Delimitation of the Paranapanema Proterozoic block: A geophysical contribution

Mantovani, Marta Sílvia Maria; Quintas, Márcia Cristina Lopes; Shukowsky, Wladimir; Neves, Benjamim B. Brito

doi:10.18814/epiiugs/2005/v28i1/002

Cited by 58 publications

(78 citation statements)

References 20 publications

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“…It seems that we start to resolve different high velocity anomalies in the lithosphere of the Paraná Basin. This would strengthen the proposed model by Milani & Ramos (1998) with several cratonic blocks separated by suture zones as opposed to a unique block proposed by Cordani et al (1984) and Mantovani et al (2005).…”

Section: Resultssupporting

confidence: 80%

“…The high‐velocity anomaly under the Paraná Basin is now better defined than in previous studies (VanDecar et al 1995; Schimmel et al 2003) due to the increased amount of data. Based on our results it is possible to test the model of several cratonic blocks, separated by suture zones according to Milani & Ramos (1998), as alternative to the unique cratonic nucleus proposed by Cordani et al (1984) and Mantovani et al (2005). Fig.…”

Section: Discussionmentioning

confidence: 82%

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Upper-mantle seismic structure beneath SE and Central Brazil from P- and S-wave regional traveltime tomography

Rocha

Schimmel

Assumpção

2010

Geophysical Journal International

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S U M M A R YWe present models for the upper-mantle velocity structure beneath SE and Central Brazil using independent tomographic inversions of P-and S-wave relative arrival-time residuals (including core phases) from teleseismic earthquakes. The events were recorded by a total of 92 stations deployed through different projects, institutions and time periods during the years 1992-2004. Our results show correlations with the main tectonic structures and reveal new anomalies not yet observed in previous works. All interpretations are based on robust anomalies, which appear in the different inversions for P-and S-waves. The resolution is variable through our study volume and has been analyzed through different theoretical test inversions. High-velocity anomalies are observed in the western portion of the São Francisco Craton, supporting the hypothesis that this Craton was part of a major Neoproterozoic plate (San Franciscan Plate). Low-velocity anomalies beneath the Tocantins Province (mainly fold belts between the Amazon and São Francisco Cratons) are interpreted as due to lithospheric thinning, which is consistent with the good correlation between intraplate seismicity and lowvelocity anomalies in this region. Our results show that the basement of the Paraná Basin is formed by several blocks, separated by suture zones, according to model of Milani & Ramos. The slab of the Nazca Plate can be observed as a high-velocity anomaly beneath the Paraná Basin, between the depths of 700 and 1200 km. Further, we confirm the low-velocity anomaly in the NE area of the Paraná Basin which has been interpreted by VanDecar et al. as a fossil conduct of the Tristan da Cunha Plume related to the Paraná flood basalt eruptions during the opening of the South Atlantic.

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Section: Resultssupporting

confidence: 80%

Section: Discussionmentioning

confidence: 82%

Upper-mantle seismic structure beneath SE and Central Brazil from P- and S-wave regional traveltime tomography

Rocha

Schimmel

Assumpção

2010

Geophysical Journal International

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“…The dyke‐swarms that fed the flood basalts have been mapped in Ponta Grossa in Brazil and in a region eastward of Asunción in Paraguay (Figure 1). Despite this magmatic episode, the basin is thought to be underlain by a cratonic block on the basis of radiometric dating [ Cordani et al , 1984], Bouguer anomaly studies [ Mantovani et al , 2005b] and the high S‐velocities that have been imaged to 200 km depth [ Schimmel et al , 2003; Snoke and James , 1997].…”

Section: Tectonic Terranes Of the South American Platformmentioning

confidence: 99%

Effective elastic thickness of South America and its implications for intracontinental deformation

Pérez‐Gussinyé

Lowry

Watts

2007

Geochem Geophys Geosyst

109

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[1] The flexural rigidity or effective elastic thickness of the lithosphere, T e , primarily depends on its thermal gradient and composition. Consequently, maps of the lateral variability of T e in continents reflect their lithospheric structure. We present here a new T e map of South America generated using a compilation of satellite-derived (GRACE and CHAMP missions) and terrestrial gravity data (including EGM96 and SAGP), and a multitaper Bouguer coherence technique. Our T e maps correlate remarkably well with other proxies for lithospheric structure: areas with high T e have, in general, high lithospheric mantle shear wave velocity and low heat flow and vice versa. In this paper we focus on the T e of the stable platform. We find that old cratonic nuclei (mainly Archean and Early/Middle Proterozoic) have, in general, high T e (>70 km), while the younger Patagonian Phanerozoic terrane has much lower T e (20-30 km), suggesting that T e is related to terrane age as has already been noted in Europe. Within cratonic South America, T e variations are observed at regional scale: relatively lower T e occurs at sites that have been repeatedly reactivated throughout geological history as major sutures, rift zones, and sites of hot spot magmatism. Today, these low T e areas are surrounded by large cratonic nuclei. They concentrate most of the intracontinental seismicity and exhibit relatively high surface heat flow and low seismic velocity at 100 km depth. This implies that intracontinental deformation focuses within relatively thin, hot, and hence weak lithosphere, that cratonic interiors are strong enough to inhibit tectonism, and that the differences in lithospheric rigidity, structure, and composition between stable cratons and sites of intracontinental deformation are not transient, and may have been maintained, in some cases, for at least 500 m.y.

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“…This age together with gravity interpretation led Mantovani et al . [] to propose a cratonic lithosphere beneath the PMP. Pérez‐Gussinyé et al .…”

Section: Introductionmentioning

confidence: 98%

Density and P‐wave velocity structure beneath the Paraná Magmatic Province: Refertilization of an ancient lithospheric mantle

Chaves

Ussami

Ritsema

2016

Geochem Geophys Geosyst

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We estimate density and P‐wave velocity perturbations in the mantle beneath the southeastern South America plate from geoid anomalies and P‐wave traveltime residuals to constrain the structure of the lithosphere underneath the Paraná Magmatic Province (PMP) and conterminous geological provinces. Our analysis shows a consistent correlation between density and velocity anomalies. The P‐wave speed and density are 1% and 15 kg/m3 lower, respectively, in the upper mantle under the Late Cretaceous to Cenozoic alkaline provinces, except beneath the Goiás Alkaline Province (GAP), where density (+20 kg/m3) and velocity (+0.5%) are relatively high. Underneath the PMP, the density is higher by about 50 kg/m3 in the north and 25 kg/m3 in the south, to a depth of 250 − 300 km. These values correlate with high‐velocity perturbations of +0.5% and +0.3%, respectively. Profiles of density perturbation versus depth in the upper mantle are different for the PMP and the adjacent Archean São Francisco (SFC) and Amazonian (AC) cratons. The Paleoproterozoic PMP basement has a high‐density root. The density is relatively low in the SFC and AC lithospheres. A reduction of density is a typical characteristic of chemically depleted Archean cratons. A more fertile Proterozoic and Phanerozoic subcontinental lithospheric mantle has a higher density, as deduced from density estimates of mantle xenoliths of different ages and composition. In conjunction with Re‐Os isotopic studies of the PMP basalts, chemical and isotopic analyses of peridodite xenoliths from the GAP in the northern PMP, and electromagnetic induction experiments of the PMP lithosphere, our density and P‐wave speed models suggest that the densification of the PMP lithosphere and flood basalt generation are related to mantle refertilization. Metasomatic refertilization resulted from the introduction of asthenospheric components from the mantle wedge above Proterozoic subduction zones, which surrounded the Paraná lithosphere. The high‐density PMP lithosphere is presently gravitationally unstable and prone to delamination.

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Delimitation of the Paranapanema Proterozoic block: A geophysical contribution

Cited by 58 publications

References 20 publications

Upper-mantle seismic structure beneath SE and Central Brazil from P- and S-wave regional traveltime tomography

Upper-mantle seismic structure beneath SE and Central Brazil from P- and S-wave regional traveltime tomography

Effective elastic thickness of South America and its implications for intracontinental deformation

Density and P‐wave velocity structure beneath the Paraná Magmatic Province: Refertilization of an ancient lithospheric mantle

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