Diachronic collision, slab break-off and long-term high thermal flux in the Brasiliano–Pan-African orogeny: Implications for the geodynamic evolution of the Mantiqueira Province

Santos, Telmo Bento dos; Tassinari, Colombo Celso Gaeta; Fonseca, Paulo E.

doi:10.1016/j.precamres.2014.12.018

Cited by 61 publications

(28 citation statements)

References 101 publications

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“…In both margins, domain A is represented by the Pan‐African Araçuaí orogen in East Brazil and the Congo orogen in West Africa (Tack et al, ; Wiedemann et al, ). The Pan‐African orogenic structure was reactivated by early postcollisional extension that most likely restored the crust to close to its present‐day thickness of between 35 and 40 km (Bento dos Santos et al, ) but remained stable during Mesozoic rifting and passive margin formation. While there is no documented evidence for a role of orogenic inheritance, our model predictions allow the interpretation of a domain B where crustal thicknesses decrease to ~25 km accommodated by the reactivation of orogenic structures and initial development of new‐formed extensional shear zones (Figure b) with crustal thicknesses of ~25 km.…”

Section: Discussionmentioning

confidence: 99%

The Wilson Cycle and Effects of Tectonic Structural Inheritance on Rifted Passive Margin Formation

et al. 2018

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The parallelism between older collisional belts and younger rift systems is widely known and particularly well portrayed along the Atlantic Ocean. How tectonic inherited and new‐formed shear zones control rift nucleation and the final architecture of rifted conjugate passive margins is still poorly understood. Here we present lithospheric‐scale thermo‐mechanical numerical models that self‐consistently create extensional and contractional tectonic inheritance, where prior extension and contraction are systematically varied. Our results show that (1) initial reactivation occurs along the former lithospheric suture zones; (2) upper crustal thick‐skinned basement thrusts are partially or fully reactivated depending on the amount of prior contraction and size of the orogen; (3) with a small amount of contraction, thick‐skinned thrusts are efficiently reactivated in extension and provide the template for rifted margin formation; (4) with larger amounts of contraction, thick‐skinned thrusts distal to the lithospheric suture zone do not reactivate in extension; and (5) reactivation of prior contractional shear zones dominates during the early stages of rifting, while during the final stage of margin formation new‐formed extensional shear zones dominate. Force balance analysis predicts an inverse relation between midcrustal viscosity and the maximum offset for reactivation of weak upper crustal structures. Force balance also predicts that the degree of weakening or healing of the weak suture and the thermal thinning of the necking area control at which stage suture reactivation is deactivated and extension proceeds by mantle lithosphere thermal necking. Two rifted conjugate margins with orogenic inheritance in the North and South Atlantic are used for comparison.

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Section: Discussionmentioning

confidence: 99%

The Wilson Cycle and Effects of Tectonic Structural Inheritance on Rifted Passive Margin Formation

et al. 2018

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“…The Araçuaí‐West Congo orogen is the northern part of the extensive Mantiqueira Province, which developed along the eastern margin of South America from Uruguay to central Brazil during the assembly of West Gondwana (e.g., Almeida et al, ; Bento dos Santos, Tassinari, & Fonseca, , and references therein) (Figure ). Altogether this province shows a complicated and long‐lived orogenic evolution, with an increasingly complex history of precollisional terrane accretion southward from the Araçuai, through the Ribeira and into the Dom Feliciano belt.…”

Section: The Araçuaí‐west Congo Orogenmentioning

confidence: 99%

“…In the Araçuaí‐West Congo orogen, the high temperatures, slow cooling, and excessive amount of melt in the hinterland (Figure b) require a heat source capable of maintaining a high temperature for a long time, more specifically to keep the temperature above 700°C from 600 to 480 Ma. This represents an unsolved question in the literature on the Araçuaí‐West Congo orogen, although vague references to radiogenic heat release from subducted metasediments and mantle upwelling, including subduction of a spreading ridge, slab break‐off, and upwelling of asthenospheric mantle, have been made (Bento dos Santos et al, ; Gradim et al, ; Tedeschi et al, ).…”

Section: Why So Hot? Why So Cold?mentioning

confidence: 99%

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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“…In this present work, the focus is on the Neoproterozoic Araçuaí orogen, which is the northern segment of the Ribeira-Araçuaí orogenic system formed during the Brasiliano/Pan-African Orogeny during the amalgamation of West Gondwana (Almeida et al, 1977;Bento dos Santos et al, 2015). This collisional belt experienced slow regional cooling, high temperature, and low pressure conditions (Petitgirard et al, 2009;Cavalcante et al, 2014;Moraes et al, 2015;Richter et al, 2016), where large volumes of magma were emplaced and deformed before solidification (Vauchez et al, 2007;Mondou et al, 2012;Cavalcante et al, 2014).…”

Section: I2 Objectivesmentioning

confidence: 99%

Deformation regime variations across the Neoproterozoic Araçuaí hot orogen (SE Brazil): insights from structural and magnetic fabric analyses

Angelo¹

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The Neoproterozoic Araçuaí belt of East Brazil formed during the amalgamation of Western Gondwana and holds characteristics of a hot collisional belt, involving large amount of magma, partial melting of the middle crust, and slow cooling rates. This work combines structural analysis, magnetic fabric, and geochronological studies in order to access information related to the flow of rocks, deformation history, and structural patterns associated with the behavior of this orogenic setting. Microstructural observations support that deformation of the plutonic bodies occurred in the magmatic state while the host metasedimentary and basement rocks remained in the solid-state. A detailed structural mapping integrating field and anisotropy of magnetic susceptibility (AMS) revealed four domains with contrasting flow patterns. The structural patterns from W to E are characterized by: westward thrusting orthogonal to the belt (region 1), orogen-parallel tranpression induced strain partitioning (regions 2 and 3), and orogen-parallel flow and subsidiary eastward vergence magmatic flow (region 4). Anisotropy of anhysteretic remanent magnetization (AARM) and magnetic mineralogy investigations suggest that the main carriers of the AMS are biotite and/or amphibole in paramagnetic samples (host metassediments and basement unit), and multi-domain (MD) or pseudo-single domain (PSD) magnetite grains in ferromagnetic materials (hosted in plutonic bodies). U-Pb dating of zircons from granitoids in the western arc border and central arc regions (structural regions 1, 2, and 3) reveal that magmatism occurred between 615-567 Ma. Microstructural investigations in the igneous bodies suggest that deformation occurred before complete solidification. This magmatism is associated with the main tectono-metamorphic peak attained by the orogen. To the east (structural region 4), younger bodies were emplaced in a still thermally buffered environment, but after solidification of the anatectic country rock. This late magmatism (540-480 Ma) is associated with a minor tectono-metamorphic peak, and magmatic deformation affected these bodies during that time. In the context of protracted deformation under slow cooling conditions, the composite observed fabric results from the interplay of collision-driven (thrusting and transpression strain partitioning) and gravity-driven (orogen-parallel flow) deformations, induced by the East-West convergence between the São Francisco and Congo Cratons.

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Diachronic collision, slab break-off and long-term high thermal flux in the Brasiliano–Pan-African orogeny: Implications for the geodynamic evolution of the Mantiqueira Province

Cited by 61 publications

References 101 publications

The Wilson Cycle and Effects of Tectonic Structural Inheritance on Rifted Passive Margin Formation

The Wilson Cycle and Effects of Tectonic Structural Inheritance on Rifted Passive Margin Formation

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

Deformation regime variations across the Neoproterozoic Araçuaí hot orogen (SE Brazil): insights from structural and magnetic fabric analyses

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