Abstract
Suggestions that the Precordillera of Argentina has an early Paleozoic connection to the Appalachian-Ouachita rifted margin of the southern U.S. have been based on Cambro-Ordovician stratigraphy and faunal assemblages. Further support comes from comparing Precambrian Grenville Appalachian basement with xenoliths brought up in Precordil-leran Miocene volcanic rocks. U-Pb zircon ages and whole rock Pb and Nd isotopic data from the xenoliths show that Precordilleran basement, along with some part of the westernmost Sierras Pampeanas (Pie de Palo Range) to the east, is essentially unique in South America and is best interpreted as being derived from Laurentia. A Grenville age is substantiated by U/Pb zircon upper intersect ages of $$1102 \pm 6 Ma$$ for a mafic xenolith and near-1100 Ma for acidic xenoliths. Both xenolith types contain pink, doubly terminated prismatic igneous zircons with relatively high U and Pb concentrations. Rounded, colorless, low U and Pb zircons with overgrowths produced in a later Pre...
Published Version
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