U–Pb zircon (TIMS and SIMS) and Sm–Nd whole-rock geochronology of the Gour Oumelalen granulitic basement, Hoggar massif, Tuareg shield, Algeria |
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Authors: | Jean Jacques Peucat Amar Drareni Louis Latouche Etienne Deloule Philippe Vidal |
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Institution: | a Géosciences Rennes, UMR-CNRS 6118, Université Rennes 1, 35042, Rennes Cedex, France;b Laboratoire de Minéralogie, CNRS FRE 2456, MNHN, 61 rue Buffon, 75005, Paris, France;c CRPG-CNRS, BP 2054501 Vandoeuvre les, Nancy Cedex, France;d CNRS, UMR 6524, Université Blaise Pascal, 5 rue Kessler, 63038, Clermont Ferrand, France |
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Abstract: | Two major granulitic units are recognized in the Gour Oumelalen area. One of the units is composed partially of Archean gneisses (Red Gneiss complex) with U–Pb zircon SIMS and TIMS ages of approximately 2.7 Ga. Although they were formed from 3.0- to 3.2-Ga-old precursors, as indicated by Nd model ages, we find no evidence of any older history (≈3.5 Ga) as suggested by previous Pb–Pb ages. The other formation (Gour Oumelalen supergroup) is a metasedimentary sequence at least partly of Paleoproterozoic age, as indicated by zircon dates of a metavolcanic rock at approximately 2.2 Ga. A later magmatic event is recorded at approximately 1.9 Ga in both units and related to coeval granulite-facies metamorphism that affected both units. Nd model ages at approximately 2.0 Ga suggest an accretion of juvenile crust formation at that time. The existence of TDM Nd model ages intermediate between 2.5 and 2.9 Ga could result from the mixing of 3.2 and 2.0-Ga-old material or may reflect separate events. |
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Keywords: | Geochronology Archaean Proterozoic Gour Oumelalen Hoggar Tuareg shield |
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