The classification scheme for gabbroic rocks without taking into account olivine and feldspathoids. Cpx is clinopyroxene, Opx is orthopyroxene, Plag is plagioclase. Rocks that contain less than 10% plagioclase are ultramafic (pyroxenite if pyroxenes are the dominant minerals). Pyroxene is almost exclusively clinopyroxene and norite is conversely rich in orthopyroxene. Anorthosite is almost monomineralic plagioclase-rock.The classification scheme of olivine-bearing (>10%) gabbroic rocks. “Olivine” should be added to the rock name if it contains more than 10% of it. Gabbroic rock that contains almost no pyroxene is troctolite.
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Coarse-grained igneous rockOne of the three basic types of rock that also include sedimentary and metamorphic. Igneous rocks are formed by the solidification of magma and comprised predominately of silicate minerals. Based on bulk chemical analysis, igneous rocks can be grouped into four major groups based on their SiO2 content: 1. Felsic: of basaltic composition that formed at depth and is 90% plagioclaseAlso referred to as the plagioclase feldspar series. Plagioclase is a common rock-forming series of feldspar minerals containing a continuous solid solution of calcium and sodium: (Na1-x,Cax)(Alx+1,Si1-x)Si2O8 where x = 0 to 1. The Ca-rich end-member is called anorthite (pure anorthite has formula: CaAl2Si2O8) and the Na-rich end-member is albite. clinopyroxene,
The most important mineralInorganic substance that is (1) naturally occurring (but does not have a biologic or man-made origin) and formed by physical (not biological) forces with a (2) defined chemical composition of limited variation, has a (3) distinctive set of of physical properties including being a solid, and has a (4) homogeneous groups that make up this rock type are plagioclase and pyroxeneA class of silicate (SiO3) minerals that form a solid solution between iron and magnesium and can contain up to 50% calcium. Pyroxenes are important rock forming minerals and critical to understanding igneous processes. For more detailed information, please read the Pyroxene Group article found in the Meteoritics & Classification category..Plagioclase usually predominates over pyroxene.Plagioclase is sodium-calciumfeldsparAn alumino-silicate mineral containing a solid solution of calcium, sodium and potassium. Over half the Earth’s crust is composed of feldspars and due to their abundance, feldspars are used in the classification of igneous rocks. A more complete explanation can be found on the feldspar group page.. It contains more calcium than sodium in gabbro.If there is more sodium in the plagioclase, then the rock type is named diorite.Diorite is usually lighter in color and contains more amphiboles than pyroxenes.
“Gabbro” in the strict sense of the term is an intrusiveRefers to igneous rocks that crystallized underground. rock that is chiefly composed of monoclinic pyroxene (clinopyroxene, abbreviated Cpx) and plagioclase.If more than 5% of Cpx is replaced with orthorhombic pyroxene (orthopyroxeneOrthorhombic, low-Ca pyroxene common in chondrites. Its compositional range runs from all Mg-rich enstatite, MgSiO3 to Fe-rich ferrosilite, FeSiO3. These end-members form an almost complete solid solution where Mg2+ substitutes for Fe2+ up to about 90 mol. % and Ca substitutes no more than ~5 mol. % (higher Ca2+ contents occur, abbreviated Opx), the rock is named gabbronorite.If more than 95% of the pyroxene is Opx, then we have noriteIgneous rock composed of 90% plagioclase, 95% orthopyroxene (low-Ca pyroxene) and less than 10% olivine. Norite is most commonly found in the lunar (highlands) meteorites but has also been found in about a dozen diogenites, a few shergottites, and a very small number of other achondrite types. Gabbro is very.These rocks are all collectively called gabbroic rocks.
Rocks that contain more than 90% pyroxene ispyroxenite.
Gabbros form in thecrustOutermost layer of a differentiated planet, asteroid or moon, usually consisting of silicate rock and extending no more than 10s of km from the surface. The term is also applied to icy bodies, in which case it is composed of ices, frozen gases, and accumulated meteoritic material. On Earth, the. This is the magmaMolten silicate (rock) beneath the surface of a planetary body or moon. When it reaches the surface, magma is called lava. that did not break to the surface to cool as a basaltBasalt is the most common extrusive igneous rock on the terrestrial planets. For example, more than 90% of all volcanic rock on Earth is basalt. The term basalt is applied to most low viscosity dark silicate lavas, regardless of composition. Basalt is a mafic, extrusive and fine grained igneous rock.Gabbroic rocks are usually equigranular (composed of similarly sized grains).
