Tesis
Granito São Francisco e formação Serra da Bocaina : evidências de magmatismo orosiriano em arco magmático continental : terreno Rio Apa - Sul do Cráton Amazônico
Fecha
2016-04-18Registro en:
SOUZA, Cinthya de Deus. Granito São Francisco e formação Serra da Bocaina: evidências de magmatismo orosiriano em arco magmático continental - terreno Rio Apa - Sul do Cráton Amazônico. 2016. 89 f. Dissertação (Mestrado em Geociências) - Universidade Federal de Mato Grosso, Instituto de Ciências Exatas e da Terra, Cuiabá, 2016.
Autor
Sousa, Maria Zélia Aguiar de
Ruiz, Amarildo Salina
http://lattes.cnpq.br/9641826735452419
http://lattes.cnpq.br/3596566506872372
Sousa , Maria Zélia Aguiar de
071.814.934-34
http://lattes.cnpq.br/3596566506872372
Pierosan, Ronaldo
915.271.120-04
http://lattes.cnpq.br/0165801213964884
071.814.934-34
023.741.338-85
Lafon, Jean Michel
293.750.102-87
http://lattes.cnpq.br/4507815620234645
Institución
Resumen
The Sao Francisco Granite and Serra da Bocaina Formation are located in the
southernmost part of the Amazon Craton - near the boundaries between Brazil-Bolivia-
Paraguay, southeast of the Brazilian state of Mato Grosso do Sul, Porto Murtinho City, which is
partially covered by Quaternary sediments of the Pantanal Formation and Alluvial Deposits.
Two petrographic facies have been identified in the Sao Francisco Granite based on geological
mapping and petrographic analysis: Biotite Monzo to Syenogranite and Alkali-feldspar Graphic
Granite. The former occurs only in the NE and SE of the study area being composed of pink to
greenish gray medium-grained leucocratic rocks which shows inequigranular hypidiomorphic to
xenomorphic textures. The latter is the dominant rock type in the batholith being composed of
pink to reddish porphyritic fine- to medium-grained leucocratic rocks with hypidiomorphic
texture as well as micrographic (granophyric) intergrowths. Two deformation stages are
observed: a ductile-brittle stage (F1) and a brittle stage (F2). The rocks of the Sao Francisco
Granite are hosted by volcanic rocks of the Serra da Bocaina Formation as highlighted by the
intrusion of dykes and apophyses. The Serra da Bocaina in the Sao Francisco Hill results from
effusive volcanism according to concordant subaerial volcanic deposits that occur in the form of
rhyolitic lava, but it is also attributed to explosive volcanism due to the occurrence of ignimbrite
deposits that are here divided into three petrographic facies: Lithic Ignimbrite, Crystal-rich
Ignimbrite and Ignimbrite Tuff. In the study area, xenoliths of tremolite-actinolite schist
belonging to the Porto Murtinho Complex, which composes the basement rock, are identified.
Geochemical data from the Sao Francisco Granite and volcanics of the Serra da Bocaina
Formation show that these rocks are of acid composition with magmatism emplacement in
magmatic arc settings; in post collisional stage, data also yield ferroan and peraluminous
affinities which are compatible with A-type granites. U-Pb zircon (SHRIMP) analyses yield
crystallization ages of 1878 ± 7 Ma for the Sao Francisco Granite, and 1899 ± 4 Ma for the
rhyolitic flows of Serra da Bocaina Formation. Whole-rock Sm-Nd analyses yield εNd(1,87 Ga)
negative values ranging from -3.65 to -2.53, and TDM ages 2.60 and 2.36 Ga that indicate these
rocks must have formed by partial melting of continental crust. The results show that the Sao
Francisco Granite and the volcanics of the Serra da Bocaina Formation are related to an
Orosirian plutonic and volcanic event which is attributed to the Amoguija Magmatic Arc.