The Caninde domain, sergipano belt, Northeastern Brazil

Author(s)

Rosemery da Silva Nascimento

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Geociências
• Defense date: 2005-10-06

Examining board members

Elson Paiva de Oliveira; Asit Choudhuri; Alfonso Schrank; Caetano Juliani; Adejardo Francisco da Silva Filho

• Advisor: Elson Paiva de Oliveira

Abstract

The Sergipana belt is located in the northeastern region of Brazil, between the Pernambuco-Alagoas massif and the São Francisco craton. The Sergipana belt has been interpreted as the South American counterpart of the African Neoproterozoic Oubanguides belt, both developed during the Brazilian/PanAfrican cycle. The litho-structural array of the Sergipana belt is composed of several domains, with the Canindé domain that is located in the central part of that geotectonic unity. The Canindé domain comprises of metavolcano-sedimentary rocks that are crosscut by a gabbroic suite and several granite bodies (eg. Boa Esperança, Lajedinho, Sítios Novos and Xingo granites). The tectonic context in which these rocks were formed is controversial. Previous models considered the area as an ophiolitc complex, an intracontinental environment, or alternatively as an island arc. In this work the Canindé domain is characterized in terms of stratigraphy, geochemistry and geochronology. Trace-element contents (eg. Nb, Ta, Th, La) were used in order to define the geotectonic environment. Geo chronologic data were obtained on zircon by U-Pb SHRIMP and other conventional techniques. Pb-Pb isotopic analyses revealed an isochron of 963 ± 20 Ma for marbles associated with amphibolites and metasedimentary rocks. Sm-Nd data of metasedimentary rocks (Novo Gosto unity) indicated model ages (Tdm) of 1.5 Ga and 1.14 Ga. Tdm amphibolites are comprised between 1.3 Ga and 0.8 Ga. Amphibolites from the Gentileza unity have (Tdm) situated in the interval 1.2 and 0.8 Ga. Quartz-mozodiorites displaying rapakivi texture from the Gentileza unity present Tdm ages of ca. 0.89 Ga. The eNd(t=o) values of Novo Gosto and Gentileza unities are dominantly negative. SHRIMP data of Novo Gosto unity indicated different ages for the source rocks (977 Ma, 718 Ma and 679 Ma). U-Pb SHRIMP zircon data of the Gentileza unity and the Lajedinho granite are respectively 688 ± 15 Ma and 634 ± 10 Ma. The Gabbroic Suite Canindé was dated at 690 ± 16 Ma and quatz-monzodiorite rapakivi from the Gentileza unity by U-Pb conventional technique (zircon) revealed age 684 ± 10 Ma. It is suggested that the oldest sources of the Novo Gosto metasediment correspond to rocks from the Poço Redondo domain and the Pernambuco-Alagoas massif, whereas the youngest ones are those from the Canindé domain. Nd isotopic compositions and the negative Nb and Ta anomalies observed in rocks from the Novo Gosto and Gentileza unities associated with the anorogenic character of the granites and with the presence of rapakivi-textured diorites permit to propose that the Canindé domain developed in an intra-continental rift whose sedimentary history lasted until the Braziliano cycle. (AU)