RT Journal Article
T1 Detrital zircon ages of Neoproterozoic sequences of the Moroccan Anti-Atlas belt
A1 Abati Gómez, Jacobo
A1 Aghzer, Abdel Mouhsine
A1 Gerdex, Axel
A1 Ennih, Nasser
AB Detrital zircon dating from Neoproterozoic successions in the Sirwa inlier of the Anti-Atlas belt in Moroccoconfirms that the maximum depositional age of the main stratigraphic groups is significantly youngerthan has been previously proposed in lithostratigraphic correlations. This can probably be extendedto the whole Anti-Atlas according to other recent data from the Saghro inlier. Although the relativestratigraphic position of the different units remains valid as published previously, a crucial implicationof the new ages is that the sequences believed to be contemporaneous with oceanic crust and islandarc formation during the rifting and break-up of the northern margin of the West African Craton (WAC),and believed to be involved in the first phases of the Pan-African orogeny, are actually late to postorogenic.The age of the main deformation associated with the collision of the oceanic- and arc-derivedterranes to the WAC, allegedly affecting the sediments of the Saghro Group, has been estimated at around663–640 Ma. However, the youngest zircon populations of sediments of the Saghro and Bou Salda Groups,obtained in this study, cluster around 620–610 Ma, constraining the maximum age of deposition. This ageof sedimentation is indistinguishable from the age of intrusive high-K calc-alkaline plutons of the AssaragSuite, suggesting a very rapid cycle of magmatism, relief formation, erosion and sedimentation in an activegeodynamic scenario. Moreover, the proportion of the 610Ma detrital zircons becomes less with respectto the Paleoproterozoic zircons at higher stratigraphic levels, suggesting that the source of young zirconswas progressively eroded and more extensive cratonic areas, that probably underlie the Neoproterozoicrocks, were exposed. We interpret these data in terms of the development of a ca. 610Ma magmaticarc, built upon WAC basement, and its progressive dismantling. This arc can be correlated with thevoluminous late Neoproterozoic (ca. 640–570 Ma) arc magmatism characteristic of the north Gondwanamargin and the peri-Gondwanan terranes. The diamictite beds that appear in the Imghi Formation of theSaghro Group have been correlated with the Sturtian glacial period ca. 700 Ma. However, zircons from onesample of these diamictites indicate that this correlation cannot be longer maintained, and instead theyshould be correlated with the Marinoan glacial period ca. 630–610 Ma, with a widespread distributionof glaciogenic deposits in West Africa. In addition, around 375 U–Pb concordant analyses obtained fromPaleoproterozoic zircons from six samples represent a statistically significant population of this area oftheWACbasement, which can be a useful database for comparison with the detrital zircon populations ofthe peri-Gondwanan terranes of Europe and North America, as the WAC margins were one of the majorsediment suppliers for these terranes.
PB Elsevier Science B.V., Amsterdam
SN 0301-9268
YR 2010
FD 2010
LK https://hdl.handle.net/20.500.14352/44188
UL https://hdl.handle.net/20.500.14352/44188
LA eng
DS Docta Complutense
RD 7 abr 2025