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The geological roots of South America: 4.1 Ga and 3.7 Ga zircon crystals discovered in N.E. Brazil and N.W. Argentina

Jean-Louis Paquette 1 J.S.F. Barbosa 2 Sébastien Rohais 3 S.C.P. Cruz 2 Philippe Goncalves 4 Jean-Jacques Peucat 5 A.B.M. Leal M. Santos-Pinto Hervé Martin 6
1 LMV - Laboratoire Magmas et Volcans
2 Institute of geosciences
3 Direction Géologie-Géochimie-Géophysique
4 LCE - Laboratoire Chrono-environnement - UFC (UMR 6249)
5 GR - Géosciences Rennes
6 LMV - Laboratoire Magmas et Volcans
Abstract : We present new LA-ICP-MS in situ geochronological results for seven Eoarchean zircons dated at 3.7 Ga coming from Cretaceous ash layers of NW Argentina and one Hadean single crystal sampled within the São Francisco Craton in NE Brazil. This zircon comprises a zoned magmatic core dated at 4.1 Ga surrounded by a 1.9 Ga overgrowth related to Paleoproterozoic reworking. This Hadean age is consistent with previously published Nd model ages on orthogneisses from the same domain. These two results represent among the oldest geological witnesses discovered to date in South America, which demonstrates the occurrence of a primitive crust. The contrasting age patterns recorded in both samples and localities indicate that at least two different nuclei of early crust survived in the continental domain. The São Francisco Craton in Brazil can be now considered as one of the very few areas where rare occurrences of Hadean zircon record the early evolution of the Earth.
Keywords : Primitive crust Salta rift Argentina U–Pb zircon dating Laser ablation ICP-MS Hadean Sao Francisco Craton Brazil
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https://hal-insu.archives-ouvertes.fr/insu-01252420
Contributor : Isabelle Dubigeon <>
Submitted on : Thursday, January 7, 2016 - 3:30:02 PM
Last modification on : Thursday, September 17, 2020 - 8:36:05 AM

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INSU | CNRS | UNIV-FCOMTE | UNIV-RENNES1 | GR | IFP | LMV | OSUR | PRES_CLERMONT | UNIV-ST-ETIENNE | CHRONO-ENVIRONNEMENT | UNIV-RENNES | OPGC | UDL

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Jean-Louis Paquette, J.S.F. Barbosa, Sébastien Rohais, S.C.P. Cruz, Philippe Goncalves, et al.. The geological roots of South America: 4.1 Ga and 3.7 Ga zircon crystals discovered in N.E. Brazil and N.W. Argentina. Precambrian Research, Elsevier, 2015, 271, pp.49-75. ⟨10.1016/j.precamres.2015.09.027⟩. ⟨insu-01252420⟩

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