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Structural framework from gravity and magnetic data in the Paleo/Mesoproterozoic Arai rift-sag basin, central Brazil

Polyanna de Sousa Moro, Roberta Mary Vidotti and Elton Luiz Dantas
Structural framework from gravity and magnetic data in the Paleo/Mesoproterozoic Arai rift-sag basin, central Brazil
Geophysics (August 2018) 83 (4): B195-B207

Abstract

The Arai Basin comprises a paleo/mesoproterozoic rift-sag basin inverted in a thick-skinned regime during the Brasiliano Orogeny. Its depth to basement, geometry, and lateral extension remain unknown. We have aimed to determine this information based on geophysical/geologic data to clarify its main structures and gain an evolutional understanding. Gravity and magnetic data allowed us to delineate the rift system - its major faults and adjacent postrift sedimentary structures - over its entire length. The geophysical investigation included radial power spectrum analysis and Euler deconvolution alongside the application of edge structure enhancement filters on magnetic anomaly and matched filter grids. A 2.5D forward gravity model was generated using all results, with geophysical sources at depths of 35-42, 20.9-22.6, 11-15.6, 9.68, 8-2.3, and 0.37-0.54 km, respectively, interpreted as the Mohorovicic Discontinuity, Curie Surface, Conrad Discontinuity, granitic intrusions, basement depths, and superficial faults. The main interpreted tectonic framework of the entire area showed a preferential direction in N40E, comprising structures related to the Transbrasiliano Lineament and its reactivations. The basin magnetic signature trends N50-80E, with structures generated essentially in the Brasiliano Orogeny and those related to extensional rift faults reactivations (belonging to Sao Jorge-Alto Paraiso-Cormari, Cavalcante-Teresina, and Teresina-Nova Roma systems). These fault systems exhibit a magnetic signature at the average depth of 6 km, converging to a single fault detected up to 21.8 km. The main rift faults are in accordance with the Euler solutions and the matched filter interpretation, confirmed by mapped alluvial fans conglomerates. The current structural framework of the basin goes back to the Brasiliano Orogeny, when its sedimentary filling was limited by crustal blocks with distinct compositional, rheologic, and magnetic characteristics. These intrinsic characteristics of each block along with the resulting kinematics were responsible for delimiting the shape and depth of the basin.


ISSN: 0016-8033
EISSN: 1942-2156
Coden: GPYSA7
Serial Title: Geophysics
Serial Volume: 83
Serial Issue: 4
Title: Structural framework from gravity and magnetic data in the Paleo/Mesoproterozoic Arai rift-sag basin, central Brazil
Affiliation: Universidade de Brasilia, Instituto de Geociencias, Brasilia, Brazil
Pages: B195-B207
Published: 201808
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 50
Accession Number: 2018-090960
Categories: Structural geologyApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sect., 2 tables, sketch maps
S15°00'00" - S12°00'00", W48°30'00" - W47°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute.
Update Code: 201849
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