TY - JOUR
T1 - Precise and accurate in situ U-Pb dating of zircon with high sample throughput by automated LA-SF-ICP-MS
AU - Frei, Dirk
AU - Gerdes, Axel
N1 - Funding Information:
Christian Knudsen is thanked for his continuing support that was vital to make the LA-SF-ICP-MS facility at GEUS a reality. The establishment of the facility was funded by a grant from the Danish Ministry of Education and Technology to the Geocenter Copenhagen (Geocenterbevilling) and financial support by GEUS. We thank Julie Alison Hollis, Jørgen Kystol, Martina Frei and Julian Wills (ThermoScientific, Bremen) for their help and assistance during set-up of the facility. DF would like to thank Jan Košler for providing indispensable insights into laser ablation U–Pb age dating and analysis automation. The donation of the reference zircons used in this study by Lance Black, Dave Cornell, Jan Košler, Guido Meinhold and Andreas Mőller is greatly appreciated. Hanne Lamberts is thanked for her great expertise in preparing most of the grain mounts used in this study. The thoughtful and constructive reviews of Nigel Kelly and Jan Košler as well as the editorial comments by John Hanchar significantly improved the presentation of the subject, which is gratefully acknowledged. Finally, Alex Kovalev is thanked for his tiredless efforts to hold the torch high. This paper is published with the permission of the Geological Survey of Denmark and Greenland.
PY - 2009/4/30
Y1 - 2009/4/30
N2 - We present an automated method for U-Pb age dating of zircon by single collector laser ablation-magnetic sectorfield-inductively coupled plasma-mass spectrometry (LA-SF-ICP-MS). The high sensitivity of SF-ICP-MS allows routine analysis with spot diameter of 20 to 30 μm and ablation time of 30 s, resulting in an ablation crater depth of ∼ 15-20 μm (∼ 35 to ∼ 65 ng of zircon). Zircon consumption is therefore limited to < 3% of a typical crystal and only by a factor of 6-10 times larger compared to secondary ion mass spectrometry (SIMS) based techniques. Precision and accuracy has been assessed using a number of well-characterised zircons as secondary quality control standards and are comparable to those of laser ablation- and ion-microprobe based techniques that use more complex and time-consuming approaches. Average measurement uncertainties (2σ, mean analytical uncertainty) based on 402 analyses of the Plešovice zircon standard were 2.2%, 3.1% and 2.1% for the
206Pb/
238U,
207Pb/
235U and
207Pb/
206Pb ratios, respectively, comparable with those attainable by SIMS. The weighted mean of all 402 analyses yielded a
206Pb/
238U age of 338 ± 1 Ma, which is in excellent agreement with the ID-TIMS
206Pb/
238U age of 337.1 ± 0.4 Ma reported for the Plešovice zircon. Data acquisition is done in automated mode for up to 16 h/day with analytical points pre-set with only minimal operator presence during the data acquisition. Individual U-Pb zircon analysis last ≤ 75 s, and sample throughput is more than an order of magnitude higher (∼ 1000 U-Pb ages/day) compared to SIMS techniques and 3-5 fold higher compared to conventional LA-ICP-MS techniques. The methods presented here are therefore expected to have significant impact on many aspects of zircon U-Pb geochronology, with particular benefits for studies on the Archean crustal evolution and the provenance of detrital zircon crystals from clastic sediments where a large number of high-quality stand-alone in situ zircon U-Pb age determinations are needed.
AB - We present an automated method for U-Pb age dating of zircon by single collector laser ablation-magnetic sectorfield-inductively coupled plasma-mass spectrometry (LA-SF-ICP-MS). The high sensitivity of SF-ICP-MS allows routine analysis with spot diameter of 20 to 30 μm and ablation time of 30 s, resulting in an ablation crater depth of ∼ 15-20 μm (∼ 35 to ∼ 65 ng of zircon). Zircon consumption is therefore limited to < 3% of a typical crystal and only by a factor of 6-10 times larger compared to secondary ion mass spectrometry (SIMS) based techniques. Precision and accuracy has been assessed using a number of well-characterised zircons as secondary quality control standards and are comparable to those of laser ablation- and ion-microprobe based techniques that use more complex and time-consuming approaches. Average measurement uncertainties (2σ, mean analytical uncertainty) based on 402 analyses of the Plešovice zircon standard were 2.2%, 3.1% and 2.1% for the
206Pb/
238U,
207Pb/
235U and
207Pb/
206Pb ratios, respectively, comparable with those attainable by SIMS. The weighted mean of all 402 analyses yielded a
206Pb/
238U age of 338 ± 1 Ma, which is in excellent agreement with the ID-TIMS
206Pb/
238U age of 337.1 ± 0.4 Ma reported for the Plešovice zircon. Data acquisition is done in automated mode for up to 16 h/day with analytical points pre-set with only minimal operator presence during the data acquisition. Individual U-Pb zircon analysis last ≤ 75 s, and sample throughput is more than an order of magnitude higher (∼ 1000 U-Pb ages/day) compared to SIMS techniques and 3-5 fold higher compared to conventional LA-ICP-MS techniques. The methods presented here are therefore expected to have significant impact on many aspects of zircon U-Pb geochronology, with particular benefits for studies on the Archean crustal evolution and the provenance of detrital zircon crystals from clastic sediments where a large number of high-quality stand-alone in situ zircon U-Pb age determinations are needed.
KW - Geochronology
KW - Laser ablation ICP-MS
KW - Magnetic sectorfield ICP-MS
KW - Plešovice
KW - U-Pb dating
KW - Zircon
UR - http://www.scopus.com/inward/record.url?scp=63249120054&partnerID=8YFLogxK
U2 - 10.1016/j.chemgeo.2008.07.025
DO - 10.1016/j.chemgeo.2008.07.025
M3 - Article
SN - 0009-2541
VL - 261
SP - 261
EP - 270
JO - Chemical Geology
JF - Chemical Geology
IS - 3-4
ER -