Samarium/neodymium elemental and isotopic systematics in sedimentary rocks

https://doi.org/10.1016/0016-7037(92)90034-GGet rights and content

Abstract

Trace element (Sm, Nd, Th, Sc) and Nd-isotopic data for sedimentary rocks are examined in order to evaluate

  • 1.

    (1) possible secular trends in the composition of the sedimentary mass and upper continental crust

  • 2.

    (2) the role of tectonic setting in controlling the chemical and Nd-isotopic composition of the sedimentary mass. When plotted against either sedimentation age or average provenance age (determined mainly from Nd-model ages), Sm/Nd in sedimentary rocks decreases abruptly from about 0.21 to 0.19 at the Archean-Proterozoic transition, consistent with a change towards a more felsic upper crustal composition. The change is only somewhat less pronounced for turbidite sediments than for those of continental affinity. A trend toward increasing Sm/Nd, approaching or exceeding Archean values, is observed for Phanerozoic turbidites. This latter change is interpreted as indicating undifferentiated young crust as a component in the sediment, which has been lost from the older post-Archean record due to sedimentary and igneous intracrustal recycling processes. When plotted against sedimentation age, Th/Sc ratios exhibit a trend directly comparable to that of Sm/Nd. In this case, Th/Sc increases abruptly at the Archean/Proterozoic boundary from about 0.5 to 1.0 and then decreases to about 0.7 during the Phanerozoic. Nd-isotopic composition of modern sediments is affected by tectonic association with those deposited at active margin settings tending to have higher ϵNd reflecting younger provenance and higher and more scattered Sm/Nd reflecting less homogenized and differentiated provenance. It is likely that these distinctions can be traced back for about 1–2 Ga but, with the current data base, are not readily resolved in older sedimentary rocks. The degree to which the preserved sedimentary mass is open to new additions from the mantle, either through replacement during sedimentary recycling or sediment mass growth, is highly variable but averages about 15–25% during the Phanerozoic.

References (86)

  • P.A. Floyd et al.

    Geochemistry and tectonic setting of Lewisian Clastic metasediments from the Early Proterozoic Loch Maree Group of Gairloch, NW Scotland

    Precambrian Res.

    (1989)
  • C.D. Frost et al.

    Mass balance for Nd in the Mediterranean Sea

    Chem. Geol.

    (1986)
  • D.K. Ghosh et al.

    Nd-Sr isotopic study of Proterozoic to Triassic sediments from southeastern British Columbia

    Earth Planet. Sci. Lett.

    (1989)
  • A.K. Gibbs et al.

    The Archean-Proterozoic transition: Evidence from the geochemistry of metasedimentary rocks of Guyana and Montana

    Geochim. Cosmochim. Acta

    (1986)
  • S.J. Goldstein et al.

    Nd and Sr isotopic systematics of river water suspended material: Implications for crustal evolution

    Earth Planet. Sci. Lett.

    (1988)
  • S.L. Goldstein et al.

    A Sm-Nd isotopic study of atmospheric dusts and particulates from major river systems

    Earth Planet. Sci. Lett.

    (1984)
  • F.E. Grousset et al.

    Neodymium isotopes as tracers in marine sediments and aerosols: North Atlantic

    Earth Planet. Sci. Lett.

    (1988)
  • S.B. Jacobsen

    Isotopic constraints on crustal growth and recycling

    Earth Planet. Sci. Lett.

    (1988)
  • G.A. Jenner et al.

    Geochemistry of the Archean Yellowknife Supergroup

    Geochim. Cosmochim. Acta

    (1981)
  • T.C. Liew et al.

    Genesis of granitoid batholiths of Peninsular Malaysia and implications for models of crustal evolution: Evidence from a Nd-Sr isotopic and U-Pb zircon study

    Geochim. Cosmochim. Acta

    (1985)
  • S.M. McLennan

    On the geochemical evolution of sedimentary rocks

    Chem. Geol.

    (1982)
  • S.M. McLennan et al.

    Geochemistry of Archean shales from the Pilbara Supergroup, Western Australia

    Geochim. Cosmochim. Acta

    (1983)
  • S.M. McLennan et al.

    Geochemical evolution of Archean shales from South Africa. I. The Swaziland and Pongola Supergroups

    Precambrian Res.

    (1983)
  • S.M. McLennan et al.

    Geochemistry of Archean metasedimentary rocks from West Greenland

    Geochim. Cosmochim. Acta

    (1984)
  • S.M. McLennan et al.

    Geochemical and Nd-Sr isotopic composition of deep sea turbidites: Crustal evolution and plate tectonic associations

    Geochim. Cosmochim. Acta

    (1990)
  • E.W. Mearns

    A samarium-neodymium isotopic survey of modern sediments from northern Britain

    Chem. Geol.

    (1988)
  • A. Michard et al.

    Nd isotopes in French Phanerozoic shales: External vs. internal aspects of crustal evolution

    Geochim. Cosmochim. Acta

    (1985)
  • R.G. Miller et al.

    The provenance and crustal residence ages of British sediments in relation to palaeogeographic reconstructions

    Earth Planet. Sci. Lett.

    (1984)
  • R.G. Miller et al.

    Crustal residence ages of clastic sediments, orogeny and continental evolution

    Chem. Geol.

    (1986)
  • W.B. Nance et al.

    Rare earth element patterns and crustal evolution—I. Australian post-Archean sedimentary rocks

    Geochim. Cosmochim. Acta

    (1976)
  • W.B. Nance et al.

    Rare earth element patterns and crustal evolution—II. Archean sedimentary rocks from Kalgoorlie, Australia

    Geochim. Cosmochim. Acta

    (1977)
  • R.K. O'Nions et al.

    A Nd isotope investigation of sediments related to crustal development in the British Isles

    Earth Planet. Sci. Lett.

    (1983)
  • R.L. Rudnick et al.

    Large ion lithophile elements in rocks from high-pressure granulite facies terrains

    Geochim. Cosmochim. Acta

    (1985)
  • E.W. Sawyer

    The influence of source rock type, chemical weathering and sorting on the geochemistry of clastic sediments from the Quetico Metasedimentary Belt, Superior Province, Canada

    Chem. Geol.

    (1986)
  • S.B. Shirey et al.

    Mantle heterogeneity and crustal recycling in Archean granite-greenstone belts: Evidence from Nd isotopes and trace elements in the Rainy Lake area, Superior Province, Ontario, Canada

    Geochim. Cosmochim. Acta

    (1986)
  • S.R. Taylor et al.

    Chemical relationships among irghizites, zhamanshinites, Australian tektites and Henbury impact glasses

    Geochim. Cosmochim. Acta

    (1979)
  • S.R. Taylor et al.

    Geochemistry of loess, continental crustal composition and crustal model ages

    Geochim. Cosmochim. Acta

    (1983)
  • S.R. Taylor et al.

    Rare earth element patterns in Archean high-grade metasediments and their tectonic significance

    Geochim. Cosmochim. Acta

    (1986)
  • J. Veizer

    Secular variations in chemical composition of sediments: A review

    Phys. Chem. Earth

    (1979)
  • J. Veizer

    Continental growth: Comments on “The Archean-Proterozoic transition: Evidence from Guyana and Montana” by A.K. Gibbs, C.W. Montgomery, P.A. O'Day And E.A. Erslev

    Geochim. Cosmochim. Acta

    (1988)
  • J. Veizer et al.

    87Sr/86Sr in Precambrian carbonates as an index of crustal evolution

    Geochim. Cosmochim. Acta

    (1976)
  • W.M. White et al.

    Isotope and trace element geochemistry of sediments from the Barbados Ridge-Demerara Plain region, Atlantic Ocean

    Geochim. Cosmochim. Acta

    (1985)
  • D.J. Wronkiewicz et al.

    Geochemistry of Archean shales from the Witwatersrand Supergroup, South Africa: Source-area weathering and provenance

    Geochim. Cosmochim. Acta

    (1987)
  • Cited by (148)

    View all citing articles on Scopus

    Presented at the symposium for S. R. Taylor, “Origin and Evolution of Planetary Crusts,” held October 1–2, 1990, at the Research School of Earth Sciences, ANU.

    View full text