Geofísica

Coeval Neoproterozoic mafic dykes with a well-constrained isotopic age of 925 Ma are distributed in the North China Craton (NCC) of China and São Francisco Craton (SFC) of Brazil. Several recent studies favor the hypothesis that these two cratons were connected during 925 Ma and constituted building cratons for the supercontinent Rodinia. However, the paleo-positions of the two cratons in Rodinia have not yet been paleomagnetically resolved.

Few data are available yet to constrain the geomagnetic field palaeointensity pattern during the Precambrian in South America, due to the lack of suitable methods and materials. We report here results from a preliminary study to determine the palaeointensity of 1419 Ma rocks from Nova Guarita mafic dykes from central Amazonian Craton and 1790 Ma mafic sills from the Avanavero sills in northern Amazonian Craton. We initially tried to conduct a Thellier-type palaeointensity determination, with units returning no palaeointensity records.

The sedimentary evolution of the Bambuí