Geology of Ore Deposits

, Volume 51, Issue 7, pp 608–616

Chemical composition of nyerereite and gregoryite from natrocarbonatites of Oldoinyo Lengai volcano, Tanzania


    • Department of MineralogySt. Petersburg State University
  • J. Keller
    • Mineralogisch-Geochemisches InstitutUniversitat Freiburg
  • J. Spratt
    • Department of MineralogyThe Natural History Museum
  • T. E. Jeffries
    • Department of MineralogyThe Natural History Museum
  • V. V. Sharygin
    • Institute of Geology and Mineralogy, Siberian BranchRussian Academy of Sciences
Minerals and Parageneses of Minerals

DOI: 10.1134/S1075701509070095

Cite this article as:
Zaitsev, A.N., Keller, J., Spratt, J. et al. Geol. Ore Deposits (2009) 51: 608. doi:10.1134/S1075701509070095


Alkali carbonates nyerereite, ideally Na2Ca(CO3)2 and gregoryite, ideally Na2CO3, are the major minerals in natrocarbonatite lavas from Oldoinyo Lengai volcano, northern Tanzania. They occur as pheno- and microphenocrysts in groundmass consisting of fluorite and sylvite; nyerereite typically forms prismatic crystals and gregoryite occurs as round, oval crystals. Both minerals are characterized by relatively high contents of various minor elements. Raman spectroscopy data indicate the presence of sulfur and phosphorous as (SO4)2− and (PO4)3− groups. Microprobe analyses show variable composition of both nyerereite and gregoryite. Nyerereite contains 6.1–8.7 wt % K2O, with subordinate amounts of SrO (1.7–3.3 wt %), BaO (0.3–1.6 wt %), SO3 (0.8–1.5 wt %), P2O5 (0.2–0.8 wt %) and Cl (0.1–0.35 wt %). Gregoryite contains 5.0–11.9 wt % CaO, 3.4–5.8 wt % SO3, 1.3–4.6 wt % P2O5, 0.6–1.0 wt % SrO, 0.1–0.6 wt % BaO and 0.3–0.7 wt % Cl. The content of F is below detection limits in nyerereite and gregoryite. Laser ablation ICP-MS analyses show that REE, Mn, Mg, Rb and Li are typical trace elements in these minerals. Nyerereite is enriched in REE (up to 1080 ppm) and Rb (up to 140 ppm), while gregoryite contains more Mg (up to 367 ppm) and Li (up to 241 ppm) as compared with nyerereite.

Copyright information

© Pleiades Publishing, Ltd. 2009