Deep crustal structure of the Paraná Basin from receiver functions and Rayleigh‐wave dispersion: Evidence for a fragmented cratonic root

Abstract

[1] The deep crustal structure of the Paraná Basin of southern Brazil is investigated by analyzing P-and PP-wave receiver functions at 17 Brazilian Lithosphere Seismic Project stations within the basin. The study area can be described as a typical Paleozoic intracratonic basin that hosts one of the largest Large Igneous Province of the world and makes a unique setting for investigating models of basin subsidence and their interaction with mantle plumes. Our study consists of (1) an analysis of the Moho interaction phases in the receiver functions to obtain the thickness and bulk Vp/Vs ratio of the basin's underlying crust and (2) a joint inversion with Rayleigh-wave dispersion velocities from an independent tomographic study to delineate the detailed S-wave velocity variation with depth. The results of our analysis reveal that Moho depths and bulk Vp/Vs ratios (including sediments) vary between 41 and 48 km and between 1.70 and 1.76, respectively, with the largest values roughly coinciding with the basin's axis, and that S-wave velocities in the lower crust are generally below 3.8 km/s. Select sites within the basin, however, show lower crustal S-wave velocities slightly above 3.9 km/s suggestive of underplated mafic material. We show that these observations are consistent with a fragmented cratonic root under the Paraná basin that defined a zone of weakness for the initial Paleozoic subsidence of the basin and which allowed localized mafic underplating of the crust along the suture zones by Cenozoic magmatism.Citation: Julià, J., M. Assumpção, and M. P. Rocha (2008), Deep crustal structure of the Paraná Basin from receiver functions and Rayleigh-wave dispersion: Evidence for a fragmented cratonic root,

The structure of the crust and uppermost mantle beneath Madagascar

“…The radial receiver functions were grouped by backazimuth and ray parameter before the joint inversion to account for laterally varying structures (Julià et al 2008). Both high-and low-frequency receiver functions were binned into groups in which bounds in backazimuth and ray parameter were limited to maximum variations of 10…”

Modelo de velocidade sísmica de ondas P da crosta e manto superior ao longo do perfil PABBRISE, estado de São Paulo

“…Estudos regionais recentes envolvendo dados sismológicos (Julià et al, 2008;Rocha et al, 2011) favorecem a interpretação de Milani & Ramos (1998).…”

“…(Julià et al, 2008;Peixoto, 2015) sugerem diferentes compartimentos composicionais, mas como representam médias crustais e como a crosta inferior foi retrabalhada, não são ideais para a definição de um arcabouço para o embasamento. Além disso, o perfil sísmico PABBRISE não atravessa o domínio de "blocos" (ou cráton) como sugerido por Cordani et al (1984) e Milani & Ramos (1998) (ver figura 2.3, Capítulo 2), e em relação a anomalia gravimétrica utilizada para justificar a existência do Bloco Paranapanema (Quintas, 1995;Mantovani et al, 2005;Mantovani & Brito Neves, 2009), os dados sísmicos mostram que não é compensada na crosta.…”

“…Nos últimos anos, no Brasil, vêm sendo envidados esforços no sentido de utilizar métodos sísmicos (Bassini, 1986 e referências ali contidas; Soares, 2005;Soares et al, 2006;Tavares, 2014;Evain et al, 2015;Lima et al, 2015) e sismológicos (Assumpção et al, 2002;França & Assumpção, 2004;Julià et al, 2008;Rocha et al, 2011;Trindade, 2014;Azevedo et al, 2015) para mapear a estrutura profunda da crosta e manto superior e, com isso, aprimorar o entendimento da compartimentação tectônica e evolução crustal do território brasileiro.…”

Caracterização sismológica da crosta sob o perfil PABBRISE : uma aproximação por função do receptor e razão espectral H/V

“…Brasil merecem destaque os trabalhos de (Assumpção et al, 2002;França, 2003;França & Assumpção 2004;Soares, 2005;Soares et al, 2006;Julià et al, 2008, Bianchi, 2008, Trindade, 2014, Tavares, 2014.…”