Tectonic implications of the 1419 Ma Nova Guarita mafic intrusives paleomagnetic pole (Amazonian Craton) on the longevity of Nuna

Author(s)

Bispo-Santos, Franklin ^[1] ; D'Agrella-Filho, Manoel S. ^[1] ; Trindade, Ricardo I. F. ^[1] ; Elming, Sten-Ake ^[2] ; Janikian, Liliane ^[1] ; Vasconcelos, Paulo M. ^[3] ; Perillo, Bruno M. ^[1] ; Pacca, Igor I. G. ^[1] ; da Silva, Jesue A. ^[4] ; Barros, Marcia A. S. ^[5]

Affiliation

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

^[2] Lulea Univ Technol, S-95187 Lulea - Sweden

^[3] Univ Queensland, Brisbane, Qld 4072 - Australia

^[4] Companhia Matogrossense Mineracao METAMAT, BR-78050300 Cuiaba, MT - Brazil

^[5] Univ Fed Mato Grosso, UFMT, BR-78068505 Cuiaba, MT - Brazil

• Document type: Journal article
• Source: Precambrian Research; v. 196, p. 1-22, FEB 2012.
• Web of Science Citations: 31

Abstract

The Nuna supercontinent was probably assembled in the Paleoproterozoic, but its paleogeography and the timing for its demise are stills matter of debate. A paleomagnetic and geochronological study carried out on the Mesoproterozoic Nova Guarita dyke swarm (northern Mato Grosso State, SW Amazonian Craton) provides additional constraints on the duration of this supercontinent. Paleomagnetic AF and thermal treatment revealed south/southwest (northeast) magnetic directions with downward (upward) inclinations for 19 analyzed sites. These directions are carried by PSD magnetite with high unblocking temperatures as indicated by additional magnetic tests, including thermomagnetic curves, hysteresis loops and the progressive acquisition of isothermal remanence in selected samples. A positive contact test with the host granite in one of the studied dykes further attests to the primary origin of the characteristic magnetic component. A mean site direction was calculated at D-m = 220.5 degrees, I-m = 45.9 degrees (alpha(95) = 6.5 degrees, K = 27.7), which yielded a paleomagnetic pole located at 245.9 degrees E, 47.9 degrees S (A(95) = 7.0 degrees). Ar-40/Ar-39 dating carried out on biotites from four analyzed dykes yielded well-defined plateau ages with a mean of 1418.5 +/- 3.5 Ma. The Nova Guarita pole precludes a long-lived Nuna configuration in which Laurentia, Baltica, North China, and Amazonia formed a long and continuous block as previously proposed for the Paleoproterozoic. It is nevertheless fully compatible with a SAMBA (Amazonia-Baltica) link at Mesoproterozoic times. (C) 2011 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 11/50887-6 - Paleomagnetism of proterozoic geological units from the Amazonian Craton, and its participation in the Columbia, Rodinia, and Gondwana supercontinents
• Grantee: Manoel Souza D'Agrella Filho
• Support Opportunities: Regular Research Grants