Compositional variation in Apollo 16 impact-melt breccias and inferences for the geology and bombardment history of the Central Highlands of the Moon

Korotev, R. L.

doi:10.1016/0016-7037(94)90372-7

Cited by 95 publications

(265 citation statements)

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“…On many twoelement plots the majority of samples fall along a mixing line (dashed lines in Figure 2) defined by the average composition of the samples and plagioclase. Similar trends, which are probably clast-matrix mixing trends, are seen in some of the Apollo 16 groups [Korotev, 1994]. The typical or normal Apollo 14 samples are those that populate the group designated here as A14-N (Table 1).…”

Section: Compositional Groupings By Landing Sitesupporting

confidence: 59%

“…Some samples that have been identified as VHA basalts are considerably more aluminous (up to 26% A1203) than the compositions discussed here. I suspect, largely on the basis of results from this work (section 5.4) but also on the basis of the distribution of data points on plots such as Figure 4 of Korotev [1994], that most of the samples of melt group 2 that are compositionally more feldspathic than groups 2DB and 2NR (e.g., group 2F of Korotev [1994] (Figure l c) suggests that the KREEP component also supplies much of the Ti, although some models have ingroup recognized and designated the "high-Sm" group by Jolliff cluded mare basalt to help account for Ti [Ryder, 1979] …”

Section: Compositional Groupings By Landing Sitementioning

confidence: 91%

“…The samples of group 2DB, in particular, form a tight cluster on plots of lithophile elements (Figure 4). Korotev [ 1994] also showed that a fifth group, designated 2Mo, is generally similar to group 2DB but is variably enriched in an olivine-bearing component. Figure 4 makes Table 1 is based emirely on sample 64815, which is compositionally distinct from other Apollo 16 mafic melt breccias [Korotev, 1994].…”

Section: Compositional Groupings By Landing Sitementioning

confidence: 94%

“…These samples include 14068 [Hubbard et at., 1972] (Figure 4). The following sources provide the data for this figure and the A15 averages of Korotev [1994] (1M, 1F, 2DB, and 2NR) for which there are many samples of each. Groups A16-2DB and A16-2NR are very similar and would be indistinguishable from each other if the intersample compositional scatter were as great as it is for other melt breccia groups.…”

Section: Compositional Groupings By Landing Sitementioning

confidence: 99%

“…There is some evidence that other small rocks in the regolith are compositionally similar , in which case sample 64815 may represent an actual compositional "group." I have not included group 2M of Korotev [1994] because this group consists of a hodgepodge of samples with compositions somewhat similar to groups 2DB and 2NR but not similar enough to be included in these compositionally tight groups. Together, the various group 2 melt breccias of Apollo 16 are samples that have been designated VHA (very high alumina) basalts in older literature and have been regarded by some as distinct from breccias associated with the LKFM composition [Spudis, 1984; McKinley et al, 1984].…”

Section: Compositional Groupings By Landing Sitementioning

confidence: 99%

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The great lunar hot spot and the composition and origin of the Apollo mafic (“LKFM”) impact‐melt breccias

Korotev¹

2000

J. Geophys. Res.

129

187

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Abstract. Thorium-rich, marie impact-melt breccias from the Apollo 14-17 missions, that is, those breccias identified with the composition known as "LKFM," are regarded largely as products of basin-forming impacts that penetrated the feldspathic crust and sampled underlying marie material and magma-ocean residuum carrying the compositional signature of KREEP (potassium, rare earth elements, phosphorous). Despite considerable compositional variation among such breccias, compositions of all of them correspond to mixtures of only four components: (1)

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Section: Compositional Groupings By Landing Sitesupporting

confidence: 59%

Section: Compositional Groupings By Landing Sitementioning

confidence: 91%

Section: Compositional Groupings By Landing Sitementioning

confidence: 94%

Section: Compositional Groupings By Landing Sitementioning

confidence: 99%

Section: Compositional Groupings By Landing Sitementioning

confidence: 99%

See 3 more Smart Citations

The great lunar hot spot and the composition and origin of the Apollo mafic (“LKFM”) impact‐melt breccias

Korotev¹

2000

J. Geophys. Res.

129

187

View full text Add to dashboard Cite

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Iron Abundances in Lunar Impact Basin Melt Sheets From Orbital Magnetic Field Data

2017

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Magnetic field data acquired from orbit shows that the Moon possesses many magnetic anomalies. Though most of these are not associated with known geologic structures, some are found within large impact basins within the interior peak ring. The primary magnetic carrier in lunar rocks is metallic iron, but indigenous lunar rocks are metal poor and cannot account easily for the observed field strengths. The projectiles that formed the largest impact basins must have contained a significant quantity of metallic iron, and a portion of this iron would have been retained on the Moon's surface within the impact melt sheet. Here we use orbital magnetic field data to invert for the magnetization within large impact basins using the assumption that the crust is unidirectionally magnetized. We develop a technique based on laboratory thermoremanent magnetization acquisition to quantify the relationship between the strength of the magnetic field at the time the rock cooled and the abundance of metal in the rock. If we assume that the magnetized portion of the impact melt sheet is 1 km thick, we find average abundances of metallic iron ranging from 0.11% to 0.45 wt %, with an uncertainty of a factor of about 3. This abundance is consistent with the metallic iron abundances in sampled lunar impact melts and the abundance of projectile contamination in terrestrial impact melts. These results help constrain the composition of the projectile, the impact process, and the time evolution of the lunar dynamo.

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Untitled

1998

J. Geophys. Res.

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Late in the Moon's heavy bombardment period, the impact that formed the Imbrium Basin excavated and melted a tremendous volume of material that was subsequently distributed over most of the Moon's surface. The Apollo orbiting ¾ ray experiments [Metzger et al., 1977] show that the Imbrium projectile struck in a Th-rich area, called the High-Th Oval Region here and regarded as a unique lunar geochemical province. Imbrium primary ejecta were thus probably rich in Th. It is shown here using ejecta deposit modeling that the distribution of Th in the highlands surface along the ground tracks of the ¾ ray •ometers is consistent with the distribution expected for Imbrium ejecta deposits. Deep basins other than Imbrium appear to have excavated regions of lower crust that were mafic and Fe-bea_fing but not Th-rich. The possibility that the surface Th distribution arises mainly from Imbrium ejecta has implications for the nature of the Moon's igneous differentiation and the nature of the proposed "cataclysm" or late bombardment with large meteoroids. If Th concentrations in the highlands are plotted as a function of distance from Mare Imbrium (Figure 1; see also Figure 3 of Met•ger et al. [1974]), they are seen to drop off steeply from just beyond the eastern edge of Mare Imbrium, pass through a minimum, and rise to intermediate values as the maxim• distance from Imbrium is approached [Haskin, 1997]. This paper reports results of ejecta modeling that predicts a Th distribution close to the actual distribution if it is assumed the Imbrium ejecta are the sole or principal source of Th in the lunar highlands. It then considers the possible origin of the Th-rich Imbrium-Procellannn region. Based on the agreement between the Th distribution as modeled and the observed hi.ghland Th .djsLn.'bufion, *•,e fo!!ew

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Compositional variation in Apollo 16 impact-melt breccias and inferences for the geology and bombardment history of the Central Highlands of the Moon

Abstract: Abstract--High-precision

Cited by 95 publications

References 27 publications

The great lunar hot spot and the composition and origin of the Apollo mafic (“LKFM”) impact‐melt breccias

The great lunar hot spot and the composition and origin of the Apollo mafic (“LKFM”) impact‐melt breccias

Iron Abundances in Lunar Impact Basin Melt Sheets From Orbital Magnetic Field Data

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