The Acampamento Velho Formation, a Lower Cambrian Bimodal Volcanic Package: Geochemical and Stratigraphic Studies from the Cerro Do Bugio, Perau and Serra De Santa Bárbara (Caçapava Do Sul, Rio Grande Do Sul, RS - Brazil)

Almeida, Delia Del Pilar Montecinos de; Zerfass, Henrique; Basei, Miguel Ângelo Stipp; Petry, Karla; Gomes, Cristiane Heredia

doi:10.1016/s1342-937x(05)70640-7

Cited by 34 publications

(32 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The Acampamento Velho Formation is a bimodal volcanic/plutonic association of sodium alkaline affinity, mainly characterized by effusive deposits of basic lavas at the base (basalts, trachybasalts and basalt-andesites), followed by explosive ignimbrite deposits, volcanic breccias, and tuffs that are covered by acidic lavas (trachytes and rhyolites) at the top (Sommer et al 1999, Almeida et al 2002, Janikian et al 2012, Matté et al 2016. There are four main occurrences of the Acampamento Velho Formation as follow: 1.…”

Section: The Acampamento Velho Formationmentioning

confidence: 99%

Post-collisional basalts of the Acampamento Velho Formation, Camaquã Basin, São Gabriel Terrane, southernmost Brazil

Vedana¹,

Philipp

Sommer

2017

Braz. J. Geol.

View full text Add to dashboard Cite

ABSTRACT:The basic volcanic rocks in the Palma region, southern portion of the São Gabriel Terrane, have always been interpreted as generated during the active subduction period of the São Gabriel orogeny (Cryogenian). This terrane was built as the result of the Charrua Ocean closure between 900-680 Ma. The basalts show a subhorizontal igneous flow foliation and porphyritic texture, with plagioclase phenocrysts in a thin matrix composed of plagioclase, augite and magnetite, commonly altered to actinolite, chlorite and epidote. They have amygdales and veinlets reflecting a pervasive hydrothermal phase and are affected by thermal metamorphism related to Jaguari granite intrusion. Two samples were dated by the U-Pb zircon geochronology and yielded crystallization ages of 563±2 Ma and 573±6 Ma. The basalts have transitional composition from tholeiitic to calc-alkaline, metaluminous character, trace elements patterns rich in large-ion lithophile element (LILE) with negative anomalies of Nb, P and Ti, slight enrichment in light rare-earth elements (LREE) and horizontal pattern of heavy rare earth elements (HREE). The data allow interpreting the basalts as belonging to the Acampamento Velho Formation of the Camaquã Basin, and related to the basalts of the Ramada and Taquarembó plateaus. These associations represent the final evolution of the volcanism generated in the post-collisional period of the Dom Feliciano Belt.

show abstract

Section: The Acampamento Velho Formationmentioning

confidence: 99%

Post-collisional basalts of the Acampamento Velho Formation, Camaquã Basin, São Gabriel Terrane, southernmost Brazil

Vedana¹,

Philipp

Sommer

2017

Braz. J. Geol.

View full text Add to dashboard Cite

show abstract

“…The basal contact of the Acampamento Velho Formation is unconformable with the Maricá and Bom Jardim Groups. According to Almeida et al (2002), in the Cerro do Bugio , Perau and Serra de Santa Bárbara (Fig. 1), the volcanic rocks (basaltic and rhyolitic compositions) upper contact is a disconformity by the alluvial conglomerates, and locally, by deltaic-lacustrine sandstones and mudstones from Santa Fé Formation.…”

Section: Fig 1 Geological Map Showing the Main Camaquã Basin Stratimentioning

confidence: 99%

“…Soliani Jr. (2000 compiled their data and obtained an age of 529 ± 4 Ma and R 0 = 0,706 (Rb-Sr whole rock). Another Rb-Sr dating was performed by Almeida et al (2002), who studied the rhyolitic flows from Cerro do Bugio area and the dykes intruding the Maricá Formation. These authors obtained two whole rock isochrons: 545.1 ± 12.7 Ma (R 0 = 0.709) and 546 ± 12.9 Ma (R 0 = 0.714).…”

Section: Acampamento Velho Formationmentioning

confidence: 99%

“…Paim et al (2000) named the unit as Acampamento Velho Formation (from Cerro do Bugio Allogroup), and this set of volcanic rocks were considered as an unit limited on the top and base by discontinuities, which marked a special period in the evolution of the basin. It has been traditionally considered as exclusively acid in composition, but detailed geological mapping in the Cerro do Bugio, Cerro do Perau and Serra de Santa Bárbara area (West of Caçapava do Sul town) revealed the existence of a basaltic/andesitic unit at the base and a felsic unit at the top (Zerfass & Almeida 1997, Zerfass et al 2000, Almeida et al 2002. This observation leads to the existence of a bimodal alkaline volcanism, mafic at the base and a felsic at the top.…”

Section: Acampamento Velho Formation: Geological Context Petrographymentioning

confidence: 99%

See 1 more Smart Citation

Late to Post-Orogenic Brasiliano-Pan-African Volcano-Sedimentary Basins in the Dom Feliciano Belt, Southernmost Brazil

Almeida¹,

Chemale²,

Machado³

2012

Petrology - New Perspectives and Applications

View full text Add to dashboard Cite

“…A organização estratigráfi ca desta formação tem sido sugerida por Wildner et al (1999), Sommer et al (1999Sommer et al ( , 2005, Almeida et al (2002), sendo as melhores exposições desta unidade localizadas nos municípios gaúchos de Vila Nova do Sul (Platô da Ramada e Cerro Tupanci), Dom Pedrito (Platô do Taquarembó) e Caçapava do Sul (Passo do Salsinho) conforme ilustradas na fi gura 1.…”

Section: O Vulcanismo Da Formação Acampamento Velhounclassified

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

Sommer

Lima

Pierosan

et al. 2011

RBG

View full text Add to dashboard Cite

Resumo A Formação Acampamento Velho é constituída por depósitos vulcânicos neoproterozoicos dominantemente ácidos, emplaçados em condições subaéreas sobre o Escudo Sul-Rio-Grandense. Registros deste vulcanismo são encontrados nos platôs da Ramada e Taquarembó localizados no sudoeste do Estado do Rio Grande do Sul. Este magmatismo varia de metaluminoso a peralcalino e apresenta afi nidade alcalina sódica. Nos depósitos de fl uxo piroclásticos dominam fragmentos juvenis, como púmices, shards e fragmentos vítreos maciços. Estes apresentam um típico elevado grau de soldagem com ignimbritos, com alto grau nas porções de base e intermediárias, e reoignimbritos no topo. 11 a 6,55 x 10 11 Pa s para os ignimbritos. Os conteúdos de Zr crescem em direção ao topo da sequência piroclástica indicando aumento da peralcalinidade, que determinou a redução da viscosidade dos clastos nas porções superiores dos fl uxos. Um modelo agradacional progressivo permite explicar as variações verticais no tamanho e tipos de clastos, e na geoquímica do depósito. Este modelo assume a aglutinação de partículas juvenis quentes durante o deslocamento do fl uxo, o que espessa progressivamente o depósito. Portanto, a elevada soldagem e o reomorfi smo são sin-deposicionais. Os fl uxos piroclásticos de alta temperatura dos platôs da Ramada e Taquarembó foram gerados a partir de baixas colunas de erupção e podem ser interpretados como depósitos ignimbríticos extracaldeira.Palavras-chave: vulcanismo, depósitos ignimbríticos, soldagem, rochas ácidas. Abstract Reoignimbrites and high-grade ignimbrites of Acampamento Velho volcanism, RS: origin and formation temperature.The Acampamento Velho Formation is constituted by neoproterozoic volcanic deposits of dominantly acid composition, which were emplaced under subaerial conditions on Sul-RioGrandense Shield. The volcanism registration have been found at Ramada and Taquarembó plateaus localized at southwest of Rio Grande do Sul State. This magmatism varies from metaluminous to peralkaline and shows alkaline sodic affi nity. At the pyroclastic fl ow deposits dominate juvenile fragments such as pumices, shards and massive vitreous fragments, which show a typical high welding degree with ignimbrites, being high degree at the base and intermediate portions, and reoignimbrites at the top. The pre-eruptive temperature calculations obtained at the saturation of zircon show values between 870-978 o C for Taquarembó Plateau and 850-946 o C for Ramada Plateau. The calculated viscosity values vary from 4.77 x 10 7 to 1.39 x 10 8 Pa s for the reoignimbrites, and 1.72 x10 11 to 6.55 x 10 11 Pa s for the ignimbrites. Zr contents increase to the pyroclastic sequence top, indicating increasing of peralkalinity, which determined the viscosity reduction of clasts at the upper portions of the fl ows. The progressive aggradacional model allows explaining the vertical variations at the clast size and type, and at the geochemistry of the deposit. This model assumes the agglutination of hot juvenile particles during the fl ow mo...

show abstract

The Acampamento Velho Formation, a Lower Cambrian Bimodal Volcanic Package: Geochemical and Stratigraphic Studies from the Cerro Do Bugio, Perau and Serra De Santa Bárbara (Caçapava Do Sul, Rio Grande Do Sul, RS - Brazil)

Cited by 34 publications

References 15 publications

Post-collisional basalts of the Acampamento Velho Formation, Camaquã Basin, São Gabriel Terrane, southernmost Brazil

Post-collisional basalts of the Acampamento Velho Formation, Camaquã Basin, São Gabriel Terrane, southernmost Brazil

Late to Post-Orogenic Brasiliano-Pan-African Volcano-Sedimentary Basins in the Dom Feliciano Belt, Southernmost Brazil

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

Contact Info

Product

Resources

About