Supplementary information for Depleted mantle with highlyunradiogenic. Pb isotopes by Sanjeewa P.K. Malaviarachchi, Akio

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1 1 Supplementary information for Depleted mantle with highlyunradiogenic Pb isotopes by Sanjeewa P.K. Malaviarachchi, Akio Makishima, Masaaki Tanimoto, Takeshi Kuritani and Eizo Nakamura Supplementary Figure 1 Supplementary Figure 2 Supplementary Notes Supplementary Methods Supplementary References Supplementary Table 1 Supplementary Table 2 Supplementary Table 3 Supplementary Table 4 Supplementary Table 5 Supplementary Table 6

2 2 Supplementary Figure 1. Lithological map of the Horoman peridotite massif, Hokkaido, Japan (modified after Takahashi 15 ). Points indicate massive and thin-layer peridotite sample localities along the Horoman River.

3 3 1.16± 0.16 Ga (2SD) MSWD=7 ( 143 Nd/ 144 Nd=0.5114±3) initial 1.06±0.28 Ga (2SD) MSWD=19 ( 176 Hf/ 177 Hf=0.2825±3) initial 1.09± 0.13 Ga (2SD) MSWD=28 ( 143 Nd/ 144 Nd=0.5115±3) initial Massive peridotites Thin-layer peridotites Massive peridotites Thin-layer peridotites Supplementary Figure 2. Sm-Nd (a) and Lu-Hf (b) isochron diagrams of the massive and thin-layer peridotites. The data of Yoshikawa and Nakamura 17 are also displayed by open triangles in (a). Isochron ages and initial isotopic ratios with uncertainties for massive peridotites calculated using ISOPLOT 41 are shown in the figures. The thin-layer peridotites do not define clear isochrons both for Sm-Nd and Lu-Hf systems as discussed in the text. Our data integrated with the data of Yoshikawa and Nakamura 17 yields an isochron (thick line) with an age of 1.09±0.13 Ga.

4 4 SUPPLEMENTARY NOTES Pb paradox, so far suggested solutions and Pb isotopic mass balance calculation using the Horoman highly-unradiogenic peridotites Pb paradox is the Pb isotopic imbalance between the crust and the mantle. If the bulk silicate Earth (BSE) remained as a closed system and only internal (crustmantle) differentiation took place after the core formation, for Pb isotopic mass balance, the sum of the crust and mantle should lie on the 4.53 Ga geochron 7. However, the sum of this system plots significantly right to the geochron which requires a hidden unradiogenic reservoir. The lower crust and the core have been proposed as candidates for this missing reservoir 29,30, but neither of them contains sufficient unradiogenic Pb to resolve the paradox 7,31. Long-term segregation of sulfides to the core has been suggested to resolve this enigma 32 although the lack of experimental data on Pb partitioning between sulfides and silicates under lower mantle conditions limits its elucidation. Additional hypothetical candidate is a garnetite reservoir stored in the transition zone, but its physical/chemical characteristics are unresolved 31. Therefore, the Pb paradox still remains unsolved and requires immediate attention once substantially unradiogenic samples are detected. Fig. 3d shows the model results of the hypothetical highly-unradiogenic mantle (HM) with different mass fractions (X=mass of HM / mass of total upper mantle). Pb isotope variation curve of the HM overlaps with that of the Horoman highly-unradiogenic samples (HUM) and the average HUM composition corresponds to X=0.34. At X=0.34, derived HM composition is Pb=0.22ppm, 206 Pb/ 204 Pb=16.71, 207 Pb/ 204 Pb=15.22 and 208 Pb/ 204 Pb=36.28, which is essentially similar to the average of measured HUM composition (Supplementary Table 6). Accordingly, the HM model results successfully reproduce the observed HUM composition implying that

5 5 the hidden reservoir discovered as HUM contains sufficient unradiogenic Pb, to be a potential candidate for the Pb isotope paradox of the Earth. SUPPLEMENTARY METHODS All the analyses were performed in a clean laboratory at the Pheasant Memorial Laboratory for geochemistry and cosmochemistry (PML), Institute for Study of the Earth s Interior, Okayama University at Misasa, Japan 33. Peridotites were crushed, and the clean chunks were selected and washed with pure water. After drying, the massive and thin-layer peridotites were powdered in an alumina mill and a silicon nitride mortar respectively. Whole rock major element including Cr and Ni contents were determined in duplicates on fused disks by Phillips PW 2400 X-ray fluorescence spectrometer using ten-times diluted glass beads containing a lithium tetraborate flux 34 and the loss on ignition (LOI) was obtained gravimetrically. Replicate analyses gave <0.5 relative % difference. Li, Rb, Sr, Y, Cs, Ba, REEs, Pb, Th and U were determined by the ID-IS method 35 employing ICP- QMS (Agilent 7500cs, Yokogawa Analytical Systems) using 50 mg of samples. Another 50 mg was used for determination of B, Nb, Ta, Zr and Hf after the ID-IS method 35 by ICP-QMS using a Teflon bomb with Al addition 37. The analyses from sample digestion were done in duplicate, and average was presented. Analytical reproducibility (RSD) was <10 % for most elements. Pb isotope analysis of unleached samples of the massive peridotites were performed after HF-HBr decomposition, applying the two double spike method of Kuritani and Nakamura 38 using TIMS (Finnigan-MAT 262) equipped with five Faraday cups, at static multi collection mode ng of Pb were measured and the data were normalized to NBS 981 standard and the analytical reproducibility was 0.008%, 0.006% and 0.006% for 206 Pb/ 204 Pb, 207 Pb/ 204 Pb and 208 Pb/ 204 Pb respectively. Total procedural blanks were typically 15-20pg and are negligible. Unleached thin-

6 6 layer peridotites were analysed for Pb isotopes applying HF-HClO 4 decomposition and Pb purification method used for the leached samples as described below, using MC-ICP-MS (Neptune, Thermo Electron) 39. For Pb isotope analysis on the leached samples, 500 mg of sample was leached with 6M HCl for 1 h in an ultrasonic bath. This leaching condition was determined after tests with various conditions of 6M HCl for 20, 40, 60 and 80 min using and , which showed depleted and enriched Pb isotope signatures. Both samples showed no significant shifts (<0.1%) of Pb isotope ratios in each leaching, indicating freshness of the samples. After leaching, the samples were decomposed with HF-HClO 4, and Pb was purified and determined after the simple double spike method 39 using a MC-ICP-MS (Neptune, Thermo Electron). Total amounts of Pb in analysis were >0.8 ng, and reproducibility in the Pb isotope analysis at this level is <0.05% 39. The total blank levels were ~12 pg of which effects were <0.1% and negligible. The U/Pb and Th/Pb of the leached sample solution were determined by ICP-QMS. The Pb isotope results of unleached and leached samples were compared (leached ratio/unleached ratio) and found that the average difference in magnitude of a given Pb isotope ratio has no significant affect in the figures indicating freshness or unaltered characters of these peridotites. For Lu-Hf and Sm-Nd isotopic analysis, samples were digested similar to the trace element determination, with Lu-Hf and Sm-Nd spikes. Ti addition method 40 was performed for purification of Hf and Lu, and isotope ratios of Hf and Lu were determined applying the methods of Lu et al. 36 and Makishima and Nakamura 40 using a multi collector ICP-MS (Neptune, Thermo Electron). Purification of Nd and Sm was done using the method of Nakamura et al. 33. Analyses were done on TIMS (Finnigan MAT 262 and TRITON) for Nd and MC-ICP-MS (Neptune, Thermo Electron) for Sm. Normalizing values of isotope fractionation correction for 143 Nd/ 144 Nd and 176 Hf/ 177 Hf were and , respectively.

7 7 SUPPLEMENTARY REFERENCES 29. Asmerom, Y. & Jacobsen, B. The Pb isotopic evolution of the Earth: inferences from river water suspended loads. Earth. Planet. Sci. Lett. 115, (1993). 30. Kramers, J.D. & Tolstikhin, I. N. Two terrestrial lead isotope paradoxes, forward transport modelling, core formation and the history of the continental crust. Chem. Geol. 139, (1997). 31. Murphy, D.T., Kamber, B.S. & Collerson, K.D. A refined solution to the first terrestrial Pb-isotope paradox. J. Petrol. 44, (2002). 32. Hart, S.R. & Gaetani, G.A. Mantle Pb paradoxes: the sulfide solution. Contrib. Mineral. Petrol. 152, (2006). 33. Nakamura, E., Makishima, A., Moriguti, T., Kobayashi, K., Sakaguchi, C., Yokoyama, T., Tanaka, R., Kuritani, T. & Takei, H. Comprehensive geochemical analyses of small amounts (<100mg) of extraterrestrial samples for the analytical competition related to the sample return mission MUSES-C. Institute of Space Astronautical Science (Japan) Report SP 16, (2003). 34. Takei, H. Development of precise analytical techniques for major and trace element concentrations in rock samples and their applications to the Hishikari gold mine, southern Kyushu, Japan. Ph.D. thesis, Graduate School of Natural Science and Technology, Okayama University (2002). 35. Makishima, A. & Nakamura, E. Determination of major, minor and trace elements in silicate samples by ICP-SFMS applying isotope dilution internal standardisation (ID-IS) and multi stage internal standardisation. Geostand. Geoanal. Res. 30, (2006). 36. Lu Y., Makishima, A. & Nakamura, E. Coprecipitation of Ti, Mo, Sn and Sb with fluorides and application to determination of B, Ti, Zr, Nb, Mo, Sn, Sb, Hf and Ta by ICP-MS. Chem. Geol. 236, (2007).

8 8 37. Tanaka, R., Makishima, A., Kitagawa, H., Nakamura, E. Suppression of Zr, Nb, Hf and Ta coprecipitation in fluoride compounds for determination in Ca-rich materials. J. Anal. At. Spectrom. 18, (2003). 38. Kuritani, T & Nakamura, E. Highly precise and accurate isotopic analysis of small amounts of Pb using 205 Pb- 204 Pb and 207 Pb- 204 Pb, two double spikes. J. Anal. At. Spectrom. 18, (2003). 39. Makishima, A, Nath, B.N, & Nakamura, E. Precise determination of Pb isotope ratios by simple double spike MC-ICP-MS technique without Tl addition. J. Anal. At. Spectrom. 22, (2007). 40. Makishima, A. & Nakamura, E. New preconcentration technique of Zr, Nb, Mo, Hf, Ta and W employing coprecipitation with Ti compounds: its application to Lu-Hf system and sequential Pb-Sr-Nd-Sm separation. Geochemical Journal, 42, (2008). 41. Ludwig, K.R. Isoplot version A Geochronological Toolkit for Microsoft Excel, Berkeley Geochronology Center (2004).

9 9 Supplementary Table 1. Major element compositions of the Horoman peridotites measured by XRF Rock Sample Major elements (in wt %) type number SiO 2 TiO 2 Al 2 O 3 Cr 2 O 3 FeO a) MnO MgO NiO CaO Na 2 O K 2 O P 2 O 5 LOI b) Total Massive peridotites Plg.lhz a b c a a b c a b c Spl.lhz Hrz Thin-layer peridotites c) Plg.lhz HR HR HR HR HR HR HR HR HR Hrz HR Plg. lhz: plagioclase lherzolite; Spl. lhz: spinel lherzolite; Hrz: harzburgite a) Total Fe as FeO b) Loss on ignition c) The numbers of the thin-layer peridotites indicate the distance (+/- cm) from the standard-horizon sample (HR 0)

10 Supplementary Table 2. Trace element compositions of the Horoman peridotites measured by ICP-QMS. Rock Sample Trace elements (in ppm) type number Li B Rb Sr Y Zr Nb Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta Pb Th U Massive peridotites Plg.lhz a b c a a b c a b c Spl.lhz Hrz Thin-layer peridotites Plg.lhz HR HR HR HR HR HR HR HR HR Hrz HR Abbreviations and the notation for samples are the same as in the Supplementary Table 1 10

11 11 Supplementary Table 3. Pb isotopic composition of the Horoman peridotites Rock Sample # U/Pb a) Th/Pb a) Pb * ( b) values on unleached samples c) values on leached samples Initial ratios at 1 Ga d) type 206 Pb/ 204 Pb 207 Pb/ 204 Pb 208 Pb/ 204 Pb 206 Pb/ 204 Pb 207 Pb/ 204 Pb 208 Pb/ 204 Pb 206 Pb/ 204 Pb 207 Pb/ 204 Pb 208 Pb/ 204 Pb (A) Measured values Massive peridotites Plg.lhz a b c a a b c a b c Spl.lhz Hrz Thin-layer peridotites Plg.lhz HR HR HR HR HR HR HR HR HR Hrz HR Standards e) NBS 981 (n=30) SD (B) Compiled values Most Depleted MORB f) GLOSS g) MORB source mantle estimates h) S H C R Abbreviations and the notation for samples is the same as in the Supplementary Table 1 a) Measured ratio on leached samples b) Pb* = [2Pb/(Ce+Pr)] N, N indicates all the elements are normalized to the Primitive mantle values 25 c) Massive peridotite data from TIMS (MAT 262) and thin peridotite data from MC-ICP-MS (Neptune) d) Calculated based on the leached data e) Uncertainties for MC-ICP-MS f) Present isotope values from Strecke et al. 26, U/Pb & Th/Pb values from Hofmann 1 g) Data from Plank & Langumuir 20 h) Data from Strecke et al. 26 (S), Hart & Saudigel 27 (H), Chauval et al. 28 (C) and Rekhämper & Hofmann 29 (R)

12 12 Supplementary Table 4. Nd and Hf isotopic compositions of the Horoman peridotites Rock Sample # Nd (ppm) Sm (ppm) 143 Nd/ 144 Nd a) 147 Sm/ 144 Nd εnd(0) b) Hf (ppm) Lu (ppm) 176 Hf/ 177 Hf a) 176 Lu/ 177 Hf εhf(0) c) Initial ratio at 1 Ga type 143 Nd/ 144 Nd 176 Hf/ 177 Hf Massive peridotites Plg.lhz ± 6 (T) ± a ± 7 (T) b ± 6 (T) ± c ± 5 (T) ± ± 5 (T) ± a ± 4 (T) ± ± 5 (T) ± a ± 5 (T) ± b ± 4 (T) ± c ± 8 (T) ± ± 5 (T) ± a ± 4 (T) ± b ± 5 (T) ± c ± 4 (T) ± Thin-layer peridotites Plg.lhz HR ± 5 (T) ± HR ± 4 (T) ± HR ± 5 (T) ± HR ± 6 (M) ± HR ± 5 (T) ± HR ± 5 (M) ± HR ± 8 (M) ± HR ± 6 (M) ± HR ± 4 (T) ± Hrz HR ± 8 (T) ± Standards PML Nd (n=13) By MAT 262 (M) ± 15 (2 SD) Corresponding La Jolla ratio PML Nd (n=10) By TRITON (T) ± 12 (2 SD) Corresponding La Jolla ratio Presernt average MORB d) MORB source mantle estimates e) S HH Abbreviations and the notation for samples are the same as in the Supplementary Table 1 a) Uncertainties are in-run analytical errors (2SE) in last decimal place; (T) - measured by TIMS (TRITON); (M) - measured by TIMS (MAT 262) b) εnd( 0) was calculated based on 143 Nd/ 144 Nd CHUR(0) = at La Jolla Nd = ; Total blanks for Nd and Sm were 1.2 pg (n=4) and 1.3 pg (n=3) respectively; Nd concentration was determined simultaneously with Nd isotope ratio by TIMS; Sm concentartion was determined by ID-MC-ICP-MS (Neptune) c) εhf( 0) was calculated based on 176 Hf/ 177 Hf CHUR(0) = ; Total blanks for Hf and Lu were 22.4 pg (n=4) and 2.9 pg (n=4); Hf concentration was determined simultaneously with Hf isotope ratio by MC-ICP-MS (Neptune) and Lu concentration was determined by ID-MC-ICP-MS (Neptune) d) 1 Ga isotope ratios of average MORB were calculated using present data compiled from PetDB database ( and Hofmann 1 e) Isotope ratios of the MORB source from Stracke et al. 26 (S), Hauri & Hart 30 (HH)

13 13 Supplementary Table 5. Compiled Pb isotopic data of world-wide peridotites Tectonic setting 206 Pb/ 204 Pb 207 Pb/ 204 Pb 208 Pb/ 204 Pb Tectonic setting 206 Pb/ 204 Pb 207 Pb/ 204 Pb 208 Pb/ 204 Pb & location & location Orogenic peridotites Mantle xenoliths Lherz a) (France) South Korea e) Spitsbergen f) Beni Bousera a) Massif Central g) (Morocco) (France) Zabargad a) (Red Sea) Canada h) (in kimberlites) Lanzo a) (Italy) Balmuccia b) (Italy) Tinaquillo c) (Venezuella) Hungary i) Abyssal peridotites Romania i) South west Indian ridge d) a) Hamelin, B., Allergre, C. J. Earth. Planet. Sci. Lett. 91, (1988) b) Mukasa, S.B, Shervais, J.W. Lithos 48, (1999) c) Choi, S.H., Mukasa, S.B., Andronikov, A.V., Marcano, M.C. Contrib.Mineral.Petrol. 153, (2006) d) Sakaguchi, C. Warren, J.M., Shimizu, N., Dick, H.J., Nakamura, E. EOS Trans. AGU 86(52), T41E-1352 (2005) e) Choi, S.H, Kwon, S., Mukasa, S.B., Sagong, H. Chem.Geol. 221, (2005) f) Ionov, D.A., Bodinier, J-L., Mukasa, S.B., Zanetti, A. J.Petrl. 43, (2002) g) Zangana, N.A., Downes, H., Thirlwall, M.F., Hegner, E. Contrib.Mineral.Petrl., 127, (1997) h) Schmidberger, S.S., Simonetti, A., Francis, D. Geochim. Cosmochim. Acta., 65, (2001) i) Rosenbaum, J.M., Wilson, M. J.Geophys.Res. 102, (1997)

14 14 Supplementary Table 6. Calculation of the hypothetical highly-unradiogenic mantle composition a) Reservoir ( 206 Pb/ 204 Pb) ( 207 Pb/ 204 Pb) ( 208 Pb/ 204 Pb) Pb (ppm) Mass b) (10 24 g) Bulk Silicate Earth c) Upper crust d) Lower crust d) Depleted mantle (DM) c) see e) Total upper mantle (TM) 1170 Hypothetical highly-unradiogenic mantle (HM) f) X e) Average of measured Horoman HUM (n=5) a) Model assumes that the lower mantle isotopic composiiton approximates that of the undifferentiated (primitive) mantle and that the upper mantle Pb is hosted in silicates and therefore sulfide control is insignificant. b) Masses of the reservoirs are from Asmerom and Jacobsen 21 c) Average composition given by Workmann and Hart 2 d) Average composition given by Kramers and Tolstikhin 30 e) Mass proportion X = HM / TM where TM = DM + HM f) Calculated values as a function of X

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