Silician magnetite from the Dales Gorge Member of the Brockman Iron Formation, Hamersley Group, Western Australia
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Jason M. Huberty
,
Hiromi Konishi
Abstract
We report silician magnetite from banded iron formation (BIF) in the Dales Gorge Member of the Brockman Iron Formation, Hamersley Group, Western Australia. Magnetite mesobands typically consisting of individual ~100 μm microlaminae are revealed to be composed of silician magnetite overgrowths on magnetite. Silician magnetite overgrowths contain from 1 to 3 wt% SiO2, whereas (low-Si) magnetite domains contain less than 1 wt% SiO2. Silicon solid solution is present in the magnetite crystal lattice as determined by in situ micro-X-ray diffraction and high-resolution transmission electron microscopy. Three textures are distinguished in magnetite mesobands: (1) magnetite sub-microlaminae with silician magnetite overgrowths, (2) recrystallized magnetite fragments with silician magnetite overgrowths, and (3) a complex intergrowth of magnetite and silician magnetite. All three textures are found in magnetite mesobands from the BIF4-5 and BIF12-16 macrobands of the Dales Gorge type-section drill core DDH-47A from Wittenoom, Western Australia. Magnetite domains contain numerous submicrometer-to-micrometer inclusions of quartz, carbonate, stilpnomelane, and apatite, whereas silician magnetite overgrowths are devoid of mineral inclusions. The presence of mineral inclusions in magnetite indicates the BIF oxide precipitate was not chemically pure iron oxyhydroxide/oxide. Magnetite domains display textures formed during soft sediment deformation that are the earliest and best preserved relict sedimentary structures in this BIF. Silician magnetite is the dominant iron oxide in the Dales Gorge BIF and is present in many other sub-greenschist facies BIFs worldwide. We suggest the former presence of organic matter creates reducing conditions necessary to stabilize silician magnetite. Thus, silician magnetite is a potential biosignature in BIFs.
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
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- Insights into the crystal and aggregate structure of Fe3+ oxide/silica co-precipitates
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- X-ray absorption near edge structure (XANES) study of the speciation of uranium and thorium in Al-rich CaSiO3 perovskite
- Rehydration of dehydrated-dehydroxylated smectite in a low water vapor environment
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Articles in the same Issue
- Boron in natural type IIb blue diamonds: Chemical and spectroscopic measurements
- Mejillonesite, a new acid sodium, magnesium phosphate mineral, from Mejillones, Antofagasta, Chile
- Silician magnetite from the Dales Gorge Member of the Brockman Iron Formation, Hamersley Group, Western Australia
- The mechanism of thermal decomposition of dolomite: New insights from 2D-XRD and TEM analyses
- A revised diamond-graphite transition curve
- Insights into the crystal and aggregate structure of Fe3+ oxide/silica co-precipitates
- Compositional dependence of alkali diffusivity in silicate melts: Mixed alkali effect and pseudo-alkali effect
- Kinetics of evaporation of forsterite in vacuum
- X-ray absorption near edge structure (XANES) study of the speciation of uranium and thorium in Al-rich CaSiO3 perovskite
- Rehydration of dehydrated-dehydroxylated smectite in a low water vapor environment
- Effect of high pressure on the crystal structure and electronic properties of magnetite below 25 GPa
- OH group behavior and pressure-induced amorphization of antigorite examined under high pressure and temperature using synchrotron infrared spectroscopy
- Single-crystal Raman spectroscopy of natural paulmooreite Pb2As2O5 in comparison with the synthesized analog
- The dissolution of laumontite in acidic aqueous solutions: A controlled-temperature in situ atomic force microscopy study
- Crystal structure of CaRhO3 polymorph: High-pressure intermediate phase between perovskite and post-perovskite
- Oxide melt solution calorimetry of Fe2+-bearing oxides and application to the magnetite–maghemite (Fe3O4–Fe8/3O4) system
- Static compression of (Mg0.83,Fe0.17)O and (Mg0.75,Fe0.25)O ferropericlase up to 58 GPa at 300, 700, and 1100 K
- Implications of ferrous and ferric iron in antigorite
- Markascherite, Cu3(MoO4)(OH)4, a new mineral species polymorphic with szenicsite, from Copper Creek, Pinal County, Arizona, U.S.A.
- Natural hydrous amorphous silica: Quantitation of network speciation and hydroxyl content by 29Si MAS NMR and vibrational spectroscopy
- Lead-tellurium oxysalts from Otto Mountain near Baker, California: VII. Chromschieffelinite, Pb10Te6O20(OH)14(CrO4)(H2O)5, the chromate analog of schieffelinite
- Experimental growth of diopside + merwinite reaction rims: The effect of water on microstructure development
- Thermodynamic model for growth of reaction rims with lamellar microstructure
- The high-pressure behavior of micas: Vibrational spectra of muscovite, biotite, and phlogopite to 30 GPa
- Critical evaluation of the revised akdalaite model for ferrihydrite—Discussion
- Critical evaluation of the revised akdalaite model for ferrihydrite—Reply
