Evaluation studies contribute to the identification of parameters that can affect the accuracy and precision of analytical methods. This study describes the analysis of δ18O and δ2H in water samples by the equilibrium method at the Isotope Geology Laboratory (LGI), Center for studies in Petrology and Geochemistry (CPGq) of the Federal University of Rio Grande do Sul (UFRGS). For that, six batches of analyzes were carried out under different ambient temperature conditions. For the reproducibility tests, four aliquots of the control sample were analyzed at the Polar Climate Center (CPC). Results showed that ambient temperature did not significantly affect the accuracy of the oxygen analysis. However, the mean result at 20 °C showed greater accuracy and acceptable precision. Hydrogen analyzes at a room temperature of 18 °C showed an external standard deviation and an internal precision exceeding the recommended, while at 20 and 22 °C the results were statistically acceptable, being the first more accurate. From that, it is possible to conclude that the determination of δ18O and δ2H in water at the LGI, employing the equilibrium method at an ambient temperature of 20 °C, showed satisfactory repeatability and reproducibility.

Abstract The Alfeu-I lamproite is one of the few alkaline rock occurrences in the South of Brazil that represents the alkaline event related to the South Atlantic opening and the enormous magmatic activity that formed the Paraná basalts. Alfeu-I lamproite is a diatreme facies and exhibits an inequigranular texture with macrocrysts of mica, spinel, garnet, and ilmenite and microcrysts of mica, pyroxene, and rare olivine, all immersed in a groundmass of pyroxene, spinel, perovskite, rutile, ilmenite, and, more rarely, olivine. Major element compositions of Alfeu-I pyroxene, garnet, ilmenite, mica, and olivine were determined by electron microprobe analyses, and trace element concentrations of clinopyroxene, garnet, ilmenite, and mica were measured using laser-ablation inductively coupled plasma mass spectrometry techniques. Temperature, pressure, and oxygen fugacity (fO2) conditions during the crystallization of Alfeu-I lamproite were calculated with the geothermobarometers and olivine, spinel, garnet, and orthopyroxene. The resulting mean equilibrium temperature ranges from 1375°C at 4 GPa to 1395°C at 5 GPa, whereas the fO2 points to ΔFMQ = +2.4 (at 4 GPa) and ΔFMQ = +2.2 (at 5 GPa). Rb-Sr and Sm-Nd isotopic data together with the trace element concentrations of minerals suggest that melting of a mantle source enriched in incompatible elements and volatiles due to previous subduction events occurred during the Gondwana breakup around 125 Ma ago. Fluids that may have originated from subducting slabs in the old subduction zone are probably the cause of the high fO2 conditions in Alfeu-I lamproite.

Abstract Trace elements provide crucial information about the origin and evolution of the Earth. One common issue regarding their analyses is the reduced analyte recovery during hot plate acid digestion for some geological samples. To overcome this, alkali fluxes (e.g., Lithium borate) have been used to produce an homogeneous synthetic glass that can be used then for both X-ray fluorescence (XRF) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). In this sense, we developed a method for LA-ICP-MS whole rock trace element analyses in glasses prepared by mixing high-purity sodium tetraborate and rock powders at high-temperature. We selected six international reference materials including peridotite (JP-1), basalt (BRP-1), kimberlite (SARM-39), pyroxenite (NIM-P), diorite (DR-N) and andesite (JA-1). Glasses were produced in a fully automatic fusion machine with step heating. Run products analyses were carried out on a Thermo® Element2 SF-ICP-MS coupled to a New Wave Research® Nd:YAG (213 nm) laser ablation system and on a Thermo® Element XR ICP-MS coupled to an Analyte G2 (193 nm) LA system. Results show that glasses are homogeneous and there is good agreement (generally > 90%) between our data and literature values for most trace elements, including large ion lithophile elements (LILE), high-field strength elements (HFSE) and rare-earth elements (REE).

Abstract The analysis of trace elements (TE) in geological materials is a valuable tool to understand geological processes, including studies in geochemistry and petrology. Among the methods applied to determine TE, Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) detects TE contents in the μg/g and ng/g range. The aim of this paper is to validate, at Laboratório de Geologia Isotópica (LGI) — Centro de Estudos em Petrologia e Geoquímica/Universidade Federal do Rio Grande do Sul (CPGq/UFRGS), a high-precision method for LA-ICP-MS analyses of TE in geological materials. Samples used in this work were reference Max-Planck-Institut für Chemie — Dingwell (MPI-DING) glasses. The method is used in tandem with the Electron Probe Microanalyzer — Wavelength Dispersive X-ray Spectrometer (EPMA-WDS) technique to determine the major and minor elements of the samples and check for homogeneity. Analyses were conducted in a Thermo® Element2 Inductively Coupled Mass Spectrometer (ICP-MS) coupled to a New Wave Research® Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) (213nm) laser ablation system. 43Ca and 29Si were used as internal standards (IS). Glitter® software and in-house spreadsheets were utilized for reduction treatments. The results using 29Si as IS present a high degree of fractionation errors compared to the results using 43Ca. Uncertainties caused by matrix interferences and fractionation effects can be corrected applying a correction factor. The obtained results demonstrate an effective recovery of TE content for the analyzed reference materials. Moreover, these silicate glasses proved to be robust to create an internal database of matrix matching standards in routine silicate analyses.

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.

Objetivou-se com o presente trabalho avaliar a influência dos porta-enxertos no que se refere ao crescimento vegetativo e desenvolvimento dos pessegueiro 'Chimarrita' e 'Maciel' em três locais de cultivo. O experimento foi desenvolvido em três locais de cultivo: 1 (Embrapa Uva e Vinho), 2 (EEA UFRGS) e 3 (CAP UFPel), em três anos. As cultivares de pessegueiro utilizadas foram: 'Chimarrita' e 'Maciel' enxertadas sobre seis porta-enxertos ('Aldrighi', 'Capdeboscq', 'Flordaguard', 'Nemaguard', 'Okinawa' e Umezeiro), no espaçamento 1,5 X 5,0m e conduzidas no sistema em "V". Foram avaliados: volume de copa, diâmetro de tronco, massa fresca da poda, produção por planta acumulada, comprimento, espessura, gemas floríferas e densidade florífera do ramo produtivo. Também foi avaliado de forma visual o ponto de enxertia. O porta-enxerto Umezeiro induziu menor vigor nos três locais de cultivo estudados e na média dos três anos. Ele pode ser indicado para utilização sob 'Maciel' nas condições edafoclimáticas do local 3. No local 1 o porta-enxerto, 'Nemaguard' possui alto vigor e maior produção acumulada, sendo o mais indicado. Já para o local 2, os porta-enxertos 'Capdeboscq', 'Okinawa' e 'Flordaguard' são os mais indicados. Os porta-enxertos afetam as características de crescimento e desenvolvimento das cultivares 'Chimarrita' e 'Maciel', o vigor destas é menor sobre o porta-enxerto Umezeiro nos três locais de cultivo. Todos os porta-enxertos podem ser indicados para os três locais de cultivo, com exceção do Umezeiro, que somente pode ser indicado em combinação com a cultivar 'Maciel' no local 3.

The objective of this study was to evaluate the influence of rootstocks in relation to vegetative growth and development of 'Chimarrita' and 'Maciel' peach trees in three places of cultivation. The experiment was conducted in three cultivating areas: first (Embrapa Grape and Wine), second (EEA UFRGS) and third (CAP UFPel), in three years. Peach trees cultivars used were: 'Chimarrita' and 'Maciel,' grafted on six rootstocks ('Aldrighi' 'Capdeboscq,' 'Flordaguard,' 'Nemaguard,' 'Okinawa' and Mume), with a spacing of 1.5m by 5.0m and conducted to a "V" system. It was evaluated: canopy volume, trunk diameter, pruning fresh weight, cumulative yield, length, thickness, flower bud and flower density of productive branch. It was also visually assessed the grafting point. The Mume rootstocks induced less vigor in the three cultivation areas studied, and in the average of three years. And it can be indicated for use on 'Maciel' at edaphoclimatic conditions of the third area. In the first area, the 'Nemaguard' rootstock has high vigor and greater cumulative production, being the best. As for the second area, the 'Capdeboscq,' 'Okinawa' and 'Flordaguard' rootstocks are the most suitable. It can be concluded that rootstocks affect the growth and development characteristics of 'Chimarrita' and 'Maciel' cultivars, the vigor of these is lower on the Mume rootstock in the three cultivating areas. All rootstocks can be indicated for the three areas of cultivation, with the exception of Mume, which can only be indicated in combination with 'Maciel' cultivar in the third area.