Anorthosite /ænˈɔːrθəsaɪt/ is a phaneritic, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar, with a minimal mafic component. Pyroxene, ilmenite, magnetite, and olivine are the mafic minerals most commonly present. Anorthosites are of enormous geologic interest, because it is still not fully understood how they form. Most models involve separating plagioclase crystals based on their density. Plagioclase crystals are usually less dense than magma; so

Rapakivi texture in Jack Creek rapakivi granite. Rapakivi is Finish for rotten or crumbly rock and describes the tendency of the rapakivi granite to easily weather,

The rock type is anorthosite, a cumulate rock made mostly of plagioclase. Cumulate rocks typically have the same minerals about the same size. In this case, grain textures look somewhat annealed, possibly because of deformation and annealing when it was still very hot. Stillwater Complex, Montana.

Anorthosite texture

Plane/cross-polarized light, field width is 6 mm. STW-37 When we have to compare Gabbro vs Anorthosite, the texture, color and appearance plays an important role in determining the type of rock. Gabbro is available in dark grey to black colors whereas, Anorthosite is available in black, bluish - grey, brown, green, grey, light greenish grey, pink, white colors. The texture reflects at least two episodes of shearing (followed by intense and partial recrystallization, respectively), one episode of cataclastic deformation, and one or more episodes of shattering and fragmentation. TEXTURE • Anorthosite are leucocratic, coarse- grained and hypidiomorphic. Some crystals have euhedral form, some have poorly developed faces and others have no crystal form at all.

Thus age, composition and magmatic texture distinguish Proterozoic massif-type from Archean megacrystic anorthosites. Aside from anorthosite, the dominant rock types of anorthosites massif, include leucogabbro, leuconorite and leucotroctolite, with minor gabbroic rocks.

1709 (IU-40) – Identify the phenocryst and describe the texture. IU-31 (1826) – Identify the rock and texture However, the typical garnet symplectitic textures are totally absent in BAC, unlike those present in the Sittampundi anorthosite complex [30] [41] .

A coarse-grained crystalline rock consisting mostly of calcic plagioclase (>90%, usually labradorite) with.

IU-31 (1826) – Identify the rock and texture However, the typical garnet symplectitic textures are totally absent in BAC, unlike those present in the Sittampundi anorthosite complex [30] [41] . Mafic granulites typically show granoblastic texture with sieved as well as coronal garnets, flakes of biotite, rounded grains of sphene. 2591.13 Mottled anorthosite, mottles increasing in size and frequency downwards. 2592.25 Mottled anorthosite, grading into… 2594.20 Leucogabbronorite. 2597.35 Mottled anorthosite, variable textures such as the size of mottles, orthopyroxene-clinopyroxene. textures, developed in fine-grained to medium-grained gabbro and melagabbro layers; (4) size grading, most commonly developed in megacrystic anorthosite layers; (5) "spotted" texture in which pyroxene forms equant crystals that are more resistant to weathering than the plagioclase and, consequently, appear as "spots"; and (6) variable texture The anorthosite highlands of the Moon are primary crust, formed as plagioclase crystallized out of the Moon's initial magma ocean and floated to the top; however, it is unlikely that Earth followed a similar pattern, as the Moon was a water-less system and Earth had water.

Anorthosite is a white to light gray-colored intrusive igneous rock. Major minerals of anorthosite include just feldspar. Anorthosite has a coarse-grained texture due to slow cooling underground. An information card with details on the rock formation, mineral content, characteristics, and uses is included.
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applied here to study the origin of anorthosite.
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Alkali suite anorthosites and norites are the second most common plutonic rock have equilibration temperatures of 950–1100 °C, relict igneous textures and,

Anorthosites are of enormous geologic interest, because it is still not fully understood how they form. Most models involve separating plagioclase crystals based on their density. Plagioclase crystals are usually less dense than magma; so Get to know information about Anorthosite texture and also know all about Anorthosite Color Anorthosite is typically a coarse-grained intrusive igneous rock with color varies between white, yellowish to brown, shades of gray, blush, and smoky pigment. Anorthosite is a white to light gray-colored intrusive igneous rock. Major minerals of anorthosite include just feldspar. Anorthosite has a coarse-grained texture due to slow cooling underground.

applied here to study the origin of anorthosite. the trace of the albite twin lamellae. The direction of lamination in the matrix does not wrap around the oikocrysts, as has been observed in other troctolites (compare Sept Iles Intrusion, Higgins, 1991). THE LAC-ST-JEAN ANORTHOSITE Elsewhere on this outcrop other textures are present.

Commonly, anorthosites form at the tops of modally graded layers on the scale of several meters up to 100 meters or more. Grain size (typically <1 cm) is characteristically smaller than the massif-type or Archean anorthosites, and textures vary from orthocumulates with tabular crysts of plagioclase to adcumulates having equant polygonal grains. Lunar anorthosite 15415 consists almost entirely of anorthite (homogeneous anorthite 96.6 molecule percent), with accessory diopsidic augite and traces of hypersthene, ilmenite, and a silica mineral. Here you can know more about texture of Gneiss and Anorthosite. Texture of Gneiss is Banded, Foliated, Platy whereas that of Anorthosite is Foliated, Glassy.

anorthosite (~98% plagioclase). Dixon and Papike. (1975) pictured relict “triple junction” texture between large grains of plagioclase (1 – 3 mm) with small grains .