Hf isotope compositions of U.S. Geological Survey reference materials

Abstract

. Reproducibility is better than 50 ppm for the granitoid compositions and better than 40 ppm for the basaltic/andesitic compositions. For the isotopic analyses acquired early in this project on glass columns, Hf isotopic analyses from several of the reference materials were significantly less reproducible than Nd and Sr isotopic analyses determined from the same sample dissolution. The 176 Hf/ 177 Hf ratios for relatively radiogenic compositions (BCR-1, 2; BHVO-1, 2; RGM-1) were shifted systematically toward lower values by 100-150 ppm when a borosilicate primary column was used. Although systematic, the shift for felsic compositions was generally within analytical error, except for GSP-2, which has a very low Hf isotopic ratio, where the shift was to higher Hf and high Hf concentrations of the borosilicate glass column (16 ppm) and frit material (22 ppm) indicate that only small amounts of such unradiogenic material could cause significant contamination of small samples. For the basaltic (BCR-1, 2; BHVO-1, 2) and rhyolitic (RGM-1) samples, approximately 3 ng of Hf from the column or frit would be enough to produce the observed 100-150 ppm shift. Accurate, high-precision 176 Hf/ 177 Hf data can only be acquired if samples are processed using all PTFE Teflon 1 labware, or quartz and polypropylene.

Petrogenesis of the 1.9 Ga mafic hanging wall sequence to the Flin Flon, Callinan, and Triple 7 massive sulphide deposits, Flin Flon, Manitoba, CanadaThis is a companion paper to DeWolfe, Y.M., Gibson, H.L., Lafrance , B., and Bailes, A.H. 2009. Volcanic reconstruction of Paleoproterozoic arc volcanoes: the Hidden and Louis formations, Flin Flon, Manitoba, Canada. Canadian Journal of Earth Sciences, 46: this issue.

“…Hafnium isotopic geochemistry was also completed at the Pacific Centre for Isotopic and Geochemical Research using TIMS, following the methods of Weis et al (2007). Values for the USGS reference standards BHVO-1 and BCR-2 yielded average 176 Hf/ 177 Hf ratios of 0.283102 and 0.282869, respectively, with analytical uncertainties of ± 0.0000015 and 0.0000016 (2s), respectively.…”

Evidence for trench-parallel mantle flow in the northern Cascade Arc from basalt geochemistry

“…Interaction with crustal rocks can therefore mimic many of the geochemical patterns considered 'diagnostic' of slab-derived contributions (Mullen and Weis, 2013). Crustal contamination is also likely to have different geochemical effects at each GVB volcanic center due to the wide range of lithologies present within the array of accreted terranes and Mesozoic plutonic rocks that comprise the GVB basement (Wheeler and McFeely, 1991). Complete geochemical datasets for basement rocks underlying each GVB volcanic center will be required to fully test crustal contamination hypotheses.…”

Assimilation of preexisting Pleistocene intrusions at Long Valley by periodic magma recharge accelerates rhyolite generation: rethinking the remelting model

“…Samples were run on four separate days. Internal normalization was made using the well-characterized ULB-JMC Hf isotope standard (JMC 475) Hf value measured for the USGS granite standard G-2 of 0.282518 ± 2 compares favorably to the accepted reference value of 0.282523 ± 6 (Weis et al 2007). Bryce et al (2005).…”