Evolução Petrológica Para Uma Sequência De Rochas Metamórficas Regionais Do Tipo Baixa Pressão Na Regiâo De Itinga, Ne De Minas Gerais

Costa, Antônio Gilberto

doi:10.25249/0375-7536.1989440448

Cited by 8 publications

(8 citation statements)

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“…In the Itinga pegmatite field, the host rocks are biotite schists with variable contents of andalusite, cordierite and sillimanite, formed during the regional metamorphism and recrystallized by contact metamorphism. Low pressure metamorphic silicates (andalusite and cordierite) together with the presence of petalite in some pegmatites and quantitative geothermobarometric data indicate a relatively shallow crustal level (6 to 12 km) for the Itinga field (Correia-Neves et al 1986;Costa 1989;Pedrosa-Soares et al 1996). The Itinga pegmatite field belongs to the rare element class, showing a clear affinity with the LCT pegmatite family.…”

Section: Geochemical and Mineralogical Specializations In The Easternmentioning

confidence: 95%

Late Neoproterozoic-Cambrian granitic magmatism in the Araçuaí orogen (Brazil), the Eastern Brazilian Pegmatite Province and related mineral resources

Campos²,

et al. 2011

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The Araçuaí orogen extends from the eastern edge of the São Francisco craton to the Atlantic margin, in southeastern Brazil. Orogenic igneous rocks, formed from c. 630 to c. 480 Ma, cover one third of this huge area, building up the Eastern Brazilian Pegmatite Province and the most important dimension stone province of Brazil. G1 supersuite (630-585 Ma) mainly consists of tonalite to granodiorite, with mafic to dioritic facies and enclaves, representing a continental calc-alkaline magmatic arc. G2 supersuite mostly includes S-type granites formed during the syn-collisional stage (585-560 Ma), from relatively shallow two-mica granites and related gem-rich pegmatites to deep garnet-biotite granites that are the site of yellow dimension stone deposits. The typical G3 rocks (545-525 Ma) are non-foliated garnet-cordierite leucogranites, making up autochthonous patches and veins. At the post-collisional stage (530-480 Ma), G4 and G5 supersuites were generated. The S-type G4 supersuite mostly consists of garnet-bearing two-mica leucogranites that are the source of many pegmatites mined for tourmalines and many other gems, lithium (spodumene) ore and industrial feldspar. G5 supersuite, consisting of high-K-Fe calc-alkaline to alkaline granitic and/or charnockitic to dioritic/noritic intrusions, is the source of aquamarine-topaz-rich pegmatites but mainly of a large dimension stone production.

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Section: Geochemical and Mineralogical Specializations In The Easternmentioning

confidence: 95%

Late Neoproterozoic-Cambrian granitic magmatism in the Araçuaí orogen (Brazil), the Eastern Brazilian Pegmatite Province and related mineral resources

Campos²,

et al. 2011

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“…The low‐pressure assemblage is not restricted to the investigated region. It has been documented over a much broader area (Costa, ; Pedrosa‐Soares et al., ; Richter et al., ) and does not show the expected zoning of a contact aureole around post‐collisional plutons. These facts strongly suggest that the second event recorded in M‐Domain II can be better compared to Buchan‐type metamorphism, as described by Harte and Hudson ().…”

Section: Discussion and Synthesismentioning

confidence: 93%

“…The different crustal levels exposed across the Arac ßua ı orogen in southeastern Brazil (Figure 1) comprise a sequence of metamorphic assemblages associated with both contractional and extensional fabric elements. The occurrence of medium-and low-pressure regional metamorphism in the orogen was first documented by Almeida, Hasui, Rodrigues, and Yakamoto (1978) and later investigated in detail by Costa, Neves, and Mueller (1984), Costa (1989), and Pedrosa-Soares, Leonardos, and Correia-Neves (1984). Nonetheless, only recently have the conditions and ages of the metamorphic events recorded in the region been investigated in detail, mostly in studies carried out in the high grade and anatectic core of the orogen (e.g.…”

Section: Introductionmentioning

confidence: 92%

Metamorphic record of collision and collapse in the Ediacaran‐Cambrian Araçuaí orogen, SE‐Brazil: Insights from P–T pseudosections and monazite dating

Peixoto

Alkmim

Pedrosa-Soares

et al. 2017

Journal Metamorphic Geology

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The Araçuaí orogen is the Brazilian counterpart of the Araçuaí‐West Congo orogenic system (AWCO), a component of the Ediacaran‐Cambrian orogenic network formed during the amalgamation of West Gondwana. The northwestern portion of the Araçuaí orogen is dominated by a succession of metasedimentary rocks made up of Meso‐ to Neoproterozoic rift, passive margin and syn‐orogenic sequences, locally intruded by post‐collisional granites. These sequences are involved in three distinct tectonic units, which from west to east are: the southern Espinhaço fold‐thrust system (SE‐thrust system), the normal‐sense Chapada Acauã shear zone (CASZ) and the Salinas synclinorium. Three deformation phases were documented in the region. The first two phases (D1 and D2) are characterized by contractional structures and represent the collisional development stage of the orogen. The third phase (D3) is extensional and currently viewed as a manifestation of orogenic collapse of the system. The distribution of the metamorphic mineral assemblages in the region characterizes two metamorphic domains. The M‐Domain I on the west, encompassing the SE‐thrust system and the CASZ, is marked by a syn‐collisional (syn‐D1) Barrovian‐type metamorphism with P–T conditions increasing eastwards and reaching ~8.5 kbar at ~650°C between 575 and 565 Ma. The M‐Domain II comprises the Salinas synclinorium in the hangingwall of the CASZ, and besides the greenschist facies syn‐collisional metamorphism, records mainly a Buchan‐type metamorphic event, which took place under 3–5.5 kbar and up to 640°C at c. 530 Ma. The northwestern Araçuaí orogen exhibits, thus, a paired metamorphic pattern, in which the Barrovian and Buchan‐type metamorphic domains are juxtaposed by a normal‐sense shear zone. Lithospheric thinning during the extensional collapse of the orogen promoted ascent of the geotherms and melt generation. A large volume of granites was emplaced in the high grade and anatectic core of the orogen during this stage, and heat advected from these intrusions caused the development of Buchan facies series over a relatively large area. Renewed granite plutonism, hydrothermal activities followed by progressive cooling affected the system between 530 and 490 Ma.

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“…Desta forma, em termos gerais, o metamorfismo no Orógeno Araçuaí cresce de oeste para leste e de norte para sul (Almeida et al 1978, Pedrosa-Soares et al 1984, Trompette 1994, Pedrosa-Soares & Wiedemann-Leonardos 2000. Dados geotermobarométricos quantitativos indicam condições de metamorfismo em torno de 530-600 °C a 5,5 kbar na Formação Ribeirão da Folha (Pedrosa-Soares 1995, 470-640 °C a 4,5-5 kbar no Grupo Rio Doce e 770-930 °C a 5-7 kbar nos complexos Jequitinhonha e Nova Venécia (Munhá et al 2005, Castañeda et al, em preparação), ao passo que na Formação Salinas ocorre uma zona de baixa pressão (3-4 kbar) com temperatura variável entre 450 e 650 °C (Costa 1989, Pedrosa-Soares et al 1996; mas, localmente, o metamorfismo da Formação Salinas é de fácies xisto verde baixo, Lima et al 2002).…”

Section: Componentes E Estágios Orogênicosunclassified

Orógeno Araçuaí: Síntese Do Conhecimento 30 Anos Após Almeida 1977

Pedrosa-Soares

Noce

Alkmim

et al. 2013

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The Araçuaí Fold Belt was defined as the southeastern limit of the São Francisco Craton in the classicalpaper published by Fernando Flávio Marques de Almeida in 1977. This keystone of the Brazilian geologicliterature catalyzed important discoveries, such as of Neoproterozoic ophiolites and a calc-alkaline magmaticarc, related to the Araçuaí Belt and paleotectonic correlations with its counterpart located in Africa (the WestCongo Belt), that provided solid basis to define the Araçuaí-West-Congo Orogen by the end of the 1990thdecade. After the opening of the Atlantic Ocean in Cretaceous times, two thirds of the Araçuaí-West-CongoOrogen remained in the Brazil side, including records of the continental rift and passive margin phases ofthe precursor basin, all ophiolite slivers and the whole orogenic magmatism formed from the pre-collisionalto post-collisional stages. Thus, the name Araçuaí Orogen has been applied to the Neoproterozoic-Cambrianorogenic region that extends from the southeastern edge of the São Francisco Craton to the Atlantic coastlineand is roughly limited between the 15º and 21º S parallels. After 30 years of systematic geological mappingtogether with geochemical and geochronological studies published by many authors, all evolutionary stagesof the Araçuaí Orogen can be reasonably interpreted. Despite the regional metamorfism and deformation, thefollowing descriptions generally refer to protoliths. All mentioned ages were obtained by U-Pb method onzircon. The Macaúbas Group records rift, passive margin and oceanic environments of the precursor basinof the Araçuaí Orogen. From the base to the top and from proximal to distal units, this group comprises thepre-glacial Duas Barras and Rio Peixe Bravo formations, and the glaciogenic Serra do Catuni, Nova Auroraand Lower Chapada Acauã formations, related to continental rift and transitional stages, and the diamictitefreeUpper Chapada Acauã and Ribeirão da Folha formations, representing passive margin and oceanicenvironments. Dates of detrital zircon grains from Duas Barras sandstones and Serra do Catuni diamictitessuggest a maximum sedimentation age around 900 Ma for the lower Macaúbas Group, in agreement withages yielded by the Pedro Lessa mafic dikes (906 ± 2 Ma) and anorogenic granites of Salto da Divisa (875 ±9 Ma). The thick diamictite-bearing marine successions with sand-rich turbidites, diamictitic iron formation,mafic volcanic rocks and pelites (Nova Aurora and Lower Chapada Acauã formations) were depositedfrom the rift to transitional stages. The Upper Chapada Acauã Formation consists of a sand-pelite shelfsuccession, deposited after ca. 864 Ma ago in the proximal passive margin. The Ribeirão da Folha Formationmainly consists of sand-pelite turbidites, pelagic pelites, sulfide-bearing cherts and banded iron formations,representing distal passive margin to oceanic sedimentation. Gabbro and dolerite with plagiogranite veinsdated at ca. 660 Ma, and ultramafic rocks form tectonic slices of oceanic lithosphere thrust onto packagesof the Ribeirão da Folha Formation. The pre-collisional, calc-alkaline, continental magmatic arc (G1 Suite,630-585 Ma) consists of tonalites and granodiorites, with minor diorite and gabbro. A volcano-sedimentarysuccession of this magmatic arc includes pyroclastic and volcaniclastic rocks of dacitic composition datedat ca. 585 Ma, ascribed to the Palmital do Sul and Tumiritinga formations (Rio Doce Group), depositedfrom intra-arc to fore-arc settings. Detrital zircon geochronology suggests that the São Tomé wackes (RioDoce Group) represent intra-arc to back-arc sedimentation after ca. 594 Ma ago. The Salinas Formation, aconglomerate-wacke-pelite association located to northwest of the magmatic arc, represents synorogenicsedimentation younger than ca. 588 Ma. A huge zone of syn-collisional S-type granites (G2 Suite, 582-560Ma) occurs to the east and north of the pre-collisional magmatic arc, northward of latitude 20º S. Partialmelting of G2 granites originated peraluminous leucogranites (G3 Suite) from the late- to post-collisionalstages. A set of late structures, and the post-collisional intrusions of the S-type G4 Suite (535-500 Ma) andI-type G5 Suite (520-490 Ma) are related to the gravitational collapse of the orogen. The location of themagmatic arc, roughly parallel to the zone with ophiolite slivers, from the 17º30’ S latitude southwardssuggests that oceanic crust only developed along the southern segment of the precursor basin of the Araçuaí-West-Congo Orogen. This basin was carved, like a large gulf partially floored by oceanic crust, into the SãoFrancisco-Congo Paleocontinent, but paleogeographic reconstructions show that the Bahia-Gabon cratonicbridge (located to the north of the Araçuaí Orogen) subsisted since at least 1 Ga until the Atlantic opening.This uncommon geotectonic scenario inspired the concept of confined orogen, quoted as a new type ofcollisional orogen in the international literature, and the appealing nutcracker tectonic model to explain theAraçuaí-West-Congo Orogen evolution.

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Evolução Petrológica Para Uma Sequência De Rochas Metamórficas Regionais Do Tipo Baixa Pressão Na Regiâo De Itinga, Ne De Minas Gerais

Cited by 8 publications

References 0 publications

Late Neoproterozoic-Cambrian granitic magmatism in the Araçuaí orogen (Brazil), the Eastern Brazilian Pegmatite Province and related mineral resources

Late Neoproterozoic-Cambrian granitic magmatism in the Araçuaí orogen (Brazil), the Eastern Brazilian Pegmatite Province and related mineral resources

Metamorphic record of collision and collapse in the Ediacaran‐Cambrian Araçuaí orogen, SE‐Brazil: Insights from P–T pseudosections and monazite dating

Orógeno Araçuaí: Síntese Do Conhecimento 30 Anos Após Almeida 1977

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