Definition of ultrabasic in English:


Pronunciation /ˌəltrəˈbāsik/ /ˌəltrəˈbeɪsɪk/


  • Relating to or denoting igneous rocks having a silica content less than 45 percent by weight, most of which are also ultramafic.

    ‘Major shear zones containing basic and ultrabasic igneous rocks are interpreted as suture zones.’
    Compare with ultramafic
    • ‘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.’
    • ‘Jansen also describes gabbro, diabase, ultrabasic rocks and Permian limestones in a comparable section on Naxos.’
    • ‘Their southward imbrication within the Kudi gneisses, the similar lithology and occurrence close to the Buziwan ultrabasic rocks near Kudi village may indicate they could have been part of Buziwan ophiolite.’