A dunite is a rock in which the major constituent is the mineral olivine (Fe,Mg)2SiO4.
HerkunftThis dunite stems from a quarry 20 miles east of Bellingham in the Twin Sisters Range
- Highly depleted in most trace elements, except for transition metals.
- LILE (Rb, Sr, K, Ba): 0.07 - 17µg/g.
- HFSE (Zr, Hf, Th, U, Nb, Ta) 0.001 - 0.150 µg/g.
- Transition metals (Sc, V, Cr, Co, Ni, Cu, Zn) 3.35 - 4100 µg/g.
Ultramafic rocks are characterised by very low silica (SiO2) content of <45 m/m%. and low potassium. Their principal mineralogy is comprised of Mg and Fe-rich minerals such as pyroxenes and olivine. The Earth's mantle consists of ultramafic rocks. Another term used to describe these rocks is ultrabasic, which includes rocks, that have a low silica content, but are not high in Mg and Fe i.e. carbonatites and ultrapotassic igneous rocks.