Dejanira Luderitz Saldanha

Geochemical evidence concerning sources and petrologic evolution of Faial Island, Central Azores

Volcanic rocks that make up Faial Island, Central Azores, consist of four volcano-stratigraphic units, with ages between 730 ka and the present. Lavas range from alkali basalts to trachyandesites and belong to the alkaline-sodic series. The oldest unit is the Ribeirinha Volcanic Complex, generally characterized by low MgO contents. The Cedros Volcanic Complex is composed of basalts to benmoreites with low MgO contents. The Almoxarife Formation represents fissure flows, containing MgO contents similar to to slightly higher than those of the underlying Cedros Volcanic Complex. The youngest unit, the Capelo Formation, consists of mafic rocks with MgO values higher than those of the other units. Bulk-rock major and trace element trends suggest that differentiation of the three earliest units were dominated by fractional crystallization of plagioclase ± clinopyroxene ± olivine ± titanomagnetite. Capelo bulk-rock compositions are the most primitive, and are related to a period when volcanic activity was fed by deep magmatic chambers, and melts ascended more rapidly. Comparison among geochemical patterns of the trace elements suggests a strong similarity between the lavas from Faial and Pico islands. Corvo Island volcanism contrasts with the geochemistry of Faial and Pico lavas, reflecting its strong K and Rb depletion, and Th, U, Ta, Nb, La, and Ce enrichment. Absence of the Daly gap in the Faial volcanics is attributed to early crystallization of Ti-Fe oxides. The probable source of the Faial magma coincides with the MORB-FOZO array, which implies the presence of ancient recycled oceanic crust in the mantle source. Ratios of incompatible trace elements suggest the similarity of Corvo volcanic rocks with magmas derived from HIMU sources, whereas the Faial and Pico volcanic rocks could have been produced from sources very close to EMII-type OIB.

Rochas dioríticas do Platô da Ramada, Rio Grande do Sul, e sua relação com o vulcanismo alcalino da Formação Acampamento Velho, Neoproterozoico do Escudo Sul-Rio-Grandense

Acampamento Velho. Esta unidade e constituida por rochas vulcânicas de composicao predominantemente acida, com termos basicos associados, e corresponde a porcao extrusiva do magmatismo alcalino sodico de idade Neoproterozoica (570-550 Ma), vinculado aos estagios pos-colisionais do Ciclo Brasiliano-Panafricano no Escudo Sul-Rio-Grandense. O corpo intrusivo varia desde termos dioriticos ate quartzo-monzoniticos e sua afinidade alcalina sodica e atestada pelos padroes de elementos litofilos de grande raio ionico (LILE), elementos de elevado potencial ionico (HFSE) e elementos terras raras (ETR), cujas caracteristicas indicam sua correlacao com o magmatismo alto Ti da Formacao Acampamento Velho, descrito no Plato da Ramada. A evolucao do magmatismo alcalino da Formacao Acampamento Velho nesta regiao pode ser explicada, principalmente, por processos de cristalizacao fracionada envolvendo tres estagios principais, conforme resultados obtidos por meio de modelamentos petrogeneticos apresentados neste artigo. No entanto, face ao grande volume de rochas rioliticas de alta silica e a complexidade que envolve a geracao e a evolucao destes liquidos, a possibilidade de que tenham ocorrido processos de cristalizacao fracionada associados possivelmente a mecanismos de assimilacao crustal e grande. A identificacao e a caracterizacao de rochas intermediarias relacionadas a Formacao Acampamento Velho no Plato da Ramada indicam, portanto, que o magmatismo provavelmente evoluiu desde composicoes basicas ate acidas. Porem, a assertiva relacionada a bimodalidade do vulcanismo ainda permanece, devido a ausencia de lavas andesiticas. Tal ausencia pode ser atribuida a uma ‘barreira de densidade’ gerada pela diferenciacao dos liquidos basicos para intermediarios enriquecidos em FeO, os quais, por esta razao, estacionariam nos niveis crustais rasos.

Quantificação da dinâmica dos remanescentes florestais no município de Jaquirana, RS, em imagens de satélite

Techniques of remote sensing and geoprocessing were used to evaluate the dynamics of the vegetal cover, more specifically in Mixed Ombrophile Forest (Araucaria Forest) and Forestry classes in the Jaquirana, northeastern Rio Grande do Sul, from 2002 to 2007. The results showed a significant increase of forestry in detriment to natural forest covering in this short time period. The loss of the natural wood belonging to Mixed Ombrophile Forest was of 5,643.37 ha in a five-year period of time. On the other hand, the forestry area which was 921.10 ha in 2002, increased to 4,814.37 ha in 2007. It was also observed that large areas along the banks of the rivers Antas, Tainhas, and Camisas are now occupied by Pinus sp. crops.

Contribuições do solo e dossel em modelo de estimativa de biomassa aérea no Bioma Pampa

The objective of this work was to evaluate the predictive performance of the JONG models spectral submodel, with the insertion of variables considering contributions of different underlying soils and canopy densities. Indices calculated by subtraction and simple ratio between 4 and 3, 4 and 5, 4 and 7 bands, of Landsat 7/ETM+ sensor - were suggested in order to represent the spectral contribution of the different underlying soils and the influence of canopy structural differences. The spectral component parameterization was implemented by multiple linear regression and, then, it was compared to the biomass data measured in the field. Spectral variables that better describe the variations of initial biomass availability and soil spectral contributions were the soil fraction (spectral mixture linear model), and ratio between 4 and 7 bands. The spectral component of the JONG model, with the new parameterization, showed sensibility in eliminating the canopy and soil influences in the biomass initial availability and, also, improved the interpretation of results due to the relationship between selected spectral variables.

Spectral analysis of soils from mafic/ultramafic rocks of Cerro Mantiqueira, south-west of Rio Grande do Sul, Brazil

In remote sensing, information about an object of interest is most frequently derived by analysing the spectral characteristics of the electromagnetic energy emanating from it. In this context, the spectral characteristics of soils and rocks can provide useful information about their chemical and mineralogical composition. In this study, an investigation is conducted in order to examine the relationship between the spectral data as obtained by a spectroradiometer and the chemical and mineralogical composition of soils originated from mafic/ultramafic rocks. In order to help in understanding this relationship, the Karhunen–Loève (KL) transformation, also known as principal components (PC) transformation, was applied to the data to determine the relationship between spectral reflectance patterns and the soils chemical and mineralogical composition. The first three principal components (PC1, PC2 and PC3), i.e. the components associated with the three largest eigenvalues, were analysed. The experiments have shown that a clear interpretation can be assigned to each of the three components. The first component (PC1) can be related to the sample albedo. The second component (PC2) conveys information with respect to the slope of the samples spectral reflectance curve, from the visible to the infrared portions of the spectrum. The third component (PC3) relates to the contents of iron-bearing and calcium/magnesium-bearing minerals in the soil sample. The approach proposed in this study may help to better understand the relationship between the samples spectral pattern and its chemical and mineralogical composition.

ANÁLISE COMPARATIVA DO NDVI EM FITOFISIONOMIAS NA BACIA HIDROGRÁFICA DO RIO SÃO MARCOS

Este trabalho objetivou a comparacao da fenologia de fitofisionomias de cerrado e classes de cobertura da terra utilizando o Indice de Vegetacao por Diferenca Normalizada (NDVI) na Bacia Hidrografica do rio Sao Marcos. As etapas de trabalho foram: (1) identificacao espacial de cada classe de cobertura da terrautilizando o mapa de vegetacao PROBIO; (2) vetorizacao de amostras em cada uma das areas; (3) extracao das medias de NDVI para todas as cenas MODIS entre os anos 2001 e 2011 e (4) elaboracao dos graficos da serie temporal para cada fitofisionomia e classe de cobertura da terra. Os resultados mostraram semelhanca na distribuicao sazonal do NDVI para as areas de savana parque e gramineo-lenhosa, sendo que as diferencas anuais se dao em funcao da epoca chuvosa ou seca. A area de agricultura apresentou diferenca anual mais abrupta devido a ocorrencia de monocultura. Na area de atividade pecuaria ocorreu diferenca sazonal em funcao das epocas chuvosa e seca, e alteracao para valores maiores de NDVI a partir do ano 2005, possivelmente pela insercao de pastagem plantada no local. A utilizacao do NDVI permitiu a comparacao entre afenologia dasfitofisionomias e o entendimento da dinâmica de cobertura da terraque ocorre na area de estudo

Análise Temporal do Uso e Cobertura dos Solos no Município de São Jose dos Ausentes, Rio Grande do Sul, Brasil (Temporal Analysis of Use and Land Cover in the Municipality of São José dos Ausentes, Rio Grande do Sul, Brazil)

Esta pesquisa apresenta o levantamento de dados sobre alteracoes no uso e cobertura dos solos na regiao denominada Campos de Cima da Serra, nordeste do RS, visando identificar as formacoes vegetais mais impactadas nos ultimos vinte anos. Foram utilizadas imagens TM do satelite Landsat 5 dos anos de 1985 e 2009 e realizadas tecnicas de processamento digital com a geracao de imagens NDVI, composicao colorida, imagem mudanca, classificacao supervisionada e a geracao de mapas de uso e cobertura dos solos da regiao. Os dados levantados revelam a reducao de 24,42% na classe mata nativa, entre os anos de 1985 e 2009. Na classe florestamento houve expansao de, aproximadamente, 514% em relacao a 1985 . Constata-se um decrescimo de 4,93% na area de campos em relacao ao ano de 1985. Entretanto, e importante salientar que a extensao na area de campos, para o ano de 2009, pode ser menor devido a confusao espectral relacionada ao estagio de desenvolvimento de pinus s.p. sobre os campos. As alteracoes no uso e na cobertura dos solos nos ultimos vinte e quatro anos no municipio de Sao Jose dos Ausentes indicam estrategias de manutencao das propriedades rurais frente as restricoes economicas e de manejo com a introducao de novos usos do solo. Os cultivos agricolas de batata e o plantio de florestas exoticas ( Pinus s.p ) nos campos nativos consorciados as atividades tradicionais ligadas a pecuaria extensiva, e uma estrategia dos proprietarios contribuindo para a alteracao da paisagem dos Campos de Cima da Serra. Palavras Chave: Sensoriamento remoto, analise temporal, usos e cobertura dos solos, Campos de Cima da Serra Temporal Analysis of Use and Land Cover in the Municipality of Sao Jose dos Ausentes, Rio Grande do Sul, Brazil ABSTRACT This research presents the collection of data on changes in land use and land cover in the region called Campos de Cima da Serra, northeast of Rio Grande do Sul state, in order to identify the plant formations more impacted over the last twenty years. LANDSAT5 satellite images were used for the years 1985 and 2009 and digital processing techniques were performed resulting in NDVI imaging, color composite and change image, supervised classification, and generation of use and land cover maps of the region. The data collected show the decrease of 24.42% in native forest class, between the years 1985 and 2009. In foresting class there was expansion of approximately 514% compared to 1985. There is a decrease of 4.93% in the area of grasslands in relation to the year of 1985, however it is important to stress that the extension in the area of grasslands, for the year 2009, may be less due to spectral confusion related to the development stage of pinus s.p. over the fields. Changes in land use and cover over the past twenty-four years in the municipality of Sao Jose dos Ausentes indicate the strategies maintenance of rural properties facing the economic constraints and the stewardship with introduction of new uses of soil. Agricultural crops of potatoes and planting exotic forests (Pinus s. p) in native grassland linked to traditional activities associated to extensive livestock farming, is a proprietary strategy contributing to changing the landscape of Campos de Cima da Serra. Keywords: remote sensing, land use e land cover, Campos de Cima da Serra