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au:SOMMER, CARLOS AUGUSTO

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Occurrence of dravitic tourmaline in a diamond-bearing breccia: a possible lamproite deposit in the Alto Paranaíba Igneous Province
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Vieira, Ana Carolina Batista

; Almeida-Abreu, Pedro Angelo

; Batillani, Gislaine Ámores

; Sommer, Carlos Augusto

Brazilian Journal of Geology

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2022, Volume 52 N. 3 elocation e20200063

Abstract: En | Text: En | PDF: En

Abstract The mineral chemistry of diamond indicator minerals is used to trace mineralizations in primary rocks such as lamproites/kimberlites and in secondary deposits. Subcalcic garnets and magnesian ilmenites are both minerals associated with the diamond potential described in many deposits in the Alto Paranaíba Igneous Province where several kimberlitic pipes and alluvial deposits occur. Our study was conducted on the Romaria diamond deposit of (Brazil), where garnet, ilmenite and tourmaline grains were recovered from a diamon-bearing breccia were analyzed under electron microprobe. The garnet composition is compatible with G10, G9 and G5 types. Ilmenite grains are Mg- to Mn-rich. Nearly 80% of the tourmaline grains are dravite-type. This association of dravite tourmaline with diamond in rocks of lamproitic affinity may be common, as evidenced in the Argyle, Ellendale, Prairie Creek, Sask, Presidente Olegário and Ymi-1 pipes. We therefore suggest a possible lamproite origin for the studied diamond deposit.

https://doi.org/10.1590/2317-4889202220200063

Geophysical characterization and modeling of a Neoproterozoic intrusive volcaniclastic lamprophyre in southernmost Brazil
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Baesso, Anderson

; Sommer, Carlos Augusto

; Savian, Jairo Francisco

; Gambeta, Johnathan Henrique

; Aquino, Robson dos Santos

Brazilian Journal of Geology

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2022, Volume 52 N. 3 elocation e20210051

Abstract: En | Text: En | PDF: En

Abstract Neoproterozoic spessartitic lamprophyres are linked to the Lavras do Sul Shoshonitic Association in the Sul-Riograndense Shield, southernmost Brazil. Bodies of intrusive spessartitic lamprophyres occur in trachyandesites of this association in the Cerro Tupanci region. There, Neoproterozoic igneous and metamorphic complexes are covered by volcanic-sedimentary Ediacaran sequences of the Camaquã Basin that include trachyandesites, conglomerates, sandstones, and spessartitic lamprophyre dikes of which a spessartitic lapilli tuff N-NE oriented is the main occurrence. Gamma spectrometric and gravimetric data for the lapilli tuff allowed definition of its occurrence as a dike elongated N-S, bearing low values for gamma spectrometry and a strong negative gravimetric anomaly approximately 450 m long and 70 m wide. Two-dimensional modeling of this anomaly suggests that the dike is subvertical to vertical. Magnetometry did not provide significant data regarding the lamprophyre but did show a normal dipolar anomaly to the west, suggesting the presence of a non-outcropping cylindrical intrusion in the area.

https://doi.org/10.1590/2317-4889202220210051

The 1.88 Ga Uatumã Magmatism in the Serra dos Magalhães region: petrology and implications to the extension of the south-eastern edge of the Amazonian Craton
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Lima, Ianna Ferreira de

; Pierosan, Ronaldo

; Barros, Márcia Aparecida de Sant'Ana

; Rubert, Rogério Roque

; Sommer, Carlos Augusto

; Okuno, Diogo Isamu de Almeida

Brazilian Journal of Geology

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2021, Volume 51 N. 1 elocation e20200046

Abstract: En | Text: En | PDF: En

Abstract The Amazonian Craton (AC) is a Pre-Cambrian tectonic segment that extends over 4.3 × 105 km2 at the northern portion of the South American Platform. Phanerozoic sedimentary basins cover most of the edges of the AC and sparse occurrences of Precambrian rocks may aid the definition of its extension. One of these occurrences is the volcano-plutonic rocks that outcrop in the Serra dos Magalhães region, which relates to the Uatumã Magmatism, an expressive Orosirian magmatic event that constitutes a Siliceous Large Igneous Province. Effusive rhyodacites and rhyolites comprise the volcanic unit and the plutonic counterpart consists of epizonal monzogranites. Whole-rock geochemistry indicates an A2-type granite affinity to all magmatic rocks. Contrasting signatures suggest a magmatic evolution from a single stratified magma chamber. U-Pb zircon crystallization ages are 1870 ± 11 Ma for the rhyodacites, 1879 ± 5 Ma for the monzogranites, and a slightly younger age of 1863 ± 14 Ma for the rhyolites. Interpretation of satellite and geophysical images allows the recognition of regional lineaments in the Parecis and Bananal basins that suggest the extension of the AC up to the Tucurui Fault in the eastern portion (Bananal Basin) and up to the Brasnorte High in the southern part (Parecis Basin).

https://doi.org/10.1590/2317-4889202120200046 725 downloads

The Mato Perso Conduit System: evidence of silicic magma transport in the southern portion of the Paraná-Etendeka LIP, Brazil
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Simões, Matheus Silva

; Lima, Evandro Fernandes de

; Sommer, Carlos Augusto

; Rossetti, Lucas de Magalhães May

Brazilian Journal of Geology

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jun 2018, Volume 48 N. 2 Pages 263 - 281

Abstract: En | Text: En | PDF: En

ABSTRACT: The Mato Perso Conduit System is described from a ~ 120 km2 area in south Brazil exposing silicic volcanics of the Paraná-Etendeka LIP. A volcanic succession is defined by basaltic flows covered by flat-lying oxidized vitrophyres, banded vitrophyres cutting the lower lavas and grey flat-lying vitrophyres covering all the units. Flow morphologies determined by the recognition of structures, textures, and vesicle distribution were observed. Oxidized vitrophyres display massive flat-lying banded cores and flow tops from vesicular to frothy. Grey flat-lying vitrophyres have sharp contacts in the top of both basalt flows and oxidized vitrophyres, locally exhibit basal breccia and have a flat-lying foliation. Conduits are represented by banded vitrophyres and breccias, which outcrop in a 6 km wide, NW-SE oriented segment downthrown by normal faults towards the Antas River. The interpretation of the units on the geological map scale indicates intrusive contact relations. Recognition of dike-like structures in banded vitrophyres and dykes of oxidized vitrophyre are evidence of felsic magma transport. Based on field observations, we propose the emplacement of subaerial oxidized and grey vitrophyres fed by a fault-related conduit system. Sustained high temperature magmatic systems ensure the silicic lavas have a low viscosity and travel great distances.

https://doi.org/10.1590/2317-4889201820170080 1372 downloads

Pb isotope geochemistry and reappraisal of Sr-Nd isotopes of the Cerro Morado basic magmatism (Ischigualasto-Villa Union Triassic basin, NW Argentina): Implications for the mantle sources
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Sommer, Carlos Augusto

; Barreto, Carla Joana S.

; Lafon, Jean Michel

; Lima, Evandro Fernandes de

; Alexandre, Felipe Marcelo

; Chemale Jr., Farid

; Koester, Edinei

Brazilian Journal of Geology

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jan 2018, Volume 48 N. 1 Pages 115 - 126

Abstract: En | Text: En | PDF: En

ABSTRACT: Sr-Nd-Pb isotopic signatures were determined for silica-undersaturated hypabyssal alkaline basic rocks of the Los Baldecitos Formation in the Cerro Morado area, situated in the Ischigualasto - Vale de la Luna Provincial Park (northernmost San Juan Province, Argentina). The basic rocks show slight variations of the Sr-Nd-Pb isotopes and similar behavior of whole-rock geochemistry, which suggest a single source for the Cerro Morado volcanic rocks. The present-day Pb isotopic data show moderately radiogenic Pb compositions (206Pb/204Pb = 18.31 - 18.35), in addition to low values of 87Sr/86Sr initial ratios of 0.70314 - 0.70386 and highly radiogenic Nd initial isotopic compositions (+7.1 < εNd (228 Ma) < +9.3), which point to a PREMA mantle reservoir signature for the alkaline basalts with little evidence of crustal contamination. The involvement of a HIMU component in the source, previously suggested for the Cerro Morado volcanics, should be disregarded in the light of the Pb isotopic signature. The Sr-Nd signature together with Nd-TDM model ages not older than 295 Ma does not support the involvement of an ancient crust.

https://doi.org/10.1590/2317-4889201820170106 1457 downloads

Zircon U-Pb geochronology, Sm-Nd and Pb-Pb isotope systematics of Ediacaran post-collisional high-silica Acampamento Velho volcanism at the Tupanci area, NW of the Sul-Rio-Grandense Shield, Brazil
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Sommer, Carlos Augusto

; Leitzke, Felipe Padilha

; Lima, Evandro Fernandes de

; Barreto, Carla Joana Santos

; Lafon, Jean Michel

; Matté, Vinicius

; Philipp, Ruy Paulo

; Conceição, Rommulo Vieira

; Basei, Miguel Ângelo Stipp

Brazilian Journal of Geology

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dec 2017, Volume 47 N. 4 Pages 545 - 560

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

RESUMO: Novas idades obtidas por meio do método U-Pb em zircão e dados isotópicos Sm-Nd-Pb são apresentados para as rochas vulcânicas e hipabssais ácidas da exposição mais setentrional da Formação Acampamento Velho na porção NW do Escudo Sul-Rio-Grandense, Brasil. O primeiro episódio vulcânico, agrupado nos riolitos alto-Ti do Cerro Tupanci, possui idades de 579 ± 5,6 Ma, o que está de acordo com dados da literatura para o vulcanismo pós-colisional da Formação Acampamento Velho na Bacia do Camaquã. Idades de 558 +/- 39 Ma foram obtidas para o grupo de riolitos baixo-Ti no Cerro dos Picados, o que pode indicar um episódio vulcânico mais recente ou um período de tempo maior para o vulcanismo da Formação Acampamento Velho no Sul do Brasil, embora o grau de incerteza nos dados seja alto. Em relação às fontes magmáticas, os dados isotópicos de Sm-Nd acoplados a isótopos de Pb e uma revisão da geoquímica de elementos-traço indicam diferentes graus de fusão de crosta inferior paleoproterozoica (Suíte Dom Feliciano, Pinheiro Machado) a neoproterozoica (Terreno Rio Vacacaí). Os dados apresentados neste estudo, quando analisados em conjunto com dados da literatura, contribuem para a melhor compreensão da evolução estratigráfica das sucessões vulcânicas neoproterozoicas pós-colisionais da Bacia do Camaquã no Escudo Sul-Rio-Grandense.

ABSTRACT: We present new U-Pb zircon ages and Sm-Nd-Pb isotopic data for volcanic and hypabyssal acid rocks from the northernmost exposure of the Acampamento Velho Formation in the NW portion of the Sul-Rio-Grandense Shield, Brazil. The first volcanic episode, grouped in the high-Ti rhyolites from the Tupanci hill, shows age of 579 ± 5.6 Ma, which is in agreement with the post-collisional Acampamento Velho Formation volcanism in the Bom Jardim Group of the Camaquã Basin. A poorly constrained age of 558 +/- 39 Ma was obtained for rhyolites from the low-Ti group at the Picados Hill, which may indicate a younger acid volcanism, or a greater time span for the volcanism of the Acampamento Velho Formation in southernmost Brazil. Regarding magmatic sources, Sm/Nd isotopic data coupled to Pb isotopes and a review of trace element geochemistry indicate different amounts of Paleoproterozoic (Dom Feliciano, Pinheiro Machado Suite) to Neoproterozoic (Rio Vacacaí terrane) lower crust melting. Our data, coupled with literature data, contribute to a better understanding of the stratigraphic evolution for the Neoproterozoic post-collisional volcanic successions of the Camaquã Basin in the Sul-Rio-Grandense Shield.

https://doi.org/10.1590/2317-4889201720170064 1901 downloads

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

; Philipp, Ruy Paulo

; Sommer, Carlos Augusto

Brazilian Journal of Geology

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sep 2017, Volume 47 N. 3 Pages 467 - 489

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

RESUMO: As rochas vulcânicas básicas da região da Palma, porção sul do Terreno São Gabriel, foram interpretadas como se tivessem sido geradas durante o período de subducção ativa da orogenia São Gabriel (Criogeniano). Esse terreno formou-se como resultado do fechamento do Oceano Charrua, entre 900-680 Ma. Os basaltos possuem foliação ígnea sub-horizontal e textura porfirítica, com fenocristais de plagioclásio em matriz fina compostos de plagioclásio, augita e magnetita, a qual é comumente alterada para actinolita, clorita e epidoto. As rochas apresentam amígdalas e venulações refletindo uma fase hidrotermal pervasiva e são afetadas por metamorfismo termal relacionado à intrusão do granito Jaguari. Duas amostras foram datadas pelo método geocronológico U-Pb em zircão e revelaram idades de cristalização de 563±2 Ma e 573±6 Ma. Os basaltos possuem composição transicional toleítica a calcioalcalina, característica metaluminosa, padrão de elementos traços enriquecidos em elementos litófilos de raio iônico grande (LILE) com anomalias negativas de Nb, P e Ti, leve enriquecimento em elementos terras raras pesados (LREE) e padrão horizontal de elementos terras raras leves (HREE). Os dados permitem interpretar os basaltos como pertencentes à Formação Acampamento Velho da Bacia do Camaquã e relacionados aos basaltos dos platôs Ramada e Taquarembó. Essas associações representam a evolução final do vulcanismo gerado no período pós-colisional do Cinturão Dom Feliciano.

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.

https://doi.org/10.1590/2317-4889201720170019 1788 downloads

Calcium Score Use in Isolation in Acute Chest Pain Setting - Is it Sufficient?
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Magalhães, Tiago Augusto

; Bittencourt, Marcio Sommer

; Rochitte, Carlos Eduardo

Arquivos Brasileiros de Cardiologia

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aug 2017, Volume 109 N. 2 Pages 94 - 96

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

https://doi.org/10.5935/abc.20170116 629 downloads

II Diretriz de Ressonância Magnética e Tomografia Computadorizada Cardiovascular da Sociedade Brasileira de Cardiologia e do Colégio Brasileiro de Radiologia
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Sara, Leonardo

; Szarf, Gilberto

; Tachibana, Adriano

; Shiozaki, Afonso Akio

; Villa, Alexandre Volney

; Oliveira, Amarino Carvalho de

; Albuquerque, Andrei Skromov de

; Rochitte, Carlos Eduardo

; Nomura, César Higa

; Azevedo, Clerio Francisco

; Jasinowodolinski, Dany

; Tassi, Eduardo Marinho

; Medeiros, Fabio de Morais

; Kay, Fernando Uliana

; Junqueira, Flávia Pegado

; Azevedo, Guilherme S. A.

; Monte, Guilherme Urpia

; Pinto, Ibraim Masciarelli Francisco

; Gottlieb, Ilan

; Andrade, Joalbo

; Lima, João A. C.

; Parga Filho, José Rodrigues

; Kelendjian, Juliana

; Fernandes, Juliano Lara

; Iquizli, Leonardo

; Correia, Luis C. L.

; Quaglia, Luiz Augusto

; Gonçalves, Luiz Flavio Galvão

; Ávila, Luiz Francisco

; Zapparoli, Marcello

; Hadlich, Marcelo

; Nacif, Marcelo Souto

; Barbosa, Márcia de Melo

; Minami, Márcio Hiroshi

; Bittencourt, Marcio Sommer

; Siqueira, Maria Helena Albernaz

; Silva, Marly Conceição

; Lopes, Marly Maria Uellendahl

; Marques, Mateus Diniz

; Vieira, Mônica La Rocca

; Coellho Filho, Otávio Rizzi

; Schvartzman, Paulo R.

; Santos, Raul D.

; Cury, Ricardo C.

; Loureiro, Ricardo

; Cury, Roberto Caldeira

; Sasdelli Neto, Roberto

; Macedo, Robson

; Cerci, Rodrigo Julio

; Faria Filho, Rui Alberto de

; Cardoso, Sávio

; Naves, Thiago

; Magalhães, Tiago Augusto

; Senra, Tiago

; Burgos, Ursula Maria Moreira Costa

; Moreira, Valéria de Melo

; Ishikawa, Walther Yoshiharu

Arquivos Brasileiros de Cardiologia

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dec 2014, Volume 103 N. 6 Pages 1 - 86

Abstract: Pt | Text: Pt | PDF: Pt

https://doi.org/10.5935/abc.2014S006 67586 downloads

10.

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

; Lima, Evandro Fernandes de

; Pierosan, Ronaldo

; Machado, Adriane

Brazilian Journal of Geology

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jul 2011, Volume 41 N. 3 Pages 420 - 435

Abstract: Pt En | Text: Pt En | PDF: Pt | PDF: En

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 afinidade alcalina sódica. Nos depósitos de fluxo 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. Os cálculos de temperaturas pré-eruptivas obtidas na saturação em zircão mostram valores entre 870-978oC para o Platô do Taquarembó e de 850-946oC para o Platô da Ramada. Os valores de viscosidade calculados variam de 4,77 x 107 a 1,39 x 108 Pa s para os reoignimbritos, e 1,72 x1011 a 6,55 x 1011 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 fluxos. 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 fluxo, o que espessa progressivamente o depósito. Portanto, a elevada soldagem e o reomorfismo são sin-deposicionais. Os fluxos 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.

Abstract: 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 affinity. At the pyroclastic flow 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 870-978oC for Taquarembó Plateau and 850-946oC for Ramada Plateau. The calculated viscosity values vary from 4.77 x 107 to 1.39 x 108 Pa s for the reoignimbrites, and 1.72 x1011 to 6.55 x 1011 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 flows. 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 flow movement, which becomes the deposit progressively thicker. Therefore, the high welding degree and the reomorfism are sin-depositional. The high temperature pyroclastic flows of Ramada and Taquarembó plateaus were generated from low eruption columns and can be interpreted as extracaldera ignimbritic deposits.

https://doi.org/10.25249/0375-7536.2011413420435 549 downloads

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