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1 Supplementary Material Machida et al. (214), Regional mantle heterogeneity regulates melt production along the Réunion hotspot-influenced Central Indian Ridge COMPILED DATA FOR THE RÉUNION HOTSPOT AND NEIGHBORING VOLCANIC EDIFICES, AND DEFINITIONS OF REPRESENTATIVE SAMPLE AND MELT END MEMBER COMPOSITIONS EXAMINED IN THIS STUDY The Réunion hotspot formed a volcanic trail from Réunion Island, the present location of the Réunion plume, to the Deccan continental flood basalt province (Fig. 1a in the main text). We compiled data for basalts from Réunion and Mauritius Islands and along-trail basalts collected by drilling during the Ocean Drilling Program (ODP) Leg 115 for the Réunion hotspot. Geochemical data are compiled from the GEOROCK database, except for samples from Leg 115 (Baxter, 199, White et al., 199). Our compilation reveals that identical enriched compositions are visible in basalts from Réunion Island and the Older series of Mauritius Island. These have the most-radiogenic Sr isotopic compositions in the region (Fig. 4 in the main text) (e.g., Albarède and Tamagnan, 1988; Fisk et al., 1988; Mahoney et al., 1989; Albarède et al., 1997; Fretzdroff and Haase, 22; Sheth et al., 23; Nohda et al., 25; Paul et al., 25; Moore et al., 211). This component also contributes to the Deccan Traps (Peng and Mahoney, 1995) and to the seamount trail from the western Deccan Traps through the Mascarene Plateau to the east of Mauritius Island (Baxter, 199; White et al., 199), and the Younger series of Mauritius (Nohda et al., 25; Paul et al., 25) (Fig. 4 in the main text). A radiogenic-melt end member derived from the Réunion plume (Réunion Island and the Older series of Mauritius Island) is defined by the composition of representative sample M12 (Moore et al., 211). We call this end member Radiogenic Enriched Component 1 (). The geochemical composition of sample M12 is given in Table 1 in the main text, and is depicted in Fig. 3 in the main text. Basalts from the Intermediate series of Mauritius Island and Rodrigues Ridge have a less radiogenic isotopic composition and higher Nb/Zr, Ba/La, and Ba/Nb than the Réunion hotspot (Figs. S1, S2, and S3). Therefore, another trace-element-enriched-melt end member, derived from the source of the Intermediate series of the Mauritius Island and Rodrigues ridge, is also defined by the composition of representative sample B5 (Sheth et al., 23). We call this end member Radiogenic Enriched Component 2 (). The geochemical composition of sample B5 is given in Table 1 in the main text, and is depicted in Fig. 3 in the main text.

2 The third distinctive melt end member, having radiogenic isotopic composition but depleted trace element geochemistry, is derived from the source of Gasitao Ridge. We defined sample DR8-1 (Nauret et al., 26) with the highest 87 Sr/ 86 Sr (=.73973) as a representative sample for the radiogenic-melt end member Radiogenic Depleted Component (). The geochemical composition of sample DR8-1 is given in Table 1 in the main text, and is depicted in Fig. 3 in the main text. DETAILED DESCRIPTION OF MELT MIXING MODEL To define which radiogenic components contribute to magma genesis for segments Central Indian Ridge, we conduct numerical mixing calculations for Sr, Nd, and Pb isotopes and Nb/Zr, Ba/Nb, and Ba/La ratios (Figs. 4 and 5 in the main text, and Figs. S4, S5, S6, S7, S1, and S11). Three radiogenic-melt end members (,, and ) are each assigned representative samples as described in the main text. We calculate the melt compositions for D--derived melt end member, assuming that the source mantle (spinel peridotite) has a composition (Workman and Hart, 25) and 15% degree of melting occurs. Mineral-melt partition coefficients, mantle mineralogy, and consumed mineral proportions for mantle melting are presented in Table S3. EM-1 melt, the averaged composition of mafic basalts from the Pitcairn volcano, is also considered. The averaged composition is calculated on the basis of sample selection by Jackson and Dasgupta (28) and compositions from the GEOROCK database. The compositions for all end members are listed in Table 1 in the main text. THREE-DIMENSIONAL PLOT FOR SR, ND, AND PB ISOTOPIC COMPOSITIONS OF CIR BASALTS Sr, Nd, and Pb isotopic compositions of CIR MORB are presented on three-dimensional (3D) diagrams (Fig. S4), together with those of the Réunion hotspot and neighboring volcanic edifices. Then, isotopic variation of CIR MORB and differences of isotopic compositions for each radiogenic melt end member discussed in this report, especially (or basalts from Réunion Island and the Older series of Mauritius Island), (or basalts from Rodrigues Ridge and the Intermediate series of the Mauritius Island), and EM-1, are presented more clearly. Data are presented using the Gnuplot program ( A shell script for commands of the Gnuplot to plot data on 87 Sr/ 86 Sr, 143 Nd/ 144 Nd, and 27 Pb/ 24 Pb, and 26 Pb/ 24 Pb, 27 Pb/ 24 Pb, and 28 Pb/ 24 Pb spaces respectively, and loading data file are shown in additional supplementary materials. The displayed diagram is free to rotate spatially if we run a shell script. Fig. S4 shows two snapshots of each 3D diagram. Furthermore, movies showing each 3D diagram rotating a vertical three hundred and sixty degrees are also

3 provided as Figs. S1 and S11. Five additional supplementary materials for 3D diagram accompany this paper on as listed below. Files to draw three-dimensional diagrams using gnuplot program Command Script A: script_for_sr-nd-7pb-plot.txt Command Script B: script_for_6-7-8pb-plot.txt Loading data: Data-CIR&Reunion.txt Movies for three-dimensional diagrams Movie A: Fig.S1_CIR-Reunion_Sr-Nd-7Pb.mp4 Movie B: Fig.S11_CIR-Reunion_6-7-8Pb.mp4 Captions for movies Fig. S1. Movie for three-dimensional diagram showing variations of Sr, Nd, and Pb isotopes of basalts from Gasitao Ridge and the Central Indian Ridge for 15 S through 2 S. Figure corresponds to free-rotatable 3D diagram, shown by the Gnuplot program ( viewed from 7 of horizontal, and is rotating from to 36 of vertical. Symbols are shown in the legend, and almost correspond to those of Fig. 2 in the main text. Fig. S11. Movie for three-dimensional diagram showing variations of three Pb isotopes of basalts from Gasitao Ridge and the Central Indian Ridge for 15 S through 2 S. Figure corresponds to free-rotatable 3D diagram, shown by the Gnuplot program ( viewed from 8 of horizontal, and is rotating from to 36 of vertical. Symbols as in Fig. S1. DETAILED DESCRIPTIONS OF MANTLE MELTING MODEL We examine the origins of various trace element compositions of basalts from the Réunion hotspot and neighboring volcanic edifices using a melting model (Fig. 7 in the main text). The source composition for three radiogenic-melt end members (,, and ) is calculable from the composition of their representative basalt samples. For source calculations, we assume 25% or 1% garnet peridotite melting, 5% garnet peridotite melting, and 25% or 5% spinel peridotite melting for,, and, respectively. Then we examine the Nb/Zr, Ba/Nb, and Ba/La ratios of the produced melts from each source under different degrees of melting for the same source lithology (Fig. 7 in the main text, and Fig. S8). Mineral-melt partition coefficients, source lithology, and consumed mineral proportions for mantle melting

4 are listed in Table S3. References Albarède, F., Luais, B., Fitton, J. G., Semet, M., Kaminski, E., Upton, B. G. J., Bachèlery, P. and Cheminèe, J.-L. (1997) The geochemical regimes of Piton de la Fournaise volcano (Réunion) during the last 53 years. J. Petrol. 38, Albarède, F. and Tamagnan, V. (1988) Modelling the recent geochemical evolution of the Piton de la Fournaise volcano, Réunion Island. J. Petrol. 29, Baxter, A. N. (199) Major and trace element variations in basalts from Leg 115. Proc. ODP, Sci. Res. (R. A. Duncan, J. Backman, L. C. Peterson, et al. eds.) 115, College Station, TX (Ocean Drilling Program), pp Cordier, C., Benoit, M., Hémond, C., Dyment, J., Le Gall, B., Briais, A. and Kitazawa, M. (21) Time scales of melt extraction revealed by distribution of lava composition across a ridge axis. Geochem. Geophys. Geosyst. 11, QAC6, doi:1.129/21gc374. Eggins, S. M., Woodhead, J. D., Kinsley, L. P. J., Mortimer, G. E., Sylvester, P., McCulloch, M. T., Hergt, J. M. and Handler, M. R. (1997) A simple method for the precise determination of 4 trace elements in geological samples by ICPMS using enriched isotope internal standardisation. Chem. Geol. 134, doi:1.116/s9-2541(96)1-3. Fisk, M. R., Upton, B. G. J., Ford, C. E. and White, W. M. (1988) Geochemical and experimental study of the genesis of magmas of Reunion Island, Indian Ocean. J. Geophys. Res. 93, Fretzdorff, S. and Haase, K. M. (22) Geochemistry and petrology of lavas from the submarine flanks of Reunion Island western Indian Ocean: Implications for magma genesis and the mantle source. Mineral. Petrol. 75, , doi:1.17/s Hellebrand, E., Snow, J. E., Hoppe, P. and Hofmann, A. W. (22) Garnet-field melting and late-stage refertilization in residual abyssal peridotites from the Central Indian Ridge. J. Petrol. 43, Jackson, M. G. and Dasgupta, R. (28) Compositions of HIMU, EM1, and EM2 from global trends between radiogenic isotopes and major elements in ocean island basalts. Earth Planet. Sci. Lett. 276, , doi:1.116/j.epsl Johnson, K. T. M. (1998) Experimental determination of partition coefficients for rare earth and high-field-strength elements between clinopyroxene, garnet, and basaltic melt at high pressures. Contrib. Mineral. Petrol. 133, 6-68.

5 Kelemen, P. B., Yogodzinski, G. M. and Scholl D. W. (23) Along-strike variation the Aleutian Island Arc: Genesis of High Mg# andesite and implication for continental crust. in Inside the Subduction Factory (Eiler J., ed.) Geophys. Monogr. 138, AGU, Washington, D. C., pp Kinzler, R. J. (1997) Melting of mantle peridotite at pressures approaching the spinel to garnet transition: Application to mid-ocean ridge basalt petrogenesis. J. Geophys. Res. 12, Mahoney, J. J., Natland, J. H., White, W. M., Poreda, R., Bloomer, S.H. and Baxter, A. N. (1989) Isotopic and geochemical provinces of the Western Indian Ocean spreading centers. J. Geophys. Res. 94, Moore, J., White, W. M., Paul, D., Duncan, R. A., Abouchami, W. and Galer S. J. G. (211) Evolution of shield-building and rejuvenescent volcanism of Mauritius. J. Volcanol. Geotherm. Res. 27, 47-66, doi:1.116/j.jvolgeores Murton, B. J., Tindle, A. G., Milton, J. A. and Sauter, D. (25) Heterogeneity in southern Central Indian Ridge MORB: implications for ridge hot spot interaction. Geochem. Geophys. Geosyst. 6, Q3E2, doi:1.129/24gc798. Nauret, F., Abouchami, W., Galer, S. J. G., Hofmann, A. W., Hémond, C., Chauvel, C. and Dyment, J. (26) Correlated trace element-pb isotope enrichments in Indian MORB along 18 2 S, Central Indian Ridge. Earth Planet. Sci. Lett. 245, , doi:1.116/j.epsl Nohda, S., Kaneoka, I., Hanyu, T., Xu, S. and Uto, K. (25) Systematic variation of Sr-, Ndand Pb-isotopes with time in lavas of Mauritius, Réunion hot spot. J. Petrol. 46, , doi:1.193/petrology/egh85. Paul, D., White, W. M. and Blichert-Toft, J. (25) Geochemistry of Mauritius and the origin of rejuvenescent volcanism on oceanic island volcanoes. Geochem. Geophys. Geosyst. 6, Q67, doi:1.129/24gc883. Peng, Z. X. and Mahoney, J. J. (1995) Drillhole lavas from the northwestern Deccan Traps, and the evolution of Reunion hotspot mantle. Earth Planet. Sci. Lett. 134, Sheth, H., Mahoney, J. J. and Baxter, A. (23) Geochemistry of lavas from Mauritius, Indian Ocean: Mantle sources and Petrogenesis. Int. Geol. Rev. 45, , doi:1.2747/ Walter, M. J. (1998) Melting of garnet peridotite and the origin of Komatiite and depleted lithosphere. J. Petrol. 39, White, W. M., Cheatham, M. M. and Duncan, R. A. (199) Isotope geochemistry of Leg 115 basalts and inferences on the history of the Reunion mantle plume. Proc. ODP, Sci. Res. (R. A. Duncan, J. Backman, L. C. Peterson, et al., eds.) 115. College Station,

6 TX (Ocean Drilling Program), pp Workman, R. K. and Hart, S. R. (25) Major and trace element composition of the depleted MORB mantle (). Earth Planet. Sci. Lett. 231, 53 72, doi:1.116/j.epsl

7 Nb/Zr Sr/86Sr Nb/Zr Nd/144Nd Rodrigues Ridge Gasitao Ridge Seamount Trail (ODP Leg.115) Réunion Island Older Series of Mauritius Is. Younger Series of Mauritius Is. Interm. Series of Mauritius Is. Nb/Zr Pb/24Pb Fig. S1 Figs. S1-S3. Nb/Zr (S1), Ba/La (S2), and Ba/Nb (S3) vs. 87 Sr/ 86 Sr, 143 Nd/ 144 Nd, and 26 Pb/ 24 Pb variation diagrams for the Réunion hotspot and neighboring volcanic edifices. Orange, yellow, and brown circles represent,, and radiogenic-melt end members, respectively. Compositions of radiogenic-melt end members are listed in Table 1 of main text. The variation range of D- and averaged (labeled ) are from Workman and Hart (25).

8 2 15 Ba/La Sr/86Sr 2 15 Ba/La Nd/144Nd 2 15 Rodrigues Ridge Gasitao Ridge Seamount Trail (ODP Leg.115) Réunion Island Older Series of Mauritius Is. Younger Series of Mauritius Is. Interm. Series of Mauritius Is. Ba/La Pb/24Pb Fig. S2

9 25 2 Ba/Nb Sr/86Sr 25 2 Ba/Nb Nd/144Nd 25 2 Rodrigues Ridge Gasitao Ridge Seamount Trail (ODP Leg.115) Réunion Island Older Series of Mauritius Is. Younger Series of Mauritius Is. Interm. Series of Mauritius Is. Ba/Nb Pb/24Pb Fig. S3

10 27 Pb/ 24 Pb av. E- 3% 27 Pb/ 24 Pb E Nd/ 144 Nd D- 2% EM-1 87 Sr/ 86 Sr Sr/ Sr av Nd/ 144 Nd D Pb/ 24 Pb EM-1 28 Pb/ 24 Pb EM % % E- 26 Pb/ 24 Pb av Pb/ 24 Pb D E av D Pb/ Pb Pb/ 24 Pb 19.5 Fig. S4. Three-dimensional diagrams showing variations of Sr, Nd, and Pb isotopes ((a) and (b)), and three Pb isotopes ((c) and (d)) of basalts from Gasitao Ridge and the Central Indian Ridge for 15 S through 2 S. Figs. (a), (b), (c), and (d) respectively correspond to snapshot of free-rotatable 3D diagram, shown by the Gnuplot program ( viewed from 7 of horizontal and 325 of vertical, 7 of horizontal and 22 of vertical, 8 of horizontal and 255 of vertical, 8 of horizontal and 32 of vertical (see additional supplementary materials for details to plot free-rotatable 3D diagram). Symbols and references for other compiled data as in Fig. 2.

11 .35.3 Mauritius Intermediate & Rodrigues Ridge.25 Nb/Zr.2.15 Réunion, Mauritius Old, & Seamount Trail.1 EM-1.5 2% Gasitao Ridge 3% Sr/86Sr Nb/Zr EM Nd/144Nd Segment 15 Segment 15 across Gasitao Ridge Segment 15B (whole rock) Segment 15C (whole rock) Segment 16 (glass) Segment 17 (whole rock) Segment 17 (glass) Segment 18A (whole rock) Segment 18A (glass) Segment 18B (glass) 2%.2 Nb/Zr.15.1 EM-1.5 2% 3% Pb/24Pb Fig. S5 Figs. S5-S7. Nb/Zr (S5), Ba/La (S6), and Ba/Nb (S7) vs. 87 Sr/ 86 Sr, 143 Nd/ 144 Nd, and 26 Pb/ 24 Pb variation diagrams for basalts from Gasitao Ridge and the Central Indian Ridge between 15 and 2 S. Previously reported CIR data (CIR others), along axis data from segment 15 (Segment 15), and across axis data from segment 15 (Segment 15 across) are from the PetDB database, Murton et al. (25) and Nauret et al. (26), and Cordier et al. (21), respectively. The compositional range for the Réunion hotspot and neighboring volcanic edifices, and composition of radiogenic-melt end members are from Figs. S1, S2, and S3. Variation range of D- and averaged (labeled ) are from Workman and Hart (25). The orange dash line and yellow and brown lines represent results of binary mixing between D--derived melt and,, and, respectively. The light blue lines represent results of binary mixing between D--derived melt and EM-1 melt, and ternary mixing D--derived melt,, and EM-1 melt. 2% and 3% respectively represent amounts of EM-1 melt and.

12 2 Mauritius Intermediate & Rodrigues Ridge 15 Réunion, Mauritius Old, & Seamount Trail Ba/La 1 EM-1 5 2% Gasitao Ridge 3% Sr/86Sr 2 15 Ba/La 1 EM-1 5 2% Segment 15 Segment 15 across Nd/144Nd 2 15 Gasitao Ridge Segment 15B (whole rock) Segment 15C (whole rock) Segment 16 (glass) Segment 17 (whole rock) Segment 17 (glass) Segment 18A (whole rock) Segment 18A (glass) Segment 18B (glass) Ba/La 1 EM-1 5 2% 3% Pb/24Pb Fig. S6

13 25 2 Mauritius Intermediate & Rodrigues Ridge Ba/Nb 15 1 Réunion, Mauritius Old, & Seamount Trail 5 2% 3% Gasitao Ridge Sr/86Sr 25 2 Ba/Nb 15 1 EM-1 5 Segment 15 Segment 15 across Nd/144Nd 3% 2% 25 2 Gasitao Ridge Segment 15B (whole rock) Segment 15C (whole rock) Segment 16 (glass) Segment 17 (whole rock) Segment 17 (glass) Segment 18A (whole rock) Segment 18A (glass) Segment 18B (glass) 1 Ba/Nb 1 EM-1 5 2% 3% Pb/24Pb Fig. S7

14 2 Mauritius Old Melting.25 Mauritius Old Melting.1 Mauritius Interm. Melting.5 Gasitao Melting.25 Gasitao Melting Ba/La Ba/Nb F Fig. S8. Diagrams of Ba/La and Ba/Nb vs. degree of partial melting (F), comparing results of batch melting models. Black lines respectively indicate Ba/La and Ba/Nb values for representative basalt from Réunion Island and the Older series of Mauritius Island (sample M12, Moore et al., 211, Ba/La = 8.36 and Ba/Nb = 8.34), basalt from Rodrigues Ridge and the Intermediate series of Mauritius Island (sample B5, Sheth et al., 23, Ba/La = and Ba/Nb = 1.2), and basalt from Gasitao Ridge (sample DR8-1, Nauret et al., 26, Ba/La = 1.6 and Ba/Nb = 2.86). The composition of source for each melting model is calculable from the composition of representative basalt assuming 25% or 1% melting (Mauritius Old Melting.25 or.1), the composition of representative basalt assuming 5% melting (Mauritius Interm. Melting.5), and composition of representative basalt assuming 25% or 5% (Gasitao Melting.25 or.5).

15 Rodrigues Ridge Gasitao Ridge Seamount Trail (ODP Leg.115) Réunion Island Older Series of Mauritius Is. Younger Series of Mauritius Is. Interm. Series of Mauritius Is. LOI 6 4 Gasitao Ridge Segment 15B (whole rock) Segment 15C (whole rock) Segment 16 (glass) Segment 17 (whole rock) Segment 17 (glass) Segment 18A (whole rock) Segment 18A (glass) Segment 18B (glass) Sr/86Sr LOI Nd/144Nd LOI Pb/24Pb Fig. S9. H2O or Loss On Ignition vs. 87 Sr/ 86 Sr, 143 Nd/ 144 Nd, and 26 Pb/ 24 Pb variation diagrams for basalts from Gasitao Ridge and the Central Indian Ridge between 15 and 2 S.

16 Table S1. Locations of the sampling sites. Site name Place Latitude (S) Longitude (E) Depth (m) RC5 Segment 15C ' ' -29 RC9 Segment ' ' RC1 Segment ' ' -275 RC11 Segment ' ' -287 RC12 Segment ' ' RC13 Segment ' ' RC14 Segment 18A ' ' RC15 Segment 18B ' ' RC16 Segment ' ' -319 RC21 Segment ' ' DR1 Gasitao Ridge ' ' DR2 Segment 15B ' ' -228 DR4 Segment 15B ' ' DR6 Segment 18A ' ' -392 DR7 Segment ' ' DR8 Segment ' ' DR9 Segment ' ' -3233

17 Table S2a. Major and trace element compositions of basaltic glasses. Sample Name RC9 RSD (%) RC1 RSD (%) RC11 RSD (%) SiO TiO Al2O FeO MnO MgO CaO Na2O K2O P2O Total H2O(+) Sc V Cr Co Ni Rb Sr Y Zr Nb Sb Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta Pb Th U

18 Table S2a. (continued) Sample Name RC12 RSD (%) RC13 RSD (%) RC14 RSD (%) SiO TiO Al2O FeO MnO MgO CaO Na2O K2O P2O Total H2O(+) Sc V Cr Co Ni Rb Sr Y Zr Nb Sb Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta Pb Th U

19 Table S2a. (continued) Sample Name RC15 RSD (%) RC16 RSD (%) RC21 RSD (%) SiO TiO Al2O FeO MnO MgO CaO Na2O K2O P2O Total H2O(+) Sc V Cr Co Ni Rb Sr Y Zr Nb Sb Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta Pb Th U

20 Table S2a. (continued) Sample Name DR6C RSD (%) DR7C RSD (%) DR8M RSD (%) SiO TiO Al2O FeO MnO MgO CaO Na2O K2O P2O Total H2O(+) Sc V Cr Co Ni Rb Sr Y Zr Nb Sb Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta Pb Th U

21 Table S2a. (continued) Sample Name DR9A RSD (%) SiO TiO Al2O FeO MnO MgO CaO Na2O K2O P2O Total H2O(+) Sc V Cr Co Ni Rb Sr Y Zr Nb Sb Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta Pb Th U

22 Table S2b. Whole rock major and trace element compositions of basalts. Sample Name RC5 DR1A DR1B DR1C DR2A DR2B DR2C SiO TiO Al2O Fe2O MnO MgO CaO Na2O K2O P2O Total H2O(+) Sc Co Zn Rb Sr Y Zr Nb Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Yb Lu Hf Ta Pb Th U

23 Table S2b. (continued) Sample Name DR4A DR4B DR4C1 DR6A DR6B DR6C DR7A SiO TiO Al2O Fe2O MnO MgO CaO Na2O K2O P2O Total H2O(+) Sc Co Zn Rb Sr Y Zr Nb Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Yb Lu Hf Ta Pb Th U

24 Table S2b. (continued) Sample Name DR7B DR8B DR8C DR8E DR9A SiO TiO Al2O Fe2O MnO MgO CaO Na2O K2O P2O Total H2O(+) Sc Co Zn Rb Sr Y Zr Nb Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Yb Lu Hf Ta Pb Th U

25 Table S2. Isotopic compositions of basalts and basaltic glasses. Sample Name Lithology 87Sr/86Sr 2σ 143Nd/144Nd 2σ 26Pb/24Pb 2σ 27Pb/24Pb 2σ 28Pb/24Pb 2σ RC9 glass RC1 glass RC11 glass RC12 glass RC13 glass RC14 glass RC15 glass RC16 glass RC21 glass DR6C glass DR7C glass DR8M glass DR9A glass RC5 whole rock DR1B whole rock DR2A whole rock DR4B whole rock DR6C whole rock DR7A whole rock DR8B whole rock DR8C whole rock DR9A whole rock

26 Table S2d. Referenced Standard Values and Analytical Results by ICP-MS for W-2. Mass Element W-2 This study (%) 45 Sc Co Zn Ga Rb Sr Y Zr Nb Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Yb Lu Hf Ta Pb Th U Note: W-2 values from Eggins et al. (1997)

27 Table S3. Parameters used in the mantle melting model. Reaction mode Source mode Lithology Garnet peridotite Spinel peridotite Garnet peridotite Spinel peridotite Ol Opx Cpx Gar.11.9 Sp.11.3 References Walter, 1998 Kinzler, 1997 Hellebrand et al., 22 Johnson et al., 1998 Partition coefficients Elements Ba Nb La Zr Ol Opx Cpx Gar Sp References Kelemen et al., 23 Kelemen et al., 23 Kelemen et al., 23 Kelemen et al., 23

Supplementary Figure 1 Map of the study area Sample locations and main physiographic features of the study area. Contour interval is 200m (a) and 40m

Supplementary Figure 1 Map of the study area Sample locations and main physiographic features of the study area. Contour interval is 200m (a) and 40m (b). Dashed lines represent the two successive ridge