Investigating climates, environments and biology using stable isotopes

Abstract

Qualitative and quantitative integration and interpretation of magnetic, gravity and magnetotelluric data help to determine the internal architecture of the Jaibaras rift, and allow assessing the evolution of the Jaibaras Rift within the Precambrian crystalline basement of Borborema Province, NE Brazil. This was achieved by 2D joint modeling of magnetic and gravity data in five sections across the main axis of the Jaibaras Rift. Surface data, rock density measurements, depth constraints from 2D Euler deconvolution and geophysical information from previous work in the area were integrated to constrain the modeling. The magnetic and gravity profiles of the Jaibaras Rift indicate estimated source bodies at depths up to 2.5 km, showing complex configuration for the structural framework, with a set of asymmetric grabens and horsts. The 2D magnetotelluric inversion shows that the Jaibaras Rift is marked by low resistivity values, and maximum thickness of the sedimentary package up to approximately 3 km. Shallow dipping conductive material may represent either a suture zone between the Ceará Central and Médio Coreaú domains or a set of fractures due to horizontal σ1 stress in the Ceará Central Domain. The Jaibaras Rift displays a very complex internal structure, with discontinuous sequences of grabens and horsts, and a significant volume of surface and subsurface volcanic rocks. The sedimentary packages with volcanic rift sequences have variable thicknesses, from 1 to 3 km. These rock units are controlled by normal faults that developed from older discontinuities, such as the Transbrasiliano lineament.