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Doctoral Thesis
DOI
10.11606/T.44.1994.tde-04102013-151926
Document
Author
Full name
Ciro Teixeira Correia
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1994
Supervisor
Committee
Girardi, Vicente Antonio Vitorio (President)
Candia, Maria Angela Fornoni
Guttler, Rainer Aloys Schultz
Jost, Hardy
Schrank, Alfonso
Title in Portuguese
Petrologia do complexo máfico-ultramáfico de Cana Brava, Goiás
Keywords in Portuguese
Petrologia
Abstract in Portuguese
O Complexo de Cana Brava corresponde a um corpo ígneo estratiforme, máfico-ultramáfico, anorogênico originado da cristalização fracionada de magma basáltico de composição olivina toleítica. Relações de campo indicam que a massa magmática original intrudiu as rochas pré-existentes já deformadas e metamorfisadas da sequência vulcano-sedimentar de Palmeirópolis. Os dados geoquímicos e petrológicos indicam que a cristalização se processou em condições de pressão inferiores a 7 kbar. O empilhamento original do Complexo é interpretado como tendo sido constituído da base para o topo por microgabros, peridotitos, websteritos e rochas gabróides variadas. Os reequilibrios minerais, o padrão de deformação e as determinações isotópicas disponíveis levaram à interpretação de que o Complexo de Cana Brava evoluiu segundo as seguintes etapas tectônicas: a) separação do manto e residência sublitosférica ou subcrustal do magma progenitor entre 2,25 e 2,62 b.a.; b) intrusão na Sequência vulcano-sedimentar de Palmeirópolis e cristalização subsequente em regime distensivo ao redor de 2,0 b.a.; c) evento principal de deformação dúctil-rúptil, em regime compressivo, ao redor de 1,3 b.a.; d) reequilíbrios metamórficos posteriores em idades Brasilianas ainda não bem estabelecidas. Estes eventos transformaram a sequência original de suas rochas da base para o topo em: anfibolitos, serpentinitos, metawebsteritos e metagabros.
Keywords in English
Not available.
Abstract in English
The anorogenic Cana Brava Complex is a stratiform mafic-ultramafic body originated from the fractional crystallization of a olivine-tholeitic magma. Field relationships indicate that the parental magma intruded rocks of the palmeirópolis volcano-sedimentary sequence, which has been previously deformed and metamorphosed. The original igneous stratigraphic sequence can be reconstructed as follows: microgabbros, peridotites, websterites and gabros (from the bottom to the top). Geochemical and petrologic data indicate that the magmatic crystallization occurred at pressures below 7 Kbar. Taking into account the phase reequilibrations, the deformation pattern and the isotopic data, the evolution of the Complex can be interpreted as follows: a) separation of magma from the mantle and sub-lithosferic or sub-crustal settling between 2.25 and 2.62 Ga; b) emplacement into the Palmeirópolis Sequence and subsequent final crystallization in at about 2.0 Ga . The available data indicate that the intrusion occurred in a extensional environment related to a crustal rifting; c) main metamorphic episode and deformation, during compressive tectonism at about 1.3 Ga ; d) subsequent metamorphic recrystallizations at lower temperatures during the Brasiliano cycle. The metamorphic events affected the original igneous stratigraphic sequence, which is actually made up by: amphibolytes, serpentinites, metawebsterites and metagabbros (from bottom to top).
 
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Publishing Date
2013-10-14
 
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