Isotopic and geochemical studies of nodules in kimberlite have implications for the lower continental crust

M. T. McCulloch*, R. J. Arculus, B. W. Chappell, J. Ferguson

*Corresponding author for this work

    Research output: Contribution to journalArticle

    35 Citations (Scopus)

    Abstract

    Lower crustal xenoliths from the Calcutteroo kimberlitic pipes in South AUS show a surprisingly diverse range in Nd and Sr isotopic compositions and rare earth element (REE) abundances. Mafic granulite and garnet-clinopyroxenite xenoliths have measured εNd(0) values between +6.1 and -7.9, both light (L)REE enrichments and depletions, low Rb/Sr ratios (0.005-0.040) and relatively high 87Sr/86Sr ratios of from 0.70675 to 0.70919. A felsic xenolith has compositions more typical of upper crustal rocks with εNd(0) = -21.4, LREE enrichments, Rb/Sr = 1.47 and 87Sr/86Sr = 0.85987. An approximate correlation also exists between Sm/Nd versus 143Nd/144Nd and Rb/Sr versus 87Sr/86Sr indicating major intracrustal differentiation in the lower crust at ∼2,400 Myr. This produced extremely low Rb/Sr ratios, and both relative LREE enrichments (low Sm/Nd) and depletions (high Sm/Nd). If these results are typical, then they indicate that the lower crust has higher 87Sr/86Sr and more positive εNd(0) values than previous estimates1-5. This may require revision of total crustal compositions and crust-mantle evolutionary models1-5.

    Original languageEnglish
    Pages (from-to)166-169
    Number of pages4
    JournalNature
    Volume300
    Issue number5888
    DOIs
    Publication statusPublished - 1982

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    McCulloch, M. T., Arculus, R. J., Chappell, B. W., & Ferguson, J. (1982). Isotopic and geochemical studies of nodules in kimberlite have implications for the lower continental crust. Nature, 300(5888), 166-169. https://doi.org/10.1038/300166a0