HIGGINS TEXTURAL COARSENING OF ANORTHOSITE Fig. 1. Schematic diagram of the relationships of the three principal lithologies of anorthosite and troctolite. The section is ~1 m thick, but the horizontal scale is not linear. To the left the Nodular Troctolite consists of olivine oikocrysts 20–30 cm long (pale) set in a matrix of anorthosite 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.
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The section is normal to the foliation and in the same plane as (a). (c) Section from the interior of an oikocryst into the matrix, digitized from photographs of three large thin sections, parts of two of which are shown in (a) and (b). 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. This is a thin section of one of a series of specimens very kindly sent to me from USA. Many thanks to the donor! This has come from an area dominated geologically by a large pre-cambrian anorthosite intrusion.
• Bitumenkälla och Anorthosite, NO. Sparagmitt in Dünnschliffen [On the behavior of canada balsam in thin sections].
Anorthosite is a rock type of the mafic-ultramafic succession, The thin section above doesn't allow evaluation of textures that may be related to overgrowths. Cite. 10th Dec, 2016.
Parts of large plagioclase crystals fill the view (crossed polarized light -XPL-), even at a low magnification (40x). Vivid colors (yellow, pink, blue, even green) of the upper first order and the lower second order are due to the larger-than-usual thickness of the section, but also suggest the presence of anorthite.
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.
A thin sliver of rock is cut from the sample with a diamond saw and ground optically flat. It is then mounted on a glass slide and then ground smooth using progressively finer abrasive grit until the sample is only 30 μm thick.
Fiss moll ackord piano
This rock is composed of calcic plagioclase with less than 10% ferro-magnesium minerals. The plagioclase may be labradorite, bytownite, or 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.
Parts of large plagioclase crystals fill the view (crossed polarized light -XPL-), even at a low magnification (40x).
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