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 from Gabbro + Norite (from 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.

This thin section is a Gabbronorite from Zimbawe (Africa), called also Absolute black, due to the deep-black color.

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Gabbronorite, Greenhills (New Zeland). Photo of Richard Arculus.



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Polished Absolute black Gabbronorite





Bibliography



• Eric A.K.Middlemost (1985): Magmas and Magmatic Rocks. Longman, London
• Ron H. Vernon (2004): A pratical guide to rock microstructure. Cambridge editore
• K.G.Cox, J.D.Bell & R.J Pankhurst (1979): The interpretetion of igneous rocks. George Allen&Unwin editori.
• David Shelley (1983): Igneous and metamorphic rocks under the microscope. Campman & Hall editori



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