Horoman peridotite (lherzolite) - full thin section

 For a general description of the Horoman peridotite body, see the post of July 2, 2013: "Horoman Peridotite ... - olivine microfabfric".

This image shows a full thin section of Horoman peridotite. The 29-mm long dimension is actually shorter than a typical thin section, which is usually between 38 mm and 42 mm. The coarse texture of the peridotite is evident in this image. For example, the large olivine grain just left of center is about 10 mm in length. Most of the olivine grains are strained, as indicated by their banded coloration (deformation banding). The pyroxene grains also show deformation banding, but much less obviously than the olivine.

FULL THIN SECTION

Click on image to enlarge.          Photo © Daniel R. Snyder

Horoman peridotite (lherzolite), Hokkaido, Japan. Full thin section, XPL macrophotograph. Brightly-colored grains are olivine; gray grains are pyroxenes. Smaller, rounded brown grains are symplectite nodules. Imaged area approximately 21 mm by 29 mm.

REFERENCES

Niida,  K., (1975), Textures and Olivine Fabrics of the Horoman Ultramafic Rocks, Japan; Jour. Japan. Assoc. Min. Petr. Econ, Geol.; 70, p. 265-285. (In English with Japanese abstract)

Niida, K., (1984), Petrology of the Horoman Ultramafic Rocks in the Hidaka Metamorphic Belt, Hokkaido, Japan, Journal of the Faculty of Science, Hokkaido University. Series 4, Geology and mineralogy, 21(2):197-250. (In English)

Niida, K.,  and Takazawa, E. (2007), Origin of Layering observed in the Horoman Peridotite Complex, Japan, Jour. Geol Soc. Japan; 113:Supplement, p. 167-184. (In Japanese except for some of the figure labels)

Sawaguchi, T., (2004), Deformation history and exhumation process of the Horoman Peridotite Complex, Hokkaido, Japan. Tectonophysics, 379, p. 109-126. (In English)

Takahashi, N., (1991), Origin of three peridotite suites from the Horoman peridotite complex, Hokkaido, Japan; Melting, melt segregation, and solidification processes in the upper mantle; Jour. Min.Petr. Econ. Geol.,  86: p. 199-215. (In English) 

Horoman peridotite (lherzolite), Hokkaido, Japan - symplectite pseudomorphs after garnet.

For a general description of the Horoman peridotite body, see the post of July 2, 2013: "Horoman Peridotite ... - olivine microfabfric".

Symplectite nodules (intergrowths of fine-grained minerals - in this example, spinel and clinopyroxene) are abundant in some layers of the Horoman peridotite complex. Because of their mineral assemblages and bulk chemical composition, these nodules are thought to be pseudomorphs after pyrope garnet.

Click on image to enlarge.          Photo © Daniel R. Snyder
Three large symplectite nodules in the Horoman peridotite body.  Brightly-colored
grains are olivine; gray grains are pyroxenes. XPL. Imaged area 2.7 mm by 4 mm.

Below: Higher-magnification image (10x objective) of a small symplectite nodule.

Click on image to enlarge.          Photo © Daniel R. Snyder
XPL. Imaged area 0.5 mm by 0.8 mm.

text

REFERENCES

Morishita, T., 2000, Three-dimensional Microstructure of Symplectite Minerals in the Horoman Peridotite: A preliminary Analysis; Jour. Geol Soc. Japan; 106:11, p. 800-811. (In English with Japanese abstract)

Morishita, T., and Arai, S., (2003), Evolution of spinel–pyroxene symplectite in spinel–lherzolites from the Horoman Complex, Japan; Contrib. Mineral. Petrol; 144, p. 509-22. (In English)

Odashima, N., Morishita, T., Ozawa, k., Nagahara, H., Tsuchiyama, A., and Nagashima, R., (2008), Formation and deformation mechanisms of pyroxene-spinel in an ascending mantle, the Horoman peridotite complex, Japan: an EBSD (electron backscatter diffraction) study; Jour. Mineral. Petrol. Sci., 103, p. 1-15. (In English)