U-Pb ages of granitoid clasts in upper Mesozoic arc-derived strata of the Vizcaino Peninsula, Baja California, Mexico

Minor but widespread granitic clasts occur in late Jurassic to early Cretaceous age volcanogenic strata of the Eugenia and Perforada formations on the Vizcaino Peninsula. Coarse-grained garnet-bearing biotite granite and xenolith-rich hornblende tonalite are the common types of clasts. Concordia modelling of U-Pb zircon data from a biotite granite clast indicates crystallization at 150(3) m.y. and a strong inherited component of Precambrian radiogenic Pb of 1340 m.y. Data from a hornblende tonalite clast indicate a slightly younger age and a small component of inherited radiogenic Pb. The apparent absence of a nearby suitable plutonic source for these clasts may reflect translation of the Vizcaino Peninsula relative to the North American craton since Aptian- Albian time and prior to the opening of the Gulf of California at 5 m.y.