Supplementary information
Analytical methods
Quenched glass from the surface of the submarine volcanic rock samples was
used for the chemical and isotope analyses except where it could not be obtained. Glass
fragments were hand-picked for the analyses, avoiding phenocrysts as much as possible.
The glass was crushed to <0.3 mm fractions after washing with pure water in an
ultrasonic bath. The sample fraction was then washed in H2O2 to decompose any
manganese oxide coating followed by a dilute HCl wash to decompose iron
oxyhydroxides. Finally, the glass sample fraction was washed with ultra pure water and
dried at 100°C. If enough glass could not be obtained, a bulk rock sample was used for
X-ray fluorescence photometry (XRF) analysis after treating in the same manner as
described above. Only XRF analysis was performed on bulk samples.
The major and minor elements were measured by XRF. The analytical
procedure followed that described in Kakubuchi et al. [1997] and Yamada et al. [1998].
The glass fragments were powdered with an agate mortar and pestle and dried at 115°C
for 3 hours, then stored in a desiccator. A mixture of 4:1 lithium metaborate and lithium
tetraborate for flux was heated at 450°C for 5 hours and lithium nitrate was dried at
115°C for 3 hours. Each of these was preserved in a desiccator prior to mixing with
the sample power. Samples were prepared as a mixture of 3.6 g flux, 1.8 g sample
powder, and 0.54 g lithium nitrate. that was placed in a platinum crucible. After adding
1-2 drops of lithium iodide, the mixture was heated at 1200°C for 520 seconds using a
Bead Sampler (Tokyo Rika Kikai, NT-2000), then quenched to make a glass bead for
the XRF analysis (RIGAKU RIX2100). Calibration lines for each element were drawn
using the analytical results of standard rock samples (Igneous rock series distributed by
the Geological Survey of Japan). The standards were prepared following the same
procedure as that of the samples. Errors of the analytical results for the major elements
are estimated to be <2-3%, minor elements with concentrations of more than one
hundred ppm have errors of <10% and REE elements <20%.
Water was extracted from the samples by thermal decrepitation in a vacuum
line. Glass fragments (0.15 g) were put in a quartz glass tube and capped with quartz
glass wool. Then, the absorbed water was removed via a vacuum line heated at 250°C
for 3 hours. The sample glass was fused with the quartz glass and volatiles thus
produced were introduced into a CuO furnace to oxidize the H2 gas into the water. After
removing impurities, the water obtained was reduced to H2 by reaction with U
[Bigeleisen et al., 1952]. The resulting volume of H2 was manometrically measured, and
hydrogen isotope ratios were determined by mass spectrometry (Micro Mass, SIRA 10).
The hydrogen isotope ratios are expressed using standard delta-notation and compared
to SMOW.
Chemical preparation of minor and trace elements using Inductively coupled
plasma mass spectrometer (ICP-MS) and mass spectrometric procedures are those of
Mahoney et al. [1991].
For the analysis of minor and trace elements including rare earth elements
(REE) using ICP-MS, 30 mg of glass fragments (sorted 0.1~0.3 mm fractions) were
washed with 1:3 HCl to remove the Mn and Fe coatings in a plastic vial, then, a mixture
of HNO3 and HF was added and heated on a hot plate to dried to a moist patch, fluorides
3.
Then, fluorides
were removed by heating with ~100 µL 8M HNO3 repeated 3 times, and finally the
resulting paste was diluted with 8 mL 1.5 M HNO3 to preserve as the stock solution.
The day before the analysis, 100 µL aliquots of the stock solution was diluted with 10
mL of an internal standard solution, in which ~900 ng B, In, Tl and Bi was dissolved in
5% HNO3 solution. These solutions were then measured using the ICP-MS (VG PQ-2S)
at University of Hawai‘i. Blanks of the internal standard solution were analyzed between
each sample and used to monitor and correct for drift. Calibration of the ICP-MS was
performed using rock standards AGV-1, BIR-1, BCR-1, and BHVO-1. Running standard
Hawaiian basalt K1919 was run after every five samples. Relative precision indicated by
repeat runs of K1919 are better than 5% for all elements except Co, Pb and Th, which
range from 5-7%.
Sr, Nd, and Pb isotopes were analyzed for selected glass samples. The
samples, separated as similar to those for ICP-MS analysis, were leached 5-8 min. in
0.15 M HF and HNO3 solutionwith mechanically agitating in an ultrasonic bath to
remove surface contaminants and any undetected alteration. Cleaned fragments of 200 –
300 mg were heated in capped Teflon® vials with concentrated 1:3 HF and HNO3 under
heat lump for overnight. The digested samples were dried and then heated with HNO3 to
dried up to eliminate fluoride precipitates, then finally diluted to ~8-10 mL 2 M HCl
solution, which was visually checked to ensure total dissolution. This solution was split
for Pb concentration determination by isotope dilution (ID) and the following Sr and Nd
isotope analysis and Pb isotope composition measurement (IC).
The obtained solution was treated using HBr-HNO3 ion exchange technique
to purify the targeted elements according to the method by Galer and O’Nions [1989],
which was modified for large sample sizes. Column washes after Pb ion-exchange
procedures were collected and purified for Sr and Nd analyses following standard
ion-exchange column methods [Mahoney et al., 1991; Mahoney and Spencer, 1991].
Then isotopes were analyzed using thermal ionization mass spectrometry (TIMS,
VG-Sector), which is used for large ion-beam radiogenic isotope analysis and
small-sample Nd (5 ng or less) isotopic analysis, at the University of Hawaii's, School
of Ocean and Earth Science and Technology (SOEST). The VG Sector is a 5 Faraday
instrument used for routine Pb, Sr, Nd (including small sample analysis at <5ng) and
double-spike Pb isotope analyses. Five-year reproducibility for NBS981 Pb using a
204
Pb-207Pb double-spike technique and multi-dynamic measurement is ~60 ppm for
206
Pb/204Pb,
207
Pb/204Pb, and
Pb/204Pb [e.g., Ingle et al., 2010]. Nd and Sr TIMS
208
measurements were internally corrected for fractionation using
148
NdO/144NdO =
0.242436, corresponding to 148Nd/144Nd = 0.241572 and 86Sr/88Sr = 0.1194. Nd and Sr
respectively. Total
measured range for La Jolla Nd standard is 0.000012 (± 0.2 εNd units) and for NBS
987 Sr is 0.000022. Within-run errors on individual sample measurements are less than
or equal to the above external uncertainties on La Jolla, NBS 987 and NBS 981
standards. Data are reported relative to
143
Nd/144Nd = 0.511855 for La Jolla Nd and
87
Sr/86Sr = 0.71024 for NBS 987 Sr. See Frey et al. [2000] for details of isotopic
fractionation corrections, and standards measurements. Total procedural blanks were
<20 pg for Nd, <100 pg for Sr, and <40 pg for Pb. Uncertainty for Pb ID are <0.8%.
Total procedural blanks are typically <50 pg for Pb, <80 pg for Sr, and <10 pg for Nd;
all blanks are negligible. Present day εNd = 0 corresponds to 143Nd/144Nd = 0.51264.
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