Plate tectonic settings for Precambrian basic rocks from Brazil by multidimensional tectonomagmatic discrimination diagrams and their limitations

Abstract

Multidimensional discrimination diagrams (2006–2011) for basic and ultrabasic igneous rocks were applied to Precambrian rock suites from the Amazonian and São Francisco cratons, and the Tocantins Province, Brazil, to infer their possible tectonic settings. The chosen study cases in the Amazonian craton include the ca. 3.0 Ga metabasalts of the Identidade greenstone belt, 1.87–1.80 Ga Parauapebas anorogenic basalt-rhyolite dikes, 1.86–1.82 Ga Rio Branco anorogenic gabbro-basalt association, ca. 1.76–1.74 Ga Aripuanã and Teles Pires intracratonic basalt-felsic volcanic associations, and 1.76–1.74 Ga Jamari and 1.60–1.53 Ga Serra da Providência arc-related gabbroic rocks. In the São Francisco craton, we selected 1.48 Ga arc-related amphibolites of the Rio Capim greenstone belt, continental mafic dikes of Uauá (2.6 Ga), Curaçá and Chapada Diamantina (1.5 Ga), and Espinhaço (ca. 1.0 Ga). In the Tocantins Province, ca. 3.0 Ga komatiites associated with oceanic basalts of the Crixás and Guarinos greenstone belts were studied. The application of the diagrams generally provided consistent results with the authors’ proposed tectonic settings based on field relationships and geochemical data. The exceptions are some within-plate (continental) mafic dikes and basalts for which our diagrams do not work well. For comparison, we also used two ternary and two bivariate traditional discrimination diagrams for the data from the Amazonian craton, whose results were poorer than the newer multidimensional diagrams.

Keywords:

• multidimensional tectonic discrimination diagrams
• tectonic settings
• log–ratio transformation
• IgRocs and TecD computer program
• Amazonian and São Francisco craton
• central Brazil

Acknowledgements

We are highly thankful to Dr Ram Chandra and Dr Vinod K. Singh, organizers of the 3rd International Conference on Precambrian Continental Growth and Tectonism (PCGT–2013), Jhansi, India, for inviting us to present this work in this conference and to Professor Robert Stern, Editor-in-Chief, International Geology Review, for approving a special issue for publication of peer-reviewed papers. Moreover, our sincere gratitude goes to the students (Shaktiman, Sanjeet, Mahesh, and Ashish) of Bundelkhand University, Jhansi, India, for providing us with wonderful hospitality. We are thankful to anonymous reviewers for their numerous constructive suggestions.

Additional information

Funding

This work was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo, FAPESP, Brazil [grant number 2012/07243–3], [grant number 12/15824–6]; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico, CNPq, Brazil [grant number 308424/2011–5]; DGAPA–UNAM PAPIIT, México [grant number IN104813].