Coincidence in time of the Imbrium basin impact and Apollo 15 KREEP volcanic flows: The case for impact-induced melting

Ryder, G.

doi:10.1130/spe293-p11

Cited by 28 publications

(40 citation statements)

References 12 publications

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“…Partial melting of the mantle is found to occur over most of the Moon's history, and the maximum depth of melting is shown to increase with time to a depth of about 600 km. This model result is consistent with the long duration of mare volcanism (from at least 4.2 Ga [Taylor et al, 1983] to about 900 Ma [Schultz and Spudis, 1983]) as well as the depth of origin of mare basalts (<540 km [e.g., Longhi, 1992] [Ryder, 1994]. (4) The reason that an igneous protolith to the Low-K Fra Mauro ("LKFM") mafic impact-melt breccias has never been found is that this impact melt is a mixture, of which one component was initially molten [Spudis et al, 1991].…”

Section: In This Paper We First Argue (As Do Dolliff Et Al [This Isssupporting

confidence: 83%

“…Finally, we suggest that the 500-km seismic discontinuity may represent the maximum depth of melting of the mare source. A scenario similar to this was originally proposed by Ryder [1994]. He argued that the Apollo 15 KREEP basalts are extrusive volcanic rocks that were derived from the nearby Apennine bench [Spudis, 1978] and that these flows were indistinguishable in absolute age from that of the Imbrium impact.…”

Section: Kreep Terranementioning

confidence: 71%

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The “Procellarum KREEP Terrane”: Implications for mare volcanism and lunar evolution

Wieczorek¹,

Phillips²

2000

J. Geophys. Res.

306

332

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Abstract. Geophysical, remote-sensing, and sample data demonstrate that the Procellarum and Imbrium regions of the Moon make up a unique geochemical crustal province (here dubbed the Procellarum KREEP Terrane). Geochemical studies of Imbrium's ejecta and the crustal structure of the Imbrium and Serenitatis basins both suggest that a large portion of the lunar crust in this locale is composed of a material similar in composition to Apollo 15 KREEP basalt. KREEP basalt has about 300 times more uranium and thorium than chondrites, so this implies that a large portion of Moon's heat-producing elements is located within this single crustal province. The spatial distribution of mare volcanism closely parallels the confines of the Procellarum KREEP Terrane and this suggests a causal relationship between the two phenomena. We have modeled the Moon's thermal evolution using a simple thermal conduction model and show that as a result of the high abundance of heat-producing elements that are found in the Procellarum KREEP Terrane, partial melting of the underlying mantle is an inevitable outcome. Specifically, by placing a 10-km KREEP basalt layer at the base of the crust there, our model predicts that mare volcanism should span most of the Moon's history and that the depth of melting should increase with time to a maximum depth of about 600 km. We suggest that the 500-km seismic discontinuity that is observed in the Apollo seismic data may represent this maximum depth of melting. Our model also predicts that the KREEP basalt layer should remain partially molten for a few billion years. Thus the Imbrium impact event most likely excavated into a partially molten KREEP basalt magma chamber. We postulate that the KREEP basalt composition is a byproduct of mixing urKREEP with shallow partial melts of the underlying mantle. Since Mg-suite rocks are likely derived from crystallizing KREEP basalt, the provenance of these plutonic rocks is likely to be unique to this region of the Moon.

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Section: In This Paper We First Argue (As Do Dolliff Et Al [This Isssupporting

confidence: 83%

Section: Kreep Terranementioning

confidence: 71%

The “Procellarum KREEP Terrane”: Implications for mare volcanism and lunar evolution

Wieczorek¹,

Phillips²

2000

J. Geophys. Res.

306

332

View full text Add to dashboard Cite

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“…Nevertheless, the idea that impacts may initiate volcanic eruptions on Earth or even the Moon has been vetted many times in recent years (Elkins-Tanton et al, 2002;Glickson, 1999;Jones et al, 1998;Jones et al, 2001;Rampino, 1987;Rogers, 1982;Ryder, 1994). Most of these proposals reiterate the original idea of Ronca (1966) that ascribes impact-induced volcanism to decompression melting beneath the impact crater.…”

Section: Introductionmentioning

confidence: 84%

Impacts do not initiate volcanic eruptions: Eruptions close to the crater

Ivanov

Melosh

2003

Geol

115

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“…While many soils and breccias are enriched in KREEP, igneous rocks with the KREEP pattern are limited mainly to Apollo 15 KREEP basalts. These rocks are temporally and spatially related to the Imbrium impact event (Ryder, 1994;Papike et aI., 1998), and are possibly a result ofimpact-induced volcanism (Ryder, 1994). This limits the possible origin of a rock lacking any KREEP component to either someplace far from the Imbrium impact (e.g., the far side), or a period in the Moon's history before that impact occurred.…”

Section: A Sample Of the Far Side?mentioning

confidence: 99%

Northwest Africa 482: A crystalline impact‐melt breccia from the lunar highlands

Daubar

Kring

Swindle

et al. 2002

Meteorit & Planetary Scien

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Abstract-Northwest Africa 482 (NWA 482) is a crystalline impact-melt breccia from the Moon with highlands affinities. The recrystallized matrix and the clast population are both highly anorthositic. Clasts are all related to the ferroan anorthosite suite, and include isolated plagioclase crystals and lithic anorthosites, troctolites, and spinel troctolites. Potassium-, rare-earth-element-, and phosphorus-bearing (KREEP) and mare lithologies are both absent, constraining the source area of this meteorite to a highland terrain with little to no KREEP component, most likely on the far side of the Moon. Glass is present in shock veins cutting through the sample and in several large melt pockets, indicating a second impact event.There are two separate events recorded in the 40Ar-39Ar system: one at -3750 Ma, which completely reset the K-Ar system, and one at :::;2400 Ma, which caused only partial degassing. These events could represent, respectively, crystallization ofthe impact-melt breccia and later formation of the glass, or the formation of the glass and a later thermal event.The terrestrial age of the meteorite is 8.6 ± 1.3 ka. This age corresponds well with the modest amount ofweathering in the rock, in the form of secondary phyllosilicates and carbonates. Based on terrestrial age and location, lithology, and chemistry, NWA 482 is unique among known lunar meteorites.

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Coincidence in time of the Imbrium basin impact and Apollo 15 KREEP volcanic flows: The case for impact-induced melting

Cited by 28 publications

References 12 publications

The “Procellarum KREEP Terrane”: Implications for mare volcanism and lunar evolution

The “Procellarum KREEP Terrane”: Implications for mare volcanism and lunar evolution

Impacts do not initiate volcanic eruptions: Eruptions close to the crater

Northwest Africa 482: A crystalline impact‐melt breccia from the lunar highlands

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