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Doctoral Thesis
DOI
10.11606/T.44.1995.tde-03062015-090005
Document
Author
Full name
Carlos Guarino Gomez Rifas
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1995
Supervisor
Committee
Sadowski, Georg Robert (President)
Campanha, Ginaldo Ademar da Cruz
Fiori, Alberto Pio
Jost, Hardy
Machado, Romulo
Title in Portuguese
A zona de cisalhamento sinistral "Sierra Ballena" no Uruguai.
Keywords in Portuguese
America do Sul
Geologia
Abstract in Portuguese
A zona de cisalhamento Sierra Ballena é um cinturão milonitico de até 6km de espessura e 75okm de comprimento formado por milonitos e ultramilonitos de diferentes tipos. Constitui o limite colisional entre o arco magmático de Pelotas e a margem passiva do Craton do Rio de La Plata. A temperatura e pressão de sua formação inicial dos milonitos oscilam no campo da fácies anfibólito, passando a xistos verdes e a feições rúpteis dos estágios tardios. Sua cinematica mostra ser essencialmente sinistral. Constitui simultaneamente com a zona de cisalhamento Além-Paraiba-Cubatão-Lancinha um dos sistemas de cisalhamento mais extensos do sudoeste de Gondwana. Sua reativação se deu durante vários períodos do Fanerozoico. O bloco leste é integrado por várias rochas graníticas aqui descritas, enquanto o bloco oeste apresenta granitos muito deformados, assim como uma sequência de rochas supracrustais do laualleja dobradas em dois eventos principais e características de sequência de margem passiva. Outra sequência supracrustal integrada por xistos miloniticos e possivelmente rochas vulcanicas, dominada por dobramento recumbente e foliação horizontal é descrita aqui pela primeira vez como Formação Fazenda el Fortim, situada entre o granito Aigua e a zona de cisalhamento sinistral Sierra Ballena.
Title in English
Not available.
Keywords in English
Not available.
Abstract in English
Sierra Ballena Shear Zone is a mylonitic belt 6 Km wide and 750 Km long. It is composed by rnylonites and uItramylonites of different types, due to differences in composition of protoliths and intensity of deformation. It is the last Pre-Devonian event in the Uruguay-Rio Grande do Sul Shield. S.B.S.S.Z. is the collisional border between the Pelotas magmatic arc and the passive margin of the Rio de La Plata craton. Her mylonites register a large activity time because they present features corresponding to "hot mylonites" as well as "cold" ones. Initial formation pressure and temperature correspond to amphibolite facies following to greenschist to brittle in the late stages. Her kinematics shows essentially a synistral component as part of simple shear as well as transtensional. It constitutes simultaneously with the Alem-Paraiba-Cubatão-Lancinha Shear Zone one of the most extensive shear belts of SW Gondwana. Her ractivation occur in Phanerozoic times affecting Paraná Basin sediments and performing the borders of Meso-Caenozoic basins. The eastern block is mainly integrated by various granitic rocks which are here described; meanwhile the western block exposses highly deformed granites, and a supracrustal sequence. The supractustal have been folded in two events and are integrated by limestones, dolomites, marbles, metamicroconglomerates, metasiltstones and acid, basic and intermediate metalavas, as well as reworked tuff ; all of the Lavalleja Group. A supracrustal sequence integrated by mylonitized schists and possible acid metavulcanic rocks, dominated by recumbent folding and horizontal foliation is described here for the first time: Fazenda El Fortin Formation, situated between the Aiguá Granite and S.B.S.S.Z.
 
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Rifas_Doutorado.pdf (43.22 Mbytes)
Publishing Date
2015-06-08
 
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