Geochemistry of diamondiferous eclogites from Udachnaya Pipe, Siberia

Ekaterina V. Rubanova, William L. Griffin, Zdislav V. Spetsius, Suzanne Y. O'Reilly, Norman J. Pearson, Richard Stern, Thomas Stachel, John Cliff

    Research output: Contribution to conferenceAbstract


    Three types of garnet (Gnt) can be recognised in eclogites from the Udachnaya kimberlite pipe, with different major-, trace-element and O-isotope compositions and related to different stages of mantle metasomatism. Gnt1 and Gnt2 are usually found together with diamonds in metasomatic veins. Gnt2 forms Mg-rich rims on Gnt 1 (mg.67-0.80 vs 0.57-0.58 for Gnt1). The significant zoning in chemistry and its relationship to diamond with mantle-like carbon (13 C = -5.6 - -6.6) suggest that Gnt2 was produced by mantle fluids/melts shortly before eruption. Gnt2 has a wide range in oxygen isotope composition (18 O = 6.2-9.0), suggesting mixing of mantle fluids with the original isotopic system (Gnt1, 18 O =11.1-12.0). Gnt3 is found in corundum-bearing eclogites and has much higher Ca (CaO=15.61-16.56 wt%) and different isotopic characteristics (13 C = -3.6 - -5.3; 18 O = 3.2-5.7). This suggests a different metasomatic fluid from the one that produced Gnt2. Lu/Gd increases significantly from Gnt3 (0.06-0.12) to Gnt1 (4.0-4.2) to Gnt2 (5.5-9.0). The major- and TE compositions of garnets from 25 eclogites show a well-defined change from positive to negative HREE/LREE at a CaO content of 7.8-8.7%. This suggests either a change in fluid compositions or a change in Gnt/fluid partitioning related to garnet composition.
    Original languageEnglish
    Number of pages1
    Publication statusPublished - 2012
    EventInternational Geological Congress (34th : 2012) - Brisbane, Australia
    Duration: 5 Aug 201210 Aug 2012


    ConferenceInternational Geological Congress (34th : 2012)


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