Jörgkellerite, Na3Mn3+ 3(PO4)2(CO3)O2·5H2O, a new layered phosphate-carbonate mineral from the Oldoinyo Lengai volcano, Gregory rift, northern Tanzania

2016 ◽  
Vol 111 (3) ◽  
pp. 373-381 ◽  
Author(s):  
Anatoly N. Zaitsev ◽  
Sergey N. Britvin ◽  
Anton Kearsley ◽  
Thomas Wenzel ◽  
Caroline Kirk
Keyword(s):  
Carbonate Mineral ◽  
Oldoinyo Lengai ◽  
Northern Tanzania ◽  
Layered Phosphate ◽  
Phosphate Carbonate

Alumoåkermanite, (Ca,Na)2(Al,Mg,Fe2+)(Si2O7), a new mineral from the active carbonatite-nephelinite-phonolite volcano Oldoinyo Lengai, northern Tanzania

2009 ◽  
Vol 73 (3) ◽  
pp. 373-384 ◽  
Author(s):  
D. Wiedenmann ◽  
A. N. Zaitsev ◽  
S. N. Britvin ◽  
S. V. Krivovichev ◽  
J. Keller
Keyword(s):  
Crystal Structure ◽  
Structure Refinement ◽  
New Mineral ◽  
Crystal Structure Refinement ◽  
Chemical Formula ◽  
Oldoinyo Lengai ◽  
Structure Topology ◽  
Northern Tanzania ◽  
Mohs Hardness ◽  
Measured Density

AbstractAlumoåkermanite, (Ca,Na)2(Al,Mg,Fe2+)(Si2O7), is a new mineral member of the melilite group from the active carbonatite-nephelinite-phonolite volcano Oldoinyo Lengai, Tanzania. The mineral occurs as tabular phenocrysts and microphenocrysts in melilite-nephelinitic ashes and lapilli-tuffs. Alumoåkermanite is light brown in colour; it is transparent, with a vitreous lustre and the streak is white. Cleavages or partings are not observed. The mineral is brittle with an uneven fracture. The measured density is 2.96(2) g/cm3. The Mohs hardness is ~4.5–6. Alumoåkermanite is uniaxial (–) with ω = 1.635(1) and ε = 1.624–1.626(1). In a 30 mm thin section (+N), the mineral has a yellow to orange interference colour, straight extinction and positive elongation, and is nonpleochroic. The average chemical formula of the mineral derived from electron microprobe analyses is: (Ca1.48Na0.50Sr0.02 K0.01)(Si1.99Al0.01O7). Alumoåkermanite is tetragonal, space group P421m with a = 7.7661(4) Å, c = 5.0297(4) Å, V = 303.4(1) Å3 and Z = 2. The five strongest powder-diffraction lines [d in Å, (I/Io), hkl] are: 3.712, (13), (111); 3.075, (25), (201); 2.859, (100), (211); 2.456, (32), (311); 1.757, (19), (312). Single-crystal structure refinement (R1 = 0.018) revealed structure topology typical of the melilite-group minerals, i.e. tetrahedral [(Al,Mg)(Si2O7)] sheets interleaved with layers of (CaNa) cations. The name reflects the chemical composition of the mineral.

scholarly journals Alumoåkermanite, (Ca,Na)2(AI,Mg,Fe2+)(Si2O7), a new mineral from the active carbonatite-nephelinite-phonolite volcano Oldoinyo Lengai, northern Tanzania

2009 ◽  
Vol 73 (6) ◽  
pp. 1063-1063
Author(s):  
D. Wiedenmann ◽  
A. N. Zaitsev ◽  
S. N. Britvin ◽  
S. V. Krivovichev ◽  
J. Keller
Keyword(s):  
New Mineral ◽  
Oldoinyo Lengai ◽  
Northern Tanzania

1966 ash eruption of the carbonatite volcano Oldoinyo Lengai: mineralogy of lapilli and mixing of silicate and carbonate magmas

1992 ◽  
Vol 56 (382) ◽  
pp. 1-16 ◽  
Author(s):  
J. B. Dawson ◽  
J. V. Smith ◽  
I. M. Steele
Keyword(s):  
Explosive Eruption ◽  
Controlled Synthesis ◽  
Iron Sulphide ◽  
Oldoinyo Lengai ◽  
Immiscible Liquids ◽  
Incomplete Reaction ◽  
Phosphate Carbonate

AbstractLapilli from the August 1966 eruption of the carbonatite volcano Oldoinyo Lengai consist of carbonate-cemented aggregates of (i) mono- and poly-mineralic fragments of ijolitic rocks, (ii) single grains and clusters of euhedral nepheline, Ti-andradite, and Ti-magnetite, and (iii) corroded pyroxene and wollastonite grains surrounded by coronas containing combeite, melilite, Ca-silicates (possibly larnite and rankinite), and rounded bodies of submicrometre intergrowths with complex bulk compositions dominated by Na,K,Ca-phosphate-carbonate and alkali-iron-sulphide-carbonate. The (ii,iii) materials, together with abundant Na-carbonate, sylvite and fluorite occurring as cement and shells in the lapilli, are attributed to mixing and incomplete reaction of ijolite and carbonatite magmas during the explosive eruption. The rounded submicrometre intergrowths are interpreted as the quench products of two types of immiscible liquids whose properties should be studied by controlled synthesis.

An ephemeral pentasodium phosphate carbonate from natrocarbonatite lapilli, Oldoinyo Lengai, Tanzania

2006 ◽  
Vol 70 (2) ◽  
pp. 211-218 ◽  
Author(s):  
R. H. Mitchell
Keyword(s):  
Low Temperature ◽  
Lava Flow ◽  
Sodium Carbonate ◽  
Sodium Phosphate ◽  
New Mineral ◽  
Atmospheric Conditions ◽  
Oldoinyo Lengai ◽  
Rapid Decomposition ◽  
Strombolian Eruption ◽  
Phosphate Carbonate

AbstractLapilli 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 quenched lavas. The lapilli were altered at low temperature (<50°C) by degassing to aggregates of sodian sylvite, potassian halite, trona, thermonatrite and a novel F-bearing sodium phosphate-carbonate. The latter is considered to be a new mineral as it has a composition (Na5–4.5PO4(CO3,F,Cl) that is not similar to that of nahpoite (Na2HPO4), dorfmanite [Na2(PO3OH).2H2O] or natrophosphate [Na7(PO4)2F.19H2O]. However, in common with these minerals, it is ephemeral and undergoes rapid decomposition under normal atmospheric conditions. The sodium phosphate-carbonate and associated halide-sodium carbonate assemblages are considered to be a part of a previously unrecognized hyperagpaitic assemblage forming as sublimates at Oldoinyo Lengai.

The 24th September 2007 ash eruption of the carbonatite volcano Oldoinyo Lengai, Tanzania: mineralogy of the ash and implications for formation of a new hybrid magma type

2007 ◽  
Vol 71 (5) ◽  
pp. 483-492 ◽  
Author(s):  
R. H. Mitchell ◽  
J. B. Dawson
Keyword(s):  
Sparse Matrix ◽  
Oldoinyo Lengai ◽  
Magma Type ◽  
Free Particles ◽  
Alkali Carbonate ◽  
Phosphate Carbonate

AbstractThe September 2007 ash eruption at Oldoinyo Lengai terminated a period of >30 y of relatively quiet extrusion of natrocarbonatite lavas. Ash erupted on the 24th September comprised nuclei of ijolitic phases, surrounded by finer peralkaline, silica-undersaturated material. The mantling material, as well as that forming nucleus-free particles, is dominated by nepheline, Ti-andradite, Na-melilite, combeite and a Na-Ca-phosphate-carbonate with minor amounts of K-Fe-sulphide and Mn-magnetite in a sparse matrix of alkali carbonate. The absence of clinopyroxene precludes this material from being termed either nephelinite or melilitite. We propose that the material represented by the mantles is an extremely undersaturated, peralkaline hybrid magma resulting from interaction between natrocarbonatite and nephelinite.

Gem-Quality Yellow-Green Haüyne from Oldoinyo Lengai Volcano, Northern Tanzania

2009 ◽  
Vol 45 (3) ◽  
pp. 200-203 ◽  
Author(s):  
Anatoly N. Zaitsev ◽  
Olga A. Zaitseva ◽  
Alexander K. Buyko ◽  
Jörg Keller ◽  
Jurgis Klaudius ◽  
...  
Keyword(s):  
Oldoinyo Lengai ◽  
Northern Tanzania
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