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

Weiss, Yaakov; McNeill, John; Pearson, D. Graham; Nowell, Geoff M.; Ottley, Chris J.

Authors

Yaakov Weiss

John McNeill

D. Graham Pearson

Chris J. Ottley



Abstract

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.

Journal Article Type Article
Acceptance Date Jun 19, 2015
Online Publication Date Aug 19, 2015
Publication Date 2015
Deposit Date Aug 18, 2017
Journal Nature
Print ISSN 0028-0836
Electronic ISSN 1476-4687
Publisher Nature Research
Peer Reviewed Peer Reviewed
Volume 524
Issue 7565
Pages 339-344
DOI https://doi.org/10.1038/nature14857
Public URL https://durham-repository.worktribe.com/output/1349475