Dissertação

Petrografia e geoquímica do Granito Pojuca, Serra dos Carajás-PA

The Pojuca Granite outcrops in the northern portion of the Serra dos Carajás, showing intrusive contact with the Archean rocks of the Itacaiúnas Supergroup. The petrographic studies, based on drilling cores, revealed that in the studied portion (sub-outcrop) the body is constituted by monzogranites...

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Autor principal: HORBE, Marco Antonio
Grau: Dissertação
Idioma: por
Publicado em: Universidade Federal do Pará 2023
Assuntos:
Petrografia
Geoquímica
Granito Pojuca
Serra dos Carajás-PA
CNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA
PETROLOGIA E EVOLUÇÃO CRUSTAL
GEOQUÍMICA E PETROLOGIA
Acesso em linha: http://repositorio.ufpa.br:8080/jspui/handle/2011/15277
id ir-2011-15277
recordtype dspace
spelling ir-2011-152772023-02-08T11:52:29Z Petrografia e geoquímica do Granito Pojuca, Serra dos Carajás-PA HORBE, Marco Antonio DALL'AGNOL, Roberto http://lattes.cnpq.br/2158196443144675 Petrografia Geoquímica Granito Pojuca Serra dos Carajás-PA CNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA PETROLOGIA E EVOLUÇÃO CRUSTAL GEOQUÍMICA E PETROLOGIA The Pojuca Granite outcrops in the northern portion of the Serra dos Carajás, showing intrusive contact with the Archean rocks of the Itacaiúnas Supergroup. The petrographic studies, based on drilling cores, revealed that in the studied portion (sub-outcrop) the body is constituted by monzogranites (MzG), dominant, with variations for monzo and syenogranitic (MzSG) transitional terms, occurring subordinately amphibole-granitoids, alkali -feldspar-granites, pegmatoid rocks and hydrothermalized leucogranites. The rocks are, in general, isotropic, equigranular medium to coarse, pink, very poor in mafics (chlorite±amphibole±tourmaline <7%), constituting leucocratic to hololeucocratic varieties, with very localized brittle deformation. The monzogranites and the monzo to syenogranites are very similar petrographically, however they present different geochemical behavior, marked by the enrichment in K2O and depletion in Na2O in the rocks of facies of the MzSG in relation to the MzG. The amphibole-granitoids show petrographic and chemical characteristics that indicate a hybrid origin, while the alkali-feldspar-granites are related to hydrothermalized portions and occur very locally. The leucogranites (LG) are restricted to the southeast end of the granite and have a well differentiated mineralogical, petrographic and geochemical behavior in relation to the other studied facies. They represent the granite dome, in sharp lower contact with MzG and MzSG, with evidence of being precocious in relation to the other facies, having been fragmented during their placement. LG are medium and fine-grained rocks, pink to cream in color, locally gray or greenish, hololeucocratic (M<2%), being hydrothermalized to varying degrees. Petrographically, two subfacies are distinguished, individualized based on the intensity of the transformations: leucogranites (LG) and intensely hydrothermalized leucogranites (LGIH). Despite the difficulties in distinguishing between primary (magmatic) albite and decalcified plagioclase, which also have an albitic composition, it was concluded, based on petrographic and geochemical evidence, that leucogranites are effectively albite-granites, assuming the hypothesis of their magmatic origin. From the remarkable coincidence of ages between the Pojuca Granite and several anorogenic granites from the Eastern Amazon and the other existing similarities between them, the Pojuca Granite was compared with the Jamon, Musa, Cigano and Serra dos Carajás granites. In terms of modal composition it does not differ from the other granites, however the leucogranites (albite-granites) present in the Pojuca Granite represent a particular variety, which was not registered in the other bodies. The Pojuca Granite exhibits intraplate type A geochemical characteristics and similarities with several anorogenic granites from the Eastern Amazon. Among those chosen for comparison, their greater affinity with the Serra dos Carajás and Cigano granites and the existence of clear differences in relation to the Jamon and Musa granites are clear. Therefore, the existence of geochemical contrasts between the anorogenic granites of the Rio Maria Granite-Greenstone Terrain (TGGRM) and those of the Carajás Block (Pojuca, Serra dos Carajás and Cigano) are confirmed. The albite-granite identified in the Pojuca Granite differs in mineralogical, petrographic and geochemical terms from the other albite-granites described in the Amazon, but this comparison should be deepened in view of the economic and petrological importance that these rocks have. CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico O Granito Pojuca aflora na porção norte da Serra dos Carajás, mostrando contato intrusivo com as rocha arqueanas do Supergrupo Itacaiúnas. Os estudos petrográficos, a partir de testemunhos de sondagens, revelaram que na porção estudada (subaflorante) o corpo é constituído por monzogranitos (MzG), dominantes, com variações para termos transicionais monzo e sienograníticos (MzSG), ocorrendo subordinadamente anfibólio-granitóides, álcali-feldspato-granitos, rochas pegmatóides e leucogranitos hidrotermalizados. As rochas são, no geral, isótropas, equigranulares médias a grossas, rosadas, muito pobres em máficos (clorita±anfibólio±turmalina <7%), constituindo variedades leucocráticas a hololeucocráticas, com deformação rúptil muito localizada. Os monzogranitos e os monzo a sienogranitos são muito similares petrograficamente, porém apresentam diferente comportamento geoquímico, marcado pelo enriquecimento em K2O e empobrecimento em Na2O nas rochas de fácies dos MzSG em relação aos MzG. Os anfibólio-granitóides evidenciam características petrográficas e químicas que indicam uma origem híbrida, enquanto que os álcali-feldspato-granitos se relacionam a porções hidrotermalizadas e ocorrem muito localmente. Os leucogranitos (LG) estão restritos à extremidade sudeste do granito e têm comportamento mineralógico, petrográfico e geoquímico bem diferenciado em relação às demais fácies estudadas. Representam a cúpula do granito, em contato inferior brusco com MzG e MzSG, com evidências de serem precoces em relação às outras fácies, tendo sido fragmentados durante a colocação das mesmas. Os LG são rochas de granulação média e fina, de cor rosa a creme, localmente cinza ou esverdeada, hololeucocráticas (M<2%), sendo hidrotermalizadas em variados graus. Petrograficamente distinguem-se duas subfácies, individualizadas a partir da intensidade das transformações: leucogranitos (LG) e Leucogranitos intensamente hidrotermalizados (LGIH). Apesar das dificuldades na distinção entre albita primária (magmática) e o plagioclásio descalcificado, que também têm composição albítica, concluiu-se, com base nas evidências petrográficas e geoquímicas, que os leucogranitos são efetivamente albita-granitos, assumindo-se a hipótese de sua origem magmática. A partir da notável coincidência de idades entre o Granito Pojuca e diversos granitos anorogênicos da Amazônia Oriental e as demais semelhanças existentes entre eles, comparou-se o Granito Pojuca com os granitos Jamon, Musa, Cigano e Serra dos Carajás. Em termos de composição modal ele não difere dos demais granitos, entretanto os leucogranitos (albita-granitos) presentes no Granito Pojuca representam uma variedade particular, que não foi registrada nos demais corpos. O Granito Pojuca exibe características geoquímicas do tipo A, intraplaca, e semelhanças com diversos granitos anorogênicos da Amazônia Oriental. Dentre os escolhidos para comparação é nítida sua maior afinidade com os granitos Serra dos Carajás e Cigano e a existência de diferenças claras em relação aos granitos Jamon e Musa. Confirma-se, portanto, a existência de contrastes geoquímicos entre os granitos anorogênicos do Terreno Granito-Greenstone de Rio Maria (TGGRM) e aqueles do Bloco Carajás (Pojuca, Serra dos Carajás e Cigano). O albita-granito identificado no Granito Pojuca difere em termos mineralógicos, petrográficos e geoquímicos dos demais albita-granitos descritos na Amazônia, porém essa comparação deverá ser aprofundada tendo em vista a importância econômica e petrológica que essas rochas possuem. 2023-02-08T11:52:01Z 2023-02-08T11:52:01Z 1998-06-14 Dissertação HORBE, Marco Antonio. Petrografia e geoquímica do Granito Pojuca, Serra dos Carajás-PA. Orientador: Roberto Dall"Agnol. 1998. 160 f. Dissertação (Mestrado em Geoquímica e Petrologia) - Curso de Pós-Graduação em Geologia e Geoquímica, Centro de Geociências, Universidade Federal do Pará, Belém, 1998. Disponível em: http://repositorio.ufpa.br:8080/jspui/handle/2011/15277. Acesso em:. http://repositorio.ufpa.br:8080/jspui/handle/2011/15277 por Acesso Aberto Attribution-NonCommercial-NoDerivs 3.0 Brazil http://creativecommons.org/licenses/by-nc-nd/3.0/br/ application/pdf Universidade Federal do Pará Brasil Instituto de Geociências UFPA Programa de Pós-Graduação em Geologia e Geoquímica 1 CD-ROM
institution Repositório Institucional - Universidade Federal do Pará
collection RI-UFPA
language por
topic Petrografia
Geoquímica
Granito Pojuca
Serra dos Carajás-PA
CNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA
PETROLOGIA E EVOLUÇÃO CRUSTAL
GEOQUÍMICA E PETROLOGIA
spellingShingle Petrografia
Geoquímica
Granito Pojuca
Serra dos Carajás-PA
CNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA
PETROLOGIA E EVOLUÇÃO CRUSTAL
GEOQUÍMICA E PETROLOGIA
HORBE, Marco Antonio
Petrografia e geoquímica do Granito Pojuca, Serra dos Carajás-PA
topic_facet Petrografia
Geoquímica
Granito Pojuca
Serra dos Carajás-PA
CNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA
PETROLOGIA E EVOLUÇÃO CRUSTAL
GEOQUÍMICA E PETROLOGIA
description The Pojuca Granite outcrops in the northern portion of the Serra dos Carajás, showing intrusive contact with the Archean rocks of the Itacaiúnas Supergroup. The petrographic studies, based on drilling cores, revealed that in the studied portion (sub-outcrop) the body is constituted by monzogranites (MzG), dominant, with variations for monzo and syenogranitic (MzSG) transitional terms, occurring subordinately amphibole-granitoids, alkali -feldspar-granites, pegmatoid rocks and hydrothermalized leucogranites. The rocks are, in general, isotropic, equigranular medium to coarse, pink, very poor in mafics (chlorite±amphibole±tourmaline <7%), constituting leucocratic to hololeucocratic varieties, with very localized brittle deformation. The monzogranites and the monzo to syenogranites are very similar petrographically, however they present different geochemical behavior, marked by the enrichment in K2O and depletion in Na2O in the rocks of facies of the MzSG in relation to the MzG. The amphibole-granitoids show petrographic and chemical characteristics that indicate a hybrid origin, while the alkali-feldspar-granites are related to hydrothermalized portions and occur very locally. The leucogranites (LG) are restricted to the southeast end of the granite and have a well differentiated mineralogical, petrographic and geochemical behavior in relation to the other studied facies. They represent the granite dome, in sharp lower contact with MzG and MzSG, with evidence of being precocious in relation to the other facies, having been fragmented during their placement. LG are medium and fine-grained rocks, pink to cream in color, locally gray or greenish, hololeucocratic (M<2%), being hydrothermalized to varying degrees. Petrographically, two subfacies are distinguished, individualized based on the intensity of the transformations: leucogranites (LG) and intensely hydrothermalized leucogranites (LGIH). Despite the difficulties in distinguishing between primary (magmatic) albite and decalcified plagioclase, which also have an albitic composition, it was concluded, based on petrographic and geochemical evidence, that leucogranites are effectively albite-granites, assuming the hypothesis of their magmatic origin. From the remarkable coincidence of ages between the Pojuca Granite and several anorogenic granites from the Eastern Amazon and the other existing similarities between them, the Pojuca Granite was compared with the Jamon, Musa, Cigano and Serra dos Carajás granites. In terms of modal composition it does not differ from the other granites, however the leucogranites (albite-granites) present in the Pojuca Granite represent a particular variety, which was not registered in the other bodies. The Pojuca Granite exhibits intraplate type A geochemical characteristics and similarities with several anorogenic granites from the Eastern Amazon. Among those chosen for comparison, their greater affinity with the Serra dos Carajás and Cigano granites and the existence of clear differences in relation to the Jamon and Musa granites are clear. Therefore, the existence of geochemical contrasts between the anorogenic granites of the Rio Maria Granite-Greenstone Terrain (TGGRM) and those of the Carajás Block (Pojuca, Serra dos Carajás and Cigano) are confirmed. The albite-granite identified in the Pojuca Granite differs in mineralogical, petrographic and geochemical terms from the other albite-granites described in the Amazon, but this comparison should be deepened in view of the economic and petrological importance that these rocks have.
author_additional DALL'AGNOL, Roberto
author_additionalStr DALL'AGNOL, Roberto
format Dissertação
author HORBE, Marco Antonio
title Petrografia e geoquímica do Granito Pojuca, Serra dos Carajás-PA
title_short Petrografia e geoquímica do Granito Pojuca, Serra dos Carajás-PA
title_full Petrografia e geoquímica do Granito Pojuca, Serra dos Carajás-PA
title_fullStr Petrografia e geoquímica do Granito Pojuca, Serra dos Carajás-PA
title_full_unstemmed Petrografia e geoquímica do Granito Pojuca, Serra dos Carajás-PA
title_sort petrografia e geoquímica do granito pojuca, serra dos carajás-pa
publisher Universidade Federal do Pará
publishDate 2023
url http://repositorio.ufpa.br:8080/jspui/handle/2011/15277
_version_ 1787148536304893952
score 11.675608

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