How do you identify harzburgite?
Unserpentinized harzburgite is a dark olivegreen, coarse-grained rock weathering red-brown on the surface. The orthopyroxene tends to resist weathering and serpentinization and forms rough projections on weathered surfaces. The rough surface and darker color serve to distinguish harzburgite from dunite in the field.
How is harzburgite formed?
Harzburgite typically forms by the extraction of partial melts from the more pyroxene-rich peridotite called lherzolite. The molten magma extracted from harzburgite may then erupt on the surface as basalt.
Where is pyroxenite found?
Where is the Pyroxenite Located. 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 Zimbabwe.
What is Orthopyroxene made of?
In Earth’s crust, pyroxenes are found in a wide range of igneous and metamorphic rocks. They are most abundant in the dark-colored igneous rocks, such as basalt and gabbro, that comprise most of the oceanic crust….
| Physical Properties of Pyroxenes | |
|---|---|
| Chemical Classification | Silicate |
| Specific Gravity | 3 to 4 |
What minerals are in harzburgite?
Named for occurrences in the Harz Mountains of Germany, a harzburgite is an ultrabasic igneous rock dominated by essential olivine and orthopyroxene with or without small amounts of clinopyroxene. Accessory minerals include plagioclase, spinel, garnet, ilmenite, chromite and magnetite.
Where is harzburgite formed?
Harzburgite is formed in the mantle when part of the peridotitic rock melts. This melt has basaltic composition and moves upward (melt is less dense than solid rock).
What is pyroxenite used for?
Pyroxenite is used as a flux in sintering and also in iron and steel industry. The magnesium silicates do not call for calcination (unlike the carbonates) and thus lowers energy requirement in the blast furnace.
What minerals are orthopyroxene?
Aside from olivine, magnesium-rich (less than 30 percent iron) orthopyroxene is the commonest silicate in meteorites; it is a major constituent of most chondrites and an important component of mesosiderites and calcium-poor achondrites….orthopyroxene.
| enstatite | 0 to 50% Fe |
|---|---|
| ferrosilite | 50 to 100% Fe |
Where is Harzburgite formed?
How are komatiites formed?
Komatiites are considered to have been formed by high degrees of partial melting, usually greater than 50%, and hence have high MgO with low K2O and other incompatible elements.
What is the composition of harzburgite?
Compared with pyrolite, harzburgite is generally lower in alumina and calcia but higher in magnesia. The starting material used by Irifune and Ringwood [ 1987b ], a “harzburgite minus 82 wt % olivine” composition consisting mainly of enstatite with minor amount of spinel (MgAl 2 O 4 ), is also shown in Table 1 for comparison.
What are the phase relations of harzburgite?
Learn more. [1] Phase relations in harzburgite have been determined between 14 and 24 GPa and 1473 and 1673 K. At 1673 K, harzburgite transformed to wadsleyite + garnet + clinopyroxene below 19 GPa and decomposed into an assemblage of ringwoodite + garnet + stishovite above 20 GPa.
What is the density of the harzburgite layer in the MTZ?
[18] For various thicknesses from 20 to 80 km, the harzburgite layer is denser in the MTZ until ~660 km depth owing to combined effects of composition, thermal, and phase relations.
How much clinopyroxene is in harzburgite?
So, harzburgite may contain only small amounts of clinopyroxene and at least 40% (but no more than 90) of it is olivine1. Fresh rock is dark green, but its components pyroxene and especially olivine are easily hydrothermally altered or weathered.