Overview

This dataset contains the age and geochemical data supporting the study of Aleutian Arc initiation at 56 Ma. The following files are provided:

• LA-ICP-MS_ages_summary.csv — Summary age data of the samples
• LA-ICP-MS_metadata.csv — Metadata of the LA-ICP-MS analyses
• LA-ICP-MS_Trace_element_data.csv — LA-ICP-MS trace element concentration data
• LA-ICP-MS_U_Pb_isotopic_data.csv — LA-ICP-MS isotopic and age data
• 40Ar39Ar_Step_Data.csv — Flattened 40Ar/39Ar step-heating data
• 40Ar39Ar_Summary_Data.csv — Summary plateau, integrated, isochron, trapped-Ar, and K/Ca results
• Whole_Rock_Major_Trace_Element_Data.csv — Summary of major and trace element composition of bulk-rock samples analyzed by XRF and ICP-MS
• Whole_Rock_ICPMS_Quality_Control.csv — Summary of quality control of ICP-MS trace element analysis by reference material and blanks
• Whole_Rock_Sr-Nd-Pb_Isotope_Data.csv — Summary of radiogenic Sr, Nd and Pb isotope composition of bulk-rock samples

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File descriptions

U-Pb Zircon Age Data

LA-ICP-MS_ages_summary.csv

• Sample — currently valid sample name
• Age — weighted mean age of repeated analyses
• uncert int. — uncertainty as 2 standard error, internal only
• Uncert total — total uncertainty, including systematic uncertainty, as 2 SE

LA-ICP-MS_metadata.csv

Parameters used for LA-ICP-MS analyses, reported based on a template available for download at www.Plasmage.org.

LA-ICP-MS_U_Pb_isotopic_data.csv

• Sample name — sample name and analysis number
• Analysis date — date of the analysis
• comment new — comment if something was observed during data reduction
• Duration (s) — duration of the integration
• Spot Size (µm) — spot size of the laser beam
• Final Pb206/U238_mean — mean final corrected ²⁰⁶Pb/²³⁸U isotopic ratio
• Final Pb206/U238_2SE(prop) — 2 standard error uncertainty with a propagated part from primary reference material for the ²⁰⁶Pb/²³⁸U isotopic ratio
• Final Pb206/U238 age_mean — mean final corrected ²⁰⁶Pb/²³⁸U age in Ma
• Final Pb206/U238 age_2SE(prop) — 2 standard error uncertainty with a propagated part from primary reference material for the ²⁰⁶Pb/²³⁸U age in Ma
• Final Pb207/U235_mean — mean final corrected ²⁰⁷Pb/²³⁵U isotopic ratio
• Final Pb207/U235_2SE(prop) — 2 standard error uncertainty with a propagated part from primary reference material for the ²⁰⁷Pb/²³⁵U isotopic ratio
• Final Pb207/U235 age_mean — mean final corrected ²⁰⁷Pb/²³⁵U age in Ma
• Final Pb207/U235 age_2SE(prop) — 2 standard error uncertainty with a propagated part from primary reference material for the ²⁰⁷Pb/²³⁵U age in Ma
• Final Pb208/Th232_mean — mean final corrected ²⁰⁸Pb/²³²Th isotopic ratio
• Final Pb208/Th232_2SE(prop) — 2 standard error uncertainty with a propagated part from primary reference material for the ²⁰⁸Pb/²³²Th isotopic ratio
• Final Pb208/Th232 age_mean — mean final corrected ²⁰⁸Pb/²³²Th age in Ma
• Final Pb208/Th232 age_2SE(prop) — 2 standard error uncertainty with a propagated part from primary reference material for the ²⁰⁸Pb/²³²Th age in Ma
• Final Pb207/Pb206_mean — mean final corrected ²⁰⁷Pb/²⁰⁶Pb isotopic ratio
• Final Pb207/Pb206_2SE(prop) — 2 standard error uncertainty with a propagated part from primary reference material for the ²⁰⁷Pb/²⁰⁶Pb isotopic ratio
• Final Pb207/Pb206 age_mean — mean final corrected ²⁰⁷Pb/²⁰⁶Pb age in Ma
• Final Pb207/Pb206 age_2SE(prop) — 2 standard error uncertainty with a propagated part from primary reference material for the ²⁰⁷Pb/²⁰⁶Pb age in Ma
• Final U238/Pb206_mean — mean final corrected ²³⁸U/²⁰⁶Pb isotopic ratio
• Final U238/Pb206_2SE(prop) — 2 standard error uncertainty with a propagated part from primary reference material for the ²³⁸U/²⁰⁶Pb isotopic ratio
• Final U/Th_mean — U/Th concentration ratio
• rho 206Pb/238U v 207Pb/235U — error correlation between isotopic ratios ²⁰⁶Pb/²³⁸U and ²⁰⁷Pb/²³⁵U
• rho 207Pb/206Pb v 238U/206Pb — error correlation between isotopic ratios ²⁰⁷Pb/²⁰⁶Pb and ²³⁸U/²⁰⁶Pb

LA-ICP-MS_Trace_element_data.csv

• Sample name — sample name and analysis number
• Analysis date — date and time of analysis
• Duration (s) — duration of the integration
• InternalStandard_Si_mean — internal standard concentration used to correct for differences in ablation rate between reference material and sample

For each element listed below, three columns are provided:

• {El}_ppm_mean — concentration in micrograms per gram (ppm)
• {El}_ppm_2SE(int) — 2 standard error (internal) uncertainty of the concentration
• {El}_ppm_LOD_Pettke — limit of detection of the concentration

Elements reported (mass indicated by isotope):

Al27, P31, Ti49, Y89, Zr91, Nb93, Ba137, La139, Ce140, Pr141, Nd146, Sm147, Eu153, Gd157, Tb159, Dy163, Ho165, Er166, Tm169, Yb172, Lu175, Hf178, Ta181, Th232, U238.

Description of zircon U-Pb dating

In-situ zircon U-Pb isotopes were measured using a Thermo Element XR SF-ICP-MS coupled with a Resonetics Resolution 155 laser-ablation system at ETH Zürich. We used a 19 μm spot size, 4 Hz repetition rate, 2.0 J/cm² energy density (fluence), and 30 s ablation time after five cleaning pulses and 30 s of gas-blank acquisition.

For U-Pb dating, GJ-1 reference zircon (Jackson et al., 2004; Horstwood et al., 2016) was used as a primary reference material, while zircons 91500, Plešovice, AUSZ7-1, AUSZ7-5, GHR-1 and Rak-17 were measured as validation reference materials (Wiedenbeck et al., 1995; Sláma et al., 2008; Kennedy et al., 2014; von Quadt, 2016; Eddy et al., 2019; Webb et al., 2021, respectively). The average precision of these reference materials (RMs) ranged from 2.0% to 10.5% (2 SE), while the average precision of the samples is 3.8%.

Data reduction of in-situ dating by LA-ICP-MS was carried out using IOLITE 4 (Paton et al., 2011) combined with VizualAge (Petrus & Kamber, 2012). The in-situ dates were not corrected for common Pb; however, during data reduction, integration intervals were set to exclude the common-Pb-contaminated signal intervals, and data were filtered according to their discordance [(²⁰⁷Pb/²³⁵U age − ²⁰⁶Pb/²³⁸U age) / ²⁰⁷Pb/²³⁵U age] < 10%. For final ages, a systematic uncertainty of 1.5% was propagated quadratically, including uncertainties from the uncorrected possible common-Pb contribution, the uncertainty on the age of the primary RM, and the uncertainty of the applied corrections (downhole fractionation, drift). Th disequilibrium was not corrected, as the usual correction is well within the overall uncertainty.

References (U-Pb zircon dating)

• Jackson, S. E., Pearson, N. J., Griffin, W. L. & Belousova, E. A. (2004). The application of laser ablation-inductively coupled plasma-mass spectrometry to in situ U–Pb zircon geochronology. Chemical Geology 211, 47–69.
• Horstwood, M. S. A. et al. (2016). Community-derived standards for LA-ICP-MS U-(Th-)Pb geochronology — uncertainty propagation, age interpretation and data reporting. Geostandards and Geoanalytical Research 40, 311–332.
• Wiedenbeck, M. et al. (1995). Three natural zircon standards for U-Th-Pb, Lu-Hf, trace element and REE analyses. Geostandards Newsletter 19, 1–23.
• Sláma, J. et al. (2008). Plešovice zircon — a new natural reference material for U–Pb and Hf isotopic microanalysis. Chemical Geology 249, 1–35.
• Kennedy, A. K., Wotzlaw, J.-F., Schaltegger, U., Crowley, J. L. & Schmitz, M. (2014). Eocene zircon reference material for microanalysis of U-Th-Pb isotopes and trace elements. Canadian Mineralogist 52, 409–421.
• von Quadt, A. (2016). High-precision zircon U/Pb geochronology by ID-TIMS using new 10¹³ ohm resistors. Journal of Analytical Atomic Spectrometry 31, 658–665.
• Eddy, M. P. et al. (2019). GHR 1 zircon — a new Eocene natural reference material for microbeam U-Pb geochronology and Hf isotopic analysis of zircon. Geostandards and Geoanalytical Research 43, 113–132.
• Webb, P., Wiedenbeck, M. & Glodny, J. (2021). Survey questions and responses to the G-Chron 2019 proficiency test. GFZ Data Services, Potsdam.
• Paton, C., Hellstrom, J., Paul, B., Woodhead, J. & Hergt, J. (2011). Iolite: free software for the visualisation and processing of mass-spectrometric data. Journal of Analytical Atomic Spectrometry 26, 2508–2518.
• Petrus, J. A. & Kamber, B. S. (2012). VizualAge: a novel approach to laser ablation ICP-MS U-Pb geochronology data reduction. Geostandards and Geoanalytical Research 36, 247–270.

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Ar/Ar Age Data

40Ar39Ar_Step_Data.csv and 40Ar39Ar_Summary_Data.csv

• Corrected1 — isotopic intensities corrected for blank, baseline, radioactive decay and detector intercalibration, but not for interfering reactions.
• X — symbol preceding a sample ID denotes analyses excluded from plateau-age calculations.

Notes

• Errors quoted for individual analyses include analytical error only, without interfering-reaction or J uncertainties.
• Integrated age calculated by summing isotopic measurements of all steps.
• Plateau-age error is the inverse-variance-weighted mean error (Taylor, 1982) times √MSWD where MSWD > 1.
• Decay constants and isotopic abundances after Min et al. (2000).
• Ages calculated relative to 28.201 Ma FC-2 Fish Canyon Tuff sanidine standard (Kuiper et al., 2008).

Description of Ar-Ar dating methods

Groundmass (180–250 μm) was ultrasonically leached in 3 M HCl for ten minutes, rinsed repeatedly with deionized water, and then hand-picked under a binocular microscope. Plagioclase was subjected to additional leaching in 10% HF for five minutes. The purified separates were irradiated in the cadmium-lined in-core tube at the Oregon State University reactor. The 28.201 Ma Fish Canyon sanidine (Kuiper et al., 2008) was used as a neutron-fluence monitor for the irradiations containing these samples.

⁴⁰Ar/³⁹Ar analyses were conducted in the WiscAr Laboratory at the University of Wisconsin-Madison. Groundmass aliquots (~2–7 mg) were placed in a 2 mm diameter well in a copper tray and incrementally heated with a 55 W CO₂ laser. Gas released during each heating step was cleaned with two SAES GP50 getters (50 W / 400 °C) and an ARS cryotrap (at −125 °C). Isotopic analyses were done using a Nu Instruments Noblesse five-collector mass spectrometer (Jicha et al., 2016). Plagioclase from sample SO249-DR51-6 was analyzed using an Isotopx NGX-600 mass spectrometer (Mixon et al., 2022).

All ⁴⁰Ar/³⁹Ar ages are calculated using the decay constants of Min et al. (2000) and are reported with 2σ analytical uncertainties, including the J uncertainty (Table 2; Supplementary Table 2; Fig. 2).

References (Ar/Ar dating)

• Kuiper, K. F. et al. (2008). Synchronizing rock clocks of Earth history. Science 320, 500–504.
• Min, K., Mundil, R., Renne, P. R. & Ludwig, K. R. (2000). A test for systematic errors in ⁴⁰Ar/³⁹Ar geochronology through comparison with U/Pb analysis of a 1.1-Ga rhyolite. Geochimica et Cosmochimica Acta 64, 73–98.
• Jicha, B. R., Singer, B. S. & Sobol, P. (2016). Re-evaluation of the ages of ⁴⁰Ar/³⁹Ar sanidine standards and supereruptions in the western US using a Noblesse multi-collector mass spectrometer. Chemical Geology 431, 54–66.
• Mixon, E. E., Jicha, B. R., Tootell, D. & Singer, B. S. (2022). Optimizing ⁴⁰Ar/³⁹Ar analyses using an Isotopx NGX-600 mass spectrometer. Chemical Geology 593, 120753.

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Whole-Rock Geochemical Data

Whole_Rock_Major_Trace_Element_Data.csv

• Sample ID — currently valid sample name
• Rock Type — based on shipboard observations
• Latitude — decimal degrees, by GPS
• Longitude — decimal degrees, by GPS
• g/100g — concentration in grams per 100 grams, i.e. weight percent (wt%)
• µg/g — concentration in micrograms per gram, i.e. parts per million (ppm)
• n/p — not provided
• n/a — not applicable
• § — regular HF-HNO₃-HCl digestion followed by Parr-bomb pressure digestion in HNO₃-HF
• §§ — LA-ICP-MS on nano-particulate pressed powders
• *** — due to U uptake and possible Pb loss during seafloor alteration, parent/daughter ratios for samples with μ > 37 were calculated assuming U = Nb/47 and Pb = Ce/25 after Hofmann et al. (1986)

Whole_Rock_ICPMS_Quality_Control.csv

• Sample — name of reference material and procedural blank used during sample preparation
• Method — solution ICP-MS after Garbe-Schönberg (1993); laser ICP-MS after Garbe-Schönberg and Müller (2014)
• Material — regular digest of sample powders after Garbe-Schönberg (1993); Parr-Bomb = pressure digest using Parr-bomb vessels; glass pellets used for LA-ICP-MS analysis
• Analysis No. — overall analysis number of the ICP-MS lab at IfG, Kiel University
• n/p — not provided
• n/a — not analyzed
• µg/g — concentration in micrograms per gram (ppm)

Whole_Rock_Sr-Nd-Pb_Isotope_Data.csv

• Sample ID — currently valid sample name
• Rock Type — based on shipboard observations
• Latitude — decimal degrees, by GPS
• Longitude — decimal degrees, by GPS
• 2SE — twofold standard error of analysis
• TIMS — thermal ionization mass spectrometry
• (t) — initial isotope composition at time (t) of formation
• ° — Rb, Sr, Sm, Nd, U, Th and Pb concentrations from Jicha et al. (2006) used to calculate initial isotope ratios
• *** — due to U uptake and possible Pb loss during seafloor alteration, parent/daughter ratios for samples "SO249 DR51-6" and "SO249 DR51-9" with μ > 37 were calculated assuming U = Nb/47 and Pb = Ce/25 after Hofmann et al. (1986)
• # — chips leached in 2 M HCl at 70 °C for 2 hours prior to digestion
• ## — powder leached in 6 M HCl at 130 °C for 3 hours prior to digestion
• ### — least radiogenic ⁸⁷Sr/⁸⁶Sr of # and ## determinations
• n/a — not analyzed

Description of whole-rock analytical methods

A detailed description of analytical procedures for rock preparation, major- and trace-element concentration analysis and radiogenic Sr-Nd-Pb isotope ratio analysis can be found open-access in Hauff et al. (2021), and is summarized for the data set presented here as follows.

Major elements were determined on a PanAnalytical MagixPro PW2540 X-ray fluorescence spectrometer at the Institute of Mineralogy and Petrography, University of Hamburg, Germany. Reference materials (RMs) JGb-1, JB-2, JB-3, JA-3 and JG-3 were measured as unknowns alongside the samples, and results can be found in Bezard et al. (2021). The major elements lie mostly within 3% of the Govindaraju (1994) reference values.

Trace elements. High-precision trace-element compositions were determined by ICP-MS. With the exception of zircon-bearing rocks, samples were decomposed on a hotplate in HF-HNO₃-HCl-HClO₄ and analyzed in solution by ICP-MS on an Agilent 7500cs at the Institute of Geosciences, Christian-Albrechts-Universität zu Kiel, following the method of Garbe-Schönberg (1993). For zircon-bearing rocks, trace-element concentrations were obtained two ways:

(a) As described in Garbe-Schönberg (1993), except that sample decomposition was done in two steps — starting with HF-HNO₃-HCl digestion on the hotplate, followed by a second digestion step using HNO₃-HF in Parr-bomb vessels (sample SO249 DR40-1); or
(b) By LA-ICP-MS measurement of nano-particulate pressed-powder tablets, using a 193 nm excimer laser-ablation system (GeoLas Pro; Coherent) coupled to an Agilent 7900 ICP-MS, as described in Garbe-Schönberg and Müller (2014). Reported concentrations are the average of 3 spots (samples SO249 DR40-2 and DR40-2xen).

For each batch of samples, replicate analyses gave a relative standard deviation of typically less than 3% for all elements reported. BHVO-2 and BIR-1 were measured in every batch of samples measured in solution, and BHVO-2G and KL2-G were measured during LA-ICP-MS analyses of nano-particulate pressed powders. Differences between our measured standards and the GeoReM preferred values (georem.mpch-mainz.gwdg.de) are typically less than 5% for all elements.

Radiogenic isotopes. Sr, Nd and Pb isotope ratios were determined by thermal ionization mass spectrometry (TIMS) at GEOMAR. Prior to dissolution, sample chips were leached in 2 M HCl at 70 °C for one hour and thereafter triple-rinsed in 18 MΩ H₂O. NBS987 (Sr) and La Jolla (Nd) were measured 4–5 times per wheel, and the average ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd values were used to obtain a factor to normalize the measured data to the reference values. Sample data are reported relative to ⁸⁷Sr/⁸⁶Sr = 0.710250 ± 0.000008 (2SD, n = 181) and ¹⁴³Nd/¹⁴⁴Nd = 0.511850 ± 0.000006 (2SD, n = 581). Within-run mass-bias correction uses ⁸⁶Sr/⁸⁸Sr = 0.1194 and ¹⁴⁶Nd/¹⁴⁴Nd = 0.7219.

Pb isotope ratios were determined by Pb double-spike (DS) after Hoernle et al. (2011). NBS981-DS values are:

• ²⁰⁶Pb/²⁰⁴Pb = 16.9408 ± 0.0019
• ²⁰⁷Pb/²⁰⁴Pb = 15.4975 ± 0.0019
• ²⁰⁸Pb/²⁰⁴Pb = 36.7206 ± 0.0050
• ²⁰⁷Pb/²⁰⁶Pb = 0.914801 ± 0.000048
• ²⁰⁸Pb/²⁰⁶Pb = 2.167858 ± 0.000097

(2SD, n = 205)

BCR-2 was processed in the same way as the samples; long-term Sr-Nd-Pb isotope values are available at geomar.de/en/research/fb4/fb4-muhs/infrastructure/tims. Total procedural blanks were typically <30 pg Pb, <100 pg Sr and <50 pg Nd.

References (whole-rock methods)

• Bezard, R., Hoernle, K., Pfänder, J. A., Jicha, B., Werner, R., Hauff, F., Portnyagin, M., Sperner, B., Yogodzinski, G. M. & Turner, S. (2021). ⁴⁰Ar/³⁹Ar ages and bulk-rock chemistry of the lower submarine units of the central and western Aleutian Arc. Lithos 392–393, 106147. https://doi.org/10.1016/j.lithos.2021.106147
• Garbe-Schönberg, C.-D. (1993). Simultaneous determination of thirty-seven trace elements in twenty-eight international rock standards by ICP-MS. Geostandards Newsletter 17, 81–97. https://doi.org/10.1111/j.1751-908X.1993.tb00122.x
• Garbe-Schönberg, D. & Müller, S. (2014). Nano-particulate pressed powder tablets for LA-ICP-MS. Journal of Analytical Atomic Spectrometry 29(6), 990–1000. https://doi.org/10.1039/C4JA00007B
• Govindaraju, K. (1994). Compilation of working values and sample description for 383 geostandards. Geostandards and Geoanalytical Research 18, 1–158. https://doi.org/10.1046/j.1365-2494.1998.53202081.x-i1
• Hauff, F., Hoernle, K., Gill, J., Werner, R., Timm, C., Garbe-Schönberg, D., Gutjahr, M. & Jung, S. (2021). R/V Sonne Cruise SO255 "VITIAZ": an integrated major-element, trace-element and Sr-Nd-Pb-Hf isotope data set of volcanic rocks from the Colville and Kermadec Ridges, the Quaternary Kermadec volcanic front and the Havre Trough backarc basin, Version 1.0. Interdisciplinary Earth Data Alliance (IEDA). https://doi.org/10.26022/IEDA/111723
• Hoernle, K., Hauff, F., Kokfelt, T. F., Haase, K., Garbe-Schönberg, C.-D. & Werner, R. (2011). On- and off-axis chemical heterogeneities along the South Atlantic Mid-Ocean Ridge (5–11°S): shallow or deep recycling of ocean crust and/or intraplate volcanism? Earth and Planetary Science Letters 306, 86–97. https://doi.org/10.1016/j.epsl.2011.03.032
• Hofmann, A. W., Jochum, K. P., Seufert, M. & White, W. M. (1986). Nb and Pb in oceanic basalts: new constraints on mantle evolution. Earth and Planetary Science Letters 79, 33–45. https://doi.org/10.1016/0012-821X(86)90038-5
• Jicha, B. R., Scholl, D. W., Singer, B. S., Yogodzinski, G. M. & Kay, S. M. (2006). Revised age of Aleutian Island Arc formation implies high rate of magma production. Geology 34(8), 661–664. https://doi.org/10.1130/G22433.1