A HREM study of the intergrowth of magnetite and coulsonite

Abstract

The microstructures of magnetite containing vanadium and titanium, found in Sichuam province, China, have been studied by hi_gh-resolution electron microscopy (HREM). The [110] structural images showed a multiply intimate intergrowth of magnetite and coulsonite as a result of exsolution along the [ 110] direction instead of the [ 111 ] direction as reported previously. The detectable different contrast of the two phases was confirmed by image simulation. The antiphase domain and various stacking faults related to the nonstoichiometry of the transitionmetal oxide in the same direction were also observed in magnetite and coulsonite, respectively. The possible genetic aspect and formation of these defects on exsolution are also considered. Oclh = 0.03 rad/~-!; and the size limited by the objective aperture, (sin 0)/h = 0.350 A-1. From the simulated images it is known that at a thickness from 50 0108-7673/89/040264-05503.00 AbstractThe structure of hexagonal Frank-Kasper (FK) phases can be described by the projection of the seven-dimensional (7D) Cr3Si and Zr4A13 cubes in a suitable projection subspace onto a 3D hyperplane. The close relationship between hexagonal FK phases and the dodecagonal quasicrystal with 12-fold rotational symmetry is discussed.

Combinatorial modular design of the structures of spinel-type phases

“…7) [79] and the aforementioned β phase, respectively. Similar spinelloid phases were also experimentally revealed in other systems [80][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95][96] [87][88][89][90][91][92][93][94][95][96].…”

“…For example, halite MgO and olivine Mg 2 GeO 4 are modules in the structures of the (Mg,Ni) 10 [85,113,114]; halite MgO and β-Ga 2 O 3 are modules in the structure of the compound Mg 7 Ga 2 GeO 12 [115]; and the oxides FeO and Fe 2 O 3 are modules in the structure of the magnetite Fe 3 O 4 (Fig. 13) [22,96,116].…”

“…Alternation of polyhedral layers consisting of (1) the FeO oxide modules (octahedra) and (2) the Fe 2 O 3 oxide modules (octahedra, tetrahedra) in the structure of the Fe 3 O 4 magnetite[96].…”

Nanoscale Study of Titanomagnetite from the Panzhihua Layered Intrusion, Southwest China: Multistage Exsolutions Record Ore Formation

“…Various attempts have been undertaken to relate titanomagnetite with different types of intergrowths to the oxide content in host rocks [33], silicate disequilibrium, and variation of f O 2 and H 2 O content in the parent magma [36], or prolonged cooling history resulting in distinct exsolution mechanisms: (i) ulvöspinel exsolution and oxidation; (ii) oxy-exsolution of ilmenite; (iii) direct ilmenite unmixing from titanomagnetite; and (iv) rebalancing processes between the various oxides, including Al, Mg, and Zn-bearing spinels [15]. Titanomagnetite from Panzhihua has been studied by high-resolution (HR) transmission electron microscopy (TEM), showing relationships with coulsonite (Fe 2+ V 3+ 2 O 4 ) [37]. The presence of wüstite has been determined based on electron diffraction patterns [38].…”

The defects and intergrowth of lead oxides revealed by HRTEM

“…The resolutions attainable in modern instruments allow details to be seen on an extremely fine scale, even to an atomic level (Buseck & Veblen, 1981). The defects, exsolution and intergrowth of silicates and some oxides and the superlattices related to the ordering arrangement of iron vacancies in laihunite have been studied in detail 0021-8898/92/020199-06503.00 (Buseck, 1983;Wang, Ye, Ximen & Kuo, 1989;Zou & Kuo, 1986). The defect structure of lead dioxide was investigated by Moseley, Hutchison & Bourke (1982).…”