Thin Section Granites

Biotite metaluminous granite showing a close up of one crystal.

Thin section granites.

Granite ˈ ɡ r æ n ɪ t is a common type of felsic intrusive igneous rock that is granular and phaneritic in texture. Quartz thin section photomicrographs are taken in plane polarized light and cross polarized light and can easily be recognized under the microscope. Photomicrographs of these minerals in thin section from s type granites of the lachlan fold belt are shown in figure 2a and 2b. 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.

Granites in the slate belt together with those in the shan scarps segment of the mogok metamorphic belt to the west fig. Damage produced during thin section grinding causes speckles of light in the biotite where the crystal lattice has been deformed. This means that biotite in standard thin sections rarely goes completely extinct. Enjoy the videos and music you love upload original content and share it all with friends family and the world on youtube.

By comparing the plane polarized light left and crossed polarizer right images we can see that there are three minerals in this granite. S type granites can also contain aluminium rich iron and magnesium rich biotites. Identification tables for common minerals in thin section these tables provide a concise summary of the properties of a range of common minerals. 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.

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. Biotite brown grains in plain light and pinkish brown with crossed polars the brown color is due to a property called. If a mineral commonly has a range of colours it will appear once for each colour. The presence of these aluminous silicate minerals are commonly used as a means of initially classifying granites as s type.

Within the tables minerals are arranged by colour so as to help with identification. 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. 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. Strictly speaking granite is an.