U-PB GEOCHRONOLOGY ON ZIRCON FROM THE AOU LI PLUTON, HAUTE-MOULOUYA AREA, MOROCCO

The Aouli Pluton consists of four units: (1) granodiorite; (2) grey gr anite; (3) pink granite - these three units constituting a spatially c ontinuous massif, and (4) muscovite granite, which is exposed in two s mall stocks somewhat removed from the other units. U-Pb ages obtained on zircon and titanite are 333 +/- 2 Ma and 319 +/- 1.5 Ma for the gra nodiorite and grey granite respectively. The 14 Ma age difference betw een the granodiorite and the grey granite supports the multiple inject ion hypothesis which was the outcome of geochemical studies [Oukemeni and Bourne, 1993]. These two rocks also contain an inherited component which has been dated at 1520 Ma in the granodiorite and at 1245 Ma an d 1804 Ma in the grey granite. The inherited components suggest the po ssible presence of Precambian crust below the Haute Moulouya. Since th e intrusion is late-to post-tectonic [Oukemeni and Bourne, 1993], the age of the granodiorite (333 +/- 2 Ma) indicates that the Hercynian de formation is pre-Visean in the Haute Moulouya area, and, by extension, throughout the eastern meseta region.