Abstract
Deep-seated xenoliths hosted in kimberlite pipes (Udachnaya, Leningradskaya, Yubileynaya, Komsomolskaya, Botuobinskaya, Zapolyarnaya) from the Siberian craton include mafic and felsic garnet granulite, two-pyroxene granulites, gneisses, and amphibolite. Calculated equilibration temperatures range from 600 to 850 degrees C at pressures from 8 to 1.4 GPa. Garnet granulites give the highest temperatures (710-850 degrees C) and pressures (9-14 GPa) and amphibolites the lowest; felsic granulites fall between these two groups. The mafic xenoliths are picrobasaltic to basaltic in bulk chemical composition. The chondrite-normalised REE patterns for the mafic granulite xenoliths vary from flat to LREE-enriched (La (sub N) /Yb (sub N) =8.6-18.8); some have slight positive Eu-anomalies. Garnet granulite xenoliths with low REE contents and positive Eu-anomalies are interpreted as cumulates. The bulk compositions of felsic granulites and gneisses vary from andesite to rhyodacite. Zircon LAM-ICPMS dating shows several episodes in the formation of the deep crust of Siberian craton. Zircons from mafic granulites are metamorphic and have concordant ages from 1.78 to 1.97 Ga. Most zircon grains from felsic granulites show oscillatory zoning in BSE images; some show core-rim structure, in which the cores have oscillatory zoning. The age of 2.95 Ga obtained from zircon in felsic xenoliths of the Botuobonskay pipe is the oldest age recorded in the xenolith suite. Magmatic zircons from the Zapollyarnay pipe yielded NeoArchean ages of 2.71 Ga.
| Original language | English |
|---|---|
| Pages (from-to) | 1850 |
| Number of pages | 1 |
| Journal | Mineralogical Magazine |
| Volume | 75 |
| Issue number | 3 |
| Publication status | Published - 2011 |
| Event | Goldschmidt Conference (21st : 2011) - Prague, Czech Republic Duration: 14 Aug 2011 → 19 Aug 2011 |