HR: 1340h
AN: U23A-0866    [Abstracts]
TI: The Permo-Triassic Araguainha impact structure (central Brazil): impact products and collapse history in the central peak-ring
AU: * Yokoyama, E
EM: elder@iag.usp.br
AF: Instituto de Astronomia Geofisica e Ciencias Atmosfericas - USP, Rua do Matao 1226, Sao Paulo, SP 05508-090, Brazil
AU: Lana, C C
EM: lana@sun.ac.za
AF: Department of Geology -University of Stellenbosch, Private Bag X1-Matieland, Stellenbosch, WC 7620, South Africa
AU: Marangoni, Y R
EM: yara@iag.usp.br
AF: Instituto de Astronomia Geofisica e Ciencias Atmosfericas - USP, Rua do Matao 1226, Sao Paulo, SP 05508-090, Brazil
AU: Souza-Filho, C R
EM: beto@ige.unicamp.br
AF: Departamento de Geologia e Recursos Naturais, Instituto de Geociencias - UNICAMP, R. Joao Pandia Calogeras 51, Campinas, SP 13083-970, Brazil
AU: Tohver, E
EM: etohver@cyllene.uwa.edu.au
AF: School of Earth and Geographical Sciences Perth-University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
AU: Trindade, R I
EM: rtrindad@iag.usp.br
AF: Instituto de Astronomia Geofisica e Ciencias Atmosfericas - USP, Rua do Matao 1226, Sao Paulo, SP 05508-090, Brazil
AB: A meteorite impact hit central Brazil ca. 250 Ma ago, just prior to the Permo-Triassic boundary, leaving a 40 km wide complex impact structure (the largest impact structure identified in South America). It is a well-preserved and shallowly eroded crater, developed on sediments of the intracratonic Parana basin. The impact has excavated more than 2 km of the original sedimentary pile, bringing to the surface granites and host metamorphic rocks of the crystalline basement after collapse. It comprises a central peak ring, annular basin, two main ring features and deformed rims. Field observations and petrographic studies in impact-related materials inside the central peak ring allow recognition of six lithofacies (porphiritic-granite, foliated-granite, partially-molten granite, melt, polymitic breccias and pseudotachylytes) that record different magnetic fabrics. Porphiritic granite preserved the original igneous fabric orientation, whereas the other rocks record crater collapse, comprising foliated granites bellow a lid of strongly deformed partially molten rocks covered by breccias and melts. Comparison of these observations with available models of crater collapse will be discussed.
DE: 1518 Magnetic fabrics and anisotropy
DE: 5420 Impact phenomena, cratering (6022, 8136)
SC: Union [U]
MN: 2007 Fall Meeting