Ar-40/Ar-39 thermochronology of Paleoproterozoic granitoids of northeast Burkina Faso, West African Craton: Implications for regional tectonics

作者：Tapsoba Boukare^*; Lo Ching Hua; Wenmenga Urbain; Jahn Bor Ming; Chung Sun Lin

来源：Precambrian Research, 2013, 235: 208-229.

DOI：10.1016/j.precamres.2013.06.012

• Thermochronology
• Birimian
• Granitoids
• Burkina Faso
• West African Craton

The greenstone belts of northeast Burkina Faso in the West African Craton (WAC) comprise Birimian meta-sedimentary and mafic-ultramafic complexes that are intruded by granitoids and late dolerite dykes. The granitoid-greenstone belt assemblages underwent at least two phases of deformation that have resulted in their principal NW and NE trends.
We performed a detailed Ar-40/Ar-39 dating together with zircon U-Pb ages in order to unravel the thermo-chronological history of the studied granitoids.
Our previous zircon U-Pb data indicated that the granitoids were emplaced between 2138 /- 7 and 2181 /- 7 Ma. This period is well known for crustal growth in the WAC. The emplacement of granitoids was concomitant with D1 or the Tangaean event (2130-2170 Ma). Amphibole and micas yield two Ar-40/Ar-39 age groups; the first group (2046 /- 12-2132 /- 13 Ma) constrained the D2 deformation event, and the second group (1918 /- 24 to 1984 /- 12 Ma), constrained the D3 or Wabo-Tempelse event.
Considering closure temperatures of the isotopic systems, the U-Pb ages and the present Ar-40/Ar-39 dating results suggest that after emplacement, the granitoids cooled to 315 degrees C at ca. 2020 Ma with a mean cooling rate of 6.5 degrees C/Ma; corresponding to a mean uplift rate of 0.65 km/Ma. The additional K-feldspar Ar-40/Ar-39 data indicate a later slow cooling stage with a rate of 0.54 degrees C/Ma, corresponding to a mean uplift rate of 0.

• 出版日期2013-9