Thermal history of Apollo 12 granite and KREEP-rich rock: Clues from Pb/Pb ages of zircon in lunar breccia 12013

Zhang, Ai‐Cheng; Taylor, L. A.; Wang, Rucheng; Li, Qiuli; Li, Xian‐Hua; Patchen, A. D.; Liu, Yang

doi:10.1016/j.gca.2012.07.023

Cited by 24 publications

(12 citation statements)

References 52 publications

(132 reference statements)

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“…Dates for multiple lunar impacts, ranging from 4335 to 1407 Ma, have been proposed based on ages from individual zircons (Pidgeon et al, 2007;Nemchin et al, 2009;Zhang et al, 2012;Grange et al, 2011Grange et al, , 2013aGrange et al, , 2013b. However, most lunar zircons do not contain diagnostic shock features found in terrestrial shocked zircons (Pidgeon et al, 2011).…”

Section: Implications For Ages Of Deformed Lunar Zirconsmentioning

confidence: 99%

A terrestrial perspective on usingex situshocked zircons to date lunar impacts

Cavosie

Erickson

Timms

et al. 2015

Geology

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Deformed lunar zircons yielding U-Pb ages from 4333 Ma to 1407 Ma have been interpreted as dating discrete impacts on the Moon. However, the cause of age resetting in lunar zircons is equivocal; as ex situ grains in breccias, they lack lithologic context and most do not contain microstructures diagnostic of shock that are found in terrestrial zircons. Detrital shocked zircons provide a terrestrial analog to ex situ lunar grains, for both identifying diagnostic shock evidence and also evaluating the feasibility of dating impacts with ex situ zircons. Electron backscatter diffraction and sensitive high-resolution ion microprobe U-Pb analysis of zircons eroded from the ca. 2020 Ma Vredefort impact structure (South Africa) show that complete impact-age resetting did not occur in microstructural domains characterized by microtwins, planar fractures, and low-angle boundaries, which record ages from 2890 Ma to 2645 Ma. An impact age of 1975 ± 39 Ma was detected in neoblasts within a granular zircon that also contains shock microtwins, which link neoblast formation to the impact. However, we show that granular texture can form during regional metamorphism, and thus is not unique to impact environments. These results demonstrate that dating an impact with ex situ shocked zircon requires identifying diagnostic shock evidence to establish impact provenance, and then targeting specific age-reset microstructures. With the recognition that zircon can deform plastically in both impact and magmatic environments, age-resetting in lunar zircons that lack diagnostic shock deformation may record magmatic processes rather than discrete impacts. Identifying shock microstructures that record complete age resetting for geochronological analysis is thus crucial for constructing accurate zircon-based impact chronologies for the Moon, Earth, or other planetary bodies.

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Section: Implications For Ages Of Deformed Lunar Zirconsmentioning

confidence: 99%

A terrestrial perspective on usingex situshocked zircons to date lunar impacts

Cavosie

Erickson

Timms

et al. 2015

Geology

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“…) and zircons <4.1 Ga have often small grain sizes (<50 μm) and show evidence for partial Pb loss (textural or as discordant U‐Pb ages, Zhang et al. ; Crow et al. ; Thiessen et al.…”

Section: Discussionmentioning

confidence: 99%

“…If the zircon indeed crystallized from a KREEP-rich melt, the age of 3941 AE 5 Ma sets a constraint on the duration of KREEP magmatism on the Moon. KREEP magmatism was previously thought to have lasted either~400-500 Myr (Meyer et al 1996;Nemchin et al 2008) or, alternatively,~200-300 Myr (e.g., Zhang et al 2012;Crow et al 2017). The latter interpretation is based on zircon age distribution patterns from different Apollo landing sites, which only show a minor age peak at 3.9 Ga, which was interpreted as the Imbrium impact event (e.g., Liu et al 2012).…”

Section: Large Zircon Grainsmentioning

confidence: 99%

“…As such, lunar zircon has become a major tool to investigate the timing and evolution of KREEP magmatism. U-Pb zircon ages from samples collected at different Apollo landing sites show a wide variety of ages spreading from~3883 AE 6 to 4417 AE 6 Ma (e.g., Meyer et al 1996;Nemchin et al 2008Nemchin et al , 2009aSeddio et al 2014;Hopkins and Mojzsis 2015;Crow et al 2017), but together indicate the presence of major age peaks at~4.35,~4.20, and ~4.00 Ga. A more detailed evaluation of these ages reveals differences in the zircon age distributions between separate landing sites, such as the~3.90 and 4.00 Ga peaks observed in zircons from Apollo 12 and 14 (e.g., Nemchin et al 2008;Liu et al 2012;Zhang et al 2012), compared with the zircon populations identified in Apollo 17 samples which do not have any of these younger peaks and are typically older than 4.20 Ga and up to 4.42 Ga (Nemchin et al 2009a). More complexities emerge when looking in detail at the age distributions from individual landing sites, and even on the level of individual samples; for example, in samples collected during the Apollo 14 mission.…”

Section: Introductionmentioning

confidence: 98%

“…; Zhang et al. ), compared with the zircon populations identified in Apollo 17 samples which do not have any of these younger peaks and are typically older than 4.20 Ga and up to 4.42 Ga (Nemchin et al. ).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

U‐Pb SIMS ages of Apollo 14 zircon: Identifying distinct magmatic episodes

Thiessen

Nemchin

Snape

et al. 2019

Meteorit & Planetary Scien

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U‐Pb ages of zircon in four different Apollo 14 breccias (14305, 14306, 14314, and 14321) were obtained by secondary ion mass spectrometry. Some of the analyzed grains occur as cogenetic, poikilitic zircon grains in lithic clasts, revealing magmatic events at ~4286 Ma, ~4200–4220 Ma, and ~4150 Ma. The age distribution of the crystal clasts in the breccias exhibits a minor peak at ~4210 Ma, which can be attributed to a magmatic event, as recorded in zircon grains located in noritic clasts. An age peak at ~4335 Ma is present in all four breccias, as well as zircon grains from different Apollo landing sites, enhancing the confidence that these grains recorded a global zircon‐forming event. The overall age distribution among the four breccias exhibits minor differences between the breccias collected farther away from the Cone Crater and the ones collected within the continuous ejecta blanket of the Cone Crater. A granular zircon grain yielded a 207Pb/206Pb age of 3936 ± 8 Ma, which is interpreted as an impact event. A similar age of 3941 ± 5 Ma (n = 17, MSWD = 0.89, P = 0.58) was obtained for a large zircon grain (~430 × 340 μm in size). This grain might have crystallized in the same impact melt sheet which formed the granular zircon or the age is representative of the final extrusion of KREEP magma. The majority of zircon grains, however, occur as isolated crystal clasts within the matrix and their ages cannot be correlated with any real events (impact or magmatic) nor can the possibility be excluded that these ages represent partial resetting of the U‐Pb system.

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A 4.2 billion year old impact basin on the Moon: U–Pb dating of zirconolite and apatite in lunar melt rock 67955

Norman

Nemchin

2014

Earth and Planetary Science Letters

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Thermal history of Apollo 12 granite and KREEP-rich rock: Clues from Pb/Pb ages of zircon in lunar breccia 12013

Cited by 24 publications

References 52 publications

A terrestrial perspective on usingex situshocked zircons to date lunar impacts

A terrestrial perspective on usingex situshocked zircons to date lunar impacts

U‐Pb SIMS ages of Apollo 14 zircon: Identifying distinct magmatic episodes

A 4.2 billion year old impact basin on the Moon: U–Pb dating of zirconolite and apatite in lunar melt rock 67955

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