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Previous issue date: 2014-03-07 / A zona de transi??o do manto est? definida por duas descontinuidades s?smicas, nominalmente a 410 e 660 km de profundidade, que resultam de transforma??es de fase no mineral olivina. A topografia dessas descontinuidades fornece informa??es sobre as varia??es laterais de temperatura da zona de transi??o. Neste trabalho, foram utilizadas convers?es P-para-S teless?smicas registradas em 32 esta??es s?smicas de banda larga na Prov?ncia Borborema para determinar a espessura da zona de transi??o abaixo desta regi?o e para investigar se h? mudan?as laterais da temperatura neste intervalo de profundidade, para isso foi feito o empilhamento e a migra??o de fun??es do receptor. Na Prov?ncia Borborema, estudos geof?sicos revelaram a exist?ncia de uma anomalia de ge?ide que poderia refletir a presen?a de uma anomalia t?rmica, a qual estaria relacionada ? origem do vulcanismo intraplaca e da epirog?nese que atingiram a Prov?ncia no Cenoz?ico. V?rios modelos t?m sido propostos para explicar esses eventos, dentre eles o modelo de pluma do manto e de eventos rasos como c?lulas de convec??o de pequena escala. Os resultados deste trabalho mostram que essa anomalia t?rmica n?o atinge a profundidade da zona de transi??o do manto, visto que n?o foram identificadas varia??es significativas na espessura da zona de transi??o. Contudo foram observadas regi?es de topografia baixa para ambas as descontinuidades (410 e 660 km) que aproximadamente se sobrep?em no espa?o, sugerindo que varia??es laterais negativa nas velocidades acima de 410 km de profundidade podem existir abaixo da Prov?ncia Borborema. O que ? consistente com a estrutura de baixa densidade que seria consequ?ncia de uma altera??o t?rmica. Portanto a fonte magm?tica que teria provocado no Cenoz?ico o vulcanismo intraplaca e estaria relacionada ao soerguimento na Prov?ncia, estaria confinada acima da zona de transi??o. / The mantle transition zone is defined by two seismic discontinuities,
nominally at 410 and 660 km depth, which result from transformations in the
mineral olivine. The topography of these discontinuities provides information
about lateral temperature changes in the transition zone. In this work, P-to-S
conversions from teleseismic events recorded at 32 broadband stations in the
Borborema Province were used to determine the transition zone thickness
beneath this region and to investigate whether there are lateral temperature
changes within this depth range. For this analysis, stacking and migration of
receiver functions was performed. In the Borborema Province, geophysical
studies have revealed a geoid anomaly which could reflect the presence of a
thermal anomaly related to the origin of intraplate volcanism and uplift that
marked the evolution of the Province in the Cenozoic. Several models have
been proposed to explain these phenomena, which include those invoking the
presence of a deep-seated mantle plume and those invoking shallower sources,
such as small-scale convection cells. The results of this work show that no
thermal anomalies are present at transition zone depths, as significant
variations in the transition zone thickness were not observed. However, regions
of depressed topography for both discontinuities (410 and 660 km) that
approximately overlap in space were identified, suggesting that lower-thanaverage,
lateral variations in seismic velocity above 410 km depth may exist
below the the Borborema Province. This is consistent with the presence of a
thermally-induced, low-density body independently inferred from analysis of
geoid anomalies. Therefore, the magma source responsible for the Cenozoic
intraplate volcanism and related uplift in the Province, is likely to be confined
above the upper mantle transition zone.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/19358 |
| Date | 07 March 2014 |
| Creators | Pinheiro, Adriane Gomes |
| Contributors | 70030929482, http://lattes.cnpq.br/0012168139768170, Ferreira, Joaquim Mendes, 58310347804, http://lattes.cnpq.br/0807368274222975, Assump??o, Marcelo Sousa de, 80543855872, http://lattes.cnpq.br/2833240474723324, Casas, Jordi Juli? |
| Publisher | Universidade Federal do Rio Grande do Norte, PROGRAMA DE P?S-GRADUA??O EM GEODIN?MICA E GEOF?SICA, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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