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40Ar/39Ar dating of 1.0–1.1 Ga magnetizations from the Sa˜o Francisco and Kalahari cratons: tectonic implications for Pan-African and Brasiliano mobile belts

Authors
Journal
Earth and Planetary Science Letters
0012-821X
Publisher
Elsevier
Publication Date
Volume
101
Identifiers
DOI: 10.1016/0012-821x(90)90165-t
Disciplines
  • Earth Science

Abstract

Abstract Paleomagnetic poles from 1.1-1.0 Ga dyke swarms in eastern Brazil (Sa˜o Francisco Craton) are compared with 1.0 Ga poles from granulites of the Namaqua Province in southern Africa (Kalahari Graton). The intrusive ages of dykes are estimated from 40Ar/ 39Ar dating of outgassed biotites from baked country rocks. The age of magnetization for the granulites is derived by combining 40Ar/ 39Ar hornblende and biotite dates. When restored to a Mesozoic pre-drift configuration the paleomagnetic poles are in crude spatial agreement but are temporally discordant. To satisfy both paleomagnetic and geochronologic constraints, a reconstruction involving separation of the Sa˜o Francisco and Kalahari cratons is required, indicating that the intervening Pan-African (Brasiliano) mobile belt may record a craton-craton collision.

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