Westerveldite from Igdhlnguaq, Ilimau.ssaq alkaline massif, South Greenland I

• Main Authors: I. S. Oen, Geologisch Instituut, E. A. J. Burke, C. Kiefr
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Greenland; Ilimaussaq
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.454.2683; http://www.minersoc.org/pages/Archive-MM/Volume_41/41-317-77.pdf

SUMMARY. Microprobe and X-ray investigation fa mineral occurring with breithauptite, nickeline, and other arsenides in the naujaite at Igdlfinguaq, Ilimaussaq alkaline massif, S. Greenland, shows that this mineral, which was formerly misidentified as 'maucherite', is a westerveldite (Fe0.,sNi0.15)As, of much iron-richer composition than the nickeloan westerveldites from the only two other known occurrences of this mineral. Westerveldite from Igdlfinguaq was presumably formed by reaction of nickeline with iron-rich solutions under conditions of reheating at temperatures of about 45 o ~ C and under partial pressures of arsenic below those necessary to stabilize nickeline. Sulphur-bearing 1611ingite occurs as exsolution blades in the westerveldite. Iron-rich nickeline, up to a composition (Ni0.82Fe0.18)As0.9~Sbo.05, was presumably formed by recrystallization of nickeline in the transition stage just before this mineral became unstable and was replaced by westerveldite. THE occurrence of Ni-arsenides and breithauptite in a few aggregates of mm-size in a naujaite rock at Igdlfinguaq in the Iltmaussaq alkaline massif, South Greenland, was described by Oen and Sorensen (1964). The naujaite is a rock composed of several-cm large poikilitic crystals of microcline, nepheline, aegirine, and eudialite, containing numerous inclusions of sodalite. However, the naujaite samples with arsenides are from a natrolite- and sodalite-rich reaction zone along the contact with a younger natrolite-sodalite-analcime-bearing cmite-arfved-