Norite

Norite is a coarse-grained basic igneous rock dominated by essential calcic plagioclase and orthopyroxene. Norite may be essentially indistinguishable from gabbro without thin section study under the petrographic microscope. The principal difference between norite and gabbro, however, is the type of pyroxene of which it is composed; norite is predominately composed of orthopyroxenes, largely high magnesian enstatite or an iron bearing intermediate hypersthene, whereas the principal pyroxenes in gabbro are clinopyroxenes, generally medially iron-rich augites.

Norite 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. The name Norite is derived from the Norwegian name for Norway: Norge.

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Diagram for Gabbroic rocks. From IUSG



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Norite from Cortlandt Complex, Westchester County, New York. Photo by Michael P. Klimetz.




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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Plagioclase and orthopyroxenes in a Norite from Germany. PPL image, 2x (Field of view = 7mm)
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Plagioclase and orthopyroxenes in a Norite from Germany. XPL image, 2x (Field of view = 7mm)
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Plagioclase and orthopyroxenes in a Norite from Germany. PPL image, 2x (Field of view = 7mm)
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Plagioclase orthopyroxenes and clinopyroxene (stronger birefringence) in a Norite from Germany. XPL image, 2x (Field of view = 7mm)
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Plagioclase and orthopyroxenes in a Norite from Germany. PPL image, 2x (Field of view = 7mm)
norite0163(6).jpg

Plagioclase and orthopyroxenes in a Norite from Germany. XPL image, 2x (Field of view = 7mm)
norite0163(7).jpg

Plagioclase and orthopyroxenes in a Norite from Germany. PPL image, 2x (Field of view = 7mm)
norite0163(8).jpg

Plagioclase and orthopyroxenes in a Norite from Germany. XPL image, 2x (Field of view = 7mm)
norite0163(9).jpg

Plagioclase and orthopyroxenes in a Norite from Germany. PPL image, 2x (Field of view = 7mm)
norite0163(7).jpg

Plagioclase and orthopyroxenes in a Norite from Germany. PPL image, 2x (Field of view = 7mm)
norite0163(8).jpg

Plagioclase and orthopyroxenes in a Norite from Germany. XPL image, 2x (Field of view = 7mm)
norite0163(9).jpg

Plagioclase and orthopyroxenes in a Norite from Germany. PPL image, 2x (Field of view = 7mm)
norite0163(10).jpg

Plagioclase orthopyroxenes and clinopyroxene (stronger birefringence) in a Norite from Germany. XPL image, 2x (Field of view = 7mm)
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Plagioclase and orthopyroxenes in a Norite from Germany. PPL image, 2x (Field of view = 7mm)
norite0163(12).jpg

Plagioclase orthopyroxenes and clinopyroxene (stronger birefringence) in a Norite from Germany. XPL image, 2x (Field of view = 7mm)
norite0163(13).jpg

Plagioclase and orthopyroxenes in a Norite from Germany. PPL image, 2x (Field of view = 7mm)
norite0163(14).jpg

Plagioclase and orthopyroxenes in a Norite from Germany. XPL image, 2x (Field of view = 7mm)
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Plagioclase and orthopyroxenes in a Norite from Germany. PPL image, 2x (Field of view = 7mm)
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Plagioclase orthopyroxenes and clinopyroxene (stronger birefringence) in a Norite from Germany. XPL image, 2x (Field of view = 7mm)
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Plagioclase and orthopyroxenes in a Norite from Germany. PPL image, 2x (Field of view = 7mm)
norite0163(18).jpg

Plagioclase and orthopyroxenes in a Norite from Germany. XPL image, 2x (Field of view = 7mm)
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Plagioclase and orthopyroxenes in a Norite from Germany. PPL image, 2x (Field of view = 7mm)
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Plagioclase and orthopyroxenes in a Norite from Germany. XPL image, 2x (Field of view = 7mm)
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Plagioclase and orthopyroxenes in a Norite from Germany. XPL image, 2x (Field of view = 7mm)