The 1420 Ma Indiavai Mafic Intrusion (SW Amazonian Craton): Paleomagnetic results and implications for the Columbia supercontinent

Autor(es)

D'Agrella-Filho, Manoel S. ^[1] ; Trindade, Ricardo I. F. ^[1] ; Elming, Sten-Ake ^[2] ; Teixeira, Wilson ^[3] ; Yokoyama, Elder ^[1] ; Tohver, Eric ^[4] ; Geraldes, Mauro C. ^[5] ; Pacca, Igor I. G. ^[1] ; Barros, Marcia A. S. ^[6] ; Ruiz, Amarildo S. ^[6]

Afiliação do(s) autor(es)

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

^[2] Lulea Univ Technol, Div Ore Geol & Appl Geophys, S-95187 Lulea - Sweden

^[3] Univ Sao Paulo, Inst Geociencias, BR-05508080 Sao Paulo - Brazil

^[4] Univ Western Australia, Sch Earth & Geog Sci, Crawley, WA 6009 - Australia

^[5] Univ Estado Rio de Janeiro, Fac Geol, BR-20550013 Rio De Janeiro - Brazil

^[6] Univ Fed Mato Grosso, Dept Geol, Inst Ciencias Exatas & Terra, BR-78060900 Cuiaba - Brazil

• Tipo de documento: Artigo Científico
• Fonte: GONDWANA RESEARCH; v. 22, n. 3-4, p. 956-973, NOV 2012.
• Citações Web of Science: 27

Resumo

The configuration and the timing of assembly and break-up of Columbia are still matter of debate. In order to improve our knowledge about the Mesoproterozoic evolution of Columbia, a paleomagnetic study was carried out on the 1420 Ma Indiavai mafic intrusive rocks that crosscut the polycyclic Proterozoic basement of the SW Amazonian Craton, in southwestern Mato Grosso State (Brazil). Alternating field and thermal demagnetization revealed south/southwest ChRM directions with downward inclinations for sixteen analyzed sites. These directions are probably carried by SD/PSD magnetite with high coercivities and high unblocking temperatures as indicated by additional rock magnetic tests, including thermomagnetic data, hysteresis data and the progressive acquisition of isothermal remanent magnetization. Different stable magnetization components isolated in host rocks from the basement 10 km NW away to the Indiavai intrusion, further support the primary origin of the ChRM. A mean of the site mean directions was calculated at Dm = 209.8 degrees, Im = 50.7 degrees (alpha(95) = 8.0 degrees, K = 22.1), which yielded a paleomagnetic pole located at 249.7 degrees E, 57.0 degrees S (A(95) = 8.6 degrees). The similarity of this pole with the recently published 1420 Ma pole from the Nova Guarita dykes in northern Mato Grosso State suggests a similar tectonic framework for these two sites located 600 km apart, implying the bulk rigidity of the Rondonian-San Ignacio crust at that time. Furthermore these data provide new insights on the tectonic significance of the 1100-1000 Ma Nova Brasilandia belt-a major EW feature that cuts across the basement rocks of this province, which can now be interpreted as intracratonic, in contrast to previous interpretation. From a global perspective, a new Mesoproterozoic paleogeography of Columbia has been proposed based on comparison of these 1420 Ma poles and a 1780 Ma pole from Amazonia with other paleomagnetic poles of similar age from Baltica and Laurentia, a reconstruction in agreement with geological correlations. (C) 2012 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 07/59531-4 - Paleogeografia do Cráton Amazônico durante o Proterozóico na formação de supercontinentes
• Beneficiário: Manoel Souza D'Agrella Filho
• Linha de fomento: Auxílio à Pesquisa - Regular
• Processo FAPESP: 07/53177-4 - Estudo paleomagnético de unidades paleoproterozóicas do Cráton Amazônico
• Beneficiário: Franklin Bispo dos Santos
• Linha de fomento: Bolsas no Brasil - Doutorado
• Processo FAPESP: 11/50887-6 - Paleomagnetismo de unidades proterozóicas do Cráton Amazônico e sua participação nos supercontinentes Columbia, Rodinia e Gondwana
• Beneficiário: Manoel Souza D'Agrella Filho
• Linha de fomento: Auxílio à Pesquisa - Regular