Formation of cratonic subcontinental lithospheric mantle from hybrid plume sources

S. Aulbach, T. Stachel, Larry M. Heaman, Robert A. Creaser, Steven B. Shirey

Research output: Contribution to journalMeeting abstract

Abstract

Peridotitic sulfide inclusions in diamonds from the central Slave craton constrain the age and origin of their subcontinental lithospheric mantle (SCLM) source. In the Re-Os isochron diagram, sulfides form two ca 3.4 Ga age arrays with variably elevated initial 187Os/188Os indicative of enriched sources. Archean to recent plume-derived melts carry a subducted crust (eclogite) signature [1], and some cratonic mantle lithosphere may have been generated in plumes by extraction of komatiitic liquids [2]. We explain our data by melting in a hybrid mantle plume that contains domains of recycled eclogite [1] and/or (?plume-initiated) subduction of proximal evolved lithospheric material [3].

In upwelling hybrid mantle, eclogite will melt first. Melts will react with olivine in surrounding peridotites to form orthopyroxene (opx), convert peridotite to pyroxenite [1] and confer their crustal isotope signatures. Upon further decompression, pyroxenitic melts [1] pervade the near-solidus mantle, helping local isotopic homogenization and adding aluminous opx. The subsequent partial melting of this opx- (Al- and Si-) enriched source generated komatiites and complementary ultradepleted cratonic mantle residues.

Subduction still is needed to explain many cratonic features. Nonetheless, this model satisfies several key observations: (1) suprachondritic initial 187Os/188Os in subsets of lithospheric mantle samples and in some coeval Archaean komatiites; (2) variable aluminous opx enrichment and (3) high Mg# combined with high opx content in cratonic SCLM [2] due to higher melt productivity of an Al- and Si-richer source [4], in addition to higher Archean temperatures. The model also alleviates a mass balance problem [2, 4] because it predicts a hybrid mantle source with variably higher SiO2 than pyrolite, and contrary to a primitive mantle source is able to reconcile compositions of komatiites and complementary cratonic mantle residues.
Original languageEnglish
Pages (from-to)A37-A37
Number of pages1
JournalGeochimica et Cosmochimica Acta
Volume74
Issue number12, Supplement
DOIs
Publication statusPublished - Jun 2010
Externally publishedYes
EventGoldschmidt Conference (20th : 2010) - Knoxville, United States
Duration: 13 Jun 201018 Jun 2010

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