The Tichka Massif,Morocco—an example of contemporaneous acidic and basic plutonism

The Tichka Massif is a shallowly emplaced, domal intrusion that has produced a thermal aurole in surrounding rocks. The interior of the massif consists of a series of leucocratic granitic, tear-shaped pods sorrounded by dioritic rocks that range in composition from gabbro to granodiorite. The orientation of the pods has a strong vertical component. Flow foliation is well-developed in the rocks that surround the pods, whereas foliation is poorly developed in the granite pods. Dikes of andesite emanate from dioritic rocks and crosscut the granite pods. These rock relationships indicate that a highly viscous granitic liquid (pods) coexisted with a less viscous, denser dioritic liquid. Differences in viscosities of the two magmas and low diffusion rates in the granite magma prevented mixing.