Gabbronorite (absolute black)

Gabbronorite is a mafic composed of the calcium-rich plagioclase and hypersthene, olivine can be present in small quantities. The name gabbronorite is derived the Norwegian name for Norway, Norge. In hand specimen gabbronorite is indistinguishable from gabbro and can be discriminated with a thin section study under the petrographic microscope. The difference between gabbronorite and gabbro is the type of pyroxene of which it is composed; gabbronorite is composed of orthopyroxenes, (enstatites), whereas the principal pyroxenes in gabbro are clinopyroxenes, generally augites. Gabbronorite occurs with gabbro and other mafic to ultramafic rocks in layered intrusions which are often associated with platinum orebodies such as in the Bushveld Igneous Complex in South Africa, the Skaergaard igneous complex of Greenland, and the Stillwater igneous complex in Montana, USA.

Polished "absolute black" gabbronorite

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
Pyroxene, plagioclase and rare biotite in a gabbronorite, Zimbawe. PPL image, 2x (Field of view = 7mm)/td>	Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 2x (Field of view = 7mm)/td>	Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 2x (Field of view = 7mm)/td>
Pyroxene, plagioclase and rare biotite in a gabbronorite, Zimbawe. PPL image, 2x (Field of view = 7mm)/td>	Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 2x (Field of view = 7mm)/td>	Pyroxene, plagioclase and rare biotite in a gabbronorite, Zimbawe. PPL image, 2x (Field of view = 7mm)/td>
Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 2x (Field of view = 7mm)/td>	Pyroxene, plagioclase and rare biotite in a gabbronorite, Zimbawe. PPL image, 2x (Field of view = 7mm)/td>	Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 2x (Field of view = 7mm)/td>
Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 2x (Field of view = 7mm)/td>	Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 2x (Field of view = 7mm)/td>	Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 2x (Field of view = 7mm)/td>
Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 2x (Field of view = 7mm)/td>	Pyroxene and plagioclase in a gabbronorite, Zimbawe. PPL image, 10x (Field of view = 2mm)/td>	Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 10x (Field of view = 2mm)/td>
Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 10x (Field of view = 2mm)/td>	Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 10x (Field of view = 2mm)/td>>	Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 10x (Field of view = 2mm)/td>
Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 10x (Field of view = 2mm)/td>	Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 10x (Field of view = 2mm)/td>	Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 10x (Field of view = 2mm)/td>
Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 10x (Field of view = 2mm)/td>	Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 10x (Field of view = 2mm)/td>	Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 10x (Field of view = 2mm)/td>
Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 10x (Field of view = 2mm)/td>	Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 10x (Field of view = 2mm)/td>	Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 10x (Field of view = 2mm)/td>
Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 2x (Field of view = 7mm)/td>	Pyroxene with exolution lamellae in a gabbronorite, Zimbawe. XPL image, 10x (Field of view = 2mm)/td>