Discussion of "New zircon shock phenomena and their use for dating and reconstruction of large impact structures revealed by electron nanobeam (EBSD, CL, EDS) and isotopic U-Pb and (U-Th)/He analysis of the Vredefort dome"

H. M. Rajesh, M. W. Knoper

Research output: Contribution to journalComment/debate

Abstract

Spodumene pegmatites occur in the southeastern sector of the 2.02 Ga Vredefort impact structure in South Africa. Moser et al. (published in 2011) presented an isotope dilution - thermal ionization mass spectrometry (ID-TIMS) age of 1136 ± 47 Ma for these spodumene pegmatites. This discussion questions the reliability of this age. Field relations indicate that the spodumene pegmatites are not affected by the structural fabric that affected the host amphibolites. The crosscutting impact-related veins of pseudotachylitic breccia clearly argues a preimpact age for the spodumene pegmatites. The high-uranium content of one of the two zircons used by Moser et al. to obtain the age is correlated to the ~1.1 Ga Pbloss event, widely observed in different rocks within the Vredefort impact structure.

Original languageEnglish
Pages (from-to)857-862
Number of pages6
JournalCanadian Journal of Earth Sciences
Volume49
Issue number7
DOIs
Publication statusPublished - Jul 1 2012

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impact structure
dome
zircon
electron
breccia
uranium
dilution
ionization
mass spectrometry
isotope
analysis
dating
rock

All Science Journal Classification (ASJC) codes

  • Earth and Planetary Sciences(all)

Cite this

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title = "Discussion of {"}New zircon shock phenomena and their use for dating and reconstruction of large impact structures revealed by electron nanobeam (EBSD, CL, EDS) and isotopic U-Pb and (U-Th)/He analysis of the Vredefort dome{"}",
abstract = "Spodumene pegmatites occur in the southeastern sector of the 2.02 Ga Vredefort impact structure in South Africa. Moser et al. (published in 2011) presented an isotope dilution - thermal ionization mass spectrometry (ID-TIMS) age of 1136 ± 47 Ma for these spodumene pegmatites. This discussion questions the reliability of this age. Field relations indicate that the spodumene pegmatites are not affected by the structural fabric that affected the host amphibolites. The crosscutting impact-related veins of pseudotachylitic breccia clearly argues a preimpact age for the spodumene pegmatites. The high-uranium content of one of the two zircons used by Moser et al. to obtain the age is correlated to the ~1.1 Ga Pbloss event, widely observed in different rocks within the Vredefort impact structure.",
author = "Rajesh, {H. M.} and Knoper, {M. W.}",
year = "2012",
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issn = "0008-4077",
publisher = "National Research Council of Canada",
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TY - JOUR

T1 - Discussion of "New zircon shock phenomena and their use for dating and reconstruction of large impact structures revealed by electron nanobeam (EBSD, CL, EDS) and isotopic U-Pb and (U-Th)/He analysis of the Vredefort dome"

AU - Rajesh, H. M.

AU - Knoper, M. W.

PY - 2012/7/1

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N2 - Spodumene pegmatites occur in the southeastern sector of the 2.02 Ga Vredefort impact structure in South Africa. Moser et al. (published in 2011) presented an isotope dilution - thermal ionization mass spectrometry (ID-TIMS) age of 1136 ± 47 Ma for these spodumene pegmatites. This discussion questions the reliability of this age. Field relations indicate that the spodumene pegmatites are not affected by the structural fabric that affected the host amphibolites. The crosscutting impact-related veins of pseudotachylitic breccia clearly argues a preimpact age for the spodumene pegmatites. The high-uranium content of one of the two zircons used by Moser et al. to obtain the age is correlated to the ~1.1 Ga Pbloss event, widely observed in different rocks within the Vredefort impact structure.

AB - Spodumene pegmatites occur in the southeastern sector of the 2.02 Ga Vredefort impact structure in South Africa. Moser et al. (published in 2011) presented an isotope dilution - thermal ionization mass spectrometry (ID-TIMS) age of 1136 ± 47 Ma for these spodumene pegmatites. This discussion questions the reliability of this age. Field relations indicate that the spodumene pegmatites are not affected by the structural fabric that affected the host amphibolites. The crosscutting impact-related veins of pseudotachylitic breccia clearly argues a preimpact age for the spodumene pegmatites. The high-uranium content of one of the two zircons used by Moser et al. to obtain the age is correlated to the ~1.1 Ga Pbloss event, widely observed in different rocks within the Vredefort impact structure.

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