Banca de DEFESA: LEONARDO DA SILVA RIBEIRO MOCITAIBA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : LEONARDO DA SILVA RIBEIRO MOCITAIBA
DATA : 04/08/2016
HORA: 14:30
LOCAL: Auditório do Departamento de Geofísica
TÍTULO:

REGIONAL GEOPHYSICAL MAPPING OF THE MESOZOIC MAGMATISM IN THE PARNAÍBA BASIN 

PALAVRAS-CHAVES:

Parnaíba Basin; Mosquito and Sardinha formation; Airborne magnetic data; Self-organizing map; Magnetic susceptibility; Seismic sections.

PÁGINAS: 95
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
RESUMO:

The Parnaíba Basin occupies a large area in the NE portion of Brazil, covering several states. It is a Paleozoic syneclise that contains records from the formation and break-up of the Gondwana supercontinent. The basin is supported by a crystalline basement developed after the collision between the Amazonian and Brazilian platforms. During the Mesozoic break-up of Pangea megacontinent, which contributed to the opening of the Atlantic Ocean, intrusive igneous (dykes and sills) and extrusive rocks took place in the Parnaíba Basin. In the stratigraphic context, those igneous rocks were divided into two units: Early Jurassic Mosquito and Early Cretaceous Sardinha formations. The main objective of this research is regional geophysical mapping of these magmatic bodies based on aeromagnetic data and self-organizing map technique (SOM). The Matched Filter was applied in order to decompose the Total Magnetic Intensity anomalies (TMI) of the basin in their components related to magnetic sources at different depths: Deep (DMF), Intermediate (IMF), and Shallow Magnetic Fields (SMF). As the IMF anomalies mainly present contributions caused by magnetic sources at shallower depths in the upper crust, characteristics of such magmatic bodies, spectral filtering techniques (Analytic Signal Amplitude and Vertical Derivative) were applied in the IMF data in order to enhance the geophysical response of these magnetic sources, increasing the spatial resolution of the investigative method. Based on high amplitude and short wavelength anomalies, magnetic domains and lineaments were delimited in aeromagnetic maps and correlated with the possible causative bodies. Thus, the correlation of the geophysical maps with SOM solutions and the geological map allowed to propose an interpretive map with the surface distribution of magnetic anomalies associated with Mesozoic Magmatism in the Parnaíba basin. The results indicated that the Mosquito Magmatism has great occurrence at the western and southern basin edges and the Sardinha Magmatism is located at the central-eastern and northeastern parts. Magnetic susceptibility data, measured in the magmatic rocks, permitted individualizing the Mesozoic Magmatism.The Sardinha Formation displays average magnetic susceptibility of 25.2 x 10^-3 SI, about two times higher than the values of 11.46 x 10 ^-3 SI obtained to Formation Mosquito, revealing a compositional differentiation of these two magmatic events. Associations between seismic sections, magnetic data and geological map showed that the high amplitude anomalies in the Analytic Signal and TMI maps are associated with sills and dykes intruded usually within Balsas, Canindé and Serra Grande groups, and are significantly influenced by outcropping or at near-surface buried igneous rocks. Finally, the directions of the magnetic lineaments revealed that ENE-WSW and NNE-SSW oriented rifts, associated with the break-up of West Gondwana, and E-W and NE-SW structural trends, associated with Transbrasiliano Shear Zone, exercised structural control over the Mesozoic Magmatism of the Parnaíba basin.

MEMBROS DA BANCA:
Interno - 1315614 - DAVID LOPES DE CASTRO
Interno - 2042405 - MOAB PRAXEDES GOMES
Externo à Instituição - FRANCISCO JOSÉ FONSECA FERREIRA - UFPR