Mid amphibolite facies metamorphism of harzburgites in the Neoproterozoic Cerro Mantiqueiras Ophiolite, southernmost Brazil

Hartmann, Léo Afrâneo; Chemale-Júnior, Farid

doi:10.1590/s0001-37652003000100012

Cited by 20 publications

(11 citation statements)

References 30 publications

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“…3a) is a south-dipping harzburgite-amphibolite body tectonically interleaved with metapelite, quartzite and marble and surrounded by TTG gneisses of the Cambaí Complex (Hartmann and Remus 2000;Hartmann et al 2000b;Hartmann and Chemale 2003). An age of about 733 ± 10 Ma has been obtained for an amphibolite of this complex (Leite et al 1998).…”

Section: Tectonic Evolution Of the São Gabriel Blockmentioning

confidence: 99%

Multiple accretion at the eastern margin of the Rio de la Plata craton: the prolonged Brasiliano orogeny in southernmost Brazil

Saalmann

Gerdes

Lahaye

et al. 2010

Int J Earth Sci (Geol Rundsch)

120

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The Neoproterozoic-Eoplalaeozoic Brasiliano orogeny at the eastern margin of the Rio de la Plata craton in southernmost Brazil and Uruguay comprises a complex tectonic history over 300 million years. The southern Brazilian Shield consists of a number of tectono-stratigraphic units and terranes. The São Gabriel block in the west is characterized by c.760-690 Ma supracrustal rocks and calc-alkaline orthogneisses including relics of older, c. 880 Ma old igneous rocks. Both igneous and metasedimentary rocks have positive eNd(t) values and Neoproterozoic TDM model ages; they formed in magmatic arc settings with only minor input of older crustal sources. A trondhjemite from the São Gabriel block intruding dioritc and tonalitic gneisses during the late stages of deformation (D 3 ) yield an U-Pb zircon age (LA-ICP-MS) of 701 ± 10 Ma giving the approximate minimum age of the São Gabriel accretionary event. The Encantadas block further east, containing the supracrustal Porongos belt and the Pelotas batholith, is in contrast characterized by reworking of Neoarchean to Palaeoproterozoic crust. The 789 ± 7 Ma zircon age of a metarhyolite intercalated with the metasedimentary succession of the Porongos belt provides a time marker for the basin formation. Zircons of a sample from tonalitic gneisses, constituting the Palaeoproterozoic basement of the Porongos belt, form a cluster at 2,234 ± 28 Ma, interpreted as the tonalite crystallization age. Zircon rims show ages of 2,100-2,000 Ma interpreted as related to a Palaeoproterozoic metamorphic event. The Porongos basin formed on thinned continental crust in an extensional or transtensional regime between c. 800-700 Ma. The absence of input from Neoproterozoic juvenile sources into the Porongos basin strongly indicates that the Encantadas and São Gabriel blocks were separated terranes that became juxtaposed next to each other during the Brasiliano accretional events. The tectonic evolution comprises two episodes of magmatic arc accretion to the eastern margin of the Rio de la Plata craton, (i) accretion of an intra-oceanic arc at c. 880 Ma (Passinho event) and (ii) accretion of the 760-700 Ma Cambaí/Vila Nova magmatic arc (São Gabriel event). The latter event also includes the collision of the Encantadas block with the Rio de la Plata craton to the west. Collision and crustal thickening was followed by sinistral shear along SW-NE-trending orogenparallel crustal-scale shear zones that can be traced from southern Brazil to Uruguay and have been active between 660 and 590 Ma. Voluminous granitic magmatism in the Pelotas batholith spatially related to shear zones is interpreted as late-to post-orogenic magmatism, possibly assisted by lithospheric delamination. It marks the transition to the post-orogenic molasse stage. Localized deformation by reactivation of preexisting shear zones continued Electronic supplementary material The online version of this article (

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Section: Tectonic Evolution Of the São Gabriel Blockmentioning

confidence: 99%

Multiple accretion at the eastern margin of the Rio de la Plata craton: the prolonged Brasiliano orogeny in southernmost Brazil

Saalmann

Gerdes

Lahaye

et al. 2010

Int J Earth Sci (Geol Rundsch)

120

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“…These new phases usually form narrow alteration rims surrounding the primary Cr spinel core or develop along cracks. Their formation is attributed to low or medium grade metamorphism, up to mid‐amphibolite facies (Thalhammer et al 1990; Barnes 2000; Hartman & Chemale‐Junior 2003). Lee (1999) suggests that Cr spinel alters into Fe–Cr spinel during amphibolite (over 500 °C) and greenschist (300–500 °C) facies metamorphism, whereas alteration to Cr‐magnetite takes place at lower temperatures.…”

Section: Introductionmentioning

confidence: 99%

Mineralogy and magnetism of Fe-Cr spinel series minerals from podiform chromitites and dunites from Tąpadła (Sudetic ophiolite, SW Poland) and their relationship to palaeomagnetic results of the dunites

Kądziałko-Hofmokl

Delura

Bylina

et al. 2008

Geophysical Journal International

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S U M M A R YThis paper presents the mineralogy and magnetic properties of two varieties of chromitite, sampled in the same exposure of a serpentinite massif regarded to be a fragment of the Sudetic ophiolite. The varieties differ mineralogically and magnetically. One of them, labelled TaA and altered to a low degree according to scanning electron microscope (SEM) and microprobe results, comprises an unaltered Al-Cr spinel core, some secondary chromite and less abundant Cr-magnetite. It has a high magnetic susceptibility and natural remanence (NRM), and its dominating magnetic phase is ferrichromite with T b /T c of about 530 • C occurring in grains in the single domain (SD) + pseudo-single domains (PSDs) and superparamagnetic (SP) states. The second variety, labelled TaB, is highly altered and comprises, apart from Al spinel, two kinds of secondary chromites that do not differ much from the primary Al spinel and no Cr-magnetites. This chromitite variety does not reveal one well defined T b /T c , but a series ranging between 200 and 450 • C, their grain sizes correspond to the SD + SP domain states. The same pattern was observed in chromitite TaA after annealing in air at a temperature of 700 • C. Dunites associated with the chromitites contain, apart from magnetite, chromite grains. The majority of specimens reveal magnetic characteristics similar to the TaA-like variety, but in some specimens TaB-like characteristics were also observed. A standard palaeomagnetic study performed earlier on the dunites showed that their NRM has three components-Lower Devonian carried by magnetite, Permian and Tertiary-Recent. The results presented here lead us to conclude that the latter two are carried by ferrichromites similar to those found in the TaA and TaB chromitites.

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“…1C). Cristais reliquiares de olivina e de cromita de metaperidotitos mostraram compo-sições tıṕicas de o iolitos Hartmann & Chemale Jr., 2003). Metaultrama itos serpentinizados, com a assembleia Anto ilita + Forsterita + Enstatita + Diopsıdio, caracterizam o metamor ismo orogenico M 1 de grau medio-alto da seŕie de baixa P/T.…”

Section: Prisma Acrescionário Da Palmaunclassified

“…Foram analisados os dados de idade de proveniencia obtidos por Hartmann et al (2003), Basei et al (2011Basei et al ( , 2020 e Eiesland (2018). Estes dados são apresentados nos histogramas da Figura 3, onde as amostras estão categorizadas de acordo com a divisão de formações apresentada por Basei et al (2011…”

Section: Proveniência Detrítica (Idades E Fontes)unclassified

Crono-correlação entre as Bacias do Camaquã (RS) e do Itajaí (SC): implicações Paleoambientais e Paleogeográfica

Paim¹,

Chemale²,

Lehn³

et al. 2021

Contribuições À Geologia Do Rio Grande Do Sul E De Santa Catarina

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Fotogra ia aeŕea do setor norte da Serra do Segredo, em Caçapava do Sul, RS, onde se destacam a Pedra do Segredo, em primeiro plano, e a Pedra da Abelha, logo à esquerda, geoformas esculpidas sobre conglomerados luviais da Bacia do Camaquã. Ao fundo, alguns cerros formados por rochas metamór icas e o imponente alto de Caçapava, sobre granitoides diversos, rochas que registram diferentes momentos do Ciclo Brasiliano no sul do Brasil. A paisagem faz parte do Geoparque Caçapava Aspirante Unesco e é parcialmente inserida no Parque Natural Municipal da Pedra do Segredo. Imagem obtida por Felipe Guadagnin. Legenda de André Weissheimer de Borba e Felipe Guadagnin.

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Mid amphibolite facies metamorphism of harzburgites in the Neoproterozoic Cerro Mantiqueiras Ophiolite, southernmost Brazil

Cited by 20 publications

References 30 publications

Multiple accretion at the eastern margin of the Rio de la Plata craton: the prolonged Brasiliano orogeny in southernmost Brazil

Multiple accretion at the eastern margin of the Rio de la Plata craton: the prolonged Brasiliano orogeny in southernmost Brazil

Mineralogy and magnetism of Fe-Cr spinel series minerals from podiform chromitites and dunites from Tąpadła (Sudetic ophiolite, SW Poland) and their relationship to palaeomagnetic results of the dunites

Crono-correlação entre as Bacias do Camaquã (RS) e do Itajaí (SC): implicações Paleoambientais e Paleogeográfica

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