Anomalously high Fe contents in rehomogenized olivine-hosted melt inclusions from oxidized magmas
-
Michael C. Rowe
,
Roger L. Nielsen
Abstract
Iron concentrations in rehomogenized (remelted) melt inclusions hosted in forsterite-rich olivine (Fo88.92) from an alkalic lava have significantly higher Fe contents (FeO* up to 21 wt%) than found in naturally quenched inclusions, matrix glasses, and bulk lava compositions (6.21.6.66 wt% FeO*). The main objectives of this study were to: (1) determine the source of the anomalous Fe concentrations, and (2) evaluate the significance of this signature with respect to rehomogenization of melt inclusions. Heating experiments conducted from 1125 to 1225 °C on crystallized inclusions show that Fe and Mg contents in rehomogenized inclusions increase with homogenization temperature, consistent with dissolution of olivine + magnetite in a 1:1 atomic ratio. The dissolution of magnetite contributes significant excess Fe to the homogenized inclusions, and thus the high FeO* contents of the glasses do not reflect the original composition of the trapped melt. The addition of excess Fe also dilutes the concentrations of other major elements, especially evident in SiO2, Al2O3, and CaO wt%.
Although the cause of magnetite formation in the inclusions is unresolved, two models (H+ diffusion and co-entrapment of magnetite) for the formation of significant volumes of magnetite are considered. One of the most significant conclusions for this study is that magnetite formation occurred prior to rehomogenization and that the magnetite did not result from post-entrapment fractional crystallization of the inclusion. For these inclusions, a correction must be made for the dissolution of magnetite (± pyroxene) and olivine to the silicate melt to accurately reconstruct the original Fe content of the melt.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Dana Lecture. Rates of Fe, Mg, Mn, and Ca diffusion in garnet
- An FTIR study of hydrogen in anorthoclase and associated melt inclusions
- First occurrence of iodine in natural sulfosalts: The case of mutnovskite, Pb2AsS3(I,Cl,Br), a new mineral from the Mutnovsky volcano, Kamchatka Peninsula, Russian Federation
- The real topological conÞ guration of the extra-framework content in alkali-poor beryl: A multi-methodological study
- A low-temperature heat-capacity study of synthetic anhydrous Mg-cordierite (Mg2Al4Si5O18)
- Dissolution kinetics of pyrochlore ceramics for the disposition of plutonium
- Oxy-amphibole equilibria in Ti-bearing calcic amphiboles: Experimental investigation and petrologic implications for mantle-derived amphiboles
- Fe2+/Fe3+ charge ordering in contact layers of lamellar magnetism: Bond valence arguments
- Calcic amphibole growth and compositions in calc-alkaline magmas: Evidence from the Motru Dike Swarm (Southern Carpathians, Romania)
- Anomalously high Fe contents in rehomogenized olivine-hosted melt inclusions from oxidized magmas
- The rate of ferrihydrite transformation to goethite via the Fe(II) pathway
- Phase transitions and volumetric properties of cryolite, Na3AlF6: Differential thermal analysis to 100 MPa
- The crystal structure of dissakisite-(La) and structural variations after annealing of radiation damage
- Effects of metal protection coils on thermocouple EMF in multi-anvil high-pressure experiments
- First-principles study of the OH-stretching modes of gibbsite
- In situ X-ray diffraction study of phase transitions of FeTiO3 at high pressures and temperatures using a large-volume press and synchrotron radiation
- High-pressure proton disorder in brucite
- Microhardness, toughness, and modulus of Mohs scale minerals
- Effects of pH, temperature, and aqueous organic material on the dissolution kinetics of meta-autunite minerals, (Na, Ca)2-1[(UO2)(PO4)]2⋅3H2O
- InterstratiÞ ed kaolinite-smectite: Nature of the layers and mechanism of smectite kaolinization
- The kinetics of the α → β transition in synthetic nickel monosulÞ de
- An electron microprobe analysis, secondary ion mass spectrometry, and single-crystal X-ray diffraction study of phlogopites from Mt. Vulture, Potenza, Italy: Consideration of cation partitioning
- Unique W-rich alloy of Os and Ir and associated Fe-rich alloy of Os, Ru, and Ir from California
- Schreyerite, V2Ti3O9: New occurrence and crystal structure
- A cold-sealing capsule design for synthesis of fluid inclusions and other hydrothermal experiments in a piston-cylinder apparatus
- Complete solid-solution between Na3Al2(PO4)3 and Mg3Al2(SiO4)3 garnets at high pressure
