New Views of Lunar Geoscience: An Introduction and Overview

Hiesinger, H.; Head, J. W.

doi:10.2138/rmg.2006.60.1

Cited by 193 publications

(147 citation statements)

References 281 publications

(377 reference statements)

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“…However, the radiogenic ages of basaltic lunar meteorites extend the duration of mare volcanism to younger ages ≤3 Ga. Borg et al (2009) reported Nd-Sm crystallization ages of 2.993 ± 0.032 Ga for an olivine cumulate gabbro (OC) clast from the basaltic breccia Northwest Africa (NWA) 773 and 2.931 ± 0.092 Ga for mare basalt NWA 032; Wang et al (2012) gave a Pb-Pb crystallization age of 3.073 ± 0.015 Ga for Zr-rich minerals in mare basalt NWA 4734; Anand et al (2006) reported a U-Pb age of 2.929 ± 0.15 Ga for phosphates in mare basalt LaPaz Icefield (LAP) 02205. These younger ages are consistent with the model ages based on crater counts from mare surfaces (Hiesinger and Head 2006). The presence of mare surfaces younger than ≤3 Ga has been verified by Morota et al (2011) in the Procellarum KREEP Terrane (PKT), where incompatible elements such as K, Th, and U and rare earth elements (REE) are highly concentrated (Jolliff et al 2000).…”

Section: Introductionsupporting

confidence: 83%

Mineralogy and petrology of lunar meteorite Northwest Africa 2977 consisting of olivine cumulate gabbro including inverted pigeonite

et al. 2015

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Lunar meteorite Northwest Africa (NWA) 2977 is identified as an olivine cumulate gabbro (OC), consisting of coarse cumulate olivine crystals up to 1 mm with low-Ca and high-Ca pyroxenes, plagioclase, and interstitial incompatible element-rich pockets of K-feldspar, Ca-phosphates, ilmenite, and troilite. These minerals and textures are similar to those of the OC clasts of the NWA 773 clan of meteorites. NWA 2977 contains a variety of pyroxene textures and compositions including augite, pigeonite, and rare orthopyroxene, all having exsolution lamellae. Some of the orthopyroxene has abundant augite lamellae with compositions indicating formation by inversion of pigeonite. This pigeonite was inverted at 1140°C according to the pigeonite eutectoid reaction (PER) temperatures. Inverted pigeonite has not been found previously in the NWA 773 clan of meteorites. The presence of inverted pigeonite indicates that NWA 2977 cooled more slowly than most other OC clasts of the NWA 773 clan. The relatively slow cooling of NWA 2977 can be explained by formation in a deeper level of the original igneous body of the NWA 773 clan OC lithology.

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Section: Introductionsupporting

confidence: 83%

Mineralogy and petrology of lunar meteorite Northwest Africa 2977 consisting of olivine cumulate gabbro including inverted pigeonite

et al. 2015

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“…We have distinguished at least three distinct shock-generated assemblages: 1) a prematrix assemblage comprising lithic and mineral clasts that have undergone different degrees of shock. The clasts retain evidence of having been shocked between 5-28 GPa (shock stages S1-S2), based on the summary of Hiesinger and Head (2006); 2) a shock melting event that produced the fine-grained igneous matrix of the meteorite. Formation of the matrix would have required relatively high shock pressures (>60 GPa).…”

Section: Shock Historymentioning

confidence: 96%

“…Based on the shock classification summary of Hiesinger and Head (2006), formation of the melt that cooled to form the matrix would have required shock pressures >60 GPa (shock stage S4). The presence of melt pockets and veins indicates a later shock excursion event, which locally attained shock pressures of 28-45 GPa (shock stage S2-S3).…”

Section: Shock Classificationmentioning

confidence: 99%

“…SaU 300 can be assigned to a shock stage that is not dependent on measurement of the absolute shock pressure, but relative to an existing shock recovery database (see Hiesinger and Head 2006 for compiled data). The bulk of the mineral and lithic clasts belong to shock stage 1b of Stöffler et al (1980), which corresponds to an equilibration shock pressure of 20-22 GPa and a post-shock temperature of 200°C.…”

Section: Shock Classificationmentioning

confidence: 99%

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Mineralogy, petrology, and shock history of lunar meteorite Sayh al Uhaymir 300: A crystalline impact‐melt breccia

Hudgins

Walton

Spray

2007

Meteorit & Planetary Scien

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Abstract-Sayh al Uhaymir (SaU) 300 comprises a microcrystalline igneous matrix (grain size <10 μm), dominated by plagioclase, pyroxene, and olivine. Pyroxene geothermometry indicates that the matrix crystallized at ~1100 °C. The matrix encloses mineral and lithic clasts that record the effects of variable levels of shock. Mineral clasts include plagioclase, low-and high-Ca pyroxene, pigeonite, and olivine. Minor amounts of ilmenite, FeNi metal, chromite, and a silica phase are also present. A variety of lithic clast types are observed, including glassy impact melts, impact-melt breccias, and metamorphosed impact melts. One clast of granulitic breccia was also noted. A lunar origin for SaU 300 is supported by the composition of the plagioclase (average An 95 ), the high Cr content in olivine, the lack of hydrous phases, and the Fe/Mn ratio of mafic minerals. Both matrix and clasts have been locally overprinted by shock veins and melt pockets. SaU 300 has previously been described as an anorthositic regolith breccia with basaltic components and a granulitic matrix, but we here interpret it to be a polymict crystalline impact-melt breccia with an olivine-rich anorthositic norite bulk composition. The varying shock states of the mineral and lithic clasts suggest that they were shocked to between 5-28 GPa (shock stages S1-S2) by impact events in target rocks prior to their inclusion in the matrix. Formation of the igneous matrix requires a minimum shock pressure of 60 GPa (shock stage >S4). The association of maskelynite with melt pockets and shock veins indicates a subsequent, local 28-45 GPa (shock stage S2-S3) excursion, which was probably responsible for lofting the sample from the lunar surface. Subsequent fracturing is attributed to atmospheric entry and probable breakup of the parent meteor.

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“…It has been proposed that, at the landing site, the regolith, with a depth of 5-12 m (Eggleton and Offield 1970) or 10-20 m (Swan et al 1971), overlays the Fra Mauro Formation, interpreted as representing the Imbrium basin ejecta sheet, with an estimated thickness of 100-200 m (Wilhems 1987). The presence of boulders, including complex fragmental breccias, impact-melt breccias and clast-poor impact melts with generally basaltic and KREEP-rich compositions at the surface (Hiesinger and Head 2006) has been attributed to ejection of Fra Mauro Formation material during impact formation of the 25 Ma old Cone crater (Turner et al 1971;Wilhelms 1987). However, Heisinger and Head (2006) comment "that it is still unclear which Apollo 14 samples represent true Imbrium ejecta and which represent locally derived materials."…”

Section: Apollo 14 Samplesmentioning

confidence: 99%

The comparative behavior of apatite‐zircon U‐Pb systems in Apollo 14 breccias: Implications for the thermal history of the Fra Mauro Formation

Nemchin

Pidgeon

Healy

et al. 2009

Meteorit & Planetary Scien

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Abstract-We report secondary ion mass spectrometry (SIMS) U-Pb analyses of zircon and apatite from four breccia samples from the Apollo 14 landing site. The zircon and apatite grains occur as cogenetic minerals in lithic clasts in two of the breccias and as unrelated mineral clasts in the matrices of the other two. SIMS U-Pb analyses show that the ages of zircon grains range from 4023 ± 24 Ma to 4342 ± 5 Ma, whereas all apatite grains define an isochron corresponding to an age of 3926 ± 3 Ma. The disparity in the ages of cogenetic apatite and zircon demonstrates that the apatite U-Pb systems have been completely reset at 3926 ± 3 Ma, whereas the U-Pb system of zircon has not been noticeably disturbed at this time. The apatite U-Pb age is slightly older than the ages determined by other methods on Apollo 14 materials highlighting need to reconcile decay constants used for the U-Pb, Ar-Ar and Rb-Sr systems. We interpret the apatite age as a time of formation of the Fra Mauro Formation. If the interpretation of this Formation as an Imbrium ejecta is correct, apatite also determines the timing of Imbrium impact. The contrast in the Pb loss behavior of apatite and zircon places constraints on the temperature history of the Apollo 14 breccias and we estimate, from the experimentally determined Pb diffusion constants and an approximation of the original depth of the excavated samples in the Fra Mauro Formation, that the breccias experienced an initial temperature of about 1300-1100 °C, but cooled within the first five to ten years.

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New Views of Lunar Geoscience: An Introduction and Overview

Cited by 193 publications

References 281 publications

Mineralogy and petrology of lunar meteorite Northwest Africa 2977 consisting of olivine cumulate gabbro including inverted pigeonite

Mineralogy and petrology of lunar meteorite Northwest Africa 2977 consisting of olivine cumulate gabbro including inverted pigeonite

Mineralogy, petrology, and shock history of lunar meteorite Sayh al Uhaymir 300: A crystalline impact‐melt breccia

The comparative behavior of apatite‐zircon U‐Pb systems in Apollo 14 breccias: Implications for the thermal history of the Fra Mauro Formation

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