Produção Nacional
The hot back-arc zone of the Araçuaí orogen, Eastern Brazil: from sedimentation to granite generation
2014; Sociedade Brasileira de Geologia; Volume: 44; Issue: 1 Linguagem: Inglês
10.5327/z2317-4889201400010012
ISSN2317-4889
AutoresCamila Gradim, Jorge Roncato, Antônio Carlos Pedrosa‐Soares, Umberto G. Cordani, Ivo Dussin, Fernando F. Alkmim, Gláucia Queiroga, Tânia Jacobsohn, Luiz Carlos da Silva, Marly Babinski,
Tópico(s)earthquake and tectonic studies
ResumoThis article presents new lithochemical and geochronological data obtained from gneisses and granites occurring in the region located to the east of the Rio Doce calc-alkaline arc (630 -580 Ma), which corresponds to the back-arc basin of the Araçuaí orogen.The Nova Venécia Complex, represents the most fertile source of peraluminous granitic melts in the studied back-arc zone.It mostly consists of migmatitic Al-rich paragneisses, ranging from biotite-rich gneisses to biotite-free cordierite-rich granulites, whose main protoliths were graywacky sediments.An EW-oriented section across the northern back-arc region reveals a zone rich in cordierite granulites of the Nova Venécia Complex at the base, followed by migmatites that gradually pass to the Ataléia foliated granites rich in metasedimentary enclaves, which in turn lay beneath the Carlos Chagas batholith.To the south of the Carlos Chagas batholith, orthopyroxene-bearing rocks often occur in both the Nova Venécia Complex and the Ataléia Suite, suggesting a deeper crustal level.Our U-Pb data suggest that melting processes started on the Nova Venécia Complex during the late development of the Rio Doce arc, around 590 Ma, forming autochthonous peraluminous melts related to the Ataléia Suite.Progressive anatexis and melt accumulation attained the climax around 575 Ma, leading to the development of the syn-collisional Carlos Chagas batholith.Around 545 -530 Ma, a late to post-collisional anatectic episode formed garnet-cordierite leucogranites, mostly from the re-melting of the Ataléia and Carlos Chagas granites.A remarkable post-collisional plutonism caused widesperead re-heating of the back-arc domain from ca. 520 Ma to 480 Ma.This long lasting history (ca.110 Ma) of granite generation in the back-arc zone requires distinct heat sources, such as asthenosphere ascent under the back-arc region in the pre-collisional stage, thrust stacking of the hot arc onto the back-arc, radiogenic heat release from the collisional thickened crust and, finally, asthenosphere uprising during the gravitational collapse of the Araçuaí orogen.
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