Alnöite

Alnöite: An ultramafic rock with phenocrysts of phlogopite-biotite, olivine and augite in a groundmass of melilite (often altered to calcite), augite and/or biotite with minor perovskite, garnet and calcite. Named after the type locality at Alnö Island, Västernorrland, Sweden. First description by Rosenbusch is dated in 1887.

Alnöites (Fig.1-2) are mafic alkaline silicate rocks that belongs to the kimberlite family and are melilite-rich. The type locality (Stornäset or Näset ) from which alnöite was originally described and given the name "melilite basalt" by Törnebohm (1882), shows a black, dense rock with phenocrysts of gold-brown phlogopite and apatite.

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Gold-brown phlogopite crystals in a Alno öite from Näset, Alno ö island. From Hildegard Wilske


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Gold-brown phlogopite crystals in a Alno öite from Näset, Alno ö island. From Hildegard Wilske



Bibliography



• Andersson, M. (2015). 3D Structure and Emplacement of the Alnö Alkaline and Carbonatite Complex, Sweden: Integrated Geophysical and Physical Property Investigations.
• Kresten P (1980): The Alnö complex: tectonics of dyke emplacement. Lithos 13:153–158.
• Brueckner H.K, Rex DC (1980): K-A and Rb-Sr geochronology and Sr isotopic study of the Alnö alkaline complex , northeastern Sweden. Lithos 13:111–119.


Photo
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Phlogopite (brown), altered olivine (yello-green) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 1x (Field of view = 9mm)
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Phlogopite (brown), altered olivine (yello-green) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 1x (Field of view = 9mm)
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Phlogopite (brown) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 1x (Field of view = 9mm)
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Phlogopite and apatite (I order gray) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. XPL image, 1x (Field of view = 9mm)
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Phlogopite (brown) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 1x (Field of view = 9mm)
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Phlogopite (brown) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 1x (Field of view = 9mm)
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Phlogopite (brown) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 1x (Field of view = 9mm)
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Phlogopite and apatite (I order gray) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. XPL image, 1x (Field of view = 9mm)
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Phlogopite (brown) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 1x (Field of view = 9mm)
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Phlogopite and apatite (I order gray) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. XPL image, 1x (Field of view = 9mm)
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Phlogopite (brown), altered olivine (yello-green) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 1x (Field of view = 9mm)
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Phlogopite (brown), altered olivine (yello-green) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 1x (Field of view = 9mm)
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Phlogopite, altered olivine and apatite (I order gray) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. XPL image, 1x (Field of view = 9mm)
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Phlogopite (brown), altered olivine (yello-green) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 1x (Field of view = 9mm)
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Phlogopite (brown) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 1x (Field of view = 9mm)
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Phlogopite (brown) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 1x (Field of view = 9mm)
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Phlogopite (brown), altered olivine (yello-green) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 1x (Field of view = 9mm)
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Phlogopite (brown), altered olivine (yello-green) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 1x (Field of view = 9mm)
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Phlogopite (brown) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 2x (Field of view = 7mm)
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Phlogopite (brown), altered olivine (yello-green) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 2x (Field of view = 7mm)
alnoite(23).jpg

Phlogopite (brown), altered olivine (yello-green) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 2x (Field of view = 7mm)
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Phlogopite (brown) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 2x (Field of view = 7mm)
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Phlogopite (brown), altered olivine (yello-green) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 2x (Field of view = 7mm)
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Phlogopite (brown) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 2x (Field of view = 7mm)
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Phlogopite (brown) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 2x (Field of view = 7mm)
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Phlogopite and apatite (I order gray) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 2x (Field of view = 7mm)
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Phlogopite (brown) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 2x (Field of view = 7mm)
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Phlogopite (brown) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 2x (Field of view = 7mm)
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Phlogopite (brown) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 2x (Field of view = 7mm)
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Phlogopite (brown) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 2x (Field of view = 7mm)
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Phlogopite (brown), altered olivine (yello-green) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 10x (Field of view = 2mm)
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Phlogopite, altered olivine and apatite (I order gray) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. XPL image, 10x (Field of view = 2mm)
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Altered olivine (yello-green) crystal in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 10x (Field of view = 2mm)
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Phlogopite (brown), altered olivine (yello-green) and apatite (colorles) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 10x (Field of view = 2mm)
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Phlogopite (brown), calcite (after melilite) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 10x (Field of view = 2mm)
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Phlogopite, calcite (after melilite) crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. XPL image, 10x (Field of view = 2mm)
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Phlogopite (brown), calcite (after melilite) and apatite crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 10x (Field of view = 2mm)
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Phlogopite, calcite (after melilite) and apatite crystals in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 10x (Field of view = 2mm)
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Phlogopite (brown) in a fine-grained groundmass. Alnöite, Alnö complex, Sweden. PPL image, 10x (Field of view = 2mm)