Paleomagnetic results from unmetamorphosed Mesoproterozoic mafic dikes of Salvador, northern São Francisco craton, yield either an easterly direction with high upward inclination (Dm=110.8°, Im=-79.3°, α95=8.4°, N=8, paleopole at 122.7°E, 6.4°N), or a westerly direction with high downward inclination (Dm=290.7°, Im=64.7°, α95=7.5°, N=7, paleopole at 282.6°E, 5.6°N). Additional paleomagnetic analyses on country rocks (granulites and amphibolitic dikes) yield paleomagnetic poles similar to those obtained in other metamorphic rocks from the São Francisco craton affected by the Transamazonian orogeny (2200-1900 Ma). Positive baked contact tests in two dikes, together with rock magnetic studies, supported by petrographic and radiometric analyses, indicate that the remanent directions isolated for the unmetamorphosed dikes are primary TRM's. 40Ar/39Ar step-heating analyses on biotite from a granulite sampled ∼90 cm away from the dike's contact yield an integrated age of 1021±8 Ma, whereas the plagioclase from the dike itself yields an integrated age of 1003±33 Ma, interpreted to be the time of the emplacement. Our data in conjunction with the available late Mesoproterozoic poles from the São Francisco craton allow to best constrain its APW path between 1080 and 1010 Ma.
All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology
- Ar/Ar geochronology
- Mafic dikes
- São Francisco craton