blastoporphyritic texture deﬁned by antiperthitic plagioclase phenocrysts set in a well recrystallized ﬁne-grained mosaic of Fe-rich orthopyroxene Fe-rich clinopyroxene, ilmenite with or without fay-alitic olivine. The proportion of ferromagnesian minerals increases from anorthosite to ferrodiorite through leuconorites

Anorthosite is medium to coarse grained and has an adcumulate texture. It is composed of plagioclase (90%) slightly sericitized in places, slightly serpentinized orthopyroxene and clinopyroxene. Gabbro and gabbronorite are fine to medium grained, homogeneous and have a mesocumulate texture.

Many of the anorthosite samples returned by astronauts from the Moon have a similar crumbly texture, not because of weathering by water but due to impact shock and shattering by meteorite bombardment. You'll notice a range of colors here. Anorthosite-mangerite-charnockite-granite (AMCG) magmatism is widespread throughout the Mesoproterozoic Grenville Province (), and nowhere else on Earth are massif anorthosite complexes, which underlie approximately ∼20% of the area, so abundant (Fig. 1; Corriveau et al., 2007; Morisset et al., 2008). The Lac Rouvray anorthosite mass forms a part of the Lac St. Jean massif.

Anorthosite texture

Both plagioclase and olivine are 5–10 mm long. The Layered Troctolite terminates abruptly along sinuous boundaries against Massive Anorthosite, which has a texture similar to anorthositic patches in both types of troctolite. Massive anorthosite Olivine oikocrysts - plagioclase chadocryst orientations indicated schematically where visible 20 cm Fig. 2. Thus age, composition and magmatic texture distinguish Proterozoic massif-type from Archean megacrystic anorthosites.

Leur texture montre que le magma dont elles proviennent a cristallisé rapidement ou assez rapidement, Roches de la série anorthosite-norite-troctolite (ANT).

Abstract. 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 The dominant texture is ‘Nodular’ troctolite, in which amoeboid olivine oikocrysts 10–20 cm in diameter are spaced 20–30 cm apart within a matrix of anorthosite ( Woussen et al., 1988; Figs 1 and 2 ).

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

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 Anorthosite is typically a coarse-grained intrusive igneous rock with color varies between white, yellowish to brown, shades of gray, blush, and smoky pigment. Get to know information about Anorthosite texture and also know all about Anorthosite Color Anorthosite is a white to light gray-colored intrusive igneous rock.

In the Adirondack Mountains, soils on anorthositic rock tend to be stony loamy sand with classic podzol profile development usually evident.
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The name is from anorthose, an old name for triclinic feldspars. Anorthosite is often associated with gabbro. Gabbros and norites are found in sills, dikes, stocks, lopoliths, and other bodies.

3.2- Les roches des terres lunaires. Une anorthosite à structure grenue rapportée par la mission Apollo 17, on y observe, des feldspaths gris d'anorthite et des 25 Jun 2020 The zone is essentially a homoclinal, neritic layered series, but one which varies from pristine igneous cumulate textures in some places to highly.
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The textures of plagioclase crystals within large olivine oikocrysts preserve the sequence of the formation of anorthosite. Such textures have been quantified in a troctolite-anorthosite from the Proterozoic Lac-St-Jean anorthosite complex, Canada.

Most models involve separating plagioclase crystals based on their density. Plagioclase crystals are usually less dense 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 Figure 20-1a.