Minerals 2014, 4(2), 503-518; doi:10.3390/min4020503
Chemical Abrasion Applied to LA-ICP-MS U–Pb Zircon Geochronology
1
Department of Geology, School of Natural Sciences, Trinity College, Dublin 2, Ireland
2
School of Earth Sciences and Environmental Sustainability, Northern Arizona University, Flagstaff, AZ 86011, USA
3
Geological Survey of Ireland, Beggars Bush, Dublin 4, Ireland
4
Tasiast Mauritanie Limited SA, ZRA 741, BP 5051, Nouakchott, Mauritania, West Africa
*
Author to whom correspondence should be addressed.
Received: 30 April 2014 / Revised: 19 May 2014 / Accepted: 23 May 2014 / Published: 3 June 2014
(This article belongs to the Special Issue Advances in Mineral Geochronology)
Abstract
Zircon (ZrSiO4) is the most commonly used mineral in U–Pb geochronology. Although it has proven to be a robust chronometer, it can suffer from Pb-loss or elevated common Pb, both of which impede precision and accuracy of age determinations. Chemical abrasion of zircon involves thermal annealing followed by relatively low temperature partial dissolution in HF acid. It was specifically developed to minimize or eliminate the effects of Pb-loss prior to analysis using Thermal Ionization Mass Spectrometry (TIMS). Here we test the application of chemical abrasion to Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) by analyzing zircons from both untreated and chemically abraded samples. Rates of ablation for high alpha-dose non-treated zircons are up to 25% faster than chemically abraded equivalents. Ablation of 91500 zircon reference material demonstrates a ca. 3% greater down-hole fractionation of 206Pb/238U for non-treated zircons. These disparities necessitate using chemical abrasion for both primary reference material and unknowns to avoid applying an incorrect laser induced fractionation correction. All treated samples display a marked increase in the degree of concordance and/or lowering of common Pb, thereby illustrating the effectiveness of chemical abrasion to LA-ICP-MS U–Pb zircon geochronology. View Full-TextKeywords:
U–Pb geochronology; zircon; chemical abrasion; Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS); Pb-loss
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Crowley, Q.G.; Heron, K.; Riggs, N.; Kamber, B.; Chew, D.; McConnell, B.; Benn, K. Chemical Abrasion Applied to LA-ICP-MS U–Pb Zircon Geochronology. Minerals 2014, 4, 503-518.
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