Petrogênese da suíte máfica do Domínio Macururé, Sistema Orogênico Sergipano, setor sul da Província Borborema

• Autor(a) principal: Pereira, Fábio dos Santos
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFS
• Texto Completo: http://ri.ufs.br/jspui/handle/riufs/11286
• topic: Geociências; Petrogênese; Rochas ígneas; Geoquímica; Geocronologia; Magmatismo; Cinturões orogênicos; Magmatismo máfico; Província Borborema; Neoproterozoico; Petrologia; Mafic magmatism; Borborema province; Neoproterozoic; Petrology; CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS

The Capela (20 km2), Dores (5 km2), Aquidabã (5 km2), Camará (10 km2), Campo Grande (4 km2) and Pedra Branca (1 km2) plutons are representatives of the mafic suite within the Macururé Domain, at the Sergipano Orogenic System. These bodies present elliptic shapes and occur structured according to the regional foliation of metasedimentary country rocks. U-Pb SHRIMP ages in zircon from Capela (631 ± 3 Ma), Aquidabã (636 ± 4 Ma) and Campo Grande (629 ± 9 Ma) plutons display the coeval emplacement of the intrusions. These plutons are dominantly constituted by diorites and gabbros, with subordinate granitic terms. Capela pluton differs from the others by presence of hornblendite cumulates. The mineralogy of these rocks is composed of plagioclase, calcic amphibole, magnesian biotite, enstatite, augite, diopside, quartz and microcline. Grossular-rich almandine occurs only in the Capela and Dores rocks. The main accessory minerals are epidote, titanite, apatite, allanite, zircon, pyrite and ilmenite. The magnesian character of mafic silicates, coupled with presence of magmatic epidote and titanite, suggest crystallization under high oxygen fugacity conditions, near to NNO buffer. Calcic garnet and magmatic epidote in paragenesis with amphibole and plagioclase reflect a minimum crystallization pressure of 8 kbar. The chemical compositions of pyroxenes, amphiboles and biotite point out affinity with calc-alkaline series and resemblance with arc cumulate suites. Geochemical data show that these rocks are high-K calc-alkaline to shoshonite, magnesian and metaluminous to weakly peraluminous. High LREE/HREE ratios and strong depletions in Nb, Ta and Ti are features of subduction-related magmatism. Trace elements compositions suggests that gabbros and diorites were generated by partial melting of an enriched subcontinental lithospheric mantle and evolved by fractional crystallization. Granites do not exhibit genetic correlation with the mafic rocks and certainly are melts produced during basic magmas emplacement into the lower crust. Field and petrographic evidences, together with geochemical and geochronological data, indicates that mafic rocks from Macururé Domain were emplaced in an early to syn-collisional stage during the build up of a continental arc in the Sergipano Orogenic System about 630 Ma ago.