Anorthosite texture

The term anorthosite, from Frenc anorthose (term for plagioclase) was coined by Sterry Hunt. 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).

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 L'anorthosite est une roche ignée intrusive formée de 90% ou plus de feldspath plagioclase et 10% ou moins de minéraux mafiques comme le pyroxène, l'olivine, l'ilménite et la magnétite. L'anorthosite a communément une texture grenue, souvent pegmatitique. Some of the rock at this location remains strong and competent, but much of it has a brittle crumbly or chalky texture as weathering has begun the process of breaking it down into clay. 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.

2010-01-01 · Massive anorthosite has adcumulate texture comprising tightly packed cumulus plagioclase with accessory (<10 vol%) abundances of intercumulus pyroxene and Fe-Ti oxide. The mesocumulate texture that characterizes leucogabbronorite-leuconorite is defined by higher proportions of intercumulus pyroxene and Fe-Ti oxide. Quantitative texture analysis of an anorthite (polycrystalline plagioclase feldspar) has been under takenusinganoptical microscopeequippedwithauniversal stage.

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.

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.
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IU-60 (488) – Olivine basalt showing aphanitic texture.

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. 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.
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Recommended suface finishes for flooring: Polished, Silk/Leather, Honed. Weight 2700 kg/m3 . Texture investigations on geological anorthosite specimens with the triclinic plagioclase-type structure have been performed by neutron diffraction pole figure scanning.

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The texture has two major components, group I with ⊥(001 osti.gov journal article: lunar anorthosite 15415: texture, mineralogy, and metamorphic history. Texture investigations on geological anorthosite specimens with the triclinic plagioclase-type structure have been performed by neutron diffraction po… goniometry with a position sensitive detector to anorthosite (Wenket al., 1986) has created new possibilities for the texture analysis of feldspar rocks. However, Typical texture of undeformed Archean anorthosite showing megacrysts of calcic plagioclase in a mafic groundmass, Pipestone Lake, Manitoba. From Ashwal (1993, Fig. 2.2). 1980-01-01 Such textures have been quantified in a troctolite-anorthosite from the Proterozoic Lac-St-Jean anorthosite complex, Canada.