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Auxiliary text for
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Geochemistry of volcanic glasses from the Louisville Seamount Trail (IODP
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Expedition 330): implications for eruption environments and mantle melting
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Alexander R.L. Nichols1#, Christoph Beier2, Philipp A. Brandl2, Stefan H. Krumm2
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Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa,
Institute for Research on Earth Evolution (IFREE), Japan Agency for Marine Earth
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237-0061 Japan
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Schlossgarten 5, 91054 Erlangen, Germany
GeoZentrum
Nordbayern,
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email: nichols@jamstec.go.jp
Friedrich-Alexander-Universität
Erlangen-Nürnberg,
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1. Drill Sites
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1.1 Canopus Guyot (Site U1372):
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Site U1372 is on the summit plain of the northern volcanic center of Canopus Guyot
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in a water depth of 1957.6 m. Hole U1372A reached 232.9 meters below sea floor
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(mbsf) and penetrated 187.3 m of igneous basement below 45.6 m of sediment cover
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[Koppers et al., 2012a]. The drilled igneous section can be broadly divided into a
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lower part (104 m thick) of aphyric to variably plagioclase and olivine phyric
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volcaniclastic breccias succeeded by aphyric to olivine phyric lava flows. Flows in the
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lower 28.7 m of the upper part of the succession have scoriaceous and oxidized tops,
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while those above have peperetic tops, implying subaerial to shallow marine
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conditions.
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1.2 Rigil Guyot (Site U1374):
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Site U1374 is near the western rift zone on Rigil Guyot in a water depth of 1559 m.
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Hole U1374A is the deepest hole drilled during IODP Expedition 330, reaching 522
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mbsf, of which 505.3 m is igneous basement. This consists largely of volcaniclastic
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breccia, with lava flows increasing in frequency towards the top [Koppers et al.,
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2012a]. This, together with peperitic tops and bottoms on some of the flow units and
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sedimentary intervals, suggests that this is an emerging sequence. Aphyric basalt
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sheets intrude the lower 185.9 m of the hole. Here the phenocryst assemblage is
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plagioclase-dominated, but olivine becomes more dominant in the upper 256.8 m.
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Clasts in the lower part of the volcaniclastic breccia have lobate and intricate margins
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suggesting in-situ cooling, whereas higher up the breccia is more blocky and includes
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pillow fragments that have broken quenched margins suggesting post-cooling re-
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deposition [Koppers et al., 2012a].
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1.3 Burton Guyot (Site U1376):
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Site U1376 is located between two small topographic highs on the eastern side of the
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summit of Burton Guyot. Drilling reached 182.8 mbsf, penetrating 140.9 m of igneous
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basement and 41.9 m of sediment cover that included volcanic sand and breccia that
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provides evidence for late-stage post-erosional volcanism [Koppers et al., 2012a]. The
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igneous basement consists of a lower 70.2 m of olivine phyric and aphyric
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volcaniclastic breccia intruded by sheets of aphyric basalt. The upper 17.35 m
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contains abundant glassy material. The top of the volcaniclastic breccia is cut by an
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erosion surface, above which is a 33 m thick massive olivine-augite flow. This is
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succeeded by further breccia and pillow lavas, suggesting that the basement section
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was emplaced in a submarine environment.
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1.4 Hadar Guyot (Site U1377):
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Site U1377 is located at the center of the Hadar’s summit plain. Hole U1377B
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reached 37.0 mbsf, of which 27.9 m was igneous basement. The lower 12.8 m of the
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igneous sequence consists of what were believed to be a stack of pillow lavas
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separated by thick well preserved glassy margins [Koppers et al., 2012a]. However,
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the margins include some curious ‘intrusive’ features where the glass connects to the
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more massive interior of the unit below. This was interpreted to be where still molten
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pillow interiors had broken out into space between overlying pillow bodies or where
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magma had injected into a stack of pillows [Koppers et al., 2012a].
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2. Analytical methods
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2.1 Major elements
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All major element analyses were carried out on fresh glass fragments that were
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handpicked to avoid any visible alteration. Major element data for each sample are the
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average of ten spots on a single glass chip, and were measured using a JEOL JXA-
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8200 Superprobe electron microprobe at the GeoZentrum Nordbayern, Universität
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Erlangen-Nürnberg. An acceleration voltage of 15 kV, a beam current of 15 nA, and a
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defocused beam (10 µm) were used. Counting times were 20 s for peaks and 10 s for
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backgrounds for SiO2, TiO2, Al2O3, FeO, MnO, MgO, CaO, K2O, Na2O, P2O5 and S,
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while for F and Cl counting times on the peaks and backgrounds were increased to 40
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and 20 s, respectively. The method used by Brandl et al. [2012] was followed except
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data were not normalized to glass standards VG-2 and VG-A99. Glass standards VG-
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2, VG-A99 and VG-568 were analyzed periodically as unknowns to ensure there was
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no spectrometer drift.
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2.2 Trace elements
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The trace elements were analyzed in-situ on the same glasses that had previously been
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analyzed for major elements using an UP193FX New Wave Research Laser operated
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on an Agilent 7500i ICP-MS at the GeoZentrum Nordbayern, Universität Erlangen-
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Nürnberg. An argon-helium mixture was used as carrier gas, 25µm spots were
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analyzed with a 20Hz repetition rate, 0.67 GW/cm2 irradiance and 3.4 J/cm2 fluence.
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Maximum peak measuring times were 10 msec for 7Li, 29Si, 55Mn; 25 m sec for 45Sc,
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Ce, 141Pr, 146Nd, 147Sm, 153Eu, 157Gd, 159Tb, 163Dy, 165Ho, 166Er, 169Tm, 172Yb, 175Lu,
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Hf,
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NIST SRM 612 was used [Pearce et al., 1997]. To ensure accuracy and
V, 53Cr, 59Co, 60Ni, 63Cu, 66Zn, 85Rb, 88Sr, 89Y, 90Zr, 93Nb, 118Sn, 133Cs, 137Ba, 139La,
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W,
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Re,
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Pb,
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Th,
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U; and 30 msec for
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Ta. For external calibration
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reproducibility NIST SRM 614 and BCR-2G were periodically analyzed (see
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auxiliary Table S2). Silica contents from the microprobe analyses were used as an
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internal standard.
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2.3 H2O and CO2 measurements
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Fifty-two of the 113 samples analyzed for major and trace elements were successfully
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analyzed for H2O and CO2 using micro-Fourier-transform infrared (FTIR)
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spectroscopy at the Institute for Research for Earth Evolution (IFREE), Japan Agency
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for Marine Earth Science and Technology (JAMSTEC). For 34 of these samples,
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glassy chips were prepared as wafers, analyzed by micro-FTIR spectroscopy, and then
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the same wafers were mounted and analyzed by EPMA and finally LA-ICP-MS (see
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Table S1). For the other 18 samples a glassy chip was broken off from the sample
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prepared for EPMA and LA-ICP-MS and prepared separately for micro-FTIR
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spectroscopy. In all cases chips were prepared for micro-FTIR spectroscopy by
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mounting in Orthocryl® and then grinding down one side with silica carbide paper
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until a large (at least 1 mm across) flat area was exposed. This was then polished
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using diamond suspension to 1 µm. After polishing, the sample, still within
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Orthocryl®, was mounted polished side down on a glass slide using Crystal Bond
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509. The Orthocryl® sample mount was then cut to a thickness of approximately 1
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mm using a Struers Discoplan-TS saw, before grinding to approximately 150 – 200
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µm thickness using silica carbide paper, and polishing the second surface, parallel to
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the first, to 1 µm using diamond suspension. The Crystal Bond 509 and Orthocryl®
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were then dissolved in acetone, leaving a free-standing wafer approximately 150 –
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200 µm in thickness with two parallel polished surfaces.
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These wafers were analyzed using a Varian FTS 7000 spectrometer and an attached
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UMA600 microscope. The spectra used to measure H2O and CO2 were collected
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conventionally in transmitted light at single spots 20  20 µm square, selected using
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the microscope, over 512 scans at a resolution of 8 cm-1 using a heated ceramic
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(globar) infra-red source and a Ge-coated KBr beamsplitter. The wafers were placed
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on a H2O-free IR-invisible KBr window. Background analyses were taken through the
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window, before the wafer of glass was positioned in the beam path to measure sample
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spectra. H2O concentrations were calculated using a modified Beer-Lambert law
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[Stolper, 1982], with the absorbance at ~3550 cm-1 used for total H2O and that at
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~1660 cm-1 for molecular H2O (H2Omol) and molar absorptivity coefficients of 63 ± 5
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and 25 ± 3 l/molcm, respectively [Dixon et al., 1988]. The absorbance was defined as
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the maximum height of the peaks above a linear baseline. The concentration of OH
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was obtained by subtracting the concentration of H2Omol from total H2O. The doublet
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at ~1515 and ~1435 cm-1, indicative of CO2 dissolved in basaltic glass [Fine and
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Stolper, 1985], was not detected in any of the Louisville glasses. Glass densities, for
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use in the Beer-Lambert law, were calculated from the oxide compositions of the
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glasses using the principles, partial molar volumes and volume changes with
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temperature from Lange and Carmichael [1987] and Lange [1997], including those
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for H2O from Ochs and Lange [1999]. Thickness for most analyses was obtained from
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interference fringes on FTIR spectra measured in reflected light on exactly the same
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spot as those measured in transmitted light following the procedures of Wysoczanski
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and Tani [2006] and Nichols and Wysoczanski [2007] and using a refractive index of
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1.546 for basalt [Kumagai and Kaneoka, 2003]. In some cases thicknesses were also
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measured directly with a digital displacement gauge and there is good agreement
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between the two methods. Where possible, thicknesses measured using interference
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fringes were preferred because these were measured in exactly the same spot as the
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spectra in transmitted light. Uncertainties in H2O species concentrations are estimated
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to be ±10 % [Wysoczanski and Tani, 2006], which is mostly due to the errors in the
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thickness and molar absorptivity coefficients. The minimum possible detectable peak
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on the FTIR spectra has an absorbance of 0.01 (ca. three times background), with the
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detection limits for each H2O and CO2 species dependent on the thickness at each
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analyzed spot.
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2.4 Oxygen isotope analyses
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Oxygen isotope (δ18O) values were analyzed by laser fluorination using a 25 W-
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Synrad CO2-laser and F2 as reagent at the GeoZentrum Nordbayern, Universität
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Erlangen-Nürnberg using the method described in detail by Haase et al. [2011] and
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Genske et al. [2013]. The oxygen isotopes were analyzed on a ThermoFisher Delta
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Plus mass spectrometer at the GeoZentrum Nordbayern. During each measurement
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day, four standard samples (UWG-2, NBS-30) were processed and measured together
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with the samples. The δ18O raw values of a run were corrected by the mean difference
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of the reference values from the standards (5.8 and 5.1‰, respectively). All oxygen
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isotope values are given in permil relative to V-SMOW. Reproducibility of the UW
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GMG 2 garnet standard obtained during the run of this study is 5.84 ± 0.07 ‰ (1sd, n
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= 29).
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3 Estimating subsidence
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In order to estimate the subsidence experienced by each sample, the collection depth
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(depth in drill hole plus water depth), corrected for sediment loading, is subtracted
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from the paleo-quenching depth derived from the volatile saturation pressures, after
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accounting for the change in sea level since the formation of the seamount to the
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present day. For each hole, sediment loading (ds) is calculated using the equation of
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Crough [1983]:
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d s = ts *
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where ts is the thickness of the overlying sediment (m) from Koppers et al., [2012a],
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m the density of the mantle (3,300 kgm-3), s the density of the sediment (estimated
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to be 1,900 kgm-3) and w the density of seawater (1,030 kgm-3). This is then
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subtracted from each sample depth to correct for sediment loading. Sea level at the
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time the seamounts were erupting is estimated using the curve of Miller et al. [2005],
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which shows that it has fallen ~44, ~43, ~43 and ~62 m since Canopus (74 Ma), Rigil
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(69.5 Ma), Burton (66 Ma) and Hadar (50 Ma) formed, respectively.
( r m - rs )
(r m - r w )
[1]
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Additional references:
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Crough, S. T. (1983), The Correction for Sediment Loading on the Seafloor, J.
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Geophys. Res., 88(B8), 6449-6454, doi: 10.1029/JB088iB08p06449.
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Dixon, J. E., E. Stolper, and J. R. Delaney (1988), Infrared spectroscopic
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measurements of CO2 and H2O in Juan de Fuca Ridge basaltic glasses, Earth Planet.
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Sci. Lett., 90, 87-104, doi:10.1016/0012-821X(88)90114-8.
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Fine, G., and E. Stolper (1985), Dissolved carbon dioxide in basaltic glasses:
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concentration and speciation, Earth Planet. Sci. Lett., 76, 263-278, doi:10.1016/0012-
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821X(86)90078-6.
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Genske, F. S., C. Beier, K. M. Haase, S. P. Turner, S. Krumm, and P. A. Brandl
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(2013), Oxygen isotopes in the Azores islands: crustal assimilation recorded in
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olivine, Geology, 41, 491-494, doi: 10.1130/G33911.1.
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Haase, K. M., S. Krumm, M. Regelous, and M. Joachimski (2011), Oxygen isotope
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evidence for the formation of silicic Kermadec island arc and Havre–Lau backarc
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magmas by fractional crystallisation, Earth Planet. Sci. Lett., 309, 348-355, doi:
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10.1016/j.epsl.2011.07.014.
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Kumagai, H., and I. Kaneoka (2003), Relationship between submarine MORB glass
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textures and atmospheric component of MORBs, Chem. Geol., 200, 1-24, doi:
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10.1016/S0009-2541(03)00077-9.
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Lange, R. A. (1997), A revised model for the density and thermal expansivity of K2O-
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Na2O-CaO-MgO-Al2O3-SiO2 liquids from 700 to 1900 K: extension to crustal
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magmatic
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10.1007/s004100050345.
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Lange, R. A., and I. S. E. Carmichael (1987), Densities of Na2O-K2O-CaO-MgO-
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FeO-Fe2O3-Al2O3-TiO2-SiO2 liquids: New measurements and derived partial molar
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properties,
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7037(87)90368-1.
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Miller, K. G., M. A. Kominz, J. V. Browning, J. D. Wright, G. S. Mountain, M. E.
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Katz, P. J. Sugarman, B. S. Cramer, N. Christie-Black, and S. F. Pekar (2005), The
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Phanerozoic Record of Global Sea-Level Change, Science, 310, 1293-1298, doi:
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10.1126/science.1116412.
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Nichols, A. R. L., and R. J. Wysoczanski (2007), Using micro-FTIR spectroscopy to
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measure volatile contents in small and unexposed inclusions hosted in olivine crystals,
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Chem. Geol., 242, 371-384, doi:10.1016/j.chemgeo.2007.04.007.
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Ochs, F. A., and R. A. Lange (1999), The density of hydrous magmatic liquids,
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Science, 283, 1314-1317, doi: 10.1126/science.283.5406.1314.
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Pearce, N. J. G., W. T. Perkins, J. A. Westgate, M. P. Gorton, S. E. Jackson, C. R.
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Neal, and S. P. Chenery (1997), A compilation of new and published major and trace
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element data for NIST SRM 610 and NIST SRM 612 glass reference materials,
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