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Petrografia e geoquímica dos ortoanfibolitos das unidades Novo Gosto e Gentileza, Domínio Canindé, Faixa de Dobramentos Sergipana, NE-BrasilLiz, Leidiane Cerqueira de Carvalho de 05 May 2017 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In the Canindé Domain, Northern portion of Sergipano Fold Belt, NE-Brazil, occur an
association of metamorfized mafic igneous rocks from the Novo Gosto and Gentileza
units.Those rocks represent important pieces in the Sergipano Fold Belt geological evolution.
The Canindé Domain has been scenario of several interpretations about the tectonic and
petrogenetic settings, due to intense deformation and metamorphism that obliterated much of
the Canindé Domain rocks original features. Petrographic and geochemical data from the
ortho-amphibolites of the Novo Gosto and Gentileza units showed this work contribute to
discuss the igneous processes involved in the protoliths genesis, therefore building up to the
Canindé Domain tectonic model definition and the major evolutionary aspects. The
petrographic data indicate that the studied rocks show Amphibolite Facies paragenesis,
marked by hornblende and plagioclase, with retrometamorphic transformations to Greenschist
Facies, defined by biotite, epidote, chlorite and sericite paragenesis. These transformations,
which were more intense in areas with shear zones concentrations, are probably, the result of
hydrothermal fluid action. In spite of the superimposed metamorphic processes, it was
possible to observe igneous relicts features, such as blast-glomeroporphiritic, blast-
intergranular and blast-subophytic textures. The chemical data suggest that the protoliths of
the studied rocks of the Novo Gosto and Gentileza units correspond to basalts with tholeiitic
affinity. These basalts are divided into high-Ti (> 2 % TiO 2 ) and low-Ti (< 1,19 % TiO 2 ).
Gentileza Unit rocks correspond to andesites and basaltic andesites with tholeiitic to calc-
alkaline affinity. The geochemical data interpretation suggest that the igneous protoliths of the
studied rocks of the Novo Gosto and Gentileza units were formed in a continental rift
environment, derived from magmas generated in different proportions of mixtures between
enriched and depleted reservoirs, with OIB-type components contribution. Ratios and
correlations among incompatible elements indicate crustal contamination participation in the
igneous protoliths generation of both units. / No Domínio Canindé, porção norte da Faixa de Dobramentos Sergipana, NE-Brasil, ocorrem
rochas ígneas máficas metamorfizadas das unidades Novo Gosto e Gentileza. Estas rochas
representam peças importantes na evolução geológica da faixa. O Domínio Canindé foi palco
de diversas interpretações quanto ao ambiente geotectônico e petrogenético, devido à intensa
deformação e metamorfismo, que obliteraram boa parte das feições originais das rochas do
domínio. Neste trabalho são apresentados e discutidos dados petrográficos e geoquímicos dos
ortoanfibolitos das unidades Novo Gosto e Gentileza, com o intuito de discorrer sobre os
processos ígneos envolvidos na gênese dos protólitos, de forma a contribuir com a definição
do ambiente tectônico de formação e dos principais aspectos evolutivos do Domínio Canindé.
Os dados petrográficos indicam que as rochas estudadas possuem uma paragênese
estabelecida no Fácies Anfibolito, marcada por hornblenda e plagioclásio, com
transformações retrometamórficas para o Fácies Xisto Verde, definidas por biotita, epídoto,
clorita e sericita. Essas transformações, que são mais intensas em áreas com concentrações de
zonas de cisalhamento, são possivelmente o resultado da ação de fluidos hidrotermais. Apesar
dos processos metamórficos superimpostos, foi possível observar feições ígneas reliquiares,
marcadas por texturas blasto-glomeroporfirítica, blasto-intergranular e blasto-subofítica. Os
dados químicos indicam, que os protólitos das rochas estudadas da Unidade Novo Gosto,
correspondem à basaltos de afinidade toleítica, que podem ser divididos em alto-Ti (> 2%
TiO 2 ) e baixo-Ti (< 1,19% TiO 2 ). As rochas da Unidade Gentileza correspondem, em sua
maioria, à andesitos e andesitos basálticos de afinidade toleítica a cálcio-alcalina. A
interpretação dos dados geoquímicos sugere que os protólitos ígneos das rochas estudadas
foram formados em um ambiente de rifte continental, derivados de magmas gerados a partir
de diferentes proporções de misturas entre reservatórios enriquecidos e empobrecidos, com
contribuição de componentes tipo-OIB. Razões e correlações entre elementos incompatíveis
sugerem a participação de contaminação crustal na geração dos protólitos ígneos das duas
unidades.
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Water content and geochemistry of the Cenozoic basalts in SE China : implications for enrichment in the mantle source of intra-plate basalts / Teneur en eau et géochimie des basaltes cénozoïques SE chinois : implication pour l'enrichissement de la source des basaltes continentauxLiu, Shaochen 22 March 2017 (has links)
Les teneurs en éléments majeurs et trace, les isotopes Sr-Nd-Pb, les teneurs en H2O et l’isotope de l’O des phénocristaux de cpx des basaltes cénozoïques de 11 sites du Sud Est Chinois situés dans des contextes géodynamiques variables ont été mesurés pour identifier les différents composants faisant partie de leur source. Les basaltes Cénozoïques de Zhejiang se sont mi en place durant deux périodes, 20-27Ma et après 11Ma. Leurs teneurs en H2O varient de 1.3-2.6%. Les basaltes Cénozoïques du Fujian ont fait éruption il y a moins de 10 Ma. Le teneurs en H2O initial des basaltes de Shiheng s’étend de 1.3-2.4%; les diabases de Bailin ont des teneurs s en eau estimés de 1.9-2.1%, et ceux de Mingxi des teneurs es initiaux de 0.3-0.5%. Les teneurs en H2O des basaltes de sont de 1.3-2.6%. Les basaltes de Xilong (Zhejiang), Mingxi (Fujian) et Leihuling (Hainan) ont des sources mantelliques contaminées par de la croûte océanique recyclée, ceux de Gaoping et Shuangcai (Zhejiang), Shiheng, Bailin et Niutuoshan (Fujian) et Maanling, Dayang et Fujitian (Hainan) voient leurs sources mantelliques contaminées par à la fois des sédiments et la croûte océanique recyclés. Les matériaux recyclés diffèrent suivant l’âge et la localisation. En résumé, les basaltes cénozoïques SE chinois ont des signatures élémentaires et isotopiques marquées par la présence de matériaux océaniques recyclés dans leurs sources mantelliques. Les matériaux recyclés varient entre les différentes localités, tant dans leurs proportions que leur degré d’évolution. Nos résultats montrent que la plaque subductée Ouest Pacifique affecte probablement la composition du manteau sous continentale du Sud Est Chinois / The major and trace element contents, Sr-Nd-Pb isotope, H2O contents and the cpx phenocryst O isotope of Cenozoic basalts from 11 places with distinct geological backgrounds in SE China have been measured to decipher the relationship between the possible recycled components and mantle geochemical heterogeneities. Zhejiang basalts erupted in two stages, 20-27Ma and after 11Ma. Their H2O contents range from 1.3-2.6%. The estimated H2O contents of initial basaltic melts for the Shiheng basalts range from 1.3-2.4%; the Bailin diabases have “fake” basaltic melt water contents from 1.9-2.1%; and the Mingxi basalts have initial H2O contents of 0.3-0.5%, in Fujian. H2O content the basalts from Leihuling (LH), Dayang (DY) and Fujitian (FJT) areas in Hainan are 2.7 wt. %, 1.3 wt. %, and 2.6 wt. %. The Xilong basalts from Zhejiang, Mingxi basalts from Fujian and Leihuling basalts from Hainan involved recycled oceanic crust components in the mantle source, while the Gaoping and Shuangcai basalts from Zhejiang, Shiheng, Bailin, and Niutoushan basalts from Fujian as well as the Maanling, Dayang and Fujitian basalts from Hainan involved recycled oceanic sediments and crust components in their mantle source. Overall, the SE China Cenozoic basalts have involved the recycled oceanic materials in their mantle source. The recycled oceanic materials have different existential state and locations, when the geological history of SE China are considered. The subducted Pacific slab most likely effect the composition of mantle in SE China
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