HR: 0800h
AN: GP21A-08    [Abstracts]
TI: Paleomagnetism of paleoproterozoic mafic and felsic volcanic rocks of the Rio Negro- Juruena Province, Southwestern Amazonian Craton, Brazil
AU: Bispo-Santos, F
EM: frankb@iag.usp.br
AF: Instituto de Astronomia, Geofisica e Ciencias Atmosfericas - Universidade de Sao Paulo, Rua do Matao, 1226, Sao Paulo, SP 05508-090, Brazil
AU: * D'Agrella-Filho, M S
EM: dagrella@iag.usp.br
AF: Instituto de Astronomia, Geofisica e Ciencias Atmosfericas - Universidade de Sao Paulo, Rua do Matao, 1226, Sao Paulo, SP 05508-090, Brazil
AU: Elming, S
EM: Sten-Ake.Elming@ltu.se
AF: Department of Applied Geophysics - Lulea University of Tecnology, Lulea S-95187, Lulea,
AB: Several paleogeographic configurations for the Amazonian Craton have been suggested along its geological history. Paleomagnetic tests for suggested configurations are however restricted due to very sparce and low quality paleomagnetic data, especially for Paleoproterozoic. In an attempt to improve our understanding of the geodynamic evolution, a paleomagnetic study was performed on felsic volcanic rocks of the Colider Suite, and associated mafic rocks in the Rio Negro-Juruena Province, southwestern Amazonian Craton. These rocks have well dated zircon U-Pb ages between 1.80-1.78 Ga. Very stable northern (southern) directions with moderate to steep negative (positive) inclinations were isolated during AF and thermal demagnetization. Rock magnetism experiments show that the magnetization, which is probably of primary origin, in the felsic rocks is carried by hematite and in the mafic rocks by Ti-poor titanomagnetite. A preliminary mean direction (D=187.4°, I=50.9°, N=16, A95=11.3°, K=11.7) yield a paleomagnetic pole located at 289.4°E, 65.4°S (A95=12.9°), which is classified with quality factor of Q=5. Paleogeographic reconstructions using key Paleoproterozoic poles suggest that Laurentia, Baltica, North China, and Amazonian Craton were located in laterally contiguous positions forming a large continental mass at 1.83-1.77 Ga ago.
DE: 1519 Magnetic mineralogy and petrology
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 1540 Rock and mineral magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly