Townendite, Na8ZrSi6O18, a new uranium-bearing lovozerite group mineral from the Ilímaussaq alkaline complex, Southern Greenland

Ian Grey, Colin Macrae, William Mumme, Allan Pring

    Research output: Contribution to journalArticle

    3 Citations (Scopus)

    Abstract

    Townendite, a new U-bearing mineral belonging to the trigonal lovozerite group has been found in the lujavrite layers of nepheline syenites in the Ilímaussaq alkaline complex in Southern Greenland. Its composition from electron microprobe analysis is Na6.08Ca0.16Mn 0.17Fe0.13Zr0.67Y0.13Sn 0.04U0.02Ti0.01Si6O16.35 (OH)1.65. Townendite has rhombohedral symmetry, R3m, with cell parameters (hexagonal setting) a = 10.345(2) Å, c = 13.103(2) Å. The structure has been refined using single-crystal X-ray data to R1 = 0.056 for 532 reflections with F > 4σ (F). Lovozerite group minerals are cyclosilicates in which Si6 (O,OH)18 rings of tetrahedra share corners with isolated MO6 octahedra (M = Zr, Ti, Ca) to form a 3D framework, with large cations, mainly Na+, located in cavities in the framework. Townendite dif-fers from other compositionally related lovozerite group minerals in having a high occupancy (92%) of another set of octahedrally coordinated sites that share faces with the MO6 octahedra, giving linear face-shared trimers parallel to [001]. These sites are occupied predominantly by Na+. Full occupancy of all sites corresponds to the ideal composition Na8ZrSi6O 18. Townendite is a significant contributor, along with steenstrupine-(Ce), to U resources in the Ilímaussaq alkaline complex.

    Original languageEnglish
    Pages (from-to)646-650
    Number of pages5
    JournalAmerican Mineralogist
    Volume95
    Issue number4
    DOIs
    Publication statusPublished - Apr 2010

    Keywords

    • Ilimaussaq alkaline complex
    • New lovozerite group mineral
    • New sodium zirconium silicate
    • New U-bearing mineral

    Fingerprint Dive into the research topics of 'Townendite, Na8ZrSi6O18, a new uranium-bearing lovozerite group mineral from the Ilímaussaq alkaline complex, Southern Greenland'. Together they form a unique fingerprint.

  • Cite this