Vertical movements at the fringe of the West African Craton: First zircon fission track datings from the Anti-Atlas Precambrian basement, Morocco

The post-Variscan uplift of the western Anti-Atlas Precambrian core is studied by zircon fission track (ZFT) analysis of ten samples of granites and schists from the Kerdous and Ifni inliers. All samples yield Carboniferous ZFT ages ranging from 358 ± 31 Ma to 319 ± 32 Ma, with nine dates younger than 338 ± 35 Ma. The weighted mean age calculated for these nine samples is 328 ± 30 Ma. These results compare with the available K–Ar datings of white mica and biotite from the same rocks or from the overlying Ediacaran-Cambrian low-grade metasediments. The fact that different systems with distinct closure temperatures yield similar ages suggests the occurrence of a short Carboniferous thermal event followed by rapid cooling. Consistent with the regional geological framework, the thermal event is assigned to the Variscan folding, being followed by rapid exhumation and cooling related to the post-folding erosion.