...Tibor Guzmics; Márta Berkesi; Robert J. Bodnar; András Fall; Enikő Bali; Ralf Milke; Enikő Vetlényi; Csaba Szabó Abstract Earth’s only active natrocarbonatite volcanism, occurring at Oldoinyo Lengai (OL), Tanzania, suggests that natrocarbonatite melts are formed through a unique geological process...

...Anatoly N. Zaitsev; Jörg Keller; John Spratt; Elena N. Perova; Anton Kearsley Abstract Samples of natrocarbonatite showing various degrees of alteration are preserved in an older carbonatite platform that existed before and until the 1917 explosive eruption at Oldoinyo Lengai volcano, in Tanzania...

... quenched trachytoidal and flow-banded textures and consist largely (90%) of calcite, plus apatite and magnetite. The principal primary constituent is inferred to have been nyerereite (cf. the natrocarbonatite of Oldoinyo Lengai) now pseudomorphed by calcite, and accompanied by primary tabular calcite...

...B. T. NGWENYA; D. K. BAILEY Abstract Fine grained carbonatite in the Kaluwe complex has been inferred, on textural grounds, to be calcified natrocarbonatite. Electron microprobe analysis, however, shows that the brown laths thought to be pseudo-nyerereite are dolomitic, with Sr values much higher...

... of premodern natrocarbonatite volcanism. The principal carbonate mineral was nyerereite, which is the dominant mineral in modern natrocarbonatite lava flows of the adjacent volcano Oldoinyo Lengai. The nyerereite of Kerimasi was leached of its alkalis by meteoric water and is now represented by calcite...

... indicate that the Tinderet carbonatites are similar to natrocarbonatites from the Oldoinyo Lengai and Kerimasi volcanoes that have altered and recrystallized to form calcite carbonatites. These data support the hypothesis that some of the Tinderet carbonatites were originally alkali-rich rocks which...

...Jörg Keller; Anatoly N. Zaitsev Abstract Carbonatite dykes are described for the first time from the active natrocarbonatite volcano Oldoinyo Lengai, Tanzania. The dykes are fine grained, with a microporphyritic texture of polycrystalline, granular calcite microphenocrysts. The porous texture...

...J. Gittins; B. C. Jago Abstract Natrocarbonatite magma, erupted as lava flows in the Tanzanian volcano Oldoinyo Lengai in June and November of 1988, has evolved chemically since its formation. The June and November flows of 1988 display increasing Cl, F, Ba, K, Mg and Mn, concomitantly with Na, Ca...

...Andrew D. Beard; Kieren Howard; Laura Carmody; Adrian P. Jones Abstract We report new observations of a clathrate mineral, melanophlogite [46SiO 2 ·6(N 2 ,CO 2 )·2(CH 4 ,N 2 )], as part of a tuffaceous layer within a sample of the 2006 natrocarbonatite lava, whose composition reflects the typical...

...B. C. Jago; J. Gittins Several K-Fe sulphide minerals have been described from natrocarbonatite lavas erupted from the Tanzanian volcano Oldoinyo Lengai but uncertainty remains about their exact identity. They do not appear to be any of the established K-Fe sulphides according to Dawson et al...

... natrocarbonatite lava that has been erupted in more recent times. This proposition is difficult to reconcile with the currently fashionable hypothesis whereby the natrocarbonatite lava separated immiscibly from a type of nephelinite magma, most recently thought to be a wollastonite nephelinite. In 1993 Dawson...

.... & Fallick, A. E. in press. Petrology and geochemistry of Oldoinyo Lengai lavas, extruded November, 1988: Magma source, ascent and crystallisation. In : Bell, K. & Keller, J. (eds) Carbonatite volcanism of Oldoinyo Lengai and petrogenesis of natrocarbonatite. IAVCEI Proceedings in Volcanology...

...R. H. Mitchell Abstract Stalactites formed by the chemical weathering of natrocarbonatite lava decorate the roofs of hollow inactive hornitos at Oldoinyo Lengai, Tanzania. The stalactites are composed principally of trona with lesser and very variable amounts of nahcolite, (NaHCO 3 ), thermonatrite...

...R. H. Mitchell Abstract Lapilli formed by a Strombolian eruption are associated with the formation of a large lava flow of natrocarbonatite on or about 21–22 July, 2000 at Oldoinyo Lengai volcano, Tanzania. Fresh lapilli consist of vesicular natrocarbonatite similar to that occurring in rapidly...

...Roger H. Mitchell Abstract Porphyritic natrocarbonatite lavas erupted from the Oldoinyo Lengai volcano (Tanzania) on 17 October 1995 and 15-19 December 1995 differ from previously studied lavas in that they preserve textures indicative of groundmass carbonate-carbonate immiscibility. The immiscible...

...R. H. Mitchell Abstract Natrocarbonatite lavas erupted from hornitos T37B and T49B at Oldoinyo Lengai (Tanzania) during 23–30 July, 2000 are unusual in containing sylvite and fluorite microcrysts together with fluorite-nyerereite intergrowths. The latter are relatively coarse grained and exhibit...

...F ig . 12. Compositions of ferroan alabandite occurring in natrocarbonatites erupted in August 2003 and July 2002 plotted in the ternary Fe-Mn-S system (atomic %). All data this work. ...