Defining Lithospheric Limits with Deep Sourced Geophysics: The Case of São Francisco Craton and Borborema Province

The East Brazilian Shield is a product of the Neoproterozoic convergence and collage of rigid Archean lithospheric blocks, which stabilized at the end of the Paleoproterozoic Trans-Amazonian event (2.0 Ga). The areal extent of the São Francisco Craton is well understood by regional gravimetric surveys, but its northern limit with the Borborema Province is not so clear. The integration of gravity, magnetics and seismic velocity anomaly maps allows mapping this northern limit to the Borborema Province. Applying the vertical integration low-pass filter to satellite magnetics yields a remarkable match to the probable lithospheric suture zone. This magnetic map identifies the deep response from thinner/thicker lithospheres of Neoproterozoic mobile belts or stable cratons. One potential microcraton is the NE extension of the Borborema Province, one site of the oldest rocks in South America, a residue of the Benino-Nigerian Craton, separated from the main occurrence by the opening of the Atlantic. The Sergipana, Riacho do Pontal and Rio Preto Neoproterozoic fold-and-thrust belts mark areas of the foreland tectonism, hundreds of kilometers inside the São Francisco Craton lithospheric block. The presence of younger rocks inside the deep geophysical limits may be evidence of a large detachment of younger continental crust over the old cratonic lithosphere.