This README.txt file was generated on 06 May 2025 by Pamela Kempton ------------------- GENERAL INFORMATION ------------------- Title of Dataset: Temporal variations of the oldest Emperor-Hawaiian plume signature influenced by interaction with shallow mantle features Data associated with Kempton et al. (2025) Temporal variations of the oldest Emperor-Hawaiian plume signature influenced by interaction with shallow mantle features. Geochemistry, Geophysics, Geosystems [Paper #2025GC012208] ------------------- ABSTRACT ------------------- Hawaiian volcanoes < ~7 Ma are believed to be sourced from two different portions of the deep mantle: Loa-trend volcanoes originate from within the Pacific Large Low Shear Velocity Province (LLSVP), whereas Kea-trend volcanoes tap ambient mantle adjacent to the LLSVP. To assess whether the Emperor-Hawaiian plume maintained this association throughout its history, we present new geochemical data (trace elements, Sr-Nd-Pb-Hf isotopes) and geodynamical modelling for Emperor Seamounts ranging from > 81 Ma (Meijii and Detroit Seamounts) to ~50 Ma (Kōko Seamount). We show that Emperor seamounts differ from younger Hawaiian Islands in the abundance of isotopically depleted components. In Hf-Nd isotope space, Detroit lavas trend toward a high Hf component similar to that observed in other mantle plumes (e.g., Iceland, Galapagos). This component originated deep within the mantle, possibly as a sheath surrounding the plume stem. Sampling of this component was facilitated by Detroit being ridge-proximal when it formed (~81 – 76 Ma). Emperor seamounts younger than Suiko (~68 Ma) were intraplate and located beneath progressively older, thicker lithosphere. Backtracked locations of Emperor seamounts lie up to 15o latitude north of the Pacific LLSVP. This suggests the ancestral Emperor-Hawaiian plume was either (i) not initially associated with the Pacific LLSVP. (ii) was deflected northward by shallow mantle features such that plume-ridge interactions dominated in the upper mantle or convective flow patterns modified the plume structure in the mid mantle, or (iii) the edge of the Pacific LLSVP receded southward by more than 15° over the past ~100 m.y. ------------------- AUTHOR INFORMATION ------------------- Author Information First Author Contact Information Name: Pamela Kempton Institution: Department of Geology, Kansas State University, Address: Manhattan, KS 66506 USA Email: pkempton@ksu.edu Corresponding Author Contact Information Name: Pamela Kempton Institution: Department of Geology, Kansas State University, Address: Manhattan, KS 66506 USA Email: pkempton@ksu.edu Phone: 785-532-6724 Author Contact Information Name: C. Adam Institution: Department of Geology, Kansas State University, Address: Manhattan, KS 66506 USA Email: cadam@ksu.edu Author Contact Information Name: A. D. Saunders Institution: School of Geography, Geology and the Environment, University of Leicester Address: University Road, Leicester LE1 7RH, UK Email: ads@leicester.ac.uk Author Contact Information Name: T. L. Barry Institution: School of Geography, Geology and the Environment, University of Leicester Address: University Road, Leicester LE1 7RH, UK Email: tlb2@leicester.ac.uk --------------------- DATA & FILE OVERVIEW --------------------- # # Directory of Files in Dataset: List and define the different # files included in the dataset. This serves as its table of # contents. # Directory of Files A. Filename: #2025GC012208_Table_S1_Major_and_Trace_Element_Data_EH_Basalts.xlsx Alternate formats: #2025GC012208_Table_S1_Major_and_Trace_Element_Data_EH_Basalts.csv #2025GC012208_Table_S1_Major_and_Trace_Element_Data_EH_Basalts.pdf Short description: major and trace element concentration data for basalts from the Emperor-Hawaiian hotspot track provided in original Excel format plus alternative csv and pdf formats B. Filename: #2025GC012208_Table_S2_Sr-Nd-Pb-Hf_Isotope_Data_EH_Basalts.xlsx Alternate formats: #2025GC012208_Table_S2_Sr-Nd-Pb-Hf_Isotope_Data_EH_Basalts.csv #2025GC012208_Table_S2_Sr-Nd-Pb-Hf_Isotope_Data_EH_Basalts.pdf Short description: Sr-, Nd-, Pb-, and Hf-isotope data for basalts from the Emperor-Hawaiian hotspot track provided in original Excel format plus alternative csv and pdf formats File Naming Convention (if not included above): file names include (i) a 12-digit identifier (i.e., 2025GC012208) supplied by the journal publishing the paper (Geochemistry, Geophysics, Geosystems); (ii) a table reference number S1 and S2, where S refers to supplementary; (iii) and a brief description of the data in the file. # # Data Description: A data description, dictionary, or codebook # defines the variables and abbreviations used in a dataset. This # information can be included in the README file, in a separate # file, or as part of the data file. If it is in a separate file # or in the data file, explain where this information is located # and ensure that it is accessible without specialized software. # (We recommend using plain text files or tabular plain text CSV # files exported from spreadsheet software.) # ----------------------------------------- DATA DESCRIPTION FOR: #2025GC012208_Table_S1_Major_and_Trace_Element_Data_EH_Basalts.xlsx Alternate formats: #2025GC012208_Table_S1_Major_and_Trace_Element_Data_EH_Basalts.csv #2025GC012208_Table_S1_Major_and_Trace_Element_Data_EH_Basalts.pdf ----------------------------------------- The Excel workbook file consists of one spreadsheet: 1. Variables: SiO2, TiO2, Al2O3, Fe2O3, MnO, MgO, CaO, Na2O, K2O, Nb(X), Zr(X), Y(X), Sr(X), Rb(X), Ba(X), Cu(X), Ni(X), Co(X), Cr(X), Sc(X), V(X), Zr, Nb, Y, Ta, Hf, Sr, Rb, Ba, La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Pr, Ho, Er, Yb, Lu, Cs, U, Th, Pb, Cr, Ni, Cu, Zn, Co, Sc, V, Mo, Sn 2. Number of cases/columns: 83 samples. Sample naming convention follows the protocol established by the International Ocean Discovery Program (IODP); see https://www.iodp.org/ for details. 3. Missing data codes: N/A 4. Variable List: All variables are chemical elements or oxides and require no definition. Major element concentrations (SiO2, TiO2, Al2O3, FeO, MgO, MnO, CaO, Na2O, K2O) are in wt %. Trace element concentrations (Zr, Nb, Y, Ta, Hf, Sr, Rb, Ba, La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Pr, Ho, Er, Yb, Lu, Cs, U, Th, Pb, Cr, Ni, Cu, Zn, Co, Sc, V, Mo, Sn) are in ppm. Trace elements followed by “(X)” were analyzed by X-Ray Fluorescence (XRF); all other trace elements analyzed from Inductively Coupled Plasma Mass Spectrometry (ICP-MS). ----------------------------------------- DATA DESCRIPTION FOR: #2025GC012208_Table_S2_Sr-Nd-Pb-Hf_Isotope_Data_EH_Basalts.xlsx Alternate formats: #2025GC012208_Table_S2_Sr-Nd-Pb-Hf_Isotope_Data_EH_Basalts.csv #2025GC012208_Table_S2_Sr-Nd-Pb-Hf_Isotope_Data_EH_Basalts.pdf ----------------------------------------- The Excel workbook file consists of 1 spreadsheet 1. Variables: Age, Rb, Sr, 87Sr/86Sr measured, 87Sr/86Sr initial, Sm, Nd, 143Nd/144Nd measured, epsilon Nd, Pb, U, Th, 206Pb/204Pb measured, 207Pb/204Pb measured, 208Pb/204Pb measured, 206Pb/204Pb initial, 207Pb/204Pb initial, 208Pb/204Pb initial, 208Pb*/206Pb*, Lu, Hf, 176H/177Hf measured, epsilon Hf 2. Number of cases / rows: 43 separate analyses / samples 3. Missing data codes: N/A 4. Variable List: variables include Age (in millions of years, Ma), trace element concentrations (Rb, Sr, Sm, Nd, U, Th, Pb, Lu, Hf) in ppm, and standard associated isotopic ratios for the Sr-, Nd-, Pb- and Hf- isotope systems. Isotope ratios listed as ‘measured’ have been corrected for run-time fractionation and reported relative to accepted standard values for each isotope system. Ratios listed as ‘initial’, have been age corrected to the age reported for that sample. ----------------------------------------- ANALYTICAL METHODS ----------------------------------------- Samples were prepared for geochemical analysis at the University of Leicester. Weathered surfaces were removed using a hand splitter and the remainder split into 3 cm3 chips. The chips were reduced to small gravel-sized fragments in a flypress. Powders for major and trace element analysis were produced in an Agate Tema swingmill; a tungsten carbide swingmill was used for samples selected for isotopic analysis. Hf, Nd, Pb, and Sr isotope ratios were determined at the NERC Isotope Geosciences Laboratory (NIGL; now the National Environmental Isotope Facility, UK); the data are presented in Supplementary Information, Table S1. Procedures used in the analysis of Sr, Pb, Nd and Hf isotopes are given in Royse et al. (1998), Kempton et al. (2001), and Kempton & McGill (2002). Whole rock powders were leached for 1 hour in hot (~100oC) 6N HCL prior to Pb, Sr, and Nd isotope analysis. Leaching has negligible effect on the hafnium isotope systems (Thompson et al., 2008), so Hf analyses were completed on unleached whole rock powders. Sr and Nd were run as the metal species on single Ta filaments and double Re-Ta filaments, respectively, using a Finnigan MAT 262 multicollector mass spectrometer. Sr was run in multi-dynamic model; Nd was run in static mode. The effects of fractionation during runs were eliminated by normalizing 87Sr/86Sr to 86Sr/88Sr value of 0.1194 and 143Nd/144Nd to 146Nd/144Nd value of 0.7219. Sr and Nd isotope values are reported relative to accepted values for NBS 987 of 0.71024 and La Jolla of 0.51186, respectively. Minimum uncertainty is derived from external precision of standard measurements, which over the course of analysis are better than 25 ppm (2s) for both 87Sr/86Sr and 143Nd/144Nd. Blanks were < 250 pg for Sr and <90 pg for Nd. Pb isotopes were analysed on a VG MC-ICPMS, with mass fractionation during the run corrected for using the Tl-doping method. We used a 205Tl/203Tl value of 2.388, which was determined empirically by cross calibration with NBS 981. All Pb isotope ratios have been corrected relative to the NBS 981 composition of Todt et al. (1996). Based on repeated runs of NBS 981, the reproducibility of whole-rock Pb isotope measurements is better than 0.05% (2s). Blanks were <200 pg for Pb. Hf isotpes were analyzed on a VG MC-ICPMS. Within-run standard error for Hf isotope measurements is normally less than 22 ppm (2s). Minimum uncertainties are derived from external precision of JMC 475 standard measurements, which average 40 ppm (2s). Replicate analysis of our internal rock standard, pk-G-D12, over the course of analysis yield 0.283050  22 (2s, n = 30), which is indistinguishable from previously reported values (Kempton et al., 2000; 2002). Most of our samples were run in duplicate, and the data in Supplementary Information, Table S1 are averaged values. The data are corrected for mass fractionation during the run by normalization to 179Hf/177Hf of 0.7325 and are reported relative to an accepted value for JMC 475 of 0.282160, as recommended by Nowell et al. (1998). Unleached powders were used for major and trace element analyses. Major element concentrations were determined by XRF; trace element concentrations were determined by XRF and ICPMS. XRF analysis was performed at the University of Leicester on a Philips PW 1400 wave-length dispersive X-ray fluorescence mass spectrometer. ICPMS analysis was performed at the Open University, following sample dissolution at NIGL. Samples and standards were diluted to 100 ml in 2% HNO3 (1:1000 dilution) and analysed using an Agilent 7500 ICPMS. Samples were introduced into the plasma via a Bibington nebulizer at a rate of 0.4 ml per minute. The plasma was operated at 1400 W power, resulting in Ce+/CeO+ ratio of ~ 0.3%. Detection limits for most trace elements are generally < 10 ppt, equivalent to <10 ppb in the rock sample. Calibration is based on up to six reference materials, using recommended element concentrations. Drift was monitored by and corrected for using an internal standard solution containing Be, In, Rb, Tm, Re, and Bi introduced online during analysis; residual drift in individual elements was corrected for externally using repeat determinations of a representative sample after every 10 unknowns. Precision is generally about 1% r.s.d. for elements above mass 133 (i.e., Cs) and 1 to 3% for elements below this mass.