Boron-isotopic constraints on the petrogenesis of hematitic phyllite in the southern Serra do Espinhaço, Minas Gerais, Brazil

Cabral, Alexandre Raphael; Wiedenbeck, Michael; Koglin, Nikola; Lehmann, Bernd; Abreu, Francisco Robério de

doi:10.1016/j.lithos.2012.01.011

Cited by 21 publications

(15 citation statements)

References 39 publications

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“…5). The presence of tourmaline in a matrix of fine-grained muscovite can thus be understood as B and K overprint on volcanic protoliths (CABRAL et al, 2012). Therefore, the presence of high amounts of K2O in the hematitic phyllite cannot be linked to potassic lavas, as interpreted by Chaves and Knauer (2020).…”

Section: Figurementioning

confidence: 94%

“…Two aspects that are relevant to the petrogenesis of hematitic phyllite escaped the attention of Chaves and Knauer (2020). First, only three of the seven samples of hematitic phyllite that are reported in Cabral et al (2012) have been considered by Chaves and Knauer (2020) -see their Table 1 and Figures 4 and 5. Those four samples that were overlooked plot within the rhyolite-dacite field of the Nb/Y-vs.-Zr/Ti diagram of Pearce (1996) -see Figure 5b of Cabral et al (2012).…”

Section: Figurementioning

confidence: 99%

“…First, only three of the seven samples of hematitic phyllite that are reported in Cabral et al (2012) have been considered by Chaves and Knauer (2020) -see their Table 1 and Figures 4 and 5. Those four samples that were overlooked plot within the rhyolite-dacite field of the Nb/Y-vs.-Zr/Ti diagram of Pearce (1996) -see Figure 5b of Cabral et al (2012). Taking into account all samples in the data set of Cabral et al (2012), two protoliths for the hematitic phyllite can be distinguished: a basic rock and an acidic rock.…”

Section: Figurementioning

confidence: 99%

“…Those four samples that were overlooked plot within the rhyolite-dacite field of the Nb/Y-vs.-Zr/Ti diagram of Pearce (1996) -see Figure 5b of Cabral et al (2012). Taking into account all samples in the data set of Cabral et al (2012), two protoliths for the hematitic phyllite can be distinguished: a basic rock and an acidic rock. Second, the widespread tourmalinisation in the southern Serra do Espinhaço, which is expressed in the hematitic phyllite as disseminations and pockets (CORRENS, 1932;DERBY, 1879DERBY, , 1899DERBY, , 1900aMORAES;GUIMARÃES, 1931;CA-BRAL et al, 2011).…”

Section: Figurementioning

confidence: 99%

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On the article “Weathered potassic volcanic rocks as protoliths of the hematitic phyllites of the southern Serra do Espinhaço (MinasGerais)”: a discussion

Cabral

Abreu²

2021

Geochim. Bras.

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Chaves and Knauer (2020) have presented three new whole-rock chemical analyses of phyllitic hematite, a unique metamorphic rock of the southern Serra do Espinhaço. Based on their three samples and a selection of other three samples from the literature, Chaves and Knauer have proposed that the geochemical uniqueness of the rock – i.e., high contents of K2O, Al2O3 and Fe2O3, and depletion in SiO2 – would represent a weathered, feldspathoid-rich alkaline basalt. This contribution is a discussion of their new data, the trace-element contents of which are at odds with those of a potassic, mantle-derived volcanic protolith for the hematitic phyllite. Its Nb/Th ratios of ~3 and chondrite-normalised La/Yb ratios of ~9–17, for instance, are typical of the continental crust. We also point out aspects that escaped the attention of Chaves and Knauer (2020), one of which is the ubiquitous occurrence of tourmaline in the hematitic phyllite.

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Section: Figurementioning

confidence: 94%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

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On the article “Weathered potassic volcanic rocks as protoliths of the hematitic phyllites of the southern Serra do Espinhaço (MinasGerais)”: a discussion

Cabral

Abreu²

2021

Geochim. Bras.

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“…Knauer e Schrank, 1994;Dussin e Dussin, 1995;Cabral et al, 2012); • outro Esteniano-Toniano (1,18 -0,91 Ga) como uma bacia intracratônica cujo processo inicial de subsidência ocorreu por implantação de um rifte, atribuído à Formação Sopa-Brumadinho, detentora dos depósitos conglomeráticos portadores de diamantes, localmente com tufos intercalados. A fase flexural da bacia é marcada pelos sedimentos eólicos e marinhos da Formação Galho do Miguel e do Grupo Conselheiro Mata, respectivamente.…”

Section: Contextualização Regionalunclassified

Interação tectônica entre bacias sucessoras no domínio externo do Orógeno Araçuaí: estudo de caso da região de Planalto de Minas, Minas Gerais

Souza

Martins

Madeira

et al. 2017

Geol. USP. Sér. Cient.

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Resumo O Supergrupo Espinhaço Meridional e o Grupo Macaúbas, em Minas Gerais, são as maiores expressões geotectônicas dos ciclos de fragmentação sucessivos que atingiram o paleocontinente São Francisco-Congo desde o Estateriano até o Criogeniano. O mapeamento geológico em escala 1:25.000 da região de Planalto de Minas, localizada no centro-norte do estado, revelou a ocorrência da Formação São João da Chapada (ca. 1.7 Ga, Supergrupo Espinhaço) diretamente sobreposta por uma sequência metavulcano-sedimentar toniana do Grupo Macaúbas (ca. 889 Ma), aqui designada de Formação Planalto de Minas. A integração geológica-geofísica revelou ainda que esta área permaneceu como um alto estrutural do final do Estateriano até o Toniano. A existência do alto estrutural de Planalto de Minas é o reflexo do complexo arranjo estrutural de rifteamentos sobrepostos, com formação e interação de um meio-gráben, ou sistema ramificado de meio-grabens, que exerceram importante controle tectono-estratigráfico na arquitetura -formação e evolução -da bacia Macaúbas.Palavras-chave: Bacias do Tipo Rifte; Alto Estrutural de Planalto de Minas; Meio-gráben; Geofísica; Supergrupo Espinhaço; Grupo Macaúbas. AbstractIn Minas Gerais state, the Southern Espinhaço Supergroup and Macaúbas Group are the major geotectonic expression of the crustal sucessives fragmentation cycles that shaped the São Francisco-Congo paleocontinent between the Statherian and Cryogenian periods. The geological mapping (1:25.000) in Planalto de Minas region (central-northern portion of Minas Gerais) revealed the occurrence of the São João da Chapada Formation (ca. 1.7 Ga, Espinhaço Supergroup) directly superimposed by a Tonian metavolcano-sedimentary sequence, here called Planalto de Minas Formation (Macaúbas Group), dated at ca. 889 Ma. The geological-geophysical data integration revealed that the Planalto de Minas region remained as a structural high, and this is a reflection of the complex structural arrangement of superimposed rifts, with the formation and interaction among one half-graben or branched system of half-grabens, being important for the tectonic-stratigraphy control -on architecture and evolution -of the Macaúbas basin.

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A new model of bauxitization in quartzitic landscapes: A case study from the Southern Espinhaço Range (Brazil)

Campos

Monteiro

Vasconcelos

et al. 2023

Earth Surf Processes Landf

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Lithology plays a fundamental role in rock weathering and erosion, and in landscape evolution. When weathering‐ and erosion‐prone lithologies are protected from erosion by more resilient rock types (e.g., quartzites and banded iron formations) unusual weathering products result. At the Southern Espinhaço Range, Minas Gerais, Brazil, bauxitic weathering profiles are found in a unique geomorphological–lithological–climatic setting. Resistant quartzites acted as a barrier against erosion of interbedded hematite‐phyllite lenses, channelling solution flows and facilitating the formation of deep weathering profiles. The long‐term exposure of the hematite‐phyllites under alternating wet and dry tropical climates favoured widespread bauxitization. Here we investigate the geochemical, mineralogical, geochronological and micromorphological signatures of scaffolded bauxites in order to reconstruct their evolutionary history. Our data suggest that recurrent aluminium and iron mobilization within the profiles were mainly driven by mineral dissolution‐reprecipitation mediated by bioturbation and the influx of vegetation‐derived organic species. (U–Th)/He geochronology of Al‐goethite reveals that bauxitization started at least since the Lower Miocene, with important intensification of weathering in the Upper Miocene and Lower Pleistocene. The adjacent resilient quartzites acted as scaffolds for bauxitization and supported the preservation of more erodible weathering profiles developed over phyllites. Surface waters that could not infiltrate into the impermeable adjacent quartzites preferentially infiltrated into the more weathereable phyllites, enhancing their porosity and permeability, further enhancing weathering. The evolutionary history of Southern Espinhaço Range bauxites suggests a new model of bauxitization in ancient land surfaces evolution underlain by quartzites, where erosion‐prone lithologies are scaffolded by resilient quartzites and survive long‐term weathering with minimum erosion, producing bauxites.

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Boron-isotopic constraints on the petrogenesis of hematitic phyllite in the southern Serra do Espinhaço, Minas Gerais, Brazil

Cited by 21 publications

References 39 publications

On the article “Weathered potassic volcanic rocks as protoliths of the hematitic phyllites of the southern Serra do Espinhaço (MinasGerais)”: a discussion

On the article “Weathered potassic volcanic rocks as protoliths of the hematitic phyllites of the southern Serra do Espinhaço (MinasGerais)”: a discussion

Interação tectônica entre bacias sucessoras no domínio externo do Orógeno Araçuaí: estudo de caso da região de Planalto de Minas, Minas Gerais

A new model of bauxitization in quartzitic landscapes: A case study from the Southern Espinhaço Range (Brazil)

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