School of Engineering and Science - Jacobs University

1.50 FeR-2 (n=3)
1.25
JUB / reference average
1.00
0.75
0.50
0.25
0.00
Sc Ti Co Ni Rb Sr Y Zr Nb Mo Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Pb Th U
Figure 12. Accuracy estimation for ICPMS analysis of iron-formation FeR-2, where n equals the
number of separate HF-HClO 4 sample decompositions and ICPMS analyses in 0.5 M HCl. Grey bars
represent variability in the calculated ratio that is due solely to uncertainty in the reference average.
Vertical lines represent the variability in the calculated ratio due to the uncertainty of the JUB data, and
all data are presented in App. 1. Precision of JUB data is generally better than that observed for the
average reference values, particularly for elements with atomic masses >100 amu (i.e., heavier than
Mo). Measured JUB data for higher mass elements are generally lower than the reference average,
though this reference average is skewed to higher values by the data of Yu et al. (2001) (see text for
details and App. 1). Data for Nb not included due to probable FeCl interferences and large uncertainty
in JUB data for Nb measurements (70% RSD).
FeR-2 compared to very Al-poor IFs. For FeR-2, the standard deviation of the JUB
data is typically 1-3%, considerably better than the range observed in the literature
data (App. 1). The JUB data tends to be somewhat lower than the reference value
average, with 25 of the 32 elements analyzed displaying concentrations between 85–
100% of the literature data (Fig. 12). However, the average reference values for many
elements are skewed towards higher numbers by the data of a single study (Yu et al.,
2001), and if the data from Yu et al. (2001) are not considered, then measured JUB
concentrations for 24 of 32 elements are within 90-110% of reference values (see
App. 1).
FeR-4
The FeR-4 iron-formation has very similar SiO 2 (50.1%) and Fe 2 O 3 (39.2%)
contents compared to FeR-2, but only one-third as much Al 2 O 3 (1.70%).
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