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.
to share – to copy, distribute and transmit the work
to remix – to adapt the work
Under the following conditions:
attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
https://creativecommons.org/licenses/by/2.0CC BY 2.0 Creative Commons Attribution 2.0 truetrue