0.3 byr of drainage stability along the Palaeozoic palaeo-Pacific Gondwana margin; a detrital zircon study

Abstract

The palaeo-Pacific margin of Gondwana in the present-day south-central Andes is marked by tectonic activity related to subduction and terrane accretion. We present detrital zircon U-Pb data encompassing the Palaeozoic era in northern Chile and northwestern Argentina. Cathodoluminescence images reveal dominantly magmatic zircon barely affected by abrasion and displaying only one growth phase. The main age clusters for these zircon grains are Ediacaran to Palaeozoic with an additional peak at 1.3-0.9 Ga and they can be correlated with 'Grenvillian' age, and the Brasiliano, Pampean, and Famatinian orogenies. The zircon data reveal main transport from the nearby Ordovician Famatinian arc and related rocks. The Silurian sandstone units are more comparable with Cambrian units, with Brasiliano and Transamazonian ages (2.2-1.9 Ga) being more common, because the Silurian deposits were situated within or east of the (extinct) Famatinian arc. Hence, the arc acted as a transport barrier throughout Palaeozoic time. The complete suite of zircon ages does not record the accretions of exotic terranes or the Palaeozoic glacial periods. We conclude that the transport system along the palaeoPacific margin of Gondwana remained stable for c. 0.3 byr and that provenance data do not necessarily reflect the interior of a continent. Hence, inherited geomorphological features must be taken into account when detrital mineral ages are interpreted.

Pre-Pampean metasedimentary rocks from the Argentinian Puna: Evidence for the Ediacaran margin of Gondwana or the Arequipa–Antofalla–Western Pampeanas block

“…The succession discussed here contains detritus from a major Pre-Pampean igneous event (or several events) during the Ediacaran, similar to observations from other successions in the region, such as: the Puncoviscana Complex ; Cambrian rocks of the overlying Méson Group (Augustsson et al, 2011); Neoproterozoic and Paleozoic rocks in Peru (Chew et al, 2008); Devonian rocks in the Central Andes (Bahlburg et al, 2009); Paleozoic rocks in the Central Andes (Augustsson et al, 2015;Einhorn et al, 2015); and Silurian successions in Bolivia (Zimmermann et al, 2015b). In the entire region, however, PrePampean Ediacaran source rocks have not yet been found in outcrop.…”

“…This possibility was also considered by Adams et al (2010). Sedimentary successions overlying the Puncoviscana complex (Zimmermann, 2005) do contain this Pampean detrital information but not as a major component (e.g., references in Zimmermann et al, 2014;Augustsson et al, 2011Augustsson et al, , 2015Einhorn et al, 2015;Rapela et al, 2016).…”

The crustal evolution of South America from a zircon Hf‐isotope perspective

“…460 Ma; e.g. Pankhurst et al ., ; Augustsson et al ., , ), which is part of an extensive magmatic arc along major parts of Andean South America (Pankhurst et al ., ; Chew et al ., ; Horton et al ., ). The Famatinian arc, exposed at mid‐crustal level, had excess crustal thickness comparable to that of the present‐day central Andes (Lucassen and Franz, ; de los Hoyos et al ., ).…”

“…Furthermore, we trace crustal addition throughout the entire Palaeozoic era for the present‐day south‐central Andes. We combine the Hf data with published U–Pb ages from the same grains (Adams et al ., , ; Willner et al ., ; Augustsson et al ., , ).…”

“…(); (18) Breitkreuz (), Augustsson et al . (); (19) Isaacson and Dutro (); (20) Galli et al . (); (21) Rebolledo and Charrier (); (22) Hervé (), Willner et al .…”