Sagna I., Quidelleur X., Dioh E., Gillot P. Y., Lefevre J. C., Baratoux Lenka, Diallo D. P. (2021). Proterozoic magmatic events recorded in Ar-40/Ar-39 data from the northern part of the Kedougou Kenieba Inlier (eastern Senegal). Journal of African Earth Sciences, 175, 104109 [8 p.]. ISSN 1464-343X.
Titre du document
Proterozoic magmatic events recorded in Ar-40/Ar-39 data from the northern part of the Kedougou Kenieba Inlier (eastern Senegal)
We present a thermal history of the Kedougou Kenieba Inlier (eastern Senegal), the western-central outcropping part of the West African Craton, based on Ar-40/Ar-39 analyses performed on hornblende, biotite, and K-feldspar minerals from Paleoproterozoic plutonic rocks. Ar-40/Ar-39 age spectra obtained for hornblendes and biotites range between 2055 +/- 26 and 2028 +/- 28 Ma, in very good consistency. They suggest that magmatism in the Kedougou Kenieba Inlier happened at the end of the Eburnean Orogeny (2.25-2.00 Ga). Taking into account previous zircon U-Pb ages, these new results imply that initial cooling from magmatic temperature to about 300 degrees C (biotite closure temperature) occurred rapidly, and that these rocks did not experience any subsequent reheating event above 300 degrees C. On the other hand, Ar-40/Ar-39 age spectra obtained on K-feldspars display strongly disturbed patterns revealing that these minerals experienced argon loss due to re-heating events. Altogether, these data constrain a thermal history for the studied area involving two thermal events with temperatures around 275 and 225 degrees C, at about 1750 and 1500 Ma, respectively. These thermal events, previously inferred from U-Pb ages of intruding mafic dykes, can be related to aborted attempts of continental breakup, as the West African Craton remained attached to Baltica and Amazonia cratons during the 1.8-1.3 Ga interval.
Plan de classement
Géologie et formations superficielles [064]
;
Géophysique interne [066]
