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Sr, Nd, and Pb isotope evidence for a mantle origin of alkali chlorides and carbonates in the Udachnaya kimberlite, Siberia

Citation

Maas, R and Kamenetsky, M and Sobolev, AV and Kamenetsky, VS and Sobolev, NV, Sr, Nd, and Pb isotope evidence for a mantle origin of alkali chlorides and carbonates in the Udachnaya kimberlite, Siberia, Geology, 33, (7) pp. 549-552. ISSN 0091-7613 (2005) [Refereed Article]

DOI: doi:10.1130/G21257.1

Abstract

The kimberlite rocks of the Udachnaya-East pipe (Siberia) are uniquely fresh and contain very high abundances of primary volatiles (Cl, CO2, S). Alkali elements and chlorine are extremely abundant in the reconstructed kimberlite melt compositions, and this enrichment is very important for our understanding of deep-mantle melting and melt transport. Here we present new isotopic data that confirm a mantle origin for these kimberlitic chlorides and carbonates, and constrain the kimberlite emplacement age as ca. 347 Ma. The initial Nd and Pb isotope ratios in a large salt aggregate, in a Cl-S-enriched water leachate of the groundmass, and in the silicate fraction of the groundmass are very similar (εNd = +3 to + 4, 206Pb/204Pb = 18.6, 207Pb/204Pb = 15.53), implying a comagmatic origin of the chlorides and carbonates and the silicates. Combined Sr, Nd, and Pb isotope data are used to rule out any significant contributions to the kimberlite chlorine budget from crustal sources, such as the Cambrian evaporite sequences of the Siberian platform. Our data support the interpretation that exsolved Na-K chloride and Na-K-Ca carbonate formed directly from original uncontaminated kimberlite magma. High Cl abundances in kimberlites suggest the presence of a Cl-rich reservoir in the deep sublithospheric mantle. © 2005 Geological Society of America.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Geology
Research Field:Igneous and Metamorphic Petrology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Kamenetsky, M (Dr Maya Kamenetsky)
Author:Kamenetsky, VS (Professor Vadim Kamenetsky)
ID Code:39071
Year Published:2005
Web of Science® Times Cited:124
Deposited By:Centre for Ore Deposit Research - CODES CoE
Deposited On:2005-08-01
Last Modified:2007-10-19
Downloads:0

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