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Jean-Paul Liégeois
Earth Sciences
Geodynamics and mineral resources
Geodynamics and mineral resources
Publication details
Abdallah, N, Liégeois, J.P., Bert De Waele, B, Fezaa, N & Ouabadi, A. 2007. ‘The Temaguessine Fe-cordierite orbicular granite (Central Hoggar, Algeria): U-Pb SHRIMP age, petrology, origin and geodynamical consequences for the late Pan-African magmatism of the Tuareg shield’. Journal of African Earth Sciences 49: 153-178. DOI: 10.1016/j.jafrearsci.2007.08.005. I.F. 1.219.
Article in a scientific Journal / Article in a Journal
The Temaguessine high-level subcircular pluton is intrusive into the LATEA metacraton (Central Hoggar) Eburnian (2 Ga) basement and in the Pan-African (615 Ma) granitic batholiths along a major NW-SE oriented major shear zone. It is dated here (SHRIMP U-Pb on zircon) at 582 ±5 Ma. Composed of amphibole-biotite granite and biotite syenogranite, it comprises abundant enclaves: mafic magmatic enclaves, country-rock xenoliths and remarkable Fe-cordierite (#Fe= 0.87) orbicules. The orbicules have a core rich in cordierite (40%) and a leucocratic quartz-feldspar rim. They are interpreted as resulting from the incongruent melting of the meta-wacke xenoliths collapsed into the magma: the breakdown of the biotite + quartz assemblage produced the cordierite and a quartz-feldspar minimum melt that is expelled, forming the leucocratic rim. The orbicule generation occurred at T< 850° and P< 0.3 GPa. The Fe-rich character of the cordierite resulted from the Fe-rich protolith (wacke with 4% Fe203 for 72% SiO2). Strongly negative Nd (-9.6 to -11.2), Nd TDM model ages between 1.64 to 1.92 Ga, inherited zircons between 1.76 and 2.04 Ga and low to moderately high ISr (0.704 - 0.710) indicate a Rb-depleted lower continental crust source for the Temaguessine pluton; regional considerations impose however also the participation of asthenospheric material. The Temaguessine pluton, together with other high-level subcircular pluton, is considered as marking the end of the Pan-African magma generation in the LATEA metacraton, resulting from the linear delamination along mega-shear zones, allowing asthenospheric uprise and melting of the lower continental crust. This implies that the younger Taourirt granitic province (535-520 Ma) should be considered as a Cambrian intraplate anorogenic event and not as a very late Pan-African event. Keywords: Fe-cordierite; orbicule; U-Pb zircon; Pan-African; Tuareg shield