Preferential occupation of pyroxene sites by iron in diogenite meteorites

Verma, H. C.; Tewari, V. C.; Paliwal, B. S.; Tripathi, R. P.

doi:10.1007/978-3-540-78697-9_146

Cited by 3 publications

(5 citation statements)

References 19 publications

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“…Verma et al. () studied pyroxenes in ALHA 77256, Tatahouine, and Bilanga and found no evidence for Fe 3+ . McCanta et al.…”

Section: Discussionmentioning

confidence: 99%

“…Costa et al (1991) studied pyroxenes in the Ibitira meteorite but did not resolve any contributions from Fe 3+ . Verma et al (2008) studied pyroxenes in ALHA 77256, Tatahouine, and Bilanga and found no evidence for Fe 3+ . McCanta et al (2008) handpicked phases from the LAP 04840 meteorite but there was insufficient material for a pure orthopyroxene separate to be analyzed.…”

Section: Comparisons With Meteoritic Pyroxenesmentioning

confidence: 99%

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Impact‐related thermal effects on the redox state of Ca‐pyroxene

McCanta

Dyar

2016

Meteorit & Planetary Scien

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Oxidation is observed in Ca‐pyroxene subjected to a range of shock pressures (21–59 GPa). Changes in the pyroxene redox ratio as measured by the changes in %Fe3+ ranged from 2–6 times the starting composition. Mössbauer and reflectance spectroscopy record the changing Fe3+ concentration as a preferential oxidation of Fe2+ in the M2 crystallographic site. The oxidation is also accompanied by mechanical changes in the pyroxene crystals including fracturing, linear defects, and twinning. As oxygen fugacity is often calculated using mineral redox ratios and thought to represent the prevailing fO2 during crystallization, it is imperative to recognize that the fO2 values measured in impact‐derived materials may represent that of the impact and not the magma source region.

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“…Verma et al. () studied pyroxenes in ALHA 77256, Tatahouine, and Bilanga and found no evidence for Fe 3+ . McCanta et al.…”

Section: Discussionmentioning

confidence: 99%

Section: Comparisons With Meteoritic Pyroxenesmentioning

confidence: 99%

Impact‐related thermal effects on the redox state of Ca‐pyroxene

McCanta

Dyar

2016

Meteorit & Planetary Scien

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“…Cooling rate estimates for diogenitic pyroxenes [ Zema et al ., ] are generally faster than that for a clearly crustal cumulate eucrite determined using the same method [ Domeneghetti et al ., ], suggesting a crustal origin for diogenites. However, Fe site occupancy data [ Verma et al ., ] may suggest even slower cooling for diogenites, perhaps at mantle depths. Study of lattice preferred orientations in diogenite olivines reveals plastic deformation like that of terrestrial mantle rocks, supporting their formation at mantle depths [ Tkalcec et al ., ].…”

Section: Predicted Crust and Mantle Stratigraphy And Compositionsmentioning

confidence: 99%

Composition of the Rheasilvia basin, a window into Vesta's interior

et al. 2013

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[1] The estimated excavation depth of the huge Rheasilvia impact basin is nearly twice the likely thickness of the Vestan basaltic crust, so the mantle should be exposed. Spectral mapping by the Dawn spacecraft reveals orthopyroxene-rich materials, similar to diogenite meteorites, in the deepest parts of the basin and within its walls. Significant amounts of olivine are predicted for the mantles of bulk-chondritic bodies like Vesta, and its occurrence is demonstrated by some diogenites that are harzburgite and dunite. However, olivine has so far escaped detection by Dawn's instruments. Spectral detection of olivine in the presence of orthopyroxene is difficult in samples with <25% olivine, and olivine in Rheasilvia might have been diluted during impact mixing or covered by the collapse of basin walls. The distribution of diogenite inferred from its exposures in and around Rheasilvia provides a geologic context for the formation of these meteorites, but does not clearly distinguish between a magmatic cumulate versus partial melting restite origin for diogenites. The former is favored by geochemical arguments, and crystallization in either a magma ocean or multiple plutons emplaced near the crust-mantle boundary is permitted by Dawn observations.

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“…IR spectra revealed the characteristic pyroxene peaks in AAT‐1 sample. Diogenites are mainly composed of magnesium‐rich orthopyroxenes, and they generally show orthorhombic structures 21 . In a study by Bowey et al, in the spectra of almost all low‐pressure silicates, a strong Si‐O stretching feature in the region of about 1000 cm −1 and O‐Si‐O bending in the region of about 500 cm −1 are common, which is due to the structure of SiO 4 tetrahedra.…”

Section: Resultsmentioning

confidence: 99%

“…Diogenites are mainly composed of magnesium-rich orthopyroxenes, and they generally show orthorhombic structures. 21 In a study by Bowey et al, in the spectra of almost all low-pressure silicates, a strong Si-O stretching feature in the region of about 1000 cm À1 and O-Si-O bending in the region of about 500 cm À1 are common, which is due to the structure of SiO 4 tetrahedra. It is also known that translations occur as a result of the movements of metal cations in the region of about 450 cm À1 .…”

Section: Infrared Spectroscopymentioning

confidence: 97%

Vibrational spectroscopic, crystallographic, and microscopic investigation on the Aioun El Atrouss diogenite

Ayvaz,

Unsalan,

Castro

et al. 2023

J Raman Spectroscopy

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Diogenites are thought to have originated from asteroid 4 Vesta asteroid, and it has been previously shown that they mostly consist of orthopyroxene, chromite, and olivine minerals. In this study, the Aioun El Atrouss (AAT‐1) diogenite was analyzed by vibrational spectroscopic (FT‐IR and micro‐Raman), EDXRF, and XRD techniques. AAT‐001 is mainly composed of pyroxene and with lesser olivine. XRD investigation confirmed magnetite, kamacite, ilmenite, and albite. A troilite‐orthopyroxene intergrowth was revealed by XRF. The olivine composition was estimated to be approximately Fo66 by Raman olivine characteristic doublets. Pyroxenes in AAT‐01 were found to be En80Fs20. Finally, approximate peak shock pressure of more than 86 GPa for AAT‐1 was suggested based on previous hypervelocity impact experiments on olivine.

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Preferential occupation of pyroxene sites by iron in diogenite meteorites

Cited by 3 publications

References 19 publications

Impact‐related thermal effects on the redox state of Ca‐pyroxene

Impact‐related thermal effects on the redox state of Ca‐pyroxene

Composition of the Rheasilvia basin, a window into Vesta's interior

Vibrational spectroscopic, crystallographic, and microscopic investigation on the Aioun El Atrouss diogenite

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