Thin Section Granites

These are photographs of a thin section of granite magnification 10x perhaps the most common igneous rock we encounter.

Thin section granites.

Strictly speaking granite is an. Granites can be predominantly white pink or gray in color depending on their mineralogy the word granite comes from the latin granum a grain in reference to the coarse grained structure of such a completely crystalline rock. Some common rock types as seen under the microscope. Granite ˈ ɡ r æ n ɪ t is a common type of felsic intrusive igneous rock that is granular and phaneritic in texture.

By comparing the plane polarized light left and crossed polarizer right images we can see that there are three minerals in this granite. This means that biotite in standard thin sections rarely goes completely extinct. Identification tables for common minerals in thin section these tables provide a concise summary of the properties of a range of common minerals. If a mineral commonly has a range of colours it will appear once for each colour.

Biotite brown grains in plain light and pinkish brown with crossed polars the brown color is due to a property called. Rocks under the microscope. Within the tables minerals are arranged by colour so as to help with identification. Biotite metaluminous granite showing a close up of one crystal.

Photomicrographs of these minerals in thin section from s type granites of the lachlan fold belt are shown in figure 2a and 2b. 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. Damage produced during thin section grinding causes speckles of light in the biotite where the crystal lattice has been deformed. Granites in the slate belt together with those in the shan scarps segment of the mogok metamorphic belt to the west fig.

Originally plane polarized scanning in separate e w n s orientations was attempted to highlight pleochroic variation but this ultimately had to be abandoned due to significant. S type granites can also contain aluminium rich iron and magnesium rich biotites. Each thin section was first scanned in unpolarized light and then again between two sheets of crossed polaroid film aligned parallel to the thin section edges. 6 1 and in the southward continuation of the slate belt in southwestern thailand comprise the western granite belt of hutchison 1973 the western tin belt granites of mitchell 1976 1977 the central and southern part of the central granitoids province of khin zaw.