Magnetic characterization of synthetic titanomagnetites: Quantifying the recording fidelity of ideal synthetic analogs

Trevor P. Almeida*, Adrian R. Muxworthy, Wyn Williams, Takeshi Kasama, Rafal Dunin-Borkowski

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

 series of four synthetic basalts comprising titanomagnetite (Fe3-xTixO4) grains of varied size and titanium content have been produced by a glass-ceramic method. Complementary characterization techniques of X-ray diffractometry, secondary electron microscopy, and transmission electron microscopy (TEM) demonstrate the reaction product composition consisted of mainly Fe3-xTixO4, pyroxene hedenbergite, fayalite, and SiO2. The samples exhibit bimodal distributions of larger (<2 µm) and smaller Fe3-xTixO4 particles (<50 nm in diameter), the latter found inside pyroxene crystals, as well as the sporadic occurance of dendritic Fe3-xTixO4 structures. Magnetic measurements show their bulk characteristics fall into two groups: Ti-rich titanomagnetite samples with varying Ti content; and near-stoichiometric magnetite. The TEM technique of off-axis electron holography allowed for visualization of the magnetic behavior of the synthetic Fe3-xTixO4 grains. Energy dispersive X-ray analysis and off-axis electron holography confirmed the small Fe3-xTixO4 grains (<50 nm) confined within glassy pyroxene regions to be Fe-rich and single domain, carrying strong magnetic signals, compared to the relatively magnetically weak larger Fe3-xTixO4 grains (x ∼ 0.6). The large grains in the pure magnetite sample are shown to be pseudo-single domain in nature. The quenching process involved in synthesis is considered similar to that of pillow basalts found at mid-ocean ridges and hence the reaction products are thought ideal in terms of characterization and understanding, for the purpose of studying natural systems.

Original languageEnglish
Pages (from-to)161-175
Number of pages15
JournalGeochemistry, Geophysics, Geosystems
Volume15
Issue number1
DOIs
Publication statusPublished - Jan 2014

Keywords

  • titanomagnetites
  • palaeomagnetism
  • electron holography
  • OCEAN-FLOOR BASALTS
  • VARIABLE TI-CONTENT
  • RICH TITANOMAGNETITE
  • ELECTRON HOLOGRAPHY
  • FORC DIAGRAMS
  • SINGLE-DOMAIN
  • TEMPERATURE
  • REVERSAL
  • TITANOMAGHEMITES
  • PARTICLES

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