Morphology and microstructure of magnetite and ilmenite inclusions in plagioclase from Adirondack anorthositic gneiss
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Hans-Rudolf Wenk
,
Kai Chen
Abstract
It is well known that oriented iron and titanium oxide inclusions occur in pyroxenes and plagioclase of anorthosites and granulites, and they are attributed to exsolution at subsolidus conditions. The oxides occur as needles or platelets. In this study, we determine the morphology of oxide needles as well as their orientation in plagioclase (An 30-35) in anorthosite gneiss from the Adirondack mountains (New York). The investigation was done with electron backscatter diffraction (EBSD) in a scanning electron microscope, as well as Laue diffraction with a microfocus synchrotron X‑ray beam at the Advanced Light Source in Berkeley. It was observed that the needle direction is [110] in magnetite and [101̅0] in ilmenite. The needle direction is consistently parallel to [001] of plagioclase. Furthermore, (111) of magnetite and (0001) of ilmenite are sub-parallel to (1̅20) and (120) of plagioclase. We note that for directions [110] in the magnetite structure and [101̅0] in ilmenite, O atoms are close-packed, and (111) and (0001) are close-packed planes, correspondingly. In plagioclase, [001] is a direction with open channels as well as approximate alignment of Si tetrahedral edges, thus providing nucleation sites with a coincidence lattice relationship. (120) and (1̅20) in this triclinic mineral are planes with approximate tetrahedral sides so that the relationship is structurally plausible. From Laue diffraction, we can determine that the magnetite needle axis is subject to an extensional stress, most likely attained during cooling of the inclusions within the plagioclase host.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- High-pressure Raman spectroscopic studies of ulvöspinel Fe2TiO4
- Brearleyite, Ca12Al14O32Cl2, a new alteration mineral from the NWA 1934 meteorite
- The 3.65 Å phase in the system MgO-SiO2-H2O: Synthesis, composition, and structure
- Water in upper mantle pyroxene megacrysts and xenocrysts: A survey study
- Mesoscale twinning and crystallographic registers in biominerals
- Radiation effects on cathodoluminescence of albite
- Structure refinement of high-pressure hexagonal aluminous phases K1.00Mg2.00Al4.80Si1.15O12 and Na1.04Mg1.88Al4.64Si1.32O12
- Elastic softening of metamict titanite CaTiSiO5: Radiation damage and annealing
- An experimental study of the diffusion of C and O in calcite in mixed CO2-H2O fluid
- Hydrochemical performance and mineralogical evolution of a dispersed alkaline substrate (DAS) remediating the highly polluted acid mine drainage in the full-scale passive treatment of Mina Esperanza (SW Spain)
- The effect of fO₂ on the partitioning and valence of V and Cr in garnet/melt pairs and the relation to terrestrial mantle V and Cr content
- An experimental study of OH solubility in rutile at 500–900 °C, 0.5–2 GPa, and a range of oxygen fugacities
- The growth interval of garnet in the UHP eclogites from the Dabie orogen, China
- Structural studies of NH4-exchanged natrolites at ambient conditions and high temperature
- Morphology and microstructure of magnetite and ilmenite inclusions in plagioclase from Adirondack anorthositic gneiss
- Thermodynamic properties of stishovite by low-temperature heat capacity measurements and the coesite-stishovite transition boundary
- Mechanisms of Cr and H incorporation in stishovite determined by single-crystal EPR spectroscopy and DFT calculations
- Paramagnetic interactions in the 31P NMR spectroscopy of rare earth element orthophosphate (REPO4, monazite/xenotime) solid solutions
- Garnet sector and oscillatory zoning linked with changes in crystal morphology during rapid growth, North Cascades, Washington
- Phase stability, elastic behavior, and pressure-induced structural evolution of kalsilite: A ceramic material and high-T/high-P mineral
- A new type of high-pressure low-flow metering valve for continuous decompression: First experimental results on degassing of rhyodacitic melts
- Substitution mechanisms and implications for the estimate of water fugacity for Ti-rich phlogopite from Mt. Vulture, Potenza, Italy
- Calibration for IR measurements of OH in apatite
- Electrolytic coloration and spectral properties of natural calcite crystals
- Compositional dependent compressibility of dissolved water in silicate glasses
- In situ monitoring of lepidocrocite bioreduction and magnetite formation by reflection Mössbauer spectroscopy
- Direct determination of europium valence state by XANES in extraterrestrial merrillite: Implications for REE crystal chemistry and martian magmatism
