Reoignimbritos e ignimbritos de alto grau do vulcanismo Acampamento Velho, RS: origem e temperatura de formação

Sommer, Carlos Augusto; Lima, Evandro Fernandes de; Pierosan, Ronaldo; Machado, Alice Beatriz Mombach Pinheiro

doi:10.25249/0375-7536.2011413420435

Cited by 13 publications

(7 citation statements)

References 67 publications

(77 reference statements)

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“…De acordo com Dingwell e Webb (1990) esta temperatura representaria o limite cinético entre um "líquido" (sistema viscoso) e um sólido (elás-tico) em resposta ao esforço mecânico aplicado, sendo que acima da temperatura de transição, as partículas serão viscosamente deformadas permitindo a soldagem, e abaixo da mesma, a soldagem é inibida. Esse tipo de interpretação tem sido discutido nos depósitos dos platôs do Taquarembó e Ramada, Escudo Sul-rio-grandense (Sommer et al, 2011).…”

Section: Discussionunclassified

Vulcanismo félsico paleoproterozoico do Grupo Iricoumé, Domínio Erepecuru-Trombetas, Província Amazônia Central: dados de campo, caracterização petrográfica e geocronologia Pb-Pb em zircão

Barreto

Lafon

Costa

et al. 2013

Geol. USP, Sér. cient.

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Disponível on-line no endereço www.igc.usp.br/geologiausp -47 -Resumo O Grupo Iricoumé compreende rochas vulcânicas efusivas e piroclásticas, com texturas e estruturas bastante preservadas, que pertence a um extenso evento vulcano-plutônico que marcou a região central do Cráton Amazônico durante o Orosiriano. Tais rochas estão expostas no noroeste do estado do Pará, na porção meridional do sudoeste do Domínio Erepecuru-Trombetas, sul do Escudo das Guianas. Estudos petrográficos permitiram distinguir um vulcanismo explosivo, predominante e representado por rochas piroclásticas (ignimbritos, reoignimbritos, tufo coignimbrítico de queda e lápili-tufo relacionado a surge), e um efusivo, subordinado, representado por fluxos de lavas coerentes e rochas hipabissais (andesitos, lamprófiros espessartíticos e latitos). A maioria das rochas piroclásticas exibe feições diagnósticas da deposição dos piroclastos sob altas temperaturas, sugerindo que as rochas vulcânicas estão provavelmente relacionadas a ambientes de geração de caldeiras. As idades Pb-Pb de 1888 ± 2,5 e 1889 ± 2 Ma obtidas em zircão de ignimbritos traquidacíticos confirmam que a maioria das rochas estudadas pertence ao Grupo Iricoumé. Por outro lado, a idade Pb-Pb de 1992 ± 3 Ma obtida em zircão de um andesito evidencia um episódio vulcânico efusivo orosiriano mais antigo, já reconhecido, localmente, mais a sul, no Domínio Tapajós. Os dados obtidos demonstram a ampla extensão do vulcanismo Iricoumé e rochas vulcânicas correlatas na porção central do Cráton Amazônico, e constituem argumentos favoráveis para associar esse episódio vulcânico e rochas magmáticas correlatas a uma silicic large igneous province (SLIP), como já vem sendo descrito por alguns autores.Palavras-chave: Orosiriano; Cráton Amazônico; Grupo Iricoumé; Domínio Erepecuru-Trombetas; Rochas vulcânicas. AbstractThe Iricoumé group consists of very well preserved pyroclastic and effusive volcanic rocks as a part of an extensive volcano-plutonic event, which marked the central part of the Amazonian craton during the Orosirian. Such rocks occur in the southern part of the southwestern of Erepecuru-Trombetas Domain (NW of the Pará state), south of the Guyana Shield. Petrographic study allows distinction of two volcanic types. A dominant explosive volcanism is characterized by pyroclastic rocks (ignimbrites, rheoignimbrites, lapilli-tuff related to surge deposit, and co-ignimbrite fall tuff) while a subordinated effusive volcanism is represented by coherent lavas flows and hypabissal rocks (andesites, lamprophyres and latites). Most of the pyroclastic rocks exhibit features of deposition under high temperature suggesting formation in a caldera-related environment. Pb-Pb zircon ages of 1888 ± 2.5 and 1889 ± 2 Ma have been obtained for the formation of trachydacitic ignimbrites and confirm that the dominant volcanism is part of the Iricoumé group. The Pb-Pb zircon age of 1992 ± 3 Ma

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Section: Discussionunclassified

Vulcanismo félsico paleoproterozoico do Grupo Iricoumé, Domínio Erepecuru-Trombetas, Província Amazônia Central: dados de campo, caracterização petrográfica e geocronologia Pb-Pb em zircão

Barreto

Lafon

Costa

et al. 2013

Geol. USP, Sér. cient.

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“…The Acampamento Velho Formation is the top unit of the Cerro do Bugio Group and represents the record of sodium alkaline affinity volcanism related to a post-orogenic extensional tectonic environment of approximately 700 m thick (Sommer et al, 1999;Janikian et al, 2005). This explosive-effusive volcanism is predominantly acid and formed in a subaerial environment associated with lavas and dikes of basic composition (Sommer et al, 2011;Matté et al, 2012). Outcrops of elongated tabular grayish-brown rhyolites oriented in the NE direction, which were described in the Acampamento Velho Formation (Figure 3f), were frequently observed in the sandstones of the Passo da Promessa Formation, near the Victor Teixeira occurrence (see Figure 2a).…”

Section: Study Area and Geological Settingmentioning

confidence: 99%

Geophysical-Structural Framework in a Mineralized Region of Northwesternmost Camaquã Basin, Southern Brazil

Pereira

2021

GeofInt

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Airborne and ground magnetic and gravimetric maps provide important information about the spatial distribution of causative sources in the geological substrate. These sources normally have different physical and geometric properties and are located at different depths, making it difficult to identify the geological features that correspond to the sources. Filtering and enhancement techniques can be used to highlight features in potential field anomalies (such as center and edges of sources). Also, these techniques remove associated noise, isolate shallow from deep sources, and estimate depths. We applied enhancement and depth estimation techniques in airborne and ground potential field data to delineate a subsurface structural framework of two copper occurrences (Victor Teixeira and Capão Grande) in the northwestern border of Camaquã Basin with the Sul-Riograndense Shield. Our results confirmed previously recognized structures and revealed an interconnected structural framework, which has an estimated depth of 170 m by Euler solutions. This configuration suggests a possible connection between the two mineralization outcrops, which are separated by a distance of 2,300 m.

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“…Geographic distribution and habitat: Calydorea riograndensis is narrowly endemic in central-southeastern Rio Grande do Sul State, Brazil, in the north of the municipality of Dom Pedrito, in the basin of Tacuarembó River, in an extent of occurrence estimated smaller than 1,000 km 2 , and an area of occupancy less than 100 km 2 . The specimens grow on stony grasslands or grasslands with shallow soils to deep, often wet, and with few capacity of drainage, developed on vulcanoclastic rocks of the Tacuarembó geological plateau (see Sommer et al, 2011). This species is sympatric with others Iridaceae, e.g., Cypella pusilla (Link & Otto) Jackson, Cypella herbertii (Herbert) Herbert, Herbertia darwinii Roitman & A. Castillo, Herbertia lahue (Molina) Goldblatt, Herbertia amoena Griseb., Kelissa brasiliensis (Baker) Ravenna and Sysirinchium spp.…”

Section: Calydorea Riograndensismentioning

confidence: 99%

Taxonomy, geographic distribution, conservation and species boundaries in Calydorea azurea group (Iridaceae: Tigridieae)

Deble¹,

Deble

Alves³

et al. 2018

Balduinia

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For this study were performed observations in populations of Calydorea azurea Klatt and allied taxa, along of the ecosystems of the Río de La Plata Grasslands, geographic extent where occur this group. For the complementation of the data were examined collections deposited in the principal herbaria of southern Brazil, Uruguay and Argentina, and were analyzed image of types and others collections available. All studied species were photographed and its populations geo-referenced. It are recognized six species: C. alba Roitman & Castillo, C. azurea, C. charruana Deble, C. luteola (Klatt) Baker, C. minima Roitman & Castillo and C. riograndensis Deble. C. azurea is cited for Brazil, C. charruana is added to Argentinian flora, C. luteola has its taxonomic delimitation established, and its occurrence is extended up to the northern Uruguay. The geographic distribution of C. riograndensis is reestablished, in view of three collections mentioned in the protologue are identified as belonging at others species. All species studied are described, illustrated through of photos, being presented data about geographic distribution, ecology and conservation.

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Reoignimbritos e ignimbritos de alto grau do vulcanismo Acampamento Velho, RS: origem e temperatura de formação

Cited by 13 publications

References 67 publications

Vulcanismo félsico paleoproterozoico do Grupo Iricoumé, Domínio Erepecuru-Trombetas, Província Amazônia Central: dados de campo, caracterização petrográfica e geocronologia Pb-Pb em zircão

Vulcanismo félsico paleoproterozoico do Grupo Iricoumé, Domínio Erepecuru-Trombetas, Província Amazônia Central: dados de campo, caracterização petrográfica e geocronologia Pb-Pb em zircão

Geophysical-Structural Framework in a Mineralized Region of Northwesternmost Camaquã Basin, Southern Brazil

Taxonomy, geographic distribution, conservation and species boundaries in Calydorea azurea group (Iridaceae: Tigridieae)

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