Complex, 3D strain patterns in a synkinematic tonalite batholith from the Araçuaí Neoproterozoic orogen (Eastern Brazil): Evidence from combined magnetic and isotopic chronology studies

Mondou, Mathieu; Egydio‐Silva, Marcos; Vauchez, Alain; Raposo, María Irene Bartolomeu; Bruguier, Olivier; Oliveira, Alexandra Fernandes

doi:10.1016/j.jsg.2012.02.015

Cited by 36 publications

(52 citation statements)

References 55 publications

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“…Most previous studies of the Araçuaí belt, including those studying the anatectic domain, placed emphasis on the characterization of strain distribution and/or magmatic episodes (e.g., Pedrosa-Soares et al, 2006;Vauchez et al, 2007;Mondou et al, 2012;Cavalcante et al, 2013); only few data on the thermal conditions and partial melting during deformation are available. Preliminary pressure (P ) and temperature (T ) estimates in mylonites from the western part of the belt (e.g., Petitgirard et Published by Copernicus Publications on behalf of the European Geosciences Union.…”

Section: Introductionmentioning

confidence: 99%

Thermal conditions during deformation of partially molten crust from TitaniQ geothermometry: rheological implications for the anatectic domain of the Araçuaí belt, eastern Brazil

et al. 2014

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Abstract. During the Neoproterozoic orogeny, the middle crust of the Araçuaí belt underwent widespread partial melting. At the regional scale, this anatectic domain is characterized by a progressive rotation of the flow direction from south to north, suggesting a 3-D deformation of the anatectic middle crust. To better determine whether melt volumes present in the anatectic middle crust of the Araçuaí orogen were large enough to allow a combination of gravity-driven and convergence-driven deformation, we used the titaniumin-quartz (TitaniQ) geothermometer to estimate the crystallization temperatures of quartz grains in the anatectic rocks. When possible, we compared these estimates with thermobarometric estimates from traditional exchange geothermobarometers applied to neighboring migmatitic kinzigites. TitaniQ temperatures range from 750 to 900 • C, suggesting that quartz starts crystallizing at minimum temperatures of ≥ 800 • C. These results, combined with the bulk-rock chemical composition of diatexites, allows the estimation of a minimum of ∼ 30 % melt and a corresponding viscosity of ∼ 10 9 -10 10 Pa s. Such a minimum melt content and low viscosity are in agreement with interconnected melt networks observed in the field. Considering that these characteristics are homogeneous over a wide area, this supports the finding that the strength of the middle crust was severely weakened by extensive partial melting, making it prone to gravitydriven flow and lateral extrusion.

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Section: Introductionmentioning

confidence: 99%

Thermal conditions during deformation of partially molten crust from TitaniQ geothermometry: rheological implications for the anatectic domain of the Araçuaí belt, eastern Brazil

et al. 2014

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“…1b and c), previously investigated by Gonçalves et al (2014), Mondou et al (2012), Nalini (1997), Nalini et al (2000Nalini et al ( , 2005Nalini et al ( , 2008 and Vauchez et al (2007). The study area covers ca.…”

Section: Resultsmentioning

confidence: 99%

“…These include: the garnet-epidote bearing dikes cropping out in the Front Range, Colorado (Dawes and Evans, 1991;Evans and Vance, 1987); the Dehnow pluton, north east Iran (Samadi et al, 2014); the Bushy Point Granites, south eastern Alaska (Arth et al, 1988;Hammarstrom, 1984a, 1984b); the Jinshan Intrusion associated with the Dabie Orogenic belt, China (e.g. Xu et al, 2013) and the subject of this study, the 30,000 km 2 Neoproterozoic Cordilleran-type Galiléia Batholith, located within the Araçuaí Orogen, Brazil (Mondou et al, 2012;Nalini, 1997;Nalini et al, 2000Nalini et al, , 2005Nalini et al, , 2008Vauchez et al, 2007). Garnet and epidote-bearing assemblages have been reported throughout the Galiléia batholith but the origin of both minerals has not been accurately constrained.…”

Section: Introductionmentioning

confidence: 93%

“…Different tectono-stratigraphic schemes have been proposed to describe the architecture of this orogen. PedrosaSoares et al (2001) and Pedrosa-Soares and Wiedemann-Leonardos (2000) proposed its subdivision into external, internal and northern domains, while Mondou et al (2012) and Vauchez et al (2007) adopted another subdivision (Fig. 1b) defining a Western Domain (or Western Mylonitic Unit), a Central Domain (or Central Plutonic Unit) and an Eastern Domain (or Anatectic Unit).…”

Section: General Background Of the Araçuaí Orogenic Beltmentioning

confidence: 99%

“…Cunningham et al (1996) and Nalini et al (2008) report that the Galiléia granitoids have both intrusive and tectonic contacts with the Rio Doce metasediments. Mondou et al (2012) suggested also that intrusion was contemporaneous with pervasive deformation in the Rio Doce metasediments.…”

Section: The Rio Doce Metasedimentary Host Rocksmentioning

confidence: 99%

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Magmatic garnet in the Cordilleran-type Galiléia granitoids of the Araçuaí belt (Brazil): Evidence for crystallization in the lower crust

Narduzzi

Farina

Stevens

et al. 2017

Lithos

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Magmatic garnet, together with epidote, is a rare mineral association in cordilleran-I-type granitoids and of special petrogenetic significance. The metaluminous to slightly peraluminous (ASI = 0.97-1.07) Galiléia batholith (Brazil) is a large (ca. 30,000 km 2 ), Neoproterozoic (ca. 632-570 Ma) weakly foliated calc-alkaline granitoid body, characterized by the widespread occurrence of garnet (grossular 25-43 mol%) and epidote (pistacite 9.3-22.7 mol%). Field, petrographic and mineral chemical evidence indicates that garnet, epidote, biotite as well as white mica crystals (low-Si phengite), are magmatic. There is no difference in bulk rock major and trace element composition between the Galiléia granitoids and other garnet-free cordilleran-type granitoids worldwide. This evidence strongly suggests that the origin of the uncommon garnet + epidote parageneses is related to the conditions of magma crystallization, such as pressure, temperature and water content. Comparison between the mineral assemblages and mineral compositions from this study and those recorded in crystallization experiments on metaluminous calc-alkaline magmas, as well as within garnet-bearing metaluminous volcanic rocks and granitoids, indicates that the supersolidus coexistence of grossular-rich garnet, epidote and white mica is consistent with magma crystallization at pressures greater than 0.8 GPa (above 25 km depth) and at temperatures below 700°C, i.e. near the water saturated solidus. Furthermore, resorption textures around garnet (plagioclase ± quartz coronas) and epidote suggest that these minerals have been partially consumed prior to complete crystallization. These findings demonstrate that at 630 Ma the crust underneath the Araçuaí Orogen was already at least 25-30 km thick and relatively cool. However, this contrasts with the marked high heat flow registered from the neighbour Carlos Chagas Batholith located 50 km to the east. In fact such granitoids record granulite-facies metamorphism at the same pressure and time (ca. 570 Ma) of Galiléia granitoids crystallization. Thus, a more suitable geodynamic scenario is required in order to explain these two contrasting thermal regimes within the same orogen. Eventually, field, petrographic and mineral chemical analogies with similar garnet-bearing granitoids located in the fore-arc settings of the British Columbia subduction zone, possibly imply that the Galiléia granitoids represent "rare" garnet-and epidote-bearing metaluminous Cordilleran-Itype granites which can only form in a fore-arc setting.

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Hot Versus Cold Orogenic Behavior: Comparing the Araçuaí‐West Congo and the Caledonian Orogens

2017

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Observations and modeling show that temperature controls crustal rheology and therefore also the orogenic evolution of continent‐continent collision zones and the associated tectonic style. In order to explore the effect of temperature in a natural environment, we compare eroded sections through the unusually cold lower Paleozoic North Atlantic Caledonian (Scandian) collision zone and the very hot Brasiliano/Pan‐African Araçuaí‐West Congo orogen. A cold and stiff subducting Caledonian continental margin was able to subduct as a rather coherent unit to ultrahigh‐pressure conditions, twice as deep as the Pan‐African/Brasiliano crust that was quickly heated and softened and got involved in partial melting. Furthermore, the Caledonian collision developed large coherent thrust sheets that were transported hundreds of kilometers toward the foreland. This was never achieved in the hot Araçuaí‐West Congo orogen, where much of the tectonic stress was absorbed by the partially molten central part of the orogen through magmatic state deformation. Major mylonite zones (thrusts) such as those seen in the Caledonides are therefore less common in the Araçuaí‐West Congo orogen. Further, the deep continental subduction in the Caledonides developed a strongly asymmetric collision zone, with rapid variations in pressure and temperature. In contrast, the Araçuaí‐West Congo orogen soon developed into a more symmetric geometry due to its easily flowing hot crust, with a relatively flat base and a corresponding plateau in its upper part. Deformation of the cold Caledonian crust was controlled by plate‐tectonic stress, while gravitational forces more strongly influenced the hot Brasiliano/Pan‐African example.

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Complex, 3D strain patterns in a synkinematic tonalite batholith from the Araçuaí Neoproterozoic orogen (Eastern Brazil): Evidence from combined magnetic and isotopic chronology studies

Cited by 36 publications

References 55 publications

Thermal conditions during deformation of partially molten crust from TitaniQ geothermometry: rheological implications for the anatectic domain of the Araçuaí belt, eastern Brazil

Thermal conditions during deformation of partially molten crust from TitaniQ geothermometry: rheological implications for the anatectic domain of the Araçuaí belt, eastern Brazil

Magmatic garnet in the Cordilleran-type Galiléia granitoids of the Araçuaí belt (Brazil): Evidence for crystallization in the lower crust

Hot Versus Cold Orogenic Behavior: Comparing the Araçuaí‐West Congo and the Caledonian Orogens

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