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


Rocks under the Microscope. Some common rock types as seen under the microscope. These are photomicrographs - very thin slices of rock, seen in plane-polarised light, or between crossed polarisers, when the colours seen are produced by interference of light.

Cumulate rocks typically have the same minerals about the same size. Anorthosite: Anorthosite: A leucocratic coarse-grained plutonic rock consisting essentially of plagioclase (usually labradorite or bytownite) often with small amounts of pyroxene. Olivine, amphibole, ilmenite, magnetite, and spinel are also sometimes present. The term anorthosite, from Frenc anorthose (term for plagioclase) was coined by Sterry Hunt. Damage produced during thin section grinding causes speckles of light in the biotite, where the crystal lattice has been deformed. Zoisite developed in pagioclase in an anorthosite. Zoisite is essentially an orthorhombic, very low-Fe epidote.

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Inequigranular anorthosite. Ths rock has a continuum of grain sizes, from very small to quite large. 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. The thin section consists almost entirely of plagioclase feldspar with minor pyroxene. All grains show evidence of considerable shock caused by meteorite impact events - the black glass coating was produced at this time.

EOS March 6, 313-315. Sato M., Hicklin N.L. and McLane J.E. (1973) Oxygen fugacity values of … 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.

In the previous section it was emphasized that the mechanical model should not be assumed, but should be soft mineral in a joint, it is often useful to try to press a thin knife into the joint. It is Berget utgörs av en anorthosite, som består till 

• It contain plagioclase of An35-65 range. 14. ORIGIN of anorthosite Magmatic Origin: Massif anorthosite are magmatic and layered anorthosites are magmatic differentiation.

A thin section of the anorthosite sample was prepared and subsequently pol-ished. First the thin section was subjected to a 3 µm diamond polish for roughly 2 h, then for a half an hour using a 1/4 µm diamond polish. Finally, the sample was polished for 5 min by hand in colloidal silica. The final thickness was slightly

Anorthosite thin section

in Fennoscandia; Baddeleyite U Pb dating of a suite of massif-type anorthosite in S. Sweden. The Laxemar subarea is dominated by the porphyritic Ävrö granite 5.2 Modal analyses Modal analyses of thin-sections have been carried out on 51 30 Diorite Gabbro Anorthosite P 10 Quartz monzodiorite Quartz monzogabbro  Area Number of sites 21 11 10 42 1 1 1 4 1 2 1 1 1 1 TBT µg/kg dry weight 186 Lager 1986) and microbial layering has been recognised in thin section from in the south-central part, consisting of olivine bearing leucogabbro to anorthosite. The stone tables are made of marble, gabbro and anorthosite. A polished thin section of c millimetres is sampled from a rock and examined with a polarising  3 Citations · Petrographic study of high-grade gneisses, Halland area · Diana Carlsson · Peat stratigraphical study of hydrological conditions at Stass Mosse,  Anorthosite Personeriasm humility.

Anorthosite thin section

Gabbros and norites are found in sills, dikes, stocks, lopoliths, and other bodies. The thin section.
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Anorthosite thin section

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 thin section. Streak: White.

Some smaller plutons, exemplified by many anorthosite bodies in the U.S. and Harris in Scotland, cover only a few dozen square kilometres.
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Microscopic examination of a thin section of garnet anorthosite from the former locality showed it to consist predominantly of scapolitised plagioclase; large (2 - 9mm) garnets, altered to kelyphite on their margins; and minor clinopyroxene, hornblende and magnetite-ilmenite.

Dispersion: r < v; weak. ® = 1.573{1.577 ¯ = 1.580{1.585 ° = 1.585{1.590 2V(meas.) = 78±{83± Cell Data: Space Group: P1 (low).

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Origin of Anorthosite by Textural Coarsening: Quantitative Measurements of a Natural Sequence of Textural Development MICHAEL D. HIGGINS* SCIENCES DE LA TERRE, UNIVERSITE´ DU QUE´BEC A` CHICOUTIMI, CHICOUTIMI, G7H 2B1, CANADA Thin section of an olivine oikocryst adjacent to section …

The section is normal to the foliation and in the same plane as (a).

Tunn sektion av kvartsit. Granat glimmer schist. Is. Gabbro från Rum, Skottland. Bronsitit. Mylonit. Kolhaltiga peloider. Anorthosite. Cordierite.

5. Photomicrograph of a thin section  the anorthosite. Rock fragments were tested with the Soxhlet extractor and uncovered thin sections were wiped with acidified solutions of HCI, HN03 and H2S04  23 Dec 2020 Bushveld anorthosites commonly contain the so-called “mottles” It is relatively unaltered except for very thin (~ 10 μm) sub-vertical veinlets of The section analysed by FESEM is highlighted by the stippled box. b This is a thin section of Anorthosite from Roineabhal, a mountain on the Island of Harris in the Outer Hebrides. Of Lewisian age, and one of the most ancient  behaviour of plagioclase is assessed from analyses of three anorthosite units deformed polished thin sections using a JEOL Superprobe JXL. 8200 at the  bauxite in thin sections (Fig.

Our own study of the 98 largest clasts in a thin section of Shişr 161 (25.2% Al. 2. O. 3) yielded only 4 of pure plagioclase [9]. Of 100 Andesite. Andesite is an extrusive igneous rock that is higher in silica than basalt and lower than … 2013-04-23 Anorthosite plutons occur in a wide range of sizes. Some smaller plutons, exemplified by many anorthosite bodies in the U.S. and Harris in Scotland, cover only a few dozen square kilometres. Larger plutons, like the Mt. Lister Anorthosite, in northern Labrador, Canada, cover several thousands of … 2020-12-23 [ LEFT ] NASA photo of an Apollo 16 rake sample, 65785, with a clast of pink spinel troctolite, labeled PST, set within recrystallized impact melt. Scale bar on the left edge is in millimeters.