#TERNARY DIAGRAM PYROXENE HOW TO#

Basaltic magma forms when peridotite is partially melted.

The main minerals are diopside (green), pyrope (purple) and olivine (yellowish green). Wehrlite (clinopyroxene peridotite) from Norway. Massive samples are often brought to the surface as xenoliths inside basalt. The Troodos ophiolite in Cyprus is a well-known locality where such rocks can be seen at the surface.

Layered ultramafic typically occur at the base of gabbroic intrusions. Layered peridotite is a cumulate rock formed by crystal settling from magma. Peridotite is often massive (homogeneous) just like other plutonic rocks, but it can be also layered. It is an ultramafic rock (mafic minerals make up more than 90% of the rocks composition). Other notable minerals that are often present are chromite, garnet, and plagioclase. Peridotite is a plutonic rock, it is mostly composed of visible mineral grains. A rock type with less olivine is named pyroxenite (or hornblendite if there are more amphiboles than pyroxenes). Olivine, the principal component of peridotite, makes up more than 40% of the pair olivine + pyroxene (or amphibole). This rock is relatively rare at the surface and is often altered by hydrothermal metamorphism or weathering because its constituent minerals are unstable at the weathering environment. Lherzolite is the least pretentious of them - it is a mixture of two pyroxenes and olivine 1. Harzburgite is rich in olivine and orthopyroxene but there can be only up to 5% clinopyroxene. Wehrlite contains almost no orthopyroxene but is rich in clinopyroxene and olivine. Dunite is a type of peridotite that is almost monomineralic (more than 90% of it is olivine). Ol, Opx, and Cpx represent olivine, orthopyroxene, and clinopyroxene respectively.

#TERNARY DIAGRAM PYROXENE HOW TO#

How to read this diagram? It is a typical ternary plot which are often used in geology. There are four subtypes: dunite, harzburgite, lherzolite, and wehrlite. Note that neither peridotite nor pyroxenite are single rock types. It is an important rock type because the EarthвЂ™s mantle is predominantly composed of it.ДЄ classification diagram of ultramafic rocks. (c) SociГ©tГ© franГ§aise de MinГ©ralogie et de Cristallographie, Paris, 1988.Peridotite is a dark-colored igneous rock consisting mostly of olivine and pyroxene. The baВ¬ sic principle adopted for amphibole nomenclaВ¬ ture (Leake and Winchell, 1978) is to denote principal stoichiometrics by generally well-established names, with adjectival modifiers to indicate the presence of substantial substitutions that are not essential constituents of the end-members this has been followed as far as posВ¬ sible in the pyroxene nomenclature. This formula unit corresponds to one quarter of the unit cell for the monoclinic pyroxenes. The pyroxene formula unit calculated to six oxyВ¬ gens, or to four cations (Vieten and Hamm, 1978), is essential for the classification. The classification and nomenclature of the pyВ¬ roxenes have been largely based on their crystal chemistry. These reВ¬ commendations have been approved by the Commission by a formal vote (20th May, 1987). The subcommittee on pyroxenes has, after a thorough evaluation of the group of pyroxene minerals, presented its recommendations for a new classification and nomenclature to the ComВ¬ mission on New Minerals and Mineral Names (hereafter abbreviated as C.N.M.M.N.). Non-voting Members : Kenichiro AOKI (Japan), Glauco GOTTARDI (Italy). GINZBURG (U.S.S.R.), Malcolm ROSS (U.S.A.), Friedrich A.

Nobuo MORIMOTO, Chairman Department of Geology and Mineralogy, Kyoto University, Kyoto 606, Japan.

Ternary diagram pyroxene