Tracing Crustal Evolution in the Southern Central Andes from Late Precambrian to Permian with Geochemical and Nd and Pb Isotope Data

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Abstract
Major and trace element abundances and Nd and Pb isotopes of sedimentary and igneous rocks of Late Proterozoic to Permian age from northwest Argentina and northern Chile (northern Puna) have been analyzed to evaluate paleogeographic reconstructions and the crustal evolution of the Pacific margin of Gondwana during the Paleozoic. Recycling of material solely derived from preexisting material of western Gondwana can explain the isotope compositions of the sedimentary samples. Major and trace element compositions of the sedimentary samples are similar to upper continental crust and show no systematic changes during the Paleozoic. Pre‐Ordovician and Ordovician sedimentary samples of the eastern belt of the northern Puna have homogeneous crustal εNd (450 Ma) values of (TDM = 1.6 to 1.8 Ga). A range of about six ε‐units (εNd to −1.3) is observed within the Arenigian Volcanosedimentary Successions, indicating the appearance of a short‐lived juvenile source. All samples of the overlying Puna Turbidite Complex show a narrow range of crustal εNd (450 Ma) values ( ). Late Paleozoic sedimentary samples from northern Chile (εNd to −4) are comparable to the Ordovician values and may be derived from local sources such as the Ordovician granitoids of the Cordón de Lila Complex (εNd to −5.4) or by recycling of the Volcanosedimentary Successions. They require no exotic source. Pb isotope data support the homogeneous makeup of the margin indicated by the Nd isotopes. We did not find evidence for juvenile arc magmatism or obduction of ocean floor