American Mineralogist, Volume 68, pages 100,1-1008, /983 Ilvaite, an alteration product replacing olivine in the Skaergaard intrusion

• Main Authors: H. R. Nasrunn, J M. Huches, R. W. Brnnrb
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Greenland; East Greenland
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.520.5481; http://rruff.info/doclib/am/vol68/AM68_1004.pdf

Ilvaite, CaFe?+Fe3+(OH)Si2Os, is an abundant mineral in the upper parr of the Skaergaard intrusion of East Greenland. It occurs in these rocks as an alteration product replacing fayalitic olivine. Analyses of unaltered olivine and ilvaite demonstrate that the replacement process requires the removal of FeO and MgO from the olivine and the addition of CaO, H2O, and 02. Single crystal X-ray diffraction studies indicate that the Skaergaard ilvaite is the orthorhombic polymorph. It is suggested that the ilvaite crystal-lized under conditions of high /Hzo, low.7co2, low /C2, and moderate? during the subsolidus cooling of the intrusion.