K-Ar and 40Ar/39Ar ages of dikes emplaced in the onshore basement of the Santos Basin, Resende area, SE Brazil: implications for the South Atlantic opening and tertiary reactivation

Guedes, E., Heilbron, M., Vasconcelos, P. M. D., Valeriano, C. D., Almeida, J. C. H., Teixeira, W. and Filho, A. T. (2005) K-Ar and 40Ar/39Ar ages of dikes emplaced in the onshore basement of the Santos Basin, Resende area, SE Brazil: implications for the South Atlantic opening and tertiary reactivation. Journal of South American Earth Sciences, 18 3-4: 371-382. doi:10.1016/j.jsames.2004.11.008


Author Guedes, E.
Heilbron, M.
Vasconcelos, P. M. D.
Valeriano, C. D.
Almeida, J. C. H.
Teixeira, W.
Filho, A. T.
Title K-Ar and 40Ar/39Ar ages of dikes emplaced in the onshore basement of the Santos Basin, Resende area, SE Brazil: implications for the South Atlantic opening and tertiary reactivation
Journal name Journal of South American Earth Sciences   Check publisher's open access policy
ISSN 0895-9811
Publication date 2005-01-01
Sub-type Article (original research)
DOI 10.1016/j.jsames.2004.11.008
Open Access Status Not yet assessed
Volume 18
Issue 3-4
Start page 371
End page 382
Total pages 12
Editor Kellogg, J. N.
Place of publication Oxford
Publisher Pergamon
Language eng
Subject C1
260109 Geochronology
780104 Earth sciences
040303 Geochronology
040304 Igneous and Metamorphic Petrology
Abstract New K-Ar and Ar-40/Ar-39 data of tholeiitic and alkaline dike swarms from the onshore basement of the Santos Basin (SE Brazil) reveal Mesozoic and Tertiary magmatic pulses. The tholeiitic rocks (basalt, dolerite, and microgabbro) display high TiO2 contents (average 3.65 wt%) and comprise two magmatic groups. The NW-oriented samples of Group A have (La/Yb)N ratios between 15 and 32.3 and range in age from 192.9 +/- 2.2 to 160.9 +/- 1.9 Ma. The NNW-NNE Group B samples, with (La/Yb)(N) ratios between 7 and 16, range from 148.3 +/- 3 to 133.9 +/- 0.5 Ma. The alkaline rocks (syenite, trachyte, phonolite, alkaline basalts, and lamprophyre) display intermediate-K contents and comprise dikes, plugs, and stocks. Ages of approximately 82 Ma were obtained for the lamprophyre dikes, 70 Ma for the syenite plutons, and 64-59 Ma for felsic dikes. Because Jurassic-Early Cretaceous basic dikes have not been reported in SE Brazil, we might speculate that, during the emplacement of Group A dikes, extensional stresses were active in the region before the opening of the south Atlantic Ocean and coeval with the Karoo magmatism described in South Africa. Group B dikes yield ages compatible with those obtained for Serra Geral and Ponta Grossa magmatism in the Parana Basin and are directly related to the breakup of western Gondwana. Alkaline magmatism is associated with several tectonic episodes that postdate the opening of the Atlantic Ocean and related to the upwelling of the Trindade plume and the generation of Tertiary basins southeast of Brazil. In the studied region, alkaline magmatism can be subdivided in two episodes: the first one represented by lamprophyre dykes of approximately 82 Ma and the second comprised of felsic alkaline stocks of approximately 70 Ma and associated dikes ranging from 64 to 59 Ma. (c) 2005 Elsevier Ltd. All rights reserved.
Keyword Geosciences, Multidisciplinary
dike swarm
tholeitiic
southeast Brazil
Obliquely Rifted Margin
Parana Flood Volcanism
Southeastern Brazil/
Rocks
Geochronology
Campos
Q-Index Code C1
Institutional Status UQ

 
Versions
Version Filter Type
Citation counts: TR Web of Science Citation Count  Cited 26 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 37 times in Scopus Article | Citations
Google Scholar Search Google Scholar
Created: Wed, 15 Aug 2007, 17:49:17 EST