The Archeane-Paleoproterozoic evolution of the Quadrilátero Ferrífero, Brasil : current models and open questions.
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2016
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The Quadril atero Ferrífero is a metallogenic district (Au, Fe, Mn) located at the southernmost end of the
S~ao Francisco craton in eastern Brazil. In this region, a supracrustal assemblage composed of Archean
greenstone and overlying NeoarcheanePaleoproterozoic sedimentary rocks occur in elongated keels
bordering domal bodies of Archean gneisses and granites. The tectonomagmatic evolution of the
Quadril atero Ferrífero began in the Paleoarchean with the formation of continental crust between 3500
and 3200 Ma. Although this crust is today poorly preserved, its existence is attested to by the occurrence
of detrital zircon crystals with Paleoarchean age in the supracrustal rocks. Most of the crystalline
basement, which is composed of banded gneisses intruded by leucogranitic dikes and weakly foliated
granites, formed during three major magmatic events: Rio das Velhas I (2920e2850 Ma), Rio das Velhas
II (2800e2760 Ma) and Mamona (2760e2680 Ma). The Rio das Velhas II and Mamona events represent a
subduction-collision cycle, probably marking the appearance of a modern-style plate tectonic regime in
the Quadril atero Ferrífero. Granitic rocks emplaced during the Rio das Velhas I and II events formed by
mixing between a magma generated by partial melting of metamafic rocks with an end member derived
by recycling gneissic rocks of older continental crust. After deformation and regional metamorphism at
ca. 2770 Ma, a change in the composition of the granitic magmas occurred and large volumes of high-K
granitoids were generated.
The ca. 6000 m-thick Minas Supergroup tracks the opening and closure of a basin during the NeoarcheanePaleoproterozoic,
between 2600 and 2000 Ma. The basal sequence involves continental to
marine sediments deposited in a passive margin basin and contain as a marker bed the Lake Superiortype
Cau^e Banded Iron Formation. The overlying sediments of the Sabar a Group mark the inversion of
the basin during the Rhyacian Minas accretionary orogeny. This orogeny results from the collision between
the nuclei of the present-day S~ao Francisco and Congo cratons, generated the fold-and thrust belt
structure of the Quadril atero Ferrífero. Afterwards, the post- orogenic collapse resulted in the deposition
of the Itacolomi Group and in the genesis of the dome-and-keel structure.
In this paper, we review current knowledge about the 1500 Ma long-lasting tectonomagmatic and
structural evolution of the Quadril atero Ferrífero identifying the most compelling open questions and
future challenges.
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Quadrilátero Ferrífero, Archean Paleoproterozoic, Tectonomagmatic evolution
Citação
FARINA, F. et al. The Archeane-Paleoproterozoic evolution of the Quadrilátero Ferrífero, Brasil: current models and open questions. Journal of South American Earth Sciences, v. 68, p. 4-21, 2016. Disponível em: <http://www.sciencedirect.com/science/article/pii/S0895981115300808>. Acesso em: 25 ago. 2017.