Banca de DEFESA: LUANNY BÁRBARA DE MEDEIROS FERNANDES

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : LUANNY BÁRBARA DE MEDEIROS FERNANDES
DATA : 05/09/2019
HORA: 14:30
LOCAL: Auditório do LGGP I
TÍTULO:

STRUCTURAL CONTROLS AND 40Ar/39Ar GEOGRONOLOGICAL DATA OF BASIC DYKE SWARMS IN THE EASTERN PART OF PARNAÍBA BASIN, NORTHEAST BRAZIL

PALAVRAS-CHAVES:

Parnaíba Basin; Basic Dyke Swarms; Structural Analysis; Geochronology

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

Two important magmatic events related to the breakup of the Pangea supercontinent and the opening of the Atlantic Ocean are represented, in the Parnaíba Basin, by intrusive (mainly dykes and sills) and subordinate extrusive rocks belonging to the Mosquito (Early Jurassic, which includes the extrusive component) and Sardinha (Early Cretaceous) magmatic suites. In the southeastern and central-eastern regions of the basin, there are two types of basic dyke swarms, respectively (i) with a consistent NE trend and (ii) in different orientations, which were elected for geochronological dating to verify whether they have different ages or different, more complex emplacement models, thus integrating the geochronological and tectonicstructural approaches. Remote sensor products and structural field data were analyzed in these basin areas in order to define the geometry and structural control of these basic bodies. The image analysis allowed to characterize (i) a family of dominant lineaments in the NE-SW trend at the southeastern edge of the basin and (ii) three others sets in the ENE-WSW, NESW and NW-SE directions at the central-eastern region. In outcrops, these structures correspond to basalt and/or diabase dykes (besides sills) associated with fracture and fault systems recorded in the sedimentary country rocks of the basin. In the southeastern region, the NE-SW trending dyke system (Sardinha suite) was controled by extensional fractures and normal faults in the same direction, arranged adjacent to and along the basin border in this region. Such structures diagnose a NW extension, well documented in the Interior Basins of Northeast of Brazil, whose origin is related to the South Atlantic rifting process, in the Early Cretaceous. Further North, other studies confirm that, at least in part, the NE trending faults reactivated Ediacarana-Cambrian age structures, as it also occurs in the southeastern basin border. In the central eastern region, dykes with different orientations display more complex structural controls, which reactivate and/or involve different deformation events. In this region, dyke (and sill) swarms were exclusively associated with the Sardinha Suite, thus requiring to explain their different orientations. However, ages in the ranges of 133-135 Ma and 195-208 Ma, acquired by the 40Ar/39Ar method (including a pre-existing date) show that, besides the Sardinha Suite bodies, there is a higher expression of dykes and sills of the Early Jurassic Mosquito Suite, which was also be investigated with a structural approach. The emplacement of these bodies was controlled by two distinct tectonic events. It is proposed that the Mosquito Suite dykes intruded the crust along structures formed or reactivated by NNW-SSE extension, responsible for controlling the basic bodies of this suíte, quite expressive in the midwest portion of the basin. This event is related to the opening of the Central Atlantic ocean, at the transition between the Triassic and the Jurassic. On the other hand, NNW-trending dykes, which also occur in the northern portion of the basin, already in the domain of the Equatorial Margin, could involve complexities in the local stress system, such as feeder centers that radiated dykes in a multi-oriented pattern, controlled by older structures) and regional, straight swarms involving stress axis permutations or the occurrence of oblique ramps associated with dominant normal faults, features that require further studies and data acquisition.

MEMBROS DA BANCA:
Presidente - 346469 - EMANUEL FERRAZ JARDIM DE SA
Interno - 1513243 - MARCOS ANTONIO LEITE DO NASCIMENTO
Externa à Instituição - MARIA DA GUIA LIMA - SGB