Sedimentation, metamorphism and granite generation in a back-arc region: Records from the Ediacaran Nova Venécia Complex (Araçuaí Orogen, Southeastern Brazil)

Richter, Fabiana; Lana, Cristiano; Stevens, Gary; Buick, Ian S.; Pedrosa-Soares, Antônio Carlos; Alkmim, Fernando Flecha de; Cutts, Kathryn

doi:10.1016/j.precamres.2015.10.012

Cited by 81 publications

(100 citation statements)

References 68 publications

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“…The precise 569 ± 6 Ma LA‐ICP‐MS concordant age obtained on sample 146 (M‐Domain II) restricts this group to the 565–575 Ma interval. This interval, as documented by various authors, represents the time of the largest production of syn‐collisional crustal melts in the Araçuaí orogen, represented by the leucogranites of the G2 Granite Supersuite (Gradim et al., ; Melo et al., ; Pedrosa‐Soares, De Campo et al., ; Peixoto et al., ; Richter et al., ; Silva, Pedrosa‐Soares, Armstrong, & Noce, ). Thus, ages of this group record the syn‐collisonal Barrovian metamorphic event in both domains.…”

Section: Discussion and Synthesismentioning

confidence: 82%

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Metamorphic record of collision and collapse in the Ediacaran‐Cambrian Araçuaí orogen, SE‐Brazil: Insights from P–T pseudosections and monazite dating

Peixoto

Alkmim

Pedrosa-Soares

et al. 2017

Journal Metamorphic Geology

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The Araçuaí orogen is the Brazilian counterpart of the Araçuaí‐West Congo orogenic system (AWCO), a component of the Ediacaran‐Cambrian orogenic network formed during the amalgamation of West Gondwana. The northwestern portion of the Araçuaí orogen is dominated by a succession of metasedimentary rocks made up of Meso‐ to Neoproterozoic rift, passive margin and syn‐orogenic sequences, locally intruded by post‐collisional granites. These sequences are involved in three distinct tectonic units, which from west to east are: the southern Espinhaço fold‐thrust system (SE‐thrust system), the normal‐sense Chapada Acauã shear zone (CASZ) and the Salinas synclinorium. Three deformation phases were documented in the region. The first two phases (D1 and D2) are characterized by contractional structures and represent the collisional development stage of the orogen. The third phase (D3) is extensional and currently viewed as a manifestation of orogenic collapse of the system. The distribution of the metamorphic mineral assemblages in the region characterizes two metamorphic domains. The M‐Domain I on the west, encompassing the SE‐thrust system and the CASZ, is marked by a syn‐collisional (syn‐D1) Barrovian‐type metamorphism with P–T conditions increasing eastwards and reaching ~8.5 kbar at ~650°C between 575 and 565 Ma. The M‐Domain II comprises the Salinas synclinorium in the hangingwall of the CASZ, and besides the greenschist facies syn‐collisional metamorphism, records mainly a Buchan‐type metamorphic event, which took place under 3–5.5 kbar and up to 640°C at c. 530 Ma. The northwestern Araçuaí orogen exhibits, thus, a paired metamorphic pattern, in which the Barrovian and Buchan‐type metamorphic domains are juxtaposed by a normal‐sense shear zone. Lithospheric thinning during the extensional collapse of the orogen promoted ascent of the geotherms and melt generation. A large volume of granites was emplaced in the high grade and anatectic core of the orogen during this stage, and heat advected from these intrusions caused the development of Buchan facies series over a relatively large area. Renewed granite plutonism, hydrothermal activities followed by progressive cooling affected the system between 530 and 490 Ma.

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Section: Discussion and Synthesismentioning

confidence: 82%

“…Metamorphic ages of c . 530 Ma were also documented on both monazite and zircon extracted from granites and paragneisses of the crystalline core of the orogen (Melo et al., ; Richter et al., ; Silva, McNaughton, Armstrong, Hartmann, & Fletcher, ; Silva et al., ).…”

Section: Discussion and Synthesismentioning

confidence: 97%

Metamorphic record of collision and collapse in the Ediacaran‐Cambrian Araçuaí orogen, SE‐Brazil: Insights from P–T pseudosections and monazite dating

Peixoto

Alkmim

Pedrosa-Soares

et al. 2017

Journal Metamorphic Geology

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“…The Eastern Domain is subdivided into the Nova Venecia complex composed of migmatites, granulites and granites (e.g. Richter et al, 2015) and into the Carlos Chagas batholith characterized by peraluminous S-type granitoids (e.g. Melo et al, 2016).…”

Section: General Background Of the Araçuaí Orogenic Beltmentioning

confidence: 99%

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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“…630 Ma. Closure of the Macaúbas basin must have started thus before 630 Ma and culminated with the abortion of the subduction system installed in its interior around 590 Ma, the age of the first generation of syn-collisonal granites, produced by melting of the basement and basin fill units (Pedrosa-Soares et al 2011a, b;Gradim et al 2014;Richter et al 2016).…”

Section: Evolutionary Synthesismentioning

confidence: 99%

“…14.2). Recent syntheses on the lithological assemblages and evolution of the crystalline core of the AWCO are provided by Gradim et al (2014), Gonçalves et al (2014Gonçalves et al ( , 2016, Richter et al (2016), and Tedeschi et al (2016). The southern limit of the Araçuaí belt is arbitrary.…”

Section: Introductionmentioning

confidence: 99%

The Araçuaí Belt

Alkmim

Kuchenbecker

Reis

et al. 2016

São Francisco Craton, Eastern Brazil

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The Araçuaí belts extends along the curved southeastern margin of the São Francisco craton between the Brazilian coast and Lat 21°S, where it merges with the Ribeira belt. It represents the external, basement-involved fold-thrust belt of the Araçuaí-West Congo confined orogen (AWCO), which formed due to the closure of the terminal branch of the Adamastor ocean during the amalgamation of West Gondwana in the Ediacaran and beginning of the Cambrian. Bounded to the east and southeast by the high grade and granitic core of the AWCO, the Araçuaí belt involves a basement assemblage older than 1.8 Ga, the 1.7-0.9 Ga rift to rift-sag successions of the Espinhaço Supergroup, the Tonian-Edicaran rift-passive margin Macaúbas Group, as well as the syn-orogenic Salinas Formation and crustal derived granitic intrusions. The Macaúbas Group, the type unit of the belt, contains a glaciomarine sequence made up of thick diamictites, sandstones and Rapitan-type banded iron formations. The units exposed along the belt were metamorphosed under greenschist to amphibolite facies conditions and affected by thrusts, reverse faults and cratonward verging folds, developed between 575 and 530 Ma. The Araçuaí orogenic front propagates into the craton interior and interacts with preexistent rift structures. This chapter describes the stratigraphic framework and overall structure of the Araçuaí belt, emphasizing the paleogeographic and tectonic significance of its sedimentary and volcanic assemblages.

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Sedimentation, metamorphism and granite generation in a back-arc region: Records from the Ediacaran Nova Venécia Complex (Araçuaí Orogen, Southeastern Brazil)

Cited by 81 publications

References 68 publications

Metamorphic record of collision and collapse in the Ediacaran‐Cambrian Araçuaí orogen, SE‐Brazil: Insights from P–T pseudosections and monazite dating

Metamorphic record of collision and collapse in the Ediacaran‐Cambrian Araçuaí orogen, SE‐Brazil: Insights from P–T pseudosections and monazite dating

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

The Araçuaí Belt

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