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Synthesis of the bedrock geology in southern Norrbotten

Anorthite weathers quite readily, so it’s not terribly abundant on Earth. Unfortunately, these thin sections are thicker than the usual 30 micrometers, and in crossed polarizers (XPL) the plagioclase has colors of the upper first order, instead of the usual grey. The QAPF diagram ( see on this page ) shows that anorthosite has more than 90% plagioclase (P) compared to K-feldspar (or alkali feldspar, A), less than 5% quartz (Q) and less 5% feldspathoids (F). 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.

Anorthosite thin section

You can find the explanation on the plagioclase feldspar page. Anorthosite Thin Sections (cont.) 2.2 Secondary Minerals Quartz. Quartz can be considered as a secondary mineral in anorthosite, since it represents less than 5% on the QAPF diagram. 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.

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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.

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to be a thin skin with vanishing thermal capacity. 10) Apart from these locations, biotite is rare in the thin section. in Fennoscandia; Baddeleyite U Pb dating of a suite of massif-type anorthosite in S. Sweden.

514-394- Anorthosite Mail-tigerdirect. Diorite Rock Composition, Formation and Uses Area. Diorite Igneous Rock (Page 1) - Line.17QQ.com. Examples of Plutonic Rocks. Pictures and Descriptions of Anorthosite Thin Sections (cont.) 2.2 Secondary Minerals Quartz. Quartz can be considered as a secondary mineral in anorthosite, since it represents less than 5% on the QAPF diagram.
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A coarse grained igneous rock, anorthosite is characterized by being … Proterozoic anorthosite Age. Proterozoic anorthosites were emplaced during the Proterozoic Eon (ca. 2,500–542 Ma).. Mode of occurrence. 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.

NASA photo S72-48821. [ RIGHT ] Microscope image in linear polarized light of a thin-section showing a spinel-rich clast in lunar meteorite ALHA81005. The Bethampudi layered anorthosite complex at the border zone of Archaean supracrustal rocks of Khammam district, Eastern Ghats shows normal stratification predominantly in the form of rhythmic layering and often exhibits of zebra layering. Graded bedding and cumulate structures are also noticed.
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PDF Petrogenesis of some Proterozoic granitoid suites and

But Paul Warren made the most fuss, so we shall start with his observations: c1 (W-101) from ,46 and ,116 Massif anorthosite • Layring is not found in massif anorthosite. • It contain plagioclase of An35-65 range.

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U-Pb zircon age of c Ma syenogranite within the protogine zone at

Is. Gabbro från Rum, Skottland. Bronsitit. Mylonit. Kolhaltiga peloider. Anorthosite. Cordierite. 2.