- Relating to or denoting igneous rocks having a silica content less than 45 percent by weight, most of which are also ultramafic. Compare with ultramafic.More example sentences
- Major shear zones containing basic and ultrabasic igneous rocks are interpreted as suture zones.
- This convergence gave rise to southward thrusting of the Yixieke forearc in Ordovician-Early Silurian time, which then led to obduction of the Buziwan ultrabasic rocks southward over the Kudi terrane.
- On the other hand, the Kudi gneisses are imbricated with an ophiolitic slice south to Kudi, and overthrust by the Buziwan ultrabasic rocks.