Putative primary magnetite in banded iron formations: an experimental approach

Dr Li, Yiliang   (Principal Investigator (PI))

Professor Chan Lung Sang   (Co-Investigator)

36

2017-01-01

359406

Putative primary magnetite in banded iron formations: an experimental approach

banded iron formation, evolution of biosphere, Fe isotopes, magnetite, photoferrotrophy

Earth Sciences,Planetary Sciences

Physical Sciences (P)

17312016

General Research Fund (GRF)

2016

Completed

1 The accurate crystallo-chemistry of magnetite from BIFs of Archean-Palaeoproterozoic eons. The chemical composition will be measured by electron microprobe and the Fe(II)/Fe(III) stoichiometry will be measured by Mössbauer spectrometer at the Department of Earth Sciences. XRD measurements of purified magnetite crystals will be used to calculate their accurate lattice constants. 2 Using electron backscatter diffraction (EBSD) to measure the heterogenesity of euhedral magnetite crystals of about 30 um in BIFs that have different genetic environments. The result of this objective will be used to explain why Fe-isotopic studies without detailed mineralogical information could only provide ambiguous explanations. 3 Wet-chemical methods in the Geobiology Laboratory to measure Fe(II) and Fe(III) concentrations in various solid and aqueous samples by spectrophotometer. Standard curves of spectrophotometric measurements of solution with a wide range of soluble Fe(II) to Fe(III) ratios will be established. 4 The characterization of ferric oxides produced in the environmental sites of Gallionella sp. and from laboratory culturing of nitrate-reducing coupled Fe(II)-oxidation by high resolution SEM and TEM observations. The same materials will be used for synthesizing GR and magnetite afterwards. 5 Synthesis and characterization of GR synthesized at different temperatures and pH conditions. The kinetic evolution from the fibrous structure to the intermediate GR phases, and the final production of magnetite will be captured by SEM and TEM observations. This study also includes a system with the addition of siliceous acid to trace the formation of Si-containing magnetite by this pathway. 6 The measurement of Fe(II) and Fe(III) species separated from magnetite from various BIFs, wet-chemical synthesis and those from biomass of Gallionella sp. and culture of bacteria with nitrate-reducing coupled Fe(II)-oxidation. 7 Synthesis of silician magnetite via the GR pathway. The determination of the structural stoichiometry of Si on the lattice of magnetite from BIFs and experimental systems. The measurement of Si-isotopes of the aqueous-magnetite in experimental systems and the magnetite-hematite-chert system of BIFs.