TY - JOUR
T1 - U and Th zonation in Fish Canyon Tuff zircons
T2 - implications for a zircon (U-Th)/He standard
AU - Dobson, Katherine J.
AU - Stuart, Finlay M.
AU - Dempster, Tim J.
PY - 2008/10/1
Y1 - 2008/10/1
N2 - The inability to accurately determine the distribution of U and Th in zircon crystals analysed using (U-Th)/He is a major source of error, and limits the confidence in subsequent data interpretation. The Fish Canyon Tuff (FCT) zircon standard shows (U-Th)/He age reproducibility in excess of ±10%. We have tested the extent to which this is due to U and Th zonation using a combination of cathodoluminescence and ion probe analysis of a population of FCT zircons. Primarily we find that FCT zircons exhibit extreme U and Th zonation, and the population has large inter-crystalline variability. Furthermore, the net cathodoluminescence intensity from the FCT zircons is negatively correlated with U and Th concentration, allowing cathodoluminescence emission to be used as a proxy for U and Th zonation. This correlation was exploited to constrain the U and Th zonation within the crystal population, and to show that the poor age reproducibility of the FCT zircons is consistent with the observed zonation.
AB - The inability to accurately determine the distribution of U and Th in zircon crystals analysed using (U-Th)/He is a major source of error, and limits the confidence in subsequent data interpretation. The Fish Canyon Tuff (FCT) zircon standard shows (U-Th)/He age reproducibility in excess of ±10%. We have tested the extent to which this is due to U and Th zonation using a combination of cathodoluminescence and ion probe analysis of a population of FCT zircons. Primarily we find that FCT zircons exhibit extreme U and Th zonation, and the population has large inter-crystalline variability. Furthermore, the net cathodoluminescence intensity from the FCT zircons is negatively correlated with U and Th concentration, allowing cathodoluminescence emission to be used as a proxy for U and Th zonation. This correlation was exploited to constrain the U and Th zonation within the crystal population, and to show that the poor age reproducibility of the FCT zircons is consistent with the observed zonation.
KW - Zircon (U-Th)/He thermochronology
KW - Fish Canyon Tuff
KW - reproducability
KW - zonation
UR - http://www.scopus.com/inward/record.url?scp=51549118442&partnerID=8YFLogxK
U2 - 10.1016/j.gca.2008.07.015
DO - 10.1016/j.gca.2008.07.015
M3 - Article
AN - SCOPUS:51549118442
VL - 72
SP - 4745
EP - 4755
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
SN - 0016-7037
IS - 19
ER -