Where is Harzburgite formed?
Harzburgite is a common mantle xenolith within mantle-derived magmas and within the upper portions of the mantle sequence of ophiolites. Harzburgite can also form as cumulates within layered intrusions. Harzburgite.
Is Harzburgite intrusive or extrusive?
The name is from the French name for olivine, péridot. HARZBURGITE – Intrusive igneous, plutonic. Harzburgite is a type of peridotite in which the major minerals are orthopyroxene (generally near enstatite) and Mg-rich olivine. In the IUGS classification M > 90%, ol/(ol+opx+cpx) = 40-90, and cpx/(ol+opx+cpx) < 5%.
How dunite is formed?
Dunite occurs in layered, gabbroic igneous complexes (see gabbro). It probably forms from the accumulation of dense, early crystallizing grains of olivine that sink to the bottom of low silica magma. Intrusions of dunite form sills or dikes. Some dunite has been altered to form serpentine.
What is lherzolite used for?
As a sample of mantle material, lherzolite approximates in composition to pyrolite—the hypothetical starting material for the genesis of basic and ultramafic magmas—and is considered to represent “fertile,” or nearly pristine mantle material (Morse, 1980).
Where are Ophiolites found?
Ophiolites have been found in Cyprus, New Guinea, Newfoundland, California, and Oman. The Samail ophiolite in southeastern Oman has probably been studied in the greatest detail. The rocks probably formed in the Cretaceous not far from the what is now the Persian Gulf.
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.
What is the meaning of lherzolite?
Lherzolite is a type of ultramafic igneous rock. It is a coarse-grained rock consisting of 40 to 90% olivine along with significant orthopyroxene and lesser amounts of calcic chromium-rich clinopyroxene. Garnet lherzolite is a major constituent of the Earth’s upper mantle (extending to ~300 km depth).
How are Ophiolites formed?
ultramafic rocks are known as ophiolites. Many geologists believe that ophiolites formed at oceanic ridges were emplaced by tectonic forces at convergent plate boundaries and then became exposed in highly deformed orogenic (mountain) belts.
What kind of rock is the harzburgite made of?
Harzburgite, an ultramafic, igneous rock, is a variety of peridotite consisting mostly of the two minerals, olivine and low-calcium (Ca) pyroxene (enstatite); it is named for occurrences in the Harz Mountains of Germany.
Where can harzburgite be found on the Earth?
Cumulate harzburgite is found in some large layered igneous intrusions. At the Earth’s surface, basaltic magmas typically crystallize the minerals: olivine, plagioclase, and augite (a high-Ca pyroxene); low-Ca pyroxenes can only co-exist with olivine at low pressure in magma that is high in both MgO and SiO 2 ( boninites ).
Which is an example of an ophiolite with harzburgite?
Examples of ophiolites with extensive harzburgite include the Troodos Ophiolite in Cyprus, the Semail Ophiolite in Oman, the Coast Range ophiolites of California, and the Bay of Islands Ophiolite in Newfoundland. Harzburgite may also be found in some Alpine peridotite massifs that consist mostly of lherzolite.
Where can you find garnet-bearing harzburgite pipes?
Garnet-bearing harzburgite is found as xenoliths in some kimberlite pipes, which are found almost exclusively in ancient continental cratons of Archean or Paleoproterozoic age. The mantle lithosphere under these cratons is particularly thick (up to 200 km or more) and cool.