Ar-40/Ar-39 geochronology of the Fernando de Noronha Archipelago and implications for the origin of alkaline volcanism in the NE Brazil

Perlingeiro, Gabriela, Vasconcelos, Paulo M., Knesel, Kurt M., Thiede, David S. and Cordani, Umberto G. (2013) Ar-40/Ar-39 geochronology of the Fernando de Noronha Archipelago and implications for the origin of alkaline volcanism in the NE Brazil. Journal of Volcanology and Geothermal Research, 249 140-154. doi:10.1016/j.jvolgeores.2012.08.017


Author Perlingeiro, Gabriela
Vasconcelos, Paulo M.
Knesel, Kurt M.
Thiede, David S.
Cordani, Umberto G.
Title Ar-40/Ar-39 geochronology of the Fernando de Noronha Archipelago and implications for the origin of alkaline volcanism in the NE Brazil
Formatted title
40Ar/39Ar geochronology of the Fernando de Noronha Archipelago and implications
for the origin of alkaline volcanism in the NE Brazil
Journal name Journal of Volcanology and Geothermal Research   Check publisher's open access policy
ISSN 0377-0273
1872-6097
Publication date 2013-01
Year available 2012
Sub-type Article (original research)
DOI 10.1016/j.jvolgeores.2012.08.017
Volume 249
Start page 140
End page 154
Total pages 15
Place of publication Amsterdam, Netherlands
Publisher Elsevier
Collection year 2014
Language eng
Abstract The Fernando de Noronha archipelago, centered ~250km off the northeastern coast of Brazil, is comprised of a diverse suite of alkaline volcanic rocks commonly associated with a mantle-plume origin. Although previous K-Ar determinations divide the three main volcanic formations of the archipelago (Remédios, Quixaba and São José formations) into two age groups, a few ages conflicting with the stratigraphic framework were suspected to suffer from excess argon. To evaluate the presence or absence of excess Ar and to improve the geochronological database for the archipelago, we have dated, by the laser incremental-heating 40Ar/39Ar method, the exact same hand specimens previously dated by K-Ar. The 22 samples studied here yield plateau ages for at least one of the two grains analyzed and none of the specimens contain significant excess Ar. Our results derive a chronostratigraphic sequence for the archipelago that is consistent with the earlier K-Ar determinations. The main discrepancy is related to some basanitic rocks of São José formation, interpreted as the youngest eruptive products which are in fact coeval with the oldest subareal volcanic activity at Fernando de Noronha. Our revised eruptive chronology defines a hiatus of nearly 3Ma separating an older period of volcanism between 12.5±0.1 and 9.0±0.1Ma comprising the Remédios and São José formations and a younger episode forming the Quixaba formation between 6.2±0.1 and 1.3±0.1Ma. Moreover, these results confirm that much of the activity at Fernando de Noronha was contemporaneous with alkaline volcanism well onshore in northeastern Brazil, supporting the suggestion that this hotspot may be a product of small-scale, plate-driven convection in the upper mantle.
Keyword Alkaline volcanism
Ar-40/Ar-39 geochronology
Edge-driven convection
Mantle plume
South Atlantic Ocean
40Ar/39Ar geochronology
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Available online: 4 September 2012.

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2014 Collection
School of Earth Sciences Papers
 
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