Strontium Isotope Studies of Alkalic Rocks: The Active Carbonatite Volcano Oldoinyo Lengai, Tanzania

Research Article| March 01, 1973 Strontium Isotope Studies of Alkalic Rocks: The Active Carbonatite Volcano Oldoinyo Lengai, Tanzania KEITH BELL; KEITH BELL 1Department of Physics, University of Toronto, Toronto, Ontario, Canada Search for other works by this author on: GSW Google Scholar J. B. DAWSON; J. B. DAWSON 2Department of Geology, University of St. Andrews, Scotland Search for other works by this author on: GSW Google Scholar R. M. FARQUHAR R. M. FARQUHAR 3Department of Physics, University of Toronto, Toronto, Ontario, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information KEITH BELL 1Department of Physics, University of Toronto, Toronto, Ontario, Canada J. B. DAWSON 2Department of Geology, University of St. Andrews, Scotland R. M. FARQUHAR 3Department of Physics, University of Toronto, Toronto, Ontario, Canada Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1973) 84 (3): 1019–1030. https://doi.org/10.1130/0016-7606(1973)84<1019:SISOAR>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation KEITH BELL, J. B. DAWSON, R. M. FARQUHAR; Strontium Isotope Studies of Alkalic Rocks: The Active Carbonatite Volcano Oldoinyo Lengai, Tanzania. GSA Bulletin 1973;; 84 (3): 1019–1030. doi: https://doi.org/10.1130/0016-7606(1973)84<1019:SISOAR>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Sr isotopic ratios as well as Rb, Sr, and K abundances are reported for 16 samples of lava and 12 ejected plutonic blocks from the active carbonatite volcano Oldoinyo Lengai, northern Tanzania. Lava and plutonic blocks together exhibit a range of Sr87/Sr86 ratios from 0.7033 to 0.7096. Phonolitic lava exhibits the same range as nephelinite, while two specimens of the sodium carbonatite lava have ratios of 0.7059 and 0.7061, similar to many of the silicate lavas. The Sr87/Sr86 ratios of the lava cannot be correlated with any other geochemical parameter or with their position in the extrusion cycle. Ejected plutonic blocks have isotopic ratios similar to or slightly lower than the lava samples and generally contain smaller amounts of K, Rb, and Sr.Similarity in Sr isotopic composition and K/Rb ratios between the phonolite and nephelinite suggests that the more silicic phonolite is not rheomorphic fenite.Correlation coefficients between several major oxides and trace elements indicate the presence of two groups, one high in Al2O2, SiO2, and Th, and another enriched in CaO, K2O, Na2O, P2O5, and Sr.Sr isotopic ratios of four specimens of evaporites from Lake Natron and Lake Magadi vary between 0.7045 and 0.7114 and are, within limits of experimental error, similar to the values from the carbonatite and silicate lavas. These are discussed in terms of the overall petrogenesis of the Oldoinyo Lengai lavas. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.