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File:Kakortokite (eudialytic nepheline syenite) Kangerdluarssaq Fjord,Greenland.jpg

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Summary

Description

Kakortokite (cut surfaces; 9.5 cm tall) - magmatically layered kakortokite from Greenland’s Precambrian-aged Ilímaussaq Complex. White = nepheline Black = arfvedsonite amphibole Red = eudialyte


Kakortokite is a rare intrusive igneous rock. The name is traditionally applied to eudialytic nepheline syenites found in southern Greenland. The attractive sample shown here principally contains three minerals: whitish nepheline ((Na,K)AlSiO4), blackish arfvedsonite amphibole (NaNa2((Fe+2)4Fe+3)Si8O22(OH)2), and reddish eudialyte (Na4(Ca,Ce)2(Fe,Mn,Y)ZrSi8O22(OH,Cl)2).

Notice that the amphibole and the eudialyte show layering. Magmatic layering is expected to occur in the lower portions of old magma chambers, and this kakortokite sample is indeed from the floor rocks of an old igneous intrusion.

Geologic unit: Ilímaussaq Intrusion (Ilímaussaq Complex; Ilímaussaq Alkaline Complex), an 8 x 17 km intrusion in the 1.12-1.35 b.y. Gardar Igneous Province, developed in a failed rift zone.

Age: late Mesoproterozoic, 1.16 billion years.

Locality: cliff outcrops on southern side of eastern end of Kangerdluarssaq Fjord (also spelled Kangerdluarsuk Fjord), far-southern Greenland.
Date
Source Kakortokite (eudialytic nepheline syenite) (Ilimaussaq Intrusion, Mesoproterozoic, 1.16 Ga; Kangerdluarssaq Fjord, far-southern Greenland) 1
Author James St. John

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This image was originally posted to Flickr by jsj1771 at https://www.flickr.com/photos/47445767@N05/14979712946. It was reviewed on 23 August 2014 by FlickreviewR and was confirmed to be licensed under the terms of the cc-by-2.0.

23 August 2014

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current00:17, 23 August 2014Thumbnail for version as of 00:17, 23 August 2014697 × 979 (453 KB)TillmanTransferred from Flickr via Flickr2commons

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