Figure 1:
Geotectonic setting of the Jequitinhonha Complex (cj), located in the northeastern part of the Araçuaí Orogen (modified from Pedrosa-Soares et al. 2008Pedrosa-Soares A.C., Alkmim F.F., Tack L., Noce C.M., Babinski M., Silva L.C., Martins-Neto M.A. 2008. Similarities and differences between the Brazilian and African counterparts of Neoproterozoic Araçuaí-West Congo orogen. : Pankhrust R., Trouw R., Brito-Neves B.B., Wit M. (eds). The Gondwana Peleocontinent in the South Atlantic Region Geological Society of London, Special Publications, 294:153-172.).
Figure 2:
Geological map of the Araçuaí Orogen (modified from
Pedrosa-Soares et al. 2007Pedrosa-Soares A.C., Noce C.M., Alkmim F.F., Silva L.C., Babinski M., Cordani U., Castañeda C. 2007. Orógeno Araçuaí: Síntese do Conhecimento 30 anos após Almeida 1977. Geonomos 15(1):1-16. ,
2008Pedrosa-Soares A.C., Alkmim F.F., Tack L., Noce C.M., Babinski M., Silva L.C., Martins-Neto M.A. 2008. Similarities and differences between the Brazilian and African counterparts of Neoproterozoic Araçuaí-West Congo orogen. : Pankhrust R., Trouw R., Brito-Neves B.B., Wit M. (eds). The Gondwana Peleocontinent in the South Atlantic Region Geological Society of London, Special Publications, 294:153-172.). The dashed rectangle shows the location presented in
Figure 3.
Figure 3:
Geological map and sections of the Almenara-Jequitinhonha region, northeastern Minas Gerais State, showing the location of the analysed samples. The map is partially compiled from Drumond & Malouf (2010Drumond J.B.V. , Malouf R.F. 2010. Carta Geológica, 1:100.000. Folha SE-24-V-A-III - Almenara Projeto Jequitinhonha, Programa Geologia do Brasil, CPRM.), Gomes (2010Gomes A.C.B. 2010. Carta Geológica, 1:100.000. Folha SE-24-V-A-VI - Rio do Prado. Projeto Jequitinhonha, Programa Geologia do Brasil, CPRM.), Junqueira et al. (2010Junqueira P.A., Gomes A.C.B., Raposo F.O, Paes V.J.C. 2010. Carta Geológica, 1:100.000. Folha SE-24-V-A-V - Joaíma Projeto Jequitinhonha, Programa Geologia do Brasil, CPRM.), and Pinto (2010Pinto C.P. 2010. Carta Geológica, 1:100.000. Folha SE-24-V-A-II - Jequitinhonha Projeto Jequitinhonha, Programa Geologia do Brasil , CPRM.).
Figure 4:
Petrographic features of rocks from the Jequitinhonha Complex. (A) Typical banded kinzigitic paragneiss. (B) Folded migmatite with dark grey kinzigitic paleosome and vein-shaped granitic leucosome. (C) Photomicrograph of kinzigitic gneiss under crossed polars, showing the regional foliation (qz: quartz; bt: biotite; cd: cordierite; gnt: garnet; sil: sillimanite); (D) Photomicrograph of kinzigitic gneiss under crossed polars, highlighting a peraluminous band composed of cordierite poikiloblasts (cd) with fibrous sillimanite (sil) roughly oriented along the regional foliation, intergrown with garnet (gnt). (E) Foliated, coarse-grained, sacaroidal quartzite of the Mata Escura Formation. (F) Medium- to coarse-grained quartzite intercalated in the kinigitic gneiss package.
Figure 5:
Major element bivariant diagrams for kinzigitic gneiss samples from different parts of the Jequitinhonha Complex, compared with schist samples of the Macaúbas Group.
Figure 6:
Major and trace element bivariant diagrams for kinzigitic gneiss samples from different parts of the Jequitinhonha omplex, compared with schist samples of the Macaúbas Group.
Figure 7:
Patterns of trace and rare earth elements of the Jequitinhonha Complex: Th / Sc values compared to those of trailing edge and juvenile arc-related sediments (Taylor & McLennan 1985Taylor S.R. , McLennan S.M. 1985. The Continental Crust: Its Composition and Evolution . Blackwell, Oxford. ), and LaN / YbN and Eu / Eu* values compared to passive margin turbidite muds and arc-related basins patterns (McLennan et al. 1990McLennan S.M., Taylor S.R., McCulloch M.T., Maynard J.B. 1990. Geochemical and Nd-Sr isotopic composition of deep-sea turbidites: Crustal evolution and plate tectonic associations. Geochimica et Cosmochimica Acta 54:2015-2050.).
Figure 8:
Rare earth elements patterns for paragneiss samples from the Jequitinhonha Complex. (a) Chondritenormalized diagram (Taylor & McLennan 1985Taylor S.R. , McLennan S.M. 1985. The Continental Crust: Its Composition and Evolution . Blackwell, Oxford. ), with a shaded field representing turbidite muds from trailing edge margins (McLennan et al. 1990McLennan S.M., Taylor S.R., McCulloch M.T., Maynard J.B. 1990. Geochemical and Nd-Sr isotopic composition of deep-sea turbidites: Crustal evolution and plate tectonic associations. Geochimica et Cosmochimica Acta 54:2015-2050.); (b) NASC-normalized diagram (Grommet et al. 1984Grommet L.P., Dymek R.F., Haskin L.A., Korotev R.L. 1984. The "North American shale composite": Its composition, major and trace element characteristics. Geochimica et Cosmochimica Acta , 48:2469-2482.).
Figure 9:
Selected cathodoluminoscence images and spot placement for zircons of sample JE03.
Figure 10:
Age histogram, probability density plot and Wetherill concordia diagram for U-Pb data from detrital zircon grains from sample JE-03.
Figure 11:
Detrital zircon age spectra of samples from the Jequitinhonha Complex in comparison to samples from the upper Macaúbas Group (passive margin) and the Rio Doce Group and Nova Venécia Complex (synorogenic arc-related basins). From: (1) Novo (2013Novo T.A. 2013. Caracterização do Complexo Pocrane, magmatismo básico mesoproterozóico e unidades neoproterozóicas do sistema Araçuaí-Ribeira, com ênfase em geocronologia U-Pb (SHRIMP e LA-ICP-MS) . Phd Thesis, Universidade Federal de Minas Gerais, Belo Horizonte, 193 p.); (2) Gradim et al. (2014Gradim C., Roncato J., Pedrosa-Soares A.C., Cordani U.G., Dussin I.A., Alkmim F.F., Queiroga G., Jacobsohn T., Silva L.C., Babinski M. 2014. The hot back-arc zone of the Araçuaí orogen, Eastern Brazil: from sedimentation to granite generation. Brazilian Journal of Geology , 44(1):155-180.); (3) this work; (4) GonçalvesDias et al. (2011Gonçalves-Dias T., Pedrosa-Soares A.C., Dussin I.A., Alkmim F.F., Caxito F.A., Silva L.C., Noce C.M. 2011. Idade máxima de sedimentação e proveniência do Complexo Jequitinhonha na área-tipo (Orógeno Araçuaí): primeiros dados U-Pb (LA-ICP-MS) de grãos detríticos de zircão. Geonomos 19(2):121-130.); (5) Peixoto et al. (2015Peixoto E.N., Pedrosa-Soares A.C., Alkmim F.F., Dussin I.A. 2015. A suture-related accretionary wedge formed in the Neoproterozoic Araçuaí orogen (SE Brazil) during Western Gondwanaland assembly. Gondwana Research 27:878-896.); (6) PedrosaSoares et al. (2000)Pedrosa-Soares A.C., Cordani U.G., Nutman A. 2000. Constraining the age of Neo-proterozoic glaciation in eastern Brazil: first U-Pb (SHRIMP) data of detrital zircons. Revista Brasileira de Geociências , 30:58-61.; (7) Kuchenbecker et al. (2015Kuchenbecker M., Pedrosa-Soares A.C., Babinski M., Fanning M. 2015. Detrital zircon age patterns and provenance assessment for pre-glacial to post-glacial successions of the Neoproterozoic Macaúbas Group, Araçuaí orogen, Brazil. Precambrian Research , 266:12-26.).
Figure 12:
Nd isotopic evolution diagram for paragneiss samples of the Jequitinhonha Complex, as compared with (a) the São Francisco Craton basement (Teixeira et al. 1996Teixeira W., Carneiro M.A., Noce C.M., Machado N., Sato K., Taylor P.N. 1996. Pb, Sr and Nd isotope constraints on the Archaean evolution of gneissic-granitoid complexes in the southern São Francisco Craton, Brazil. Precambrian Research 78:151-164., Noce et al. 2000Noce C.M., Macambira M.B., Pedrosa-Soares A.C. 2000. Chronology of Neoproterozoic-Cambrian granitic magmatism in the Araçuaí Belt, Eastern Brazil, based on single zircon evaporation dating. Revista Brasileira de Geociências , 30:25-29.) and Tonian rift volcanics of the West Congo belt (Tack et al. 2001Tack L., Wingate M.T.D., Liégeois J.P., Fernandez-Alonso M., Deblond A. 2001. Early Neoproterozoic magmatism (1000-910 Ma) of the Zadinian and Mayumbian groups (Bas-Congo): Onset of Rodinian rifting at the western edge of the Congo craton. Precambrian Research , 110:277-306.); and (b) Macaúbas Group samples (Babinski et al. 2012Babinski M., Pedrosa-Soares A.C., Trindade R.I.F. , Martins M., Noce C.M., Liu D. 2012. Neoproterozoic glacial deposits from the Araçuaí orogen, Brazil: Age, provenance and correlations with the São Francisco craton and West Congo belt. Gondwana Research 21(2-3):451-465. ).
Figure 13:
Tectonic model for the precursor basin of the Jequitinhonha Complex and its relations to the Macaúbas Group.