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.

Carbonate-carbonate immiscibility, neighborite and potassium iron sulphide in Oldoinyo Lengai natrocarbonatite

1997 ◽  
Vol 61 (409) ◽  
pp. 779-789 ◽  
Author(s):  
Roger H. Mitchell
Keyword(s):  
Solid Solution ◽  
Compositional Data ◽  
Iron Sulphide ◽  
Oldoinyo Lengai ◽  
Group Mineral ◽  
Primitive Magma ◽  
Highly Evolved

AbstractPorphyritic 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 fractions are considered to involve: a Na-K-Ca-CO2-Cl-rich, F-bearing fluid crystallizing gregoryite, sodian sylvite, potassium neighborite as well as a complex Ba-rich carbonate; and a Na-rich, Cl-poor carbonate liquid approximating to a nyerereite-gregoryite cotectic composition. Compositional data are given for potassium neighborite, this mineral being the first recognized occurrence of a fluorine-based perovskite group mineral in a magmatic environment. New compositional data are also given for a previously recognized potassium iron sulphide which indicate that this phase is probably a solid solution between the ternary sulphides, KFe3S4, K2Fe3S4, and KFe2S3. Textural and paragenetic data are interpreted to suggest that these recent lavas are more evolved than previously investigated Oldoinyo Lengai lavas and that natrocarbonatite is a highly evolved rather than a primitive magma.

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

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.

Correction to "Ascending seismic source during an explosive eruption at Tungurahua volcano, Ecuador”

2011 ◽  
Author(s):  
Hiroyuki Kumagai ◽  
Pablo Placios ◽  
Mario Ruiz ◽  
Hugo Yepes ◽  
Tomofumi Kozono
Keyword(s):  
Explosive Eruption ◽  
Seismic Source ◽  
Tungurahua Volcano

Droplet Factories: Synthesis and Assembly of Silver and Palladium Nanoparticles at the Liquid-Liquid Interface

2019 ◽  
Author(s):  
Suchanuch Sachdev ◽  
Rhushabh Maugi ◽  
Sam Davis ◽  
Scott Doak ◽  
Zhaoxia Zhou ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Reaction Rate ◽  
Tertiary Structure ◽  
Flow Reactor ◽  
Pd Nanoparticles ◽  
Subsequent Removal ◽  
Immiscible Liquids ◽  
Flow Reactors ◽  
Droplet Flow ◽  
One Step

<div>The interface between two immiscible liquids represent an ideal substrate for the assembly of nanomaterials. The defect free surface provides a reproducible support for creating densely packed ordered materials. Here a droplet flow reactor is presented for the synthesis and/ or assembly of nanomaterials at the interface of the emulsion. Each droplet acts as microreactor for a reaction between decamethylferrocene (DmFc) within the hexane and metal salts (Ag+/ Pd2+) in the aqueous phase. The hypothesis was that a spontaneous, interfacial reaction would lead to the assembly of nanomaterials creating a Pickering emulsion. The subsequent removal of the solvents showed how the Ag nanoparticles were trapped at the interface and retain the shape of the droplet, however the Pd nanoparticles were dispersed with no tertiary structure. To further exploit this, a one-step process where the particles are synthesised and then assembled into core-shell materials was proposed. The same reactions were performed in the presence of oleic acid stabilise Iron oxide nanoparticles dispersed within the hexane. It was shown that by changing the reaction rate and ratio between palladium and iron oxide a continuous coating of palladium onto iron oxide microspheres can be created. The same reaction with silver, was unsuccessful and resulted in the silver particles being shed into solution, or incorporated within the iron oxide micro particle. These insights offer a new method and chemistry within flow reactors for the creation of palladium and silver nanoparticles. We use the technique to create metal coated iron oxide nanomaterials but the methodology could be easily transferred to the assembly of other materials.</div><div><br></div>

Seeded Growth of Single-Crystal Two-Dimensional Covalent Organic Frameworks

2017 ◽  
Author(s):  
Austin M. Evans ◽  
Lucas R. Parent ◽  
Nathan C. Flanders ◽  
Ryan P. Bisbey ◽  
Edon Vitaku ◽  
...  
Keyword(s):  
Molecular Transport ◽  
Controlled Synthesis ◽  
Two Dimensional ◽  
Covalent Organic Frameworks ◽  
Seeded Growth ◽  
Covalent Bonds ◽  
Crystalline Materials ◽  
Step Procedure ◽  
Structures And Properties ◽  
2D Polymer

<div> <div> <div> <p>Polymerizing monomers into periodic two-dimensional (2D) networks provides structurally precise, atomically thin macromolecular sheets linked by robust, covalent bonds. These materials exhibit desirable mechanical, optoelectrotronic, and molecular transport properties derived from their designed structure and permanent porosity. 2D covalent organic frameworks (COFs) offer broad monomer scope, but are generally isolated as polycrystalline, insoluble powders with limited processability. Here we overcome this limitation by controlling 2D COF formation using a two- step procedure. In the first step, 2D COF nanoparticle seeds are prepared with approximate diameters of 30 nm. Next, monomers are slowly added to suppress new nucleation while promoting epitaxial growth on the existing seeds to sizes of several microns. The resulting COF nanoparticles are of exceptional and unprecedented quality, isolated as single crystalline materials with micron-scale domain sizes. These findings advance the controlled synthesis of 2D layered COFs and will enable a broad exploration of synthetic 2D polymer structures and properties. </p> </div> </div> </div>

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