Unique mineral assemblages of shock-induced titanium-rich melt pockets in eucrite Northwest Africa 8003

Pang, Run‐Lian; Harries, Dennis; Pollok, Kilian; Zhang, Ai‐Cheng; Langenhorst, F.

doi:10.1016/j.chemer.2019.125541

Cited by 5 publications

(8 citation statements)

References 46 publications

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“…In the present study, corundum occurs as a fine-grained aggregate dispersed in the inner part of shock-induced melt regions which contains the high-pressure mineral tissintite. This occurrence and the association with tissintite indicate that the corundum aggregates formed from a shock-induced melt in the lunar meteorites, similar to that in the eucrite NWA 8003 (Pang et al, 2018(Pang et al, , 2019 and the achondrite meteorite NWA 7325 (Yang et al, 2019), but different from the corundum grains (40-200 μm in size) in Apollo fines (Christophe-Michel-Levy et al, 1972;Kleinmann & Ramdohr, 1971). In texture, tissintite is located at the edge of the zoned, molten regions while corundum is located at the inner zone (Figure 1).…”

Section: Formation Conditions Of Tissintite and Corundummentioning

confidence: 84%

“…Therefore, 4–5 GPa might be the lower limit for the tissintite formation of Ca‐rich plagioclase composition (Rucks et al., 2019). Although most tissintite grains in the lunar meteorites contain a few weight percent of MgO + FeO (>1 wt%) differing from the Mg,Fe‐poor tissintite in the synthetic experiments (Rucks et al., 2018, 2019), some of the Mg,Fe‐bearing/rich tissintite aggregates are in direct contact spatially with Mg,Fe‐poor tissintite in chemically heterogeneous molten regions (Figure 1b). Therefore, it is likely that the Mg,Fe‐bearing tissintite aggregates have also formed at a pressure at least 4–5 GPa.…”

Section: Discussionmentioning

confidence: 96%

“…Corundum is a relatively rare mineral in extraterrestrial samples. Its formation varies from presolar origin (Takigawa et al., 2018), solar‐nebula condensation origin (Makide et al., 2009; Simon et al., 2002), alteration origin of Ca,Al‐rich inclusions (Ma et al., 2009), xenolith origin in eucritic basalt (Li et al., 2020), shock‐induced origin (Pang et al., 2018, 2019; Yang et al., 2019), and unknown origin (Christophe‐Michel‐Levy et al., 1972; Kleinmann & Ramdohr, 1971). In the Apollo samples, corundum grains were found only in fines, without exact textural information (Christophe‐Michel‐Levy et al., 1972; Kleinmann & Ramdohr, 1971).…”

Section: Discussionmentioning

confidence: 99%

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Widespread Tissintite in Strongly Shock‐Lithified Lunar Regolith Breccias

Zhang

Jiang

Tomioka

et al. 2021

Geophysical Research Letters

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Shock‐lithification is a fundamental process of making rocks from fine‐grained and porous regoliths on the surface of the Moon. Previous investigations have constrained potential shock pressures during shock‐lithification based on experimental and numerical simulations. However, pressure and temperature conditions during shock‐lithification have not been directly inferred from natural lunar breccias. Here, we report the discovery of widespread tissintite in strongly shock‐lithified lunar meteorites, accompanied occasionally by Si‐rich corundum and coesite. The coexistence of tissintite and coesite and the absence of stishovite in molten regions indicate a shock pressure of 4–8 GPa, which might be the pressure boundary between weak and strong shock‐lithification. Meanwhile, the presence of Si‐rich corundum imposes a temperature constraint of ∼2,300 K for the intergranular melts. This temperature constraint has profound significance for interpreting the behaviors of volatile and moderately volatile elements and remanent magnetization records during strongly shock‐lithification of lunar breccias.

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Section: Formation Conditions Of Tissintite and Corundummentioning

confidence: 84%

Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

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Widespread Tissintite in Strongly Shock‐Lithified Lunar Regolith Breccias

Zhang

Jiang

Tomioka

et al. 2021

Geophysical Research Letters

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“…; Pang et al. 2018b). Based on previous experimental results, the assemblage grossular + kyanite + silica has a large range of pressure and temperature (~2–15 GPa and < 2000 °C; Liu et al.…”

Section: Discussionmentioning

confidence: 99%

Shock‐induced phase transformation of anorthitic plagioclase in the eucrite meteorite Northwest Africa 2650

Chen

Zhang

Pang

et al. 2019

Meteorit & Planetary Scien

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Anorthite is an important constituent mineral in basaltic achondrites from small celestial bodies. Its high‐pressure phase transformation in shocked meteorites has not been systematically studied. In this study, we report the diverse phase transformation behaviors of anorthite in a shocked eucrite Northwest Africa (NWA) 2650, which also contains coesite, stishovite, vacancy‐rich clinopyroxene, super‐silicic garnet, and reidite. Anorthite in NWA 2650 has transformed into anorthite glass (anorthite glassy vein, maskelynite, and glass with a schlieren texture and vesicles), tissintite and dissociated into three‐phase assemblage grossular + kyanite + silica glass. Different occurrences of anorthite glass might have formed via the mechanism involving shear melting, solid‐state transformation, and postshock thermally melting, respectively. Tissintite could have crystallized from a high‐pressure plagioclase melt. The nucleation of tissintite might be facilitated by relict pyroxene fragments and the early formed vacancy‐rich clinopyroxene. The three‐phase assemblage grossular, kyanite, and silica glass should have formed from anorthitic melt at high‐pressure and high‐temperature conditions. The presence of maskelynite and reidite probably suggests a minimum peak shock pressure up to 20 GPa, while the other high‐pressure phases indicate that the shock pressure during the crystallization of shock melt veins might vary from >8 GPa to >2 GPa with a heterogeneous temperature distribution.

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“…Shock‐induced melting and high‐pressure minerals have been identified in eucrites (coesite, stishovite, tissintite, vestaite, zagamiite, and the majorite‐bearing garnet); however, their occurrence has still been restricted to a handful of meteorites: Béréba, Northwest Africa (NWA) 2650, NWA 7643, NWA 8003, NWA 8120, NWA 8677, and NWA 10658 (Pang et al. 2016, 2018, 2019; Chen et al. 2019; Fudge and Sharp 2020).…”

Section: Introductionmentioning

confidence: 99%

Complicated pressure–temperature path recorded in the eucrite Padvarninkai

Miyahara

Yamaguchi

Ohtani

et al. 2021

Meteorit & Planetary Scien

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High‐pressure minerals in the eucrite Padvarninkai were investigated. Parts of anorthitic plagioclase and tridymite in the host rock of Padvarninkai vitrified, indicating that the shock pressure was 22–27 GPa. Tissintite, coesite, and a majorite‐bearing garnet occurred in the shock‐melt veins of Padvarninkai as high‐pressure minerals. Tissintite, kyanite, corundum, and dense plagioclase have occurred in the anorthitic plagioclase grains. The anorthitic plagioclase was melted and tissintite crystallized from the melt after the crystallization of kyanite and corundum. The residual melt became dense plagioclase by quenching. Tridymite has also melted and coesite crystallized from the melt. The formation of tissintite and coesite indicates that the shock pressure recorded in the veins was 2–13 GPa. The temperature increased drastically in the veins (>˜3000 K) compared with the host rock (<˜800 K). Parts of the tissintite and coesite became, respectively, amorphous (or anorthite) and quartz. Two different impact events may be recorded in Padvarninkai: The first impact event brecciated a part of the host rock, and the second impact event induced the melting of the brecciated portion, resulting in the formation of shock‐melt veins where the conditions are a high temperature and a relatively low pressure. In the veins, tissintite and coesite formed first, and parts of them underwent a back‐transformation due to a long cooling time.

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Unique mineral assemblages of shock-induced titanium-rich melt pockets in eucrite Northwest Africa 8003

Cited by 5 publications

References 46 publications

Widespread Tissintite in Strongly Shock‐Lithified Lunar Regolith Breccias

Widespread Tissintite in Strongly Shock‐Lithified Lunar Regolith Breccias

Shock‐induced phase transformation of anorthitic plagioclase in the eucrite meteorite Northwest Africa 2650

Complicated pressure–temperature path recorded in the eucrite Padvarninkai

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