Química mineral e condições de cristalização do Plúton Granítico Barcelona, extremo nordeste da Província Borborema, Nordeste do Brasil

Cavalcante, Rogério; Galindo, Antonio Carlos; Silva, Fernando C. Alves Da; Souza, Raquel Franco de

doi:10.22456/1807-9806.78102

Cited by 6 publications

(6 citation statements)

References 25 publications

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“…The anhedral to subhedral titanite II is related to the sphenitization process. This titanite probably has a late‐magmatic origin, being the result of opaque alteration by the action of deuteric fluids (Cavalcante, Galindo, Alves da Silva, & Souza, 2018; Galindo, Silva, & Souza, 2012). According to Dall'agnol, Scaillet, and Pichavant (1999) titanite can be formed by two processes: associated with peritectic reactions involving pyroxene hydration and its replacement by hornblende during the magmatic or subsolidus stage; and oxidation during post‐magmatic re‐equilibrium in calc‐alkaline rocks, initially following a cooling trend under reduced conditions with ilmenite/magnetite formation.…”

Section: Discussionmentioning

confidence: 99%

Contribution to the understanding of the Pinheiro Machado Complex (Dom Feliciano Belt, Brazil): A study of textures, mineral chemistry, and crystallization conditions

et al. 2020

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This article presents textures, mineral chemistry, and geothermobarometric data for the southeastern Pinheiro Machado Complex rocks (PMC), eastern domain of the Dom Feliciano Belt, Rio Grande do Sul, Brazil. The PMC is composed by comagmatic intrusions of quartz diorite, tonalite, and granodiorite with medium‐ to fine‐grained equigranular and medium‐grained inequigranular textures with subordinate alkali‐feldspar macrocrystals. Partial melting features are observed in the comagmatic as melt pools and melt films. Amphibolite xenoliths also occur, presenting sharp‐angled to rounded contacts with the intrusions and evidences of partial assimilation, marked by mafic schlierens. Electron probe microanalyzer punctual analyses were used to classify amphibole, plagioclase, biotite, epidote, and titanite, as well as for the calculations of the crystallization P–T conditions. Amphiboles consist of pargasite for the comagmatic intrusions, and Mg‐hornblende for the amphibolite. Plagioclase ranges from oligoclase to andesine (An15‐40) in both units. Biotite corresponds to annite, with Fe/(Fe + Mg) > 0.3. The epidote has mostly magmatic characteristics in the comagmatic intrusions, with pistacite content 25–30%. Titanite has two distinct textures, titanite I is well formed, subhedral to euhedral, with up to 3 mm; while titanite II is anhedral with size >1 mm and rounded shapes, being both chemically homogeneous. The estimated P–T conditions for the amphibolite crystallization, using plagioclase‐hornblende geothermometer are 650–850°C and 3.62–4.95 kbar, whereas the conditions from the comagmatic intrusions are 714–871°C and 4.44–6.10 kbar. In the mineral phases there is a prevalence in the recrystallization field between subgrain rotation (SGR) and grain boundary migration (GBM) in submagmatic flow. These new data indicate that possibly at the end of PMC crystallization, late magmatic fluids caused re‐equilibrium of mineral phases, mainly in biotite and feldspars. Finally, we suggest that the PMC is the result of continuous and repeated comagmatic intrusions in a continental magmatic arc setting at a depth of 20–30 km in an amphibolitic continental crust.

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Section: Discussionmentioning

confidence: 99%

Contribution to the understanding of the Pinheiro Machado Complex (Dom Feliciano Belt, Brazil): A study of textures, mineral chemistry, and crystallization conditions

et al. 2020

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“…According to Dickson and Scott (1997), the average Th content in the upper crust is 12 ppm; usually, mafic and felsic rocks have contents below and above this value, respectively. However, in the Borborema Province, correlations of gammaray spectrometric data (e.g., Cavalcante et al 2016;Uchôa Filho et al 2019;Gomes et al 2021;Costa et al 2023) with geology reveal that granitic rocks of the Brasiliano/Pan-African Orogeny usually do not show relative enrichment of eTh, although in many of these bodies, potassium and uranium are high and the thorium as well (see the whitish areas in Figure 2).…”

Section: Causes Of Th Enrichment In the Archean Unitsmentioning

confidence: 99%

“…In metamorphic rocks, the eTh content can vary greatly. In addition, it was observed that the eTh content is depleted compared to the eU content in most Neoproterozoic metasedimentary units of the Borborema Province (e.g., Cavalcante et al 2016;Uchôa Filho et al 2019;Gomes et al 2021;Costa et al 2023). However, the eTh content is enriched in the Paleoproterozoic gneissmigmatite complexes that compose the basement of the metasedimentary units, for instance, in the Alto Moxotó terrane (Lira Santos et al 2023) and the Rio Piranhas-Seridó domain (Costa et al 2023).…”

Section: Causes Of Th Enrichment In the Archean Unitsmentioning

confidence: 99%

Gamma-ray spectrometry, magnetic and gravity signatures of Archean nuclei of the Borborema Province, Northeastern Brazil

Oliveira,

Domingos,

Medeiros

et al. 2024

JGSB

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Gamma-ray spectrometry, as well as magnetic and gravity data, are used to investigate the geophysical signatures of the Archean nuclei of the Borborema Province. Natural radioactivity, magnetic anomalies, and residual Bouguer gravity anomalies of the Archean nuclei exhibit distinct signatures in relation to adjacent Proterozoic domains. Gamma-ray spectrometry data reveal eTh enrichment in relation to K and eU contents in Archean units. Assuming that K and U were the dominant isotopes, this relative enrichment of eTh can be explained by the fact that Th radioisotopes have a longer half-life than the other two radionuclides and that 4.56 Ga has elapsed since Earth's formation. The intensity of the total magnetic gradient in Archean units is greater than in Proterozoic units in most nuclei. The Archean units underwent deformation and metamorphism in the Brasiliano/Pan-African Orogeny; therefore, the magnetic characteristics now observed in Archean mafic-ultramafic rocks, iron formations and gneissmigmatite complexes are the joint result of their primary properties and the superposed effects of the orogeny. All Archean nuclei of the Borborema Province show positive residual Bouguer gravity anomalies. This could be due to the conservation of the main petrophysical properties of the Archean lithosphere, and their preservation during the intense granitization that occurred in the Brasiliano/Pan-African Orogeny. As magnetic and gravity methods provide information from depth, it is possible to infer the continuity of some Archean nuclei beyond the limits established by surface geological data. Based on these results, it will be possible to use geophysical signatures to investigate the possible existence of unknown Archean units in the province.

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“…Os dados de ETR analisados fazem parte de uma compilação iniciada por Nascimento et al (2015) e alimentada com dados de trabalhos posteriores (e.g. Cavalcante, 2015; Tabela 1. Sumarização dos corpos estudados das suítes Shoshonítica e Calcioalcalina de alto K Porfirítica e seus respectivos trabalhos de referência e fonte dos dados utilizados.…”

Section: Materiais E Métodosunclassified

Padrões de distribuição de elementos terras-raras nas suítes plutônicas Ediacaranas a Cambrianas no extremo nordeste da Província Borborema, Brasil

Pinheiro,

Lucas,

Nascimento

et al. 2023

Geol. USP. Sér. Cient.

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O magmatismo Ediacarano a Cambriano no extremo NE da Província Borborema é representado por seis suítes plutônicas definidas com base em critérios químicos, petrográficos e texturais, sendo estas as suítes Shoshonítica, Calcioalcalina de alto K Porfirítica, Calcioalcalina de alto K Equigranular, Calcioalcalina, Alcalina e Alcalina Charnockítica. Este trabalho apresenta e discute os padrões de variação de elementos terras-raras (ETR) para essas suítes, utilizando a abordagem do método de lambda (λ) para obtenção dos coeficientes de forma (i.e. λ0, λ1, λ2, λ3) para os padrões de ETR. Os valores médios obtidos para tais coeficientes (notação λ0/λ1/λ2/λ3) são: suítes Shoshonítica (5,36/8,68/108,65/-1.438,32), Calcioalcalina de alto K Porfirítica (5,34/11,83/141,35/-1.464,81), Calcioalcalina de alto K Equigranular (5,43/9,29/152,15/-1.486,88), Calcioalcalina (4,77/5,44/149,65/-1.383,71), Alcalina (3,85/3,49/174,37/-1.282,47), AlcalinaFlores (5,63/4,12/152,31/-1.166,31) e Alcalina Charnockítica (5,60/9,98/128,10/-1.638,25). Os resultados apontam para forte influência no fracionamento de feldspatos nos padrões ETR observados, principalmente no que diz respeito às anomalias de Eu observadas utilizando λ0 como um marcador de fracionamento. Outros minerais como granada, clino e ortopiroxênio podem apresentar localmente influência sobre os baixos valores de λ1 e altos valores de λ3, enquanto os minerais que particionam álcalis influenciam valores altos de λ2.

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Química mineral e condições de cristalização do Plúton Granítico Barcelona, extremo nordeste da Província Borborema, Nordeste do Brasil

Cited by 6 publications

References 25 publications

Contribution to the understanding of the Pinheiro Machado Complex (Dom Feliciano Belt, Brazil): A study of textures, mineral chemistry, and crystallization conditions

Contribution to the understanding of the Pinheiro Machado Complex (Dom Feliciano Belt, Brazil): A study of textures, mineral chemistry, and crystallization conditions

Gamma-ray spectrometry, magnetic and gravity signatures of Archean nuclei of the Borborema Province, Northeastern Brazil

Padrões de distribuição de elementos terras-raras nas suítes plutônicas Ediacaranas a Cambrianas no extremo nordeste da Província Borborema, Brasil

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