anorthite. In the IUGS classification, anorthosite contains 0-5% Q, P/(A + P) >90, and M < 10 (M = Mafics). 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. The


Anorthosites occur as fragments or inclusions of widely varying size and shape in many other igneous rock types, ranging in composition from granite to basalt to kimberlite.

Olivine, amphibole, ilmenite, magnetite, and spinel are also sometimes present. The term anorthosite, from Frenc anorthose (term for plagioclase) was coined by Sterry Hunt. Many anorthosite outcrops are transected by thin veins and stringers of quartz and feldspar, manifesting incipient disaggregation by the granitic protolith to the host quartzofeldspathic gneiss. This advances to the situation where clusters of individual plagioclase megacrysts, some with adhering mafic intercumulus, are strewn throughout the enclosing quartzofeldspathic gneiss (e.g., Fig. 18.8A ). ANORTHOSITE - Intrusive igneous, plutonic. This rock is composed of calcic plagioclase with less than 10% ferro-magnesium minerals.

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Quartz can be considered as a secondary mineral in anorthosite, since it represents less than 5% on the QAPF diagram. Anorthite is the calcic end member of the plagioclase feldspar series. In thin section, plagioclase feldspar grains often look like they’re sprinkled with dirt (PPL) or tiny confetti (XPL). You can find the explanation on the plagioclase feldspar page. Anorthite weathers quite readily, so it’s not terribly abundant on Earth.

Within and adjacent to the intrusion, thin to moderately of the Beardmore-Geraldton belt covered the Hercules project area. Anorthosite. 4F.

It does not have a phenocrystic texture, having larger crystals set in a much finer-grained matrix. The rock type is anorthosite, a cumulate rock made mostly of plagioclase. Cumulate rocks typically have the same minerals about the same size.

Thin section slides are precisely ground to a thickness of 0.03 mm across the entire specimen area. Mineral and rock thin sections are mounted on 27 x 46 mm microscope slides, and protected by a glass coverslip. All thin section slides are labeled for reference.

Cell Dimensions: a = 8.177, b = 12.877, c = 14.169, Z = 8; alpha = 93.166°, beta = 115.85°, gamma = 91.216° V = 1,340.29 Den (Calc)= 2.75. Crystal System: Triclinic - Pinacoidal H-M Symbol ( 1) Space Group: P 1 ,I 1. X Ray Diffraction: thin section. Streak: White. Luster: Vitreous. Optical Class: Biaxial ({).

Anorthosite thin section

All thin section slides are labeled for reference. So, take a look at the thin section pictures for the three lunar basalts below, and give these three rocks textural names! Lunar Basalt 12002, Apollo 12. Lunar Basalt 12005, Apollo 12. Lunar Basalt 70017, Apollo 17. Question 2: Intersertal and Intergranular textures occur on the Earth in Mid Ocean Ridge Basalts, which are erupted on the bottom of the sea Left: Zircon oriented N-S. Zircon is usually colorless in thin section.
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Anorthosite thin section

Chondrite L4. Tagounite 001, Morocco 1999 sample 2. Polished section. Chondrite H5 Sahara 97095.

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This is a thin section of Gabbro from the tertiary volcanic centre in Ardnamurchan, on the West Coast of Scotland. Famous for its complete ring dyke made of Eucrite, a similar gabbro. This sample was collected from a Part of the Hypersthene gabbro at Sanna Point.

Intrusive igneous, plutonic . Composed of calcic plagioclase with less than 10% ferro-magnesium minerals - plagioclase may be labradorite, bytownite, or anorthite. The name is from anorthose, an old name for triclinic feldspars. Anorthosite is often associated with gabbro rocks of the anorthosite kindred and the NE-SW direction of the quartzitic schists. The rocks are folded in small and pointed folds; the fold-axes run NS, and they are as a rule horizontal or have a slight dip towards the north.