scholarly journals A new istopic and trace-element standard for the ion microprobe: preliminary thermal ionization mass spectrometry (TIMS) U-PB and electron-microprobe data; Radiogenic age and isotopic studies: Report 14

2001 ◽  
Author(s):  
R A Stern
Keyword(s):  
Mass Spectrometry ◽  
Trace Element ◽  
Electron Microprobe ◽  
Thermal Ionization Mass Spectrometry ◽  
Thermal Ionization ◽  
Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Ion Microprobe ◽  
Isotopic Studies ◽  
Thermal Ionization Mass

scholarly journals Stepwise chemical abrasion–isotope dilution–thermal ionization mass spectrometry with trace element analysis of microfractured Hadean zircon

Geochronology ◽  
2019 ◽  
Vol 1 (1) ◽  
pp. 85-97
Author(s):  
C. Brenhin Keller ◽  
Patrick Boehnke ◽  
Blair Schoene ◽  
T. Mark Harrison
Keyword(s):  
Mass Spectrometry ◽  
Trace Element ◽  
Thermal Ionization Mass Spectrometry ◽  
Trace Element Analysis ◽  
Thermal Ionization ◽  
Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Element Analysis ◽  
Thermal Ionization Mass ◽  
Jack Hills

Abstract. The Hadean Jack Hills zircons represent the oldest known terrestrial material, providing a unique and truly direct record of Hadean Earth history. This zircon population has been extensively studied via high-spatial-resolution high-throughput in situ isotopic and elemental analysis techniques, such as secondary ionization mass spectrometry (SIMS), but not by comparatively destructive, high-temporal-precision (<0.05 % two-sigma) thermal ionization mass spectrometry (TIMS). In order to better understand the lead loss and alteration history of terrestrial Hadean zircons, we conduct stepwise chemical abrasion–isotope dilution–thermal ionization mass spectrometry with trace element analysis (CA-ID-TIMS-TEA) on manually microfractured Hadean Jack Hills zircon fragments previously dated by SIMS. We conducted three successive HF leaching steps on each individual zircon fragment, followed by column chromatography to isolate U–Pb and trace element fractions. Following isotopic and elemental analysis, the result is an independent age and trace element composition for each leachate of each zircon fragment. We observe ∼50 Myr of age heterogeneity in concordant residues from a single zircon grain, along with a protracted history of post-Hadean Pb loss with at least two modes circa ∼0 and 2–4 Ga. Meanwhile, stepwise leachate trace element chemistry reveals enrichments of light rare earth elements, uranium, thorium, and radiogenic lead in early leached domains relative to the zircon residue. In addition to confirming the efficacy of the LREE-I alteration index and providing new insight into the mechanism of chemical abrasion, the interpretation and reconciliation of these results suggest that Pb loss is largely driven by low-temperature aqueous recrystallization and that regional thermal events may act to halt – not initiate – Pb loss from metamict domains in the Hadean Jack Hills zircons.

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