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Hf isotope systematics of kimberlites and their megacrysts: New constraints on their source regions

Nowell, G.M; Pearson, D.G; Bell, D.R; Carlson, R.W; Smith, C.B; Kempton, P.D; Noble, S.R


D.G Pearson

D.R Bell

R.W Carlson

C.B Smith

P.D Kempton

S.R Noble


Kimberlites from Southern Africa, along with their low-Cr megacrysts, have unusual Hf–Nd isotopic characteristics. Group I and Transitional kimberlites define arrays trending oblique to, and well below, the Nd–Hf isotope ‘mantle array’, defined by oceanic basalts, i.e. they have negative Hf values. Group I kimberlites have Hf values varying from –1.2 to –10.1. Low-Cr megacryst suites from individual Group I kimberlites have compositions that overlap those of their host kimberlites. The trend for all Group I kimberlite megacrysts (Hf values –1.0 to –9.0) shows a striking correspondence to that of the Group I kimberlite field. Group II kimberlites and their low-Cr megacrysts plot on or close to the mantle Nd–Hf array (Hf values 3.6 to –2.6). The data indicate a genetic link between kimberlites and the low-Cr megacryst suite. The negative Hf characteristics of Group I kimberlites and their megacrysts require a source component that is ancient (>1 Ga), and has evolved with low time-integrated Lu/Hf relative to Sm/Nd. Our preferred option is that this component originates beneath the lithosphere, from a reservoir of ancient, deeply subducted oceanic basalt that became incorporated into the convecting mantle source region for Group I and Transitional kimberlites.


Nowell, G., Pearson, D., Bell, D., Carlson, R., Smith, C., Kempton, P., & Noble, S. (2004). Hf isotope systematics of kimberlites and their megacrysts: New constraints on their source regions. Journal of Petrology, 45(8), 1583-1612.

Journal Article Type Article
Publication Date 2004-08
Deposit Date Feb 20, 2007
Journal Journal of Petrology
Print ISSN 0022-3530
Electronic ISSN 1460-2415
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 45
Issue 8
Pages 1583-1612
Keywords isotopes; kimberlites; lutetium–hafnium; megacrysts.
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