Cathodoluminescence Characterization of Maskelynite and Alkali Feldspar in Shergottite (Dhofar 019)

Kayama, Mitsu; Nakazato, T.; Nishido, H.; Ninagawa, K.; Gucsik, A.

doi:10.1063/1.3222879

Cited by 2 publications

(4 citation statements)

References 5 publications

(10 reference statements)

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“…Similar emission bands have been reported in the CL spectra of experimentally shocked sanidine, microcline, and albite above 30 GPa (partly at 20 GPa) and those of maskelynite in Martian meteorites (Kayama et al 2012). Such a spectral pattern is characteristic of maskelynite and diaplectic feldspar glass, and undetectable in crystalline plagioclase (Kayama et al 2009a(Kayama et al , 2009b(Kayama et al , 2012. On the other hand, the CL spectroscopy of the dark portion exhibits only a blue emission band at~410 nm ( Fig.…”

Section: High-pressure Polymorphs Of Plagioclasesupporting

confidence: 78%

“…Crystalline plagioclase in rocks also shows the blue emission bands (Kayama et al. , , ). Therefore, the bright and dark portions observed in the panchromatic CL images correspond to maskelynite and residual plagioclase, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…Such a spectral pattern is characteristic of maskelynite and diaplectic feldspar glass, and undetectable in crystalline plagioclase (Kayama et al. , , ). On the other hand, the CL spectroscopy of the dark portion exhibits only a blue emission band at ~410 nm (Fig.…”

Section: Resultsmentioning

confidence: 99%

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High‐pressure polymorphs in Yamato‐790729 L6 chondrite and their significance for collisional conditions

Kato

Sekine

Kayama

et al. 2017

Meteorit & Planetary Scien

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Shock pressure recorded in Yamato (Y)‐790729, classified as L6 type ordinary chondrite, was evaluated based on high‐pressure polymorph assemblages and cathodoluminescence (CL) spectra of maskelynite. The host‐rock of Y‐790729 consists mainly of olivine, low‐Ca pyroxene, plagioclase, metallic Fe‐Ni, and iron‐sulfide with minor amounts of phosphate and chromite. A shock‐melt vein was observed in the hostrock. Ringwoodite, majorite, akimotoite, lingunite, tuite, and xieite occurred in and around the shock‐melt vein. The shock pressure in the shock‐melt vein is about 14–23 GPa based on the phase equilibrium diagrams of high‐pressure polymorphs. Some plagioclase portions in the host‐rock occurred as maskelynite. Sixteen different CL spectra of maskelynite portions were deconvolved using three assigned emission components (centered at 2.95, 3.26, and 3.88 eV). The intensity of emission component at 2.95 eV was selected as a calibrated barometer to estimate shock pressure, and the results indicate pressures of about 11–19 GPa. The difference in pressure between the shock‐melt vein and host‐rock might suggest heterogeneous shock conditions. Assuming an average shock pressure of 18 GPa, the impact velocity of the parent‐body of Y‐790729 is calculated to be ~1.90 km s−1. The parent‐body would be at least ~10 km in size based on the incoherent formation mechanism of ringwoodite in Y‐790729.

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Section: High-pressure Polymorphs Of Plagioclasesupporting

confidence: 78%

Section: Resultsmentioning

confidence: 99%

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High‐pressure polymorphs in Yamato‐790729 L6 chondrite and their significance for collisional conditions

Kato

Sekine

Kayama

et al. 2017

Meteorit & Planetary Scien

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“…On the other hand, there are claims that maskelynite can be formed via quenching from a shock melt as a fused plagioclase glass under high pressure (Chen and El Goresy, 2000). Cathodoluminescence (CL) techniques have been used as pivotal tools, for example, geochemistry, petrology, mineralogy, and crystallography (e.g., Kayama et al, 2009a). CL microscopy enables the observation of various features such as the two-dimensional distribution of silica polymorphs and chemical zoning in plagioclase.…”

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confidence: 99%

Cathodoluminescence mineralogy of Ca-rich plagioclase in experimentally shocked Stillwater gabbronorite

KANEMARU,

YAMAGUCHI,

SEKINE

et al. 2024

Journal of Mineralogical and Petrological Sciences

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We performed a cathodoluminescence (CL) study of in Stillwater gabbronorite experimentally shocked at 20.1, 29.8, and ~41 GPa, for characterization of the shock effects. Chroma CL image of unshocked plagioclase showed the homogeneous red CL emission. In contrast, experimentally shocked plagioclase showed the heterogeneous CL emission colors in red and blue. The Raman spectra analysis identified that the red and blue portions correspond to plagioclase and maskelynite, respectively. In our observation, plagioclase experimentally shocked at 20 GPa was partially converted into maskelynite. At 30 GPa, most of plagioclase were converted into maskelynite. At 40 GPa, plagioclase was fully converted into maskelynite. Our observations of Ca-rich plagioclase indicated that the maskelynization starts at a slightly lower pressure and completes at a higher pressure than those in the previous studies (~24 GPa and ~28 GPa, respectively). These pressure differences may be due to the high sensitivity of CL, which allows for the detection of small (a few µm in size) and rare phases that may have been overlooked in the traditional methods. The CL spectra of plagioclase showed a continuous change with increasing shock pressure. Hence, the CL imaging method using plagioclase and maskelynite is found to be very effective to estimate precisely shock pressure. In particular, there was a marked decrease in the CL intensity of Mn 2+ and Fe 3+ centers. Furthermore, the shock-induced center around the UV region was observed in experimentally shocked plagioclase and maskelynite. These CL features reflect the destruction of the framework structure to varying extents depending upon shock pressure.Combined with the FTIR analysis in the present study, the transition of plagioclase to maskelynite was clearly illustrated in spectra. The reflectivity decreased continuously with increasing shock pressures during maskelynization. Additionally, the absorption at ~8.6 µm observed in plagioclase was absent in maskelynite. This feature can be used as a diagnostic feature to characterize plagioclase and maskelynite by FTIR.

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Cathodoluminescence Characterization of Maskelynite and Alkali Feldspar in Shergottite (Dhofar 019)

Cited by 2 publications

References 5 publications

High‐pressure polymorphs in Yamato‐790729 L6 chondrite and their significance for collisional conditions

High‐pressure polymorphs in Yamato‐790729 L6 chondrite and their significance for collisional conditions

Cathodoluminescence mineralogy of Ca-rich plagioclase in experimentally shocked Stillwater gabbronorite

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