Metasomatism of the Upper Mantle and the Genesis of Kimberlites and Alkali Basalts
- F.R. Boyd and
- Henry O.A. Meyer
Published Online: 19 MAR 2013
Copyright © 1979 by the American Geophysical Union.
The Mantle Sample: Inclusion in Kimberlites and Other Volcanics
How to Cite
Boettcher, A. L., O'Neil, J. R., Windom, K. E., Stewart, D. C. and Wilshire, H. G. (1979) Metasomatism of the Upper Mantle and the Genesis of Kimberlites and Alkali Basalts, in The Mantle Sample: Inclusion in Kimberlites and Other Volcanics (eds F.R. Boyd and H. O.A. Meyer), American Geophysical Union, Washington, D.C.. doi: 10.1029/SP016p0173
- Published Online: 19 MAR 2013
- Published Print: 1 JAN 1979
Print ISBN: 9780875902135
Online ISBN: 9781118664858
- Alkali basalts;
- Isotopic analyses;
- Kimberlites genesis;
- Upper mantle metasomatism
Petrological and geochemical evidence reveals that pervasive metasomatism of upper-mantle lherzolite is precursory to or concomitant with anatexis associated with the genesis of alkali basalts and kimberlites. This introduction of fluids rich in Ti, K, Fe, H2O and other elements is well displayed in peridotite and eclogite xenoliths in these rocks, particularly in the development of titaniferous phlogopites and amphiboles. Values of δD of phlogopite lie in the restricted range of −60 to −79‰, which is consonant with other determinations of primordial H2O and implies constant conditions of formation. On the other hand, amphiboles exhibit a large range in D and H2O contents, suggesting a more complex history. Values of δ18O for the phlogopites and amphiboles range from 4.26 to 5.92, also typical of deep-seated materials.
Selective enrichment by aqueous fluids may be, in part, responsible for the chemical heterogeneity of the upper mantle, which is supported by a plethora of other geochemical data. It also provides a ready explanation for the abundance of incompatible elements in kimberlites and alkali basalts as well as a mechanism for localized magma generation within the mantle.