Parsa enstatite chondrite: a mineralogic and textural analysis
Public Deposited- Last Modified
- February 26, 2019
- Creator
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Horne, Audrey
- Affiliation: College of Arts and Sciences, Department of Geological Sciences
- Abstract
- The mineralogy and petrology of Parsa, an EH4 enstatite chondrite (Bhandari et al., 1980), was analyzed with an emphasis on the rare mineral roedderite [(Na,K)2(Mg,Fe)5Si12O30)] using a scanning electron microscope, a JEOL Hyperprobe, and a Raman spectrometer. The dominant minerals in Parsa include enstatite (Mg2Si2O6), kamacite (Fe-Ni alloy, more than 90-95 wt% Fe), troilite (FeS), and taenite (Fe-Ni alloy, more than 20 wt% Ni), indicating formation under highly reducing conditions. Secondary minerals include albite (NaAlSi3O8), quartz (SiO2), daubreelite (FeCr2S4), caswellsilverite (NaCrS2), roedderite, and a mystery Ca-Mg-silicate. The minerals are fragmented, creating a brecciated texture, with only the primary minerals forming crystals larger than 300 μm. All minerals are surrounded by FeO(OH), a weathering product of iron-containing minerals. Both kamacite and taenite contain up to 15 wt% Si, with more partitioned into taenite. Kamacite contains quartz inclusions, whereas taenite does not. The metallic minerals demonstrate partial melting, indicating that Parsa’s parent body underwent a heating episode. Roedderite occurs as elongated euhedral crystals, commonly as inclusions in troilite. All crystals are less than 15 μm across. K and Na typically occur in a 1:1 atomic ratio with no apparent zoning. Roedderite contained within troilite typically forms euhedral to subhedral, unbrecciated prisms with aspect ratios of ~5, whereas roedderite crystals surrounded by brecciated silicates are typically anhedral. This difference in morphology may reflect differences in the physical properties of the troilite and other phases.
- Date of publication
- spring 2014
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- Rights statement
- In Copyright
- Note
- Funding: SURF Grant
- Advisor
- Glazner, Allen F.
- Degree
- Bachelor of Science
- Honors level
- Honors
- Degree granting institution
- University of North Carolina at Chapel Hill
- Extent
- 28
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