GEOLOGY, GEOCHEMISTRY AND GEOCRONOLOGY OF THE GRANITIC ROCKS OF SAN IGNÁCIO OROGENY (BOLÍVIA)

Geology, geochemistry and geocronology of the granitic rocks of San Ignácio Orogeny (BOLÍVIA)

Authors

  • Gabriela Vargas MATTOS Universidade do Estado do Rio de Janeiro (UERJ), Rua São Francisco Xavier, 524, Maracanã, Rio de Janeiro, Brasil.
  • Mauro Cesar GERALDES Universidade do Estado do Rio de Janeiro
  • Armando D. TAVARES JÚNIOR Universidade do Estado do Rio de Janeiro (UERJ), Rua São Francisco Xavier, 524, Maracanã, Rio de Janeiro, Brasil
  • Ramiro Matos SALINAS Universidad Mayor de San Andrés (UMSA), Calle 27 de Cota Cota, Pabellon Geologia, Campus Universitário, Cota Cota, La Paz- Bolivia.
  • Wilson TEIXEIRA Instituto de Geociências, Universidade de São Paulo

DOI:

https://doi.org/10.5016/geociencias.v39i1.12805

Abstract

This contribution aims to characterize the Proterozoic granites of San Ignacio orogeny, western Bolivia, describing their chemical composition, U-Pb and Sm/Nd isotopic to identify sources and process of the crustal formation. The results of chemical and isotopic granitoids of Cachuela, Motacusal and Talcoso, present U/Pb age in zircon between 1307 and 1333 Ma, suggesting an important epoch of generation of granitoids in the Bolivian pre-Cambrian. Chemistry (A-Type granites) and Nd isotopes (εNd(1330) between -0.77 and -3.86) signatures here reported suggest an anorogenic environment and the spider diagram indicate the within-plates tectonic setting for the formation of these granites, instead of arc-related environment is suggested in the literature for these rocks. The data here reported suggest a geological evolution for the Bolivian pre-Cambrian composed of the San Ignacio event is represented by magmatic arc with participation of continental crust previously formed representing an important collisional period in the SW Amazonian craton.

Author Biographies

Mauro Cesar GERALDES, Universidade do Estado do Rio de Janeiro

Departamento de Mineralogia e Petrologia Ignea Area de Geocronologia

Ramiro Matos SALINAS, Universidad Mayor de San Andrés (UMSA), Calle 27 de Cota Cota, Pabellon Geologia, Campus Universitário, Cota Cota, La Paz- Bolivia.

Universidad Mayor de San Andrés (UMSA), Calle 27 de Cota Cota, Pabellon Geologia, Campus Universitário, Cota Cota, La Paz- Bolivia.

Wilson TEIXEIRA, Instituto de Geociências, Universidade de São Paulo

Instituto de Geociências, Universidade de São Paulo, Rua do Lago 562, Cidade Universitária, São Paulo – SP.

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Published

2020-05-19

Issue

Vol. 39 No. 1 (2020)

Section

Artigos