U-PB ZIRCON AND MONAZITE RESULTS FROM GRANITE AND CHARNOCKITE FROM THE MAZAGAN ESCARPMENT, OFFSHORE MOROCCO
Rocks from the Mazagan escarpment may have originated from NW Africa, or from the eastern North American margin, if left behind after the breakup of Pangea. Between ~560 Ma and the formation of Pangea, only rifting occurred along the NW African margin. The ~560 Ma granite may have Pan-African, Avalonian or Ganderian origin. The presence of a ~1.20 Ga inherited zircon and the absence of ~2.2-2.0 Ga is not characteristic for northwest Africa, though the scarcity of inherited zircon makes this interpretation ambiguous. The charnockite may have a NW African origin and that the ~1.95 Ga oldest zircon date represents its crystallization age at the end of the Eburnean orogeny. All younger analyses are then a result of metamorphic zircon growth or Pb loss, perhaps as a result of widespread mafic magmatism that occurred between ~1.95 and ~1.64 Ga. The charnockite is unlikely to be part of Laurentian Paleoproterozoic basement, because such basement is not known to contain ~560 Ma granite. However, it may represent a fragment of Ganderian or Avalonian basement, even though such basement is not exposed in the Appalachians. Nd whole-rock model ages and inherited zircon of ~1.85 Ga are common for Ganderia, and less common for Avalonia. If rocks of the Mazagan escarpment have Ganderian or Avalonian origin, then the Pangean suture zone lies on the continental shelf southeast of the Mazagan escarpment.