O maciço alcalino de Tunas, PR: novos dados geocronológicos

Authors

  • Oswaldo Siga Júnior Universidade de São Paulo; Instituto de Geociências; Departamento de Mineralogia e Geotectônica
  • Celso de Barros Gomes Universidade de São Paulo; Instituto de Geociências; Departamento de Mineralogia e Geotectônica
  • Kei Sato Universidade de São Paulo; Instituto de Geociências; Centro de Pesquisas Geocronológicas
  • Cláudia Regina Passarelli Universidade de São Paulo; Instituto de Geociências; Centro de Pesquisas Geocronológicas

DOI:

https://doi.org/10.5327/Z1519-874x2007000200005

Keywords:

geochronology, alkaline magmatism, alkaline Tunas massif

Abstract

The NW-SE elongated Tunas intrusion, occupying an area of 22 km², crops out about 80 km from the city of Curitiba, and it is emplaced into Precambrian metavolcanic-sedimentary rocks of the Açungui Group. Five sub-circular volcanic structures are recognized. Petrographically, the massif mainly consists of syenites and alkali syenites with subordinate alkali gabbros, essexites, syenogabbros and syenodiorites; small late syenitic dykes and magmatic breccias are also found. Previous K-Ar data give a Late Cretaceous mean age of 82.2 Ma for Tunas rocks. In this article we present new U-Pb age determinations on zircon crystals from syenitic rocks (ID-TIMS, 82.7 ± 0.7 Ma; SHRIMP, 84.7 ± 1.2 Ma) which confirm that age, placing the massif into the Late Cretaceous group of alkaline intrusions tectonically associated with the São Jerônimo-Curiúva Lineament, a NW-SE-trending branch of the Ponta Grossa Arch in southern Brazil.

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Published

2007-10-01

Issue

Vol. 7 No. 2 (2007)

Section

Articles

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How to Cite

Siga Júnior, O., Gomes, C. de B., Sato, K., & Passarelli, C. R. (2007). O maciço alcalino de Tunas, PR: novos dados geocronológicos . Geologia USP. Série Científica, 7(2), 71-80. https://doi.org/10.5327/Z1519-874x2007000200005