What is a pyroxenite rock?
A pyroxenite is an ultramafic plutonic rock consisting of ≫60% pyroxene (either clino- or orthopyroxene, or both). Other phases include olivine, hornblende, micas, garnet, feldspar, spinel, ilmenite, and sulfides. They have a gradational relationship with peridotites.
What is dunite rock?
dunite, light yellowish green, intrusive igneous ultramafic rock that is composed almost entirely of olivine. It is a common rock in Earth’s upper mantle. Occurrences include Dun Mountain, New Zealand, from which the rock takes its name; the Bushveld Igneous Complex, South Africa; and Frostviken, Jämtland, Sweden.
Where is Websterite found?
Abstract. An unusual quartz-bearing orthopyroxene-rich websterite xenolith has been found in an alkali basaltic tuff at Szigliget, Bakony–Balaton Highland Volcanic Field (BBHVF), western Hungary.
Where can pyroxenite be found?
Distribution. They frequently occur in the form of dikes or segregations in gabbro and peridotite: in Shetland, Cortland on the Hudson River, North Carolina (websterite), Baltimore, New Zealand, and in Saxony. They are also found in the Bushveld Igneous Complex in South Africa and The Great Dyke in Zimbabwe.
What is special about dunite?
Dunite is an ultramafic plutonic rock that is composed almost exclusively of olivine. “Ultramafic” means that mafic minerals form more than 90% on the rocks composition. Peridotite that contains more than 90% olivine have a special name, they are called dunite (named in 1864 after Dun mountain in New Zealand).
What type of rock is Websterite?
ultramafic igneous rock
Websterite is ultramafic igneous rock that consists of roughly equal proportions of orthopyroxene and clinopyroxene. It is a type of pyroxenite. Websterite is named after the town Webster in North Carolina.
What type of rock is pyroxenite?
Pyroxenite is an ultramafic plutonic igneous rock. Ultramafic means that more than 90% of the rock is composed of magnesium- and iron-rich minerals like pyroxenes, amphiboles, and olivine. In pyroxenite the dominant mafic mineral is a pyroxene. Pyroxenite may contain up to 40% olivine.
What is the difference between pyroxenite and hornblendite?
In pyroxenite the dominant mafic mineral is a pyroxene. Pyroxenite may contain up to 40% olivine. More than that means that the rock is peridotite. If felsic minerals like feldspars constitute more than 10% of the rock, it is melanocratic gabbro. Hornblendite is a similar igneous rock, but it is composed of amphiboles instead of pyroxenes.
What are pyroxenes and why are they important?
Pyroxenes are an important and abundant group of rock-forming silicate minerals that vary in composition.
What are orthopyroxenes in pyroxenites?
Orthopyroxenes are also very common in pyroxenites. They may be recognizable by brown sub-metallic luster (crystals in the lower left), but in many cases orthopyroxenes and clinopyroxenes are indistinguishable in hand sample. Kemi, Finland (host rock of chromite).