer the crystallisation age of magmatic or metamorphic zircon and thus provides the age of the source rock itself. Even though, the direct comparison of the detrital age spectra to the age of a crystalline rock might be difficult (Condie et al., 2009), the Hf isotope ratios of U–Pb dated zircons allow a further specification of the provenance. It is possible to distinguish magmatic episodes that added juvenile mantle material to the conti- nental crust from episodes with recycling of the existing crust (e.g. Patchett et al., 1981; Patchett, 1983; Kinny et al., 1991; Scherer et al., 2001; Gerdes and Zeh, 2009). The same is possible with the whole- rock Sm–Nd isotope ratios, which are widely reported in the literature. The Lu–Hf and the Sm–Nd isotope systems behave in similar ways. Thus, a whole-rock Nd crustal residence age of a magmatic source rock can be compared directly to the Hf model age of the detrital zircon (Vervoort et al., 1999; Patchett et al., 2004). This methodology is very suitable for the study area in southern Peru and northern Bolivia (14°–17°S; Figs.1 and 2). There, Proterozoic to early Paleozoic crystalline basement rocks are restricted to isolated outcrops mainly in the Eastern Cordillera and the Arequipa Massif. These outcrops belong to different mobile belts accreted to the southwest of the Amazonian Craton, which are subject to subduction- related processes. The scarce basement outcrop occurrences represent a very fragmentary basis for understanding the geodynamic evolution of the Proterozoic to early Paleozoic Western Gondwana margin (14°– 17°S). In contrast, thick and widespread early Paleozoic sedimentary Gondwana Research xxx (2010) xxx–xxx ⁎ Corresponding author. Tel.: + 49 251 8333974; fax: + 49 251 8336108. E-mail address: reimannc@uni-munster.de (C.R. Reimann). GR-00468; No of Pages 15 1342-937X/$ – see front matter © 2010 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.gr.2010.02.002 Contents lists available at ScienceDirect Gondwana Research journal homepage: www.elsevier.com/locate/gr ARTICLE IN PRESS Please cite this article as: Reimann, C.R., et al., Geodynamic evolution of the early Paleozoic Western Gondwana margin 14°–17°S reflected by the detritus of the Devonian and Ordovician basins of southern Peru and ..., Gondwana Res. (2010), doi:10.1016/j.gr.2010.02.002