Harzburgite

Named for occurrences in the Harz Mountains of Germany, a harzburgite is an ultrabasic igneous rock dominated by essential olivine and orthopyroxene with or without small amounts of clinopyroxene. Accessory minerals include plagioclase, spinel, garnet, ilmenite, chromite and magnetite. Harzburgites are a peridotite and a major component of the upper mantle where they form as residues of partial melting of lherzolite. Metasomatism of harzburgite in the mantle can produce accessory micas and amphiboles. Harzburgite is a common mantle xenolith within mantle-derived magmas and within the upper portions of the mantle sequence of ophiolites. Harzburgite can also form as cumulates within layered intrusions.

Diagram for Ultramafic rocks.Harzburgites field in blue

Harzburgite. Stillwater Complex, Beartooth Mountains, Montana, USA. From James St. John .

Bibliography

• Cox et al. (1979): The Interpretation of Igneous Rocks, George Allen and Unwin, London.
• Howie, R. A., Zussman, J., & Deer, W. (1992). An introduction to the rock-forming minerals (p. 696). Longman.
• Le Maitre, R. W., Streckeisen, A., Zanettin, B., Le Bas, M. J., Bonin, B., Bateman, P., & Lameyre, J. (2002). Igneous rocks. A classification and glossary of terms, 2. Cambridge University Press.
• Middlemost, E. A. (1986). Magmas and magmatic rocks: an introduction to igneous petrology.
• Shelley, D. (1993). Igneous and metamorphic rocks under the microscope: classification, textures, microstructures and mineral preferred-orientations.
• Vernon, R. H. & Clarke, G. L. (2008): Principles of Metamorphic Petrology. Cambridge University Press.

Photo
Orthopyroxene (gray) and olivine crystals. XPL image. 10x (Field of view = 2mm)	Orthopyroxene and olivine crystals. PPL image. 10x (Field of view = 2mm)	Orthopyroxene (gray) and Olivine crystals. XPL image. 10x (Field of view = 2mm)
Orthopyroxene (gray) and olivine crystals. XPL image. 10x (Field of view = 2mm)	Orthopyroxene (gray) and olivine crystals. XPL image. 10x (Field of view = 2mm)	Orthopyroxene (gray) and olivine crystals. XPL image. 10x (Field of view = 2mm)
Orthopyroxene (gray) and olivine crystals. XPL image. 10x (Field of view = 2mm)