Preprints
https://doi.org/10.5194/se-2020-53
https://doi.org/10.5194/se-2020-53
14 May 2020
 | 14 May 2020
Status: this preprint was under review for the journal SE but the revision was not accepted.

Resolving uncertainties in the application of zircon Th / U and CL gauges to interpret U-Pb ages: a case study of eclogites in polymetamorphic terranes of NW Iberia

Pedro Castiñeiras, Juan Gómez Barreiro, Francisco J. Fernández, Carmen Aguilar, and José Manuel Benítez Pérez

Abstract. Zircon crystal texture and Th / U ratio have been used as a watertight argument when interpreting U-Pb ages. The wide, and sometimes indiscriminate, use of those gauges could result into misinterpretation of the geological meaning of U-Pb data. A case study is presented here where zircons from a controversial polymetamorphic eclogite unit were analyzed with SHRIMP. Both U-Pb and trace element (TE) data were collected for each point. The combination of TE and structural arguments indicates that zircon was part of the eclogite facies mineral assemblage at 390 Ma. However, using Th / U ratio and CL textures lead to a different interpretation. Our results suggest that in complex orogenic scenarios and extreme environments well-known techniques (CL) and geochemical relationships (Th / U) must be used in combination with TE data and structural relationships as provenance/process gauges. While geochronology provides accurate isotope relationships, their temporal dimension must rely on structural and petrological evidence.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Pedro Castiñeiras, Juan Gómez Barreiro, Francisco J. Fernández, Carmen Aguilar, and José Manuel Benítez Pérez
 
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Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Pedro Castiñeiras, Juan Gómez Barreiro, Francisco J. Fernández, Carmen Aguilar, and José Manuel Benítez Pérez
Pedro Castiñeiras, Juan Gómez Barreiro, Francisco J. Fernández, Carmen Aguilar, and José Manuel Benítez Pérez

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