Integration of elemental and isotope data supports a Neoproterozoic Adamastor Ocean realm
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Abstract
Figures
Figure 1 (a) Geological map of the Mantiqueira Province of southeastern South America in the context of (b) West Gondwana, with (c-f) elemental and (g-j) isotopic data from basic to felsic plutonic rocks and mafic-ultramafic bodies (see Supplementary Information for sources and references). |
Figure 1 |
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Introduction
The Cretaceous breakup of Gondwana in the South Atlantic region produced an asymmetric division of the Neoproterozoic Brasiliano/Pan-African Orogen (Fig. 1a,b) (Cordani et al., 2003
Cordani, U.G., Brito Neves, B.B., D’Agrella-Filho, M.S. (2003) From Rodinia to Gondwana: a review of the available evidence from South America. Gondwana Research 6, 275–283.
). A large part of the orogen remained in South America as the 3,000 km long and 100–500 km wide Mantiqueira Province (Almeida et al., 1981Almeida, F.F.M., Hasui, Y., Brito Neves, B.B., Fuck, R.A. (1981) Brazilian structural provinces: an introduction. Earth-Science Reviews 17, 1–29.
) (Fig. 1a).Early postulations of tectonic evolution of the Mantiqueira Province emphasised intra-continental models (e.g., Torquato and Cordani, 1981
Torquato, J.R., Cordani, U.G. (1981) Brazil-Africa geological links. Earth-Science Reviews 17, 155–176.
; Porada et al., 1989Porada, H. (1989) Pan-African rifting and orogenesis in southern to equatorial Africa and eastern Brazil. Precambrian Research 44, 103–136.
), an interpretation that received renewed attention in recent years (Cavalcante et al., 2019Cavalcante, C., Fossen, H., Almeida, R P., Hollanda, M.H.B., Egydio-Silva, M. (2019) Reviewing the puzzling intracontinental termination of the Araçuaí-West Congo orogenic belt and its implications for orogenic development. Precambrian Research 322, 85–98.
; Meira et al., 2019Meira, V.T., Garcia‐Casco, A., Hyppolito, T., Juliani, C., Schorscher, J.H.D. (2019) Tectono‐Metamorphic Evolution of the Central Ribeira Belt, Brazil: A Case of Late Neoproterozoic Intracontinental Orogeny and Flow of Partially Molten Deep Crust During the Assembly of West Gondwana. Tectonics 38, 3182–3209.
; Fossen et al., 2020Fossen, H., Cavalcante, C., Konopásek, J., Meira, V.T., Almeida, R.P., Hollanda, M.H.B., Trompette, R. (2020) A critical discussion of the subduction-collision model for the Neoproterozoic Araçuaí-West Congo orogen. Precambrian Research 343, 105715.
; Konopásek et al., 2020Konopásek, J., Cavalcante, C., Fossen, H., Janoušek, V. (2020) Adamastor–an ocean that never existed?. Earth-Science Reviews 205, 103201.
). However, a wealth of field, geochemical and geochronological data produced in recent decades progressively prompted interpretations involving distinct stages of typical Wilson cycle processes involved in the closure of the Adamastor Ocean (originally defined by Hartnady et al., 1985Hartnady, C., Joubert, P., Stowe, C. (1985) Proterozoic crustal evolution in southwestern Africa. Episodes 8, 236–244.
). Besides reworked Archean-Palaeoproterozoic basement, Neoproterozoic continental rift and passive margin successions, ocean floor assemblages and syn-orogenic basins were described. Those are intruded by large volumes of Cryogenian to Cambrian plutonic rocks typical of pre-collisional, collisional, and post-collisional stages (Fig. 1a), with temporal and spatial ordering leading to the present unraveling of a simple and reliable interpretation of a complete rift-drift-subduction-collision plate tectonic cycle. The archetypical examples of intracontinental orogens (Raimondo et al., 2014Raimondo, T., Hand, M., Collins, W.J. (2014) Compressional intracontinental orogens: Ancient and modern perspectives. Earth-Science Reviews 130, 128–153.
), as proposed in the last century and recently revived, lack many of the tectonic components recognised in the last decades in the Mantiqueira Province.Here we provide a new interpretation for a comprehensive database of 1,583 Hf-in-zircon (839 from Neoproterozoic, 744 from Archean-Palaeoproterozoic basement), 358 Sm-Nd isotope (221 and 137) and 824 bulk rock elemental geochemistry determinations of Neoproterozoic plutonic and volcanic rocks of the Mantiqueira Province (Supplementary Information), and demonstrate that these rocks are a testimony to an oceanic realm that was consumed to generate a Himalayas-sized orogen.
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Tonian-Cryogenian assemblages with Volcanic Arc Signatures
Tonian-Cryogenian tonalite-granodiorite orthogneisses with dioritic to mafic enclaves represent an expanded series of calc-alkaline, magnesian, metaluminous, I-type magmas along tholeiitic basalt (Fig. 1c–f). The 835–860 Ma Serra da Prata Complex of the central province has whole rock εNd(t) from +6.4 to +0.9 with TDM Nd of 860–1,200 Ma, 87Sr/86Sri < 0.7035, zircon εHf(t) from +14 to +10, and TDM Hf of 840–1,010 Ma (Peixoto et al., 2017
Peixoto, C.A., Heilbron, M., Ragatky, D., Armstrong, R., Dantas, E., Valeriano, C.M., Simonetti, A. (2017) Tectonic evolution of the Juvenile Tonian Serra da Prata magmatic arc in the Ribeira belt, SE Brazil: Implications for early west Gondwana amalgamation. Precambrian Research 302, 221–254.
; Heilbron et al., 2020Heilbron, M., Valeriano, C.M., Peixoto, C., Tupinambá, M., Neubauer, F., Dussin, I., Corrales, F., Bruno, H., Lobato, M., Almeida, J.C.H., Silva, L.G.E. (2020) Neoproterozoic magmatic arc systems of the central Ribeira belt, SE-Brazil, in the context of the West-Gondwana pre-collisional history: A review. Journal of South American Earth Sciences, 102710.
; Santiago et al., 2020Santiago, R., Caxito, F.A., Pedrosa-Soares, A., Neves, M., Dantas, E. (2020) Tonian island arc remnants in the northern Ribeira orogeny of western Gondwana: The Caxixe batholith (Espírito Santo state, SE Brazil). Precambrian Research 351, 105944.
). The Rio Negro Complex comprises intermediate to felsic plutonic rocks (620–790 Ma) with εNd(t) from +5 to −3 and 87Sr/86Sr < 0.705, as well as high K calc-alkaline to shoshonitic felsic rocks (605–620 Ma) with εNd(t) = −3 to −14 and 87Sr/86Sr = 0.7050–0.7100 (Tupinambá et al., 2012Tupinambá, M., Heilbron, M., Valeriano, C., Porto Jr., R., Dios, F.B., Machado, N., Silva, L.G.E., Almeida, J.C.H. (2012) Juvenile contribution of the Neoproterozoic Rio Negro magmatic arc (Ribeira Belt, Brazil): implications for western Gondwana amalgamation. Gondwana Research 21, 422–438.
).The São Gabriel terrane in the southern region (Fig. 1a) yielded U-Pb zircon ages of 800–860 Ma and 680–770 Ma (Babinski et al., 1996
Babinski, M., Chemale, F., Hartmann, L.A., Van Schmus, W.R., Silva, L.C. (1996) Juvenile accretion at 750–700 Ma in southern Brazil. Geology 24, 439–442.
; Saalmann et al., 2005Saalmann, K., Hartmann, L.A., Remus, M.V.D., Koester, E., Conceição, R.V. (2005) Sm–Nd isotope geochemistry of metamorphic volcano-sedimentary successions in the São Gabriel Block, southernmost Brazil: evidence for the existence of juvenile Neoproterozoic oceanic crust to the east of the Rio de la Plata craton. Precambrian Research 136, 159–175.
). Sm-Nd TDM are at 800–1,000 Ma with εNd(t) on the depleted mantle curve (up to +8, Babinski et al., 1996Babinski, M., Chemale, F., Hartmann, L.A., Van Schmus, W.R., Silva, L.C. (1996) Juvenile accretion at 750–700 Ma in southern Brazil. Geology 24, 439–442.
; Saalmann et al., 2005Saalmann, K., Hartmann, L.A., Remus, M.V.D., Koester, E., Conceição, R.V. (2005) Sm–Nd isotope geochemistry of metamorphic volcano-sedimentary successions in the São Gabriel Block, southernmost Brazil: evidence for the existence of juvenile Neoproterozoic oceanic crust to the east of the Rio de la Plata craton. Precambrian Research 136, 159–175.
) and zircon εHf(t) from +14 to +8 (Cerva-Alves et al., 2020Cerva-Alves, T., Hartmann, L.A., Remus, M.V.D., Lana, C. (2020) Integrated ophiolite and arc evolution, southern Brasiliano Orogen. Precambrian Research 341, 105648.
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Ediacaran Assemblages with Volcanic Arc Signatures
Widespread Ediacaran (mainly ca. 580–630 Ma) magmatic rocks represent an expanded series of medium to high K calc-alkaline, magnesian, metaluminous, I-type tonalites to granodiorites rich in dioritic to mafic enclaves, with minor gabbro (Fig. 1a) (Tedeschi et al., 2016
Tedeschi, M., Pedrosa-Soares, A., Dussin, I., Tassinari, C., Silva, L.C., Gonçalves, L.E., Alkmim, L., Lana, C., Figueiredo, C., Dantas E., Medeiros, S., Campos, C., Corrales, F., Heilbron, M. (2016) The Ediacaran Rio Doce magmatic arc revisited (Araçuaí-Ribeira orogenic system, SE Brazil). Journal of South American Earth Sciences 68, 167–186.
; Basei et al., 2018Basei, M.A.S., Frimmel, H.E., Campos Neto, M.C., Ganade de Araújo, C.E., Castro, N.A., Passarelli, C.R. (2018) The tectonic history of the southern Adamastor Ocean based on a correlation of the Kaoko and Dom Feliciano belts. In: Siegesmund S., Basei M., Oyhantçabal P., Oriolo S. (Eds.) Geology of Southwest Gondwana. Regional Geology Reviews. Springer, Cham., 63–85.
; Corrales et al., 2020Corrales, F.F., Dussin, I.A., Heilbron, M., Bruno, H., Bersan, S., Valeriano, C.M., Pedrosa-Soares, A.C., Tedeschi, M. (2020) Coeval high Ba-Sr arc-related and OIB Neoproterozoic rocks linking pre-collisional magmatism of the Ribeira and Araçuaí orogenic belts, SE-Brazil. Precambrian Research 337, 105476.
). The Rio Doce plutonic and volcanic rocks show εNd(t) of −2.9 to −13.6 with TDMNd of 1,190–2,030 Ma, 87Sr/86Sr of 0.7059–0.7165 and zircon εHf(t) of +2.3 to −11.7 (Tedeschi et al., 2016Tedeschi, M., Pedrosa-Soares, A., Dussin, I., Tassinari, C., Silva, L.C., Gonçalves, L.E., Alkmim, L., Lana, C., Figueiredo, C., Dantas E., Medeiros, S., Campos, C., Corrales, F., Heilbron, M. (2016) The Ediacaran Rio Doce magmatic arc revisited (Araçuaí-Ribeira orogenic system, SE Brazil). Journal of South American Earth Sciences 68, 167–186.
; Degler et al., 2017Degler, R., Pedrosa-Soares, A., Dussin, I., Queiroga, G., Schulz, B. (2017) Contrasting provenance and timing of metamorphism from paragneisses of the Araçuaí-Ribeira orogenic system, Brazil: Hints for Western Gondwana assembly. Gondwana Research 51, 30–50.
; Novo et al., 2018Novo, T.A., Pedrosa-Soares, A., Vieira, V.S., Dussin, I., Silva, L.C. (2018) The Rio Doce Group revisited: an Ediacaran arc-related volcano-sedimentary basin, Araçuaí orogen (SE Brazil). Journal of South American Earth Sciences 85, 345–361.
; Araújo et al., 2020Araújo, C., Pedrosa-Soares, A., Lana, C., Tedeschi, M., Dussin, I. (2020) Primeiro registro de magmatismo juvenil no arco magmático Rio Doce, Orógeno Araçuaí meridional. In: XVII Simpósio Nacional de Estudos Tectônicos (SNET), SBG, Bento Gonçalves, Annals, 105.
; Corrales et al., 2020Corrales, F.F., Dussin, I.A., Heilbron, M., Bruno, H., Bersan, S., Valeriano, C.M., Pedrosa-Soares, A.C., Tedeschi, M. (2020) Coeval high Ba-Sr arc-related and OIB Neoproterozoic rocks linking pre-collisional magmatism of the Ribeira and Araçuaí orogenic belts, SE-Brazil. Precambrian Research 337, 105476.
). The Pelotas-Florianópolis-Aiguá batholith forms a multi-intrusion geological structure consisting of granite, gabbro and diorite with 87Sr/86Sri ratios of ca. 0.712, εNd of −3.6 to −22.2 and TDMNd of 1,200–2,400 Ma (Babinski et al., 1997Babinski, M., Chemale, F., Van Schmus, W.R., Hartmann, L.A., Silva, L.C. (1997) U-Pb and Sm-Nd geochronology of the neoproterozoic granitic-gneissic Dom Feliciano Belt, southern Brazil. Journal of South American Earth Sciences 10, 263–274.
; Koester et al., 2016Koester, E., Porcher, C. C., Pimentel, M. M., Fernandes, L.A.D., Vignol-Lelarge, M.L., Oliveira, L.D., Ramos, R.C. (2016) Further evidence of 777 Ma subduction-related continental arc magmatism in Eastern Dom Feliciano Belt, southern Brazil: the Chácara das Pedras Orthogneiss. Journal of South American Earth Sciences 68, 155–166.
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Neoproterozoic Basic-Ultrabasic Assemblages
Accretionary mélanges of the northern province (Fig. 1a) include MORB chemistry metabasalt, banded metadolerite, metagabbro and meta-ultramafic rocks, with εNd(t) up to + 6.3 (Pedrosa-Soares et al., 1998
Pedrosa-Soares, A., Vidal, P., Leonardos, O.H., Brito Neves, B.B. (1998) Neoproterozoic oceanic remnants in eastern Brazil: further evidence and refutation of an exclusively ensialic evolution for the Araçuaí–West Congo orogen. Geology 26, 519–522.
; Amaral et al., 2020Amaral, L., Caxito, F.A., Pedrosa-Soares, A.C., Queiroga, G., Babinski, M., Trindade, R., Lana, C., Chemale, F. (2020) The Ribeirão da Folha ophiolite-bearing accretionary wedge (Araçuaí orogen, SE Brazil): new data for Cryogenian plagiogranite and metasedimentary rocks. Precambrian Research 336, 105522.
). Rootless plagiogranite veins hosted by a banded metadolerite are dated at 645 ± 10 Ma (Amaral et al., 2020Amaral, L., Caxito, F.A., Pedrosa-Soares, A.C., Queiroga, G., Babinski, M., Trindade, R., Lana, C., Chemale, F. (2020) The Ribeirão da Folha ophiolite-bearing accretionary wedge (Araçuaí orogen, SE Brazil): new data for Cryogenian plagiogranite and metasedimentary rocks. Precambrian Research 336, 105522.
).Mafic-ultramafic rock associations in the central sector include dunite cumulates, MORB- and IAT-like gabbro, metabasic rocks with sheeted dikes, pillow lavas and chert, emplaced at ca. 630 Ma (Tassinari et al., 2001
Tassinari, C.C., Munhá, J.M., Ribeiro, A., Correia, C.T. (2001) Neoproterozoic oceans in the Ribeira Belt (southeastern Brazil): The Pirapora do Bom Jesus ophiolitic complex. Episodes, 24, 245–251.
; Passarelli et al., 2018Passarelli, C.R., Basei, M.A.S., Siga Jr., O., Harara, O.M.M. (2018) The Luis Alves and Curitiba terranes: continental fragments in the Adamastor Ocean. In: Siegesmund S., Basei M., Oyhantçabal P., Oriolo S. (Eds) Geology of Southwest Gondwana. Regional Geology Reviews. Springer, Cham., 189–215.
).The 715–920 Ma MORB chemistry mafic-ultramafic assemblages in the southern sector have zircon εHf(t) up to +15 and mantle-like trace element signatures (Arena et al., 2017
Arena, K.R., Hartmann, L.A., Lana, C. (2017) Tonian emplacement of ophiolites in the southern Brasiliano Orogen delimited by U-Pb-Hf isotopes of zircon from metasomatites. Gondwana Research 49, 296–332.
, 2018Arena, K.R., Hartmann, L.A., Lana, C. (2018) U–Pb–Hf isotopes and trace elements of metasomatic zircon delimit the evolution of neoproterozoic Capané ophiolite in the southern Brasiliano Orogen. International Geology Review 60, 911–928.
; Hartmann et al., 2019Hartmann, L.A., Werle, M., Michelin, C.R.L., Lana, C., Queiroga, G., Castro, M.P., Arena, K.R. (2019) Proto-Adamastor ocean crust (920 Ma) described in Brasiliano Orogen from coetaneous zircon and tourmaline. Geoscience Frontiers 10, 1623–1633.
). Dravite in altered oceanic crust has typical ocean floor δ11B up to +1.8 (Hartmann et al., 2019Hartmann, L.A., Werle, M., Michelin, C.R.L., Lana, C., Queiroga, G., Castro, M.P., Arena, K.R. (2019) Proto-Adamastor ocean crust (920 Ma) described in Brasiliano Orogen from coetaneous zircon and tourmaline. Geoscience Frontiers 10, 1623–1633.
). The southernmost ophiolites show whole rock εNd(t) up to +8.5 (Peel et al., 2018Peel, E., Sanchez-Bettucci, L., Basei, M.A.S. (2018) Geology and geochronology of Paso del Dragón Complex (northeastern Uruguay): Implications on the evolution of the Dom Feliciano Belt (Western Gondwana). Journal of South American Earth Sciences 85, 250–262.
; Ramos et al., 2020Ramos, R.C., Koester, E., Vieira, D.T. (2020) Sm–Nd systematics of metaultramafic-mafic rocks from the Arroio Grande Ophiolite (Brazil): Insights on the evolution of the South Adamastor paleo-ocean. Geoscience Frontiers, doi: 10.1016/j.gsf.2020.02.013.
) (Fig. 1a).top
Discussion
The time dependent variation of isotopic trends (Fig. 1g–j) is interpreted as a shift from Tonian-Cryogenian juvenile settings fingerprinting intra-oceanic arcs to Ediacaran settings with magmas formed by mixing of mantle wedge melts and anatectic melts from both the Tonian-Cryogenian rocks and the Archean-Palaeoproterozoic basement. The resulting mixed melts intruded active continental margin settings similar to Andean volcanic arcs. The protracted consumption of oceanic lithosphere is required, and this is attested by the associated ophiolites along the entire length of the Mantiqueira Province.
Recently revisited models of intracontinental orogeny focused on a “space problem” for the development of an Adamastor oceanic realm based on estimates of maximum oceanic width using modern spreading and subduction rates (Fossen et al., 2020
Fossen, H., Cavalcante, C., Konopásek, J., Meira, V.T., Almeida, R.P., Hollanda, M.H.B., Trompette, R. (2020) A critical discussion of the subduction-collision model for the Neoproterozoic Araçuaí-West Congo orogen. Precambrian Research 343, 105715.
; Konopásek et al., 2020Konopásek, J., Cavalcante, C., Fossen, H., Janoušek, V. (2020) Adamastor–an ocean that never existed?. Earth-Science Reviews 205, 103201.
). However, those estimates are contingent and cannot be used as hard proof against mobilistic models, because: 1) the ocean was probably fragmented in smaller sub-domains such as in the present day western Pacific and also connected to a much large Neoproterozoic oceanic system (Cordani et al., 2003Cordani, U.G., Brito Neves, B.B., D’Agrella-Filho, M.S. (2003) From Rodinia to Gondwana: a review of the available evidence from South America. Gondwana Research 6, 275–283.
) (Fig. 1b); 2) the Neoproterozoic upper mantle was warmer, leading to distinct spreading and subduction rates and dynamics (Brown, 2014Brown, M. (2014) The contribution of metamorphic petrology to understanding lithosphere evolution and geodynamics. Geoscience Frontiers 5, 553–569.
); 3) intense wrench tectonics with thousands-of-km long shear zones obliterated former low angle surfaces and displaced allochthonous units far from their original position; 4) age, size and time span of an ocean have little significance in determining whether subduction is feasible or not (Hall, 2019Hall, R. (2019) The subduction initiation stage of the Wilson cycle. Geological Society, London, Special Publications 470, 415–437.
), while lithospheric weaknesses such as magma-rich rift systems present in the orogen precursor basins (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 Rodinia rifting at the western edge of the Congo craton. Precambrian Research 110, 277–306.
; Basei et al., 2008Basei, M.A.S., Frimmel, H.E., Nutman, A.P., Preciozzi, F. (2008) West Gondwana amalgamation based on detrital zircon ages from Neoproterozoic Ribeira and Dom Feliciano belts of South America and comparison with coeval sequences from SW Africa. Geological Society, London, Special Publications 294, 239–256.
) might play a major role in subduction initiation (Stern and Gerya, 2018Stern, R.J., Gerya, T. (2018) Subduction initiation in nature and models: A review. Tectonophysics 746, 173–198.
); 5) those calculations use a palinspastic incorrect pre-drift reconstruction, ignoring at least ca. 280 km of restored continental crust now stretched in the Brazilian and African passive margins (Aslanian et al., 2009Aslanian, D., Moulin, M., Olivet, J. L., Unternehr, P., Matias, L., Bache, F., Rabineau, M., Nouzé, H., Klingelheofer, F., Contrucci, I., Labails, C. (2009) Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints. Tectonophysics 468, 98–112.
); 6) the termination of the orogen in a gulf partially enclosed by continental crust implies much lower convergence rates; and 7) non-Euclidean geometry implies the diachronous along strike opening and closure of oceanic basins. Thus, calculations of former oceanic width are interesting hypothetical exercises, but the field, petrographic, isotopic, elemental and geochronological data sets cannot be considered as subordinated to it.The striking coherence of evidence from various geological disciplines (detailed field, petrographic and structural studies, bulk rock chemistry, isotope geochemistry, quantitative geothermobarometry and petrology) support a solid interpretation for the tectonic units and their arrangement in time and space to be explained better through the development and consumption of an oceanic realm in the Mantiqueira Province. The evidence provided here suggests that the main ocean was located to the west of the arc rocks, where recently paired HP-HT metamorphic belts were described (Ricardo et al., 2020
Ricardo, B.S., Faleiros, F.M., Moraes, R., Siga Jr., O., Campanha, G.A. (2020) Tectonic implications of juxtaposed high-and low-pressure metamorphic field gradient rocks in the Turvo-Cajati Formation, Curitiba Terrane, Ribeira Belt, Brazil. Precambrian Research, 105766.
). The original proposition of Hartnady et al. (1985)Hartnady, C., Joubert, P., Stowe, C. (1985) Proterozoic crustal evolution in southwestern Africa. Episodes 8, 236–244.
would correspond to the Marmora back-arc basin in the African counterparts, east of the Pelotas arc (Frimmel et al., 2011Frimmel, H.E., Basei, M.S., Gaucher, C. (2011) Neoproterozoic geodynamic evolution of SW-Gondwana: a southern African perspective. International Journal of Earth Sciences 100, 323–354.
; Basei et al., 2018Basei, M.A.S., Frimmel, H.E., Campos Neto, M.C., Ganade de Araújo, C.E., Castro, N.A., Passarelli, C.R. (2018) The tectonic history of the southern Adamastor Ocean based on a correlation of the Kaoko and Dom Feliciano belts. In: Siegesmund S., Basei M., Oyhantçabal P., Oriolo S. (Eds.) Geology of Southwest Gondwana. Regional Geology Reviews. Springer, Cham., 63–85.
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Acknowledgements
We dedicate this article to the memory of Koji Kawashita, a pioneering, devoted scientist who dedicated his career to the implementation of many isotope geology laboratories in Brazil. The authors acknowledge the Brazilian Scientific and Technological Development Council (CNPq) for their research grants. Comments by Craig Storey and Hartwig Frimmel are acknowledged. This is a contribution to Project MOBILE (
Editor: Horst R. Marschall
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References
Almeida, F.F.M., Hasui, Y., Brito Neves, B.B., Fuck, R.A. (1981) Brazilian structural provinces: an introduction. Earth-Science Reviews 17, 1–29.
Show in context
A large part of the orogen remained in South America as the 3,000 km long and 100–500 km wide Mantiqueira Province (Almeida et al., 1981) (Fig. 1a).
View in article
Amaral, L., Caxito, F.A., Pedrosa-Soares, A.C., Queiroga, G., Babinski, M., Trindade, R., Lana, C., Chemale, F. (2020) The Ribeirão da Folha ophiolite-bearing accretionary wedge (Araçuaí orogen, SE Brazil): new data for Cryogenian plagiogranite and metasedimentary rocks. Precambrian Research 336, 105522.
Show in context
Accretionary mélanges of the northern province (Fig. 1a) include MORB chemistry metabasalt, banded metadolerite, metagabbro and meta-ultramafic rocks, with εNd(t) up to + 6.3 (Pedrosa-Soares et al., 1998; Amaral et al., 2020).
View in article
Rootless plagiogranite veins hosted by a banded metadolerite are dated at 645 ± 10 Ma (Amaral et al., 2020).
View in article
Araújo, C., Pedrosa-Soares, A., Lana, C., Tedeschi, M., Dussin, I. (2020) Primeiro registro de magmatismo juvenil no arco magmático Rio Doce, Orógeno Araçuaí meridional. In: XVII Simpósio Nacional de Estudos Tectônicos (SNET), SBG, Bento Gonçalves, Annals, 105.
Show in context
The Rio Doce plutonic and volcanic rocks show εNd(t) of −2.9 to −13.6 with TDMNd of 1,190–2,030 Ma, 87Sr/86Sr of 0.7059–0.7165 and zircon εHf(t) of +2.3 to −11.7 (Tedeschi et al., 2016; Degler et al., 2017; Novo et al., 2018; Araújo et al., 2020; Corrales et al., 2020).
View in article
Arena, K.R., Hartmann, L.A., Lana, C. (2017) Tonian emplacement of ophiolites in the southern Brasiliano Orogen delimited by U-Pb-Hf isotopes of zircon from metasomatites. Gondwana Research 49, 296–332.
Show in context
The 715–920 Ma MORB chemistry mafic-ultramafic assemblages in the southern sector have zircon εHf(t) up to +15 and mantle-like trace element signatures (Arena et al., 2017, 2018; Hartmann et al., 2019).
View in article
Arena, K.R., Hartmann, L.A., Lana, C. (2018) U–Pb–Hf isotopes and trace elements of metasomatic zircon delimit the evolution of neoproterozoic Capané ophiolite in the southern Brasiliano Orogen. International Geology Review 60, 911–928.
Show in context
The 715–920 Ma MORB chemistry mafic-ultramafic assemblages in the southern sector have zircon εHf(t) up to +15 and mantle-like trace element signatures (Arena et al., 2017, 2018; Hartmann et al., 2019).
View in article
Aslanian, D., Moulin, M., Olivet, J. L., Unternehr, P., Matias, L., Bache, F., Rabineau, M., Nouzé, H., Klingelheofer, F., Contrucci, I., Labails, C. (2009) Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints. Tectonophysics 468, 98–112.
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However, those estimates are contingent and cannot be used as hard proof against mobilistic models, because: 1) the ocean was probably fragmented in smaller sub-domains such as in the present day western Pacific and also connected to a much large Neoproterozoic oceanic system (Cordani et al., 2003) (Fig. 1b); 2) the Neoproterozoic upper mantle was warmer, leading to distinct spreading and subduction rates and dynamics (Brown, 2014); 3) intense wrench tectonics with thousands-of-km long shear zones obliterated former low angle surfaces and displaced allochthonous units far from their original position; 4) age, size and time span of an ocean have little significance in determining whether subduction is feasible or not (Hall, 2019), while lithospheric weaknesses such as magma-rich rift systems present in the orogen precursor basins (Tack et al., 2001; Basei et al., 2008) might play a major role in subduction initiation (Stern and Gerya, 2018); 5) those calculations use a palinspastic incorrect pre-drift reconstruction, ignoring at least ca. 280 km of restored continental crust now stretched in the Brazilian and African passive margins (Aslanian et al., 2009); 6) the termination of the orogen in a gulf partially enclosed by continental crust implies much lower convergence rates; and 7) non-Euclidean geometry implies the diachronous along strike opening and closure of oceanic basins.
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Babinski, M., Chemale, F., Hartmann, L.A., Van Schmus, W.R., Silva, L.C. (1996) Juvenile accretion at 750–700 Ma in southern Brazil. Geology 24, 439–442.
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The São Gabriel terrane in the southern region (Fig. 1a) yielded U-Pb zircon ages of 800–860 Ma and 680–770 Ma (Babinski et al., 1996; Saalmann et al., 2005).
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Sm-Nd TDM are at 800–1,000 Ma with εNd(t) on the depleted mantle curve (up to +8, Babinski et al., 1996; Saalmann et al., 2005) and zircon εHf(t) from +14 to +8 (Cerva-Alves et al., 2020).
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Babinski, M., Chemale, F., Van Schmus, W.R., Hartmann, L.A., Silva, L.C. (1997) U-Pb and Sm-Nd geochronology of the neoproterozoic granitic-gneissic Dom Feliciano Belt, southern Brazil. Journal of South American Earth Sciences 10, 263–274.
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The Pelotas-Florianópolis-Aiguá batholith forms a multi-intrusion geological structure consisting of granite, gabbro and diorite with 87Sr/86Sri ratios of ca. 0.712, εNd of −3.6 to −22.2 and TDMNd of 1,200–2,400 Ma (Babinski et al., 1997; Koester et al., 2016).
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Basei, M.A.S., Frimmel, H.E., Nutman, A.P., Preciozzi, F. (2008) West Gondwana amalgamation based on detrital zircon ages from Neoproterozoic Ribeira and Dom Feliciano belts of South America and comparison with coeval sequences from SW Africa. Geological Society, London, Special Publications 294, 239–256.
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However, those estimates are contingent and cannot be used as hard proof against mobilistic models, because: 1) the ocean was probably fragmented in smaller sub-domains such as in the present day western Pacific and also connected to a much large Neoproterozoic oceanic system (Cordani et al., 2003) (Fig. 1b); 2) the Neoproterozoic upper mantle was warmer, leading to distinct spreading and subduction rates and dynamics (Brown, 2014); 3) intense wrench tectonics with thousands-of-km long shear zones obliterated former low angle surfaces and displaced allochthonous units far from their original position; 4) age, size and time span of an ocean have little significance in determining whether subduction is feasible or not (Hall, 2019), while lithospheric weaknesses such as magma-rich rift systems present in the orogen precursor basins (Tack et al., 2001; Basei et al., 2008) might play a major role in subduction initiation (Stern and Gerya, 2018); 5) those calculations use a palinspastic incorrect pre-drift reconstruction, ignoring at least ca. 280 km of restored continental crust now stretched in the Brazilian and African passive margins (Aslanian et al., 2009); 6) the termination of the orogen in a gulf partially enclosed by continental crust implies much lower convergence rates; and 7) non-Euclidean geometry implies the diachronous along strike opening and closure of oceanic basins.
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Basei, M.A.S., Frimmel, H.E., Campos Neto, M.C., Ganade de Araújo, C.E., Castro, N.A., Passarelli, C.R. (2018) The tectonic history of the southern Adamastor Ocean based on a correlation of the Kaoko and Dom Feliciano belts. In: Siegesmund S., Basei M., Oyhantçabal P., Oriolo S. (Eds.) Geology of Southwest Gondwana. Regional Geology Reviews. Springer, Cham., 63–85.
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Widespread Ediacaran (mainly ca. 580–630 Ma) magmatic rocks represent an expanded series of medium to high K calc-alkaline, magnesian, metaluminous, I-type tonalites to granodiorites rich in dioritic to mafic enclaves, with minor gabbro (Fig. 1a) (Tedeschi et al., 2016; Basei et al., 2018; Corrales et al., 2020).
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The original proposition of Hartnady et al. (1985) would correspond to the Marmora back-arc basin in the African counterparts, east of the Pelotas arc (Frimmel et al., 2011; Basei et al., 2018).
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Brown, M. (2014) The contribution of metamorphic petrology to understanding lithosphere evolution and geodynamics. Geoscience Frontiers 5, 553–569.
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However, those estimates are contingent and cannot be used as hard proof against mobilistic models, because: 1) the ocean was probably fragmented in smaller sub-domains such as in the present day western Pacific and also connected to a much large Neoproterozoic oceanic system (Cordani et al., 2003) (Fig. 1b); 2) the Neoproterozoic upper mantle was warmer, leading to distinct spreading and subduction rates and dynamics (Brown, 2014); 3) intense wrench tectonics with thousands-of-km long shear zones obliterated former low angle surfaces and displaced allochthonous units far from their original position; 4) age, size and time span of an ocean have little significance in determining whether subduction is feasible or not (Hall, 2019), while lithospheric weaknesses such as magma-rich rift systems present in the orogen precursor basins (Tack et al., 2001; Basei et al., 2008) might play a major role in subduction initiation (Stern and Gerya, 2018); 5) those calculations use a palinspastic incorrect pre-drift reconstruction, ignoring at least ca. 280 km of restored continental crust now stretched in the Brazilian and African passive margins (Aslanian et al., 2009); 6) the termination of the orogen in a gulf partially enclosed by continental crust implies much lower convergence rates; and 7) non-Euclidean geometry implies the diachronous along strike opening and closure of oceanic basins.
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Cavalcante, C., Fossen, H., Almeida, R P., Hollanda, M.H.B., Egydio-Silva, M. (2019) Reviewing the puzzling intracontinental termination of the Araçuaí-West Congo orogenic belt and its implications for orogenic development. Precambrian Research 322, 85–98.
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Early postulations of tectonic evolution of the Mantiqueira Province emphasised intra-continental models (e.g., Torquato and Cordani, 1981; Porada et al., 1989), an interpretation that received renewed attention in recent years (Cavalcante et al., 2019; Meira et al., 2019; Fossen et al., 2020; Konopásek et al., 2020).
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Cerva-Alves, T., Hartmann, L.A., Remus, M.V.D., Lana, C. (2020) Integrated ophiolite and arc evolution, southern Brasiliano Orogen. Precambrian Research 341, 105648.
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Sm-Nd TDM are at 800–1,000 Ma with εNd(t) on the depleted mantle curve (up to +8, Babinski et al., 1996; Saalmann et al., 2005) and zircon εHf(t) from +14 to +8 (Cerva-Alves et al., 2020).
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Cordani, U.G., Brito Neves, B.B., D’Agrella-Filho, M.S. (2003) From Rodinia to Gondwana: a review of the available evidence from South America. Gondwana Research 6, 275–283.
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The Cretaceous breakup of Gondwana in the South Atlantic region produced an asymmetric division of the Neoproterozoic Brasiliano/Pan-African Orogen (Fig. 1a,b) (Cordani et al., 2003).
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However, those estimates are contingent and cannot be used as hard proof against mobilistic models, because: 1) the ocean was probably fragmented in smaller sub-domains such as in the present day western Pacific and also connected to a much large Neoproterozoic oceanic system (Cordani et al., 2003) (Fig. 1b); 2) the Neoproterozoic upper mantle was warmer, leading to distinct spreading and subduction rates and dynamics (Brown, 2014); 3) intense wrench tectonics with thousands-of-km long shear zones obliterated former low angle surfaces and displaced allochthonous units far from their original position; 4) age, size and time span of an ocean have little significance in determining whether subduction is feasible or not (Hall, 2019), while lithospheric weaknesses such as magma-rich rift systems present in the orogen precursor basins (Tack et al., 2001; Basei et al., 2008) might play a major role in subduction initiation (Stern and Gerya, 2018); 5) those calculations use a palinspastic incorrect pre-drift reconstruction, ignoring at least ca. 280 km of restored continental crust now stretched in the Brazilian and African passive margins (Aslanian et al., 2009); 6) the termination of the orogen in a gulf partially enclosed by continental crust implies much lower convergence rates; and 7) non-Euclidean geometry implies the diachronous along strike opening and closure of oceanic basins.
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Corrales, F.F., Dussin, I.A., Heilbron, M., Bruno, H., Bersan, S., Valeriano, C.M., Pedrosa-Soares, A.C., Tedeschi, M. (2020) Coeval high Ba-Sr arc-related and OIB Neoproterozoic rocks linking pre-collisional magmatism of the Ribeira and Araçuaí orogenic belts, SE-Brazil. Precambrian Research 337, 105476.
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Widespread Ediacaran (mainly ca. 580–630 Ma) magmatic rocks represent an expanded series of medium to high K calc-alkaline, magnesian, metaluminous, I-type tonalites to granodiorites rich in dioritic to mafic enclaves, with minor gabbro (Fig. 1a) (Tedeschi et al., 2016; Basei et al., 2018; Corrales et al., 2020).
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The Rio Doce plutonic and volcanic rocks show εNd(t) of −2.9 to −13.6 with TDMNd of 1,190–2,030 Ma, 87Sr/86Sr of 0.7059–0.7165 and zircon εHf(t) of +2.3 to −11.7 (Tedeschi et al., 2016; Degler et al., 2017; Novo et al., 2018; Araújo et al., 2020; Corrales et al., 2020).
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Degler, R., Pedrosa-Soares, A., Dussin, I., Queiroga, G., Schulz, B. (2017) Contrasting provenance and timing of metamorphism from paragneisses of the Araçuaí-Ribeira orogenic system, Brazil: Hints for Western Gondwana assembly. Gondwana Research 51, 30–50.
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The Rio Doce plutonic and volcanic rocks show εNd(t) of −2.9 to −13.6 with TDMNd of 1,190–2,030 Ma, 87Sr/86Sr of 0.7059–0.7165 and zircon εHf(t) of +2.3 to −11.7 (Tedeschi et al., 2016; Degler et al., 2017; Novo et al., 2018; Araújo et al., 2020; Corrales et al., 2020).
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Fossen, H., Cavalcante, C., Konopásek, J., Meira, V.T., Almeida, R.P., Hollanda, M.H.B., Trompette, R. (2020) A critical discussion of the subduction-collision model for the Neoproterozoic Araçuaí-West Congo orogen. Precambrian Research 343, 105715.
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Early postulations of tectonic evolution of the Mantiqueira Province emphasised intra-continental models (e.g., Torquato and Cordani, 1981; Porada et al., 1989), an interpretation that received renewed attention in recent years (Cavalcante et al., 2019; Meira et al., 2019; Fossen et al., 2020; Konopásek et al., 2020).
View in article
Recently revisited models of intracontinental orogeny focused on a “space problem” for the development of an Adamastor oceanic realm based on estimates of maximum oceanic width using modern spreading and subduction rates (Fossen et al., 2020; Konopásek et al., 2020).
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Frimmel, H.E., Basei, M.S., Gaucher, C. (2011) Neoproterozoic geodynamic evolution of SW-Gondwana: a southern African perspective. International Journal of Earth Sciences 100, 323–354.
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The original proposition of Hartnady et al. (1985) would correspond to the Marmora back-arc basin in the African counterparts, east of the Pelotas arc (Frimmel et al., 2011; Basei et al., 2018).
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Hall, R. (2019) The subduction initiation stage of the Wilson cycle. Geological Society, London, Special Publications 470, 415–437.
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However, those estimates are contingent and cannot be used as hard proof against mobilistic models, because: 1) the ocean was probably fragmented in smaller sub-domains such as in the present day western Pacific and also connected to a much large Neoproterozoic oceanic system (Cordani et al., 2003) (Fig. 1b); 2) the Neoproterozoic upper mantle was warmer, leading to distinct spreading and subduction rates and dynamics (Brown, 2014); 3) intense wrench tectonics with thousands-of-km long shear zones obliterated former low angle surfaces and displaced allochthonous units far from their original position; 4) age, size and time span of an ocean have little significance in determining whether subduction is feasible or not (Hall, 2019), while lithospheric weaknesses such as magma-rich rift systems present in the orogen precursor basins (Tack et al., 2001; Basei et al., 2008) might play a major role in subduction initiation (Stern and Gerya, 2018); 5) those calculations use a palinspastic incorrect pre-drift reconstruction, ignoring at least ca. 280 km of restored continental crust now stretched in the Brazilian and African passive margins (Aslanian et al., 2009); 6) the termination of the orogen in a gulf partially enclosed by continental crust implies much lower convergence rates; and 7) non-Euclidean geometry implies the diachronous along strike opening and closure of oceanic basins.
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Hartmann, L.A., Werle, M., Michelin, C.R.L., Lana, C., Queiroga, G., Castro, M.P., Arena, K.R. (2019) Proto-Adamastor ocean crust (920 Ma) described in Brasiliano Orogen from coetaneous zircon and tourmaline. Geoscience Frontiers 10, 1623–1633.
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The 715–920 Ma MORB chemistry mafic-ultramafic assemblages in the southern sector have zircon εHf(t) up to +15 and mantle-like trace element signatures (Arena et al., 2017, 2018; Hartmann et al., 2019).
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Dravite in altered oceanic crust has typical ocean floor δ11B up to +1.8 (Hartmann et al., 2019).
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Hartnady, C., Joubert, P., Stowe, C. (1985) Proterozoic crustal evolution in southwestern Africa. Episodes 8, 236–244.
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However, a wealth of field, geochemical and geochronological data produced in recent decades progressively prompted interpretations involving distinct stages of typical Wilson cycle processes involved in the closure of the Adamastor Ocean (originally defined by Hartnady et al., 1985).
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The original proposition of Hartnady et al. (1985) would correspond to the Marmora back-arc basin in the African counterparts, east of the Pelotas arc (Frimmel et al., 2011; Basei et al., 2018).
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Heilbron, M., Valeriano, C.M., Peixoto, C., Tupinambá, M., Neubauer, F., Dussin, I., Corrales, F., Bruno, H., Lobato, M., Almeida, J.C.H., Silva, L.G.E. (2020) Neoproterozoic magmatic arc systems of the central Ribeira belt, SE-Brazil, in the context of the West-Gondwana pre-collisional history: A review. Journal of South American Earth Sciences, 102710.
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The 835–860 Ma Serra da Prata Complex of the central province has whole rock εNd(t) from +6.4 to +0.9 with TDM Nd of 860–1,200 Ma, 87Sr/86Sri < 0.7035, zircon εHf(t) from +14 to +10, and TDM Hf of 840–1,010 Ma (Peixoto et al., 2017; Heilbron et al., 2020; Santiago et al., 2020).
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Koester, E., Porcher, C. C., Pimentel, M. M., Fernandes, L.A.D., Vignol-Lelarge, M.L., Oliveira, L.D., Ramos, R.C. (2016) Further evidence of 777 Ma subduction-related continental arc magmatism in Eastern Dom Feliciano Belt, southern Brazil: the Chácara das Pedras Orthogneiss. Journal of South American Earth Sciences 68, 155–166.
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The Pelotas-Florianópolis-Aiguá batholith forms a multi-intrusion geological structure consisting of granite, gabbro and diorite with 87Sr/86Sri ratios of ca. 0.712, εNd of −3.6 to −22.2 and TDMNd of 1,200–2,400 Ma (Babinski et al., 1997; Koester et al., 2016).
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Konopásek, J., Cavalcante, C., Fossen, H., Janoušek, V. (2020) Adamastor–an ocean that never existed?. Earth-Science Reviews 205, 103201.
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Early postulations of tectonic evolution of the Mantiqueira Province emphasised intra-continental models (e.g., Torquato and Cordani, 1981; Porada et al., 1989), an interpretation that received renewed attention in recent years (Cavalcante et al., 2019; Meira et al., 2019; Fossen et al., 2020; Konopásek et al., 2020).
View in article
Recently revisited models of intracontinental orogeny focused on a “space problem” for the development of an Adamastor oceanic realm based on estimates of maximum oceanic width using modern spreading and subduction rates (Fossen et al., 2020; Konopásek et al., 2020).
View in article
Meira, V.T., Garcia‐Casco, A., Hyppolito, T., Juliani, C., Schorscher, J.H.D. (2019) Tectono‐Metamorphic Evolution of the Central Ribeira Belt, Brazil: A Case of Late Neoproterozoic Intracontinental Orogeny and Flow of Partially Molten Deep Crust During the Assembly of West Gondwana. Tectonics 38, 3182–3209.
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Early postulations of tectonic evolution of the Mantiqueira Province emphasised intra-continental models (e.g., Torquato and Cordani, 1981; Porada et al., 1989), an interpretation that received renewed attention in recent years (Cavalcante et al., 2019; Meira et al., 2019; Fossen et al., 2020; Konopásek et al., 2020).
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Novo, T.A., Pedrosa-Soares, A., Vieira, V.S., Dussin, I., Silva, L.C. (2018) The Rio Doce Group revisited: an Ediacaran arc-related volcano-sedimentary basin, Araçuaí orogen (SE Brazil). Journal of South American Earth Sciences 85, 345–361.
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The Rio Doce plutonic and volcanic rocks show εNd(t) of −2.9 to −13.6 with TDMNd of 1,190–2,030 Ma, 87Sr/86Sr of 0.7059–0.7165 and zircon εHf(t) of +2.3 to −11.7 (Tedeschi et al., 2016; Degler et al., 2017; Novo et al., 2018; Araújo et al., 2020; Corrales et al., 2020).
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Passarelli, C.R., Basei, M.A.S., Siga Jr., O., Harara, O.M.M. (2018) The Luis Alves and Curitiba terranes: continental fragments in the Adamastor Ocean. In: Siegesmund S., Basei M., Oyhantçabal P., Oriolo S. (Eds) Geology of Southwest Gondwana. Regional Geology Reviews. Springer, Cham., 189–215.
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Mafic-ultramafic rock associations in the central sector include dunite cumulates, MORB- and IAT-like gabbro, metabasic rocks with sheeted dikes, pillow lavas and chert, emplaced at ca. 630 Ma (Tassinari et al., 2001; Passarelli et al., 2018).
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Pedrosa-Soares, A., Vidal, P., Leonardos, O.H., Brito Neves, B.B. (1998) Neoproterozoic oceanic remnants in eastern Brazil: further evidence and refutation of an exclusively ensialic evolution for the Araçuaí–West Congo orogen. Geology 26, 519–522.
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Accretionary mélanges of the northern province (Fig. 1a) include MORB chemistry metabasalt, banded metadolerite, metagabbro and meta-ultramafic rocks, with εNd(t) up to + 6.3 (Pedrosa-Soares et al., 1998; Amaral et al., 2020).
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Peel, E., Sanchez-Bettucci, L., Basei, M.A.S. (2018) Geology and geochronology of Paso del Dragón Complex (northeastern Uruguay): Implications on the evolution of the Dom Feliciano Belt (Western Gondwana). Journal of South American Earth Sciences 85, 250–262.
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The southernmost ophiolites show whole rock εNd(t) up to +8.5 (Peel et al., 2018; Ramos et al., 2020) (Fig. 1a).
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Peixoto, C.A., Heilbron, M., Ragatky, D., Armstrong, R., Dantas, E., Valeriano, C.M., Simonetti, A. (2017) Tectonic evolution of the Juvenile Tonian Serra da Prata magmatic arc in the Ribeira belt, SE Brazil: Implications for early west Gondwana amalgamation. Precambrian Research 302, 221–254.
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The 835–860 Ma Serra da Prata Complex of the central province has whole rock εNd(t) from +6.4 to +0.9 with TDM Nd of 860–1,200 Ma, 87Sr/86Sri < 0.7035, zircon εHf(t) from +14 to +10, and TDM Hf of 840–1,010 Ma (Peixoto et al., 2017; Heilbron et al., 2020; Santiago et al., 2020).
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Porada, H. (1989) Pan-African rifting and orogenesis in southern to equatorial Africa and eastern Brazil. Precambrian Research 44, 103–136.
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Early postulations of tectonic evolution of the Mantiqueira Province emphasised intra-continental models (e.g., Torquato and Cordani, 1981; Porada et al., 1989), an interpretation that received renewed attention in recent years (Cavalcante et al., 2019; Meira et al., 2019; Fossen et al., 2020; Konopásek et al., 2020).
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Ramos, R.C., Koester, E., Vieira, D.T. (2020) Sm–Nd systematics of metaultramafic-mafic rocks from the Arroio Grande Ophiolite (Brazil): Insights on the evolution of the South Adamastor paleo-ocean. Geoscience Frontiers, doi: 10.1016/j.gsf.2020.02.013.
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The southernmost ophiolites show whole rock εNd(t) up to +8.5 (Peel et al., 2018; Ramos et al., 2020) (Fig. 1a).
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Raimondo, T., Hand, M., Collins, W.J. (2014) Compressional intracontinental orogens: Ancient and modern perspectives. Earth-Science Reviews 130, 128–153.
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The archetypical examples of intracontinental orogens (Raimondo et al., 2014), as proposed in the last century and recently revived, lack many of the tectonic components recognised in the last decades in the Mantiqueira Province.
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Ricardo, B.S., Faleiros, F.M., Moraes, R., Siga Jr., O., Campanha, G.A. (2020) Tectonic implications of juxtaposed high-and low-pressure metamorphic field gradient rocks in the Turvo-Cajati Formation, Curitiba Terrane, Ribeira Belt, Brazil. Precambrian Research, 105766.
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The evidence provided here suggests that the main ocean was located to the west of the arc rocks, where recently paired HP-HT metamorphic belts were described (Ricardo et al., 2020).
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Saalmann, K., Hartmann, L.A., Remus, M.V.D., Koester, E., Conceição, R.V. (2005) Sm–Nd isotope geochemistry of metamorphic volcano-sedimentary successions in the São Gabriel Block, southernmost Brazil: evidence for the existence of juvenile Neoproterozoic oceanic crust to the east of the Rio de la Plata craton. Precambrian Research 136, 159–175.
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The São Gabriel terrane in the southern region (Fig. 1a) yielded U-Pb zircon ages of 800–860 Ma and 680–770 Ma (Babinski et al., 1996; Saalmann et al., 2005).
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Sm-Nd TDM are at 800–1,000 Ma with εNd(t) on the depleted mantle curve (up to +8, Babinski et al., 1996; Saalmann et al., 2005) and zircon εHf(t) from +14 to +8 (Cerva-Alves et al., 2020).
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Santiago, R., Caxito, F.A., Pedrosa-Soares, A., Neves, M., Dantas, E. (2020) Tonian island arc remnants in the northern Ribeira orogeny of western Gondwana: The Caxixe batholith (Espírito Santo state, SE Brazil). Precambrian Research 351, 105944.
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The 835–860 Ma Serra da Prata Complex of the central province has whole rock εNd(t) from +6.4 to +0.9 with TDM Nd of 860–1,200 Ma, 87Sr/86Sri < 0.7035, zircon εHf(t) from +14 to +10, and TDM Hf of 840–1,010 Ma (Peixoto et al., 2017; Heilbron et al., 2020; Santiago et al., 2020).
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Stern, R.J., Gerya, T. (2018) Subduction initiation in nature and models: A review. Tectonophysics 746, 173–198.
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However, those estimates are contingent and cannot be used as hard proof against mobilistic models, because: 1) the ocean was probably fragmented in smaller sub-domains such as in the present day western Pacific and also connected to a much large Neoproterozoic oceanic system (Cordani et al., 2003) (Fig. 1b); 2) the Neoproterozoic upper mantle was warmer, leading to distinct spreading and subduction rates and dynamics (Brown, 2014); 3) intense wrench tectonics with thousands-of-km long shear zones obliterated former low angle surfaces and displaced allochthonous units far from their original position; 4) age, size and time span of an ocean have little significance in determining whether subduction is feasible or not (Hall, 2019), while lithospheric weaknesses such as magma-rich rift systems present in the orogen precursor basins (Tack et al., 2001; Basei et al., 2008) might play a major role in subduction initiation (Stern and Gerya, 2018); 5) those calculations use a palinspastic incorrect pre-drift reconstruction, ignoring at least ca. 280 km of restored continental crust now stretched in the Brazilian and African passive margins (Aslanian et al., 2009); 6) the termination of the orogen in a gulf partially enclosed by continental crust implies much lower convergence rates; and 7) non-Euclidean geometry implies the diachronous along strike opening and closure of oceanic basins.
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Tack, 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 Rodinia rifting at the western edge of the Congo craton. Precambrian Research 110, 277–306.
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However, those estimates are contingent and cannot be used as hard proof against mobilistic models, because: 1) the ocean was probably fragmented in smaller sub-domains such as in the present day western Pacific and also connected to a much large Neoproterozoic oceanic system (Cordani et al., 2003) (Fig. 1b); 2) the Neoproterozoic upper mantle was warmer, leading to distinct spreading and subduction rates and dynamics (Brown, 2014); 3) intense wrench tectonics with thousands-of-km long shear zones obliterated former low angle surfaces and displaced allochthonous units far from their original position; 4) age, size and time span of an ocean have little significance in determining whether subduction is feasible or not (Hall, 2019), while lithospheric weaknesses such as magma-rich rift systems present in the orogen precursor basins (Tack et al., 2001; Basei et al., 2008) might play a major role in subduction initiation (Stern and Gerya, 2018); 5) those calculations use a palinspastic incorrect pre-drift reconstruction, ignoring at least ca. 280 km of restored continental crust now stretched in the Brazilian and African passive margins (Aslanian et al., 2009); 6) the termination of the orogen in a gulf partially enclosed by continental crust implies much lower convergence rates; and 7) non-Euclidean geometry implies the diachronous along strike opening and closure of oceanic basins.
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Tassinari, C.C., Munhá, J.M., Ribeiro, A., Correia, C.T. (2001) Neoproterozoic oceans in the Ribeira Belt (southeastern Brazil): The Pirapora do Bom Jesus ophiolitic complex. Episodes, 24, 245–251.
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Mafic-ultramafic rock associations in the central sector include dunite cumulates, MORB- and IAT-like gabbro, metabasic rocks with sheeted dikes, pillow lavas and chert, emplaced at ca. 630 Ma (Tassinari et al., 2001; Passarelli et al., 2018).
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Tedeschi, M., Pedrosa-Soares, A., Dussin, I., Tassinari, C., Silva, L.C., Gonçalves, L.E., Alkmim, L., Lana, C., Figueiredo, C., Dantas E., Medeiros, S., Campos, C., Corrales, F., Heilbron, M. (2016) The Ediacaran Rio Doce magmatic arc revisited (Araçuaí-Ribeira orogenic system, SE Brazil). Journal of South American Earth Sciences 68, 167–186.
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Widespread Ediacaran (mainly ca. 580–630 Ma) magmatic rocks represent an expanded series of medium to high K calc-alkaline, magnesian, metaluminous, I-type tonalites to granodiorites rich in dioritic to mafic enclaves, with minor gabbro (Fig. 1a) (Tedeschi et al., 2016; Basei et al., 2018; Corrales et al., 2020).
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The Rio Doce plutonic and volcanic rocks show εNd(t) of −2.9 to −13.6 with TDMNd of 1,190–2,030 Ma, 87Sr/86Sr of 0.7059–0.7165 and zircon εHf(t) of +2.3 to −11.7 (Tedeschi et al., 2016; Degler et al., 2017; Novo et al., 2018; Araújo et al., 2020; Corrales et al., 2020).
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Torquato, J.R., Cordani, U.G. (1981) Brazil-Africa geological links. Earth-Science Reviews 17, 155–176.
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Early postulations of tectonic evolution of the Mantiqueira Province emphasised intra-continental models (e.g., Torquato and Cordani, 1981; Porada et al., 1989), an interpretation that received renewed attention in recent years (Cavalcante et al., 2019; Meira et al., 2019; Fossen et al., 2020; Konopásek et al., 2020).
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Tupinambá, M., Heilbron, M., Valeriano, C., Porto Jr., R., Dios, F.B., Machado, N., Silva, L.G.E., Almeida, J.C.H. (2012) Juvenile contribution of the Neoproterozoic Rio Negro magmatic arc (Ribeira Belt, Brazil): implications for western Gondwana amalgamation. Gondwana Research 21, 422–438.
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The Rio Negro Complex comprises intermediate to felsic plutonic rocks (620–790 Ma) with εNd(t) from +5 to −3 and 87Sr/86Sr < 0.705, as well as high K calc-alkaline to shoshonitic felsic rocks (605–620 Ma) with εNd(t) = −3 to −14 and 87Sr/86Sr = 0.7050–0.7100 (Tupinambá et al., 2012).
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Supplementary Information
The Supplementary Information includes:
- References for Data Sources of Figure 1
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