Spinel assemblages in lunar meteorites Graves Nunataks 06157 and Dhofar 1528: Implications for impact melting and equilibration in the Moon's upper mantle

Wittmann, A.; Korotev, R. L.; Jolliff, Bradley L.; Carpenter, P. K.

doi:10.1111/maps.13217

Cited by 10 publications

(31 citation statements)

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“…It is paradoxical that a suite of very primitive rocks (with high Mg#) would also host a very evolved KREEP signature (e.g., Elardo et al, 2017Elardo et al, , 2018Shearer et al, 2015;Shervais & McGee, 1998;Snyder et al, 1995). Rare occurrences of cordierite have also been reported (e.g., Herzberg & Baker, 1980;Marvin et al, 1989;Treiman, 1991;Treiman & Gross, 2012;Wittmann et al, 2019), suggesting that low-pressure, high-temperature metamorphic reactions may have chemically altered some of the Mg-suite cumulates.…”

Section: Introductionmentioning

confidence: 99%

Geochemistry and Petrogenesis of Northwest Africa 10401: A New Type of the Mg‐Suite Rocks

et al. 2020

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The petrogenetic models of the lunar crust are built on the returned Apollo and Luna samples collected from limited parts of the lunar nearside that are chemically unusual (i.e., material rich in K, Rare Earth Elements, and P [KREEP]) and not representative of the entire lunar lithologic suite. The lunar Mg-suite is part of this sample collection and ubiquitously has geochemical characteristics indicating the involvement of KREEP in their petrogenesis and seemed to be linked to the Procellarum KREEP Terrain (PKT). However, it is unclear if KREEP is necessary for Mg-suite magmatism or whether Mg-suite magmatism was a global event that occurred without significant KREEP contribution, and thus, Mg-suite rocks outside of the PKT region may exist without containing a significant KREEP signature. Here, we investigate lunar meteorite Northwest Africa (NWA) 10401, an anorthositic troctolitic breccia with a granulitic texture. NWA 10401 shares many characteristics of Apollo Mg-suite rocks: both its bulk rock composition and alumina content, as well as its mineralogy and mineral chemistry, are more consistent with typical Apollo Mg-suite rocks, rather than ferroan anorthosites. In addition, olivine-spinel equilibria calculations indicate that NWA 10401 is consistent with being derived from a common parent to the Apollo Mg-suite troctolites. However, despite these many shared characteristics, NWA 10401 is strongly depleted in REE, starkly separating it from the typical Apollo Mg-suite of the PKT. This indicates that NWA 10401 (and pairs) could represent a Mg-suite component outside the PKT, and thus, KREEP-poor Mg-suite magmatism may have been a global phenomenon on the Moon.Plain Language Summary Theories of the formation and evolution of the Moon's crust were built upon the returned Apollo and Luna samples that were collected from small areas of the Moon's nearside (the side that always faces Earth). These areas are now known to be chemically unusual and contain rocks that are rich in K, Rare Earth Elements (REE), and P, called KREEP. The lunar magnesian-suite, or Mg-suite, is part of this sample collection and represents a series of ancient rocks formed from slow cooling magmas that formed immediately after the end of magma ocean crystallization. Samples of this Mg-suite always have chemical characteristics that indicate the involvement of KREEP in their formation, and they seemed to be linked to the Procellarum KREEP Terrain (PKT) on the Moon. However, it is unclear if (1) KREEP is needed for the formation of Mg-suite magmatism, and thus, if Mg-suite magmatism is limited to the geographically restricted PKT area, or (2) whether Mg-suite magmatism was a global event that occurred without significant KREEP contribution. In this case, KREEP is simply a contamination in the Mg-suite rocks. If (2) is true, Mg-suite rocks outside of the PKT area on the Moon should be KREEP poor. In this study, we investigate the lunar feldspar-rich meteorite called Northwest Africa (NWA) 10401 from the lunar highlands. Calculations indicate t...

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Section: Introductionmentioning

confidence: 99%

Geochemistry and Petrogenesis of Northwest Africa 10401: A New Type of the Mg‐Suite Rocks

et al. 2020

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“…The petrological characteristics and computational results of the isothermal, isobaric phase diagrams of enthalpy versus composition support recrystallization from impact melts (Treiman et al, 2015). Similarly, impact melting has been suggested as the mode of formation of fine-grained, glassy melt breccias in Dho 1528 and GRA 06157 that contain ＜10 -20 μm spinel phenocrysts (Wittmann et al, 2019). The presence of spinel in meteorite NWA 13191 is closely related to melting, but is the origin of the melts caused by impact melting (exogenic) or magma (endogenic)?…”

Section: Formation Of Spinel-bearing Clasts In Nwa 13191mentioning

confidence: 77%

“…Among all lunar samples, spinel compositions basically meet the characteristics of PSA only for NWA 13191 and returned soil samples Luna 20 (Figs. 5 and 9a, Prinz et al 1973;Wittmann et al, 2019). For further comparison, we compiled analytical data for Luna 20 samples (Bansal et al, 1972;Haggerty, 1973;Helmke et al, 1973;Vinogradov, 1973;Snyder et al, 1992).…”

Section: The Spinel-bearing Clasts Of Nwa 13191 Vs the Spinel-bearing...mentioning

confidence: 99%

“…This indicates that the formation of PSA may have occurred on a global scale. PST clasts found in Lunar samples (e.g., Herzberg and Baker, 1980;Marvin et al, 1989;Cohen et al, 2001) and lunar meteorites (e.g., Wittmann et al, 2019) are the closest samples to the spectroscopic interpretation of the spinel composition. However, the spinel is general slightly richer in Fe and Cr than that in PSA, just one clastic particle from the regolith breccia 10019 (Keil et al, 1970) and spinel-bearing troctolite 2003 from Luna 20 (Cohen et al, 2001) are the only two samples with small amounts of near-pure spinel (Mg # ~ 93, Al # ~ 98; Mg # ~ 91, Al # ~ 98, respectively) matching PSA.…”

Section: Introductionmentioning

confidence: 96%

“…b. Spinel formed at low pressure by chemical reaction between picritic magma or Mg-suite parental melts and anorthositic crust (Morgan et al, 2006;Prissel et al, 2014). c. Spinel formed at high pressure in the deep crust (≥ ~ 25 -60 km), from basaltic or peridotitic precursors (Herzberg and Baker, 1980;Marvin et al, 1989;Wittmann et al, 2019). The hypotheses b and c contradict the apparent lack of mafic minerals in the PSA, because the picritic, basaltic, and peridotitic magma can produce abundant mafic minerals.…”

Section: Introductionmentioning

confidence: 99%

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A possible origin of the lunar spinel-bearing lithologies as told by the meteorite NWA 13191

Xie,

Chen,

Miao

et al. 2024

American Mineralogist

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Pink spinel anorthosite (PSA) and pink spinel troctolite (PST) are two lunar lithologies known to contain Mgrich spinel. PSA rich in spinel and lacking mafic minerals, was detected by the visible and near-infrared reflectance spectroscopy. PST clasts were found in returned lunar samples and meteorites. NWA 13191 is a recently approved lunar meteorite that contains a large amount of spinel-bearing clasts and provides an opportunity to discuss its origin. In this paper, 64 spinel-bearing clasts are studied. These clasts are dominated by anorthitic feldspars (20.8 -80.9 vol.%, An90.9-96.8), mafic-rich and aluminum-rich melt (14.7 -72.1 vol.%) and spinels (0.19 -5.18 vol.%). 49 of these clasts appears to have an unusually low modal abundance of mafic silicates (avg. olivine ± pyroxene, 1.87 vol.%), which distinguishes it from known spinel-bearing lunar samples (e.g., PST). The spinel composition (avg. Mg # = 90.6, Al # = 97.4) and mafic minerals content are basically consistent with those of PSA. The absorption characteristics of the melt in the reflection spectrum are not obvious, so it is not clear if the PSA contains melt. The simulated crystallization experiment clearly shows that it contains a large amount of melt at the spinel crystallization stage. These phenomena provide experimental and sample evidences for the existence of melt in the lunar spinel-bearing lithologies. NWA 13191 records the highest known bulk Mg # (avg. 89.8) and the spinel records the highest Al # (98.8) and Mg # (93.1) of lunar samples to date. The chemical properties of spinel-bearing clasts in NWA 13191 are consistent with the slightly REE-enriched and alkali-poor Mg-suite rocks, such as PST, magnesian anorthosites (MANs), and olivine-enriched Mg-suite rocks. These phenomena and previous simulated crystallization experiments indicate that the Mg-Al-rich melt may be produced by impact melting of Mg-rich anorthosite precursors. The spinel is a metastable crystallization product along with plagioclase and vitric melt near the Moon's surface. This realization provides sample observational evidence for previous simulated crystallization experiments and theoretical speculations.

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Using Lunar Granulites to Constrain Re‐Equilibration Timescales of Contact Thermal Metamorphism on the Moon

2023

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Rocks of the lunar granulite suite are the product of high‐temperature metamorphism within the Moon's crust. However, to date, their formation conditions have few constraints. Here, we combine Ti‐in‐pyroxene element diffusion modeling and two‐pyroxene thermometry with thermal modeling of the lunar crust in order to assess potential heat sources that could generate granulite metamorphism within the lunar highland crust. For the samples investigated in this study, the pyroxene crystals experienced peak metamorphic temperatures between ∼1,027 and 1,091°C over timescales ranging from ∼153 years to ∼15.1 Kyrs. To best satisfy these temperature and timescale constraints, hot (∼2,300°C) impact melt sheets with thickness ranging from 350 m to 3.35 km—equating to impact crater diameters between ∼60 and 280 km—have the potential to heat the underlying anorthositic crust. Deep (>20 km) igneous bodies, such as the large (>10 km thick) sills observed by the GRAIL mission near the base of the lunar crust, also have the potential to generate the required peak metamorphic temperatures; however, the thermal equilibration timescales in this scenario are modeled to be much larger (>100 Kyrs) than was witnessed by the granulites investigated. Our modeling highlights that while lunar granulites are only a minor component within the Apollo and meteorite collection, they are likely an important and ubiquitous lithology within the lunar highland crust.

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Spinel assemblages in lunar meteorites Graves Nunataks 06157 and Dhofar 1528: Implications for impact melting and equilibration in the Moon's upper mantle

Cited by 10 publications

References 68 publications

Geochemistry and Petrogenesis of Northwest Africa 10401: A New Type of the Mg‐Suite Rocks

Geochemistry and Petrogenesis of Northwest Africa 10401: A New Type of the Mg‐Suite Rocks

A possible origin of the lunar spinel-bearing lithologies as told by the meteorite NWA 13191

Using Lunar Granulites to Constrain Re‐Equilibration Timescales of Contact Thermal Metamorphism on the Moon

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