U/Pb dating of zircons from the lower crustal xenoliths from Siberian kimberlites

Zircons from seven lower crustal xenoliths from Siberian
kinberlites have been dated in situ by U/Pb LAM-ICP-MS at
the GEMOC National Key Centre, Macquarie University,
Australia. The suite of studied samples comprises two
granulites from the Udachnaya pipe and one granulite from the
Leningradskaya pipe, (Daldyn kimberlite field), one granulite
from the Yubileinaya pipe and three shists from the
Komsomol’skaya pipe, (Alakit field).
Thirty eight zircon grains were extracted and analyzed
from the granulite xenolith Ud-01-44 (Udachnaya). Most of
the zircons give 207Pb/206Pb ages of 1.89 Ga and two grains
give 2.5 Ga. Only four zircons have been found in the
granulite xenolith Ud-01-66 (Udachnaya). They give a
207Pb/206Pb age of 1.79 Ga. Twenty zircon grains from
granulite xenolith L-02-9 from the Leningradskaya pipe give a
207Pb/206Pb age of 1.9 Ga.
Six zircon grains from the granulite xenolith Yb-02-27
(Yubileinaya pipe) give a 207Pb/206Pb age of 1.86 Ga. Twelve
zircon grains from the shist xenolith K-3-02
(Komsomol’skaya) give a 207Pb/206Pb age of 1.89 Ga.
Seventeen zircon grains from the shist xenolith K-69-02
(Komsomol’skaya) give a 207Pb/206Pb age of 1.9 Ga. Three
other grains give 2.9, 2.4, and 2.3 Ga. Nineteen zircon grains
from the shist xenolith K-45-02 from the Komsomol’skaya
pipe give a 207Pb/206Pb age of 1.84 Ga. Two grains give 2.3 Ga
and one grain give 2.46 Ga.
Xenoliths of granulites and shists from the Paleozoic
kimberlites provide the timing of major periods of lower crust
formation in the Siberian craton in Archean and Proterozoic
time. The Paleoproterozoic ages around 1.8-1.9 Ga correspond
to a period of crustal reworking, and the collision between
separate blocks of the craton, during the final assembly of the
Siberian craton [1,2].

[1] Rosen et al. (1994) In: Condie, K.C. (ed.), Archean Crustal
Evolution, 411-459.
[2] Smelov and Timofeev (2007) Gond.
Research 12, 279-288.