Geology and petrology of the Salto do Céu Suite: tectonic and stratigraphic implications on the SW Amazonian Craton

GABRIELLE APARECIDA DE LIMA, MOACIR JOSÉ BUENANO MACAMBIRA, MARIA ZÉLIA AGUIAR DE SOUSA, AMARILDO SALINA RUIZ, MARIA ELISA FROÉS BATATA, RONALDO PIEROSAN

Resumo


The basic rocks of the Salto do Céu Suite outcrop as sills and flows in the southwestern Amazon Craton, Rondonian-San Ignacio Province, with an age of about 1.44 Ga. Sills are 2 to 30 m thick being hosted by pelites of the Aguapei Group. The flows are up to 5 m thick and cover this unit. Typical textures of magma mingling are observed near the contact with granites of Rio Branco Suite. The Rio Branco Intrusive Suite is composed of basic and acid rocks, as well as hybrid rocks that indicate mixing processes between basic and acids magmas. U-Pb (TIMS zircon) results indicate ages around 1.4 Ga for both terms. The Salto do Céu Suite rocks have tholeiites affinity classified as subalkaline and iron-rich tholeiitic basalts, with mg# values between 0.30 and 0.51. They can be separated into two groups, based on LaN; one is richer in ETR with LaN greater than 100, while the other one has LaN less than 100. Rocks of the Salto do Céu Suite and Rio Branco Suite are interpreted as a bimodal suites showing magma mingling features such as those developed in continental intraplate settings, extensional regime associated to the Columbia/Nuna breakup.


Palavras-chave


Mafic flows and sills; Petrogenesis; Extensional tectonics; Amazonian Craton.

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DOI: http://dx.doi.org/10.1590/2317-4889201820160088

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