TY - JOUR
T1 - High-Precision, High-Accuracy Oxygen Isotope Measurements of Zircon Reference Materials with the SHRIMP-SI
AU - Ávila, Janaína N.
AU - Ireland, Trevor R.
AU - Holden, Peter
AU - Lanc, Peter
AU - Latimore, Andrew
AU - Schram, Norm
AU - Foster, John
AU - Williams, Ian S.
AU - Loiselle, Liane
AU - Fu, Bin
N1 - Publisher Copyright:
© 2019 The Authors. Geostandards and Geoanalytical Research © 2019 International Association of Geoanalysts
PY - 2020/3/1
Y1 - 2020/3/1
N2 - Analytical protocols for SHRIMP-SI oxygen isotope analysis (δ18O) of a suite of zircon reference materials (RMs) are presented. Data reduction involved a robust estimate of uncertainties associated with the individual spot as well as for groups where the spot data are combined. The repeatability of δ18O measurements is dependent on both the analytical conditions and the choice of the primary reference material. Under optimised conditions, repeatability was often better than 0.4‰ (2s) allowing sample uncertainties to be obtained to better than 0.2‰ (at 95% confidence limit). Single spot uncertainty combined the within-spot precision with the scatter associated with repeated measurements of the primary zircon reference material during a measurement session. The uncertainty for individual spots measured under optimised conditions was between 0.3 and 0.4‰ (at 95% confidence). The analytical protocols described were used to assess a variety of zircon RMs that have been used for geochronology and for which laser fluorination oxygen isotope data are available (Temora 2, FC1, R33, QGNG and Plešovice), as well as zircons that have been used as RMs for trace element or other types of determination (Mud Tank, Monastery, 91500, AS57, AS3, KIM-5, OG1, SL13, CZ3 and several other Sri Lankan zircons). Repeated analyses over nine sessions and seven different mounts show agreement within analytical uncertainty for Temora 2, FC1, R33, QGNG, Plešovice and 91500, when normalised to Mud Tank. For existing ion microprobe mounts with these materials, an appropriate δ18O can be determined. However, care should be taken when using zircons from the Duluth Complex (i.e., FC1, AS57 and AS3) as reference materials as our data indicated an excess scatter on δ18O values associated with low-U zircon grains.
AB - Analytical protocols for SHRIMP-SI oxygen isotope analysis (δ18O) of a suite of zircon reference materials (RMs) are presented. Data reduction involved a robust estimate of uncertainties associated with the individual spot as well as for groups where the spot data are combined. The repeatability of δ18O measurements is dependent on both the analytical conditions and the choice of the primary reference material. Under optimised conditions, repeatability was often better than 0.4‰ (2s) allowing sample uncertainties to be obtained to better than 0.2‰ (at 95% confidence limit). Single spot uncertainty combined the within-spot precision with the scatter associated with repeated measurements of the primary zircon reference material during a measurement session. The uncertainty for individual spots measured under optimised conditions was between 0.3 and 0.4‰ (at 95% confidence). The analytical protocols described were used to assess a variety of zircon RMs that have been used for geochronology and for which laser fluorination oxygen isotope data are available (Temora 2, FC1, R33, QGNG and Plešovice), as well as zircons that have been used as RMs for trace element or other types of determination (Mud Tank, Monastery, 91500, AS57, AS3, KIM-5, OG1, SL13, CZ3 and several other Sri Lankan zircons). Repeated analyses over nine sessions and seven different mounts show agreement within analytical uncertainty for Temora 2, FC1, R33, QGNG, Plešovice and 91500, when normalised to Mud Tank. For existing ion microprobe mounts with these materials, an appropriate δ18O can be determined. However, care should be taken when using zircons from the Duluth Complex (i.e., FC1, AS57 and AS3) as reference materials as our data indicated an excess scatter on δ18O values associated with low-U zircon grains.
KW - SHRIMP
KW - high precision
KW - oxygen isotopes
KW - secondary ion mass spectrometer
KW - zircon
UR - http://www.scopus.com/inward/record.url?scp=85075423822&partnerID=8YFLogxK
U2 - 10.1111/ggr.12298
DO - 10.1111/ggr.12298
M3 - Article
SN - 1639-4488
VL - 44
SP - 85
EP - 102
JO - Geostandards and Geoanalytical Research
JF - Geostandards and Geoanalytical Research
IS - 1
ER -