Redox states of thirteen shergottites as inferred from iron micro X-ray absorption near edge structure of maskelynite

Satake, Wataru; Mikouchi, T.; Miyamoto, M.

doi:10.2343/geochemj.2.0288

Cited by 5 publications

(7 citation statements)

References 33 publications

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“…The Fo contents of olivine in the analyzed Itokawa particles including new samples are all in the limited range ) ratios have been well determined by wet chemistry (Monkawa et al 2006;Satake et al 2014). The presence of two peaks corresponding to Fe 2+ and Fe 3+ is obvious.…”

Section: Equilibrated Nature Of Analyzed Particlesmentioning

confidence: 79%

“…Details of the SR-XRD measurement are described in Hagiya et al (2010). For plagioclase in RA-QD02-0100 and RA-QD02-0133-1, we performed SR iron X-ray absorption near-edge structure (XANES) measurements to determine the presence of Fe 3+ at BL-4A, Photon Factory (PF), High Energy Accelerator Research Organization (KEK, Ibaraki, Japan) using the method described in Monkawa et al (2006) and Satake et al (2014). The SR X-ray beam size was approximately 5 × 6 μm.…”

Section: Methodsmentioning

confidence: 99%

“…However, such a high Fe 3+ /Fe 2+ ratio is known from maskelynite (shocked plagioclase glass) in Martian meteorites and is interpreted to represent the formation under an oxidizing environment (Satake et al 2014). Although the plagioclase compositions are different, maskelynite in Martian meteorites is estimated to have formed at around a few log units above the iron wüstite buffer (logfO 2 = IW + 2~3), where the Fe 3+ /(Fe 2+ +Fe 3+ ) ratio is approximately 0.5 (Satake et al 2014). Similarly, Noguchi et al (2013) reported Fe-XANES analysis of olivine in some Itokawa particles and suggested similarity to the Tuxtuac LL5 chondrite.…”

Section: Itokawa Particles Are Ll Chondritesmentioning

confidence: 99%

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Mineralogy and crystallography of some Itokawa particles returned by the Hayabusa asteroidal sample return mission

et al. 2014

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We studied seven Itokawa particles provided by the Japan Aerospace Exploration Agency (JAXA) as first International Announcement of Opportunity (AO) study mainly using electron and synchrotron radiation X-ray beam techniques. All the analyzed particles were collected from the first-touchdown site and composed of olivine and plagioclase with traces of Ca phosphate and chromite, and do not contain pyroxenes. Optical microscopy of these particles shows minor undulatory extinction of olivine and plagioclase, suggesting minor shock metamorphism (shock stage: S2). The electron microprobe analysis shows that olivine is

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Section: Equilibrated Nature Of Analyzed Particlesmentioning

confidence: 79%

Section: Methodsmentioning

confidence: 99%

Section: Itokawa Particles Are Ll Chondritesmentioning

confidence: 99%

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Mineralogy and crystallography of some Itokawa particles returned by the Hayabusa asteroidal sample return mission

et al. 2014

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“…; Satake et al. ). The XANES spectra at the Fe K‐absorption edge were obtained in the fluorescence mode by scanning the incident X‐ray energy from 7105 to 7153 eV at an interval of ~0.12 eV.…”

Section: Sample and Analytical Techniquesmentioning

confidence: 98%

“…In order to constrain the charge valence of iron in both colorless and brown olivine, synchrotron radiation (SR) micro-XANES (X-ray absorption near edge structure) analysis was performed at beam line BL-4A, Photon Factory, High Energy Accelerator Research Organization (KEK), Tsukuba, Japan and pre-edge spectra of Fe were compared in order to estimate their Fe 3+ /ΣFe ratios (Monkawa et al 2006;Satake et al 2014). The XANES spectra at the Fe K-absorption edge were obtained in the fluorescence mode by scanning the incident X-ray energy from 7105 to 7153 eV at an interval of~0.12 eV.…”

Section: Sample and Analytical Techniquesmentioning

confidence: 99%

Mineralogical study of brown olivine in Northwest Africa 1950 shergottite and implications for the formation mechanism of iron nanoparticles

Takenouchi

Mikouchi

Kogure

2017

Meteorit & Planetary Scien

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Martian meteorites, in particular shergottites, contain darkened olivine (so‐called “brown olivine”) whose color is induced by iron nanoparticles formed in olivine during a shock event. The formation process and conditions of brown olivine have been discussed in the Northwest Africa 2737 (NWA 2737) chassignite. However, formation conditions of brown olivine in NWA 2737 cannot be applied to shergottites because NWA 2737 has a different shock history from that of shergottites. Therefore, this study observed brown olivine in the NWA 1950 shergottite and discusses the general formation process and conditions of brown olivine in shergottites. Our observation of NWA 1950 revealed that olivine is heterogeneously darkened between and within grains different from brown olivine in NWA 2737. XANES analysis showed that brown olivine contains small amounts of Fe3+ and TEM/STEM observation revealed that there is no SiO‐rich phase around iron metal nanoparticles. These observations indicate that iron nanoparticles were formed by a disproportionation reaction of olivine (3Fe2+olivine → Fe0metal + 2Fe3+olivine + Volivine, where Volivine means a vacancy in olivine). Some parts of brown olivine show lamellar textures in SEM observation and Raman peaks in addition to those expected for olivine, implying that brown olivine experienced a phase transition (to e.g., ringwoodite). In order to induce heterogeneous darkening, heterogeneous high temperature of about 1500–1700 K and shock duration of at least ~90 ms are required. This heterogeneous high temperature resulted in high postshock temperature (>900 K) inducing back‐transformation of most high‐pressure phases. Therefore, in spite of lack of high‐pressure phases, NWA 1950 (= Martian meteorites with brown olivine) experienced higher pressure and temperature compared to other highly shocked meteorite groups.

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Petrology and shock history of the first depleted‐like poikilitic shergottite Asuka 12325

Takenouchi,

Yamaguchi,

Mikouchi

et al. 2023

Meteorit & Planetary Scien

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Asuka (A) 12325 is the first poikilitic shergottite having a depleted pattern in light rare earth elements (REE). Compared with known poikilitic shergottites, A 12325 has smaller but more abundant pyroxene oikocrysts with remarkable Fe‐rich pigeonite rims, indicating that A 12325 cooled relatively faster at a shallower part of the crust. The redox condition (logfO2 = IW + 0.6‐IW + 1.7) and Fe‐rich chemical compositions of each mineral in A 12325 are close to enriched shergottites. The intermediate shergottites could not form by a simple mixing between parent magmas of A 12325 and enriched shergottites. Although A 12325 contains various high‐pressure minerals such as majorite and ringwoodite, plagioclase is only partly maskelynitized. Therefore, the maximum shock pressure may be within 17–22 GPa. Thermal conduction and ringwoodite growth calculation around a shock vein revealed that the shock dwell time of A 12325 is at least 40 ms. The weaker shock pressure and longer shock dwell time in A 12325 may be attained by an impact event similar to those of nakhlites and Northwest Africa (NWA) 8159. Such a weak shock ejection event may be as common on Mars as a severe shock event recorded in shergottites. Alteration of sulfide observed in A 12325 may imply the presence of magmatic fluid in its reservoir on Mars. A 12325 expands a chemical variety of Martian rocks and has a unique shock history among poikilitic shergottites while A 12325 also implies that poikilitic shergottites are common rocks on Mars regardless of their sources.

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Redox states of thirteen shergottites as inferred from iron micro X-ray absorption near edge structure of maskelynite

Cited by 5 publications

References 33 publications

Mineralogy and crystallography of some Itokawa particles returned by the Hayabusa asteroidal sample return mission

Mineralogy and crystallography of some Itokawa particles returned by the Hayabusa asteroidal sample return mission

Mineralogical study of brown olivine in Northwest Africa 1950 shergottite and implications for the formation mechanism of iron nanoparticles

Petrology and shock history of the first depleted‐like poikilitic shergottite Asuka 12325

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