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Return to Rodinia? Moderate to high palaeolatitude of the São Francisco/Congo craton at 920 Ma

Evans, D. A D; Trindade, R. I F; Catelani, E. L.; D'Agrella-Filho, M. S.; Heaman, L. M.; Oliveira, E. P.; Söderlund, U. LU ; Ernst, R. E.; Smirnov, A. V. and Salminen, J. M. (2015) In Geological Society Special Publication 424(1). p.167-190
Abstract

Moderate to high palaeolatitudes recorded in mafic dykes, exposed along the coast of Bahia, Brazil, are partly responsible for some interpretations that the São Francisco/Congo craton was separate from the low-latitude Rodinia supercontinent at about 1050 Ma. We report new palaeomagnetic data that replicate the previous results. However, we obtain substantially younger U-Pb baddeleyite ages from five dykes previously thought to be 1.02-1.01 Ga according to the 40Ar/39Ar method. Specifically, the so-called «A-normal» remanence direction from Salvador is dated at 924.2±3.8 Ma, within error of the age for the «C» remanence direction at 921.5±4.3 Ma. An «A-normal» dyke at Ilh»us is dated at 926.1±4.6 Ma, and two... (More)

Moderate to high palaeolatitudes recorded in mafic dykes, exposed along the coast of Bahia, Brazil, are partly responsible for some interpretations that the São Francisco/Congo craton was separate from the low-latitude Rodinia supercontinent at about 1050 Ma. We report new palaeomagnetic data that replicate the previous results. However, we obtain substantially younger U-Pb baddeleyite ages from five dykes previously thought to be 1.02-1.01 Ga according to the 40Ar/39Ar method. Specifically, the so-called «A-normal» remanence direction from Salvador is dated at 924.2±3.8 Ma, within error of the age for the «C» remanence direction at 921.5±4.3 Ma. An «A-normal» dyke at Ilh»us is dated at 926.1±4.6 Ma, and two «A-normal» dykes at Olivença have indistinguishable ages with best estimate of emplacement at 918.2±6.7 Ma. We attribute the palaeomagnetic variance of the «A-normal» and «C» directions to lack of averaging of geomagnetic palaeosecular variation in some regions. Our results render previous 40Ar/39Ar ages from the dykes suspect, leaving late Mesoproterozoic palaeolatitudes of the São Francisco/Congo craton unconstrained. The combined «A-normal» palaeomagnetic pole from coastal Bahia places the São Francisco/Congo craton in moderate to high palaeolatitudes at c. 920 Ma, allowing various possible positions of that block within Rodinia.

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author
organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
in
Geological Society Special Publication
volume
424
issue
1
pages
24 pages
publisher
Geological Society of London
external identifiers
  • Scopus:84966715272
ISSN
03058719
DOI
10.1144/SP424.1
language
English
LU publication?
yes
id
208f1d1b-4960-4ff7-8b56-0ea7229ae988
date added to LUP
2016-10-10 14:34:02
date last changed
2016-11-09 08:24:21
@misc{208f1d1b-4960-4ff7-8b56-0ea7229ae988,
  abstract     = {<p>Moderate to high palaeolatitudes recorded in mafic dykes, exposed along the coast of Bahia, Brazil, are partly responsible for some interpretations that the São Francisco/Congo craton was separate from the low-latitude Rodinia supercontinent at about 1050 Ma. We report new palaeomagnetic data that replicate the previous results. However, we obtain substantially younger U-Pb baddeleyite ages from five dykes previously thought to be 1.02-1.01 Ga according to the <sup>40</sup>Ar/<sup>39</sup>Ar method. Specifically, the so-called «A-normal» remanence direction from Salvador is dated at 924.2±3.8 Ma, within error of the age for the «C» remanence direction at 921.5±4.3 Ma. An «A-normal» dyke at Ilh»us is dated at 926.1±4.6 Ma, and two «A-normal» dykes at Olivença have indistinguishable ages with best estimate of emplacement at 918.2±6.7 Ma. We attribute the palaeomagnetic variance of the «A-normal» and «C» directions to lack of averaging of geomagnetic palaeosecular variation in some regions. Our results render previous <sup>40</sup>Ar/<sup>39</sup>Ar ages from the dykes suspect, leaving late Mesoproterozoic palaeolatitudes of the São Francisco/Congo craton unconstrained. The combined «A-normal» palaeomagnetic pole from coastal Bahia places the São Francisco/Congo craton in moderate to high palaeolatitudes at c. 920 Ma, allowing various possible positions of that block within Rodinia.</p>},
  author       = {Evans, D. A D and Trindade, R. I F and Catelani, E. L. and D'Agrella-Filho, M. S. and Heaman, L. M. and Oliveira, E. P. and Söderlund, U. and Ernst, R. E. and Smirnov, A. V. and Salminen, J. M.},
  issn         = {03058719},
  language     = {eng},
  month        = {05},
  number       = {1},
  pages        = {167--190},
  publisher    = {ARRAY(0xa66fb48)},
  series       = {Geological Society Special Publication},
  title        = {Return to Rodinia? Moderate to high palaeolatitude of the São Francisco/Congo craton at 920 Ma},
  url          = {http://dx.doi.org/10.1144/SP424.1},
  volume       = {424},
  year         = {2015},
}