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Master's Dissertation
DOI
https://doi.org/10.11606/D.44.2020.tde-01032021-110432
Document
Author
Full name
Lizeth Hernandez Tasco
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2020
Supervisor
Committee
Moraes, Renato de (President)
Tedeschi, Mahyra Ferreira
Viegas, Luis Gustavo Ferreira
Title in English
Relation between partial melting, granulite metamorphism, crystallization, deformation of leucosome and the influence of these processes in the rheology of the lower continental crust
Keywords in English
Leucosome
Nappe Socorro-Guaxupé
Partial melting
Quartz c-axis fabric
Ti in quartz
Abstract in English
The main objective of this study is to contribute to the understanding of deformation of leucosome and its residue, in diatexites and granulites, using as examples two units of the Nappe Socorro-Guaxupé, the metatexite unit and the basal granulite unit, from the southernmost portion of the Brasília Orogen. The first is dominated by metasedimentary rocks, although has a name of metatexite unit, it is dominated by diatexite at its base, and the second, is composed primarily by felsic granulite. In oriented samples, after textural characterization, the quartz caxis fabric thermomether and cathodoluminescence (CL) images, where Ti in quartz evidences temperature domains, were used to determine the deformation temperature, which was compared with thermobarometry data in the respective residues. In this way, it was established that the crystallization in the basal granulite and metatexite units occurred along the cooling portion of the P-T path, but in some portions, it was deformed and might be related to medium and high temperatures. During the metamorphism of the amphibolite and granulite facies, synanatectic deformation with melt crystallization and late deformation in solid-state occurred. Therefore, when the granulite is in the solid state, the diatexite is still in the dominantly liquid state, causing the granulite to register those higher deformation temperatures that the diatexite cannot register due to its still mostly liquid state.
Title in Portuguese
não disponível
Keywords in Portuguese
Eixo-c de quartzo
Fusão parcial
Leucossoma
Nappe Socorro-Guaxupé
Ti em quartzo
Abstract in Portuguese
O objetivo principal deste estudo é contribuir para o entendimento da deformação do leucossoma e seus resíduos, em diatexitos e granulitos, utilizando como exemplos duas unidades da Nappe Socorro-Guaxupé, a unidade metatexito e a unidade granulíto basal, da porção mais meridional do Orógeno Brasília. A primeira é dominada por rochas metassedimentares, embora tenha o nome de unidade metatexíto, é dominada por diatexito em sua base, e a segunda, é composta principalmente por granulito félsico. Nas amostras orientadas, após a caracterização textural, o termômetro do eixo c de quartzo e imagens de catodoluminescência (CL), em que o Ti no quartzo indica temperatura, foram utilizados para determinar a temperatura de deformação, a qual foi comparada com os dados de termobarometria nos respectivos resíduos. Desta forma, foi estabelecido que a cristalização nas unidades basais de granulito e metatexito ocorreu ao longo da porção de resfriamento da trajetória P-T, mas em algumas porções foi deformada e pode estar relacionada a médias e altas temperaturas. Durante o metamorfismo das fácies anfibolito e granulito, ocorreu deformação sin-anatética com cristalização por fusão e deformação tardia no estado sólido. Portanto, quando o granulito está no estado sólido, o diatexito ainda está no estado dominantemente líquido, fazendo com que o granulito registre aquelas temperaturas de deformação mais altas que os diatexitos não puderam registrar devido ao seu estado ainda dominantemente líquido.
 
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Publishing Date
2021-03-03
 
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