Abstract The Tamboril and Olho d’Água granitic stocks are part of the abundant calc-alkalic magmatic epidote-bearing granitic rocks in the Cachoeirinha–Salgueiro Terrane (CST) in the Transversal Zone Domain, northeastern Brazil. The equigranular Olho d’Água stock is composed of medium-grained clinopyroxene-amphibole–biotite tonalite; the porphyritic Tamboril stock is medium- to coarse-grained amphibole biotite ± clinopyroxene granodiorite. Abundances of clinopyroxene and epidote vary inversely in both stocks. Amphibole–rich clots are regarded as fragments from the source region captured by granodioritic/tonalitic magma during its ascent. Epidote composition in the Olho d’Água stock (Ps18–26) and in Tamboril stock (Ps17-20) is consistent with crystallization under oxygen fugacity between QFM and HM buffers. In the Olho d’Água stock, calculated values of pressure range from 5.1 to 6.6 kbar and in the Tamboril stock from 6.2 to 7.0 kbar. Solidification temperatures estimated from plagioclase-hornblende pairs in the Olho D´Água stock range from 637 to 679 °C and for Tamboril from 587 to 641 °C. Zr-saturation temperature estimates are 788 to 819 °C (Olho d’Água) and 807 to 829 °C (Tamboril). Altogether our data suggest that the studied stocks crystallized from two distinct magmatic pulses formed from fractional melting of a single amphibolitic source. These two magma pulses underwent subsequent crystallization, in a convective magmatic chamber, at rather high pressure.

RESUMO Esqueletos de corais contêm excelentes registros de condições ambientais passada, devido à sua longevidade e assinaturas geoquímicas bem calibradas. Registros de isótopos estáveis de C e O de isótopos em corais são especialmente interessantes, porque eles podem destacar a variabilidade multidecadal das condições climáticas locais além do registro instrumental com alta fidelidade e resolução sub-anual. Aqui nós relatamos um dos primeiros registros climáticos com base em coral do Atlântico Sul Equatorial, através de perfis isotópicos de duas colônias de Porites sp. do Atol das Rocas, um localchave para reconstruções climáticas e anteriormente não estudada. Aqui são apresentados dados de perfis ao longo do vale entre coralitos de uma colónia e na parte central do leque de coralitos de outra colónia. Embora exista diferenças significativas nos valores isotópicos entre as duas colônias, ainda são observados em ambas o registro do evento do ENSO 2009/2010 - um episódio de branqueamento do coral mundial - através de valores anômalos de δ18O negativos (até 1 permil mais negativo do que os valores de base). Valores de isótopos estáveis de C também aparentam ser afetada pelo evento do ENSO. Nossos resultados indicam que os corais do Atol das Rocas são substratos ideais para monitorar grandes oscilações climáticas no Oceano Atlântico tropical Sul.

ABSTRACT Coral skeletons contain records of past environmental conditions due to their long life span and well calibrated geochemical signatures. C and O isotope records of corals are especially interesting, because they can highlight multidecadal variability of local climate conditions beyond the instrumental record, with high fidelity and sub-annual resolution. Although, in order to get an optimal geochemical signal in coral skeleton, sampling strategies must be followed. Here we report one of the first coral-based isotopic record from the Equatorial South Atlantic from two colonies of Porites astreoides from the Rocas Atoll (offshore Brazil), a new location for climate reconstruction. We present time series of isotopic variation from profiles along the corallite valley of one colony and the apex of the corallite fan of the other colony. Significant differences in the isotopic values between the two colonies are observed, yet both record the 2009/2010 El Niño event - a period of widespread coral bleaching - as anomalously negative δ18O values (up to −1 permil). δ13C is found to be measurably affected by the El Niño event in one colony, by more positive values (+0.39 ‰), and together with a bloom of endolithic algae, may indicate physiological alteration of this colony. Our findings indicate that corals from the Rocas Atoll can be used for monitoring climate oscillations in the tropical South Atlantic Ocean.

We report for the first time the occurrence of organic-walled microfossils in Ediacaran limestones and marls of the Frecheirinha Formation, Ubajara Group, and the first Precambrian acritarchs so far reported for northeastern Brazil. The assemblage of the Frecheirinha Formation represents a low-diversity microflora comprising Leiosphaeridia, Lophosphaeridium and subordinated Bavlinella (=Sphaerocongregus). Their thermal alteration index (TAI) between 4+ and 5, suggests metamorphic temperatures exceeding 200-250°C. Higher temperatures are probably related to intruding granitic plutons (Meruoca, Mucambo). Reported δ13C values of carbonates of -3.5 ‰ VPDB (Vienna-Peedee Belemnite) at the base, passing up section into a positive plateau of up to +3.7 ‰, and corresponding 87Sr/86Sr values between 0.7075 and 0.7080 suggest an Ediacaran age. The acritarch assemblage is comparable to the Late Ediacaran Leiosphere Palynoflora (LELP) or Kotlin-Rovno assemblage, in broad agreement with chemostratigraphic data. Macrofossils belonging to the Ediacara fauna were reported from the overlying Jaibaras Group, which would constrain even further the depositional age of the Frecheirinha Formation to within ca. 575-555 Ma. A more comprehensive palynological study of the Frecheirinha Formation is necessary to confirm this age assignment.

Objetivou-se nesse trabalho avaliar o efeito de diferentes tratamentos pré- germinativos em sementes de Poincianella bracteosa e Poincianella pyramidalis. Foram testados os seguintes tratamentos: embebição em água por 24 horas; embebição em água a 80 ºC até atingir a temperatura ambiente; escarificação com lixa; escarificação com lixa seguida da embebição em água por 24 horas; escarificação química com ácido sulfúrico concentrado por 30 segundos, 1; 5 e 10 minutos e a testemunha. A avaliação do efeito dos tratamentos foi feita pelas variáveis: germinação, primeira contagem e índice de velocidade de germinação, comprimento da raiz principal e da parte aérea e a determinação da massa seca da raiz e da parte aérea das plântulas. Concluiu-se que as sementes de P. bracteosa e P. pyramidalis não apresentam dormência tegumentar.

The objective of this study was to evaluate the effect of different pre-germination treatments on seeds of Poincianella bracteosa and Poincianella pyramidalis. The following treatments were tested: soaking in water for 24 hours; soaking in water at 80 ºC until reaching room temperature; scarification with sandpaper; scarification followed by soaking in water for 24 hours; chemical scarification with concentrated sulphuric acid for 0.5, 1, 5 and 10 minutes; and a control. Evaluation of the effect of the treatments was made, employing the following variables: germination, first count and germination speed index, main root and shoot length, and determination of the root and shoot dry mass of the seedlings. It was concluded that the seeds of P. bracteosa and P. pyramidalis do not exhibit integumentary dormancy.

Propôs-se, no presente trabalho, determinar o procedimento de secagem e substratos ideais para avaliar a viabilidade e o vigor de sementes de pitangueira (Eugenia uniflora L.). O delineamento experimental adotado foi o inteiramente casualizado, em arranjo fatorial 2 x 4 (2 procedimentos de secagem: à sombra e ao sol; 4 substratos: Areia, vermiculita, pó-de-coco e papel toalha) com quatro repetições de 25 sementes cada uma. Caracterizou-se a curva de absorção de água pela semente e se avaliaram os seguintes parâmetros: germinação (%), primeira contagem de germinação (%), índice de velocidade de germinação e sementes mortas (%). O experimento foi conduzido em germinador do tipo BOD, regulado a temperatura constante de 25 ºC e regime de luz contínua. Nas condições em que o trabalho foi realizado, a secagem à sombra e o substrato vermiculita podem ser recomendados para avaliar a qualidade fisiológica, porque proporcionaram maior germinação e desenvolvimento inicial das plântulas de pitangueira.

The present work had as its objective to determine the ideal procedure of drying and the substrate to evaluate the viability and vigour of surinam cherry seeds (Eugenia uniflora L.). The experiment was developed in a completely randomized design in factorial scheme 2 x 4 (2 procedures of drying: shade and sun; 4 substrates: sand, vermiculite, coconut fiber and paper towels) with four replications of 25 seeds each. The water absortion curve was characterized and the following parameters were analyzed: germination percentage, first germination count (%), germination speed index and dead seeds (%). The experiment was conducted in a BOD germinator regulated at constant temperature of 25 ºC and regime of continuous light. In the conditions where the work was carried out, the drying under shade and vermiculite may be recommended to evaluate the vigour because they provided the best germination and initial development of surinam cherry seedlings.

Conduziu-se este trabalho com o objetivo de determinar o procedimento de secagem e substratos ideais para avaliar a visibilidade e o vigor das sementes e crescimento inicial das plântulas de pitangueira (Eugenia uniflora L.). Utilizou-se o delineamento inteiramente casualizado, em esquema fatorial 2 x 4 (2 procedimentos de secagem: à sombra e ao sol; 4 substratos: Areia, vermiculita, pó-de-coco e papel toalha), com quatro repetições de 25 sementes cada uma e se avaliaram os seguintes parâmetros: tempo médio de germinação, comprimento da raiz e do epicótilo e massa seca da plântula. O experimento foi conduzido em germinador tipo BOD, regulado a temperatura constante de 25 ºC e regime de luz contínua. O procedimento de secagem à sombra e o substrato vermiculita podem ser recomendados para testar o vigor dessa espécie.

This study had as its objective the determination of ideal procedure of drying and the substrate to evaluate the vigour and the initial growth of surinam cherry seedlings (Eugenia uniflora L.). The used design was entirely randomized in factorial scheme 2 x 4 (2 procedures of drying: shade and sun; 4 substrates: sand, vermiculite, coconut fiber and paper towels) with four replications of 25 seeds each. The following parameters were also analyzed: average time of germination, length of primary root and epicotyl and dry weight of the seedling. The experiment was conducted in BOD regulated at constant temperature of 25 ºC and regime of continuous light. The shade method of drying and the vermiculite substrate can be recommended to test the vigour of this specie.

Visando o efeito de tratamentos pré-germinativos (testemunha; imersão em ácido clorídrico por 3 min; cortes longitudinais sem e com embebição em água) e substratos (areia e pó de coco) na germinação de sementes de Platypodium elegans Vog avaliou-se, no presente estudo, a porcentagem total, a primeira contagem e a velocidade de germinação das sementes, o comprimento e a massa seca das plântulas. Não houve diferença significativa para a porcentagem de germinação (x = 51%), mas os cortes longitudinais proporcionaram maior velocidade de germinação (x = 0,95) e maior porcentagem na primeira contagem (x = 42%). O pó de coco e os cortes longitudinais promoveram maiores comprimento (x = 13,5 cm) e acumulação de massa seca (x = 50,0 mg) das plântulas.

The aim of this work was to evaluate the influence of germinative pretreatments (control; chloridric acid, for 3 min; longitudinal cuts without and with water soaking) and substrates (sand and coconut fiber) in the germination of Platypodium elegans Vog. seeds. The analyzed characteristics were: percentage of germination, first germination count, germination speed index, length and dry mass gain to seedlings. There was no significant difference for the germination percentage (x = 51%), but the longitudinal cuts promoted higher indices of germination speed (x = 0.95) and first germination count (x = 42%). The coconut fiber and the longitudinal cuts induced greater length (x = 13.5 cm) and dry mass gain (x = 50.0 mg) in the seedlings.

O pegmatito Alto Quixaba na região do Seridó, nordeste do Brasil, é um corpo subvertical de direção 60°/80°SW intrudindo discordante biotita xistos da Formação Seridó. Apresenta três zonas distintas em termos de mineralogia e textura, além de uma zona de alteração em forma de dique na qual ocorre, entre outros minerais-gema, elbaítas coloridas. As elbaítas ocorrem como cristais prismáticos alongados de acordo com o eixo C, com faces arredondadas e estrias paralelas a esse eixo. Os cristais são uniaxiais negativos e apresentam forte pleocroísmo; índices de refração nE = 1,619-1,622 e nO = 1.639-1.643, birrefrigência entre 0,019 e 0,021, densidade relativa de 3,07, e os parâmetros seguintes da célula unitária: ao = 15,845 Å, co = 7,085 Å e V = 1540,476 Å. O sítio X apresenta deficiência em álcalis entre 12 e 17%. As elbaítas são relativamente ricas em MnO (1,69 a 2,87%) e ZnO (até 2,98%).

The Alto Quixaba pegmatite, Seridó region, northeastern Brazil, is a 60º/80ºSW-trending subvertical dike discordantly intruded into biotite schists of the Upper Neoproterozoic Seridó Formation. It has three distinct mineralogical and textural zones, besides a replacement body that cuts the pegmatite at its central portion and in which occur, among other gem minerals, colored elbaites. Elbaites usually occur as prismatic crystals, elongate according to the c-axis, with rounded faces and striations parallel to this axis. Optically, crystals are uniaxial negative with strong pleochroism; refractive index extraordinary axis = 1.619-1.622 and ordinary axis = 1.639-1.643, birefringence between 0.019 and 0.021, average relative density of 3.07, and the following unit cell parameters: ao = 15.845 Å, co = 7.085 Å and V = 1540.476 Å. There is alkali deficiency in the X site of 12-17%. The elbaites are relatively enriched in MnO (1.69 to 2.87%) and ZnO (up to 2.98%).

Valores de isótopos de C e 87Sr/86Sr de cinco seqüências de carbonatos do Complexo São Caetano, nordeste do Brasil; foram usados para estimar a sua idade de deposição e relacionar variações da composição isotópica na água do mar com eventos tectônicos globais. Três estágios de variação de isótopos de carbono foram identificados de base para o topo numa seção quimioestratigráfica composta: (1) estágio em que delta13C varia de +2 a +3.7‰PDB (media 3‰PDB), (2) estágio no qual delta13C varia consideravelmente (de -2 a +3‰PDB) e (3) estágio apresentando valores constantes de cerca de +3.7‰PDB. Valores de 87Sr/86Sr ~ 0.70600 caracterizam o estágio isotópico 1, tornando-se mais variáveis no estágio isotópico 2 (entre ~ 0.70600 e ~ 0.70700). Finalmente, valores em torno de 0.70600 caracterizam o estágio isotópico 3. A quimioestratigrafía de C e Sr permite concluir que: (a) as curvas de variação seculares dos carbonatos do Complexo São Caetano registram flutuações primárias na composição isotópica de C e Sr da água do mar durante a passagem Meso-Neoproterozóico na Província Borborema; (b) o ciclo orogênico Cariris velhos/Greenville, a ocorrência de rifteamento e formação de arcos magmáticos continentais, e a formação do supercontinente Rodinia, controlaram a composição isotópica de C e Sr da água do mar durante os estágios isotópicos 1, 2, 3.

C-isotope and 87Sr/86Sr values for five carbonate successions from the São Caetano Complex, northeastern Brazil, were used to constrain their depositional age and to determine large variations in the C- and Sr-isotopic composition of seawater under the framework of global tectonic events. Three C-isotope stages were identified from base to top in a composed chemostratigraphic section: (1) stage in which delta13C values vary from +2 to +3.7‰ PDB and average 3‰ PDB, (2) stage with delta13C values displaying stronger oscillations (from -2‰ to +‰ PDB), and (3) stage with an isotopic plateau with values around +3.7‰ PDB. Constant 87Sr/86Sr values (~ 0.70600) characterize C-isotope stage 1, whereas slightly fluctuating values (from 0.70600 to 0.70700) characterize C-isotope stage 2. Finally, 87Sr/86Sr values averaging 0.70600 characterize C-isotope stage 3. The C- and Sr- chemostratigraphic pathways permit to state: (a) the C- and Sr-isotope secular curves registered primary fluctuations of the isotope composition of seawater during late Mesoproterozoic- early Neoproterozoic transition in the Borborema Province, and (b) onset of the Cariris Velhos/Greenville cycle, widespread oceanic rifting, continental magmatic arc formation and onset of the agglutination of Rodinia supercontinent, mostly controlled the C- and Sr-isotope composition of seawater during the C-isotope stages 1, 2 and 3.

Carbon isotope fluctuations in Precambrian sedimentary carbonates between 2.8 Ga and 0.60 Ga in Brazil are examined in this study. The carbonate facies of the BIF of the 2.8 Ga-old Carajás Formation, state of Pará in northern Brazil, has rather homogeneous delta13C (-5 o/ooPDB), compatible with carbonatization of a silicate protolith by a CO2-rich fluid from mantle degassing. The Paleoproterozoic Gandarela Formation, state of Minas Gerais, displays a narrow delta13C variation (-1.5 to +0.5 o/oo) compatible with carbon isotope signatures of carbonates deposited around 2.4 Ga worldwide. The Fecho do Funil Formation has probably recorded the Lomagundi delta13C positive anomaly (+6.4 to +7.1 o/ooPDB). The magnesite-bearing carbonates of the Orós mobile belt, state of Ceará, exhibit carbon isotope fluctuation within the range for carbonates deposited at 1.8 Ga. The C-isotope record of the Frecheirinha Formation, northwestern state of Ceará, shows negative delta13C values in its lower portion (-2 o/oo) and positive values up section (+1 to +3 o/oo), which suggests this sequence is a cap carbonate deposited after a glacial event around 0.95 Ga. The Jacoca and Acauã sedimentary carbonate Formations, state of Sergipe, NE Brazil, show carbon isotope fluctuations very similar to each other (average around -5 o/oo), compatible with a deposition around 0.76 Ga. The younger Olho D'Água carbonate Formation, however, also in the state of Sergipe, displays negative delta13C values at the lower portion of the Formation, changing dramatically up section to positive values as high as +10 o/oo, a characteristic compatible with a Sturtian cap carbonate deposited around 0.69 Ga. On the light of the C isotope data discussed in this study, it seems that delta13C fluctuations in Paleoproterozoic carbonates in Brazil are within the range found globally for metasedimentary carbonates of this age. Carbon isotope data proved to be very useful in establishing relative chronology of Neoproterozoic carbonate formations for which precise radiometric ages are not available.