Artículos de revistas
Paleogeography Of The Congo/sao Francisco Craton At 1.5 Ga: Expanding The Core Of Nuna Supercontinent
Registro en:
Precambrian Research. Elsevier Science Bv, v. 286, p. 195 - 212, 2016.
0301-9268
1872-7433
WOS:000389104000010
10.1016/j.precamres.2016.09.011
Autor
Salminen
J. M.; Evans
D. A. D.; Trindade
R. I. F.; Oliveira
E. P.; Piispa
E. J.; Smirnov
A. V.
Institución
Resumen
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The Congo/Sao Francisco (C/SF) craton, one of the largest cratons in Proterozoic paleogeography, has been lacking reliable paleomagnetic data for the supercontinent Nuna interval (ca. 1600-1300 Ma). Here we provide a new paleomagnetic key pole for this craton from recently dated mafic dykes in the Curaca (1506.7 +/- 6.9 Ma) region of Brazil. The characteristic remanent magnetization (ChRM) direction D = 070.6 degrees, I = 54.0 degrees (k = 22.1 and a(95) = 13.1 degrees) corresponds with a paleomagnetic pole at 10.1 degrees N, 009.6 degrees E (K = 15.6, A(95) 15.8 degrees), which places C/SF craton in moderate paleolatitudes at the time of remanence acquisition. Primary nature of the paleomagnetic remanence is supported by a baked-contact test. A similar ChRM direction was obtained for four Mesoproterozoic mafic intrusions in Chapada Diamantina region. The new pole, only from Curaca, for C/SF allows us to reconstruct the extended core of the supercontinent Nuna at 1.5 Ga. Based on coeval 1.5 Ga and 1.38 Ga magmatism in Baltica, Siberia and C/SF, we favor the position where Southwest Congo is reconstructed against present South -Southeast (S-SE) Baltica. We explore two alternative 1.5 Ga reconstructions of Nuna's core. In both of them Baltica and Laurentia are shown in the well-defined NENA (Northern Europe North America) fit, together with Siberia in a tight fit to northern Laurentia. In reconstruction option A, more traditional fit of Amazonia with Baltica is shown, modified from the geologically based SAMBA (South AMerica BAltica) model to accommodate paleomagnetic data. In this option, however, West Africa must be extricated from SAMBA because C/SF has taken its place. For reconstruction option B, Amazonia is shifted to lie adjacent to NE Laurentia and West Baltica. In both options SW Congo is reconstructed against S-SE Baltica, but in option B there is a tighter fit between them, and there is a better match with our new paleomagnetic data for C/SF. In either option, separation of C/SF from Baltica and Siberia probably occurred at 1.38 Ga, the age of pronounced mafic magmatism throughout this sector of Nuna. (C) 2016 Elsevier B.V. All rights reserved. 286 195 212 Academy of Finland Alfred Kordelin Foundation NSF [EAR-1149434] Brazilian CNPq grant [304934/2014-3, 305658/2015-8] Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)