Geochemistry of the Guaxupe Granulites, Minas Gerais, Brazil

Geochemical data for granulite terrain are presented from the northernmost portion of the Guaxupe Massif, at Mantiqueira Province, SE Brazil. Several types of granulites are recognized in the area: basic, intermediate and acid granulite. Major and trace elements (including REE) point to only one ma,oma source for these granulites generated at different times. Geochemical data point to plagioclase and apatite fractionation as responsable in the REE behaviour in intermediate and more basic rocks. Overall composition of the Guaxupe Granulites is similar to average composition of the lower crust.

Magmatismo há ca. 660 - 640 Ma no Domínio Socorro: Registros de convergência-colisional na Aglutinação do Gondwana Ocidental

Uranium-lead zircon ages between 660 and 640 Ma, obtained from a series of calc-alkaline orthogneisses and plutons in southeast Brazil's Central Mantiqueira Province, suggest that a significant period of magmatism occurred in this region prior to the collisional assembly of West Gondwana (presently constrained in the region between ca. 625 and 580 Ma). While the nature of this earlier magmatism is presently unclear, some preliminary Sm-Nd data suggest that these magmas were not solely derived from the Paleoproterozoic lithosphere, but appear to represent hybrid products of Paleoproterozoic and Neoproterozoic sources. As such hybrid mixtures have been most commonly observed in continental are settings, it is possible that the 660 to 640 Ma magmatism represents are magmatism that resulted from subduction of Neoproterozoic oceanic crust during early precollisional convergence and closure of a branch of either the Adamastor or Goianides oceans.

Evolução geológica dos batólitos granitóides neoproterozóicos do sudeste do estado de são paulo

The Neoproterozoic granitogenesis related to the Central Mantiqueira Province comprise the calc alkaline to alkaline granitoid complexes of Sorocaba, San Francisco, São Roque, Ibiúna and Piedade. These complexes occur in a ruptil tectonic to tardi (Sn+3) event. The emplacement of the different facies in transtractives structures of the pull-apart type are characterized in the area by the main transcurrent shear zones of Taxaquara-Pirapora, Itu-Jundiuvira, Moreiras, Cangüera and Caucáia of ENE-WSW general direction. The massifs present complex internal architecture characterized by intrusions in restrict initial phase of intermediate equigranular nature. Also present a main phase of porfiroid monzo and sienogranite that fragments the previous phase, followed by lateral accretion of equi to inequigranular material, and in some cases by the accretion of late phases of circular bodies of porfiroid rapakivi granites, and a late to final phase of aplitic to pegmatitic composition. This magmatism grew with the intrusions of successive magmatic pulses, partially controlled by many reactivations of the shear zones. The REE also suggest that the magmatic phases are similar, synchronous and repetitive in four of the complexes in both domains, present in the São Francisco Complex. The crystallization starts from accretion processes, but compositionally quite different from the others. The variation in compositions and ages (TDM) for these granites reflect the derivation from different sources developed under different magmatic conditions, followed by processes of contamination that frequently occur in the crust.

Petrologia e geoquímica das rochas graníticas do maciço do Capão Bonito, SP

The granitic massif Capão Bonito is located in the southwest of the State of São Paulo and is associated with Neoproterozoic evolution of Central Mantiqueira Province. Its rocks outcrop along the edge of the Paraná Basin in a body with elongated shape whose major axis has a general NE-SW, covering an area of approximately 110km2. Occurs in intrusive epimetamorphic rocks of Votuverava Formation, Acungui Group and granitic rocks of the Três Córregos Complex and their placement is related to a brittle tectonics of NE-SW direction shear zones. In metasediments, when preserved from deformational features imposed by mylonitic deformation, preserve up textures and mineralogy of contact metamorphism with development of mineral in albite-epidote and hornblende hornfels facies. The Massif Capão Bonito consists of red syenogranites, holo-leucocratic with biotite and rare hornblende, medium to coarse inequigranulars and isotropic lightly mylonitic and / or cataclastic in marginal regions. Commercially are called Vermelho Capão Bonito and for export as Ruby Red Granite. Rocks belonging to the calcium-alkaline high potassium to shoshonitic series or the series subalkaline potassic and metaluminous to peraluminous character. The magmatism is compatible with granite type A, tardi-orogenic to anorogenic of intraplate environment, from the crust material with lower melting emplacement associated with correlated transtensive structure to shear zones in an extensional environment at the end of collisional event of Orogênese Ribeira. Metamorphism occurred in the region in the greenschist facies, low to medium, generating quartzites, phyllites, schists, and calcium-silicate metabasics

Fishes of the Atlantic Rainforest of Boraceia: testimonies of the Quaternary fault reactivation within a Neoproterozoic tectonic province in Southeastern Brazil

The upper portion of the Rio Guaratuba, located in the Serra do Mar coastal range of Southeastern Brazil, shows biological and geological evidences of being captured and diverted away from its original course in the direction of the Parana River Basin to become a coastal river due to the Quaternary activity of NW-trending faults. Despite draining directly to the Atlantic Ocean, the upper portion of the Guaratuba still maintains an ichthyofauna that is typical of the adjoining Parana River Basin rather than the characteristic fish fauna of the Brazilian coastal drainages. The fish fauna of the upper Guaratuba is an evident testimony of the tectonic process that allowed the faunal interchange between the upland basins and the coastal drainages that probably has been taking place in Southeastern Brazil throughout the long geological history of the passive Brazilian continental margin.

Alimentação de peixes na microbacia do Ribeirão Grande, Serra da Mantiqueira oriental, SP

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Distribuição de peixes na microbacia do Ribeirão Grande, Serra da Mantiqueira Oriental, São Paulo, Brasil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Reproductive aspects of Harttia carvalhoi Miranda Ribeiro, 1939, a small loricariid from streams of serra da Mantiqueira eastern, SP, Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Relics of eclogite facies assemblages in the Ceara Central Domain, NW Borborema Province, NE Brazil: Implications for the assembly of West Gondwana

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

High-pressure granulites from Carire, Borborema Province, NE Brazil: Tectonic setting, metamorphic conditions and U-Pb, Lu-Hf and Sm-Nd geochronology

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Simulação do saldo de radiação na Serra da Mantiqueira

A influência do desmatamento da Mata Atlântica sobre o microclima da Serra da Mantiqueira ainda não é totalmente compreendida. Para conhecer as consequências do desmatamento sobre o clima serrano é necessário realizar estudos sobre o balanço de radiação na superfície. A falta de dados possibilita conjugar imagens de satélite com dados meteorológicos em um Sistema de Informação Geográfica na determinação do balanço de radiação. O presente estudo teve por objetivo avaliar o modelo MTCLIM em dias de céu claro ou nublado para simular o balanço de radiação na Serra da Mantiqueira, divisa entre os estados de São Paulo, Minas Gerais e Rio de Janeiro, Brasil. Imagens diárias, semanais e dezesseis dias do sensor MODIS disponíveis em 2003 foram utilizadas em rotinas específicas do MTCLIM. Alvos específicos foram selecionados para avaliar o comportamento do balanço de radiação. Observou-se que o balanço de radiação acompanhou a topografia local e é influenciado pelo tipo de uso da terra. Conclui-se que a temperatura da superfície contribui para aumentar a temperatura do ar implicando em diminuição do balanço de radiação sobre pastagem. O modelo MTCLIM demonstrou boa correlação para a temperatura do ar (R² = 0,82) e para a radiação solar global (R² = 0,71).

Mesoproterozoic rapakivi granites of the Rondonia Tin Province, southwestern border of the Amazonian craton, Brazil - I. Reconnaissance U-Pb geochronology and regional implications

Rapakivi granites and associated mafic and ultramafic rocks in the Rondonia Tin Province, southwestern Amazonian craton, Brazil were emplaced during six discrete episodes of magmatism between ca 1600 and 970 Ma. The seven rapakivi granite suites emplaced at this time were the Serra da Providencia Intrusive Suite (U-Pb ages between 1606 and 1532 Ma); Santo Antonio Intrusive Suite(U-Pb age 1406 Ma), Teotonio Intrusive Suite (U-Pb age 1387 Ma); Alto Candeias Intrusive Suite (U-Pb ages between 1346 and 1338 Ma); Sao Lourenco-Caripunas Intrusive Suite (U-Pb ages between 1314 and 1309 Ma); Santa Clara Intrusive Suite (U-Pb ages between 1082 and 1074 Ma); and Younger Granites of Rondonia (U-Pb ages between 998 and 974 Ma). The Serra da Providencia Intrusive Suite intruded the Paleoproterozoic (1.80 to 1.70 Ga) Rio Negro-Juruena crust whereas the other suites were emplaced into the 1.50 to 1.30 Ga Rondonia-San Ignacio crust. Their intrusion was contemporaneous with orogenic activity in other parts of the southwestern Amazonian craton, except for the oldest, Serra da Providencia Intrusive Suite. Orogenic events coeval with emplacement of the Serra da Providencia Intrusive Suite are not clearly recognized in the region. The Santo Antonio, Teotonio, Alto Candeias and Sao Lourenco-Caripunas Intrusive Suites are interpreted to represent extensional anorogenic magmatism associated with the terminal stages of the Rondonian-San Ignacio orogeny. At least the Sao Lourenco-Caripunas rapakivi granites and coeval intra-continental rift sedimentary rocks may, in contrast, represent the products of extensional tectonics and rifting preceding the Sunsas/Aguapei orogeny (1.25 to 1.0 Ga). The two youngest rapakivi suites, the Santa Clara Intrusive Suite and Younger Granites of Rondonia, seemingly represent inboard magmatism in the Rondonian-San Ignacio Province during a younger episode of reworking in the Rio Negro-Juruena Province during the waning stages of the collisional 1.1 to 1.0 Ga Sunsas/Aguapei orogeny. The six intra-plate rapakivi granite episodes in the southwestern part of the Amazonian craton form three broad periods of anorogenic magmatism that have age-correlative events composed of similar rocks and geologic environments in eastern Laurentia and Baltica, although the exact timing of magmatism appears slightly different. Recognition of lithologic and chronological correlations between various cratons provide important constraints to models explaining the interplay between rapakivi granite magmatism and deep crustal evolution of an early Mesoproterozoic supercontinent. They are, furthermore, important to plate tectonic models for the assembly, dispersal and reassembly of Amazonia, Laurentia and Baltica in the Mesoproterozoic and Neoproterozoic. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Geological evolution of the basement rocks in the east-central part of the Rondonia Tin Province, SW Amazonian craton, Brazil: U-Pb and Sm-Nd isotopic constraints

On the basis of geologic, petrologic, and U-Pb geochronologic data the basement rocks in the east-central part of the Rondonia Tin Province (RTP, southwestern Amazonian craton) are grouped into five lithologic associations: (1) tonalitic gneiss (1.75 Ga); (2) enderbitic granulite (1.73 Ga); (3) paragneiss; (4) granitic and charnockitic augen gneisses (1.57-1.53 Ga); and (5) fine-grained granitic gneiss and charnockitic granulite (1.43-1.42 Ga). The first three are related to development of the Paleoproterozoic Rio Negro-Juruena Province and represent the oldest crust in the region. The tonalitic gneisses and enderbitic granulites show calc-alkaline affinities and Nd isotopic compositions (initial epsilon(Nd) = +0-1 to -1.5; T-DM of 2.2-2.1 Ga) that suggest a continental arc margin setting for the original magmas. The paragneisses yield T-DM values of 2.2-2.1 Ga suggesting that source material was primarily derived from the Ventuari-Tapajos and Rio Negro-Juruena crusts, but detrital zircon ages and an intrusive granitoid bracket deposition between 1.67 and 1.57 Ga. The granitic and charnockitic augen gneisses show predominantly A-type and within-plate granite affinities, but also some volcanic arc granite characteristics. The initial epsilon(Nd) values (+0.6 to +2.0) indicate mixing of magmas derived from depleted mantle and older crustal sources. These rocks are correlated to the 1.60-1.53 Ga Serra da Providencia intrusive suite that reflects inboard magmatism coeval with the Cachoeirinha orogen located to the southeast. The fine-grained granitic gneiss and charnockitic granulites represent the first record of widespread magmatism at 1.43-1.42 Ga in northern Rondonia. Their geochemical signatures and the slightly positive initial epsilon(Nd) values (+0.7 to +1.2) are very similar to those of the most evolved granites of the calc-alkaline Santa Helena batholith farther southeast. U-Pb monazite and Sm-Nd whole-rock-garnet ages demonstrate that a high-grade tectonometa-morphic episode occurred in this region at 1.33-1.30 Ga. This episode attained upper-amphibolite conditions and is interpreted as the peak of the Rondonian-San Ignacio orogeny. The U-Pb and Sm-Nd data presented here and data published on rapakivi granites elsewhere indicate that the east-central part of the RTP is a poly-orogenic region characterized by successive episodes of magmatism, metamorphism, and deformation between 1.75 and 0.97 Ga. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Plutonism in three orogenic pulses, Eastern Blue Ridge Province, southern Appalachians

The Eastern Blue Ridge Province of the southern Appalachians contains, in part, remnants of an Ordovician accretionary wedge complex formed during subduction of an oceanic tract before mid-Ordovician accretion with Laurentia. The Eastern Blue Ridge Province consists of metapelite and amphibolite intruded by low-K plutons, high-temperature (T > 750 degrees C) Ordovician eclogite, and other high-pressure metamafic and meta-ultramatic rocks. Felsic plutons in the Eastern Blue Ridge Province are important time markers for regional-scale tectonics, deformation, and metamorphism. Plutons were thought to be related to either Taconian (Ordovician) or Acadian (Devonian-Silurian) tectonothermal events.We dated five plutonic or metaplutonic rocks to constrain pluton crystallization ages better and thus the timing of tectonism. The Persimmon Creek gneiss yielded a protolith crystallization age of 455.7 +/- 2.1 Ma, Chalk Mountain 377.7 +/- 2.5 Ma, Mt. Airy 334 +/- 3 Ma, Stone Mountain 335.6 +/- 1.0 Ma, and Rabun 335.1 +/- 2.8 Ma. The latter four plutons were thought to be part of the Acadian Spruce Pine Suite, but instead our new ages indicate that Alleghanian (Carboniferous-Permian) plutonism is widespread and voluminous in the Eastern Blue Ridge Province. The Chattahoochee fault, which was considered an Acadian structure, cuts the Rabun pluton and thus must have been active during the Alleghanian orogeny. The new ages indicate that Persimmon Creek crystallized less than 3 m.y. after zircon crystallization in Eastern Blue Ridge eclogite and is nearly synchronous with nearby high-grade metamorphism and migmatization. The three phases of plutonism in the Eastern Blue Ridge Province correspond with established metamorphic ages for each of the three major orogenic pulses along the western flank of the southern Appalachians.

The Rondonian-San Ignacio Province in the SW Amazonian Craton: An overview

The Rondonian-San Ignacio Province (1.56-1.30 Ga) is a composite orogen created through successive accretion of arcs, ocean basin closure and final oblique microcontinent-continent collision. The effects of the collision are well preserved mostly in the Paragua Terrane (Bolivia and Mato Grosso regions) and in the Alto Guapore Belt and the Rio Negro-Juruena Province (Rondonia region), considering that the province was affected by later collision-related deformation and metamorphism during the Sunsas Orogeny (1.25-1.00 Ga). The Rondonian-San Ignacio Province comprises: (1) the Jauru Terrane (1.78-1.42 Ga) that hosts Paleoproterozoic basement (1.78-1.72 Ga), and the Cachoeirinha (1.56-1.52 Ga) and the Santa Helena (1.48-1.42 Ga) accretionary orogens, both developed in an Andean-type magmatic arc; (2) the Paragua Terrane (1.74-1.32 Ga) that hosts pre-San Ignacio units (>1640 Ma: Chiquitania Gneiss Complex, San Ignacio Schist Group and Lomas Manechis Granulitic Complex) and the Pensamiento Granitoid Complex (1.37-1.34 Ga) developed in an Andean-type magmatic arc; (3) the Rio Alegre Terrane (1.51-1.38 Ga) that includes units generated in a mid-ocean ridge and an intra-oceanic magmatic arc environments; and (4) the Alto Guapore Belt (<1.42-1.34 Ga) that hosts units developed in passive marginal basin and intra-oceanic arc settings. The collisional stage (1.34-1.32 Ga) is characterized by deformation, high-grade metamorphism, and partial melting during the metamorphic peak, which affected primarily the Chiquitania Gneiss Complex and Lomas Manechis Granulitic Complex in the Paragua Terrane, and the Colorado Complex and the Nova Mamore Metamorphic Suite in the Alto Guapore Belt. The Paragua Block is here considered as a crustal fragment probably displaced from its Rio Negro-Juruena crustal counterpart between 1.50 and 1.40 Ga. This period is characterized by extensive A-type and intra-plate granite magmatism represented by the Rio Crespo Intrusive Suite (ca. 1.50 Ga), Santo Antonio Intrusive Suite (1.40-1.36 Ga), and the Teotonio Intrusive Suite (1.38 Ga). Magmatism of these types also occur at the end of the Rondonian-San Ignacio Orogeny, and are represented by the Alto Candeias Intrusive Suite (1.34-1.36 Ga), and the Sao Lourenco-Caripunas Intrusive Suite (1.31-1.30 Ga). The cratonization of the province occurred between 1.30 and 1.25 Ga. (C) 2009 Elsevier Ltd. All rights reserved.