Ultramafic rock
Olivine in a peridotite weathering to iddingsite within a mantle xenolith Ultramafic rocks (also referred to as ultrabasic rocks , although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). The Earth's mantle is composed of ultramafic rocks. Ultrabasic is a more inclusive term that includes igneous rocks with low silica content that may not be extremely enriched in Fe and Mg, such as carbonatites and ultrapotassic igneous rocks. Contents 1 Intrusive ultramafic rocks 2 Volcanic ultramafic rocks 3 Ultrapotassic ultramafic rocks 4 Metamorphic ultramafic rocks 5 Distribution in space and time 6 Soil and regolith developed on ultramafic rock 7 See also 8 References Intrusive ultramafic rocks IUGS Classific
