Helium and lead isotopes reveal the geochemical geometry of the Samoan plume

Abstract

Hotspot lavas erupted at ocean islands exhibit tremendous isotopic variability, indicating that there are numerous mantle components1,2 hosted in upwelling mantle plumes that generate volcanism at hotspots like Hawaii and Samoa3. However, it is not known how the surface expression of the various geochemical components observed in hotspot volcanoes relates to their spatial distribution within the plume4,5,6,7,8,9,10. Here we present a relationship between He and Pb isotopes in Samoan lavas that places severe constraints on the distribution of geochemical species within the plume. The Pb-isotopic compositions of the Samoan lavas reveal several distinct geochemical groups, each corresponding to a different geographic lineament of volcanoes. Each group has a signature associated with one of four mantle endmembers with low 3He/4He: EMII (enriched mantle 2), EMI (enriched mantle 1), HIMU (high µ = 238U/204Pb) and DM (depleted mantle). Critically, these four geochemical groups trend towards a common region of Pb-isotopic space with high 3He/4He. This observation is consistent with several low-3He/4He components in the plume mixing with a common high-3He/4He component, but not mixing much with each other. The mixing relationships inferred from the new He and Pb isotopic data provide the clearest picture yet of the geochemical geometry of a mantle plume, and are best explained by a high-3He/4He plume matrix that hosts, and mixes with, several distinct low-3He/4He components.

Figure 1: Map of the Samoan hotspot showing the division of the hotspot into three parallel volcanic lineaments.
Figure 2: Pb-isotopic plot showing the isotopic separation of the volcanic lineaments in Samoa and the convergence of the four geochemical groups on the high-3He/4He component region.
Figure 3: Relationship between He and Pb isotopic ratios in Samoan lavas.
Figure 4: Conceptual model of the geochemical geometry of the Samoan plume, as sampled by shield-stage lavas, and how it relates to the geochemical distinction among the parallel volcanic lineaments.

References

  1. 1

    Zindler, A. & Hart, S. Chemical geodynamics. Annu. Rev. Earth Planet. Sci. 14, 493–571 (1986)

    CAS  Article  ADS  Google Scholar 

  2. 2

    Hofmann, A. in The Mantle and Core (ed. Carlson, R. W. ) Vol. 2 Treatise in Geochemistry 61–101 (Elsevier, 2003)

    Google Scholar 

  3. 3

    Morgan, W. J. Convection plumes in the lower mantle. Nature 230, 42–43 (1971)

    ADS  Article  Google Scholar 

  4. 4

    Abouchami, W. et al. Lead isotopes reveal bilateral asymmetry and vertical continuity in the Hawaiian mantle plume. Nature 434, 851–856 (2005)

    CAS  Article  ADS  PubMed  Google Scholar 

  5. 5

    Weis, D., Garcia, M. O., Rhodes, J. M., Jellinek, M. & Scoates, J. S. Role of the deep mantle in generating the compositional asymmetry of the Hawaiian mantle plume. Nature Geosci. 4, 831–838 (2011)

    CAS  Article  ADS  Google Scholar 

  6. 6

    Huang, S., Hall, P. S. & Jackson, M. G. Geochemical zoning of volcanic chains associated with Pacific hotspots. Nature Geosci. 4, 874–878 (2011)

    CAS  Article  ADS  Google Scholar 

  7. 7

    Payne, J. A., Jackson, M. G. & Hall, P. S. Parallel volcano trends and geochemical asymmetry of the Society Islands hotspot track. Geology 41, 19–22 (2013)

    Article  ADS  Google Scholar 

  8. 8

    Rohde, J. et al. 70 Ma chemical zonation of the Tristan-Gough hotspot track. Geology 41, 335–338 (2013)

    CAS  Article  ADS  Google Scholar 

  9. 9

    Harpp, K. S., Hall, P. S. & Jackson, M. G. in The Galápagos: A National Laboratory for the Earth Sciences (eds Mittelstaedt, E., Graham, D., d’Ozouville, N. & Harpp, K. ) 27–40 (AGU, in the press).

  10. 10

    Chauvel, C. et al. The size of plume heterogeneities constrained by Marquesas isotopic stripes. Geochem. Geophys. Geosyst. 13, Q07005 (2012)

    Article  ADS  CAS  Google Scholar 

  11. 11

    Stracke, A., Hofmann, A. W. & Hart, S. R. FOZO, HIMU and the rest of the mantle zoo. Geochem. Geophys. Geosyst. 6 http://dx.doi.org/10.1029/2004GC000824 (2004)

  12. 12

    Kurz, M. D., Jenkins, W. J. & Hart, S. R. Helium isotopic systematics of oceanic islands and mantle heterogeneity. Nature 297, 43–47 (1982)

    CAS  Article  ADS  Google Scholar 

  13. 13

    Hart, S. R., Hauri, E. H., Oschmann, L. A. & Whitehead, J. A. Mantle plumes and entrainment: isotopic evidence. Science 256, 517–520 (1992)

    CAS  Article  ADS  PubMed  Google Scholar 

  14. 14

    Farley, K. A., Natland, J. H. & Craig, H. Binary mixing of enriched and undegassed (primitive?) mantle components (He, Sr, Nd, Pb) in Samoan lavas. Earth Planet. Sci. Lett. 111, 183–199 (1992)

    CAS  Article  ADS  Google Scholar 

  15. 15

    Hanan, B. B. & Graham, D. W. Lead and helium isotope evidence from oceanic basalts for a common deep source of mantle plumes. Science 272, 991–995 (1996)

    CAS  Article  ADS  PubMed  Google Scholar 

  16. 16

    Tatsumoto, M. Isotopic composition of lead in oceanic basalt and its implication to mantle evolution. Earth Planet. Sci. Lett. 38, 63–87 (1978)

    CAS  Article  ADS  Google Scholar 

  17. 17

    Workman, R. K. et al. Recycled metasomatized lithosphere as the origin of the Enriched Mantle II (EM2) endmember: evidence from the Samoan volcanic chain. Geochem. Geophys. Geosyst. 5, http://dx.doi.org/10.1029/2003GC000623 (2004)

  18. 18

    Koppers, A. A. P. et al. Samoa reinstated as a primary hotspot trail. Geology 36, 435–438 (2008)

    CAS  Article  ADS  Google Scholar 

  19. 19

    Jackson, M. G. et al. The return of subducted continental crust in Samoan lavas. Nature 448, 684–687 (2007b)

    CAS  Article  ADS  PubMed  Google Scholar 

  20. 20

    Jackson, M. G., Kurz, M. D., Hart, S. R. & Workman, R. K. New Samoan lavas from Ofu Island reveal a hemispherically heterogeneous high 3He/4He mantle. Earth Planet. Sci. Lett. 264, 360–374 (2007a)

    CAS  Article  ADS  Google Scholar 

  21. 21

    Konter, J. G. & Jackson, M. G. Large volumes of rejuvenated volcanism in Samoa: Evidence supporting a tectonic influence on late-stage volcanism. Geochem. Geophys. Geosyst. 13, (2012)

  22. 22

    Farnetani, C. G., Hofmann, A. W. & Class, C. How double volcanic chains sample geochemical anomalies from the lowermost mantle. Earth Planet. Sci. Lett. 359/360, 240–247 (2012)

    Article  ADS  CAS  Google Scholar 

  23. 23

    Harpp, K. S. et al. in The Galápagos: A National Laboratory for the Earth Sciences (eds Mittelstaedt, E., Graham, D., d’Ozouville, N. & Harpp, K. ) (AGU, in the press).

  24. 24

    Bryce, J. G., DePaolo, D. J. & Lassiter, J. C. Geochemical structure of the Hawaiian plume: Sr, Nd, and Os isotopes in the 2.8 km HSDP-2 section of Mauna Kea volcano. Geochem. Geophys. Geosyst. 6, Q09G18 (2005)

    Article  CAS  Google Scholar 

  25. 25

    Coltice, N., Moreira, M., Hernlund, J. & Labrosse, S. Crystallization of a basal magma ocean recorded by helium and neon. Earth Planet. Sci. Lett. 308, 193–199 (2011)

    CAS  Article  ADS  Google Scholar 

  26. 26

    Mukhopadhyay, S. Early differentiation and volatile accretion recorded in deep-mantle neon and xenon. Nature 486, 101–104 (2012)

    CAS  Article  ADS  PubMed  Google Scholar 

  27. 27

    Li, M., McNamara, A. K. & Garnero, E. J. Chemical complexity of hotspots caused by cycling oceanic crust through mantle reservoirs. Nature Geosci. http://dx.doi.org/10.1038/ngeo2120 (2014)

  28. 28

    Natland, J. H. The progression of volcanism in the Samoan linear volcanic chain. Am. J. Sci. 280A, 709–735 (1980)

    Google Scholar 

  29. 29

    Hart, S. R. et al. Genesis of the Western Samoa (WESAM) seamount province: age, geochemical fingerprint and tectonics. Earth Planet. Sci. Lett. 227, 37–56 (2004)

    CAS  Article  ADS  Google Scholar 

  30. 30

    Eisele, J., Abouchami, W., Galer, S. J. G. & Hofmann, A. W. The 320 kyr Pb isotope evolution of Mauna Kea lavas recorded in the HSDP-2 drill core. Geochem. Geophys. Geosyst. 4 http://dx.doi.org/10.1029/2002GC000339 (2003)

  31. 31

    Carlson, R. W., Czamanske, G., Fedorenko, V. & Ilupin, I. A comparison of Siberian meimechites and kimberlites: implications for the source of high-Mg alkalic magmas and flood basalts. Geochem. Geophys. Geosyst. 7, Q11014 (2006)

    Article  ADS  CAS  Google Scholar 

  32. 32

    Galer, S. J. H. Chemical and Isotopic Studies of Crust–Mantle Differentiation and the Generation of Mantle Heterogeneity. PhD thesis, Univ. Cambridge. (1986)

  33. 33

    Abouchami, W., Galer, S. J. G. & Koschinsky, A. Pb and Nd isotopes in NE Atlantic Fe–Mn crusts: proxies for trace metal paleosources and paleocean circulation. Geochim. Cosmochim. Acta 63, 1489–1505 (1999)

    CAS  Article  ADS  Google Scholar 

  34. 34

    Petrone, C. M., Francalanci, L., Carlson, R. W., Ferrari, L. & Conticelli, S. Unusual coexistence of subduction-related and intraplate-type magmatism: Sr, Nd and Pb isotope and trace element data from the magmatism of the San Pedro-Ceboruco graben (Nayarit, Mexico). Chem. Geol. 193, 1–24 (2003)

    CAS  Article  ADS  Google Scholar 

  35. 35

    Todt, W. Cliff, R. A., Hanser, A. & Hofmann, A.W. in Earth Processes: Reading the Isotopic Code (eds Basu, A. & Hart, S. R. ) Geophys. Monogr. 95, 429–437 (1996)

    Google Scholar 

  36. 36

    Hart, S. R. et al. The Pb isotope pedigree of Western Samoan volcanics: new insights from high-precision analysis by NEPTUNE ICP/MS. Eos 83, F20 (2002)

    Google Scholar 

  37. 37

    Kurz, M. D., Curtice, J., Lott, D. E., III & Solow, A. Rapid helium isotopic variability in Mauna Kea shield lavas from the Hawaiian Scientific Drilling Project. Geochem. Geophys. Geosyst. 5, Q04G14 (2004)

    Article  CAS  Google Scholar 

  38. 38

    Jackson, M. G. et al. The Samoan hotspot track on a “hotspot highway”: Implications for mantle plumes and a deep Samoan mantle source. Geochem. Geophys. Geosyst. 11 http://dx.doi.org/10.1029/2010GC003232 (2010)

  39. 39

    Koppers, A. A. P. et al. Age systematics of two young en echelon Samoan volcanic trails. Geochem. Geophys. Geosyst. 12, Q07025 (2011)

    ADS  Google Scholar 

  40. 40

    Natland, J. H. & Turner, D. L. in Geological Investigations of the Northern Melanesian Borderland (ed. Brocker, T. M. ) Earth Science Series Vol. 3 139–172 (Circum-Pacific Council for Energy and Mineral Resources, 1985)

    Google Scholar 

  41. 41

    Mcdougall, I. Age and evolution of the volcanos of Tutuila, American Samoa. Pac. Sci. 39, 311–320 (1985)

    CAS  Google Scholar 

  42. 42

    Stolper, E. M. & DePaolo, D. M. Introduction to special section: Hawaii Scientific Drilling Project. J. Geophys. Res. 101, 11593–11598 (1996)

    Article  ADS  Google Scholar 

  43. 43

    Kear, D. & Wood, B. L. The Geology and Hydrology of Western Samoa New Zealand Geological Survey Bulletin 63. (1959)

  44. 44

    Palacz, Z. A. & Saunders, A. D. Coupled trace element and isotope enrichment in the Cook-Austral-Samoa islands, southwest Pacific. Earth Planet. Sci. Lett. 79, 270–280 (1986)

    CAS  Article  ADS  Google Scholar 

  45. 45

    McDonough, W. & Chauvel, C. Sample contamination explains the Pb isotopic composition of some Rurutu island and Sasha seamount basalts. Earth Planet. Sci. Lett. 105, 397–404 (1991)

    CAS  Article  ADS  Google Scholar 

  46. 46

    Hawkins, J. W. & Natland, J. H. Nephelinites and basanites of the Samoan linear volcanic chain: their possible tectonic significance. Earth Planet. Sci. Lett. 24, 427–439 (1975)

    CAS  Article  ADS  Google Scholar 

  47. 47

    White, W. M. & Hofmann, A. W. Sr and Nd isotope geochemistry of oceanic basalts and mantle evolution. Nature 296, 821–825 (1982)

    CAS  Article  ADS  Google Scholar 

  48. 48

    Wright, E. & White, W. M. The origin of Samoa: new evidence from Sr, Nd, and Pb isotopes. Earth Planet. Sci. Lett. 81, 151–162 (1986)

    Article  ADS  Google Scholar 

  49. 49

    Workman, R. K., Eiler, J. M., Hart, S. R. & Jackson, M. G. Oxygen isotopes in Samoan lavas: confirmation of continent recycling. Geology 36, 551–554 (2008)

    CAS  Article  ADS  Google Scholar 

  50. 50

    Hanyu, T. et al. Geochemical characteristics and origin of the HIMU reservoir: a possible mantle plume source in the lower mantle. Geochem. Geophys. Geosyst. 12, Q0AC09 (2011)

    Article  CAS  Google Scholar 

  51. 51

    Hauri, E. H. & Hart, S. R. Re-Os isotope systematics of HIMU and EMII oceanic island basalts from the south Pacific ocean. Earth Planet. Sci. Lett. 114, 353–371 (1993)

    CAS  Article  ADS  Google Scholar 

  52. 52

    Hauri, E. H. & Hart, S. R. Rhenium abundances and systematics in oceanic basalts. Chem. Geol. 139, 185–205 (1997)

    CAS  Article  ADS  Google Scholar 

  53. 53

    Hofmann, A. W. & White, W. M. Mantle plumes from ancient oceanic crust. Earth Planet. Sci. Lett. 57, 421–436 (1982)

    CAS  Article  ADS  Google Scholar 

  54. 54

    Cabral, R. A. et al. Anomalous sulphur isotopes in plume lavas reveal deep mantle storage of Archaean crust. Nature 496, 490–493 (2013)

    CAS  Article  ADS  PubMed  PubMed Central  Google Scholar 

  55. 55

    Gale, A., Dalton, C. A., Langmuir, C. H., Su, Y. & Schilling, J.-G. The mean composition of ocean ridge basalts. Geochem. Geophys. Geosyst. 14, 489–518 (2013)

    CAS  Article  ADS  Google Scholar 

  56. 56

    Graham, D. W. et al. Helium isotope geochemistry of mid-ocean ridge basalts from the South Atlantic. Earth Planet. Sci. Lett. 110, 133–147 (1992)

    CAS  Article  ADS  Google Scholar 

  57. 57

    Parai, R., Mukhopadhyay, S. & Lassiter, J. C. New constraints on the HIMU mantle from neon and helium isotopic compositions of basalts from the Cook–Austral Islands. Earth Planet. Sci. Lett. 277, 253–261 (2009)

    CAS  Article  ADS  Google Scholar 

  58. 58

    Hanyu, T. & Kaneoka, I. The uniform and low 3He/4He ratios of HIMU basalts as evidence for their origin as recycled materials. Nature 390, 273–276 (1997)

    CAS  Article  ADS  Google Scholar 

  59. 59

    Honda, M. & Woodhead, J. D. A primordial solar-neon enriched component in the source of EM-I-type ocean island basalts from the Pitcairn Seamounts, Polynesia. Earth Planet. Sci. Lett. 236, 597–612 (2005)

    CAS  Article  ADS  Google Scholar 

  60. 60

    Jackson, M. G. et al. Globally elevated titanium, tantalum, and niobium (TITAN) in ocean island basalts with high 3He/4He. Geochem. Geophys. Geosyst. 9 http://dx.doi.org/10.1029/2007GC001876 (2008)

  61. 61

    Hart, S. R. & Jackson, M. Ta’u and Ofu/Olosega volcanoes: the ‘‘Twin Sisters’’ of Samoa, their P, T, X melting regime, and global implications. Geochem. Geophys. Geosyst http://dx.doi.org/10.1002/2013GC005221 (2014)

  62. 62

    Farley, K. A. Rapid cycling of subducted sediments into the Samoan mantle plume. Geology 23, 531–534 (1995)

    CAS  Article  ADS  Google Scholar 

  63. 63

    Class, C. & Goldstein, S. L. Evolution of helium isotopes in the Earth’s mantle. Nature 436, 1107–1112 (2005)

    CAS  Article  ADS  PubMed  Google Scholar 

  64. 64

    Hart, S. R. A large-scale isotope anomaly in the Southern Hemisphere mantle. Nature 309, 753–757 (1984)

    CAS  Article  ADS  Google Scholar 

  65. 65

    Sims, K. W. W. et al. 238U-230Th-226Ra-210Po, 232Th-228Ra, and 235U-231Pa constraints on the ages and petrogenesis of Vailulu’u and Malumalu lavas, Samoa. Geochem. Geophys. Geosyst. 9, Q04003 (2008)

    Article  ADS  CAS  Google Scholar 

  66. 66

    Hart, S. R. et al. Vailulu’u undersea volcano: the new Samoa. Geochem. Geophys. Geosyst. 1 http://dx.doi.org/10.1029/2000GC000108 (2000)

  67. 67

    Anderson, T. The volcano of Matavanu in Savaii. Q. J. Geol. Soc. Lond. 66, 621–639 (1910)

    Article  Google Scholar 

  68. 68

    Matsuda, J. I., Notsu, K., Okano, J., Yaskawa, K. & Chungue, L. Geochemical implications from Sr isotopes and K-Ar age determinations for the Cook-Austral Islands chain. Tectonophysics 104, 145–154 (1984)

    CAS  Article  ADS  Google Scholar 

  69. 69

    McDougall, I. Age of volcanism and its migration in the Samoa Islands. Geol. Mag. 147, 705–717 (2010)

    CAS  Article  ADS  Google Scholar 

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Acknowledgements

We thank J. Natland, P. Hall and M. Regelous for discussions, and R. Carlson for access to analytical facilities. Comments from B. Hanan and K. Harpp improved the manuscript. M.G.J. acknowledges grants from the NSF that funded this research: OCE-1061134, OCE-1153894, EAR-1348082 and EAR-1145202.

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Contributions

M.G.J. conceived of the project, performed most of the Sr, Nd and Pb isotopic analyses, and wrote the paper. S.R.H. provided analytical access and insights into the nature of the Samoan mantle. J.G.K. performed statistical modelling, improved figures, and added discussion about the volcanic stages during the evolution of a Samoan volcano. M.D.K. performed helium isotopic measurements, K.A.F. performed helium isotopic measurements and some Sr and Nd isotopic measurements, and J.B. helped with sample preparation and made several Sr and Pb isotopic measurements. All authors contributed intellectually to the manuscript.

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Correspondence to M. G. Jackson.

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Extended data figures and tables

Extended Data Figure 1 Sample locations and volcano ages.

The range of ages for each location (subaerial or submarine dredge) is provided in a box at the periphery of the map, and a yellow line connects each location with the respective age data; not all samples with geochemical data have age data (indeed, most Samoan samples with geochemical data, submarine and subaerial, do not have age constraints). Dredge locations are labelled with a red line: dredges from the 1999 AVON2/3 cruise aboard the RV Melville17 have dredge numbers less than 100, and dredges from the 2005 ALIA cruise aboard the RV Kilo Moana18,19,39 have dredge numbers greater than 100. Samples collected on land were taken from the five Samoan islands (and are labelled with yellow stars: Savai’i subaerial, Upolu subaerial, Tutuila subaerial, Ta’u subaerial and Ofu subaerial). Malumalu and Vailulu’u seamount ages are based on uranium-series disequilibrium, and therefore maximum ages are provided65,66. Upolu subaerial lavas include both rejuvenated series (which bracket the younger limit of ages) and the shield series (which bracket the older limit of ages); poor outcrop exposure on the highly vegetated Samoan islands can make designation of the volcanic stages difficult (particularly if geochemical data are not available for the hand sample), and an average age for the rejuvenated or shield stages on Upolu is therefore not provided. Rejuvenated lavas are present on Tutuila, but ages are not available in the literature. All reported subaerial lavas from Savai’i are rejuvenated, indicating that the island has been covered with a veneer of rejuvenated volcanism21,28. Rejuvenated volcanism has been observed during historical times on Savai’i, which was last active from 1905–1911 (ref. 67); error bars are not provided for the oldest Savai’i subaerial sample in ref. 17. Submarine samples dredged off the coast of Savai’i (D114, D115 and D128) and from Tisa seamount were dredged distal to the Upo lineament and may not belong to this lineament. All available ages for Samoan islands and seamounts are provided in refs 17, 18, 39, 40, 41, 65, 66, 68 and 69. (Ma, million years.)

Extended Data Figure 2 A three-dimensional presentation of the Pb-isotopic groups shows that they converge on the high 3He/4He common component region.

99% confidence intervals (appearing as ‘tubes’) around the best-fit lines through each of the four data groups—Malu lineament (pink tube), Vai lineament (dark blue), subaerial Upo lineament (yellow) and rejuvenated lavas (light blue)—are shown in three-dimensional Pb-isotopic space. The composition of the common component region is modelled as an ellipsoid (grey) that is defined by the 2σ variance around the average in the Pb-isotopic compositions for samples with 3He/4He >20 Ra. In three-dimensional Pb-isotopic space, the 99% confidence intervals around each of the best-fit trend lines overlap with the ellipsoid that encompasses the common component region. Each tube represents an estimate of the error around the best-fit trend to the data defining each geographic lineament. The tube therefore encloses the set of all possible mixing arrays associated with a given geographic lineament. Since all the tubes intersect the ellipsoid of the common component region, statistically a range of mixing arrays exists for each geographic lineament that passes through the common component region. This result is consistent with the compositional data of the four lineaments mixing with the high-3He/4He common component.

Extended Data Figure 3 The isotopic composition of the four Samoan data groups are shown in Nd and Pb isotopic spaces.

In both panels, the high-3He/4He common component region is modelled by a grey ellipse that defines the 2σ variance around the average of the heavy radiogenic isotopic compositions of Samoan lavas with 3He/4He > 20 Ra. The left panel shows the four data groups identified in Pb-isotopic space (Fig. 2) in a plot of 143Nd/144Nd versus 206Pb/204Pb. Samples for which Pb-isotopic ratios were measured by high-precision techniques (Pb-spiked samples run by TIMS and samples run using Tl-addition by MC-ICP-MS) are shown as large symbols (where estimated 2σ external uncertainties are smaller than the symbols17,19,20,21,29,38), and unspiked Pb-isotopic TIMS data are shown as small symbols (where estimated 2σ external uncertainties are equal to or better than ±0.076 for the 208Pb/204Pb ratio, as shown14,17,48,51). The right panel shows the four data groups identified in Fig. 2 in a plot of 206Pb/204Pb versus 207Pb/204Pb. Samples for which Pb-isotopic ratios were measured by high-precision techniques (Pb-spiked samples run by TIMS and samples run using Tl-addition by MC-ICP-MS) are shown as large symbols (where estimated 2σ external uncertainties are smaller than the symbols, except for samples run on the P54 at Carnegie, where estimated 2σ external precision error bars are shown on the individual data points, as reported in the Methods); unspiked Pb-isotopic TIMS data are shown as small symbols (where estimated 2σ external uncertainties are equal to or better than ±0.019 and ±0.023 for 206Pb/204Pb and 207Pb/204Pb, respectively, as shown). 99% confidence intervals around the best-fit lines through each data group overlap with the high-3He/4He common component region. Symbols are the same as in Fig. 2 of the main text. The MORB average composition is from ref. 55. The HSDP-2 drill core data are from refs 24 and 30. See Supplementary Table 4 for a compilation of the Samoan data shown; Alexa data are from ref. 29.

Extended Data Figure 4 Various geochemical signatures show clear trends with increasing distance from the common component region in Pb-isotopic space.

The top panel shows a plot of versus Ti/Ti*. Samoan lavas with the highest 3He/4He have the highest Ti/Ti* and the lowest values; this follows from an earlier observation that Ti/Ti* correlates with 3He/4He in Samoan lavas, and the high-3He/4He mantle reservoir has elevated Ti/Ti* (ref. 60). Ti/Ti* is defined in ref. 19. Only lavas with MgO > 7 wt% are shown, to avoid the effects of fractional crystallization of trace phases that might fractionate the trace element ratios. A sample with high MnO from Soso (ALIA110-39) is excluded owing to a high degree of alteration. ALIA-115-07, which is highly altered, is also excluded, as are all samples from ALIA Dredge 118. Samples with He concentrations <10−9 cm3 of 4He at STP per gram of sample (olivine) are excluded. Additionally, only shield-stage lavas are plotted. The middle panel shows versus 143Nd/144Nd. 143Nd/144Nd shows systematic behaviour in each data group moving away from the common component region (that is, with increasing ) in Pb-isotope space. Data from subaerial Upo-lineament lavas (yellow) exhibit increasing 143Nd/144Nd with increasing distance (higher ) from the common component region, and this supports the hypothesis that the subaerial portion of the Upo lineament samples a depleted mantle (DM) component similar to that found in the Alexa seamount and Hawaii. The other data groups (from the rejuvenated lavas and the Vai and Malu volcanic lineaments) all exhibit lower (more enriched) 143Nd/144Nd with increasing distance from the common component region. Finally, the middle panel shows that 143Nd/144Nd exhibits the least amount of variability in the common component region—where is zero—as the four isotopic groups converge on a common component with relatively homogeneous isotopic characteristics. The bottom panel shows versus 3He/4He (also shown in Fig. 2 of the main text) for comparison with the other panels. Symbols are the same as in Fig. 2. The MORB average composition is from ref. 55. The HSDP-2 drill core data are from refs 24 and 30. When calculating Ti/Ti*, only data obtained by ICP-MS (except Ti, which is measured by X-ray fluorescence) are used. See Supplementary Table 4 for sources of the Samoan data; Alexa data are from ref. 29.

Extended Data Figure 5 (U+Th)/Pb versus Ba/Th.

Vai-lineament lavas exhibit the highest (U+Th)/Pb values in Samoa, consistent with a HIMU signature. Such high (U+Th)/Pb values are consistent with the radiogenic Pb-isotopic compositions in Vai-lineament lavas and similar to the high (U+Th)/Pb values observed in HIMU lavas. Samoan rejuvenated lavas, which have an EM1 signature, have high Ba/Th (and Ba/Sm and Ba/Nb); this Ba-enrichment matches the positive Ba-anomalies observed in EM1 endmember lavas from Pitcairn29. Highly altered samples and samples with low MgO are excluded (as described in Extended Data Fig. 4). Ref. 17 identified Upolu sample U10 as an outlier in many isotope and trace element spaces. Symbols are the same as in Fig. 2 of the main text. Only data obtained by ICP-MS are shown. See Supplementary Table 4 for a compilation of the Samoan data shown.

Extended Data Figure 6 The 3He/4He ratios of Samoan lavas are shown in colour (warmer colours represent higher 3He/4He) to show the distribution of 3He/4He ratios in 208Pb/204Pb versus 206Pb/204Pb isotopic space.

Lavas with the highest 3He/4He tend to cluster near the region in Pb-isotopic space where the four Pb-isotopic data groups converge, and lavas with lower 3He/4He tend to plot farthest from the common component region. Samples with <10−9 cm3 of 4He at STP per gram of sample (olivine) are excluded. See Supplementary Table 4 for a compilation of the Samoan data shown.

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Jackson, M., Hart, S., Konter, J. et al. Helium and lead isotopes reveal the geochemical geometry of the Samoan plume. Nature 514, 355–358 (2014). https://doi.org/10.1038/nature13794

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