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Unmixed spinel in chromitite from the Iwanai-dake peridotite complex, Hokkaido, Japan: A reaction between peridotite and highly oxidized magma in the mantle wedge
-
Akihiro Tamura
und
Shoji Arai
Veröffentlicht/Copyright:
28. März 2015
Abstract
Spinel [(Mg, Fe2+)(Cr, Al, Fe3+)2O4] with an inhomogeneous texture was observed in a chromitite section from the Iwanai-dake complex, Hokkaido, Japan, which mainly consists of highly depleted Alpine-type peridotite. The inhomogeneous spinel identified under reflected-light microscopy has speckled and symplectic textures in the chromitite layer adjacent to dunite. On the other hand, spinel in the surrounding dunite and harzburgite is homogeneous. The inhomogeneous spinel comprises two different phases: an MgAl-rich spinel and an Fe-rich spinel with wide variation of Cr content. The compositional relationships of contiguous phases correspond to the solvus at 600 °C, which suggest that the inhomogeneous spinel was formed by an unmixing process due to the miscibility gap between Al-rich and Fe3+-rich phases. The original spinel composition in the chromitite layer, estimated from bulk spinel composition, is intermediate between magnesioferrite (MgFe23+O4) and magnetite (Fe2+Fe23+O4). Such an Fe3+-rich spinel composition indicates that the chromitite was formed under highly oxidized conditions at magmatic temperatures. A highly oxidized hydrous silicate melt, such as minette or absarokite, generated by melting of hydrous mantle, possibly reacted with peridotite in the mantle wedge and crystallized the Fe3+-rich spinel.
Received: 2003-12-4
Accepted: 2004-10-18
Published Online: 2015-3-28
Published in Print: 2005-2-1
© 2015 by Walter de Gruyter Berlin/Boston
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Artikel in diesem Heft
- Comparative planetary mineralogy: Valence state partitioning of Cr, Fe, Ti, and V among crystallographic sites in olivine, pyroxene, and spinel from planetary basalts
- The origin of orthopyroxene/biotite + plagioclase coronas from the Bolangir anorthosite complex (India), and implications for reconstructing P-T paths
- Dellaventuraite, NaNa2(MgMn23+Ti4+Li)Si8O22O2, a new anhydrous amphibole from the Kajlidongri Manganese Mine, Jhabua District, Madhya Pradesh, India
- Successive zoning of Al and H in hydrothermal vein quartz
- The Ti-saturation surface for low-to-medium pressure metapelitic biotites: Implications for geothermometry and Ti-substitution mechanisms
- Thermochemistry of hydrotalcite-like phases in the MgO-Al2O3-CO2-H2O system: A determination of enthalpy, entropy, and free energy
- Igneous thermometers and barometers based on plagioclase + liquid equilibria: Tests of some existing models and new calibrations
- Thermodynamic properties of the Tschermak solid solution in Fe-chlorite: Application to natural examples and possible role of oxidation
- Experimental data on the Tschermak substitution in Fe-chlorite
- Nanometer-sized, divalent-Mn, hydrous silicate domains in geothermal brine precipitates
- Geometric crystal chemical models for structural analysis of micas and their stacking polytypes
- Fundamental difference between synthetic powder and natural or synthetic single-crystal 1M micas: Geometric homo-octahedral vs. geometric meso-octahedral sheets
- The crystal structures of synthetic Fe2(SO4)3(H2O)5 and the type specimen of lausenite
- Experimental study of plagioclase rim growth around anorthite seed crystals in rhyodacitic melt
- Luminescence study of defects in synthetic as-grown and HPHT diamonds compared to natural diamonds
- Molar absorptivities of OH and H2O in rhyolitic glass at room temperature and at 400600 °C
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- Oxygen isotope heterogeneities and diffusion profile in composite metamorphic-magmatic garnets from the Pyrenees
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- Mn-bearing “oxy-rossmanite” with tetrahedrally coordinated Al and B from Austria: Structure, chemistry, and infrared and optical spectroscopic study
- Geochemical applications of the simple salt approximation to the lattice energies of complex materials
- Letter: A method for controlling alkali-metal oxide activities in one-atmosphere experiments and its application to measuring the relative activity coeficients of NaO0.5 in silicate melts
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- Letter: Ferrous hydroxy carbonate is a stable transformation product of biogenic magnetite
