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1. Analytical Methods
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1.1. Hf, Pb, Sr and Nd chemical separation and mass spectrometry
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New Hf-Pb-Sr-Nd isotopic measurements on glasses and whole rock powders are
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reported in Table 2. The majority of analyses were carried out on >200 mg of fresh glass
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chips (or whole rock powder), but only ~100 mg of glass available was available for a
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few of the samples. Nineteen samples of glass chips and one whole rock powder (sample
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4-1) were acid leached and dissolved at the Ecole Normale Supérieure in Lyon (ENS
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Lyon) following the protocols of Blichert-Toft et al. [1997] and Blichert-Toft and
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Albarède [2009]. The samples were leached in 2 ml of 6N HCl for 20 minutes at 120° C,
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followed by 10 minutes of sonication. Samples were leached again at 120° C for an
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additional 10 minutes, followed by 5 minutes of sonication and then 5 more minutes of
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leaching at 120° C; the HCl was pipetted off and the samples were rinsed twice in milliQ
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H2O.
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Dissolution in concentrated HF and HNO3 and chemical separation of Hf by
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anion- and cation-exchange columns followed the methods outlined by Blichert-Toft et
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al. [1997]. An additional six samples were leached and dissolved at Boston University
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(BU), and the leaching procedure followed the same protocol as that used at ENS Lyon.
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Pb, Sr and Nd retained in the CaMg-fluoride precipitate (left after removal of Hf by HF
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leaching at ENS Lyon) and Pb, Sr and Nd for samples leached at BU, were separated
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from all 26 samples using cation-exchange chemistry at BU. A number of replicates also
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were analyzed (Table 2), all on different aliquots of glass (from the same sample).
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Replicates samples were picked separately, leached separately (in 6N HCl at 110° C for
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20 minutes) dissolved separately, run on separate columns (on different days than the
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original analyses) and analyzed during different analytical sessions on the mass
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spectrometer. These replicate measurements provide conservative estimates of the long-
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term reproducibility of isotopic analyses of unknown basaltic samples. Pb was purified
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using Biorad AG1-X8 resin (100-200 μm), Sr was separated using Eichrom Sr resin (25-
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50 μm), and Nd was purified using a two-step Nd separation method that first used
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Eichrom TRU resin (100-150 μm) followed by Eichrom LN-Spec resin (50-100 μm).
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Strontium and Nd were recovered from the clean wash of the Pb columns. This wash
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fraction was split in two, one destined for the Sr separation protocol and the other
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destined for the Nd separation protocol. In this manner, Hf, Pb, Nd, and Sr were all
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separated from the same sample dissolutions, thereby minimizing glass consumption and
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avoiding potential problems due to possible sample heterogeneity that could lead to
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isotopic variations. The total procedural blanks for Hf, Pb, Sr and Nd were < 20 pg, < 30
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pg, < 80 pg and < 35 pg, respectively, which are all negligible relative to the amount of
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Sr, Nd and Pb analyzed in the rocks.
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Hafnium isotopic compositions were determined by multi-collector inductively
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coupled plasma mass spectrometry (MC-ICP-MS) on the Nu Plasma HR at ENS Lyon
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during October and November of 2012. All Pb, Sr and Nd isotopic measurements were
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performed on the Neptune MC-ICP-MS at Woods Hole Oceanographic Institution
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(WHOI) at the end of 2012 and the first half of 2013, following recent replacement of the
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Faraday collectors. The following outlines the mass spectrometry protocols used for the
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analyses of Hf, Pb, Sr and Nd isotopic compositions of this study:
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Hafnium. Hafnium isotopic measurements followed the protocol described by Blichert-
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Toft et al. [1997]. The Hf standard JMC-475 was analyzed between every second to
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fourth sample depending on machine stability. The unweighted mean 176Hf/177Hf ratios
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of the JMC-475 standard obtained during each of three day-long sessions of collection of
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the present Hf isotope data were 0.282166, 0.282170 and 0.282170. Since these values
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are identical within error to the accepted value of 0.282163 ± 0.000009 [Blichert-Toft et
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al., 1997] for JMC-475, no corrections were applied to the data collected on basalts. All
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measured Hf isotopic ratios were corrected online for isobaric interferences of W and Ta
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on mass 180 and Lu and Yb on mass 176 by monitoring the interference-free isotopes
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183
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fractionation by normalizing 179Hf/177Hf to 0.7325 using an exponential law. Lutetium
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and Yb interferences on 176Hf were insignificant for all samples analyzed. The external
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precision of 176Hf/177Hf based is estimated to be 10-30 ppm (2σ).
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Lead. Lead isotopic ratios were corrected for instrumental mass bias by introducing Tl
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(SRM 997) as an internal standard to sample Pb solutions prior to each run assuming a
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205
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correct for 204Hg interference, but this correction was small owing to low 202Hg/208Pb
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ratios (typically < 1.0x10-5). Measured Pb-isotopic ratios of the samples were normalized
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based on the offset between our average measured and the accepted SRM981 values from
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Todt et al. [1996] (206Pb/204Pb =16.9356, 207Pb/204Pb =15.4891, 208Pb/204Pb =36.7006).
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External reproducibility on runs of SRM981 at WHOI ranges from 17 ppm (2σ) for
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207
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Strontium. During each analytical session, intensities were measured on masses 82
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through 88. Corrections for isobaric interferences of Rb on mass 87 and Kr on masses 84
W, 181Ta, 175Lu and 173Yb, respectively. The data were corrected for instrumental mass
Tl/203Tl ratio of 2.38709 and using an exponential law. Mass 202 was monitored to
Pb/206Pb to 117 ppm (2σ) for 208Pb/204Pb [Hart et al., 2004].
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and 86 were made offline following the procedures outlined in Jackson and Hart [2006].
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Runs with low intensities (i.e., <3 V on mass 88, with a 1011 Ω resistor) were discarded.
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Strontium isotope ratios were corrected for instrumental mass bias relative to an 86Sr/88Sr
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value of 0.1194 using an exponential law.
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normalized by the offset between our average measured value of SRM987 during each
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analytical session and the accepted 87Sr/86Sr of 0.710240 [Jackson and Hart, 2006]. The
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external precision of the 87Sr/86Sr measurements is estimated to be 15–25 ppm (2σ) [Hart
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and Blusztajn, 2006].
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Neodymium. The data were corrected for instrumental mass fractionation relative to a
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146
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standards were run during each analytical session. The 143Nd/144Nd values for JNDi-1
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were adapted to the La Jolla 143Nd/144Nd value using a using a ratio of 1.000503 [Tanaka
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et al., 2000]. The La Jolla and La Jolla-renormalized-JNdi-1 143Nd/144Nd measurements
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were averaged to give a final La Jolla average for each analytical session. Samples were
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normalized based on the offset of this La Jolla average and the La Jolla 143Nd/144Nd value
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of 0.511847 that we adopt here [White and Patchett, 1984]. The external precision of the
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143
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2006].
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Sr/86Sr ratios for unknowns were then
Nd/144Nd value of 0.7219 using an exponential law. Both the La Jolla and JNdi-1
Nd/144Nd measurements is estimated to be 15–25 ppm (2σ). ) [Hart and Blusztajn,
The well-characterized international rock standards BCR-2 and AGV-2 were
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dissolved, processed, and analyzed similarly to and along with unknowns (although rock
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standards were not leached) during each batch of column chemistry and each analytical
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session. Two BCR-2 standards were measured for Hf isotopes in this study
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(Supplementary Table 1) and yielded 176Hf/177Hf of 0.282882±4 (2σ) and 0.282884±5
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(2σ), which compare well with the value of 0.282884±7 (2σ) reported by Le Fevre and
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Pin [2001] for BCR-2. Furthermore, the BCR-1 value of 0.282879±8 (2σ) reported by
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Blichert-Toft [2001] and measured in the same laboratory (ENS Lyon) compares well
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with the BCR-2 standards from this study. Results for Pb, Sr and Nd isotopic
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measurements of the BCR-2 and AGV-2 rock standards (this study, Supplementary Table
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1) likewise compare well with those of Weis et al. [2006] (Supplementary Fig. 1). In
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particular, we note that the 87Sr/86Sr ratios for BCR-2 and AGV-2 measured on the
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Neptune MC-ICP-MS in this study, compare well with the measurements of the same
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rock standards determined on a Triton TIMS in Weis et al. [2006] (thermal ionization
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mass spectrometer) (Supplementary Fig. 1 and Supplementary Table 1).
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1.2. He isotopic analyses
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Helium isotopes were measured on clean glass chips at WHOI using an automated
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dual-collection, statically-operated helium isotope mass spectrometer. Measurements
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were all made by crushing in vacuo, following the protocol of Kurz et al. [2004]. 4He gas
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concentrations ranged from 9x10-10 to 5.5x10-6 cc STP/g, and 2σ internal precision of the
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3
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relative to atmospheric (R/Ra) using an atmospheric 3He/4He ratio of 1.384 × 10-6. New
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He/4He measurements ranged from ±0.06 to ±0.52 Ra. 3He/4He ratios are reported
He/4He measurements on glasses reported in this study are shown in Table 2.
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1.3. Major element analyses
All major element analyses, with the exception of samples 127-05, 127-11, and
126-18, were measured on glasses by electron microprobe at the Hawaii Institute of
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Geophysics and the data are published previously [Sinton et al., 1985; Johnson and
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Sinton, 1990; Sinton et al., 1993]. Whole rock powders were prepared for samples 127-
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05 and 127-11 and measured by X-ray fluorescence on a ThermoARL XRF at
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Washington State University (WSU) and the data are published in Jackson et al. [2010].
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All major element data are summarized in Table 1.
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1.4. Trace element analyses
Trace element concentrations were previously measured by X-ray fluorescence
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for many of the samples examined in this study [Sinton et al., 1985; Johnson and Sinton,
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1990; Sinton et al., 1993]. New trace element analyses were performed by ICP-MS at the
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Washington State University GeoAnalytical Lab on a aliquots of the glass samples
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examined by Sinton et al. [1985], Johnson and Sinton [1990], Sinton et al. [1993], and
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Jackson et al. [2010] (Table 3). Measurements were made on glass chips (unleached, but
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sonicated in milliQ H2O). For one sample (4-1), glass was not available and unleached
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whole rock powder was prepared instead (sample 4-1 was crushed in W-carbide and,
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hence, the Ta data are compromised). As a check on the reproducibility of the trace
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element analyses, we included an analysis of a 200 mg aliquot of BHVO-2 powder with
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the batch of samples analyzed in this study, and the data are reported in Table 3.
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1.5. Comparisons of new isotopic data with previously published values
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We note that 13 of the glass samples with new isotopic data reported here were
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previous analyzed for Sr and Nd isotopes in the 1980’s at Lamont-Doherty Geological
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Observatory (LDGO) [Sinton et al., 1993] and at Massachusetts Institute of Technology
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(MIT) [Johnson and Sinton, 1990]. While all of the 143Nd/144Nd analyses agree within 60
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ppm, two 143Nd/144Nd analyses show larger disagreement: sample 5-15, measured at
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LDGO, is 107 ppm higher than our analysis, and sample 140-1A, measured at MIT, is
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131 ppm lower. The 87Sr/86Sr agreement between this study and the two previous studies
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is poorer. The 87Sr/86Sr analyses run 69 to 112 ppm higher than the MIT analyses. Five
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of the seven 87Sr/86Sr analyses at LDGO agree with our analyses within 90 ppm, but
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LDGO analyses of samples 5-14 and 6-54 ran 138 ppm and 439 ppm higher than the
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present study. The LDGO glasses were not acid leached prior to analysis (they were
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sonicated in distilled water), which may explain the elevated 87Sr/86Sr relative to the data
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reported here.
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However, we cannot easily explain the large offsets in 143Nd/144Nd between this
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data set and the two MIT and LDGO measurements, as analyses at MIT and LDGO also
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were made on glasses. Again, the lack of leaching may play an important role,
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particularly if secondary Nd-rich material, such as ferromanganese oxyhydroxides or
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phosphates, was present on the surface of the glass. We note that our measurements on
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unknowns are reproducible and our results on basaltic standards are consistent with
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measurements made in other modern laboratories (Supplementary Fig. 1 and
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Supplementary Table 1). One of the two glasses that shows a large discrepancy in Nd
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isotopic composition relative to the MIT analysis, sample 140-1A, was analyzed twice in
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our laboratory on two different aliquots of glass chips prepared several months apart; the
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aliquots were picked, leached, dissolved and processed through column chemistry
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separately and run during different analytical sessions on the Neptune MC-ICP-MS, and
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the 143Nd/144Nd measurements differ by only 50 ppm. Furthermore, multiple USGS rock
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standards measurements of 143Nd/144Nd (and 87Sr/86Sr) made in this study show excellent
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agreement with other labs (Supplementary Fig. 1).
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As a final note, we point out that radiogenic isotopes were measured on whole
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rock [Jackson et al., 2010] and glass (this study) aliquots for three samples from Wallis
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and Futuna Islands, 127-05, 127-11 and 6-52. Where 87Sr/86Sr and 143Nd/144Nd were
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measured on both glass and whole rock powder, there is excellent agreement. Lead
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isotopic measurements of whole rocks and glasses show poorer agreement. One
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explanation for this variance may be the variable affects that weathering has on the whole
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rock, for which sample freshness is more difficult to ascertain than for glass samples,
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which can be visually inspected for freshness. As demonstrated in Fig. 4, Futuna whole
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rocks exhibit evidence of having been compromised by weathering, while glasses are
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characterized by more pristine patterns. The whole rock and glass trace element analyses
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of sample 6-52, which exhibit significant differences in Pb isotope compositions, also
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show clear differences in spidergram shape. In particular, the Pb abundance in the glass
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is nearly three times lower than in the whole rock, suggesting Pb mobilization.
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Furthermore, it is not always apparent which portion of the rock is attacked by leaching
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prior to sample dissolution and analysis, particularly for Sr and Pb isotopic compositions
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in altered basalts [Nobre Silva et al., 2010]. Thus, we conclude that different weathering
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patterns in the whole rocks may make whole rock Pb more susceptible to being
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compromised relative to fresh glasses from the same sample.
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