Petrologic and thermobarometric study of the Riás schists (NW Iberian Massif)

  1. Byron Ernesto Solís-Alulima 1
  2. Alicia López-Carmona 1
  3. Gabriel Gutiérrez-Alonso 1
  4. Antonio M. Álvarez-Valero 1
  1. 1 Universidad de Salamanca
    info

    Universidad de Salamanca

    Salamanca, España

    ROR https://ror.org/02f40zc51

Journal:
Boletín geológico y minero

ISSN: 0366-0176

Year of publication: 2019

Volume: 130

Issue: 3

Pages: 445-464

Type: Article

DOI: 10.21701/BOLGEOMIN.130.3.004 DIALNET GOOGLE SCHOLAR lock_openOpen access editor

More publications in: Boletín geológico y minero

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Abstract

The Riás Schists crop out in the so-called Iberian Variscan parautochthon, surrounding the Malpica-Tui Complex (NW Iberian Massif), as part of the westernmost internal areas of the European Variscan belt. Three Variscan metamorphic events have been identified in the Riás Schists (M1, M2 and post-M2). M1 comprise unoriented microinclusions that have only been identified in garnet porphyroblast cores and inside staurolite crystals. M2, comprises the matrix foliation (S2) and the assemblage garnetRIM + staurolite + muscovite + biotite + chlorite + rutile/ilmenite + magnetite + quartz and the development of syntectonic andalusite. Finally, postM2 (post-S2) includes andalusite and plagioclase together with secondary muscovite, biotite and chlorite and accessory tourmaline, Fe/Ti oxides, apatite and carbonate. Results of multi-equilibrium thermobarometry (pressure-temperature pseudosections), for M2 indicates a medium-pressure Barrovian metamorphic event (0.5-0.6 GPa; 580-570 o C; ca. 20 km deep), followed by moderate cooling during decompression, together with the extensional collapse of the Variscan orogenic pile (post-M2; 0.3 GPa; 540 o C; ca. 10 km deep). Inferred P T conditions in the Riás Schists, and their spatial relationship with the overlying allochthonous high-pressure pelitic schists (i.e. Ceán Schists), suggest that both lithologies were part of the same continental margin during the beginning of the Variscan orogeny. However, they experienced very different tectonothermal evolutions due to their putative locations in the orogenic wedge.

Funding information

This work has been funded by the Spanish Ministry of Economy and Competitiveness under the project ODRE III-Oroclines & Delamination: Relations & Effects (CGL2013-46061-P) and the project Origin, metallogeny, climatic effects, and cyclical large igneous provinces (14.Y26.31.0012; Russian Federation). A. López-Carmona was also funded by a “Juan de la Cierva” grant (reference FJCI-2014-20740). We thank J. Abati and P. Lozano from the Mineralogy and Petrology Department from the UCM for having provided the samples for this study, and A. Fernández Larios from the ICTS ⁄CNME-UCM for his technical support. We also thank J. Escuder Viruete and F.J. Rubio Pascual for insightful reviews that largely contributed to improving this paper and to E. Pardo-Igúzquiza for his editorial handling.

Funders

    • FJCI-2014-20740