Appendix 2. Analytical accuracy (observed versus expected values) and precision (coefficient of
variation) for geochemical data. ND not determined.
USGS-W-2 USGS-BCR-1
Weight Coefficient Percent Observed Expected Observed Expected of Variation
SiO2 52.1 52.1 54.6 54.89 0.49 TiO2 1.05 1.06 2.17 2.22 1.49 A1203 15.6 15.5 14.0 13.7 0.22 Fe203* 11.1 10.8 13.3 13.5 0.53 MnO 0.17 0.17 0.19 0.19 0.79 MgO 6.48 6.37 3.50 3.49 0.72 CaO 10.8 10.8 7.75 6.98 0.67 Na20 ND 2.20 3.24 3.29 0.34 K20 0.68 0.63 1.95 1.68 1.14 P205 0.17 0.14 0.39 0.33 8.69
PPM
Ba 175 174 748 675 1.06 Cr 73 92 [253 270 ]** 3.20 Cu 105 106 29 18 19.3 Ni 70 70 12 16 3.67 Rb 15 21 40 47 16.1 Sr 193 192 325 330 2.78 V 248 259 330 399 1.12 Y 29 23 39 37 18.5 Zn 78 80 115 120 1.99 Zr 114 100 212 190 5.32
S*Values for Cr in USGS-BCR-1 are below detection Bracketed values are from analyses of USGSDNC-1.
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