Letter | Published:

Highly saline fluids from a subducting slab as the source for fluid-rich diamonds

Nature volume 524, pages 339342 (20 August 2015) | Download Citation


The infiltration of fluids into continental lithospheric mantle is a key mechanism for controlling abrupt changes in the chemical and physical properties of the lithospheric root1,2, as well as diamond formation3, yet the origin and composition of the fluids involved are still poorly constrained. Such fluids are trapped within diamonds when they form4,5,6,7 and so diamonds provide a unique means of directly characterizing the fluids that percolate through the deep continental lithospheric mantle. Here we show a clear chemical evolutionary trend, identifying saline fluids as parental to silicic and carbonatitic deep mantle melts, in diamonds from the Northwest Territories, Canada. Fluid–rock interaction along with in situ melting cause compositional transitions, as the saline fluids traverse mixed peridotite–eclogite lithosphere. Moreover, the chemistry of the parental saline fluids—especially their strontium isotopic compositions—and the timing of host diamond formation suggest that a subducting Mesozoic plate under western North America is the source of the fluids. Our results imply a strong association between subduction, mantle metasomatism and fluid-rich diamond formation, emphasizing the importance of subduction-derived fluids in affecting the composition of the deep lithospheric mantle.

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Y.W. acknowledges his Lamont postdoctoral fellowship and National Science Foundation grant no. 1348045. We thank T. Stachel and D. Walker for discussions and J. J. Gurney, J. Carlson, T. Nowicki and BHP Minerals/Dominion Diamonds for access to diamonds from the Ekati mine. J.M. was funded by a scholarship from the Diamond Trading Company at Durham University. D.G.P. completed this work under tenure of a Canada Excellence Research Chair, with support from the Deep Carbon Observatory (Sloan Foundation). Y.W. thanks Israel Science Foundation grant number 435/12 for funding the EPMA and Fourier transform infrared (FTIR) analyses at the Hebrew University. D. E. Jacob, M. Santosh and M. Walter made excellent suggestions that greatly improved this paper. This is Lamont–Doherty Earth Observatory contribution number 7908.

Author information


  1. Lamont-Doherty Earth Observatory, Columbia University, New York, New York 10964, USA

    • Yaakov Weiss
  2. Department of Earth Sciences, Durham University, Durham, DH1 3LE, UK

    • John McNeill
    • , Geoff M. Nowell
    •  & Chris J. Ottley
  3. Department of Earth & Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada

    • D. Graham Pearson


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Y.W. preformed the EPMA and FTIR analyses and conceived and developed the model. Y.W. and D.G.P. wrote the paper. D.G.P., G.M.N. and J.M. jointly developed the in situ closed-cell laser ablation analytical technique used. D.G.P. supervised the trace element and isotopic measurements performed by J.M. C.J.O. aided in sample preparation and measurements. All authors contributed intellectually to the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Yaakov Weiss.

Sample metadata have been archived in the System for Earth Sample Registration (SESAR) with associated International GeoSample Numbers (IGSNs). The data set can be found in the EarthChem library (http://doi.org/10.1594/IEDA/100540).

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    Supplementary Information

    This file contains Supplementary Tables 1-4.

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    Supplementary Data

    This file contains individual microinclusion EPMA analyses, HDFs and Minerals.

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