Deep mantle origin of kimberlite magmas revealed by neon isotopes

[1] We measured noble gases in olivines extracted from alteration-free samples of the Udachnaya-East kimberlite pipe, eastern Siberia. Neon isotope ratios indicate that the kimberlite has a less nucleogenic Ne signature than a typical mid-ocean ridge basalt (MORB) source, which is consistent with the less radiogenic Ar-40/Ar-36 ratio compared to MORB and subcontinental lithospheric mantle (SCLM) sources. Based on He-Ne systematics, the He-3/He-4 ratio of the plume source of the Udachnaya kimberlite pipe would be higher than 15 R-A with the dominant He signature of the magma acquired by assimilation of SCLM and/or crustal material during magma ascent. Our results indicate that the source of the Udachnaya kimberlite has similar noble gas characteristics to those of ocean island basalts (OIBs). Its origin is therefore deeper than that of the MORB source mantle, and probably is the same as the OIB-source mantle.