Pyroxenite


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pyroxenite

[pə′räk·sə‚nīt]
(petrology)
A heavy, dark-colored, phaneritic igneous rock composed largely of pyroxene with smaller amounts of olivine and hornblende, and formed by crystallization of gabbroic magma.

Pyroxenite

 

an ultrabasic rock composed chiefly of one or more pyroxenes. It sometimes contains small admixtures of olivine; more rarely, it contains feldspar and magnetite or titanomagnetite. The type of pyroxene and the ore minerals present in the rock form the basis for determination of the variety of pyroxenite. Thus, rocks containing bronzite are called bronzitites, while those with hypersthene are known as hypersthenites. Pyroxenites containing equal amounts of orthopyroxene and diopside are called websterites. Pyroxenites are composed of 43–53 percent SiO2, 4–10 percent AI2O3, 5–13 percent FeO + F2O3, 13–24 percent MgO, and 9–20 percent CaO.

Pyroxenites are found in areas of basic plutons, forming rather extensive belts and zones. They are often associated with alkali rocks and carbonatites, thus producing deposits of many minerals, such as apatite and rare earths. Pyroxenites sometimes occur as titanium-rich iron ores.

References in periodicals archive ?
These units are tectonically overlain by Upper Cretaceous ophiolitic rocks (harzburgites, dunites, wehrlites, pyroxenites, gabbros, and serpentinites).
The ultramaphic rocks include Dunites, Harzburgites, lherzolites, Verlites and Pyroxenite that transform into Serpentine due to the erosion under certain climatic conditions and oxidation environment.
The drilling also indicated that sulphides are regularly present in altered peridotite and pyroxenite gneisses underlying the mineralized laterite.
2) Contact zone between two units, an olivine gabbro and an olivine pyroxenite, within the intrusive complex; the outcropping veins occur along this contact on the east and south east sides of the complex.
Pakistan has enormous wealth of decorative and building stones such as granites, diorite, dunite, tanatite, pyroxenite, serpentite, gabbro, onyx, marble of different shades, recrystallized limestone, fossiliferrous limestone, sand stone, magnesium sandstones etc.
Finally, low CaO/[Al.sub.2][O.sub.3] and Mg# may be consistent with a source rich in pyroxenite (e.g.
The pyroxenite zone was shown to have platinum group values of up to 28 grams/metric ton (28 ppm) (Wagner, 1929).
Crystallization of this magma produced predominantly massive adcumulate-mesocumulate with less abundant, but regular, occurrences of(in order of relative abundance) gabbronorite-ferrodiorite segregations, mottled texture, foliation, pyroxenite aggregates, and modal layering.
(2008): Large P-T gap between Ballantrae blueschist/garnet pyroxenite and surrounding ophiolite, southern Scotland, UK: Diapiric exhumation of a Caledonian serpentinite melange.
The Aguablanca stock is a small body in the northern part of the Main Santa Olalla Pluton and consists of cumulates, mainly gabbro and norite with intercalations of pyroxenite and peridotite, that grade into amphibole-biotite diorites in the core.
Furthermore, many of the clasts within the matrix consisted of metamorphic rocks (rochas verdes) including green slate, pyroxenite, metaperidotite, metadolerite, and amphibolite.
The Jongju Complex consists of six elongated multiple intrusions, mainly alkali pyroxenite, orthoclase pyroxenite, alkali gabbro, pegmatite and lamprophyre.