Small mantle fragments from the renard kimberlites, Quebec

Powerful recorders of mantle lithosphere formation and modification beneath the eastern superior craton

Lucy Hunt*, Thomas Stachel, Herman Grütter, John Armstrong, Tom E. McCandless, Antonio Simonetti, Sebastian Tappe

*Corresponding author for this work

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The origin and evolution of diamondiferous lithospheric mantle sampled by the Neoproterozoic Renard kimberlites (eastern Superior Province, Quebec) is constrained based on mantle-derived microxenoliths and xenocrysts. The dataset illustrates the wealth of knowledge that can be gleaned from small samples (1·;2 mg-2·;2 g) through an integration of multiple, mainly single mineral based approaches. Our samples document the presence of an ∼200 km thick lithosphere with a 'cold' (38 mW m -2 surface heat flow) model geotherm at the time of kimberlite emplacement (c. 632 Ma), resulting in a large diamond window from 130 to 200 km (42-60 kbar). On the basis of the mantle xenolith and xenocryst record and excluding megacrysts, the lithospheric mantle beneath Renard was dominated by peridotite (91%), composed of lherzolite (72% of samples), harzburgite (24%) and wehrlite (5%), with minor eclogitic (3%) and websteritic (6%) portions. Comparatively abundant harzburgite probably establishes the principal diamond source, but elevated Na contents in eclogitic garnet suggest the additional presence of diamond-stable eclogites. A number of events have modified the lithospheric mantle underlying the eastern Superior Province, including the following: (1) evolving 'kimberlitic' melts pervasively re-fertilized the originally strongly depleted lithospheric mantle with respect to highly and moderately incompatible trace elements; (2) less pervasive fluid style metasomatism is indicated by selective re-enrichment of highly incompatible elements that occurred within a depth range of 125-170 km. In situ Pb isotope data obtained for clinopyroxenes suggest a model age of ∼2·;7 Ga for the protolith(s) of the cratonic lithospheric mantle beneath Renard. This age coincides with a major phase of continental crust generation within the Superior Province and throughout the Laurentia supercontinent (e.g. Greenland).

Original languageEnglish
Article numberegs027
Pages (from-to)1597-1635
Number of pages39
JournalJournal of Petrology
Volume53
Issue number8
DOIs
Publication statusPublished - Aug 2012
Externally publishedYes

Keywords

  • Continental lithosphere
  • Cratonic mantle
  • Geochemistry
  • Geothermobarometry
  • Pb isotopes
  • Xenocryst
  • Xenolith

Fingerprint Dive into the research topics of 'Small mantle fragments from the renard kimberlites, Quebec: Powerful recorders of mantle lithosphere formation and modification beneath the eastern superior craton'. Together they form a unique fingerprint.

  • Cite this