Signatures of continental collisions and magmatic activity in central Brazil as indicated by a magnetotelluric profile across distinct tectonic provinces

Bologna, Maurício S.; Padilha, Antônio L.; Vitorello, Ícaro; Pádua, Marcelo B.

doi:10.1016/j.precamres.2010.12.003

Cited by 39 publications

(32 citation statements)

References 51 publications

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“…SSA‐dens resolves low‐density perturbations (between −5 and −15 kg/m 3 ) for the APAP, PGA, and SMA (Figure ). Alkaline intrusion, fluid, chemical variations, and thermal anomalies may be related to these seismic anomalies [e.g., Assumpção et al ., ; Rocha et al ., ; Bologna et al ., ].…”

Section: Discussionmentioning

confidence: 99%

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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Section: Discussionmentioning

confidence: 99%

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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“…It has also proved invaluable in imaging the structure of, and understanding the processes involved in, magmatic systems, including the effects of mantle plumes (e.g. Brasse & Eydam 2008;Wannamaker et al 2008;Bologna et al 2011;Kelbert et al 2012). Examples of rifting studies include those of Hautot et al (2000), Simpson (2000) and Häuserer & Junge (2011) further south in the East African rift.…”

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confidence: 99%

Magma imaged magnetotellurically beneath an active and an inactive magmatic segment in Afar, Ethiopia

Johnson

Whaler

Hautot

et al. 2015

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This paper presents broadband magnetotelluric data collected along profiles over two magmatic segments comprising part of the subaerial Red Sea arm of the Afar triple junction. One of these segments has been active since late 2005 and the other segment is currently inactive. After robust processing and galvanic distortion analysis, we found that the data passed the twodimensional subsurface resistivity modelling criteria. Profiles across the segments had welldefined geoelectrical strike directions parallel to the local rift axes. Data from the northern end of the active segment had a more ambiguous strike oblique to the profile and rift axes, but the direction did not have a severe impact on the deduced model. All three models displayed prominent zones of low resistivity, interpreted as arising from magma and partial melt. Petrological information has been used to constrain the resistivity of the parent melt and hence to estimate the melt fractions from the bulk resistivity. The total amount of melt estimated beneath the profile crossing the active segment (c. 500 km 3 ) is approximately an order of magnitude greater than that beneath the profile crossing the currently inactive rift. This implies that the availability of magma is at least one factor affecting whether a rift segment is active.

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“…Subduction of organic graphite-bearing sediments in continental collision zones has also been suggested to explain the high-conductivity anomalies observed in the lower crust in some regions (e.g. Bologna et al, 2011). The precipitation of graphite even in small amounts proximal to the deep-seated faults and shears would significantly reduce the overall resistivity of the rock matrix.…”

Section: Precambrian Suture Zone As a Deep Crustal Fluid Reservoirmentioning

confidence: 99%

“…From broadband and long period magnetotelluric studies along a 560 km EeW profile along the Neoproterozoic suture zone in central Brazil, Bologna et al, (2011) recently investigated the continental collision signature in this region. The conductivity structures derived in their work show signatures of the past tectonomagmatic events that affected the region.…”

Section: Precambrian Suture Zone As a Deep Crustal Fluid Reservoirmentioning

confidence: 99%

“…The formation and exhumation of high grade metamorphic orogens within the Precambrian collisional sutures are considered to mark the final phase of a prolonged subduction-accretion history with the consumption of the intervening oceans, and culminating in Himalayan-style collision (e.g., Collins et al, 2007;Cawood et al, 2009;Santosh et al, 2009a, b;Santosh, 2010a, in press). During continentecontinent collision in some of the Precambrian collisional sutures, deep underthrusting of organic graphite-bearing metasedimentary rocks has been attributed as one of the causes for the observed high electrical conductivity (e.g., Bologna et al, 2011). Subduction processes also carry substantial volumes of water into the deeper portions of the Earth (e.g., Maruyama et al, 2009), which is subsequently returned through plumes and magmas.…”

Section: Introductionmentioning

confidence: 99%

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Geophysical signatures of fluids in a reactivated Precambrian collisional suture in central India

Naganjaneyulu

Santosh

2011

Geoscience Frontiers

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The Central India Tectonic Zone (CITZ) marks the trace of a major suture zone along which the south Indian and the north Indian continental blocks were assembled through subduction-accretioncollision tectonics in the Mesoproterozoic. The CITZ also witnessed the major, plume-related, late Cretaceous Deccan volcanic activity, covering substantial parts of the region with continental flood basalts and associated magmatic provinces. A number of major fault zones dissect the region, some of which are seismically active. Here we present results from gravity modeling along five regional profiles in the CITZ, and combine these results with magnetotelluric (MT) modeling results to explain the crustal architecture. The models show a resistive (more than 2000 U$m) and a normal density (2.70 g/cm 3 ) upper crust suggesting dominant tonaliteetrondhjemiteegranodiorite (TTG) composition. There is a marked correlation between both high-density (2.95 g/cm 3 ) and low-density (2.65 g/cm 3 ) regions with high conductive zones (<80 U$m) in the deep crust. We infer the presence of an interconnected grain boundary network of fluids or fluid-hosted structures, where the conductors are associated with gravity lows. Based on the conductive nature, we propose that the lower crustal rocks are fluid reservoirs, where the fluids occur as trapped phase within minerals, fluid-filled porosity, or as fluid-rich structural conduits. We envisage that substantial volume of fluids were transferred from mantle into the lower crust through the younger plume-related Deccan volcanism, as well as the reactivation, fracturing and expulsion of fluids transported to depth

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Signatures of continental collisions and magmatic activity in central Brazil as indicated by a magnetotelluric profile across distinct tectonic provinces

Cited by 39 publications

References 51 publications

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

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

Magma imaged magnetotellurically beneath an active and an inactive magmatic segment in Afar, Ethiopia

Geophysical signatures of fluids in a reactivated Precambrian collisional suture in central India

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