Autor(es)

D'Agrella-Filho, Manoel S. ^[1] ; Trindade, Ricardo I. F. ^[1] ; Queiroz, Marcelo V. B. ^[1] ; Meira, Vinicius T. ^[1] ; Janikian, Liliane ^[2] ; Ruiz, Amarildo S. ^[3] ; Bispo-Santos, Franklin ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, Rua Matao 1226, BR-05508090 Sao Paulo - Brazil

^[2] Inst Mar, Dept Ciencias Mar, Unidade 11, UNIFESP, Campus Baixada Santista, Av Alm Saldanha Gama 89, Santos, SP - Brazil

^[3] Univ Fed Mato Grosso, Dept Geol, Inst Ciencias Exatas & Terra, Av Fernando Correa Costa S-N, BR-78060900 Cuiaba - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Precambrian Research; v. 272, p. 1-17, JAN 2016.
• Citações Web of Science: 7

Resumo

The Aguapei paleomagnetic pole obtained for mafic sills and dykes from Salto do Ceu region at the western margin of the Amazonian Craton constrains its links with Baltica and Laurentia in Rodinian reconstructions. A new U-Pb age on baddeleyite at 1439 +/- 4 Ma for the intrusives, contrasts strongly with a previous Ar-Ar age at 981 +/- 2 Ma, with important consequences for paleogeographic reconstructions. We report new paleomagnetic and magnetic anisotropy results for sills from the Salto do Ceu region and reassess the paleomagnetic data in view of the new geochronological age. A total of 155 samples were collected from thirteen new paleomagnetic sampling sites, five of them corresponding to sedimentary rocks located at the borders of the sills in an attempt to perform baked contact tests. After thermal and alternating field demagnetization, the sills provided a characteristic magnetic component at D-m=208.2 degrees, I-m=68.5 degrees (N=8, alpha(95)=6.4), with a corresponding paleomagnetic pole at 46.4 degrees S; 277.0 degrees E (A(95)=10.2 degrees). Directions obtained in this study are similar to those reported previously for other mafic sills and dykes in the same region. A pole integrating the new results for the sills with those of the previous Aguapei pole is situated at 56.0 degrees S; 278.5 degrees E (A(95)=7.9 degrees). This new combined Salto do Ceu pole supersedes the previous Aguapei pole. Magnetic mineralogy studies, optical and electronic microscopy indicates PSD magnetite as the main magnetic carrier in these rocks. The baked contact tests were inconclusive, but the similarity between Salto do Ceu pole and other high-quality poles with ages around 1420-1430 Ma suggests they carry a primary thermoremanence of that age. The Salto do Ceu and other coeval poles are compatible with a connection between Amazonia and Baltica at the Mesoproterozoic in a paleogeographic configuration slightly different from SAMBA (South America-Baltica). At the same time, the new geochronological and paleomagnetic data imply that all paleogeographic interpretations for the position of Amazonia in Rodinia based on the previously published Aguapei pole (and now renamed as Salto do Ceu pole) must be revised. (C) 2015 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 12/50327-3 - O craton amazonico e o supercontinente columbia:implicacoes paleogeograficas baseadas no estudo paleomagnetico de unidades geologicas paleo-mesoproterozoicas.
• Beneficiário: Franklin Bispo dos Santos
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 11/50887-6 - Paleomagnetismo de unidades proterozoicas do craton amazonico e sua participacao nos supercontinentes columbia, rodinia e gondwana.
• Beneficiário: Manoel Souza D'Agrella Filho
• Modalidade de apoio: Auxílio à Pesquisa - Regular