| Инд. авторы: | Zaitsev A.N., Keller J., Spratt J., Jeffries T.E., Sharygin V.V. |
| Заглавие: | Chemical composition of nyerereite and gregoryite from natrocarbonatites of Oldoinyo Lengai volcano, Tanzania |
| Библ. ссылка: | Zaitsev A.N., Keller J., Spratt J., Jeffries T.E., Sharygin V.V. Chemical composition of nyerereite and gregoryite from natrocarbonatites of Oldoinyo Lengai volcano, Tanzania // Geology of Ore Deposits. - 2009. - Vol.51. - Iss. 7. - P.608-616. - ISSN 1075-7015. - EISSN 1555-6476. |
| Внешние системы: | DOI: 10.1134/S1075701509070095; SCOPUS: 2-s2.0-77949680125; |
| Реферат: | eng: 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. © Pleiades Publishing, Ltd., 2009.
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| Ключевые слова: | Microprobe analysis; Minor elements; Natrocarbonatite; Nyerereite; Oldoinyo Lengai; Prismatic crystals; Tanzania; Ablation; Alkalinity; Crystals; Inductively coupled plasma mass spectrometry; Manganese; Manganese compounds; Phosphorus; Raman spectroscopy; Rubidium; Sodium; Sulfur; Trace analysis; Trace elements; Volcanoes; Minerals; carbonate group; carbonatite; chemical composition; crystal structure; electron probe analysis; lava; Raman spectroscopy; trace element; Oldoinyo Lengai; Tanzania; Calcium; High-content; Detection limits; Chemical compositions; Laser-ablation-ICP-MS; Alkali carbonate; |
| Издано: | 2009 |
| Физ. характеристика: | с.608-616 |